Option MANUAL RESET, after the intruder has been detected the alarm remains on until manually turned off and reset. A variety of remote alarms which plug into any 120 VAC outlet without additional wiring are available fo~ use with the CA1A. New CA1DC CRIME ALERT© This model operates on both 120 VAC and 12 to 18 VDC.
File Info : application/pdf, 76 Pages, 7.60MB
Document DocumentElectronics Worlá
TELEPHONE ATTACHMENTS-What Is Available?
JULY, 1971 60 CENTS
MEASURING COLOR -TV GENERATED X-RAYS
BE COOL-COOK WITH A MICROWAVE OVEN
LIGHT EMITTERS & DETECTORS -The Optoelectronics Revolution
TRANSISTOR TESTERS
I1tu r? TLJ
^i' it,:lc:777
I 'l
'oN
'd"H!T-AOZSOC93OA,\tSzZ1.AZ0I'1
iCN?' 61XXE 0T,,1C0-0"7' P
?kdH
S;
How new Memorex
Recording Tape
shattered glass and
why it will make your
favorite music sound better.
To shatter glass with the human voice, a singer must reach and hold the pitch it takes to make a given glass vibrate. That pitch must then be projected with enough volume to vibrate the glass to its shatter point.
We figured if we could capture that precise pitch on our new Memorex Recording Tape and play it back at the same volume, we'd dramatically demonstrate the exactness with which our tape can reproduce music.
So that's exactly what we did. Memorex has increased tape sensitivity, increased high -frequency response, and improved signal -to -noise ratio; so much, that now you can record your favorite music, then play it back the same way it sounded live. You should hear us.
MEMOREX Recording Tape
Reproduction so true it can shatter glass.
Incidentally, our cassette tape also shatters glass.
CIRCLE NO. 130 ON READER SERVICE PAGE
C 970, MEMOREX CORPORATIJ
W you can measure resistors accura
N CIRCUIT in solid state devices
F=21
with 41 -inch
meter $99.51
FE20 HI -LO
with hi- voltage probe and large
six -inch meter
$129.50
WITH THE NEW HI -LO FIELD EFFECT MULTIMETERS
USES ONLY .08 VOLTS TO POWER OHMMETER TO PREVENT TRANSISTORS FROM
CONDUCTING AND UPSETTING READINGS
Look at these extra features to see why the Hi -Lo meter belongs on your want list-
Unbelievable specifications of 15 megotlm input impedance on DC and 12 megohms on AC
Laboratory accuracy of 1.5 percent on DC and 3 percent on AC 9 DC voltage ranges from as low as .1 volts full scale to 1000 volts
3 hi- voltage ranges of 3 KV, 10 KV and 30 KV
9 DC current ranges from 100 microamps to 1 amp
Automatic built -in battery test . . . never a worry about rundown batteries, just push the switches under the meter and read.
Standard .6 amp fuse to protect the ohms and milliamps scales if voltage or overload is accidentally applied. No more need to retJm the
9 DC zero center ranges from .05 volts to 500 volts . . . a must for delicate transistor bias measurements
7 resistance ranges from 1000 ohms full scale to 1000 megohms
meter to factory for repair . . just replace the fuse.
Special probe with 100K isolation resistor in probe to prevent AC pickup or to prevent loading oscillator circuits. Leave in normal position for most tests.
July, 1971
Low voltage of .08
volts prevents tran-
sistors from conduct-
i// ing and misreading circuit. Resistor will now read 10K as it should. Also prevents any damage to transistor.
F CD
riwt Here is why you
should have both Hi and Lo battery volt-
T ages for correct in-
circuit resistance measurements in
solid state circuits:
Higher voltage of 1.5 vcl s causes semi ccrductors to conduct to read prcper frcrt -to -back ratio or conductivity of taansistors. Meter wculd no: be complete vrth-
ou- hi -ohms reading.
INC. 3200 Sencore Drive Sioux Falls, South Dakota 57167
CIRCLE NO. 122 ON READER SERVICE PAGE
CL1
features greater protection range, many new options
for security systems.
1
New CA1A CRIME ALERT() Even 22 feet away, this new ultrasonic intrusion alarm can detect a burglar and take appropriate action. Like
letting out a high -pitched scream or turning on a lamp floodlight, horn or bell. The built -in audible signal may be switched off and the accessory outlet used to give warning at some remote location without alerting the intruder.
Increased detection sensitivity isn't all that's new about the CA1A. It's got four different operating options that give it greater flexibility and allow it to make use of more accessories for a variety of security systems.
Option REMOTE RESET, lets you activate and deactivate the alarm from a remote location. Lockswitch RS1 is recommended.
Option AUTOMATIC RESET, alarm automatically stops after two minutes of operation. Accessory timer CAT 100 must be used.
Option INSTANT RESET, lets alarm trip only when intruder moves. When movement stops, the alarm stops and is instantly and automatically reset, ready to signal the next movement. Accessories like the weatherproof
horn 87600, bell 60006 and rotating red light RRL1 are ideal for use with this option.
Option MANUAL RESET, after the intruder has been detected the alarm remains on until manually turned off and reset.
A variety of remote alarms which plug into any 120 VAC outlet without additional wiring are available fo~ use with the CA1A.
New CA1DC CRIME ALERT© This model operates on both 120 VAC and 12 to 18 VDC. Automatically switches to batteries if AC power fails. Has remote reset automatic reset and manual reset described above. Audible alarm may be switched off.
Normally oper isolated relay contacts may be used for accessories such as DC bell 60007. Three Mallory M915 batteries are recommended for standby power. AC accessories not recommended for use with CA1DC.
Price for either CA1A or CA1DC $99.95. Accessories at additional cost.
Write for bulletin 9 -616 which describes the Mallory full line of security systems.
Batteries
2
Capacitors
MALLORY DISTRIBUTOR PRODUCTS COMPANY
a division of P. R. MALLORY 8c CO. INC. Box 1558. Indianapolis. Indiana 46206; Telephone: 317- 636 -53513
Controls CRIME ALERTm DURATAPE' Resistors Semiconductors Switches Timers Vibrators
CIRCLE NO. 131 ON READER SERVICE PAGE
ELECTRONICS WORLD
r
Electronics World
JULY 1971
VOL. 86, NO. 1
Contents
1rld hOIIICS 11
27
Attachments to Your Telephone Walter H. Buchsbaum
What are some of the devices that can be easily attached to the phone or to the
phone lines? Here are phone- company specs and requirements. along with prices.
TRANSISTOR TESTERS
30 Recent Developments in Electronics 32 Zener Diode Voltage- Regulator Nomograms Chester W. Young
34 Designing a Phase -Shift Oscillator Jon L rui,no
36 Technicians in Britain E. A. Bromfield
THIS MONTH'S COVER shows a grouping of representative transistor testers used for servicing. At the top
left is the Eico 685. Below it is the Heath IM -36. At the top
right is the Hy- Tronix 900. At
the bottom right the RCA WC-
506A is being used to check a power transistor. For specs and prices on these and a
number of other transistor
testers, refer to our article on page 40 of this issue. Cover
photo: Dirone -Denner
37
40
43 44 46
Measuring Color -TV Generated X -Rays J. G. Ello
Descriptions of the various types of survey instruments, their comparative charac-
trrlstcs, and methods of checking color-TV receivers for excessive radiation.
Transistor Testers for Servicing Forest H. Belt
Contrary to early promises, transistors don't last forever. In order to check their performance you need a good transistor tester such as ones described. A complete directory of such service -type testers and their specs is included.
Transistor Testers and Curve Tracers -Directory
Be Cool: Cook with a Microwave Oven William Stocklin
The Optoelectronics Revolution Lothar Stern & Irwin Carroll
Sold atate
their extremely long lives and low power consumption,
are starting to take the place of incandescent lamps and glow- discharge display
tubes. Used as light sources, light modulators, indicators, detectors, couplers,
and sensing arrays, here's what is available now and prospects for the future.
52 Advertising a Service Business John Frye
Publisher LAWRENCE SPORN
61 Miniature Wide -Range V.L.F. Tuner N.H. Brown
Editor
WM. A. STOCKLILA
Technical Editor MILTON S. SNITZER
Managen t Editor PRISCILLA B. HOEFER
66 Remote U.H.F.-TV Signal-Seeking System PaulLeFevre 68 Understanding Complex Waveforms Lawrence S. Nickel
Contrrhut,,, t WALTER H. BUCHSBAUM
Prof. ARTHUR H. SEIDMAN FOREST H. BELT
EW Lab Tested
KU-i Model 41 I ape Deck Sony ST-5100 AM/Stereo-FM Tun
Art Editor
RICHARD MOSS Technical Illustrato r
Reader Service Page
J. A. GOLANEK
Advertising Man g,v
JOSEPH E. HALLORAN
i,
MONTHLY FEATURES
Advertiui,,rt
MARGARET DANIELLO
Associate l'uhli; her STANLEY NEUFELD
4 Coming Next Month 13 News Highlights
20 Letters 60 Books
Group Vice President Electronics & Photographic
FURMAN H. HEBB
70 New Products & Literature
Copyright 1971 by Ziff-Davis Publishing Company. All rights reserved
July, 1971
3
ALWAYS INSIST
ON
CCtC
*CONTROLLED QUALITY CRYSTALS
for your Communications
THE
"ON-CHANNEL"
CRYSTALS by
CHYSTEK
WPM k01118 ^
-- mos. amuse se
14111.111 meant s.
Coming Next Month
Special Feature Article
Electronics ` odd
POPiebIC Sound SYSIBms
PORTABLE
SOUND SYSTEMS
FOR PERFORMERS
Putting together such a system is a challenge because performers are usually loud, halls frequently have poor acoustics, and there is plenty of noise and feedback. In this first of a two -part series, Donald L. Patten of Shure Brothers explains how to select, locate, and hook up mikes and mixers to overcome these problems.
Computer Typesetting
Computers and TV -like scanning techniques are helping
publishers keep abreast of the information explosion. David L. Heiserman explains how the RCA Videocomp works-photographing lines of type from the screen of a
CRT at speeds of up to about 1000 words per second.
Do We Need 4-Channel Stereo?
Frank Krausser of Fisher Radio thinks so. He contends that stereo reproduction through four channels can improve the listening experience considerably, provided certain psy-
choacoustic factors are taken into consideration.
A Close Look at TV Lead -Ins
Here's some practical help in selecting the best TV lead -in for your particular installation. Low loss at u.h.f.; imped-
ance smoothness for color; shielding against interference;
freedom from aging-these are all current requirements
and Forest H. Belt explains their importance.
An Improved
Vehicular Intrusion Alarm
An interior-mounted "on -off" switch makes this alarm system virtually burglar-proof. Adjustable time -delay circuits sound horn a short time after the car door is opened. Component parts are readily available and inexpensive.
OW N
YOU CAN
Z/PORDER
THE CQC CRYSTALS YOU WANT
Your electronics dealer has new, fast, direct- factory ZIP-Order Purchase Certificates to enable you to get CRYSTEK CB, Monitor or Amateur Controlled Quality Crystals mailed direct to you promptly. Ask about them.
CRYSTEK
i
formerly
TEXAS CRYSTALS
Div. Whitehall Electronics Corp.
1000 Crystal Drive
4117 W. Jefferson Blvd.
Fort Myers, Florida 33901
Los Angeles, California 90016
CIRCLE NO. 143 ON READER SERVICE PAGE
4
... All these and many more interesting and informative articles will be yours in
the August issue of ELECTROVICS WORLD .
on sale July 20th
.
ZIFF-DAVIS PUBLISHING COMPANY
William Ziff, President W. Bradford Briggs, Executive Vice President Hershel B. Sarbin, Senior Vice President and Secretary Stanley R. Greenfield, Senior Vice President Philip Sine, Financial Vice President and Treasrrer Walter S. Mills, Jr., Vice ?resident, Circulation Phillip T. Heffernan, Vice President, Marketing Frank Pomerantz, Vice President, Creative Services Arthur W. Butzow, Vice President, Production Edward D. Muhlfeld, Vice President, Aviation Division Irwin Robinson, Vice President, Travel Division George Morrissey, Vice President Sydney H. Rogers, Vice President
Editorial and Executive Offices One Park Avenue New York. New York 10016 212 679 -7200 NEW YORK OFFICE 212 679 -7200 Joseph E. Halloran. Adv. Mgr. M30I7DNWoErtShTMERicNhigOaFnFAICveEnue CGheiocraggeo.B.IlMlineonins i6o0n6.8J1r.312 726-0892 9W02E5SWTEilRshNireOFBFoIuCleEvard Beverly Hills, California 90211 W21e3sCteRrneaAtvdivewert4is-i0n2g65M; BaRnaadgsehr,awBu2d-1D1e6a1n JAPAN; James Yegi. Oui Palace Aoyama 6-25- Minami Aoyama. 6- Chome. Minata -ku Tokyo 407. 1930/6821 CIRCULATION OFFICE P.O. Box 1093, Flushing. N.Y. 11352
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EPuLbElCisThiRnOg NCIoCmSpWanOy-RaLlDso(Jtuhley,pu19b7l1is, hVerosl.
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ELECTRONICS WORLD
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CREI Programs cover all important areas of electronics including communications, automatic control, computers, even digital communications. You're sure to find a program that fits your career objectives.
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July, 1971
5
HI -FI PRODUCT REPORT
Hirsch-Houck Labs by
KLH Model 41 Tape Deck
Sony ST-5100 AM /Stereo-FM Tuner
KLH Model 41 Tape Deck
For copy of manufacturer's brochure, circle No. 1 on Reader Service Page.
LTHOUGH the Dolby "B-type" noise- reduction system is now incorporated in several cassette recorders, we
know of only one reel-to-reel tape recorder with a built-in
Dolby system-the KLH Model 41. This is a compact, low-
priced tape deck with a minimum of frills (barring the Dolby circuits, which we would hardly classify as a "frill"), but clearly designed to provide the optimum combination of quality and low operating cost when fed into a home music system.
The deck is a three -speed, single -motor stereo machine, assembled on a rigid cast plate. Its electronics portions are built on seven printed boards. One is a long master interconnection board, which carries the sockets into which the six smaller boards are plugged.. The printed-circuit boards are readily accessible from the rear for servicing or adjustment.
The unit has three heads, but cannot be used as a simultaneous recording /playback machine for monitoring off the tape. It has only a single set of Dolby circuits, which are switched from record to playback. The transport operation is controlled by a single knob, which has an ingenious mechanical interlock to prevent accidental tape breakage or spilling when going rapidly from fast-forward or rewind to normal playing speed. Before entering normal speed from a fast speed, it is necessary to wait about 2 seconds for the tape to come to a complete stops The knob will not move into Play until that time has elapsed. When going from Stop to Play there is also a delay of about 2 seconds, for a different reason. Power is removed from the playback amplifiers in the fast speeds, to eliminate annoying squeals from the speakers. There is a noticeable time required for the amplifiers to reach their operating condition in Play, but this can be avoided by first going into Pause for a moment. This situation does not exist during recording, as the recording
B
amplifiers are turned on whenever the power is applied to the deck.
The deck has individual illuminated vu meters which read both recording and playback levels of the two channels. Each channel has its own recording -level control, for balancing, and a master gain control sets the over-all recording level. Playback level is adjusted by a control under the deck. Also under the deck are the two pairs of line inputs, with different sensitivities, and the outputs for an external stereo power amplifier. A pair of microphone jacks are recessed into the right side of the unit.
The front-panel control lineup is completed by the two record safety buttons and their signal lights, and three lever switches controlling line power, Dolby operation, and play-
back mode. The latter switch can feed either channel
through both outputs for mono playback or provide normal stereo operation. A four -digit index counter and a small lever for speed changing are on the deck near the head covers.
KLH specifications are based on the use of standard tape
formulations, such as 3M #111 or # 190, and the machine
is normally biased and equalized for these tapes. If one chooses to use the more expensive low -noise tape, such as the 3M #201 series, bias and equalization must be re-adjusted for the tape used. This can produce a slight extension of high-frequency response and improvement in signal-tonoise ratio, although as our tests showed this is hardly need-
ed.
Laboratory Use Tests
In our laboratory measurements, using 3M #111 tape,
i4 the record /playback frequency response at 33/4 in /s was
within dB from 20 Hz to 16 kHz. There was a broad rise in the upper-middle and high-frequency range, reaching a maximum of +6 dB at about 6 to 7 kHz. This rise was accentuated by a couple of dB when the Dolby was used, an effect which we have observed with all the Dolbyequipped cassette decks we have tested. At P/8 in/ s, the
response was within ±4 dB from 20 Hz to 7500 Hz, sur-
passing KLH specifications although not quite of true "hifi" caliber.
The real surprise came at 7'/2 in /s. The response was within ±2 dB from 25 Hz to 20 kHz, which is excellent by any standards. Since response did not appear to be dropping off at 20 kHz, we made a response curve from 20 to 40 kHz and found that the output did not drop off until we passed 30 kHz. Over-all, the 7'/2 in record /playback re-
5
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5 +5
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S S/A Ws (AMPEX 31531-01 TAPE)
II I
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- FREQUENCY Hz
ELECTRONICS WORLD
sponse was ±2 dB from 25 Hz to 28 kHz, far exceeding
KLH specs.
The playback response, with Ampex test tapes, was excel-
lent. At 33/4 in /s it was within ±1 dB from 50 Hz to 7500 Hz; while at 71/2 in /s it measured ±1.5 dB from 50 Hz to 15
kHz.
The transport operated slightly fast (about 2.5 %), which would produce a timing error of 45 seconds in 30 minutes of playing. This should not be a problem in home- recording
applications. Wow and flutter were very low; with wow measuring 0.03% and less than 0.01% at 33/4 and 7'/2 in / s, respectively, and with flutter measuring 0.12% and 0.08 %, respectively (about half the specified limits). The fast-speed operation of the deck was within specifications, but rather
slow for our taste. It took 182 seconds in fast-forward and
104 seconds in rewind to pass 1200 feet of tape.
To reach a 0-dB recording level, an input of 96 or 310 millivolts (depending on one's choice of input sensitivity) was required at the line inputs, or 0.59 millivolt at the microphone inputs, which have a 1000-ohm impedance. The playback output at 0 dB was 1:85 volts, which could be
adjusted downward by the control under the deck. Cross
talk between channels was unmeasurable, being below the noise level. The distortion was 1.6% at 0 dB and reached the standard 3% level at about +2.5 dB.
The signal-to-noise ratio was 51 dB without the Dolby and 56 dB with it, referred to the 3% distortion level, at either 33/4 or 7'/2 in/ s. These figures are from 7 to 10 dB worse than KLH specifications, although they would be considered quite low for any home tape recorder, at least at the lower speed. Like KLH, we restricted our measurement bandwidth to the audio range (actually 22 kHz) to
exclude ultrasonic noise.
We recorded FM broadcasts, disc records, and inter station FM hiss on the Model 41, using 33/4 in /s. In the case of the records and the hiss, we were able to make an A -B
comparison of the playback with the incoming signal. With noise, the high-frequency emphasis could be heard distinctly, together with a slight loss in extreme highs. In the case of music, it was sometimes possible to detect these response characteristics, but only by direct comparison with the original. At 7'/2 in /s, music emerged unaltered from the recorder, although we heard a slight accentuation of the extreme
highs with noise signals. Subjectively, the Dolby circuit had a much more impres-
sive effect than the mere 5 to 8 dB measured improvement would indicate. Our test instruments are not frequency sen-
sitive, while the ear is most sensitive to high frequencies which are actually reduced about 10 dB.
In view of the excellent frequency response and low
noise of the deck at 33/4 in / s, using relatively inexpensive
standard tape, we must conclude that KLH has achieved its aim of producing a tape recorder for home use which can do essentially perfect recording of FM broadcasts and disc records at the lowest possible operating cost. Although the best cassette decks can come very close to matching this
performance, cassette tapes are relatively expensive and do not offer the convenience of editing that one enjoys with open -reel tapes. Furthermore, a cassette deck which is at all comparable to the Model 41 costs at least as much and, in some cases, considerably more.
The KLH Model 41 is supplied complete with a wooden walnut-finished base. It measures 14'/4" wide X 113/a" deep
X 53/8" high and weighs about 19 pounds. The suggested retail price is $249.95, but the tape deck is widely offered at
about $200.
Sony ST-5100 AM /Stereo-FM Tuner For copy of manufacturer's brochure, circle No. 2 oui Reader Service Page.
+10
f I 1111
111
+5
AUDIO OUTPUT Oae =IV
o
SONY ST -5100 MONO FM
W 25
J-30 -35 -40
I F USABLE SENSITIVITY 2.6)JV
45 -501
TOTAL D STORTION, NOISE, HUM RE 100% MOD. AT 400Hz
2
5 R.F.
TE10ST-
20 SIGNAL
50 00
INPUT IN
5k
Ok 20k
MICROVOLTS 1,1.1V)
50k 400k
July, 1971
CONY'S Model ST-5100 AM /stereo-FM tuner is a companion to the TA-1144 amplifier, which it closely re-
sembles in styling. Like the TA-1144, it has a silver-colored, satin -finished panel, with a large black central cut -out for the dial and twin tuning meters. The FM dial scale has linear calibrations, and the tuner features both relative signalstrength and zero-center tuning meters. At the lower right of the dial opening the word Stereo lights up in red when stereo-FM broadcasts are being received by the tuner.
Dominating the center of the black dial area is the only
knob on the ST-5100-the large, fluted tuning knob. The
tuning is smooth and free from backlash. At the left side of the panel is a lever switch controlling the power and on the right side of the panel is a similar switch which selects FM or AM reception. The other controls on the panel are four push-buttons. The two at the right control a.f.c. and stereo/ mono operation (stereo switching is automatic when the button is in the stereo position); at the left are the muting and high-blend switch. The tatter function, which blends the two channels somewhat at high frequencies to reduce
7
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5" Bent Thin Chain Nose. For handling fine wires in close quarters. No. 79CG 51/2' Thin Needle Nose. For firm gripping and looping of wires. No. 57CG 4" Full Flush Cutting Diagonals. Snap cuts to the extreme tip. No. 84CG 5" Midget Slip Joint. Narrow jaws for close quarter wo-.k. 3 openings to '/Z ". No 50CG
REQUEST CATALOG
nationwide availability through local distributors
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CIRCLE NO 117 ON READER SERVICE PAGE 8
background hiss on weak stereo signals while retaining most of the stereo effect, is found on many tuners. However, on the ST -5100 its operation is automatic when signal strength falls below about 100 microvolts. The listener is unlikely to be consciously aware that the blending has taken place, merely that the ST -5100 sounds quieter than most tuners when receiving weak signals. The muting takes place for signals below 8 microvolts, when the switch is actuated.
In the rear of the tuner are the ferrite -rod antenna for AM, the external antenna terminals, and two pairs of audio outputs. One is at a fixed level of about 1 volt; the other can be adjusted to any level that is desired up to 2.5
volts.
The front-end of the tuner is novel in its use of three tuned circuits ahead of the FET mixer, but there is no active r.f. amplifier. This combines excellent image and spurious-response rejection with exceptional freedom from over-
load in strong -signal areas. Also unusual for a new tuner design is the absence of IC's. However, the discrete-component i f. section has seven stages, with
+s
U.S.A. and Canada) have a dual primary transformer for 100- to 240-volt operation. Inside the tuner is a switch to change the FM de- emphasis from the U.S. standard of 75 microseconds to the 50 microseconds used in Europe.
Laboratory & Use Tests
In our lab tests, we measured the FM IHF usable sensitivity of the ST-5100 at 2.6 microvolts, exactly as rated. The limiting action was complete at 5 microvolts and the measured distortion for that and higher input levels was the 0.5% residual level of our signal generator. The outputs of the multiplex circuit are filtered with exceptionally effective low -pass filters to remove virtually all 19 -kHz and 38 -kHz components, yet with negligible effect on the frequency response up to 15 kHz. We measured the response at ±1 dB from 30 Hz to 13.5 kHz, and it was down only 2.5 dB at 15 kHz. Stereo separa-
tion was between 30 dB and 35 dB
from 100 Hz to 2.5 kHz and reached a minimum of about 14 dB between 10 kHz and 15 kHz. The AM rejection was 56 dB, exceeding Sony's specification of 50 dB. Signal-to-noise ratio was also
o
FREQUENCY RESPONSE
5
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-25
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>
I4
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SSOTNEYRESTO
5100 FM
AVERAGE BOTH CHANNELS
SEPARATION
45
50 20
50 70 100 200
500 700 1k
2k
FREQUENCY -Hz
5k 7k 10k
20k
six permanently aligned ceramic fil-
ters. The last two stages include diode limiters followed by a ratio detector. Interstation noise is sensed at the input to the sixth i.f. stage and _its rectified average value controls a FET switch in
the audio output of the detector for
muting. A separate, similar noise-sens-
ing circuit, one stage earlier, operates the automatic high -blend circuit.
The AM tuner has an r.f. stage, FET mixer, and two i.f. stages with two permanently aligned ceramic filters for selectivity. Although no measurements were made on it, it had good audio
quality.
The power supply is electronically regulated and the power transformer is tapped for 100- or 120 -volt a.c. line power. Export models (outside the
better than rated-74 decibels versus
the 70 decibels specified. The subjective performance of the
tuner leaves little to be desired. It is one of the smoothest handling units we have used, with excellent mechanical "feel." The quiet background and general freedom from hiss on almost all FM signals, weak or strong, is immedi-
ately apparent and sets the ST -5100
apart from many other tuners we have operated. The sound is clean and effortless and tuning is non -critical.
Our chief criticism is the dim illumination of the tuning meters. Otherwise, this is a delightful tuner to use, in every respect.
The price of the Sony ST -5100 is $219.50, including a matching dark-
gray metal cabinet.
ELECTRONICS WORLD
There is no substitute for training
on real electronic equipment.
It's just as easy to train on the type of equipment technicians actually use
and service. And it's a lot more practical. Take TV
Servicing, for instance. You'll have it all over the man whose
only experience has been on a TV re-
ceiver designed strictly for training purposes.
NTS Project-Method courses in Electronics combine the latest, professional equipment with easy -to -grasp lessons, texts and manuals. You build your equip-
ment a stage at a time, and then use the equipment on projects that duplicate actual servicing problems.
It's like getting on- the -job experience
at home. Here's just some of the equipment
you get to keep, and what you will learn. You'll get all the details when you receive the NTS full-color catalog.
5 watt AM transmitter receiver
4111111
5"
Oscilloscope
e
+
o
t»>
Exclusive
NTS COLOR AND B &W T.V. SERVICING
Compu- Trainer"
N -S ELECTRONIC &
NTS ELECTRONICS COMMUNICATIONS
You receive a color TV with
many unique features, including built -in self- servicing equipment so you can
COMPUTER TECHNOLOGY
One of the 10 important kits included is this remarkable
AND F.C.C.
Two exciting courses in the big -paying fields of transmitting and receiving. Either
NTS INDUSTRIAL & AUTOMATION ELECTRONICS
make all normal test opera-
Compu- Trainer" -an NTS
one qualifies you for your
Let NTS put you into the age
tions. You also build an AM-
exclusive. It's a fully oper-
FCC First Class Radio-Tele-
of electronic controls. Sys-
SW radio, solid -state radio, F.E.T. Volt- Ohmmeter, and
aetiro-nalol acdoemdpuwtiethr
logic trainintegrated
phone License. NTS assures you will pass this FCC exam
tems automation is rapidly becoming the emphasis of
electronic tube tester. You
circuits. It introduces you
within 6 months after suc-
modern industry. NTS train-
learn trouble-shooting, hi -fi, multiplex systems, stereo
quickly to the how, what, and why of computers. You
- cessfully completing your
course or your tuition is
ing equipment includes a 5" wide band oscilloscope. You
and color TV servicing.
also receive a F.E.T. Volt Ohmmeter and a 5" wide
refunded. You receive 14 kits to build an amateur
-a also get the new exclusive
NTS Electro-Lab
com-
band oscilloscope-
phone 6 meter VHF trans-
plete workshop. Build five
Solid state
B &W TV
74 sq. in. picture
Mail coupon today for
TS GUIDE ELECTRONICS
ceiver plus NTS' exclusive 6 transistor solid-state radio
and a fully transistorized volt- ohmmeter.
industrial controls to regulate motor speed temperatures, pressure, liquid level
and much more.
(cabinet included)
free, fullcolor catalog
Please rush Free Color Catalog and Sample Lesson, plus information on course checked below. No obligation. No salesman will call.
The B &W TV receiver fea-
that details every
National Technical Schools
tures the latest in solid -state
circuitry, making your TV
training the most modern,
training program we offer. No obligation. No
4000 S. Figueroa St., Los Angeles, Calif. 90037
Master Course in Color TV Servicing
Practical Radio Servicing
most advanced available.
salesman will call.
Color TV Servicing (For advanced
ín FCC License Course
Technicians)
iI Master Course in Electronics
CLASSROOM TRAINING AT LOS ANGELES
You can take classroom training at Los Angeles in sunny
Master Course in B &W TV & Radio Servicing
Technology Industrial and Automation Electronics
Southern California. NTS occupies a city block with over a million dollars in facilities devoted exclusively to technical
n Master Course in Electronics
Communications
Computer Electronics Basic Electronics
Dept. 240 -071
training. Check box in coupon.
APPROVED FOR VETERANS
Name
Age
Accredited Member: National Association of Trade
& Technical Schools; National Home Study Council.
Address
NATIONAL cHNIÇAL SCHOOLS
World -wide training since 1905
4000 S. Figueroa St., Los Angeles, Calif. 90037
-- City
n Check if
interested
in Veteran
- State__ __
Training
Check
if
interested
Zip
only in
Classroom
under new G.I. Bill.
Training at Los Angeles.
July, 1971
9
FREE... Aii
66764 E_TON JOHN Tumblereei Connection Uni LP, 31.R, CASS
3 Stereo LPs or
WITH NO OBLIGATION
66826 BOBBY SHERMAN Portrait cf Bobby Metro LP, ¿TR, CASS
rsc.maIwo"
68023 WOODSTOCK TWO (2 record set) Cotil LP, 8TR, CASS
41213 JESLS CHRIST SUPEFSTRR (2 record set)
Decca LP, 8TR, CASS
36184 DIOMIE WARWICK Very Dionne Scept LP, 8TR, CASS
67517 TFREE DOG NIGHT Golden Biscuits Dunhi LP, 8TR, CASS
68030 CROSBY STILLS NASH & YOUNG Four Way Street (2 record set)
Atlan LP, 8TR, CASS
65797 GABOR SZABO Blowin' Some Old Smoke Budda LP, 8TR, CASS
21597 RIMSKY-KORSAKOV Scheherazade Yorks LP, 8TR, CASS
42780 LED ZEPPELIN II Atlan LP, 8TR, CASS
37833 ROD McKUEIN in The Beginning
Sunse LP, 8TR
43871 STATLER BROS Bed of Roses Mercu LP, 8TR, CASS
33093 IAN S. SYLVIA Greatest hits (2 record set) Vangu LP, 8TR, CASS
44765 SHIRLEY BASSET Is Really Something UniAr LP, 8TR, CASS
21551 BEETHOVEN Piano Sonatas Yorks LP, 8TR, CASS
33182 SUSAN SINGS
SESAME STREET SONGS Scept LP, 8TR, CASS
41217 BERT KAEMP-
FERT Orange Colored Decca LP, 8TR, CASS
Sky
30618 DIANA ROSS Motow LP, 8TR, CASS
37838 FLIP WILSON Flipped Out
39089 5th DIMENSION 38368 VENTURES 10th Sunse LP, 8TR
Greatest Hits SouCi LP, 8TR, CASS
Anniversary Album (2 record set) Liber LP
21633 RED ARMY ENSEMBLE
Yorks LP, 8TR, CASS
42988 ROGER WILLIAMS Love Story Kapp LP, 8TR, CASS
42986 ROGER WILLIAMS Golden Hits Vol. II Kapp LP, 8TR, CASS
48800 B. B. KING Live At Cook County Jail ABC LP, 8TR, CASS
38373 IKE & TINA TURNER Workin' Together Liber LP, 8TR, CASS
75002 JACKSON 5 Maybe Tomorrow Motow LP, STR. CASS
42665 CROSBY STILLS & NASH Atlan LP, 8TR, CASS
43870 MELBA MOORE Look What You're Doing Mercu LP, 8TR, CASS
33099 PDQ BACH Stoned Guest Vangu LP, 8TR, CASS
50506 BUFFY SAINTE -MARIE Wanna Be A Ballerina Vangu LP, 8TR, CASS
32882 JOAN BAEZ Joan Baez 5 Vangu LP, 8TR, CASS
68019 EMERSON, LAKE & PALMER Cotil LP, 8TR, CASS
16595 VIRGIL FOX Bach at the Fillmore Decca LP, 8TR, CASS
See for yourself why over 11/2 million) record and tape collectors paid $5 to join Record Club of America when other recor6 or tape clubs would have accepted them free.
CAN YOU CHOOSE FROM ALL LABELS'
INCSLOURDINTGPES CARTRIDGE AND CASSETTE TAPES'
MUST YOU BUY A "MINIMUM" NUMBER OF RECORDS OR TAPES, HON MANY'
HOW MUCH MUST YOU MEND O FULFILL YOUR LEGAL OBL'CATION'
CAN YOU BUY ANY RECORD OR IAPE you WANT AT A
DISC OLIN T'
DO YOU EVER RECEIVE UNORDERED RECORDS OR TAPES'
HOW LONG MUST YOU WAIT FOR SELECTIONS TO ARRIVE,
Citadel Record Club las adv. In
TV Guide Oct. 3, 1970)
NO
12
559.76
10
571.75
NO
YES
5 to 6 weeks
Columbia Stereo Tape Cartridge Service
(a5 adv, it
Esquire Nov. 1970
NO
12
$83.76
10
S95.40
NO
YES
5 to 6 weeks
Capitol Record Club (as adv. in
Look Ian. 26, 197s
Columbia Record Club I
(a5 adv. in Playboy
Feb. 1971)
NO
NO
12
$59.76 t0
$71.76
NO
10
$49.80 to
$59.80
NO
YES
6' 5 to
weeks
YES
S to 6 weeks
RCA Stereo O Tape Club
(as adv. in Esquire
Cct. 7970`
RECORD CLUB OF AMERICA
Choose any LP or tape
On any label! No excep
'inns! over f3a0ctui ers
NO
YES! ncluding n Capitol. Co.
lumbia, RCA, An Be 1,
London. etr.
No oó11 8 atiorr! No
yearly quota! Take a5
6
NONE!
!^any, as rew, or notn. m g at all it you so de.
ride!
e41.ó11 10
$47.10
You don't have to spend ZERO a penny -because you're
nootf "legally oaligated"
DOLLARS buy even a single
record or tape!
ND YES
Your discount up to
ALWAy$
t Dever
OFF. less
Guaranteed than r third!
No exceptions'
There are no cards
which you must return.
NEVER!
Otanpleys
the you
records want are
and sent
-and only when you ask
us to send them.
5 to- 6 weeks
NO LONG
Your same
order day received.
ed
WAITS! Shipping on oar
TYPICAL "EXTRA DISCOUNT" SALE
$4.98 LPs average as low as $1.96 $5.98 LPs average as low as $2.25 $6.98 LPs average as low as $2.56
Savings of 63% or more from recent Club sales up
to $4.42 per LP. Start these giant savings now... not after you fulfill your obligation like the other
clubs.
Average List Club
AndyWilliams -Love Story
Anne Murray
Ed Ames -This Is
2001 -A Space Odyssey
Mary Travers -Mary
Label Colum Capit RCA
MGM WarBr
Price 5.98 5.98 6.98 6.98 4.98
Price 2.25 2.25 2.56 2.56 1.96
Creedence Clearwater
Revival -Pendulum
Fanta
Miles Davis- Bitches Brew Colum
Love Story-Soundtrack
Param
Perry Como-It's Impossible RCA
Bloodrock -3
Capit
Santana -Abraxas
Colum
Worst of Jefferson Airplane RCA
4.98 5.98 5.98 5.98 5.98
5.98
5.98
1.96 2.25 2.25 2.25 2.25 2.25 2.25
RECORD CLUB OF AMERICA The World's Largest Record and Tape Club
10
ELECTRONICS WORLD
Crtridge
Ilorlh
ia lily i e taa,s.e<<Xhoull lloro $Pa
TO BUY ANYTHING EVER!
... Yes, take your pick of these great hits right now! Choose any 3 Stereo LPs (worth up to $20.94) or any 1 Stereo Tape (cartridge or
cassette, worth up to $13.96) FREE as your welcome gift from Record Club of America when you join at the low lifetime membership fee of $5.00. You can defer your selection of FREE items and choose from an expanded list later if you can't find 3 LPs or 1 Tape here. We make this amazing offer to introduce you to the only record a, tape club offering guaranteed discounts of 331/2 % to
79% on all labels -with no obligation or commitment to buy anything ever. As a member of this one -of -a -kind club you will be able to order any record or tape commercially available, on every label- including all musical preferences. No automatic shipments,
no cards to return. We ship only what you order. Moneyback guarantee if not satisfied.
66738 NEIL DIAMOND Tap Root Manuscript
Uni LP, 8TR, CASS
1110141-
65793 BREWER & SHIPLEY Tarkio KamSu LP, 8TF, CASS
ú4. AIM/PH
'M,teaaNt i,wOia>, <
38376 CANNED HEAT
'N JOHN LEE HOOKER (2 record set) Liber LP
42784 STEPHEN STILLS Atlan LP, 8TR, CASS
66709 ORSON WELLES Begetting of the
President Media LP
65784 MELANIE Leftover Wine
Budda LP, 8TR, CASS
21537 TCHAIKOVSKY 1812 Overture Yorks LP, 81R, CASS
41152 WHO Tommy (2 record set)
33185 JOSEPH & THE
33183 B. J. THOMAS
AMAZING TECHNICOLOR Most of All
67519 STEPPENWOLF Gold
33092 BEST OF BUFFY 44746 DUKE ELLING-
SAINTE -MARIE
TON 70th Birthday
33179 DIONNE WAR -
WICK I'll Never Fall In
Decca LP,8TR, CASS
DREAMCOAT
Scept LP, 8TR, CASS
Dunhi LP, 8TR, CASS
(2 record set)
Concert
Love Again
Scept LP, 8TR, CASS
Vangu LP, 8TR, CASS
(2 record set) SoISt LP Scept LP, 8TR, CASS
44726 FERRANTE & TEICHER 10th Anniversary Album (2 record set) UniAr LP
44757 BEST OF GORDON LIGHTFOOT UniAr LP, 8TR, CASS
28082 GREGORIAN CHANT TREASURY Yorks LP, 8TR, CASS
42911 MAN OF LA MANCHA Original Cast Kapp LP, 8TR, CASS
33134 B. J. THOMAS Greatest Hits Vol. 1 Scept LP, 8TR, CASS
65796 CAL TJADER Tjader-Ade Budda LP, 8TR, CASS
65775 VERY BEST OF LOVIN' SPOONFUL KamSu LP, 8TR, CASS
44753 TRAFFIC John barleycorn Must Die UniAr LP, 818, CASS
33065 JOAN BAEZ
NOW YOU CAN David's Album
`
CHAIIGl:1'l', TOO! Vangu LP, 8TR, CASS
o
RECORD CLUB OF AMERICA
CLUB HEADQUARTERS YORK. PENNSYLVANIA 17405
Vw041
AT LAST A RECORD AND TAPE CLUB WITH NO "OBLIGATIONS" -ONLY BENEFITS!
Yes -Rush me a lifetime Membership Card Free
Ordinary record and tape clubs make you choose
LPs or tapes will be sent later). If you can't find
Giant Master LP & Tape Catalog, and Disc & Tape
from a few labels- usually their own! They make you buy up to 12 records or tapes a year-usually
at list price -to fulfill your obligation. And if you
3 LPs or 1 tape here, you can defer your selection and choose from expanded list later. This entitles you to LIFETIME MEMBERSHIP-and you
Guide at this Special Membership Offer. Also send me the 3 FREE LPs or 1 FREE tape which I have indicated below (with a bill for a small mailing and
forget to return their monthly card -they send
never pay another club fee. Your savings have
handling charge). I enclose my $5.00 lifetime mem-
you an item you don't want and a bill for $4.98, $5.98, $6.98, or $7.98! In effect, you may be
already more than made up for the nominal membership fee.
bership fee. This entitles me to buy any LPs or tapes at discounts up to 79 %, plus a small mailing and
charged almost double for your records and tapes.
BUT RECORD CLUB OF AMERICA ENDS ALL THAT!
We're the largest all -label record and tape club
NOW YOU CAN CHARGE IT
If you prefer, you may charge your membership to one of your credit cards. We honor four dif-
ferent plans. Check your preference and fill -in
handling charge. I am not obligated to buy any records or tapes -no yearly quota. If not completely delighted I may return' items above within 10 days for immediate refund of membership fee.
in the world. Choose any LP or tape (cartridges
your account number on the coupon.
3 FREE LPs
and cassettes), including new releases. No exceptions! Take as many, or as few or ro selections at all if you so decide. Discounts are
GUARANTEED AS HIGH AS 79% OFF! You always save at least 331/3 %. You get best sellers for as low as 99f.
- LOOK WHAT YOU GET
FREE Lifetime Membership Card guarantees
... you brand new LPs and tapes at discounts up
so 79% Never less than 1/3 off.
FREE Giant Master LP and Tape Catalog -lists
all readily available LPs and tapes (cartridges
or 1 FREE TAPE 8 track cassette
NO AUTOMATIC SHIPMENTS With our Club there are no cards which you must return to prevent shipment of unwanted LPs or tapes (which you would have to return at your
own expense if you have failed to send written notice not to ship). We send only what you order.
and cassettes) of all labels (including foreign)
... all musical categories.
- FREE Disc and Tape Guide The Club's own
Magazine, and special Club sale announcements
which regularly bring you news of just- issued new releases and "extra discount" specials.
or M r. Mrs. Miss
Address
Defer Selection -send expanded list.
HOW CAN WE BREAK ALL RECORD
FREE ANY 3 Stereo LPs or any 1 Tape shown
AND TAPE CLUB RULES?
here (worth up to $20.94) with absolutely no
City
State
Zip
We are the only major record and tape club NOT OWNED...NOT CONTROLLED...NOT SUBSIDIZED by any record or tape manufacturer anywhere. Therefore, we are not obliged by company policy to push any one label. Nor are we prevented by distribution commitments from offering the very newest LPs and tapes.
SPECIAL INTRODUCTORY MEMBERSHIP OFFER
obligation to buy anything ever!
GUARANTEED INSTANT SERVICE All LPs and tapes ordered by members are shipped same day received (orders from the Master Catalog may take a few days longer). ALL
RECORDS AND TAPES GUARANTEED- factory new and completely satisfactory or replacements will be made without question.
# All Servicemen write Soc. Sec
CHARGE IT to my credit card. I am charging my $5.00 membership (mailing and handling fee for each FREE LP and tape selected will be added).
Check one: Diners Club
Master Charge
American Express
BankAmericard
Join RECORD CLUB OF AMERICA now and take advantage of this special Introductory Member-
ship Offer. Choose any 3 LPs or any 1 tape shown here (worth up to $20.94) and mail coupon with check or money order for $5.00 membership fee (a small handling and mailing fee for your free
MONEY BACK GUARANTEE
If you aren't absolutely delighted with our dis-
counts (up to 79 %)- return items within 10 days
and membership fee will be returned AT ONCE! Join over one and one -half million budget -wise record and tape collectors now.
Acct
Expiration Date
Signature
Canadians: mall coupon to above address. Orders to be serviced from Canada.
RECORD CLUB OF AMERICA -The World's Lowest Priced Record and Tape Club
July, 1971
CIRCLE NO. 124 ON READER SERVICE PAGE
11
GTE Sylvania has the lines that lay it on the line.
Only GTE Sylvania gives you a choice of three different price lines n color picture tubes.
And GTE Sylvania tells you and your customer exactly what you are getting in each line.
That makes Sylvania tubes easier to sell. You can tell your customers the advantages of the top -line color bright 85® XR. You can show them where the savings come from in the economy color screen 85 line. And you can tell them exactly what they're getting for their money in the middle line color bright 85® RE. The way we see it, if we lay it on the line with you, you can lay it on the line with your customers. Instead of just handing them a line.
color bright 3xR color bright Ed RE color screen DE
Sylvania rare earth red phosphors Other manufactured rare earth phosphors All sulfide phosphors X -ray inhibiting glass
New glass
Reused glass
Regunned
Screen blemish specs
White field uniformity
Cut off; purity currents; beam shield leakage
12
yes no no yes yes no no OEM
OEM
OEM
yes
no no no some some no OEM
slightly wider than OEM
OEM
yes
yes
no
no
some
some
SOME
slightly wider than OEM
slightly wider than "RE"
slightly wider than OEM
ELECTRONICS WORLD
NEWS
HIGHLIGHTS
Money for Unemployed Engineers
A $42- million program to help unemployed engineers and scientists find new jobs has been announced by U.S. Labor Secy. Hodgson. Most of the money ($25 million) is to be used to retrain 15,000 in new fields; $5 million is to provide 20,000 with travel money to look for new jobs; $10 million is to reimburse 10,000 for moving expenses; and $2 million is for research. Right now there are between 75,000 and 100,000 unemployed engineers and scientists in the U.S., a good many of whom have been working in the depressed
aerospace industry.
Con sumer Electronics Sales Are Up
It's difficult for a monthly magazine to keep up to the minute on sales figures, especially when they fluctuate as widely as they do in the area of consumer electronics. However, the last quarterly figures we saw from the Electronic Industries Association show healthy increases in sales of TV's, radios, and phonos for the first quarter of 1971 compared to last year. Here are the figures: color TV's up 18 %, black- and -white TV's up 6%, FM home radios up 14.7 %, AM home radios down 2.8%, automobile radios up 24.4%, console phonos down 20.9%, and portable and table phonos up a whopping 51.2 %.
While we're talking about the EIA, we should give you a couple of more figures they are especially proud of. The Association's electronic service technician workshops for high-school instructors will reach 15,000 young men this year, and the sale of the one-millionth EIA- sponsored textbook on consumer electronics servicing was marked recently at a ceremony in New York.
CB'ers Aid Police in California Earthquake
Everyone was pitching in to do their share to help in the violent earthquake that was centered in the San Fernando Valley some months ago. One group we have heard about are those local, CB'ers affiliated with React, which is a national public- service community program to provide 2-way radio communications in emergencies. A number of CB units were used to relay messages to and from the police and hospitals. Messages also handled dispatching authorities, equipment, and volunteers to areas where they were needed. Evacuation orders were sent out to residents below two dams that were in danger of breaking. The main communications control was at the Foothill Division Police Station, from which messages were continuously relayed from units in the area without telephone service. The Citizens Band can be employed for a worthwhile purpose; although it's sometimes hard to believe this if you've monitored some of the idle and useless chatter that you hear on the band around New York City these days.
The Video Cassette Pot is Bubbling
July, 19 71
There is lots of activity in the video -cassette field these days. We recently attended a press conference at which Bob Brockway, president of CBS Electronic Video Recording Div., announced that agreement had been reached with four Japanese manufacturers to make EVR players for sale in the U.S. and Canada. The four are Hitachi, Matsushita, Mitsubishi, and Toshiba; delivery is expected to begin early next year. The EVR players use special film cartridges which are played back through one or more TV receivers. Motorola has been making these players under an exclusive manufacturing license in the U.S. and Canada; the license expires at the end of this year. Motorola issued a statement welcoming the Japanese manufacturers to the U.S. market as a step toward popularizing and standardizing the EVR medium. Most of the company's efforts have been in the school, industrial, and institutional markets, while the Japanese companies seem to be more interested in the home market. Motorola has been selling its EVR color player for around $800. No prices were given for the Japanese models but it was indicated that these would be simpler and not have some of the "industrial" features found in the Motorola players. Our guess is that they will come into the U.S. market at least several hundred dollars cheaper than the Motorola units. They will have to be a lot cheaper than this, however, before we find one in every home. Remember, this system is strictly for playback and does not provide for making your own TV home movies.
At about the same time, Sony announced that it will begin to market its video cassette system in the U.S.
13
early next year. Sony's system uses a cartridge of video tape that is played back on its player through one or more TV receivers. The company's playback unit will sell for around $800, while a blank 60- minute tape cassette will cost approximately $30. Pre-recorded cassettes will be more expensive, though, depending on the particular program offered. Sony is limiting its efforts to the industrial, educational, and institutional markets, saying that the use of the units in the home will be "in the future."
In the meantime, representatives from Avco are talking about extensive additions to its library of pre-recorded magnetic tape cartridges for its Cartrivision system. New programs on such subjects as: the art and sport of fishing, science for young viewers, how to enjoy the arts, and world culture, are some of the offerings. Cartrivision representatives certainly seem to be emphasizing the home market, and they keep talking about home movies taken on blank tape with a separate camera, and played back through the television receiver.
Dolby System for Broadcasters
Our readers are probably quite familiar with the use of the Dolby noise- reduction system in mastering records and tapes, in home tape recorders, and in separate outboard adapters. Dolby Laboratories is now pushing the use of its system to FM broadcasters and in FM tuners and receivers. We recently attended a demonstration of the use of the simple Dolby-B system in a simulated FM broadcast. The normally noisy reception one gets from a distant FM station that is transmitting stereo was just about all gone. It was almost as though the station had increased its power output. This means that the stereo-FM broadcaster should have greater effective coverage and be able to transmit signals with a higher dynamic range. For best results the FM receiver should also have Dolby circuits built in. But even without these circuits, there is an improvement in reception. On receivers without the matching circuitry, the sound appears to be treble- boosted. By simply rolling off the treble somewhat with the treble control, the received audio is flat and noise is reduced. However, since the system is a dynamic one, best results are obtained with the matching circuitry in the receiver.
The system was later demonstrated at the National Association of Broadcasters in Chicago. The first FM tuners and receivers incorporating the Dolby -B system are expected to be on sale later this year.
Audio Tape Cartridge Market Expected to Reach $1 Billion
Sales of equipment and audio tape cartridges mainly for the automobile are expected to break the billiondollar mark in 1971, according to Red Gentry of Motorola Automotive Products. Equipment sales will account for half this amount; cartridge sales for the remainder. Factory and dealer installations on new cars are running at about 5% of domestic new -car sales, with aftermarket sales estimated to be about 7 times the original equipment installations. The home audio tape cartridge market is also beginning to grow steadily, and this may account for one -third of the 1971 sales.
These figures were given at a recent Motorola press demonstration of its new Quad-8 tape players for autos. These players accommodate the increasing number of 4-channel, 8-track tape cartridges that are coming into the market. We heard a demonstration of 4-channel stereo in a car where the four separate speakers were installed in the car's four doors. The player had front-back and left-right balance controls. Talk about being surrounded with sound!
Four -Channel Stereo Adapters
There's some more excitement brewing in the 4- channel stereo field these days. Allied Radio Shack has announced plans to market 4- channel hi-fi equipment under the "Stereo -4" name. Using the matrix system developed by Electro- Voice, Allied will manufacture and market receivers, amplifiers, and an adapter which will make it possible for existing equipment to play back 4- channel sound.
Not to be outdone, Lafayette is also beginning to promote a 4-channel amplifier along with a tape-cartridge deck. The company is also offering a 4- channel adapter, called the "Dynaquad," under license from Dynaco,
Inc.
Upcoming NEA Annual Convention
The National Electronic Associations is getting ready to hold its seventh annual convention on July 12 -18
at the Portland Sheraton Hotel in Portland, Oregon. Sessions are planned on business management and
association matters for the radio-TV service technicians and shop owners who will attend. Fishing trips, a
dance party, and golf are also on the agenda. If you hurry, there is still time to register and attend. Write to:
National Electronic Associations, 1309 West Market St., Indianapolis, Ind. 46222.
A
14
ELECTRONICS WORLD
Electronics World
READER SERVICE PAGE
FREE I N FORMATION SERVICE ! Here's an easy and convenient way for
and to get additional information about products advertised or mentioned editorially (if it has a "Reader Service Number ")
in this issue. Just follow the directions below...
and the material will be sent to you promptly
free of charge.
On coupon below, circle the number(s) that
rE18Cl1'0111es W01'Id
Void 60 days after date of issue,
771
correspond(s) to the key P.O. Box 7842
number(s) at the bottom or
Philadelphia, Pa. 19101
next to the advertisement or
editorial mention that is of
1
2 3
4
5
6
7 8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
interest to you. (Key numbers
26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
for advertised products also
51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75
appear in the Advertisers'
76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
Index.) Print or type yoúr
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15
NRI "hands -on" training in Television, Communications, Electronics and Computers
can give you as much
as 2 years of on-the-job
experience.
- EARN YOUR FCC LICENSE OR YOUR MONEY BACK
NRI Communications training programs will qualify you for a First Class Commercial
Radiotelephone License issued by the FCC. If you fail to pass the FCC examinations for this license after successfully completing an NRI Communications course we will,
on request, refund in full the tuition you have paid. This agreement is valid for the period of your active student membership and for six months after completion of your training. No school offers a more liberal FCC License agreement.
16
ELECTRONICS WORLD
Experience is still your best teacher
NRI Achievement Kit is educator -ac-
claimed and the original "starter" kit in home study training. Imitated but never duplicated, this kit is designed ar.d
- personalized for you and your training objective. It has one
purpose to get you started quickly and easily.
"Bite- Size" Texts average an easily- digested
40 pages of well- illustrated, scientifically prepared sul:ject matter in the course of your choice. Questions in each book are carefully hand -graded and returned to you with helpful instructional notes. You get unlimited personal help from the day you enroll.
.., here's how you get it with
unique NRI training at home
Ask any teacher, job counselor, engineer, technician or prospective employer about the need for practical application of theory in Electronics. He'll tell you Electronics is as much a "hands-on" profession as
dentistry or chemistry. That's how you learn at home with NRI. You prove the theory you read in "bite size" texts, by actual experimentation with the type
- of solid-state, transistor and tube circuits you'll find
on the job today not hardware or hobby kits. You introduce circuit defects, analyze results, discover quickly the kind of trouble- shooting and design techniques that will make you employable in Electronics.
Train with the leader NRI
- NRI lab equipment is designed from chassis up for
effective, fascinating training not for entertainment. The fact that end results are usable, quality products is a bonus. In Communications, for example, you build and analyze, stage by stage, your own 25watt phoneícw transmitter. It's suitable for use on the 80 -meter amateur band, if you have an interest in ham radio. In TV-Radio Servicing your practical training gives you your choice of monochrome or color
- TV sets. All training equipment is included in the low
tuition you pay nothing extra. Discover for yourself the ease, excitement and value of NRI training. Mail postage-free card today for new NRI Catalog . . . or use the coupon below. No obligation. No salesman will call on you. NATIONAL RADIO INSTITUTE, Washington, D.C. 20016.
Designed-For-Learning Equipment
Like this phone -cw transmitter (Kit #7 in the Communications course) is engineered from chassis up to demonstrate principles you must know. NRI does not use modified hobby kits for training, but the finest parts money can buy, professionally and educationally applied.
July, 1971
APPROVED UNDER NEW GI BILL
If you have served since January 31, 1955. or are in service now, check GI line on postage -free card or in coupon.
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CIRCLE NO. 118 ON READER SERVICE PAGE
Punch clean,
true holes
in seconds.
A Greenlee chassis punch is the quickest way yet to cut round, square, key, D, or double -D holes in 16-gauge metal, hard rubber, plastics, epoxy, etc. Available at radio and electronics parts dealers. Or write for Catalog E -730 to: Greenlee Tool Co, 1764 Columbia
Ave., Rockford, Ill. 61101.
GREENLEE TOOL CO
XLO
EX- CELL -O CORPORATION CIRCLE NO. 137 ON READER SERVICE PAGE
IC's IN COLOR TV
To the Editor:
The article by Forest H. Belt on
"Color TV for 1971" (March, 1971) is in error in the description of the IC audio circuits for the Heath chassis. On page
44 the author states: "The Motorola
and Heath chassis use extra audio amplification before the output transistor, too. Most sound -section IC's drive the audio output transistor directly."
The Heath circuit also drives the output transistor by the IC directly. The circuit does have an extra transistor used as an emitter follower to drive the hi -fi output. This is between the second and third stages of the IC at the point
in the circuit where the signal is
brought out of the IC to the volume control.
STANLEY J. BRIGGS
Trenton, Mich.
Reader Briggs is correct as far as the
Heath set is concerned. With regard to Motorola, the statement in the article is
correct in that two driver transistors are used between the output of the audio IC and the input to the audio output transistors.-Editor
PHOTOFLASH NOMOGRAMS
To the Editor: The nomograms (Fig. 3) in the two
articles by Walter W. Schopp ( "Electronic Photoflash Meter," June, 1970; and "Rapid -Flash," April, 1971) do not agree with each other.
According to the June, 1970 article nomogram, beam candlepower seconds (BCPS) can be converted to wattseconds (WS) by using the factor of 35 BCPS =1 WS. Conversion of the 2000 BCPS used in the example gives 57 WS equivalent. Using the 57 WS figure in the nomogram of the April, 1971 article coincides with approximately 1000 BCPS and not the 2000 of the first nomogram.
Reference to Kodak electronic -flash data and specifically pamphlet AC-37
gives a formula for determining a
guide number (GN) as V .05 X BCPS X ASA. Using the information from the June nomogram example of 100 for ASA and 2000 for BCPS produces a GN of 100. Testing this in the April, 1971 nomogram indicates a GN of about 110. Cross- checking these guide numbers against the Kodak AC-37 chart for
a flash of 2000 BCPS shows an ASA of
100 for GN of 100 and an ASA of 125 for GN of 110.
By dividing the WS scale of the April, 1971 nomogram by two, one would get a GN of about 55 for the
2000 BCPS which corresponds to the above checks. It appears then that this WS scale should be divided by two and left positioned as it is.
KENNETH L. ANDREWS Riverside, Calif.
Following is a copy of Author Schopp's reply to the above letter-Ed-
itor
Dear Mr. Andrews: Some of the problems you seem to
have stem from the fact that you put too much stock in light- measurement figures that do not mean too much to the amateur photographer. Light is one of the hardest things to measure. According to what book you read, any figure can be proven. Depending on your particular flash tube and supply efficiency, your supply may provide anywhere from 10 to 50 ECPS (effective candlepower- seconds) per watt second. (Reference to a copy of the General Electric "Flash -tube Data Manual" will substantiate this claim.)
As you can see, this conversion is a very flexible thing and will ultimately depend on the trial -and-error method to eventually come up with the correct figures. The nomogram just provides a starting place. The nomogram appearing in the April issue uses an approxi-
mation of 20 ECPS =1 watt -second,
which I believe to be a more meaningful figure for the lightly loaded flashtube, such as the Kemlite CX2R2 used in the "Rapid-Flash."
In regard to your reference to the nomogram used in the June, I970 issue, I believe you confused the ASA number for the GN, as this nomogram does not show any reference to GN. Using the lines as drawn on the nomogram, GN= distance in feet X "f'-stop number. Thus, GN =10 X 11 =110, which agrees with the nomogram in the April, 1971 issue and also agrees
with the Kodak "Master Photo Guide"
No. R -21.
The more I study this particular sub -
ject, the more I believe that everything written on the subject was de-
ELECTRONICS WORLD
signed to confuse the layman. But one
thing is certain-it's hard to argue with
a good exposure obtained by using the nomogram.
WALTER W. SCHOPP
Livermore, Calif.
*
COLOR ORGANS
To the Editor: In the January, 1971 issue of ELEC-
TRONICS WORLD was an article written by Fred Holder called "Color Organs
& Strobe Lights Enhance Music."
While the article was informative, the list of color organs available today did not begin to list all of them. Here are some more manufacturers and distributors of color organs for the author's (and your readers') information:
Curtis Electro-Lighting, Inc Olson Electronics, Inc
1536 S. Paulina St.
260 S. Forge St
Chicago. III. 60608
Akron, Ohio 44308
Da tee
Box 5203 Fullerton. Cal. 92633
Restivo Psychedelic Lighting 3547 Urscala St. Seaford, N.Y. 11783
KAS Engineering Box 384 Beltsville, Md. 20705
Retch, L. 1636 Canton Ave. Milton, Mass. 02186
Lafayette Radio Electronics Science Workshop
111 Jericho Turnpike
33 Cain Dr,
Syosset, N.V. 11791
Plainview, N.V. 11803
Lightrays 713 Pine St. Philadelphia, Pa. 19106
Southwest Technical Products 219 W. Rhapsody San Antonio, Texas 78216
Murphy Kits 204 Roslyn Ave. Carle Place, N.Y. 11514
Technical Writers Group Box 5994. State College Sta. Raleigh, N.C. 27607
Teletronics Box 1266 S. Lake Tahoe, Cal. 95705
ARTHUR L. STANHOPE
Cherry Hill, N.J.
As we indicated in the article, new companies are coming into the field almost daily so that a complete listing is practically impossible to obtain. We
tried to pick a representative sampling, however; we thank Reader Stanhope
for adding to our list of color organ
manufacturers and distributors.-Edi-
tor
SPECIAL SECTIONS AVAILABLE
For those of our readers who might
be interested in the "Special Sections"
we have published in the past, eight of
the more recent ones (since 1967) are still available in fairly limited quanti-
ties:
"Computer Memories" "Linear IC's" "Solid-State Diodes" "Filters"
"Cables & Connectors" "Linear IC's" "Power Supplies" "Relays"
October, 1970 July, 1970 July, 1969 April, 1969
October, 1968 July, 1968 April, 1968 April, 1967
Send 25e for each to ELECTRONICS WORLD Editorial Dept., One Park
Ave., New York, N. Y. 10016.
A
July, 1971
Allied Radio Shack
Brings Back a "Best Buy:'
And Now It's S19.95 Better!
29995 The Allied' 395
AM/FM Stereo Receiver
So nearly perfect the critics could suggest only one way to improve it: make the $ 19.95 walnut case standard. And we did. Without adding a penny to the price!
Frankly, we goofed! We knew our 395 was a winner, but we weren't prepared
for a flood of rave reviews from all the audio magazines and an enthusiatic "best
buy" rating. Suddenly we were caught with our inventories down. But now the
395 is back with every original feature intact. 195-watt power. FET stereo FM.
Wideband AM. An "everything" preamp with 3 phono inputs, a tape head input
equalized for 71/2 and 33/4 ips, dual concentric bass /treble controls, plus all
-it the usuals. And now the luxurious wood case is included, so we've beat our own
unbeatable value! At ARS stores everywhere. Or you may order by mail costs
you no more!
... Over 950 Stores Nationwide
See the Yellow Pages
2725 West 7th St.
Fort Worth, Texas 76107
/.ILUfD IPA010SHACK
..
il.AT ION COMPANY
Dept. EW-2 I
Rush me the All.ed 395, shipping paid by you. I enclose iJ check Omoney order for 299.95
Name (print)
I Street
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21
The Booming Field in Electronics is
COMMUNICATIONS
The earth becomes smaller and outer space nearer because of the great strides being made in communications electronics. In thousands of applications, from two -way radio to deep space probes, specialized technicians and engineers keep new developments coming and existing equipment operating.
Let Pathfinder School of Electronics train YOU in communications. The dictionary defines "pathfinder" as "one who finds or opens up a way or path
..." Pathfinder School of Electronics is a school dedicated to the purpose of
opening up a path to success in electronics -more specifically, a path to suc-
cess in communications electronics -for those who wish to break into this
amazing field ofemployment.
Pathfinder offers two different courses in communications, one of which is sure to fit your particular need. For those who are in a hurry to get an FCC license, we offer an 88 lesson course in FCC License Preparation. For those who are willing to take more time and want more thorough training (complete communications training) , we offer a 210 lesson course in Communications Engineering Technology. Both courses are prepared in detail, by experts in electronics and education, for easy learning while you
STUDYAT HOME!
Mail the coupon for our free brochure, which gives complete details on the
courses offered.
Enroll Under G. I. Bill
i Pathfinder School of Electronics
1509 N. Western Ave., Hollywood, Calif. 90027
Please send me your free brochure with details and prices of your courses in communications electronics.
I
I
I am a beginner interested in an electronics career.
I have a little experience lkits or other) with electronic equipment.
I am an experienced electronics technician.
NAME
ADDRESS
CITY
STATE
I am eligible for G.I. Bill benefits.
22
AGE
ZIP EW-7-71
Both Pathfinder courses are available under the G.I. Bill, If you served on active duty since January 31, 1955, or are now in the Service, check the box by the bottom line in the coupon.
Pathfinder School of Electronics is accredited by the Accrediting Commission of the National Home Study Council.
PATHFINDER SCHOOL OF ELECTRONICS
1509 N. Western Ave., Hollywood, Calif.
ELECTRONICS WORLD
Put More "GO POWER" into Your Electronics Career
AftlC©)1Y/1 hlIghD
from Technician to
I
D
by studying at home with
GRANTHAM SCHOOL OF
ENGIN EERING
"the college that comes to you"
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Earn a DEGREE in Electronics Engineering
The GRANTHAM educational program in ELECTRONICS ENGINEERING is designed to
upgrade electronics technicians to the engineering level, mostly by home study.
While you continue your present employment, you can
really learn electronics engineering and earn an
ACCREDITED DEGREE. You can upgrade your income and prestige by upgrading your electronics education at the college level.
GRANTHAM'S strong -foundation educational program in electronics engineering is designed especially for the working technician. This program, offered mostly
by home -study, leads to non -obsolescent skills -to skills
based on reasoning -and leads to the DEGREE of Asso-
ciate in Science in Electronics Engineering (the ASEE Degree).
This accredited degree program consists of four cor-
- respondence courses of 100 lessons each -an overall total
of 400 lessons followed by a two-week graduation seminar held at the School. Upon completion of the four correspondence courses, you are awarded a diploma in Electronic Engineering. Then, upon completion of the two -week graduation seminar, you are awarded the ASEE Degree.
Accreditation and G.I. Bill Approval Grantham School of Engineering is accredited by the Accrediting Commission of the National Home Study, is approved under the G.I. Bill, and is authorized under the laws of the State of California to grant academic degrees.
Grantham School of Engineering
UtTklf 04,0 Established in 1 95 1
- What's in Your Future
The Same Old Job, or Success in Engineering?
Where will you be five years from today? Are you headed for real advancement in electronics, or in a rut ? The experience you have as a technician is valuable ; it gives you a head start toward a better future. But to get ahead and stay ahead, experience must be supplemented with more education in electronics and such allied subjects as mathematics, physics, computers, and engineering design.
The Grantham educational program in electronics engineering is not for beginners. Every point is explained just as carefully as if you were a beginner, but the important difference is that while the beginner would need extensive laboratory training, you (as an experienced technician working with modern equipment) do not require such training and should not waste your time doing the same laboratory experiments that beginners must perform. This program in engineering is designed, written, and taught for and to experienced technicians, and beginners are not accepted for enrollment.
rFor complete details, mail postcard or coupon. Grantham School of Engineering EW-7-7I 1505 N. Western Ave., Hollywood, Calif. 90027 Gentlemen: Please send me your free Bulletin which gives corn plete details on the Grantham educational program leading to the Associate Degree in Electronics Engineering. I understand no salesman will call.
Name
1505 N. Western Ave.
Address
HUME yTJ
Hollywood, Calif. 90027
City
Telephone:
State
Zip
(213) 469 -7878
t have been in electronics for
years.
I
July, 1971
CIRCLE NO. 138 ON READER SERVICE PAGE
Y5
4ciannei/2 channel
top choices for the new world of sound
1730 SS
1730 0-SS/AA-6100
An entirely new world .of sound has been created by AKAI's electronics engineers who have developed a new and sophisticated line of 4- channel surround stereo equipment. Included _n this line are the exciting 1730-SS 4-Channel /2-Channel Stereo Tape Recorder and the 1730DSS 4- Channel/2- Channel Stereo Tape Deck. With either system, you're completely surrounded in sound with four
speakers ... left and right in front, and left
and right in the rear. This system gives
you a real "sense of presence", the feeling of being exactly in the middle of a live
performance. Both models are designed to be used for not only 4- channel stereo
but also 2-channel stereo as well.
The 1730 -SS, equipped with four built in pre-amplifiers, two built-in main amplifiers, and two monitor speakers, is designed for amazing versatility. It can be used not only as a complete 2- channel stereo tape recorder, but also as an exciting 4- channel stereo tape recorder by simply adding an extra pair of AKAI speakers to your existing 2- channel stereo amplifier /speaker system.
The 1730D -SS is perfectly matched with AKAI's exclusive AA -6100 Solid State 4-Channel System Pre-Main Amplifier. This amplifier has 80W music power for dynamic 4- channel stereo sound and accommodates both 4-channel and 2channel stereo operation.
Cross over to 4- channel stereo and enjoy the multidimensional sounds no 2-channel system can ever achieve.
Audio & Video
AKAI
AKAI AMERICA, LTD.
2139 East Del Amo Boulevard /Compton, California 90220 (213r 537 -3880 Manufacturer
AKAI ELECTRIC CO., LTD.
F.C. Box 21, Tokyo International Airport, Japan
from July 1 AKAI products will be available in the U.S.A.
1971
26
CIRCLE NO. 150 ON READER SERVICE PAGE
ELECTRONICS WORLD
Attachments
to Your
Telephone
By WALTER H. BUCHSBAUM
What kind of devices can be easily attached to the phone or the phone lines? What are phone company's specifications, requirements, and some prices?
n ... "uAVE an extension phone without paying monthly charges" suggest the ads by dealers in used and reconditioned phones. And they are right, it is now perfectly legal and permissible to connect an extension phone, or any of a host of other devices, to the regular telephone line. Ever since Carterfone Company won the right to connect a radiotelephone to the AT&T network, all sorts of devices have become available for attachment to the telephone. Some of these are simple, like a transistor amplifier driving a built -in speaker; others are complex, like a complete facsimile transceiver unit.
Many thought that the Carterfone case would open
AT&T's lines to practically anyone with any sort of gadget. Newspapers wrote fanciful accounts of devices that would let you turn on home appliances by phone as you leave the office, devices that would print newspapers in your home
during the night, and perform all sorts of other chores-all
directed over telephone lines. Most of these things are technically feasible, but turn out to be so complex and ex-
pensive that the average subscriber would be unwilling to pay the price. There are, however, some phone attachments which are both reasonable in cost and sufficiently useful to assure their growing acceptance.
While the Carterfone decision makes "foreign" or subscriber-owned phone attachments legal, the phone company still has the right to insist that such attachments not in-
July, 1971
terfere with normal telephone operations, deprive the
phone company of its lawful revenue, or create a hazard to its equipment or personnel. It is largely for these reasons that gadgeteers are discouraged from simply connecting their own homemade devices to the phone lines.
What You Can Attach
In theory, any device that receives and transmits information in the band from 300 to 3000 Hz can somehow be connected to the telephone lines. This means human voice as well as digital data, facsimile, and slow-scan TV signals, provided they are modulated on suitable tone signals. Greater bandwidths are available in certain areas, but the average telephone lines going into homes and offices are bandwidth -limited.
The most basic attachment, that almost anyone can install, is an extension phone or bridge. This is simply another
telephone set, connected in parallel with the existing phone. With this arrangement both phones will ring and
either phone can be used to dial calls. If two people are using the phones, the sound levels will be reduced to approximately half. If more than two phones are connected in parallel, the loading of the line becomes too great and special circuits must be provided. There is nothing illegal or wrong in buying your own phone and connecting it across an existing phone, provided your phone meets the techni-
27
HANDSET OFF -HOOK
WAIT FOR DIAL TONE
1
DIAL
WAIT FOR SIGNAL
RING SIGNAL WAIT FOR ANSWER
CONVERSATION
HANDSET ON-HOOK
Fig. 1. Flow chart showing steps taken when making a call.
HOOK
DIAL
J- SWITCH
O=. LINE
O
RINGER TC2
CI VR I
HYBRID COIL
VR2
C XTMR.
RC VR.
a
Fig. 2. Simplified circuit diagram of standard telephone set.
6IM BREAK CLOSED
OPEN
D4AL ,LGE.
NOMINAL 100
L_ISECONDS
j
INTERDIGITAL T.ME 600 MILLSECONDS
INTERDIGITAL TIME
r OF 6001 MILLISECONDS
DIGIT 3
DIGIT J
1_ 0 UI
-II DIAL PULSE RATE -NOMINAL 10 PULSES PER SECOND IA MIN
MAX 1
PERCENT BREAD - NOMINAL 61 ISB MIN -6A MAX .1
UNTERDIGITAL TIME -MINIMUM OF 600 MILLISECONDS
Fig. 3. Typical dial -pulse pattern when dialing "3,1,2."
cal specifications of the telephone company and does not cause interference or degrade telephone service.
Another popular attachment is a loudspeaker and amplifier system, allowing "hands-free" phone conversations and permitting several people to participate in a phone conference. In one version the telephone handset is acoustically coupled to the amplifier system, but in another version it is connected directly into the voice circuits of the handset. In this arrangement the phone can also be used as part of an intercom system. A number of such arrangements are possible, but since they require connections directly into the telephone set, the property of the phone company, you either have to know exactly what you are doing or else you have to rent a "voice coupler" from the local phone compa-
ny which will install it for you. Commercial establishments can now purchase their own
internal switching equipment, such as manual switch-
-a boards, PBX's, or special -purpose equipment, and the
phone company will rent suitable interface equipment
28
more complex type of coupler. Some of these installations involve whole racks of equipment, power supplies, relays, dialers, ringers, and tone generators, assembled to fit specific customer requirements.
Commercial customers can also rent special couplers to connect their facsimile machines, teletypewriters, and other data terminals to the telephone network. If acoustic couplers are used, the telephone company does not get involved and can only charge regular voice -transmission rates. In many applications, however, acoustic couplers are not desirable and then direct connections, via phone -company couplers, are used.
Private subscribers most frequently want to connect an automatic telephone answering machine to the phone and this usually involves rental of a suitable coupler. Automatic alarm systems, which dial the police or fire departments and then transmit a tape- recorded message, are generally connected through a phone-company- furnished coupler. Radiotelephone and private-wire phone systems, which connect to the AT&T or other public network, also require couplers and, usually, special installations.
Aside from the legal requirement that the attachment may not disturb the telephone network, there are valid technical and economic reasons for using company-furnished and installed couplers. Initiating or receiving a phone call involves a number of simple human functions, such as waiting, dialing, listening, and recognizing different signals-functions that are not as easily implemented by automatic electronic devices. It is usually cheaper for the individual subscriber to rent the specific coupler he needs than to design, test, and maintain his own device. As we shall see, the monthly rental charges are moderate.
Principles of Telephone Operation
Consider what you do when you call someone. The flow chart of Fig. 1 illustrates the separate actions required and we can see at once that any automatic call -initiating device will have to contain timers, tone detectors, and logic circuits, in addition to the stored message. The device will have to recognize a dial tone, generate the correct dial pulses, recognize a busy signal as well as a ring signal and, depending on which it receives, either go "on- hook" and start the cycle over again or wait until the ring is answered before it can play its message.
When the device is intended only to receive calls, some of the complexity is reduced but, in many cases, other problems are added. Playing messages back on demand over the phone requires the recognition of a special code, rewinding of the tape, and resetting to the "call-receive" mode.
The basic telephone circuit for almost all phones currently in use is shown in Fig. 2. When the handset is on the cradle, the hook switch is open and only the ringer or bell is connected across the line. There is no appreciable amount of d.c. in the circuit and only the 20-Hz a.c. ringing signal from the central office can reach the subscriber. C2 provides the a.c. path for the ringing signal.
With the handset off the cradle, or "off-hook," the dialing contact is normally closed and a d.c. connection is made, causing the line relay at the central office to pull in and make the connection. The hybrid coil is part transformer, part balancing and isolating coil, arranged to split the 2wire line electrically so that most of the incoming sound signal goes to the receiver (earphone) and the outgoing sound from the transmitter (microphone) goes to the line. Most transmitters are simple carbon -pile microphones, but some new ones as well as all receivers are electrodynamic devices. To prevent overloading, a varistor VR2 is shunted across the receiver, limiting the average audio output amplitude. Another varistor, VR1, limits current pulses due to the dialing contacts. Varistors change their resistance according to the amount of current flowing through them.
The dial contains a cam and sprocket which opens then
ELECTRONICS WORLD
closes the dial contacts when the dial returns to its station-
ary position. When you dial "1," you turn the dial a short
idanigpsteatrhnioecdenuaonmfdab,beaorssuitt"3r6e,01tu,m2r"nilsilsi,sstehhcoeowncdnosn.itnaTcFhtiseg.apr3uelasonepdetnrthaeiedndofionffrceedreifanolrt-
time periods, which the telephone company central office, are indicated. If the tolerance ceeded, wrong numbers will be reached.
expects at limits are
the
ex-
Another network, ed in the hybrid-coil
not shown assembly,
in Fig. 2 but usually includis the anti-sidetone network
which limits the feedback between receiver and transmit-
fttheehirrmee. nsApechlesfo.minnaeltlhaaem"rloeivcueen"itveosrof,usbindudettobtonyoeamilsloudwcehisnisrgiadbetlhteoebneteaclcakaueusrseetsiotinghiteveaer-sr
Many modern phones contain ringer loudness controls
and a number of additional terminals and other variations
of the basic circuit. Phones are available buttons, extension, intercom, and buzzer
with selective call signaling features.
RTizoeecndeetn"otnldyeiagltihenengetrienalteosporhsmocenoeanrnecaoescm.tepTdahnetyoseahpapshuosihnn-etbrsouhdttauovcnee-dctroa"nnTtsroiosultlcoehrd--
matrix switch and, instead tone signals is used.
of the
d.c.
dial
pulses,
a
series of
What the Phone Company Can Do for You
A subscriber is equipment for his
not legally required to rent phone attachment from the
interface telephone
ppiitcesnhllcoyseeiom.tmran,cpnopobacmouunerptiystcla,eyatnrohlbtueumwttohaacyayfoko.vunrbepToemlwhteqoerousscoipmttomehpanoeeycnntooehebpmcielntcpegyoleeioamtaxsub,ypirsoawuetntoitqhy-thuetfhiwigipemtiusmlorlcoesoeiwtnunotpsnputltratpeoa;lrolc.iiwttntiI,hcneatoerhsltuohscaumseonpruides--t
The 30 from the amplifier
-type voice coupler is used to connect voice -only phone to the subscriber's attachments, such as an or intercom. It is essentially an audio transformer
wastataoaumnnalrbdykdsps"lcataicosrfvopiwiobelmhiiiremotdmrcosnihtrsueu,yntjniashanibtcceethaaekmyltvr.aibc.oonTroinIiccmhdnseeeccoisltoonuryvfiadpsel,tnteruhesdotemtfrhoaipiemnrtwhmsptoi2helelnl-iqerwtehuukicaidlrevvoieeenaeu.pellpeisTtnlondehdeturh.e,.ceait.Wsoavtotoeaphtuareasatconeohvg"tfepitrodhdotrfheeeusvaenstua"wlde-rditinexoiosode----
clusion key," a white button on the cradle of the telephone
lsaYayennotddi,rnkitoshdCneilfliiyfftieytnertsdehttanheultnelpap,ctmiaatorhnontensttcohchhfoelayutrhapgtrelteeeacnricsothaiuasmlnrcoteforounynrnt.ndtbehc$eis2tce0odc.moPtueorpicalteehcrsteivvipseah.r5oyI0nnselcNieglienhnwttes-
eesfpmmbwCftliqueoarAaaeefrnuAwaitnonUcnnsitdretp.tmdt,esireatmo.oSuipsnnsiUctFaenhuashrnoa3p)rtttv,thr,tmphimeecnoletaeyoygornan",nprSndoStetrtoeUfaaUeof3cmuil-Cgf6nah,oteauyAosom(annssmodUpe,takedearla"bmieopattanihextneclecedenerlcdatogdt-ooalehssweaiunuutennnreapebrmgcuydeclsyemiticoas.srsefrnlpybodTiisesrpbseehtteurehentiotclhsrmhtesfoh'eesrfcfteesarnooa.cereveouemoIqatpdtnitbnuihpfloleetyeiaftlrprhofibof,tforesimhlilvucreeeteeSabelhrolUpo,snolsdgcoep6steaiirdletcaciiimmlbcolootwieeenyounnclrdphdesagao'ssoe-t-llr
ooicHsmnnouvzunbAettsdrsthhntocieettunrhioisoaebecpelneoetbpirauraoithpsc.tpnoolksoaenilrrctme.toaafluteblPaolalsaaehtshtsuiueiss1rsrde4eedhh,7atoo5hanomm-vednHaeesizt,tluhoaabtaenbonsldtncedhceroetiitebunhgsaepietslrlntaeytrethtropmhreanetahtetaodSehlrienUasi,vsr3smtise,heceneqenpsd,nudeyisrastdpmnhtemaeaitmtta2eesl1c.ntaot2ttrHenh5mideeseInstallation cost for this coupler is about $11.00 and the
July, 1971
mwichopanhtthoslinymeir-leaanrntsacwlouiesprli$en3rg,.2t5myppaelcuhRsiDtnaeLxsionarnNRdDecwMoY,nutoasrikendiCnfiogtyr .tawAuotsoo-mwmaaety-speech amplifiers, rents for $3.50 plus tax, with an installation charge of $20.50.
In addition to these couplers, AT&T offers
models for different phone attachments and
many other subscriber
connections. Other networks and local phone companies
have similar couplers available. Local business provide details on rental and installation costs.
offices
will
pcohuIofpnyleeorucowwmilalpnaftunrtyon'sisdhceosaiungpdnlewyr,ohuyarot uoitwmwnuilssltyrsketnqeoumwiretow. Thwaaotbrlkseigw1niasthlhsowtthhsee,
(Continued on page 54)
EXCLUSION KEY
CONNECTING ROCK
VOICE CONNECTING ARRANGEMENT VOICE COUPLER
ASSOCIATED TELEPHONE SET NETNORN CONTROL ANO SIGNALING UNIT
- CUSTOMER PROVIDED
PLUG AND CORD
The simple 30 -type voice coupler supplied by phone company.
CUSTOMER - PROVIDED PLUG ANO CARLE
More SU6,
elaborate voice -connecting arrangements, types CAU, are also available at increased rentals from the phone
SU3, and company.
siaAupnselnugtt'taigoshtpsogetdeerTwdamrrneohianncsincomt-oTyrhdeitcacetaenohrrsmreeuapxannatcnietdndonsineshroseniotohcewaneercnerijtvsaeemhcdrerkaer,uekqdniunowiiirgrtrsieetch.acoSautualtonysopmemleReptdaoCatorAiactafhcttcpeeohaheursoepsssnceheteiotco-threaandanleelvryserew,cltioonebsrreuuditnechislhgrte,.-
29
rocs%
Recent
Developments in Electronics
Thirty-Kilowatt U.h.f: TV Klystron Tube. (Top left) We are always impressed with the giant transmitting tubes that are used by our broadcasters. The one shown in our photo is no exception. It is a 30 -kW four-cavity klystron tube that is used for u.h.f. television broadcast transmitters. Engineers are shown adjusting the tube for the exact channel required to minimize adjustments after installation. A family of three of the new klystrons cover the low, middle, and high portions of the u.h.f. TV band. The tubes can be used in either the video or audio power-amplifier stages of the u.h.f. TV transmitter. The tubes are made in the RCA plant in Lancaster, Pa. Price of the new klystrons is $8820 each.
Side-Looking Radar Maps from the Air. (Center) You are looking at an aerial view of the low coastal area around Port Arthur, Texas. This is not an ordinary aerial photograph, however, but it is a picture made by a side-looking radar system. Unlike a photograph, it could have been made in daylight or total darkness, in sunny weather or cloudy. The black areas at the top and bottom are water, while the white specks in the water are ships and offshore oil rigs. The radar system is the same as that used for military intelligence and mapping in Vietnam since 1965. The manufacturer, Goodyear Aerospace Corp., has unveiled the system for possible civilian use in such fields as topographic mapping, geophysics, mineral exploration, oceanography, and agriculture. Transmitting and receiving equipment are carried in a plane that may be flying at extremely high altitudes and at speeds faster than the speed of sound. The radar pulses are sent out to the side. Returning pulses are recorded on data film which subsequently undergoes chemical and optical processing to produce an exact image of the territory surveyed. And because side-looking radar images.a wide swath of terrain on a single flight, thousands of square miles are condensed on one strip of film. The high resolution results from the use of the Doppler frequencies of the pulse returns to improve their along -track or azimuth resolution.
Closed-Circuit TV Monitors Steel Plant. (Below left) No less than 16 closed-circuit TV monitors are being used to keep watch on the progress of steel plate in the heat-treating facilities of a new steel plant in Baytown, Texas. The new line, consisting of a hardening furnace, roller quench, and a tempering furnace, has been designed to ultimately produce heat-treated ship steels and pressure- vessel steel plates up to 12'/z feet wide and up to 5 inches thick. Natural gas is used to fire the heat -treating system, which is controlled through the television monitors from the hardening furnace to the tempering furnace. Ste& plate travels 186 feet through the hardening furnace at temperatures up to 1800 degrees. it is then quenched by water sprays. The quenched plates are then moved into a tempering furnace 244 feet long where they are heated to between 750 and 1350 degrees. After tempering, the plates are allowed to air cool. The new plant is U. S. Steel's Texas Works, which will serve fabricators in the Gulf-Southeast section of the country.
ELECTRONICS WORLD
Scanning Electron Microscope Teamed with Computer. (Top right) A scanning electron microscope (at extreme left in photo) has been teamed with an IBM computer in an experimental configuration that provides immediate chemical analysis of the specimen under observation. The microscope can magnify an object more than 50,000 times compared to about 2000 times for the conventional optical instrument. In this setup, the computer selects the electron scanning beam locations and collects and analyzes observed signal characteristics. Since the computer requires digital information, the analog signals from the microscope must first be converted into this particular form before they are used.
Electronic Thermometer for Hospitals. (Center) The nurse is about to take the temperature of her young patient with a new electronic thermometer. The thermometer accurately records temperatures in only 20 seconds and has a sterile disposable cover. There is no washing, sterilizing, breakage, or shake-down required. The probe uses a thermistor for temperature measurement and the meter readout unit is not much larger than a king-size cigarette package. It operates on two long-life 9 -volt transistor -radio batteries. Price of the unit, made by LaBarge, Inc. of St. Louis, is $140.
Low-Light TV Watches Shoppers. (Below left) The nation's first police-operated low-light -level TV system designed for round -the -clock detection was placed in operation recently in Mount Vernon's (N.Y.) main shopping area. The system consists of two all- weather TV cameras mounted on utility poles. The pickup tubes used are so light sensitive that they can easily detect a man one -half mile away in what looks like almost total darkness to the eye. A wide -range automatic brightness control protects the tubes when the scene is brightly illuminated. The cameras are connected to two monitors at police headquarters via underground cable. They can be remotely controlled from headquarters to rotate, tilt vertically, or zoom in on any suspicious person or object. Ultimately, the system will include a video tape unit that will record all incidents "seen" by the cameras over a 24 -hour period. GTE Sylvania made the installation, which covers 1000 feet of the town's main business street.
Electronic Ignition Switch Foils Drunks. (Below right) When you get into your car a few years from now, a random number may flash on a small display screen. You get three chances to repeat that number. You should have no trouble doing it, provided you are not too drunk to drive. If you are successful, you can then press the Start button and start the car. At least this is the idea behind the latest configuration of Delco's Phystester ignition -interlock system. Scientific evaluation is now underway and 50 of the units have been available to the National Highway Traffic Safety Administration for evaluation in government vehicles. Now all we have to do is make sure the car starts when we press the button on a cold or damp day.
July, 1971
Zener Diode
Voltage-Regulator Nomograms
POWER SUPPLY . EPS(SR)
R
J EPS(NL)
- - ---- VOLTAGE REGULATOR
ER(SERIES)- w-1 RS
=T
ER(LOADJ
i
J
IL-------J
Fig.1. Basic circuit diagram of the zener-diode regulator.
áÉS s=ò,
VOLTAGE [DROP
`
,,
Fig.2. This voltage-regulator design nomogram is used to determine percentage regulation of zener supply voltage.
Fig.3. The second voltage -regulator design nomogram is used to determine the parameters of the series limiting resistor.
32
_OAO RL
vJaGE VO S,
R-_Cs sSI-sL-Y0ACE
Editor's Note: Although some of the nomograms shown in the following article are used to solve some fairly simple calculations, they do serve to demonstrate the use of nomograms in design work. In most cases, nomograms serve to speed up tedious, time -consuming calculations simply by the user placing a straightedge over the scales of the chart.
-HE silicon zener diode -is the work-
horse of solid -state voltage regulators and simple circuits like that of Fig. 1 are easy to design. Although the regulating action is similar to that of the
VR tube, zeners are quite tempera-
ture-sensitive so additional calculations are necessary. Four design nomograms
have been developed that will help_
make regulator design fairly routine. Any voltage-regulator design begins
with the load requirements and determination of the voltage variations to be supplied to the regulator from the basic power supply. The nomogram of Fig. 2 shows how the regulation of the supply can be determined. First the no-load voltage is determined analytically or measured. Then a dummy load can be placed across it equal to the full load and the new voltage measured. Regulation is determined by the inter-
nal resistance drop and can be ex-
pressed by the equation:
R- EPS(NL)- EPS(FL) x loo
EPS(FL)
where: R is percentage regulation,
EPS(NL) is output voltage of power supply with no load, EPS(FL) is output voltage of power supply with full load, and:
EPS(NL)- EPS(FL) = EPS(IR)
where: Eps(IR) is voltage drop across the internal resistance of the power supply. These three voltage are shown in Fig. 1 to the left.
The first three scales on the left of Fig. 2 determine the numerator of the first equation and the "Z" scales on the right use the numerator to calculate the regulation.
For example, if an unregulated supply furnishes 15 volts under no -load condition and 12 volts under full dummy load, we have a 3 -volt internal resistance drop. If we draw a line between the 3-volt point to the right to a 12 -volt point on the fifth scale, we cross the Regulation scale at 25 %.
ELECTRONICS WORLD
By CHESTER W. YOUNG
Four design charts that can be used to simplify selection of components for a solid-state voltage-regulator circuit.
The second nomogram (Fig. 3) takes the next step and starts with the power-supply full-load voltage. This is cornbined with the current requirements of the load and the zener to determine the series limiting resistor value. The three scales to the left determine the
voltage drop involved and the "Z" scales on the right determine the re-
quired resistance. Two equations are:
ER(aeriea) = EPS(FL) -ER (load) where: ER(.,.iee). is voltage across seriesdropping resistor, EPS(FL) is voltage out-
put of the power supply under full
load, ER(load)is voltage to be maintained across the load by zener diode and:
Raeriee = ER(series) / I where: Raer;es is required resistance of the series-dropping resistor and I is the total current to be drawn under regulating conditions.
For example, if we assume that we have been designing for a load that requires 10 volts at 20 milliamperes, we
enter the nomogram on the second
scale at 12 volts (our power supply full load voltage) and connect a line to the first scale at the required 10-volt point. Extending this line to the third scale on
our right we determine the voltage
drop across the resistor to be 2 volts. The "Z" chart on the right helps determine the resistance value if the load current (20 mA) and the zener current (usually 10% of required load current, 2 mA) are known. In this case the total would be 22 mA drawn through the
dropping resistor. A line extending
from the 2 -volt point (3rd scale) to the far-right scale passing through the 22-
mA point of the middle "Z" scale
would intersect at 91 ohms. This solves the fraction 2/0.022.
The selection of the series resistor is .
determined by the resistance valuejust calculated and the maximum current to be drawn through it. The nomogram in Fig. 4 determines the power (center
scale) from either of the formulas:
W= EI or W= PR, where W is power (in watts) dissipated in either resistor or zener diode, E is volts across resistor or zener, and I is current through resistor or zener.
For example, we have just deter-
mined the series-resistor value to be 91 ohms so we enter this on the second scale from the left. We also know the total load and zener current is 22 mA.
This value is entered on the second
scale from the right (P) at 22 mA. Joining these two points with the solid line,
(Continued on page 75)
July, 1971
VOL (VOLTS)
oo
R
RESISTANCE (OHMS)
(000
50
500
20
200
IO
5
W
POWER ( WATTS)
loo 50
20 io
-- 2
(=2)
CURRENT
AI
300
S CURRENT
(mA)
1000
soo 200
200 i00
50
2
20
10
5 5
20
001
.2
2
0005
2
0002
.0001 Fig.4. The third design nomogram is employed to find the power requirements of the series resistor and zener diode.
Fig.5. This fourth nomogram is used to relate the various zener-diode parameters in order to provide circuit trade-offs.
-
33
Designing
a Phase-Shift
Oscillator
By JON L. TURINO
Simple, step-by-step design technique that can be used to produce this versatile sine -wave audio oscillator.
THE phase-shift oscillator has been around a long time. It is a versatile circuit which has a number of applications
other than its main use as a sine -wave source in the audio frequency range.
For the experimenter, however, there is usually one drawback to incorporating the phase -shift oscillator in a
project-how do you design one that will work and oscillate
at the frequency you need? Circuit designers use a long, mathematically complex
procedure when they design a phase-shift oscillator; and then have the circuit built and tested to determine the actual parts values and to evaluate its performance. Many use an additional sophisticated technique unavailable to most of
us-computer aided design (CAD).
The phase-shift oscillator design procedure presented here is a simple, straightforward, step-by -step method for obtaining a circuit that will work when power is applied to it. The frequency of oscillation will be within five percent of the calculated value, and the d.c. stability of the circuit is entirely adequate if a low- leakage silicon transistor is used as the active element. The approximate frequency range of
Fig. 1. Schematic of general type phase -shift oscillator circuit. vcc
RL
ii
34
this phase-shift oscillator circuit is from 20 Hz to around 50
kHz. Fig. 1 is the schematic of the general circuit and the de-
sign procedure used to determine the parts values is listed in the box. Since the main stumbling block is in the first step, a little time is devoted to determining how to specify RL if the oscillator is to drive an amplifier or emitter- follower stage, as is usually the case.
Fig. 2 shows two typical transistor stages that might be used to isolate the oscillator from the actual load so that variations in the load will not affect the frequency or output amplitude. The input impedance of the emitter- follower stage (Fig. 2A) is actually the load resistance for the oscillator. Its value can be closely approximated using the formula R,n= (RBX ORE) /(RB +ßRE) where ß (beta) is the forward current gain of the transistor, usually called lofe. For the stage in Fig. 2A, this value is 25k ohms.
Determining the Input resistance of the amplifier stage in Fig. 2B is slightly more complex. The effects of both RBI and RB2 must be taken into account, since they are actually in parallel with the transistor input. The formula for finding R;n for the circuit of Fig. 2B is R;n =1 I (1 / RBl) + (11 RB2) +
(11 ORE).
Once the load resistance has been determined, the rest is easy. Let's do an actual e+cample. Suppose we need 10 volts r.m.s. at 5000 Hz and the emitter-follower of Fig 2A is used for isolation. Referring to step 1 of the design procedure, specify RL as 25k ohms and 28 V p-p across it (p -p is 2.8 times r.m.s.). The power supply (tie,) must be 1.4 times 28 V, or about 40 volts. Now set collector resistor R, to 0.2RLor
5000 ohms.
For the stage to operate properly, the collector current
must allow about one -half the supply voltage to be dropped
across R, . Using the formula of step 4, 4 will equal 40 /2>< 5000 or 4 mA. Now another composite parameter is needed. The a.c. signal from this oscillator sees both R, and RL in
parallel as a resistance, RL e.,.. From the formula in step 5,
RL ac. = 4100 In order to
ohms. sustain
oscillation
in
this
circuit,
the
voltage
gain of the circuit must equal the loss through the phase-
shift network. This loss can be mathematically reduced to a
constant-37. Adding an eight percent "fudge factor" to
this gives us the number 40. The voltage gain in the circuit
of Fig. 1 is approximately equal to the ratio of the a.c. col -
ELECTRONICS WORLD
lector resistance (RL a.c.) to the emitter resistor, RE, so this relationship can be used to calculate the value of RE. In our example, 100 ohms is the closest standard -value resistor that will work properly.
Now a suitable transistor must be selected. First, it must be of a low- leakage silicon type. Second, it must have a beta (hra) of at least 50 at the frequency at which we want the circuit to oscillate. Third, it must have a power dissipation of at least 40 V x 0.004 amp or 160 mW. One other important parameter is the collector-to-emitter breakdown voltage. It must be at least equal to the supply voltage, and preferably 50% higher. For our application, the 2N930 will work. Its beta is typically 100 all the way to 10 MHz, its power dissipation 300 mW, and its breakdown voltage a minimum of 50 V.
Using /3=100, calculate the base current, 'B, at 0.04 mA. The formula in step 9 derives an Rbb (total) of 490k ohms. The nearest standard value of Rbb, and Rbb2 (from steps 10 and 11) are 100k ohms and 390k ohms, respectively. Now bypass the a.c. signal that would be fed from the collector to the base using this bias method so that it does not reduce the gain of the circuit. Cb is the bypass capacitor and its reactance should be less than or equal to 1000 ohms (Rbbl/ 100, step 12) at 5000 Hz. A 0.033 -1F capacitor does the job effectively.
Now the R;n for the oscillator stage must be determined. This value is found using the same formula used for the emitter-follower input resistance, with Rbbl substituted for
RB (step 13): R;= (100k X100 X100) /(100k+100 X 100)
or 10k ohms. The value for the two "R" resistors in the circuit are now known.
In order for the circuit to oscillate, the signal applied to the base must be 180° out -of-phase with the collector signal. Since we have three legs in our phase-shift network, each should provide 60° of phase shift. This occurs when the capacitive reactance (Xe) of the capacitors is 1.732 times the
resistance of the "R" resistors. Therefore, Xc must be
17.32k ohms at 5000 Hz. Using the formula C =1 /27/Xe, the value 0.0018 µF is derived and the design is complete. Fig. 3 shows the complete circuit, with parts values assigned. When breadboarded, it provided 30 volts p-p output at 4900 Hz, very close to what was specified.
The frequency of oscillation can be trimmed to an exact figure by adjusting the value of either "R" resistor. The phase -shift oscillator provides a signal suitable for use as a code-practice oscillator, a fixed-frequency audio-signal generator for testing amplifiers and other audio equipment, and, with minor modifications, an active bandpass filter. It can even be used to generate the sound of bongo drums by making RE large enough so that the circuit gain is just below the point where oscillations begin. If a trigger is ap-
(A)
(B)
Fig. 2. Schematic diagrams of (A) simple emitter follower
and (B) more complex circuit that might be used
to isolate the phase-shift oscillator from actual load.
0 +40V
.033 390k
50k 5k 100k
.0018
2N930
100
.0018
500
10k
.0018
10k
Fig. 3. The complete schematic diagram of the phaseshift oscillator circuit constructed by the author showing the values of all of the various components used.
plied to the base of the transistor, the circuit will be shocked into oscillations which will quickly die away.
(Three such circuits at low, medium, and high frequencies, will create the sounds of a bass drum, a tom-tom, and a bongo drum, respectively.)
The same gain-reducing technique (raising the value of RE) allows the circuit to become an active bandpass filter, an application the author has incorporated into a five -channel stereo color organ.
DESIGN PROCEDURE
1. Specify RL and p-p volts required across RL 2. Specify Vee at 1.4 X p-p volts across RL
9. Calculate Rbb(total, where Rbb(total)
(Voe /2) -VBE _ßRE
IB
3. Set Re approximately equal to 0.2 RL 4. Calculate le, where le= Vee/2Re
10. Set Rbb1 =0.2 Rbb(total) 11. Set Rbb2 =0.8 Rbb (total)
5. Calculate RL where RL a.e.= (RLXRe) /(RL+ Re)
6. Set RE= RL a c /40
7. Select transistor with beta greater than 50 and power dissipation greater than VeeX le
8. Calculate IB, where IB =1e /ß
12. Set Cb so that its /Cc< Rbb1 /100
/n= 13. Set "R " =R;n, where R;
(Rbb]XßRE) / (Rbbl +NRE)
14. Set the Xc of "C" equal to 1.732R 15. Calculate the required value of "C" from
its Xc at the desired frequency
July. 1971
35
Technicians in Britain
In the U.K. Technician Engineers are Thp s
By E.A. BROMFIELD /Secretary
The Institution of Electrical and Electronics Technician Engineers
A recent authoritative survey has revealed that over one million technician engineers and technicians will be required by 1975. The United Kingdom is now laying the basis for their professional recognition.
IN the United Kingdom, most professional engineers of all
disciplines are members of the Council of Engineering Institutions (CEI) and are referred to as "chartered." Until recently it has been possible to become a chartered engineer based on past experience but without having a-professional degree. This is being changed and all chartered engineers of the future will have to be'degreed engineers.
The Technician Engineer
In view of this, it has become necessary to set up a separate title for engineers without degrees whose qualifications, training, and experience nonetheless entitle them to be called engineers. In fact, these men outnumber chartered engineers by a ratio of 4:1. The generic designation "technician" would not be suitable since it is used as indiscriminately as the generic "engineer." The widespread acceptance of the title "technician engineer," however, (from the Continental concept ingénier technicien) shows that it has provided the long-sought compromise. This term is used by all engineering disciplines, government departments, educational establishments, industry, and by the Council of Engineering Institutions.
In all sectors of electrical and electronic engineering, technician engineers are expert in the application of specif-
ic engineering techniques-whether in manufacturing, op-
erations, maintenance, or research and development work. These non -chartered engineers carry out a wide variety of
specialized activities wherever electricity is used as a
means of power, control, and communication. Technician engineers provide the detailed information from which engineering decisions are made and influence the selection of materials and apparatus. They obtain their academic quali-
fications-HNC (Higher National Certificate) or CGL[ (Full
Technological Certificate of the City and Guilds of London
Institute)-by part-time day courses with technical college
attendance once a week, or by block-release and evenings only courses. (Block -release is an arrangement whereby employers send young employees to technical colleges for a period of several weeks at a time, while still paying their
wages.)
With their good, near-degree academic attainment, allied to specialist training and experience, electrical and electronics technician engineers have a distinct identity and status. For them, career prospects have never been better than they are today because more and more of them are needed to occupy "kingpin" positions in every branch of industry as well as in a managerial /supervisory role.
The Technician
The technician, also in short supply (particularly in the
36
electronics field) requires similar technical knowledge and
skills, although not quite so high, but still substantial. Many
technicians reaching the requisite technical educational
and experience levels develop into good technician engi-
neers.
A research report by the Engineering Industry Training
Board published on December 8, 1970, gives added empha-
sis to the distinction between technicians and technician
engineers. The difference "lies less in the actual activities of
the two than in the technician engineer's greater breadth
of knowledge and wider range of activities, backed by a
higher level of attainment in further education."
In 1967, following a request by the Government, the Na-
tional Advisory Council on Education and Commerce set
up a committee under the chairmanship of Dr. H.L. Hasle-
grave (a former vice -chancellor of the Loughborough Uni-
versity of Technology) to review the provision of courses
suitable for ing grades
technicians at all in non -technical
levels-including
occupations-and
correspondto consider
what changes should be made in the present structure of
courses and examinations. The Haslegrave Committee,
whose report appeared in December, 1969, concluded that
the present complex pattern should be replaced by a sim-
ple, two-tier system of certificates and diplomas, and that
national certificates and CGLI awards should be gradually
phased out. They recommended that a Technician Educa-
tion tion
Council Council
be for
ensotnab-tleischhendi-caallofniegldsw-ittoh
a Business Educaplan and regulate
the new structure, with the CGLI acting as the administer-
ing body to serve the two Councils.
There has been a widespread support within engineering
circles to setting up an Engineers Registration Board and just at press time we have been advised that such a board
has been set up under the aegis of the CEI (Council of Engineering Institutions). This Board will register all three categories: Chartered Engineer, Technician Engineer, and
Technician. It is intended that titles and designatory initials shall be awarded under protective powers derived from the
CEI's Royal Charter. It is believed that such a comprehensive, authoritative system of registration will improve the standing of the entire U.K. engineering profession and in-
dustry, will dissipate the existing confusion over qualifications and titles, and will help to encourage more young
men to seek a career in engineering.
(Editor's Note: Information about technician engineering careers in Britain's electrical and electronics fields can be obtained from the author, 2 Savoy Hill, London WC2R, OBS, England.)
ELECTRONICS WORLD
Measuring Color-TV Generated
X -Rays
By J. G. ELLO /Radiation Measurements & Instrumentation Industrial Hygiene & Safety Div., Argonne National Lab.
The end -window (left) and the thin -wall Geiger- Muller (right) tube survey meters used by the author to detect the level of x- radiation emitted from TV sets.
Types of survey instruments, comparative characteristics, and methods of checking color-TV receivers for excessive radiation.
HE television receiver is a principal source of home entertainment and information but, like many other products, has its share of undesirable by- products. The automobile, steel mills, and power stations pollute the atmosphere with their noxious exhaust gases while television receivers emit an unwanted by- product called x- radiation. Recognized since the black-and -white television receiver came into being in 1946, x-radiation has become more of a problem since the advent of larger picture tubes requiring higher voltages. In an effort to limit x- radiation levels, present television receivers are designed under the guidelines recommended by Underwriters' Laboratories and the National Council on Radiation Protection and Measurements. With the use of present-day radiation detection and measuring equipment, the author feels confident that TV-receiver manufacturers have reduced x- radiation to safe levels. Nevertheless, once the receiver leaves the factory, x-radiation levels may be altered if controls are improperly adjusted. Color-TV receiver x-radiation, or x-rays as they are sometimes called, is only one source of radiation exposure with which the average consumer may come in contact. Other sources include: medical and dental x -rays, earthen materials used in building our homes, the sun, and in certain instances industrial equipment on the job. The Radiation Control Act of January, 1970 was passed to provide the TV viewers with as much protection from TVproduced x-rays as possible. Standard levels set back in the 1950's, stipulating that x-ray emission from TV receivers must not exceed 0.5 milliroentgen per hour measured at about 2 inches from all outside surfaces of the TV receiver at the time of purchase, are now in effect. (A milliroentgen is sub-multiple of the roentgen and is equal to one onethousandth of a roentgen. The roentgen is a quantity of xor gamma radiation that will produce one electrostatic unit of ions in one cubic centimeter of air.)
X-rays Reviewed
TV x -rays are produced mainly by the picture tube
(CRT), rectifier, and high- voltage regulator tubes. Before we go any further, a brief review of what x -rays are and how they are produced is in order.
In 1895, a German physicist, W. C. Roentgen, discovered penetrating rays, which he called x -rays, while experimenting with the luminescence produced by cathode rays (electron emission from a cathode). Unlike nuclear alpha and
July, 1971
beta radiation, x -rays are not affected by electrical or magnetic fields. When x -rays pass through air or a gas, the air or gas has the ability to conduct electricity, that is, x-rays produce electrically charged atoms (ions). They can also stimulate or disintegrate living tissues. Opaque materials, such as cardboard, wood, or books, that block visible (light) waves are transparent to x-rays. It is the ability of x-rays to affect the sensitive emulsion of photographic film that makes it ideal for use in the medical field. We could say x -rays are of the same nature as light, but with a shorter wavelength.
A basic x -ray generating circuit, in which the x-ray tube functions as its own rectifier, is shown in Fig. 2. The secondary winding of transformer T 1 furnishes the filament current for x-ray tube XT and transformer T2 furnishes the necessary high-voltage potential between the electrodes (cathode and anode). Once the x -ray tube is energized, its cathode will release electrons, causing the electron stream ES (cathode ray) to accelerate at very high speeds to the anode. It is the impact of the swiftly moving electron stream on the anode that produces the x -rays (secondary
emission). Similarly, x-rays of various energies (intensities) can be
produced by electron tubes which are capable of accelerating electrons to energies of several thousand electron volts (eV). The higher the voltage across the electrodes of the x -ray producing tube, the higher the x -ray intensities and the greater the penetration. Potentials at, say, 100,000 volts across the tube electrodes will produce x -rays with penetrating power that would show the bones of the hand while lower potentials, about 10,000 to 40,000 volts, produce lower energy rays, referred to as soft x -rays. Soft x-rays are easily absorbed by matter and have energies below 50,000 electron volts (50 keV). Consequently, any electron tube with the potential of accelerating electrons to energies of several thousand electron volts can produce x-rays.
TV X-rays
Color-television receivers have been known to emit x-ray levels in excess of 0.5 milliroentgen per hour (0.5 mR /hr). It was also found that the amount of x-rays radiated from color-TV receivers is related to the input a.c. line voltage. For example, a five-volt increase in line voltage is capable of increasing the x-ray level by a factor of two. As mentioned earlier, the CRT is one of the main sources of x -rays from color-TV receivers. Here the primary x-rays emanate from the CRT's faceplate. In shunt -regulator tubes, x -rays are
37
generated at the anode and in high-voltage rectifiers at the cathode (due to the reverse cycle of the sweep cycle). This occurs when the d.c. high voltage is applied across the rectifier in a reversed direction; the anode is at negative high voltage. The x-rays from the CRT's faceplate are absorbed somewhat by the picture tube's glass panel and on more recent color -TV CRT's by the steel shadow mask. X -rays from the rectifier and shunt-regulator tubes are absorbed by the glass envelope and the steel tube shields.
The x-rays that bypass the absorbers are of various energies, ranging from approximately 10,000 to 35,000 eV. Appropriate radiological survey instruments are required to detect and measure these x -rays. Some of these may cost thousands of dollars, such as the pulse-height spectrometer, or hundreds of dollars, such as battery -powered survey meters. Fortunately, the technique for identifying the TV xray spectrum is known and simpler radiological survey meters may be used to monitor color-TV receivers.
Since the theory behind the operation of survey meters can be found in a number of texts, we will confine our discussion to how a survey meter can be used to spot x-rays from color-TV receivers and which type is best for the job.
TV X-ray Energies
To determine what x-ray energies are emitted from color-TV receivers, studies were conducted by taking readings from specially adjusted color -TV receivers, using a pulse height scintillation spectrometer. It was found that if a 25inch rectangular color picture tube were operated above the recommended voltage, the over-all x-ray energy spectrum emanating from the TV receiver would be between 10 and 31 keV. The tests showed that from the face of the picture tube, x -ray energies would range from approximately 19 to 25 keV with a peak at about 24 keV. The x -ray energy range from the shunt regulator was about 10 to 25 keV with peaks at 12.7 and 24 keV and the high-voltage rectifier produced x-ray energies from about 10 to 31 keV with a peak at about 26 keV. As the high voltage increased or decreased, so did the x -rays emitted from the TV receiver. For example, when the high voltage was raised above the recommended selling the measurable amount of x -rays increased.
Measurable x -rays emanating from a color -TV set can range up to about 31 keV. Of these, the lower energy x-rays are easily absorbed by matter such as cardboard, while other energies pass through. This is similar to a light beam passing through a couple of sheets of tissue paper, which absorbs a certain portion of the light. Therefore, when measuring or detecting x -rays emanating from TV recevers, it should be kept in mind that the material from which the detector is constructed will also absorb some of the x-
rays. Since x-rays emanating from color-TV receivers are of
Fig. 1. (Left) Eberline Instrument Corporation's scintillation type and (right) Victoree Company's ionization chamber are two other survey meters used to detect x-rays from TV sets.
various energy levels, an ideal detector would be one that has a flat response to the whole energy spectrum. Unfortunately, no such detector is readily available, but there are a number of detectors which are susceptive to soft x -rays and with proper calibration against a known x-ray source (which is in agreement with the National Bureau of Standards), can be used for detecting TV's soft x -rays.
X-ray Detectors
The lead photo shows an end -window and a thin -wall Geiger -Muller (GM) tube survey meter. The end -window GM tube (at the left) consists of a very thin mica window approximately 1.4 milligrams lcm2 thick and with an active area approximately 1$/8" in diameter. The other GM tube consists of a very thin aluminum cylinder approximately 30 milligrams / cm2 thick and with an active area 23/4" long. The energy response of these two types of GM tubes is poor for determining a dose rate. The data sheet on the thin -wall GM tube (1B85) shows it to be sensitive down to about 10 keV while the end-window GM tube fares a little better. One reason for a poor response is that the detection of soft x-rays (uncharged particles) requires the production of secondary electrons. Secondary electrons produced by the soft x -ray interactions are easily absorbed directly by the GM tube counting gas. The efficiency of such GM tubes depends on how many x -rays are absorbed by the GM tube and also how many secondary electrons reach the interior of the detector. Accurate calibration may be difficult because of these complications, including the energy and path of the secondary electrons. The GM -tube survey meter may be used as a "go /no-go" instrument for localizing beams that are emanating from color -TV receivers, such as those from the shunt and high-voltage rectifier tubes. They also will give an indication if excessive amounts are emanating from the picture -tube face.
Survey meters associated with the two types of GM tubes shown in the lead photo have three linear ranges, from 0 to 50 mRlhr. The readout consists of 0-50 microammeter and a phone jack for aural monitoring. The meters are powered by two carbon "D" cells with a battery life of about 300 hours.
Two other types of instruments that can be used for detecting TV x-rays are shown in Fig.. 1 with the scintillation type on the left and the ionization chamber on the right. The scintillation detector has come into its own in the last decade although scintillation is not new. It is one of the oldest methods of detecting nuclear radiation through the process of scintillation in a phosphorous material. With im-
provements in photomultiplier tubes, the scintillator gained wide acceptance. The scintillation detector contains
a photomultiplier tube and a NaI (Tl) crystal (sodium-iodide activated with thallium). Such a scintillator detector would respond to all low- energy x -rays were it not for its protective screen and opaque Mylar window, which absorbs the very-low- energy x-rays. Other limitations on low-energy sensitivity is the natural background from gamma and cosmic rays and from the thermionic current noise within the photomultiplier tube and its associated circuits. The energy response of the scintillator is well within the color-TV x-ray emission range. With its protective screen removed, x-rays down to 3 keV can be detected above the natural background. The small active area of the scintillator is ideal for detecting narrow x-rays beams from TV sets.
The survey meter used with the scintillator detector is a battery-powered pulse-count-rate meter with single-channel, pulse- height analyzer capability. It has three separate channels with high -voltage adjustments. The survey meter readout consists of a dual scale and pointers. The meter indicates counts per minute and, with proper calibration, the counts can be converted into mR/hr readings. Battery life is approximately 350 hours when mercury cells are
used.
ELECTRONICS WORLD
The other type detector, is an ionization chamber. The ionization chamber is widely used in dose-rate survey meters and is calibrated to read directly in mR /hr. Most battery- operated ionization survey meters consist of vacuum tube electrometers. For increased sensitivity, a vibrating reed electrometer is used as in the ionization meter shown. Ionization chambers are versatile in that all types of nuclear radiation which produces either primary or secondary ionization within the chamber may be detected. They may also be constructed in various shapes. Many chambers which have a very thin Mylar window are sensitive down to about 4 keV depending, of course, on the detector design and its counting circuit. Energies below 4 keV are easily attenuated by the chamber walls and therefore cannot penetrate it. Data that is available on the ionization survey meter shows a relatively flat response down to about 6 keV, which is well within the range of x -rays emanating from malfunctioning color -TV receivers. The ionization survey meter is battery powered utilizing 4 carbon "D" cells with a life expectancy of approximately 100 hours. It has a range from 0 to 300 mR /hr and is calibrated to read directly in mR /hr.
Radiographic X-ray Film
There are other ways of detecting x -rays. One is by means of radiographic medical x -ray film. Radiographic
film is widely used for monitoring personnel working with or near ionizing radiation. This same principle has been applied to monitoring color-TV sets for x-ray emission. The film has proven useful in detecting narrow x -ray beams produced by shunt -regulator and high -voltage rectifier tubes. The film may be packaged in various sizes and the package may contain one or more types of film.
The film consists of an emulsion containing silver-iodide or silver- bromide crystals imbedded in a gelatin mix which is spread on a base support. The film is then packaged in an opaque material. Absorption of low-energy x-rays is a problem, therefore film sensitivity depends both on the packaging material and the size crystal used. The film can be made sensitive down to the 6-keV x-ray energy range. Unlike the other types of detectors mentioned previously, the film needs no electronics for its ionization process. The xray's interaction with the emulsion compound causes the release and trapping of electrons. The trapped electrons in the crystals cause a darkening of the film during the developing process. The film response, or darkening, is proportional to the intensity of the x-rays; that is, the greater the intensity, the darker the film will get. After developing, the film is viewed by a densitometer. Readings from the densitometer are then converted into mR/hr readings. To monitor a TV receiver, a film packet is attached to each side of the TV receiver. After a proper time exposure, the film is developed for dark clouding or images that indicate x -ray exposure.
To sum up, at present there is no all- around survey meter for TV x-ray monitoring. Calibration of the survey meter must be known. Conversion to an mR /hr reading must be certain and the accuracy of the low -level reading in the 0.5 mR /hr range must be dependable. Sensitive detectors such as the GM detectors in the lead photo and the scintillation detector which are energy- dependent, are quite capable of detecting low- energy x -rays providing the energy in question is known. They are useful in detecting small x -ray beams such as those produced by the shunt-regulator and high-voltage rectifier tubes. The ionization survey meter is not suitable for beam measurements. This is because of the large area of the ionization chamber. However, it is suitable for measuring x -rays emanating from the face of the TV picture tube. In the author's opinion, an ionization-type survey meter with interchangeable ionization chambers accurately calibrated in mR /hr would be an ideal TV-monitoring survey meter. The scintillation detector would come
July, 1971
S.C.
0000
TI
lJ
T2
Fig. 2. Basic x -ray tube (XT) circuit showing how x -rays are
produced when accelerating electron stream (ES) strikes anode.
START SCAN
SCANNING SPEED -2 "/s WIDTH -2"/SCAN
1
2
2
Fig. 3. Diagram showing method used by the author for scanning TV receiver for x -rays. Meter should be held no more than 2" from all cabinet surfaces while maintaining scanning width of 2" /scan and a scanning speed of approximately 2 " /s.
second only because it is very sensitive and therefore
affected by natural background radiation. Monitoring with radiographic x -ray film, in the author's opinion, is too slow for home use.
TV X -ray Surveying Color-television receivers are designed to limit x-radiation below the maximum value stated in the Radiation Control Act of January, 1970. If for some reason a TV receiver is suspected of emitting x -rays above the maximum level, it should be surveyed. Although as this article is being written
there is no standardized procedure for TV surveys, the following technique was used by the author.
Preferably, the survey should be conducted during the daylight hours when the a.c. line voltage is highest. The choice of survey meters will depend on the surveyor's ability and knowledge of radiation -detection technology. The author has used both GM and scintillation- survey meters to survey for small x -ray beams and the ionization-type survey meter for broad area beams such as those which might be
(Continued on page 55)
39
EMC 212
TRANSISTOR TESTERS for
Leader LTC -902
6&K 162 Po
Williams AO.
T HERE is certainly no mystique involved in testing transistors any more. Technicians and engineers know you can check for good or bad transistors with a simple ohmmeter, if the internal voltage or current is not too high. Lately, makers of volt-ohm-milliammeters have reduced ohmmeter voltages, and several have special low -power resistance ranges, so that they won't damage transistor or diode junctions.
But you might want to know if two transistors have the same beta, for use in push -pull. Or, you might want to pick one with low leakage for some critical circuit. There are a good many reasons you might need a quantitative evaluation.
That's when you need a transistor tester. There is a wide range of choices. Our recent survey for the accompanying chart turned up over twenty different models for the service technician; at least six are new this year. We know of two more that will be introduced soon.
The testers available fall into five categories: (1) inexpensive type, (2) general type, (3) automatic type, (4) lab type, and (5) curve tracer (use with scope).
Low Cost and Quick
Even within this category, instruments vary considerably. The simplest model tests only /cop (collector-to-emitter leakage current with base open) and makes a beta test of sorts. The diagram of Fig. lA shows the basic test setup that is used.
For this p-n -p transistor, negative voltage goes to collector and positive to emitter. That reverse-biases the collec-
tor and emitter junction. Any current that flows is IcEo
leakage. A small- signal transistor should hardly wiggle a 0 -3 mA meter at all. A power transistor could show normal /cEo up to quarter-scale. More than that means the transistor is
defective-with excessive leakage or shorted. No reading
means the transistor may be open. To see if the transistor amplifies, you close the Gain
switch. A resistor applies negative voltage to forward -bias the base-emitter junction. If the transistor is okay, collector current jumps upward. The meter should read considerably more than it did with the base open. If not, the transistor is faulty.
40
This kind of evaluation is "go /no -go" testing. You make no accurate gain measurement. Also, the test voltage for leakage may be much less (or more) than what's needed by the transistor you want to test. That creates some inaccuracies. Yet, at low cost, these testers are acceptable. Two models that work this way are the Heath IT -27 and the RCA WC -506A.
The EMC212 makes a simple IcEO test and a check of d.c. beta. Then you can plug a transistor into the socket and test its performance as an oscillator. If it works, the signal generated can then be employed for signal-injection troubleshooting.
The Simpson 650 permits reasonably accurate d.c. beta readings. The 650 is an adapter that fits on the Simpson 260 v.o.m. Precision resistors, plus switches and adjustment pots, calibrate the tester for beta readings up to 250. The only leakage reading is /CEO.
Testing /CEO instead of ICBo (collector -to -base leakage with emitter open) would be okay except that ICBo usually tells more about how well most transistors will operate. Acceptable /CEO and "relative gain" readings may camouflage a transistor that won't function well because of too much /Cap. Some testers omit the /CEO reading; their designers consider IcBo the more important test.
More Time, Accuracy, Cost
Several instruments test for both /ego and /CEO, and measure beta with somewhat more accuracy. We've labeled these "general" -type models. Some do other tests, too
The Heath Model IT -18, for example, measures both kinds of leakage. The test for /ego of an n -p -n transistor is shown in Fig. 1B. (For a p-n -p the battery and meter are reversed.) The base -collector junction is reverse -biased. Any current that flows is leakage. A few microamps is all that's allowable. As a rule of thumb: for r.f. transistors, no more than 5 µA; low-power transistors, no more than 50 µA; power -output transistors, up to 1 mA.
The d.c. beta test in general-type instruments is simple, but it's calibrated so you get a better idea of how well a transistor can amplify. The test arrangement in Fig. IC is typical, although some may have several additional ranges and scales.
ELECTRONICS WORLD
y Heath IT-18
Lectrolech TT-25C
SERVICING
By FOREST H. BELT
A survey of what is available to the service technician for checking leakage currents, amplification, and displaying characteristic curves of transistors, FET's, and diodes.
ASimpson 650
There are two steps. First, you push switch Si to the Cal (calibrate) position. That puts the meter into the collector circuit across R2 and applies bias to the base through Rl and R3. You adjust bias with the knob of R3 until the meter reads a specific amount of collector current. For example, suppose this calibration Ic is 5 mA.
As the second step you push Si back to the Read position (labeled Beta on some instruments). Rl becomes part of the collector circuit. The meter switches to the base circuit.
The meter measures how much base current is flowing. If the scale is marked in microamps, you can figure out beta. Roughly speaking, beta is the ratio of collector current to base current. Suppose that, with 5 mA of collector current, a particular transistor shows base current of 25 µA (0.025 mA). Collector current of 5 mA divided by base current of 0.025 mA equals beta of 200.
To make it easier, the meter scale is marked in beta. This approximation of true a.c. beta is dependable only if the test voltages fit the particular transistor and its operating
conditions.
Some instruments provide extra test ranges. The Heath IT-18 has two. So does the Lectrotech TT-250. The RCA WT -501A has five different operating levels for measuring beta; that improves the accuracy of the reading.
The Leader LTC -902 tests /CEO and two ranges of d.c. beta. It also generates a high-harmonic 1 -kHz tone for sig-
nal injection. An internal amplifier, with gain of 90 dB, makes a good a.f. signal tracer. As in several instruments, metering functions are accessible separately: 0 -50 mA and 0 -20 volts, in this model. This and virtually all other units
measure diode leakage. Several instruments measure beta the a.c. way. The Sen-
core TF17 and TF151, the B&K 162, and the Eico 685 are examples in the general category. Several models in other categories also measure a.c. beta.
It's interesting to note that the B&K, Eico, and Sencore instruments also measure transconductance (GM) of field -effect transistors (FET's). That's similar in many ways to a.c. beta. GM of a FET is a ratio worked out by dividing signal current in the drain circuit by signal voltage at the gate. The result is in mhos (reciprocal of ohms), or more accurately in micromhos (µmhos).
July, 1971
You find a.c. beta in bipolar transistors by dividing collector signal current by base signal current. If you did it the complicated way, you'd figure out currents from voltages across resistors in the collector and base circuits (no ordinary instrument measures signal currents directly). Then you'd calculate beta. With a tester, you set up switches and controls and the meter shows you a.c. beta already calculated.
These B&K, Eico, and Sencore models are the "upper class" of general-type transistor testers. They all check leakage in both bipolar and field-effect transistors. The Sencore units measure only I0BO in bipolars, but measure both IGSS (gate-to-source leakage with drain shorted to source) and Inss (zero-bias drain current) in FET's.
The B&K 162 performs a whole gamut of bipolar and FET measurements. In addition to Icß( and /CEO tests, it measures collector -to- emitter leakage with the base shorted to emitter (IcEs) This reading should be lower than the /CEO reading, but not as low as the kw) reading. The 162 also checks both IGSS and Inss in FET's.
The Eico 685 makes all three leakage tests for bipolars and both leakage tests on FET's. In addition, there is a pinchoff test for FET's. You apply 5 volts between drain and source, then turn up a control that applies pinchoff
- F!!g. 1. (A) Basic test circuit for IcEO (collector -to-emitter
leakage current with base open), and-by closing the switch
aaggeaicnurerveanltuawtiitohn.em(Bi)ttTeersot pfoern)I.CRE(e)v(ecroslelebciatosr
-to is
-base used.
leakNote
that "n -p-n" transistor is shown here while "p-n -p" is shown
in (A). (C) The simple test for d.c. beta requires two steps.
(A)
(B)
(C) 41
Fig. 2. Collector-voltage /current characteristics of transistor under different biases are displayed simultaneously on scope screen by curve tracer. (Left) Normal family of curves for an n -p -n transistor. (Right) A "signature pattern" of a transistor that is being checked out in a circuit.
to the gate. When current stops, the voltage control knob tells you the pinchoff value. (You use the same variable voltage to determine where a zener diode breaks over or an
SCR fires.)
Another general unit is the Sencore F1155. It's special in that it tests only FET's. The unit makes all the FET tests the other Sencore units make, plus gate-2 tests on dual-gate FET's.
Automatic Testing
A couple of operations to test a transistor-or three or
four, if you count leakage tests-isn't much work. But the
new Hy-Tronix tester, made by a division of Vanguard Tool Mfg. Co., takes even that chore out of in- circuit testing. There are five colored lights on the meter scale.
The in-circuit test is quick. You flip the function switch for Visual or Sound indication, Xstr test. Then you make connections to the foil side of the printed board with a special probe. If the transistor is good, the two top lights or the two bottom lights start blinking. A label between the two blinking lights tell you the polarity of the transistor.
If there's a short or excess leakage, different lights start blinking. Labels between whichever lights blink will tell you which elements in the transistor are shorted.
If you set the Function switch for Sound, and the transis-
tor is okay, a Sonalert beeper sounds off each time the
"Good NPN" or "Good PNP" lights flash. If the transistor is bad, you hear nothing. The idea is that you can go through a bunch of transistors on a printed board without looking up from your work.
Out-of-circuit tests are similar to those by other testers. You measure /CEO or /CEO. You can check beta with base current at 20 µA, 200 µA, or 2 mA, depending on whether the transistor is an r.f. type, low-power type, or a high -power type. The lights aren't involved.
"Lab" Testers
These instruments are for testing individual transistors, usually out-of-circuit. We've tagged them "lab types" be-
cparouascehthoepytipmruomvidfeoroepaecrhatitnragnsciostnodri-taiotnsletahsat tfcolrosseolmyeapo-f
the tests. Simplest is the Heath IM -36. There are knobs for collec-
tor voltage, collector current, base voltage, base current, and leakage voltage. If you're testing transistors that need more voltage or current than the instrument supplies, you can connect an external voltage supply to binding posts on the panel. With the right combination of switch and control settings, you can test leakage between any two elements and measure d.c. beta under many different voltage and current conditions.
Similar advantages are obtained with the Hickok Model 890A. Test voltage and current for the collector are variable over a small range. You can test IcBO and measure a.c. beta with a 1 -kHz oscillator (more realistic than a 60 -Hz a.c. beta test). You can test transistors in circuit or out.
The Hickok Model 870 is the most elaborate and versatile tester on the chart, and the most expensive. It has a roll
42
chart with data on over 1000 transistors. If your cross- reference books are up to date, you can test new types too.
The 870 lets you test beta by a.c. or d.c. methods. The a.c. beta measurement is at 1 kHz, and transistor operating voltage and current are variable. You can test IIBo with a variable test voltage. You can run operating curves to determine saturation point, and check just about any other transistor parameter you care about. The instrument has
voltages to suit almost any transistor-low power or high,
ordinary or switching type.
Curve Tracers
These are fairly new to the transistor -testing scene, at least insofar as inexpensive instruments for the service technician are concerned. Only two curve tracers are avail-
able as this is written, but others are expected shortly.
There is some controversy about their usefulness for serv-
icing. True, they are more elaborate than is necessary to
spot a shorted or open transistor. But, for that matter, so are
mtooustsetraannsoisstcoilrlotsecsotepres.wDitehtrtahcetocrusrvoebjtercatcebre-ctawusoe
you have pieces of
equipment instead of one. Many technicians insist transistors don't "get weak" like
tubes do; they're either good or bad. Evidence proves oth-
erwise for some kinds of transistors in some applications.
Heat changes operating curves; so does age in some in-
stances. You can spot such variances only if you see whole
operating curves. A curve tracer and scope display a "family" of operating
curves for the transistor being tested -see Fig. 2 (left). Each
curve is the Ic-Vc characteristic of the transistor. It is made by "sweeping" the collector voltage while keeping a cer-
tain value of base current (bias). The family of curves is developed by stairstep changes of
bias. Each change of bias makes another curve. A different family can be displayed if you change the average (center) collector voltage. In an elaborate curve tracer, then, you can pick whatever collector "center" voltage and whatever
set of bias stairsteps suit a particular transistor. The Eico 443 lets you measure beta, IcEO, inverse break-
down voltage, and several other parameters. You must know the calibration of your scope, but the 443 has calibration voltages built in. A collector-current switch lets you display two families of three curves each: one family for
signal transistors and another for power types. The Williams Model A provides for testing at eight dif-
ferent collector "center" voltages. The increment between stairsteps of base current is also variable. You can set the switch to make the curves 10 µA, 20 µA, 50 µA, 100 µA, 200 µA, 500 µA, or 1 mA apart. You can learn to read beta, spot leakage, test for breakdown levels, and so on. You must calibrate your scope, but that isn't too hard to do; most scopes have their own calibration system built right in.
Once a typical family of curves is available for every transistor type, the instrument will be more useful. It can also
be used for SCR's, zener diodes, FET's, and ordinary
diodes. But you must become familiar with what patterns
are normal. One TV manufacturer, Sylvania, has begun adding in-
circuit "signature patterns" to service data for transistors in TV receivers. An example is shown in Fig. 2 (right). Once setmakers or service -lit publishers add transistor curve data to schematics, the curve tracer can be a more valuable aid. You just go through the set (with power off) touching the special three-prong probe to each transistor at the foil connections. Compare the curves you get with the pattern specified for that transistor in that circuit, and you can spot
any significant variations. The special transistor-testing probe we've mentioned is a
product originated by B&K. The Model FP-3 probe has three tips or prods of needle-point steel. Each prod is independently mounted in a spring- loaded ball-socket. And
ELECTRONICS WORLD
they're made in unequal lengths. The longest is for the collector connection, the middle length for emitter, and the shortest for base.
Here's how you use the probe. Locate the E, C, and B connections on the foil side of the printed board. Push the needle tip of the collector prod into the C connection. Then, keeping pressure so that the tip doesn't slip off, rotate the body of the probe until the emitter tip is over the E
connection; push downward until it makes contact. Keep-
ing that pressure applied, again move the probe body
around until the base tip is over its connection. Push down-
ward some more and all through resin protection
t-harneedcwointnheoctnieonhsaanrde.
made -even
You can use the probe with just about any tester listed in
the chart. It is included with the B&K 162 and the Wil-
liams curve tracer.
-ANSISTOR TESTERS
MFGR.
MODEL
ICSO
BIPOLAR TESTS
cE o
ICES
BETA
FET TESTS
WHAT
ELSE
loss
I,s_
IT
PRICE
G,
IN CKT. OUT-SKr.
TESTS
SIR-KIT)
COMMENTS
RA K EICO
162
0 -IA
0 -IA
0-IA
a.c.
0 -1A
O IA
O 50,000
y,
1 -5000
680
0 -0.5A
0 -0.5A
-
d.c.
-
-
-
yes
2 -300
685
0 -5mA
0 -5mA
0-5mA
a.c.
0 -5mA
0 -50mA
0- 50,000
yes
2 -1Q000
EMC
212
0 -80mA
-
-
HEATH
IM36
0-150 0-15aA
-
IT -18
0-15mA
0-5mA
-
IT27
-
0 -3mA
-
HICKOK
870
0-10mA
yes
-
SOSA
0-500
-
_
Ay TRONIX
U -100mA 0 -100mA
-
LEADER
L C I -952
-
0- 50reA
-
LECTROTECR
TT-250
0 -5mA
-
-
RCA
WT-501A
0 -1000
0 -1A
-
WC-506A
-
relative
-
SENCORE SIMPSON
TF17 TF151 TR115 FT155
650
0-5mA
yes
-.
0-5mA
yes
-
-
0 -50mA
-
-
-
-
-
0 -104A
-
d.c.
-
-
0 -200
d.c.
-
-
0-400
d.c.
-
-
0 -1000
d.c.
-
-
relative
ac.
-
-
I -600
d.c.
0-300
a -c.
-
_
0-200
d.c.
-
-
0 -500
d.c.
-
-
0 -200
d.c.
-
-
0 -500
d.c.
-
-
1-1000
d.c.
.-
-
relative
-
yes
-
-
-
yes
-
-
-
-
-
yes
-
yes
-
-
yes
-
yes
-
-
ac. I -500
0 -5mA
0-50mA
0- 50,000
yes
a.c.
0 -5mA
0 -50mA
0- 50,000
yes
1 -500
d.c.
-
-
-
-
relative
-
0 -2001JA
0 -50mA
0- 50,000
-
d.c.
-
-
-
-
Il -25II
yes
dinde, SCR,
LUT, triac
yes
diode
yes
diode, zener,
SCR, UJT,
triac
yes
diode
yes
diode
yes
diode
yes
diode
yes
-
yes
yes
diode
yes
diode
ye-
-
Yee
diode
pas
diode
yes
diode, zener,
var. cap. diode
yes
diode, zener,
var. cap. diode
yes
-
yee
-
yes
-
100
35(K) 55
100(K) 150
Can be used as v.o.m. Can be used as v.e.m.
15(K) 22
62(K) 93
25(K) 7(K)
Voltmeter0 -12V; milliammeter 0 -BOmA; tests oscillation
Portable case
425
Testsa.c. beta at
1000 Hz; roll chart built-in
235
Measures B -E input res. &imp.;
portable; a.c. beta tested at 1000 I.:
287
Audible& light display;
Model 103 probe $15 extra
100
Works also as injector & tracer
90
b/
18
110 130 25 95
44
Attaches to Model 2600.o.rn.
CURVE TRACERS
MFGR. FICO
MODEL
-
-
WILLIAMS
te,o
ICES
yes
-
yes
-
BETA yes
OTHER TESTS
NO. OF CURVES DISPLAYED
V TI6A11,
3
BVCeor
yes
0VCEO;
6
VCE(SAT)
COLLECTOR VOLTAGES
10V @ 12mA 10V @ IA
cont. vartableo -00V
W8 AT ELSE IT TESTS
diode, tener SOR, PET
diode, tener, SCR, FET
PRICE SIK -KIT)
I! li
COMMENTS
Has own caspa calibrator
.,.
y,1831 43
rrr i f/,nSFxv
I
Be Cool:
- Cook With a
MICROWAVE OVEN
By WILLIAM STOCKLIN /Editor
You can cook a frozen TV dinner in 31/2 minutes or bake a potato in 4 minutes with the new Heath GD-29 microwave oven.
BUILDING electronic kits, particularly for the first few times, is quite a satisfying experience. But if you're
looking for a change, as we were, then why not build the new Heath microwave oven? There isn't a printed-circuit
board in the entire assembly and, except for an avalanche
diode, the few lock assembly.
solid-state The kit is
devices are in the pre -built inter-
basically mechanical-you have a
few switches and lamps; a relay, electrolytic capacitor and
transformer; and a lot of sheet-metal parts to put together.
Anyone can build it, and the odds are that it will work the
first time. It took us 10 hours but the average time should
be 10-15 hours.
Microwave ovens are not new. The original idea was a spin -off from microwave technology utilizing magnetron design concepts, resonant cavities, and waveguide technology from radar development laboratories. The first commercial designs came out around 1947 and were used in
restaurants (shortly thereafter, in vending machines too). Chances are that many who have eaten out or done much
flying recently have tasted food cooked by microwaves. It wasn't until a few years ago, though, that engineering
know -how was able to develop an oven for the consumer market that featured compact size, operated off standard 120 -V, 15-ampere house power lines, and could be offered
for under $500. (Now, of course, we even have kits.) Microwave ovens do cook as fast as they claim. You can
boil eight ounces of water in two minutes, bake a potato in four minutes, and prepare an average beef roast in 15 minutes (5 min /lb). Frozen food can be defrosted in minutes, too (2-3 min /lb) for spur-of-the-moment meals. These ovens are ideal for vegetables, fish, and stew-meat, too, but they
do not prepare all foods equally as well. Pie crusts and
browning of meats, for example, would best be done in conventional gas or electric ovens.
The Microwave Spectrum
The microwave spectrum ranges from 500-10,000 MHz, falling between the u.h.f. TV and infrared bands. For the most part, these frequencies are used for radar and microwave communications. There are two exceptions, howev-
er -the 915 MHz and 2450 MHz channels allocated for in-
dustrial, scientific, and medical use. These are the operating frequencies for microwave ovens and industrial systems for food-processing, wood -drying, and other purposes. The 915 and 2450 MHz bands are ideal for microwave cooking;
at lower frequencies food is heated more slowly, and at higher frequencies the food surface is heated too quickly.
The Heath oven operates at 2450 MHz, using a Litton5201 magnetron producing 650 watts minimum r.f. output
power. Power is fed into a length of S -band waveguide measuring 3.40 x 1.25 in. in cross-section, and then to the oven cavity. A "mode- stirrer" (fan) distributes energy throughout the oven.
One of the problems with microwaves is that they are easily reflected so that it is not advisable to use an empty oven or metal pans which are reflective and may cause overheating. As a precautionary measure in the Heath design, power is turned off when temperatures become excessive due to no -load operation, fan-motor failure, or even a dirty filter.
There are two areas of major concern to the microwave oven designer: (1) radiation leakage, and (2) finding a fool-
Fig. 1. Wiring diagram of Heath GD -29 microwave oven. The door interlock and magnetron/waveguide are supplied assembled.
r MAGNETRON
NI T
LA
120V AC. 1!A
44
POWfR- iLMR. STlRTER A
STIRRER
LA
MOTOR YOTOR
LiÑP
OOO MR P
ELECTRONICS WORLD
proof method of eliminating the possibility of the magnetron operating while the door is open.
Minimizing Microwave Radiation
Effective July 1, 1971, the new standard of the Radiologi-
cal Health Bureau, U. S. Department of Health, Education
& Welfare (HEW) restricts microwave radiation from ovens
at the point of manufacture to 1 mW / cm2 at a distance of 5
cm. Actually, no one knows precisely what the danger level
is, but HEW will insist that this standard be met as a safety
precaution. Microwave radiation is non-ionizing-as are in-
frared rays, radio
tion-and they do
waves, and not produce
other low- frequency radiairreversible damage. There-
fore, there is no cumulative effect. This differs considerably from x-radiation which destroys tissue that cannot be re-
paired; x-rays are ionizing radiation and their effects are cumulative.
We measured radiation from the Heath oven with a Narda Model 8200 radiation survey meter. This new instrument should find wide acceptance as the standard measur-
ing device for microwave ovens in service shops across the country. It is a much lower-priced version of its Model 8100; both give the same results. In checking all possible
points of radiation from the Heath oven, the maximum we found was the ridiculously low figure of 0.2 mW /cm2. This
was far below what we had thought possible.
HEW has also set what might be termed a "use" standard
for microwave ovens. They should never radiate more than
5 mW /cm2 at 5 cm in their entire lifetime. It is this figure that field technicians should abide by; if radiation ever goes beyond this point, protective measures should be taken.
It is important that the builder of this kit pay particular attention to the assembly of the conductive-vinyl door seals, and care should be taken not to scratch the Teflon -coated capacitive seal plate inside the door. Any scratch on this coating may cause arcing and permit leakage.
Other Safety Features
For obvious reasons, all power to the magnetron must be off prior to opening the door. The oven incorporates two interlock switches for this purpose. When a.c. power is applied between lugs 1 and 4 of the interlock assembly (Fig. 1), it is applied across the SCR through the interlock solenoid. However, the SCR will not conduct until it is triggered by a small positive voltage on the gate (G). This is supplied from a voltage divider consisting of Rl and R2 (through lugs 2 and 5) when the door handle switch is depressed. The a.c. voltage is rectified by Dl. The SCR then conducts, energizing the interlock solenoid and releasing the door lock. At the same time, the interlock switch contacts are open; this, in turn, opens -the circuits to the mag-
netron. (Diode D2 is used to short out reverse voltage
surges that might be developing across the solenoid.) When the oven door is opened, the door interlock switch
is mechanically actuated to further disable the magnetron circuit. The system is foolproof. (A rather interesting situation could occur, however, in the event of electric power failure while the oven is in use. It would then be impossible for the door to be opened until power was restored.)
Heating Phenomenon
The microwave interaction is produced by what can be
called "molecular friction." Molecules forth orient themselves with the electric
moving back and field, causing heat,
but the degree of temperature rise depends on the type of
molecule. (Some move too slowly.) Water is an ideal medi-
um for microwave heating since it has both a high dielec-
tric constant and high loss. It is the basis of microwave cook-
ing, in fact. All foods cooked this way must contain water.
For this reason, paper plates, glass, or crockery containers
absorb little energy and are heated only indirectly by the
food they contain.
July, 1971
The magnetron and waveguide come pre-assembled and are
mounted on oven with 25 nuts and bolts. Magnetron is a Litton L-5201 producing a minimum of 650 watts r.f. output.
With microwave cooking, not only is cooking time drastically cut, but so is dish-washing time. Food can be cooked in
glass, ceramic, or even paper plates, and served on the same dish. Anyone using the microwave oven for the first
time might as well forget all he has learned about conventional gas or electric ovens. Microwave cooking is an entirely new phenomenon and is gaining in popularity as the modern approach to home -cooking.
For those interested in building their own microwave
radiation tester, the U. S. Dept. of Health, Education &
Welfare recently issued a booklet, `Inexpensive Read-
out for a Commercial Thermocouple Microwave Power Density Probe" (BRH/DEP 70-31, PB 192-377), which completely describes construction of such a unit including circuit diagrams and mechanical assembly details. The design is based on the use of Narda's Model 8122 probe and the cost is estimated at about $50 for the parts plus $150 for the probe. For a copy of the booklet, send $3.00 to National Technical Information
Service, Springfield, Virginia 22151. The radiation tester we used (as described in the arti-
cle) is Narda's Model 8200, which is available at $295 including probe and carrying case. For further details, see item in "New Products" Department.
Inside door, showing vinyl seal on outer edge and the Teflon-
coated capacitive seal. This Teflon seal overlaps an area of
the oven front panel when the door is in the closed position.
The contact width of this area is equal to Y. wavelength of the
fundamental
cavity sees
frequency a parallel
of 2450 MHz. The energy in the transmission line 3/4- wavelength
oven long
which is terminated ed line appears as a
in an open -circuit. short circuit at its
Such an open- circuit input end, effectively
shorting the oven front panel to the door. The Teflon coating
maintains a uniform separation between the door and oven
front panel, acting as a dielectric between the two capacitor
plates, forming the transmission line. This Teflon prevents
arcing between the capacitive seal plate and oven front panel.
CONDUCTIVE -VINYL DOOR SEAL
CON -A;T
WIC TO
CAPnC TI'/E
GEwL
'ENEL
.
TEF_ON MATING
e..
OVEN CAVITY
0
45
The
Optoelectronic
Revolution
By LOTHAR STERN and IRW N CARROLL Semiconductor P'_ducts Div.. Motorola Iic.
Long-lived and low-power solid-state devices are starting to invade the fields presently served by incandescent lamps and glow-discharge display tubes. Used as light sources, light modulators, indicators, displays, detectors, couplers, and sensing arrays, here's what's available now and future prospects.
This 7-segment sol yd -state readout is a custom hybrid unit with
4 the decoder-driver IC chip (top) mounted in the same package.
FOR some time, two technologies have been moving along separate but gradually intersecting paths. Now
that their courses are destined to meet, this could produce
aanwdaveelecotfronnewicsaapnpdlicthateiornesl.atTivheelytwnoewtecthenromlo-goiepstoaerleecotprtoincsics- coined to describe this merger, has captured the atten-
tion and fired the imagination of scientists, engineers, technicians, and experimenters.
The field of optoelectronics deals mainly with the twin phenomena of converting light into electric current and, conversely, turning an electric current into light. Neither of these is new. The phototube and the solid -state cadmium sulphide photocell are early and successful examples of light detectors while tungsten- filament and gas -filled bulbs
Fig. 1. Relative response of silicon photodetector compared to
wavelength of light output produced by various light -emitters.
1.1
TYPICAL SILICON
1.0
Ira RESPONSE
-0.9
RESPONSE
MI UM --_, 0.8
-_,- illirGaP
- 0.7
_''(GREEN)
0.6
GaA 0.62P0.38
GaA
,--Ì2 0.5
GED)
1.0
0.4 0.3 0.2 0.1
glaì!l1IJI-0.8
0.6
II
0.4 0.2
0
03
04
05 0.560.6 0.660.7
0
I
WAVELENGTH (MICRONS)
46
have been serving as light sources for many years. But all of these components have limitations that restrict their use to rather mundane applications. Only the relatively recent development and mass production of silicon photodetectors and light-emitting semiconductor diodes, combined with large-scale integration of their required electronic circuitry, have lifted these restraints. Today, although the actual utilization of these new optoelectronic devices is still minimal, the variety of optoelectronic products in mass production is large enough to move the technology from experimentation to implementation. Moreover, there exists a custom-product capability so that the only limitation on applications will be the imagination of the equipment design engineer.
Light-Emitting Diodes
In electronic equipment, incandescent and neon lamps will soon have strong competition from light -emitting (semi- conductor) diodes (LED's) in applications ranging from indicators to displays. And the reasons are obvious.
For a start, the response of LED's is many times faster than that of previous devices. While incandescent lamps work very well at d.c. and respond even in the low audiofrequencye range, LED's can faithfully follow frequencies well into the megahertz region. Also, solid -state devices are much less fragile than their glass counterparts. Finally, their anticipated lifetime is far greater. While the life of an average incandescent indicator bulb may reach 5000 hours and that of an average neon lamp could extend to 10,000 hours, it is estimated that the life expectancy of an LED is on the order of 20 to 30 years. (Some special incandescent
ELECTRONICS WORLD
and neon lamps have life expectancies as great as ten times the previous fig-
ures.-Editor) In addition, high -volume
manufacturing techniques are expected to quickly establish price levels for
solid -state devices that are competitive
w o 20 k
10 k
á 5k >
2k
iuriimiiiñ .1=ii _IIII.
iii=1=iiiiiñi NNr.
_1MLED600)!-
SPATL -L RESPONSE
0D 100
RELATIVE RADIANT FLUX
with today's well -established and mass-
1k
'T
produced incandescent lamps.
500
Most of today's light- emitting diodes
211C
are either made of gallium arsenide,
1oc-
which produces infrared radiation (ap-
proximately 9000 angstroms) when the
diode is forward biased, or of gallium
arsenide phosphide which produces a
visible red light of about 6600 ang-
stroms. Both are being manufactured
in quantity and both have specific ap-
plications. The visible-light diodes are
designed to be used as panel lights, cir-
cuit-condition indicators, light modula-
tors, displays, and the like. Infrared
emitters are recommended for card
and tape readers, for shaft and position encoders, and for other applications
Fig. 2. The power or light output of two typical LED's for various forward currents. Also shown are four spatial responses available.
where photodetectors can take the place of the human eye. Since the infrared wavelength of gallium arsenide coincides with the optimum response for silicon detectors, this pro-
rent, hence greater light output. Moreover, the shape of the package determines spatial radiation distribution (Fig.
2).
vides a system of optimum efficiency (Fig. 1). Although the variety of light emitters is limited at the
present time, engineers are using packaging variations to broaden the scope of their application. Each of the various packages may house the same emitter chip, but the shape and materials used in the package determine device char-
acteristics -and its price.
One inherent characteristic of light-emitting diodes is the linear change of light intensity with current. The limiting current value is set by the power dissipation capability of the package in which the die is housed. Thus, an efficient heat -dissipation package permits operation at higher cur-
From a materials standpoint there are three different
package types: plastic, metal, and ceramic. The metal packages are generally hermetically sealed and have a lower thermal resistance than the plastic units. Thus, they are suitable for use over a higher temperature range and can be operated at a higher maximum current. As a result, they can produce a brighter light output. On the other hand, the plastic-packaged devices are considerably less expensive
and are usually preferred in commercial, industrial, and consumer applications. Ceramic packages are currently being used for readouts of the seven-segment type.
But this is only the start of differences. Of the two Moto-
Inside the LED
Of all the light generated in an LED, only a small fraction actually reaches the outside world. There are two basic factors that account for most of these losses: the low transparency of the LED material to the wavelength being emitted and the high index of refraction of the LED material.
A few of the possible paths that the generated light can take are shown in the illustration. The longer the path through the material, the greater will be the absorption of the light. As can be seen, light leaves the junction in all directions. The gold backing used for bonding reflects light emitted towards the back of the die adding somewhat to the forward-emission radiation.
The "bending" of the light being emitted is due to the high index of refraction of gallium arsenide phosphide as is the light being reflected from the inside surface back into the die. If the light strikes the surface at an angle greater than the critical angle e, it will be reflected back into the die.
The critical angle can be increased by placing the die in a material which has an intermediate index of refraction such as epoxy or plastic. Additional shaping of the plastic can also enhance the radiation characteristics.
Even when the generated light strikes the surface in an ideal manner, perpendicular to the internal surface (normal incidence), a certain portion of the radiation is reflected back into the die. This is due to the reflection coefficient which is also a function of the index of refraction.
The reflection coefficient can be reduced by coating the surface of the die with a transparent material that has an intermediate index of refraction. The thickness of this coating should be an odd number of quarter wavelengths of the emitted light
as measured in the intermediate material. A common material
is Si02, while SiO or Si3N4 is also being used. A combination of die -coating and encapsulation in an inter-
mediate material can improve bare -chip efficiency by a factor of 2 or more. In addition, using a red plastic encapsulation that will pass the emitted radiation improves viewing contrast.
.2 UNCTION REG nN WHERE LIGHT IE GENERATED
FCES,IR: ADCATD:vcL-'vGIh_E°x,'
OF
G-csp-p..g .=
LEGEND:
1 . Directly emitted ray from top surface 2. Internally reflected ray from top surface 3. Specularly reflected ray leaving top surface 4. Diffusely reflected ray 5. Ray leaving side of chip 6. Ray with normal incidence with dotted line showing ef-
fects of reflection coefficient 7. Ray striking top surface at critical angle Bc, and emer-
ging ray parallel to surface.
July, 1971
47
Monolithic 5 x 7 alphanumeric GaAsP light- emitting diode array.
CASE Zia
CASE 1T1t2I
CASE 6IA MUSMAWATORE)
CASE S.
CASE Ae
Spal.IReraomm
PLASTIC
A
C
HERMETICALLY SEALED
A
6
A
Max OL.Cumm
AI Wmmiength
Visible Light
I6ú00 %)
Intrered
m oaio
40 80
MUD 50
FILED 60 MLE090
50 80
MUD 6011
WED 907
75 150
WED 610
MMES 910
75
-
WED OM -
-
150
-
OLEO 930
Fig. 3. Some currently available light -emitting diode packages, together with some of their important operating characteristics.
DIODES
LOWUENSITY TRANSISTONS
NIGN-0ENSTY TRANSISTORS
DARLINGTON AMPLIFIER
¡
III
'
/s4)
Pckegr
MEW
WIN
Plastic
Plmk
WW
Plastic
A I
p
A
O
A®anM
O3
13 002-01 01-08
02
DutpullMinl
yA/mW/Imz
mA/mW/em
B
N
A
Da
Oa-015
mAimW/pn
B
10-A g0 mA/mWbe=
WitchingTime Aanga
m 1.0
5-11.Oya M.
AEA Mn
a00vs Ma:
Fig. 4. istors,
Silicon photodetectors Darlington amplifiers.
are available as Typical specs
diodes, transare indicated.
Fig. 5. (Top) Combined counter- latch-decoder-driver and 7 -segment readout. (Bottom) Circuitry needed for 5 X 7 dot matrix.
2
Erable
Clock
Strobe 14
Lamp Test
13
Drivers
10a
11b
Decade Cou ntei
4 bit Latch
7- Segnen Decoder
90
f'
5d
4e e d
6f
Reset
as Crags
0- Lines
Al
A20-
A30-
A4 AS
0O---
AS O--
A70-
12 Se Pal
Output
Address Decode
Memory Matrix (2240 Bits)
48
Lamp
Aim 3
131
Direct Column Select
bbóbb
Cl C2 C3 C4 C5
Column -
Select Lines
7g
VCC=Pin 16
Gnd = Pin f
Oper.Ended Output Buffers
b
Chip Enable
-O 131 -O --0 82
B3
-O 84 -O 85
--0 136 --0 B7
Cl C3 C5
CO
C4
rola packages, it would appear that the primary difference is one of size. This, however, accounts for some rather star-
tling variations in spatial response-and in subsequent ap-
plications. In the small package, the chip is near the center of the curved dome so that emission of light radiated at an angle is at a maximum. Hence, the angle of visibility is quite wide, making these devices suitable as pilot lights, fault -indicators, and in other wide-angle -visibility applications. In the larger package, the die is mounted some distance from the dome. This results in internal reflections that produce a rather narrow beam. Visibility is therefore limited to a relatively narrow angle, although the output is less diffused and appears brighter. This type of unit is better suited for "directional" applications such as modulators, tuning indicators, optical data links, and the like.
Similar considerations apply to metal -cased units so that careful evaluation of the unit's spatial emission characteristics is recommended before making a final selection (Fig.
3).
Photodetectors
The susceptibility of semiconductor -device characteristics to impinging light has been known since the earliest days of the technology. Indeed, the variations in leakage current in glass-packaged diodes, due to changes in light levels, was a nuisance that was corrected only at considerable extra expense. Yet, it is this phenomenon that is being exploited for light- sensing purposes and today's semiconductor photodetectors are designed to optimize this effect.
Silicon photodetectors are widely available in three electrical configurations: diodes, transistors, and Darlington amplifiers. Each successive variation produces an improvement in sensitivity, but at the expense of speed (Fig. 4).
The different characteristics of these variations make them suitable for different applications. The photodiodes, with their extremely fast (nanosecond) response, are ideal for laser detection as well as for ultra -high-speed demodulation, switching, and decoding. Their low current (microamps) output, however, makes subsequent amplification
necessary.
Phototransistors, on the other hand, have respectable outputs in the mA region, but their switching times are measured in microseconds. Accordingly, they are more suitable for industrial inspection, processing, and control systems. To increase their versatility, such devices are available in miniature as well as subminiature packages, the latter being recommended for tape and card reading, character recognition, and other applications requiring high density mounting.
Finally, the photo Darlington transistors have outputs high enough to act as industrial drivers, but speeds that are limited to several hundred microseconds.
The Impact of LSI
The explosive growth of solid -state optoelectronics is greatly enhanced by maturing large-scale integration (LSI) capabilities. Not only from a size standpoint, but from power-supply requirements as well, both technologies are entirely compatible. It is this compatibility that provides new potentials for widespread implementation. For example, the mere replacement of an incandescent or neon -lamp ricmeoanpdcooorumttaniwtcaienthttoraewlsiaoablridirla-itsnyttatiaemnupenrqoituviempmmigeenhnttstn, roest-pdabeceseiogrfend.suuBfcfutiictoitenhnset, and cost advantages could provide an ample incentive.
A case in point is the combined counter-latch-decoderdriver circuit (Fig. 5) which, in conjunction with a hybrid type LED readout, provides this kind of advantage. Moreover, an integrated-circuit chip can be placed in the same pagaeckdaiggeit.wSiuthchthdeevriecaedsohuatvfeorbeaefnulplyroodpuecreadti,vbeu, tsianrgelen-optaycke-t generally available.
ELECTRONICS WORLD
NEW IR -18M solid -state 12-speed chart recorder kit
r .....n..
NEW IB-101 solid -state 15 MHz frequency
counter kit
u
r
NEW GR -371MX 25" square- corner solid -state color TV kit
icmtiss
s
NEW GD-29 microwave oven kit
NEW IB -102 175 MHz solid -state frequency scaler kit
NEW 10 -102 solid -state 5" scope kit
NEW IM -105 solid -state VOM kit
Seven new Heathkit ®improvement ideas for home or shop
N EW! Heathkit 1R-18M 10" chart recorder kit provides 12 different
chart speeds...instant pushbutton selection from 5 sec /in. to 200 min /in. Digital logic delivers accuracy unobtainable with ordinary gear trains. Two input ranges permit accurate measurements from 0 -1 & 0 -10 mV full scale. Hi -Z input minimizes loading. 3- terminal floating input. Light-operated modulator eliminates problems of a mechanical chopper...operates at 240 Hz to reduce 60 Hz noise. Internal temperature -stabilized reference voltage eliminates troublesome reference battery. Coarse & Fine zero controls allow fast, accurate pen positioning. Other features: versatile pen holder that accepts virtually any writing instrument & hinged top for easy paper loading. For the best value going in a chart recorder, order your IR-18M now. Kit IR -18M, 15 lbs., 149.95*
N EW ! GR -371 MX 25" solid-state ultra- rectangular color TV. Check
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ture ever...high resolution circuitry plus adjustable video peaking
...Automatic Fine Tuning...pushbutton channel advance..."Instant-
On "...Automatic Chroma Control...factory assembled 3 -stage solid -
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marginal conditions...adjustable noise limiting & gated AGC...ad-
justable tone control... hi-fi sound output to internal speaker or your
hi -fi system. Plus your choice of installation in one of the three
beautiful Heath cabinets or custom wall mounting capability. And
the exclusive Heath self- service features let you do all normal ad-
justment & servicing, saving hundreds of dollars in service costs. If
you want the finest, this is it...order your 371MX now. Kit GR- 371MX,
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N EW! GD-29 microwave oven...the most modern way to prepare
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399.95*
Roll- around cart gives oven easy mobility, Model GDA-29-1, 24.95*
NEW ! IB-102 Scaler and IB -101 Frequency Counter combination
give you frequency measurement capability to 175 MHz at low, low cost. IB-101 counts from 1 Hz to over 15 MHz. Hz/kHz ranges & overrange indicator let you make an 8 -digit measurement down to the
last Hz in seconds. 5 -digit cold-cathode readout...extremely low in-
put triggering...all solid -state with 26 ICs, 8 transistors. NEW IB-102
Frequency Scaler can be used with virtually any counter on the
market to extend your measurement capability well into the VHF
range...at a price far below the cost of a 175 MHz counter. 10:1 and
100:1 scaling ratios give resolution down to 10 Hz...1:1 ratio provides
- straight-thru counting for frequencies in range of counter. Exclusive
Heath input circuit triggers at very low levels at 100 MHz less than
30 mV is needed. A handy Test switch gives a quick, accurate check
of proper operation. All solid- state; fully regulated supplies; conven-
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capability now with these two new kits. Kit IB-101, 7 lbs.....199.95*
Kit IB-102, 7 lbs.
99.95*
N EW! 10 -102 solid -state 5" scope ideally suited for general purpose
service & design work. Features wide DC -5 MHz response, 30 mV /cm sensitivity and 80 ns rise time. Switch -selected AC or DC coupling for greater versatility. Frequency-compensated 3- position attenuator. FET input provides hi-Z to minimize circuit loading. Recurrent, automatic-sync type sweep provides five ranges from 10 Hz to 500 kHz with vernier. External horizontal and sync inputs are also provided. One volt P-P output provides an accurate comparison voltage source. Additional features include a big 5" CRT with high visibility trace; 6x10 cm ruled graticule that can be replaced with a standard camera mount; solid-state zener-regulated supplies for extra display stability and 120/240 VAC operation. An excellent all-around scope that belongs on your bench now. Kit 10 -102, 29 lbs., 119.95*
NEW ! 1M-105 solid -state portable VOM...an extremely rugged, high-
ly accurate, low cost meter for hundreds of applications. High impact Lexan® case and ruggedized diode & fuse protected taut -band meter movement will suffer extreme abuse and still maintain specifications. 95° wide viewing area provides high resolution. 3% DC accuracy; 4% AC accuracy; 3% DC current accuracy. Temperature compensated. 8 DCV ranges from 0.25 to 5000 V full scale 7 ACV ranges from 2.5 to 5000 V full scale...6 DC current ranges from 0.05
mA to 10 A full scale...5 ohms ranges from xl to x10k with center scale factor of 20...5 dB ranges from -10 to +50 dB. Other features
include DC polarity reversal switch; front panel thumbwheel ohms zero; self- storing handle and fast, easy assembly. A lot of meter at a little cost...that's the new IM -105. Order yours now. Kit 1M -105, 7
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t See these kits at your local Heathkit Electronic Center.. . or Send for Free Catalog.
CALIF.: Anaheim, 330 E. Ball Road; El Cerrito, 6000 Potrero Avenue; La Mesa, 8363
Center Drive; Los Angeles, 2309 S. Flower St.; Redwood City, 2001 Middlefield Rd.; Woodland Hills, 22504 Ventura Blvd.; COLO.: Denver, 5940 W. 38th Ave.; GA.: At-
HEATH COMPANY, Dept.1 5 -7 Benton Harbor, Michigan 49022
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Rd.; Mo.: St. Louis, 9296 Gravois Ave.; N.J.: Fair Lawn, 35 -07 Broadway (Rte. 4); N.Y.: Jericho, L -I., 15 Jericho Turnpike; New York, 35 W. 45th Street; OHIO: Cleve-
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Retail Heathkit Electronic Center prices slightly higher to cover shipping, local stock, consultation and demonstration facilities. Local service also available
whether you purchase locally or by factory mail order.
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J CL-411
July, 1971
CIRCLE NO. 115 ON READER SERVICE PAGE
49
Another LSI circuit for potential use in conjunction with solid-state readouts is the MMOS-1 2240-bit character generator. This circuit can generate the outputs required for 64 different USASCII characters to be displayed on a 5 X 7 dot matrix of light- emitting diodes.
Clearly, the combination of circuit and display arrangements offers a number of possibilities for compact portable
Modulation Input
LINEAR COUPLING ARRANGEMENT
Constant
i
pF
47
Current
/
Emitter
Input
Za
--IC
Detector
= 10 Volts Output
RL
Pulse Input
PULSE COUPLING ARRANGEMENT
47
IC
Emitter
c-
Detector
V LC 10 Volt
Pulse Output
RL
Fig. 6. The circuit arrangements that can be employed with optoelectronic couplers for linear, analog -type signals or For pulses.
Across the top are three 7- segment readouts showing different packaging techniques. Unit at top center has red cover and one
at right is on black background, thus obscuring display segments in both cases. Device at bottom center is optoelectronic coupler.
A group of optoelectronic detector arrays. The large device is 100-diode monolithic array; smaller ones are standard arrays.
50
equipment which would not be feasible without these interlocking technologies.
Optoelectronic Arrays
Like other semiconductor components, discrete optoelectronic devices, such as combined light-emitting diodes and photodetectors, have many uses. But their real potential lies in optoelectronic arrays which, like complex integrated circuits, are apt to gravitate toward custom designs. There will be, and indeed already are, a significant number of standard arrays. But these are produced more to demonstrate functional capability and manufacturing proficiency than an expected high -volume sales potential.
Of course, there are exceptions. Certain light-emitting displays (i.e., 7- segment readouts) do represent a huge market for standard parts; so do punched-card and tape-reading assemblies for standardized computer equipment. Many products for these functions have already emerged. But large as these specific markets are expected to be, they are nothing at all compared to the potential offered by custom designs.
An over-all glimpse of what is imminent and the possible impact on future designs, is best obtained by looking at some of the products that are now, or soon will be, availa-
ble.
Optoelectronic Couplers
An excellent example of optoelectronic utilization to replace conventional electronic components is the optical coupler. Consisting of an infrared -emitting diode coupled to a phototransistor in a single package, the device advantageously replaces interstage transformers and relays as well as coupling and feedback networks.
Consider as an example the MOC1000 coupler. The unit can be used as a linear -signal coupler or transformer and as a pulse coupler or relay (Fig. 6). In the former mode, a constant current supplied to the light emitter biases this diode and, since the output (infrared in this case) is directly proportional to the diode current, any increase or decrease of diode bias current resulting from an applied modulation input, causes corresponding variations in light output. These are coupled to the phototransistor detector which provides an equivalent linear output current. In this particular device, the output current is typically 60% of the input current and the bandwith is 700 kHz. Other devices, with an emitter- detector current gain greater than unity, are now available on a limited basis.
As a pulse coupler, the device requires no bias current. The detector is either "off" (with a dark-current of typically less than 20 nA) or "on" (with a maximum continuous forward current of around 35 mA).
Used as an electronic relay, it is fast-much faster than mechanical relays -and it has no contacts to "bounce," pit,
or corrode. It is small, insensitive to vibration, and unlike other forms of electronic relays, its output is completely isolated from the input.
Obviously, couplers of this type could be produced with a wide variety of gain, sensitivity, and output current.
Light-Emitting Displays
The cold -cathode gaseous display has been "king of the hill" for so many years that it is familiar to everyone working with digital electronic equipment. Now, however, its reign is being threatened by solid -state optoelectronic readouts that offer a number of advantages.
Optoelectronic readouts are smaller than their gaseous counterparts. Their numerals are only '/s" to '/4" high, compared to over 1/2" for the latter. Yet, they are so clear, sharp, and easy to read that they appear to be larger. Moreover, their bright red color makes them easily visible and distinguishable at a respectable distance. They operate at low voltage which makes them more compatible with transis-
. ELECTRONICS- WORLD
tors and integrated circuits than are
gaseous displays.
Optoelectronic displays come two
ways -monolithic and hybrid. The
monolithics are smaller but less expensive. They are designed for instruments, calculators, and other indicators read at short and medium distances. Hybrids are better suited for distance viewing, as in panel readouts. There's even work going on in combining the optoelectronic readout with all the associated electronic circuitry in a single package, so that each digit will be a complete, self- contained entity.
Sensing Arrays
Individually packaged photodiodes and phototransistors can be board mounted in large numbers to form discrete-device arrays. The smallest packages can be spaced as closely as 85 mils, but that's not nearly close enough for a great many applications. For extremely high -resolution requirements they are available as standard monolithic arrays of up to 39 photodiodes or photo transistors in a single package, while custom monolithic arrays can include more than 100 devices. In a typical array, the diode chips are spaced on 5mil centers with the active -element
area per chip being 4.5 by 5 mils.
These arrays are designed for optical
pattern and character -recognition
equipment, mark sensors, and a wide variety of other sophisticated and critical applications.
Nor is this necessarily the optimum or maximum array size. On a custom basis almost any linear or two-dimensional design can be obtained for special purposes, including star -pattern recognition for navigation.
Some special sensor arrays being produced for standard off-the -shelf availability include card and tape readers. Currently Motorola is producing 10- and 12 -cell arrays with standard card spacings (0.087" and 0.250 ", respectively) and 9 -cell arrays with 0.100" spacing for tape reading. These arrays consist of individually packaged cells that have been carefully matched for uniform sensitivity and then subsequently repackaged in array form. From these, it is but a short jump to corresponding light-emitting arrays. Since standard light-emitting diodes are individually housed in the same type packages as light sensors, they can be molded in the same type array forms as the detectors to assure a per-
fect match.
The Green Light
To date, materials used for most semi-
conductor light- emitters have been
gallium arsenide (GaAs) and gallium ar-
senide phosphide (GaAsP) -for infra-
red and visible red light. There is, however, a strong demand for a green -light
July, 1971
emitter, not only for the psychological impact of green light, but also because the eye is far more sensitive to green.
Green light can be obtained most
readily from gallium phosphide (GaP), a material that is more difficult to process than GaAsP, but its advantages far outnumber its drawbacks. The first dif-
ficulty encountered is that of crystal growing. Because gallium and phosphorous have greatly differing vapor
pressures, crystal pulling must be carried out in a special crystal "puller" ca-
pable of operating at pressures of 1500 -
-it psi (100 atmospheres). The importance
of GaP is due to its dual nature can be used for red -and green-emitting devices, depending on the dopants used. As a red emitter, GaP is more efficient than the more common gallium arsenide phosphide. However, the eye is not as responsive to the GaP characteristic wavelength so that apparent visual response is approximately equal for both
types. One significant advantage of GaAsP
over GaP (as a red emitter) is that
GaAsP devices exhibit a linear relationship between light ouput and current input up to very high current values. Therefore, such units can be pulsed at
high currents to yield an apparently high output (as long as power dissipation is kept within the thermal capability of the die and package). Gallium phosphide, on the other hand, saturates very quickly at increased current levels, with the resulting light output
reaching a fairly constant value. Although GaP devices of either red
or green light are now in short supply, GaP holds promise of being the materi-
al of the future. The role of GaAsP could well be like that of germanium
devices -there will always be some
cases where it will prove to be the best
choice.
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wrigohrrty, ,reimf esmombeert-hiitn'sg
still in the design stage."
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Advertising A Service usiness
The consumer revolt means that not only products but services must be offered on new and different terms.
By John Frye
ALATE afternoon thundershower had broken the endof-June heat wave, and the doors of Mac's Service
Shop stood wide open to welcome the cool damp air. Barney was glancing over the evening paper that had just been delivered while Mac made out a parts order. Matilda had already gone home.
"Hey, Mac," Barney said to his employer, "have you noticed a rather subtle change in advertising lately? Seems to me there's a lot less unfounded bragging about products and services and more down -to-earth talking with the customer."
"I've noticed," Mac nodded, "and I think it's a reaction to the consumer revolt, or whatever you call this new respect-
ful look at the customer many companies are taking -with,
it must be admitted, a little helpful prodding from Ralph
Nader and some forceful nudging from declining sales. For the first time many manufacturers are seeing their customers as intelligent individuals to be reasoned with, instead of as a herd of sheep easily led or stampeded in any desired direction by the expenditure of enough advertising dollars."
"I know you too well to believe you're 'agin' advertising,"
Barney observed. "That's right. I'm a firm believer in advertising to keep a
business growing. But I think the age of the Big Lie in advertising is over."
"What do you mean by that ?" "I think it was Hitler's Goebbels who is supposed to have said that if you repeated any lie, no matter how monstrous, often enough and emphatically enough, people would believe it. For several years many advertising companies have paid a tacit tribute to this theory. Hitting `the message'
hard was the thing-much more important than the essen-
tial truth of the message. This is the kind of advertising that depends heavily on reiterated slogans and bold statements that may be paraphrased as: `You can depend on Manufacturer X,' or `Manufacturer Y's products are better because of constant research,' or `Quality is a must with Manufacturer Z.'
"All too often money that would have justified these claims had it been spent on quality control and quality-directed research was diverted into advertising on the erroneous theory that people really didn't appreciate quality and were more swayed by what they read and heard than
by what they actually experienced with the products. "I know how I feel when I hear a TV announcer sounding
off on the sterling quality of the products of a certain manufacturer and recall having to return two defective percolators of that manufacturer before I finally got a good one, or remember returning a new electric can opener twice to his authorized service center because it simply would not open cans, and each time having it come back just the way it left.
I finally had to repair it myself. "I know I am not alone in my feelings. Today's consumer
is much more sophisticated and much less gullible than the customer for whom this kind of advertising was designed. He does not believe that after the salesman has married
52
him to a product the two of them will necessarily `live happily ever after.' He wants to know: What if the product is defective or later breaks down? What responsibility does the manufacturer assume and what provisions has he made for keeping the product working ?"
"I've seen several examples of the new kind of advertising," Barney observed. "I read that GM was carrying on an experiment in Chicago for a limited time in which any purchaser of a GM car in that area who felt he was not getting
satisfactory service on his new car from the local dealer could call the factory free of charge and discuss his complaint. And I'm sure you saw Whirlpool's TV advertisements in which Whirlpool washer owners anywhere in the U.S. were given a telephone number they could call in the event that they could not get proper service on their appli-
ances locally. Avis took full page ads to invite their customers to `Yell if Avis does something wrong' on a toll -free hot
line."
"These straws in the wind have not escaped my notice," Mac said, "and I'm convinced the radio-TV service operator would do well to align his own advertising with these
trends."
"Could be," Barney agreed, "but that will add another requirement to what I have always felt was a tough assignment: advertising a service business. We have problems not present in advertising a product. In the first place, we are trying to sell something intangible. We have nothing a customer can see, lick, sniff, hear rattle, or pinch. We can't take advantage of Wheeler's advice that `the sizzle sells the steak' because service doesn't sizzle."
"You're right. In a sense we have to sell our customers a pig in a poke. Not only do we have to persuade them they need the pork, but we must convince them our invisible pig is better than any other pig they can buy. In short, we are denied any sort of sensory appeal and must rely on purely
intellectual persuasion. Any advertising man worth his
salt-and all women-know it is much easier to appeal to
the senses than to appeal to the intellect." "How can the service technician give his advertising this
New Look?"
"His first aim must be to narrow the credibility gap between what his advertising says and what the average customer believes about radio-TV service. Thanks to the admitted shady practices of some technicians and to the representing of these practices by newspapers and magazines as being typical of the whole industry, that credibility gap can use a lot of narrowing. The only way to make people believe you is to tell the exact truth as simply and unequivocally as you can without ever making an exception. That sounds easy, but it's not. I never cease to be amazed at how people can misunderstand a statement in which there is no intent to deceive if that statement is not written with crys-
tal clarity."
"How's he going to get his message across? TV advertising is too expensive for the average service shop. Anyway, I've never seen a TV advertisement for service of any kind
that impressed me very much-with the possible exception
ELECTRONICS WORLD
of some of the clever, and I'm sure
quite expensive, oil company ads. I am not much impressed by shots of the interior or exterior of the service shop, nor by a picture of the service trucks all lined up, nor by an obviously posed picture of a young housewife becoming almost as ecstatic about the radio -TV service she gets from you as she does about the way her laundry comes out
when she uses Brand X detergent.
None of this is very convincing." "I agree. TV advertising is most ef-
fective when it can `show the product.' That's why I think it is most worthwhile when it is used by a service organization to plug its emblem. Well -written spot announcements on local radio stations aired during programs popular with adult audiences can be quite effective in keeping your business in front of the public.
"But neither of these afford much elbow room to practice the new honesty in- advertising technique we were discussing. Personally, I think the most effective means of doing this is contained
in the weekly short columns in newspapers I notice several widely different
businesses are using: automobile dealers, funeral parlors, real estate firms, and banks, for example."
"I'm not sure I know what you're
talking about." "Well, these are usually boxed stories
of a couple hundred words. Quite often a head-and-shoulders cut of the person whose name appears at the bottom is
used at the top of the story. These stories are educational in nature and their title spotlights this feature. For example, one used by car dealers might be
entitled How to Buy a Used Car, or
When Do You Need a Tune -Up? or The
Best Time to Trade. In each case, to be
effective, the story must be written so as to give the impression the author is
genuinely interested in helping the
reader." "How do you picture us using this
medium ?" "One way would be to acquaint our
customers with the fairness of our
charges. Take for instance the mark -up on tubes and other parts. Many people think we are crooks because our tube charges are higher than the wholesale
prices they see in catalogues. We could
explain such mark -ups are justified be-
cause we give time -and -place utility to the replacement items. We attempt to have them ready and waiting on our
shelves when the customer needs
them. Otherwise he would have to or-
der the parts himself from a distant parts store, pay postage on them, wait for several days or even weeks for delivery, and return the parts for examination and possible replacement if they were defective.
"To avoid all these inconveniences
for him, we tie up a lot of our capital
July, 1971
and expend lots of time and energy maintaining a large stock of parts. Quite often we suffer losses because items become obsolete on our shelves. If anything we sell is defective, we replace it immediately and then wrestle with the distributor about making it
good to us. The mark -up on parts is a
long, long way from being all pure
profit. In fact, we simply cannot afford to absorb all the expense of maintaining a large parts inventory. The markup on parts is simply a means of making this operation pay its own way."
"I get the idea," Barney said. "We could do another column on What is and What is not Covered by our Service Guarantee and Why. This is a fre-
quent source of misunderstanding. It should not be too difficult to make an intelligent customer see that if we re-
place one tube in a TV set we should be responsible for it alone and not for the other umpteen tubes in the set."
"You have the idea, but don't let's
forget our primary aim is to instill con-
fidence and trust in the customer's mind by showing that we have his interest at heart. Along that line other
stories could be: TV Checks You Can Make Before You Call a Service Technician, How to Keep Service Charges to a Minimum, It May Not Be the Picture Tube, and How to Care for Your Tape Recorder."
"You know," Barney mused, "this new advertising approach may usher in a new Era of Good Feeling between manufacturers and their customers that will benefit both. If so, it is not coming a bit too soon. Growing distrust and cynicism on the part of customers had already reached the place where conventional advertising dollars were largely wasted. More and more advertising was regarded as pure propaganda aimed at moronic minds. It will take a while to erase that impression, but at least we're making a start."
CONSUMER ELECTRONICS ANNUAL
The 1971 "Consumer Electronics Annual" which describes an industry that is hav-
ing an increasingly greater impact on the
daily lives of all Americans, has been published by the Consumer Electronics Groups
of the EIA. This handy booklet describes develop-
ments in the consumer electronics field
over the past 51 years and supplies statis-
tics on TV sets, radios, phonographs, audio components, tape equipment, and allied products. Also included in this 40-page publication are a chronology of consumer highlights, radio and TV stations, glossary of terms, and allied trade associations.
For from 1 to 24 copies the price is 50 cents each, dropping to 25 cents in quantities from 25 to 99. Order from Consumer Electronics Group, Electronic Industries Assn., 2001 Eye St., N. W., Washington, D.C. 20006. Payment must accompany all orders.
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CIRCLE N0. 126 ON READER SERVICE PAGE
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53
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CIRCLE NO. 116 ON READER SERVICE PAGE
Telephone Attachments
(Continued from page 29)
in general, the various signal specifications while the dialpulse description is shown in Fig.3. The central-office equipment is designed to expect at least one second of "onhook" interval between calls, although a 10- second interval is better design practice. To receive a dial tone after the "off-hook," your equipment must wait at least three seconds, although again a 10- second wait is recommended. Once your equipment starts dialing, the maximum period between digits should be no longer than 10 seconds. Even though Fig. 3 shows a minimum interdigit time of 600 milliseconds, a minimum of one second is recommended to avoid close tolerances.
The specifications in Table 1 are nominal and exact values may vary with local phone circuits. The 600-ohm impedance, for example, may actually be as low as 400 or as high as 1000 ohms. Speech transmission levels can vary even more widely. The typical value of -2 dBm, approximately 0.75 mW, may be as low as -12 dBm or 0.075 mW, although this would make for a weak -sounding phone con nection.
Most customer equipment will have little trouble meeting the out-of-band limits, although stray signals from the bias oscillator of a tape recorder could conceivably get into the phone line. Note also the requirement that no singletone signals in the 2450- to 2750 -Hz band are to be used.
Table 1. General specs for voice -connecting arrangements.
VOICE TRANSMISSION Transmission loss: Frequency range: Impedance: Speech transmission level:
0 dB 300 -3000 Hz 600 ohms (nominal)
-2 dB to -12 dB over
a 3- second interval
OUT -OF -BAND LIMITS 3995 -4005 Hz 4000-10,000 Hz 10,000-25,000 Hz 25,000- 40,000 Hz Above 40,000 Hz
At least 18 dB below in -band
Less than -16 dBm Less than -24 dBm Less than -36 dBm Less than -50 dBm
INTERNAL IMPEDANCE (subscriber's equipment) 600 ohms in voice band (resistive)
SIGNALING CONSIDERATIONS Because of tone -signaling devices used for network control functions, customer devices should have no signals with energy solely in the 2450-2750 Hz band. If such signals are present, at least equal energy in the BOO- to 2450 -Hz band must be present.
D.C,. SIGNALS AND POWER
Any d.c. must be less than 10 mA into the voice
transformer of the coupler.
Max, between any conductor
135 volts d.c.
and ground:
50 volts d.c.
ELECTRONICS WORLD
Measuring Color-TV X-Rays
(Continued from page 39)
emitted from the face of the color picture tube. A single survey meter may be used, provided you are thoroughly familiar with its characteristics, calibration, accuracy, and energy dependence.
To begin with, the TV set should be "off " and a background count taken. This background reading will then be subtracted from x-ray readings (if any). The high-voltage control should be adjusted by an authorized factory representative in accordance with factory specifications. In most cases, since the TV receiver was factory adjusted, there should not be any above-acceptable x -rays emanating from it. Using just the front-panel controls of the TV set, survey the receiver under four operating conditions: 1. set the brightness control for the darkest viewing picture, 2. set the brightness control for maximum brightness, 3. set the TV receiver off-channel with maximum brightness, and 4. survey the TV with the brightness control set for normal viewing.
When performing a survey, pass the survey meter and /or detector very slowly about 2 inches from all cabinet surfaces, including the bottom and rear of the TV set (see Fig. 3). Above all, remember that the x -ray reading on the meter will fluctuate and an average reading should be taken. If readings above acceptable levels are detected, you can in most cases reduce x -rays to a safe level by performing one or more of the following: 1. properly adjusting the high voltage, 2. replacing the high-voltage and /or shunt- regulator tubes, and 3. installing tube shields. Once the suspected fault has been corrected, the TV set should again be surveyed to insure that the x-radiation has been minimized.
A word of caution for the electronics service technician.
Always be consciously aware of the possibility of radiation emission from other products as well as from TV receivers. Full knowledge of the products you service is a "must" in order to protect yourself, and those around you, from these insidious hazards. In many service shops, service technicians and their fellow workers risk unnecessary exposure. To cite one example, a color -TV receiver was out of its cabinet, lying on the side of the chassis with high-voltage tube shielding missing, and the set turned on. This is not only an electrical hazard, but also a radiation hazard. A TV receiver, which must be "on" after repairs, should be isolated from service personnel. The service technician working on a TV receiver should disable all hazardous circuits or use radiation shielding. The high voltage should be checked and /or adjusted as per the manufacturer's specifications with a calibrated high-voltage meter and probe combination before the color-TV receiver is returned to its owner.
For those who may want to build their own GM survey meters, the Public Health Service has issued a booklet entitled, "Simple X -ray Detection Instrument for Television Service Technicians." The PM number is BRH /DEP 70-14. The booklet costs $3.00 and is available from the Clearinghouse for Federal, Scientific, and Technical Information, Springfield, Virginia 22151.
The Victoreen Company and the Eberline Instrument Corp. have complete lines of battery-operated color-TV survey instruments for anyone wishing to purchase one. Information is available by writing to: Victoreen Instrument Div., 10101 Woodland Ave., Cleveland, Ohio 44104 and to Eberline Instrument Corp., Santa Fe, New Mexico.
REFERENCES
"Conference on Detection and Measurement of X-ray Radiation from Color Television Receivers." U.S. Department of Health, Education, and Welfare, Public Health Service.
"Color Television and the X -Ray Problem." Federal Trade Commission
True 4'Channel Sound
[s42.50 per 20 watt channel)
There are several components on the market that you can take home and get true 4- channel sound out of today.
All are expensive.
Except ours.
We call ours QAUDIO.* It's an amplifier and player with 4 discrete channels. And we designed it primarily to play the new 8 -track 4- channel cartridges.
But we also give it the capability of playing ordinary
8 -track stereo cartridges,
because there are a lot more of them around today than
there are 4- channel car-
tridges. And QAUDIO makes
even ordinary stereo car-
tridges sound fuller and richer than they ever have before.
But of course it takes a specially recorded 4- channel cartridge to give you the real QAUDIO experience, and there's no point in try-
ing to describe what that's like. It's simply something
that has to be experienced.
And you can experience it today -at a price that's
almost as unbelievable as the sound: $169.95. (That's $169.95 for a true 4- channel amplifier-player with 80 watts of total music power.) A QAUDIO unit for your car or boat is just $129.95.
We'll be happy to send you the names of dealers
near you demonstrating QAUDIO, together with a brochure describing it in
detail.
t uum Write to Toyo Radio Company of America, Inc., 1842B West 169th Street, Gardena, Calif. 90247.
BY ToYo
A SHOCKING EXPERIENCE IN SOUND.
;PRONOUNCED "KWAH -010''. THE NAME QAUDIO IS BASED ON THE GENERIC "QUADRIPHONIC ".
July, 1971
CIRCLE NO. 110 ON READER SERVICE PAGE
55
How to
become a
"Non-Degree
Engineer"
Exciting careers in the new industries of the Seventies are waiting for men with up -to -date electronics training. Thousands of real engineering jobs are being filled
- by men without engineering degrees
provided they are thoroughly trained in basic electronic theory and modern application. The pay is good, the future is bright ...and the training can now
be acquired at home -on your own time.
56
ELECTRONICS, the Science of he Seventies, has created a new breed of pro-
fessional man-the non- degree engineer.
Depending on the branch of electronics he's in, he may "ride herd" over a sophisticated computer installation, run a powerful TV transmitter, supervise a law enforcement communi cations control center or work side by side with distinguished scientists fighting pollution or doctors seeking a medical break-through.
But you do need to know more than soldering connections, testing circuits and replacing components. You need to ready know the fundamentals of electronics.
How can you pick up this necessary knowledge? Many of today's non-degree engineers learned their electronics at home. In fact, some authorities feel that a home study course is the best way. Popular Electronics said:
"By its very nature, home study develops your ability to analyze and extract information as well as to strengthen your sense of responsibility and initiative."
CIE Method Makes It Easy
f you do decide to advance your career through home study, it's best to pick a school that specializes in the home -study method. Electronics is complicated enough without trying io learn it from texts and lessons that were designed for the classroom instead of the home.
Cleveland Institute of Electronics con centrates on home study exclusively. Over
ELECTRONICS WORLD
the last 35 years we have developed techniques that make learning at home easy, even if you once had trouble studying. Your instructor gives the lessons and questions you send in his undivided personal atten-
tion-it's like being the only student in his
"class." He not only grades your work, he analyzes it. And he mails back his corrections and comments the same day he gets your lessons, so you read his notations while everything is still fresh in your mind.
Students who have taken other courses often comment on how much more they learn from CIE. Says Mark E. Newland of Santa Maria, California:
"Of 11 different correspondence courses I've taken, CIE's was the best prepared, most interesting and easiest to understand. I passed my 1st Class FCC exam after completing my course, and have increased my earnings by $120 a month."
Always Up -To-Date
Because of rapid developments in electronics, CIE courses are constantly being revised. This year's courses include up -tothe-minute lessons in Microminiaturization, Laser Theory and Application, Suppressed Carrier Modulation, Single Sideband Techniques, Logical Trouble- shooting, Boolean
...Algebra. Pulse Theory, Solid -State Devices and many more.
... An FCC License or Your Money Back
CIE'S AUTO-PROGRAMMED® Lessons are so successful that better than 9 out of 10 CIE graduates who take the FCC exam pass
July, 1971
it. This is despite the fact that, among non -CIE men, 2 out of every 3 who take the exam fail! That's why CIE can promise in writing to refund your tuition in full if you complete one of its FCC courses and fail to pass the licensing exam.
This Book Can Help You Thousands who are advancing their electronics careers started by reading our famous book, "How To Succeed in Electronics." It tells of many non -degree engineering jobs and other electronics careers open to men with the proper training. And it tells which courses of study best prepare you for the work you want.
Let us send you this 44-page book free. Just fill out and mail the attached postpaid card. Or, if the card is missing, mail the coupon, or write directly to: Cleveland Institute of Electronics, 1776 East 17th Street, Cleveland, Ohio 44114.
NEW COLLEGE -LEVEL CAREER COURSE FOR MEN WITH PRIOR EXPERIENCE IN ELECTRONICS
ELECTRONICS ENGINEERING...covers steady-state and transient network theory, solid -state physics and circuitry, pulse techniques, computer logic and mathematics through calculus. A college -level course for men already working in Electronics.
CIRCLE NO. 145 ON READER SERVICE PAGE
CCofleIEEvleelacntrdonInicsstitute
1776 East 17th Street
Cleveland, Ohio 44114
Please send me without cost or obligation: Your new illustrated 44 -page book, "How To
Succeed in Electronics." Your book on "How To Get a Commercial FCC
L tense."
I am especially interested in:
Electronics Technology Electronics Technology with Laboratory Broadcast Engineering First Class FCC License Electronic Communications Industrial Electronics Electronics Engineering
Name Address
(please print)
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NEW REVISED G.I. BILL BENEFITS: All CIE courses are approved for full tuition reimbursement under new G.I. Bill. If you served on active duty since laauary 31, 1955, OR are in service now, check box for G.I. Bill information.
Accredited Member National Home Study Council
Ew -91
L
59
OOKS
"CIRCUIT PROBLEMS AND SOLUTIONS" by Gerard Lip -
pin. Published by Hayden Book Company, Inc., New York, N.Y. Three volumes: 188, 125, and 90 pages, respectively.
Prices $3.95, $3.95, and $3.55. Soft cover.
This three -volume set has placed major emphasis on practicality and is designed to supplement and amplify standard texts on electricity or serve as a reference source.
Volume I covers elementary methods, volume 2 covers network theorems, while volume 3 deals with transistor and tube circuits. In each volume the approach is a mathematical analysis of individual circuits and, since the scope is
wide, these three volumes provide a handy source book for information on everything from Ohm's law, resistive circuits, series and parallel circuits, through delta to wye transformation, Millman's Theorem, to tube and transistor
constants, decibels, audio voltage and power amplifiers, to resonant circuits. Each volume includes appendices on conversion factors, trigonometrical ratios, and four -figure logs so each book is self-contained. Problems are worked out, making this series suitable for home study if desired.
*
"HANDBOOK OF ELECTRONIC TEST EQUIPMENT" by
John D. Lenk. Published by Prentice -Hall, Inc., Englewood
Cliffs, N.J. 451 pages. Price $15.00. This handbook is for practicing and /or in- training techni-
cians and is designed to familiarize them with all types of
test equipment they are liable to encounter in their work. By providing basic information on how the various meters and test devices work, technicians can quickly figure out the operation of more sophisticated equipment by analyz-
ing them circuit by circuit or stage by stage. In eleven major sections the author deals with analog me-
ters, digital and differential meters, bridge-type test equipment, signal generators, scopes and recorders, electronic counters, amplifiers, frequency and time standards, probes
and transducers, wave analyzers, and microwave test
equipment. A special appendix covers digital logic circuits. The material is informally written, lavishly illustrated,
and, above all, practical. This text can be used in lieu of instruction manuals on equipment operation or to amplify instructions provided by the manufacturer.
*
*
"RADIO SPECTRUM HANDBOOK" by James M. Moore.
Published by Howard W Sams & Co., Inc., Indianapolis,
Ind. 181 pages. Price $7.95. This is a relatively painless way for the non-specialist to
obtain all the information he requires regarding the allocation of the radio spectrum without having to plow through voluminous government files and multi- volume Rules and
Regulations. For those without any technical background, the author
has provided two chapters explaining the nature of radio waves and receiving equipment but the bulk of the material deals with allocations, 1.f. and v.l.f., medium frequencies,
high frequencies, v.h.f. and u.h.f., and the types of services
operating in the various bands. The text includes tables covering almost every conceiv-
able aspect of the subject from call-sign assignments to the types of equipment that can be used in the various services.
60
While emphasis is on allocations and services in the U.S.,
certain foreign assignments are also covered where long -
distance transmissions might be involved.
*
*
*
"ELECTRONIC DESIGN DATA BOOK" by Rudolf F. Graf.
Published by Van Nostrand Reinhold Company, New York.
307 pages. Price $17.95.
This is a varied compilation of data needed by engineers,
technicians, hams, and students, presented in the form of
nomograms, tables, charts, and formulas. It is not intended
to instruct the user on the theory or derivation of such data
but to serve merely as a quick reference source for informa-
tion.
The material is divided into six functional sections which
deal with frequency data, communications, passive compo-
nents and circuits, active components and circuits, mathe-
matical data, formulas and symbols, and physical data.
The large format of the book and the generous size of the
nomograms, diagrams, tables, and charts make this an easy-
to-use addition to any technical library.
*
*
*
"HOW TO USE VECTORSCOPES, OSCILLOSCOPES & SWEEP- SIGNAL GENERATORS" by Stan Prentiss. Pub-
lished by Tab Books, Blue Ridge Summit, Pa. 17214. 253 pages. Price $7.95 hardbound, $4.95 soft cover.
Although the author admits that there are already hundreds of books on scopes, vectorscopes, and sweep and signal generators on the market, he feels that covering all three of these instruments in a single volume is justified since his emphasis is on how such equipment should be used, not the nuts -and-bolts of the circuitry.
In ten chapters he deals with scopes in general; vector scopes; basic uses for a scope; sampling, storage and spec-
trum-analyzer scopes; sine, square, and triangular waves; push-button alignment and sweep generators; vectorscope troubleshooting and chroma alignment; finding faulty components with a scope; IC and transistor circuit troubleshooting; and tracking down stereo multiplex faults with the vec-
torscope. The text is elaborately illustrated and the only reserva-
tion regarding this book is that the author concentrates on Tektronix and Telequipment scopes to the exclusion of other models, which may be disconcerting to those not familiar
with these lines.
*
"ELECTRONIC ORGAN SERVICING GUIDE" by Robert G.
Middleton. Published by Howard W. Sams & Co., Inc., Indi-
anapolis, Ind. 126 pages. Price $4.95. Soft Cover. This volume has been prepared for the service technician
who is accustomed to working on hi-fi equipment but has
hesitated to tackle electronic organs, despite their proliferation in private homes as well as clubs, churches, and other public places. The author contends there is nothing to be "scared" of in organ servicing and proceeds to demonstrate how easily the hi-fi technician can make the switch to organ servicing (which can be a profitable field, according to the
author). The nine chapters cover general principles; preventive
maintenance and evaluations; adjustments and minor repairs; tone-generator troubleshooting; servicing the keying
system; tracking down troubles in the voicing section; piano /harpsichord, glockenspiel, and special voicing networks; amplifier servicing; and troubleshooting electronic -
organ power supplies. The text is clear, concise expanded and augmented by a
wealth of large, easy -to -read diagrams, charts, partial schematics, photographs, and tables. Equipment needed to service the organs is also discussed and pictured. A glossary of terms peculiar to electronic organs has been included as has a frequency chart of the tempered scale, and a reference chart to standard electronic schematic symbols as used
in the text.
ELECTRONICS WORLD
Miniature
Wide -Range
Build this pipelike
Schober Recital Organ
for only
VL.F Tuner
By N.H. BROWN /Associate Engineer Senior Tucson Engineering Lab., Hughes Aircraft Co.
Using magnetic bias to control large inductance changes (15 mH- 100µH) makes design of miniature tuners for low- frequency applications feasible.
HE LC circuits for low- frequency
I applications become large and
cumbersome when conventional meth-
ods are used to vary the value of either
L or C to cover the low- frequency
spectrum from approximately 1 kHz to
600 kHz.
To cover this frequency range with a variable capacitor and fixed inductors would require a capacitor with many
plates and very large physical dimen-
sions, plus a bank of fixed inductors
that could be band-switched into the
circuit.
A variable permeability device has been developed that is capable of covering this frequency range with a sin-
gle inductor and a miniature fixed ca-
pacitor. This is made possible by using
an inductor whose value can be
changed from 15 mH to 100 H. This large inductance change is ac-
complished by changing the permeability of a ferrite toroid core upon which the inductor is wound. Magnetic bias is applied to the core by two small permanent magnets in a unique arrangement whereby one magnet is held in a fixed position while the second magnet is rotated 180 degrees in
polarity relationship to the fixed magnet. The core to be controlled is positioned between the two magnets.
When Ml is aligned with M2 in un-
like polarity, flux lines are in effect short -circuited, flowing directly between unlike poles and having minimum effect on the core. This is the point of maximum inductance. As the shaft carrying Ml is rotated toward the point where like poles of the magnets will be aligned, an increasing number of flux lines are forced to flow through
the core until near saturation is
reached at the 180- degree point. This is the point of minimum inductance. Flux linkage through the core follows a path that would not normally be expected, maximum linkage occurring when like magnetic poles are aligned.
A prototype was constructed to the dimensions shown in the diagram, us-
July, 1971
ing an Indiana General ferrite core Type CF101 of 0 -6 material, 0.230" o.d., 0.120" i.d., and 0.060" thick,
wound with 100 turns of No. 35 magnet wire. The magnets are 0.5 inch in diameter, V- grooved with normal N -S polarity, and have a flux density of approximately 350 gauss. The air gap between magnets and core is adjusted to approximately 0.01 inch. Minimum in-
ductance can be adjusted by this air
gap up to the point of core saturation.
The inductance, as measured on a
Boonton Q- meter, was 15 millihenrys maximum and 100 microhenrys minimum for a 180-degree shaft rotation. Average Q over this range was 40.
With a fixed capacitor of 0.001 µF
shunting the inductor, the tuning
range is 40 kHz to above 600 kHz. This range can be extended down to 7 kHz by the addition of a 0.047-µF capacitor.
This type of construction and inductance control makes possible the design of miniature tuners for the low frequency spectrum, and would allow the design of small, portable v.l.f. receivers, chokes, band -pass filters, etc.
Only one type of ferrite material has been investigated at this time and perhaps materials of other types would yield similar or improved results. The primary purpose of this article is to point out the technique and feasibility.
(Note: A patent disclosure (PD68529) on this device is on file with
Hughes Aircraft, Culver City, Calif)
Dimensions and construction details on v.l.f. tuner with an inductance range of 15 millihenrys to 100 microhenrys.
BRASS SPACERS
M2 FIXED
PLASTIC PLATES
7/8" DIA. I/8" THICK
MI ROTOR
CORE MOUNTED IN CENTER PLASTIC MOUNTING RING
'Includes finished walnut
console. (Only
$1446 if you build your own console.) Amplifier, speaker
system, optional accessories extra.
You couldn't touch an organ like this in a store for
less than $4,000 -and there never has been an elec-
tronic instrument with this vast variety of genuine
pipe-organ voices that you can add to and change
any time you like! If you've dreamed of the sound
of a large pipe organ in your own home, if you're
looking for an organ for your church, you'll be more
-kit thrilled and happy with a Schober Recital Organ than
you could possibly imagine
or no kit.
You can learn to play it -and a full -size, full-facil-
ity instrument is easier to learn on than any cut -down
"home" model. And you can build it, from Schober
Kits, world famous for ease of assembly without the
- slightest knowledge of electronics or music, for de-
sign and parts
above all -for
quality from the highest
the ground praise from
up, and musicians
everywhere.
Send right now for the full-color Schober catalog,
containing specifications of all five Schober Organ
models, beginning at $499.50. No charge, no obliga-
tion. If you like music, you owe yourself a Schober
Organ!
The
Organ Corp., Dept. R N- 92
43 West 61st Street, New York, N.Y. 10023
Please send me Schober Organ Catalog and free 7 -inch "sample" record. Enclosed please find $1.00 for 12 -inch L.P. record of Schober Organ music.
NAME
ADDRESS
CITY
STATE
ZIP
CIRCLE NO. 123 ON READER SERVICE PAGE
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10 Reasons why
RCA Home Training is
your best investment
for a rewarding
career
in electronics:
Performing transistor experiments on programmed breadboard -using C4
oscilloscope.
62
ELECTRONICS WORLD
1 LEADER IN ELECTRONICS TRAINING
When you think of electronics, you immediately think of RCA... a name that stands for dependability, integrity, and pioneering scientific advances. For over half a century, RCA Institutes, Inc., a subsidiary of RCA, has been a leader in technical training.
2 RCA AUTOTEXT TEACHES ELECTRONICS FASTER, EASIER, ALMOST AUTOMATICALLY
Beginner or refresher, AUTOTEXT, RCA Institutes' own method of programmed Home Training will help you learn electronics more quickly and with less effort, even if you've had trouble with conventional learning methods in the past.
3 WELL PAID JOBS ARE OPEN TO MEN SKILLED IN ELECTRONICS
RCA Institutes is doing something positive to help men with an interest in electronics to qualify for rewarding jobs in this fascinating field. There are challenging new fields that need electronics technicians... new careers such as computers, automation, television, space electronics where the work is interesting and earnings are greater.
4 WIDE CHOICE OF CAREER PROGRAMS
Start today on the electronics career of your choice. On the attached card is a list of "Career Programs", each of which starts with the amazing AUTOTEXT method of programmed instruction. Look the list over, pick the one best suited to you and check it off on the card.
5 SPECIALIZED ADVANCED TRAINING
For those already working in electronics or with previous training, RCA Institutes offers advanced courses. You can start on a higher level without wasting time on work you already know.
6 PERSONAL SUPERVISION THROUGHOUT
All during your program of home study, your training is supervised by RCA Institutes experts who become personally involved in your efforts and help you over any "rough spots" that may develop.
7 HANDS-ON TRAINING To give practical application to your studies, a variety of valuable RCA Institutes engineered kits are included in your program. You get over 250 projects and experiments and as many as 22 kits in some programs. Each kit is complete in itself. You never have to take apart one piece to build another. They're yours to keep and use on the job.
- FCC LICENSE TRAINING
8 MONEY BACK AGREEMENT
Take RCA's Communications Career
program -or enter with advanced stand-
ing and prepare immediately for your 1st, 2nd, or 3rd class FCC Radio Telephone License examinations. RCA Institutes money -back agreement assures you of your money back if you fail to pass the FCC examination taken within 6 months after completing the course.
9 CONVENIENT PAYMENT PLANS You get a selection of low-cost tuition plans. And, we are an eligible insti-
tution under the Federally Insured Student Loan Program.
10 RCA INSTITUTES IS FULLY ACCREDITED
RCA Institutes is an accredited member of the National Home Study Council. Licensed by N.Y. State-courses of study and instructional facilities are approved by the State Education Department.
VETERANS: TRAIN UNDER NEW GI BILL
SEND ATTACHED POSTAGE PAID CARD TODAY! FREE DESCRIPTIVE BOOK YOURS WITHOUT OBLIGATION!
If reply card is detached, send this coupon today.
1 RCA INSTITUTES, INC. DEPT. 240 -007 -1
320 W. 31 ST. NEW YORK, N.Y. 10001
Please send me FREE illustrated career catalog. I understand that I am under no obligation.
IJ
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Address
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Veterans: Check here
L
J
Construction of Multimeter.
ncn
Temperature experiment with transistors.
Construction of Oscilloscope.
July, 1971
65
Do you know about
the group of audio
modules created by
Sinclair for the
Project 60 line?
New Generation IC -12
Would you like an impressive amount of material describing the world's
first consumer Phase Lock Loop FM stereo tuner plus power amplifier modules and power supplies, a fine preamplifier module and the unique Sinclair Active Filter Unit? Write Audionics for free information or en-
close $1.00 for a Project 60 manual, detailed technical data, applications ideas and a certificate refund ng your dollar with the purchase of a Project
60 module from Audionics or an
authorized dealer. We'll even include
details on Sinclair's New Generation
Sinclair integrated circuit power amplifier.
Write:
Audionics, Inc.
8600 NE Sandy Blvd. Portland, Oregon 97220
1
1
Name
I
I
1 Address
1
1 City
State
Zip
I
ewj
CIRCLE NO. 149 ON READER SERVICE PAGE
Cooperate With The Zip Code Program of The Post Office
Department.
Remote U.H'.F. -TV
Signal-Seeking System
By PAUL LeFEVRE Sylvania Electric Products Inc.
Here is a circuit developed by Sylvania that provides the TV viewer with means to remotely select u.h.f. channels.
THE eight-function remote -control system described in this article pro-
vides the user with the capability of twodirection (up -band and down-band) signal seeking on the u.h.f. TV channels, in addition to the usual seven functions (volume up and down, color increase and decrease, tint red and green, and
.
v.h.f. channel) . In effect, this system provides nine remote-control functions using only eight frequency channels. The use of eight channels is dictated by the limited frequency spectrum falling between the second and third harmonics of the TV horizontal oscillator, which is used for remote control, and the necessary separation between these eight channels to assure proper operation of the system.
AilSince this article is concerned with the signal-seeking system, only the circuits pertaining to this function are discussed.
Operation of Circuit
The circuit for the remotely controlled u.h.f. signal-seeking system was designed to work in conjunction with a detector to stop a conventional motordriven u.h.f. tuner on- channel, within the a.f.c. pull-in range, and to provide the user with remote control of the direc-
tion in which the tuner starts. Reversing on command is also provided.
To obtain two-direction control using one function, a 34.25-kHz ultrasonic signal, generated by a transistor oscillator in the remote-control unit, is sent or 0.75 second or less for up-band, and one second or more for down-band direction of search. The tuner doesn't move while either signal is being sent but does start when the transmitter switch is released. Tuner direction can be changed while in the process of signal seeking using the same method; the result is ease and reliability of u.h.f. TV-channel selection without confusing the user.
Relay Control
A search relay and a reversing relay in conjunction with a remote relay, which is in the remote receiver and is operatorcontrolled, provide full control of the u.h.f. drive motor. This has two stator windings tied together at one point and fed back to one side of the 117-volt a.c. power source. Thus, referring to the block diagram, it can be seen that the drive motor is energized by connecting one of the stator windings through con tacts on the reverse, search, and remote relays to the other side of the power source. Note that the state of the reverse
Block dia:ram of Sylvcnia's D-12 remote -contro'' u.h.f. signal- seeking system.
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63
OTHER
FU CrrONS
O
150V IRING RE CT
U.KF. DRIVE wOTOR
SYNC SET.
¡il
S.S. COLLECTOR
A.F C. AMP.
ELECTRONICS WORLD
relay determines direction of rotor rota-
tion.
How It Works
When the transmitter switch at the remote unit is pressed, an ultrasonic signal is generated that is picked up by a microphone transducer at the input of the Remote Receiver Preamp circuit, amplified, and fed to the appropriate detector circuit. In this case, since the remote units is in the u.h.f. mode, the 34.25 -kHz signal transmitted by the transistor oscillator activates the Detector circuit for the u.h.f. circuitry. The output of the detector circuit, in turn, energizes the remote relay causing both the 150 -volt Timing Rectifier and 20volt Regulated supply to switch on. The 150-volt timing circuit, acting through the Search Initiate circuit (a transistor circuit operating in the common -emitter configuration) to the 20-volt supply, energizes the search relay. Accordingly, when the transmitter switch is released, the remote relay is de-energized causing
the 150-volt timing circuit to switch "off" and the 150-volt sustain rectifier circuit to switch "on" through the normally open contacts of the search relay. Although the 150-volt timing circuit is "off," the search relay is maintained in its energized state by the Search Sustain circuit (a transistor circuit operating in the common -emitter configuration) and 20 -volt regulated source. It should be noted at this time that during search initiate (search relay energized) the 20volt source is supplied from the 150-volt timing circuit and during search (u.h.f. motor energized) by the 150-volt sus tain circuit.
The u.h.f. drive motor, initially activated when the remote relay was energized and maintained by the 150 -volt sustain rectifier circuit, runs in the direction determined by the state of the reverse relay and will continue to run as long as the search relay remains energized. However, referring to the diagram, it can be seen that if the remote relay is held closed by the operator, after the search relay is energized, the motor remains inoperative. This keeps the search tuning operation fully automatic yet controlled by the operator.
Once energized, the search relay remains in this state until the two detectors feeding the search-sustain circuit receive the sync (15.75 kHz) and carrier (45.75 MHz) signals, coincidentally. With the receipt of these two signals, the search relay is de- energized, thereby opening the 150 -volt sustain circuit and causing the u.h.f. drive motor to stop. The response is fast enough to stop the motor reliably on station.
Timing Circuit's Function
The function of the Reverse T. C. and the Reverse Amp. timing circuits is to delay the energizing of the reverse relay
July, 1971
when the 150-volt timing circuit is switched on. In effect, this action prevents the circuit from interpreting any quick succession of short-hold transmissions as a long-hold one. In addition, the reverse amp circuit helps maintain constant timing at all line voltages between 105 and 132 volts. Consequently, when the long -hold (1 second or more ) transmission signal is received, the reverse relay, after a short delay, is energized and the u.h.f. drive motor actuates the tuner down-band. When a short -hold (0.75 second or less ) transmission signal is received, the reverse relay will remain in its de-energized state and the motor will drive the tuner up -band.
Band -End Switch A switch, which is an integral part of the signal- seeking system and not shown in the diagram, is actuated when the tuner dial mechanism reaches either end of its travel; at the top of the band it energizes the reverse relay from the 20-
volt source, causing the motor to reverse its direction to down-band, and at the low end of the band it shorts the 20-volt regulated source to the ground -return circuit de-energizing the search relay and terminating the search. With the receipt of the next short -hold signal the motor will drive the tuner up-band, removing the 20 -volt source from the ground-return circuit and restoring the normal search operation. This arrangement for shut -off prevents the possibility of continuous search that may be initiated inadvertently when there is no broadcast or when there is an antenna or circuit malfunction.
At the end of search, either on- station or at the low end of the band, both 150volt supplies are shut off leaving the circuit in a passive state yet alert to the next command from the remote transmitter.
In addition, contacts are provided on the search relay so that the TV audio is muted during the u.h.f. signal- seeking operation.
"You'll need 24 hours to fix this one. I've been working on it!"
. #i 2.4^ía`=?D:.-',,`tr,,h..':k
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Binaural recording re- creates the directions, dis-
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Binaural recording offers the listener the identical acoustical perspective and instrument spread of the
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STARTLING REALITY. The Binaural Demonstration
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demon-
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MUSIC IN BINAURAL. The musical) performances
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The Stereo Review Binaural Demonstration Record is the ultimate in sound reproduction. It has been made without compromise for the owner of stereo headphones. If you own stereo headphones, this
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PAYMENT MUST BE ENCLOSEC WITH ORDER Emma
67
Understanding
Complex
Waveforms
By LAWRENCE S. NICKEL
Engineer, General Electric Co.
The harmonic content of various types of non-sinusoidal waves and the use of
oscilloscopes to observe such waves.
WAVEFORM analysis is a complex field which can be very difficult to understand. Let's talk first about
square waves, for instance. You may know that square
+v
,r
27r
cot
_V 4V/ Tr
4V/ 37r
4V/5 77
4V/97r
o
2
3
4
5
6
7
8
9
NUMBER OF HARMONIC
Fig. 1. The square wave at the top has a line spectrum (up through the first nine harmonics) as shown at the bottom. Wave has no d.c. component, hence no "O harmonic."
Fig. 2. Harmonic composition of triangular waveform. Note presence of d.c. component and rapidly falling harmonics.
waves have a lot of harmonics. What you may not know is that square waves have no even harmonics. Perhaps you know that the strength of the harmonics decreases as you go up in frequency.
For the square wave (with its 50% duty cycle, or "on" half of the time) this is certainly true, but for the pulse (other than 50% duty cycle), this is not necessarily so. Depending on the duty cycle, the fundamental or first harmonic may be strong, the next few harmonics decrease in strength, and then the following several harmonics may be stronger again.
We are concerned here with only periodic waveforms. A periodic waveform is one which repeats itself exactly each time interval, and this time interval is called the period. Each periodic waveform which is non -sinusoidal will con-
f tain certain harmonics, the first of which is the fundamen-
tal. If the period is t (time), then the frequency (in hertz) of the fundamental is 1 ft. No frequencies lower than the fundamental may be found in any complex waveshape.
A logical method for displaying the harmonic content of a waveform is by use of line- spectra charts. Refer to Figs. 1 through 3. These charts indicate the relative positions and strengths of each harmonic (only the first few harmonics are shown). Often a line is included at zero frequency to indicate the d.c. (average) value of the wave.
The set of harmonics are named Fourier series. According to theory the strength of the members (harmonics) of this series gets weaker and eventually goes to zero at infinite frequency. Since the waveform is actually the algebraic sum of all harmonics (which would include all those out to infinity), as we add higher and higher harmonics we get a closer and closer approximation of the actual waveform.
One way to predict the strengths of the harmonics of a particular waveform is by using integral calculus; however,
Fig. 3. This sawtooth waveform has the harmonics shown. Note that odd and even harmonics are included in waveform.
27r Olt
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2
3
4
5
6
7
8
9
NUMBER OF HARMONIC
7r
2v/7r
2Vi37r V/2s 2V/57r
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I
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3
4
5
6
7
8
NUMBER OF HARMONIC
2V/9A I 9
ELECTRONICS WORLD
by using data with the harmonic
strengths already worked out as shown
in the figures, we can draw some con-
clusions. For instance, the ninth har-
monic of a square wave is fairly weak
compared with the lower harmonics.
This means that if your oscilloscope has
a bandwidth approximately ten times
the fundamental of the square wave,
you can get a fairly accurate reproduc-
tion of the square wave on the scope
screen. If your oscilloscope had a band -
pass of up to 1 MHz with a very sharp
cutoff there (which is unlikely) and you
fed in a perfect 500 -kHz square wave,
you would see a 500 -kHz sinusoid on
the screen.
The shape of the waveform is direct-
ly related to its risetime. This is the
time for the .value of the wave to go
from 10% to 90% of its maximum val-
ue. In general, the faster the risetime,
the stronger the higher harmonics. If
the wave has sharp bumps or spikes, it
will have strong harmonics up to many
times the. fundamental. There is also a
correlation between sound and wave -
shape. The waves with the sharp points
(sawtooths, square waves, and triangu-
lar waves) are the ones that are rough
or sharp sounding. The sine wave is the
"smooth-sounding" one.
There is a relationship between
bandwidth and risetime that is true for
most oscilloscopes. The formula for ex-
pressing this is T,.B =0.35, where Tr is
the risetime of scope (µs) and B is
bandwidth of scope (MHz). By know-
ing the risetime of your scope you can
figure the approximate signal risetime
it will display with little or no distor-
tion.
Suppose you feed a pulse into your
scope. If the risetime of the waveform
is slow (long) with relation to the rise-
time of the scope amplifier, then the
scope will be able to reproduce the
waveform accurately. But if the pulse
has a risetime almost as short as or
shorter than the oscilloscope's risetime,
the scope amplifier will not be able to
move the stored charge in the capaci-
tors of the scope amplifier rapidly
enough, and distortion occurs.
A simple formula relating the vari-
ous risetimes is: t3= t12+ 122, where
tl equals the scope risetime, t2 equals
the actual signal risetime, and t3 equals
the risetime which will be observed on
the scope screen. Suppose the scope
risetime is 3µs. If a pulse is fed in with
a 40 -µs risetime, the observed risetime
on the screen is almost exactly 40 µs.
So the scope has not distorted the pulse
much. Suppose the wave put in has a
risetime of only 4 µs; we will then see a
pulse on the screen with a 5 -µs rise-
time. This risetime has been distorted
or "stretched out" by 25 %. Hence, we
need to know risetime and frequency
if we really want to know if the scope is
giving a true picture.
A
July, 1971
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A.P.M. SYSTEMS, INC. 1551 Almaden Rd.
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A.P.M. SYSTEMS, INC. Dept. M15 P.C. Box 9159, San Jose, Calif. 95117
Make and repair your own patchcord stacking plugs in seconds. Any color, any length for 40% less cost.
These new kits contain everything you need to custom assemble and/or replace damaged molded stacking patchcord plugs: 60 metal banana or .OBO standard tip metal plugs, 60 housings, 10 in each of the six standard colors. An assembly tool and fixture for fast, easy assembly. Use with standard 0.144" wire (not included in kit). To assemble, simply feed stripped end of wire through cross -hole metal contact. Insert contact and wire into housing. Place in fixture and snap contact into place. Convenience and flexibility, pl us savings of at least 40 %over molded stacking patchcord plugs.
E. F. Johnson Company, Waseca, Minnesota 56093
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Please send me complete information on your new stacking patchcord kits.
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®E. F. JOHNSON COMPANY
CIRCLE N0. 134 ON READER SERVICE PAGE
69
&NELWITEPRRAOTDUURCETS
COMPONENTS TOOLS TEST EQUIPMENT HI -FI AUDIO
For additional information on items identified by a code number, simply fill in coupon or Reader Ser vice Card. In those cases where code numbers are not given, may we suggest you write dire3t to the manufacturer on business letterhead.
CB COMMUNICATIONS
RADIATION MONITOR
The new Model 8200 radiation monitor complies with the requirements specified for test equipmeat in the proposed performance stan-
dards as published by the Department of
Health, Education and Welfare in the Federal Register dated May 22, 1970.
The "Mini -Surveyor" has a calibration fre-
quency of 2450 MHz but other frequencies are available on special order. It features two full scale power reading ranges 10 mW /cm2 and 100
mW /cm- with the Model 8223 probe and 2
mW/cm2 and 20 mW /cm2 with the Model 8221 probe. Accuracy of the probe calibration is 1
dB (calibrated at 2 mW/cm2 at a distance of96
inches at 2450 MHz; stated accuracy applies over the complete power- density range of the
probe). Accuracy of the instrument is t3% of
full scale. The complete unit (Model 8200) includes me-
ter, battery, one probe as selected by the customer, and a 2 -inch spacer. A data sheet, 17 -14, providing complete details on this lightweight, portable instrument is available on request. Narda
Circle No. 3 on Reader Service Page P.A. AMPLIFIERS
Three solid -state p.a. amplifiers for general purpose or professional applications have been introduced as the Models PA -25, PA -50, and PA -100.
The PA -25 has a power output of 25 watts r.m.s., 50 watts peak, at less than 5% distortion. Frequency response is 100 to 10,000 Hz. The PA -50 is rated at 50 watts r.m.s., 100 watts peak, while the PA -100 provides 100 watts r.m.s. and 200 watts peak, both at less than 5% distortion.
All three units are designed to operate from 105 -120 volts, 60 Hz a.c. power sources and
measure l51/2" X 51/2" u 101/2" deep. Lafayette
Circle No. 4 on Reader Service Page STEREO PREAMPS
Two new stereo preamplifiers that provide the voltage gain, equalization, and choice of impedances necessary to operate magnetic phono car-
70
tridges and tape playback heads have been introduced as the Models M64 and M64-2E.
According to the company, the preamps provide complete freedom from microphonics, extremely low noise, and the ability to use 50 feet or more of output cable when operated as an impedance converter and buffer amplifier.
Both models have a single slide switch for selecting equalization for phono, tape, or flat. Positions provide RIAA equalization for magnetic stereo cartridges, NAB equalization for tape heads, and flat for microphones or for use as a buffer amplifier.
The M64 operates on 120 volts, 50/60 Hz or from an auxiliary 24- to 36 -volt d.c. supply while the M64-2E operates on a line voltage of 240, 50/60 Hz. Shure
Circle No. 5 on Reader Service Page
SPEAKER-SYSTEM KIT A kit version of the Acoustic Research AR -3a speaker system is now available as the AS -I03. The kit uses three AR drivers in a sealed acoustic-suspension enclosure to deliver a virtually flat response from 30 to 20,000 Hz. The 12' woofer provides clean bass down to 30 Hz while the special AR hemispherical dome mid -range and tweeter, combined with a specially engineered crossover network provides transparent sound to well beyond audibility. Separate output -level controls on the rear of the cabinet for both mid -range and tweeter allow the user to custom-tailor the sound to suit the acoustic environment. The walnut cabinet measures 25" high X 14' wide X 111/2" deep and will fit on a bookshelf or can be used as a floor- standing system. Heath Circle No. 6 on Reader Service Page
METRIC TOOL KIT A 100-piece metric-measure tool kit has just been introduced as the JTK -17 MM. The kit is designed for field engineers' use on foreign-made and international -design equipment having metric-measure fasteners and parts. Virtually every normal tool likely to be required when making
- repairs or adjustments to electronic or data -
processing equipment has been included. Emphasis has been placed on fastener tools
those needed to dismantle and reassemble complete systems. The tools are packed in an attaché case with two removable pallets. The case measures 41/2" deep and has a solid wood frame with mahogany paneling. The hardware is solid brass. Partitioned compartments of the case hold larger tools and parts. Space for service manuals and documents is provided in the cover. A Triplett #310 v.o.m. tester to fit into the case is available as an optional accessory. Jensen Tools
Circle No. 7 on Reader Service Page
4- CHANNEL STEREO DECODER A kit version of the new Electro -Voice "Stereo -4" decoding system is now available as the AD-2002. The new system permits the audiophile to enjoy the sound of 4- channel stereo at modest cost. The decoder, when used in conjunction with an existing stereo system and a second amplifier and speaker system, permits listening to 4-channel stereo of any tape, record, or stereo -FM broadcast that has been encoded
using the EV matrixing system. According to the company, assembly of the
kit takes about 2 to 4 hours using the step-by-
step manual and giant fold -out pictorials supplied. Connection and operation are equally
simple. Front -panel knobs control "on- off"/
master gain and source switching; the rear panel
provides complete inputs and outputs. All cir-
cuitry. including the IC, is identical to the EV unit. Heath
Circle No. 8 on Reader Service Page
SOLDERING TOOLS Two new precision soldering tools have been introduced as the W-TCP -L and W -MCP. The former is a controlled- output tool with interchangeable tips which automatically provide precise wattage control from 20 to 60 watts. Accessories are designed for maximum productivity in production -line, R&D, or service-bench applications. It is a fast-recovery unit with an isolated low- voltage power supply and flexible non -burning cord. The Model W-MCP is a solid -state miniaturized tool for micro-soldering with a fixed -temperature element, isolated low -voltage power supply, and flexible non -burning cord set. It is offered in temperature ratings of 550 and 750 degrees F, with a variety of specialized tips to meet virtually any micro -soldering application from 5 to 20 watts. Weller Circle No. 9 on Reader Service Page
STEREO TAPE DECKS Two stereo tape decks, the GX -280D and GX -220D, both with glass and crystal ferrite heads have been recently introduced to the U.S.
market.
The core of the GX head is made of a single crystal ferrite and the inner circumference of the heat shield is mounted and set in glass. As a result, the GX head is "dust free" from magnetic tape particles, according to the company. Thus, sound quality is not affected even under
ELECTRONICS WORLD
excessively high temperatures and humidity. According to the company, wear and abrasion are almost completely eliminated and tape motion stability is enhanced because of the high
degree of glass and crystal ferrite hardness. The GX-280D is a 4- track, 2-channel stereo/
mono system which operates at 7'/2 and 33/4 in/
s. It will handle up to 7" reels. Response is 30-
24,000 Hz +3 dB at 7'/2 in /s. Signal -to -noise
ratio is better than 50 dB. The GX -220D is a 4-track, 2-channel stereo/mono deck which operates at 71/2, 33/4, and 1% in/s. Frequency response and signal -to-noise ratio is the same as the 280D at 71/2 in /s. Both have three heads and three motors.
Complete specifications on these new decks are available on request. Akai
Circle No. 10 on Reader Service Page
DIGITAL MULTIMETER A new multimeter with a digital display has been put on the market as the Model 3469A. The instrument makes average a.c. measurements from 1 millivolt full -scale to 500 volts over a frequency range from 20 Hz to 10 MHz, resistance measurements on its most sensitive range of one ohm full -scale to 10 megohms full scale, d.c. measurements from 100 mV to 1000 V full-scale, and d.c. current from 1µA to 100
mA full -scale. A data sheet giving complete specifications on
the Model 3469A is available. Hewlett -Packard Circle No. 11 on Reader Service Page
SOUND SYSTEM
r I A six -mode, 70-watt sound system designed
for public safety applications is now available. It can be used for public address, police siren, yelp, European siren, radio relay, and listening applications. The multiple-siren feature permits alternating the emergency signal for maximum clarity and effect while the listening mode makes it possible for two-way p.a. conversation with all windows rolled up.
An exclusive input circuit triggers at extremely low signal levels. At 100 MHz, for example,
only 30 mV maximum is needed to trigger. A front -panel sensitivity control and built -in meter allow adjustment of the input signal for maxi-
mum sensitivity. Pressing the "Test" switch gives a quick, accurate indication of proper
counting. The IB -102, which is supplied in kit form,
comes with a heavy -duty aluminum case with combination handle/tilt-stand. Heath
Circle No. 13 on Reader Service Page
Various weather-resistant, low -profile speakers are available and can be easily installed with-
i lout obstructing a warning light. Full details are
available on request. Standard Communications Circle No. 12 on Reader Service Page
175 -MHz FREQUENCY SCALER The IB -102 frequency scaler, when used in combination with virtually any frequency counter on the market, provides measurement capability to 175 MHz. The unit will divide input frequencies from 2 MHz to 175 MHz, with the scaled output fed to any frequency counter with a 1- megohm input. Front -panel switches allow selection of 10:1 or 100:1 scaling ratios, with counter resolution down to 10 Hz when used with a counter having a I- second time base. A 1:1 switch provides straight- through counting without scaling for use with frequencies within the range of the counter being used.
DIGITAL READOUT SYSTEM A new displacement measuring system which operates as a ratiometer to provide a system accuracy to +0.1%, +1 digit is now available. The system consists of a high- accuracy d.c. -d.c. linear variable ditTerential transformer, a shielded cable with a connector at each end, and a 31/2-digit readout (0 to +1999). The system operates at its rated accuracy with line voltage variations over the range of 98 to 125 V. Since d.c transmission is used between
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Built -in monitor speaker with 1000 cycle tone burst
Built -in keying relay
- Completely solid-state 21 transistors
Rechargeable battery operated ,
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July, 1971
CIRCLE NO. 144 ON READER SERVICE PAGE
71
the transducer and the display unit there are no cable capacity and crosstalk problems, according to the company. Complete details are available on request. Pickering
Circle No. 14 on Reader Service Page
4- CHANNEL ADAPTER The "Dynaquad" adapter, plus two additional speakers, combined with any existing stereo amplifier or receiver permits the reception of 4channel sound from stereo records, tapes, or stereo -FM broadcasts. The reflected sound components picked up automatically by the recording microphones during 2- channel recording are normally
masked by the so- called "Haas effect." These reflected sound components reproduced through the rear speakers provide the necessary 4-channel effect.
The adapter has a 4- position function switch with a special balance position for achieving precise adjustment among the four speakers in the system, a rear-level control for adjusting the volume of the rear speakers, and a function switch which may be used to operate the front and rear speakers separately. For normal listening the function switch is left in the "4 Ch." position.
The walnut- grained metal enclosure measures 52/4" wide X 49/16" deep X 21/2" high.. Lafayette
Circle No.15 on Reader Service Page
PANEL FUSEHOLDER A new knob lens has been designed for the firm's "glow when they blow" 3AG indicating type panel fuseholders and is fully interchangeable with the series 343 and 344 lenses. The new lens is conical and extends -11/2" in front of the mounting panel and provides additional application flexibility to circuit and panel designers of electric instruments, computers, and commercial equipment, according to the company. As an added space- saving feature, the fuseholders extend only 1.56" behind the mounting panel. The fuseholder can be used as a pilot light with the lamp "on" to indicate continuous current flow. The lamp glows until the fuse blows, a reverse of the usual application of indicating-type panel fuseholders. Littelfuse Circle No. 16 on Reader Service Page
VOLTMETER /DIGITAL DISPLAY A true r.m.s. voltmeter that covers almost the whole spectrum of a.c. measurements has been introduced as the Model 3403A. The instrument
measures d.c. and a.c. from 1 Hz to 100 MHz. Using a three-digit LED display with a fourth digit for overrange, the d.v.m. reads both in volts and, with an option, in decibels.
The a.c. voltage is measured from 10 mV to 1000 V full-scale with an accuracy of +0.2% of
, :::""....°°"
range. The instrument reads dBV from -60 to +60 with an accuracy of 0.1 dB.
A full range of options is available including autorange, BCD output, and remote programmability for systems applications. Analog outputs proportional to volts and decibels are available for use with analog recording devices.
The Model 3403A measures 41/2" X 73/4" X 9'/2 ". Hewlett-Packard
Circle No. 17 on Reader Service Page
STEREO CASSETTE DECK The new F -106E stereo cassette tape deck features a dual -bias selector switch and the company's exclusive "Endmatic" automatic shut -off
system. With this system the tape transport stops, thereby eliminating tape tension. At the same time the tape -drive mechanism automatically disengages, avoiding any possibility of deformation to the rubber pinch roller. All pushbuttons return automatically to the "off" position and the signal light indicating the end of the tape turns "on" and stays on.
The dual -bias selector provides for extended frequency response when used with the new super- dynamic cassettes. This feature permits selection of the proper bias setting for either. standard or super cassettes.
The deck also features separate right- and left -channel record level controls with backlighted vu meters, a remote start/stop control unit, tape counter, pause control, noise filter, and headphone monitoring. Frequency response is 40- 12,000 Hz with wow and flutter less than 0.2% r.m.s. Concord
Circle No 18 on Reader Service Page
MUSIC SYNTHESIZER The recently introduced ARP 2600 P electronic music synthesizer is housed in a specially designed carrying case which provides protection against bumps and handling wear. The synthesizer is a practical instrument for
individual performers and composers. A comprehensive manual on synthesizers, which is obtainable separately, has been prepared for guidance in operating the unit.
A table -top consolette version of the synthesizer in.a wrap-around cabinet is also available.
Tonus Circle No. 19 on Reader Service Page
MIKE/PARABOLIC REFLECTOR The new "Astro- Mike" kit, recently introduced, is designed for persons who want to tape record happenings, even at a distance: The kit includes a Model 2393B portable cassette tape recorder /player, an ultra-sensitive long-distance microphone with parabolic reflector, a hand-held remote -control microphone, a blank C30 cassette, an earphone, and six "C" cell batteries. Complete details on this equipment are available on request. Bell & Howell Circle No. 20 on Reader Service Page
tape pilot which indicates the mode of operation at a glance; and a headphone-level switch which adjusts the playback volume when monitoring through headphones:
The deck also includes a tape- select switch to optimize record equalization for standard or the new chromium- dioxide cassettes. Superscope
Circle No. 21 on Reader Service Page
CB ANTENNA The "Sigma 1/2" is a new legally installable 22 -foot, 1/2-wave ground plane antenna designed to provide strong, noise -free, long- distance performance. Although it must be installed 2 feet . below the highest point on a house or building, the low -angle radiation_take -off gives a ground hugging.signal for longer distance and fewer dead spots, according to the company. A matching loop which prevents burn -outs and detuning eliminates the need for coils or transformers. The radiator is adjustable for fine tuning and pre-marked for easy "no measuring" assembly. This telescoping section uses full circle clamps for positive electrical contact and sturdy construction. The heavy -duty radials have stainless-steel tips for reduced wind loading. The antenna is d.c. grounded to reduce static and noise. Avanti Circle No. 22 on Reader Service Page
ENDLESS -LOOP CASSETTE An endless-loop cassette designed specifically for industrial, business, and educational use is now on the market. The new cassette has a playing time of three minutes which, according to the company, is the longest that currently can be employed within the reliability and durability requirements of industrial use. Endless -loop cassettes enable users to program the same message at planned intervals. They have application in alarm systems, point of- purchase messages, and announcements in such places as elevators, museums, zoos, amusement parks, among others. Norelco Circlle No. 23 on Reader Service Page
STEREO TAPE DECK" A budget-priced 4 -track stereo tape deck has just been introduced as the T-6100. The unit is enclosed in an open -faced oiled -walnut cabinet which can be mounted vertically for shelf use or operated horizontally. It features easy loading and can be single -hand threaded in seconds. The circuit provides stabilized pressure between the pinch roller and capstan to protect the
® e©®t% `Tr 0J
72
STEREO CASSETTE DECK
The Sony Model 160 stereo cassette deck in-
corporates several major engineering advances
including closed-loop dual- capstan drive which
eliminates modulation distortion and reduces
i
wow and flutter to an imperceptible 0.1 %; a built-in peak limiter which reduces high-level transient peaks to the 0 vu level; and illuminated
ELECTRONICS WORLD
tape and insure constant operating conditions. A sensing foil can be used to reverse the tape or it can be reversed by pushing a single button. A pause lever can be used for stopping the tape momentarily, during record or playback, making it easy to edit tapes.
The deck is a 4- track, 2-channel stereo or 4track, 1-channel mono unit using reels up to 7" in diameter. It features three heads and can op-
erate at either 7'/2 or 33/4 in/s speeds. Frequency response is 30-20,000 Hz at 71/2 in /s and 30-
13,000 Hz at 3% in/s. Pioneer Circle No. 24 on Reader Service Page
SWEEP /SIGNAL GENERATOR The Model ASG -1 audio sweep /signal generator is designed for use in the frequency range of 0 to 100 kHz. It will display the response characteristics of either active or passive circuits on a standard oscilloscope. Both swept and c.w. operating modes are provided and sweep width is variable from a few hertz to 100 kHz in a single
sweep. Output is adjustable from 0 to 5 volts peak -to-
peak. A synchronized ramp output with adjusta-
"ANNOUNCING MY 3RD GRAND OPENING!"
"I opened my first
Allied Radio Shack store with a small investment .
-in The smartest move I ever
made
June, 1968 I opened
my first retail store in Ports-
mouth, N.H. Things happened
fast and with the profits from
that store I opened a second,
in Dover, N.H., in July 1969.
My 3rd .Grand Opening? June
1, 1971, in Holyoke, Mass. Be-
lieve me when I say the Allied
Radio Shack plan is the great-
est thing going in consumer
electronics."
Tony Esposito
ble amplitude is supplied for driving the horizontal input to the scope. If triggered operation is desired, generator blanking pulses are available. Sweep time is variable from 20 ms to 20 s for one sweep. Rameco
Circle No. 25 on Reader Service Page
STEREO POWER AMP The Model 250 stereo power amplifier provides a full 250 watts r.m.s. continuous power throughout the audio spectrum, from 20 to
20,000 Hz, with both channels driven at or below the rated distortion, according to the company.
Among the features included in this new unit are illuminated professional output-level meters, operating over two selectable ranges permitting deflection sensitivity at output levels as low as 125 milliwatts. The amplifier is convertible for use on either 120 volts or 240 volts by simply changing internal connections to the tapped power-transformer primary.
A unique relay-operated protective circuit prevents damage to output transistors, power supply, or speakers from excessive levels of subsonic frequencies. It acts as a stabilizer, protecting speakers against high power surges and eliminating transient thumps and pops sometimes encountered in solid -state amplifiers. Mar antz
Circle No. 26 on Reader Service Page
PORTABLE DIGITAL V.O.M. The 460 digital v.o.m. features 26 switch -selectable ranges to cover a wide variety of testing situations. These include five a.c. and d.c. voltage, five a.c. and d.c. current, and six resistance ranges with accuracy from ±0.1% of reading, ±1 digit. Since no separate battery pack or power supply is needed, the unit is completely portable. Operation is from line power or batteries. The batteries are self-contained. Four nickel- cadmium rechargeable "D"-cell batteries will supply up to 8 hours of continuous operation. Powerline operation automatically recharges the bat -
teries.-
The numerical display is a 31/2-digit -instant readout, with automatic overrange, plus and mi-
July. 1971
$30,000 PUTS YOU IN BUSINESS FOR YOURSELF!
AelleliectdronRicasdioreStahialecrk-oisvea rd9iv5i0siosntoreosf
Tandy Corp. (NYSE)' and the nation's biggest from coast -to-coast and In Alaska! We offer
consumer a unique
franchise opportunity to energetic men and women who want a retail business of their own.
Within weeks you can be the outright owner of a store too. You get the full benefit of
)ur 50 years of experience, right away. Here's your chance to be your own boss, to he
an important part of the community you select for your store, to achieve real success,
real status.
* * * *
PROFITS! PRESTIGE! SECURITY!
OUR PLAN IS SUCCESS -DESIGNED
It covers everything from your Grand Opening to everyday operations. A. full -color annual catalog, dynamic sales flyers and local newspaper ads keep the customers coming! You benefit from creative merchandising, continuing assistance, plus the convenience of dealing with a single, reliable vendor.
YOU'RE IN A CLASS BY YOURSELF
There's no other operation like ours . no one else can sell the same brands "right across the street." You'll be selling Allied Radio Shack's own nationally famous products including 100's of exclusives not sold elsewhere: Allied and Realistic audio and CB products, Knight -Kits, Archer antennas and parts, Radio Shack batteries, PortaVision Concertape, many others. All priced "right" for healthy gross profits for you.
INDEPENDENCE!
BA TANDY CORPORATION COMPANY
CALL COLLECT OR WRITE . . .
A. A. Bernabei Vice President Allied Radio Shack 2617 West 7th Street Fort Worth, Texas 76107 Phone (817) 336 7163
Locations available from coast to coast!
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73
nus indication. The front -panel analog meter shows peaks and nulls at a glance.
The 460 measures 4" X 81/2" X 71/2" and
weighs 61/2 pounds with batteries and 6'/4
pounds without batteries. Bulletin T-811, available on request, gives complete details. Simpson Electric
Circle No. 27 on Reader Service Page
PROGRAMMABLE H.V. SUPPLY A BCD digitally programmable power supply with outputs to.10 kV d.c. has been introduced as the Model RHR- I0P100X241. The unit features a line and load regulation of 0.02%, ripple of 0.1 %, and an output accuracy of 0.2% of rating. It is capable of being voltage programmed by punch -card insertion to a computer or other programmer and will provide additive outputs in 10-volt steps in BCD code 1 -24-8 in three decades, 10, 100, and 1000 volts d.c. Output current is 0 to 10 mA. The supply is housed in a 19" rack- mounting cabinet with standard notching. Spellman Circle No. 28 on Reader Service Page
FREQUENCY COUNTER The latest addition to the company's line of frequency counters is the Model 150A automatic counter. This small, lightweight instrument can be operated from either standard a.c. or battery power sources to automatically measure and display frequencies from 5 Hz to 32 MHz. Extensive use of IC's, especially medium -scale integration, makes the Model 150A compact and light. It measures only 41/2" wide X 2" high X 7'/2" deep and it weighs less than 3 pounds. Monsanto Circle No. 29 on Reader Service Page
NUMERICAL READOUT TUBE The new NL -1222 numerical readout tube has a seated height of 1.456 inches, a diameter of 0.512 inch, and character height of 0.5 inch. It has been especially designed for applications where space limitations are critical, such as in modern digital instruments. Designed for use at 170 volts d.c., the tube operates equally well in the d.c., strobe, or timeshare modes, according to the company. It is available in a variety of base configurations and is designed for both solder -in and socket applications. A data sheet with complete electrical and mechanical specifications will be forwarded on request. National Electronics Circle No. 30 on Reader Service Page
MANUFACTURERS' LITERATURE
INSULATION RESISTANCE TESTS How to test insulation resistance with the new "Meg-Chek" megohmmeters is described in a 34 -page operation and applications handbook just published. This handy pocket-sized booklet describes how the instruments can be used as an important tool in a preventive maintenance program. Operating instructions, setups and procedures for various test applications, and maintenance considerations are covered in detail with the help of schematics and photographs.
74
Copies of the handbook, Manual 17456, are available on request. Associated Research
Circle No. 31 on Reader Service Page
CAPACITORS & RESISTORS A revised short-form catalogue that includes performance specifications on several recently introduced capacitors and resistors is now available as EPD DSF -1. The four-page, illustrated folder lists performance characteristics, physical descriptions, and military designations for each of the company's glass and glass -ceramic capacitors and glass tin oxide film resistors. The firm's BX semi- precision capacitors and miniature NC3 high-reliability and high- voltage flameproof resistors are also covered. Corning Glass
Circle No. 32 on Reader Service Page
KIT/WIRED PRODUCTS Some 250 products in both kit and wired versions, in nine lines, are covered in a new 32 -page catalogue now ready for distribution. Included are photographs and complete specifications on stereo components, audio color organs, projects of various types, solid -state test equipment, accessories, strobe lights, and ham
gear. Eico
Circle No. 33 on Reader Service Page
RFI SHIELDED CHAMBERS A four-page folder which describes the construction and performance of several types of RFI shielded chambers is now available from Emerson & Cuming, Inc., Canton, Massachusetts 02021. Chamber size may vary from 130 feet by 100 feet to 8 feet by 8 feet. The firm is prepared to design and construct the chamber to a customer's specifications or supply parts so that the customer can make his own installation or shield an existing area. The brochure lists the typical insertion loss versus frequency which is achievable with each type of construction. The shielding effectiveness against magnetic fields, electric fields, and plane
waves is also shown.
ALUMINUM ELECTROLYTICS A new 16 -page Engineering Bulletin, 3431C, providing detailed information on the company's "Powerlytic" aluminum electrolytic capacitors for use in computer main -frame peripheral power supplies, energy storage applications, and industrial control equipment, is now available for distribution. The bulletin provides complete information on all standard ratings in the new extended range design, performance characteristics, and a guide to application and operation which gives full data on permissible r.m.s. ripple current. The Technical Literature Service, Sprague Electric Co., 51 Marshall St., North Adams, Mass. 01247 will forward a copy on request.
CABLE -STRIPPING TOOL A single -page data sheet describing a new stripping tool for single- and double -braid cable is available from the Electronic Components Division of Deutsch Company, Municipal Airport, Banning, California 92220. The brochure pictures this manual tool, which makes the clean, square-shouldered cuts required to cold strip single- or double-braid cable and leave it ready for termination, and explains its special features. When writing, request a copy of Bulletin No.
107.
INDUSTRIAL INSTRUMENTS Heath Company, Benton Harbor, Michigan 49022 has just issued a 68 -page catalogue covering its line of scientific instrumentation for industrial and academic labs. Pictured and described is an extensive line of kit and assembled instruments and systems including digital timing and power modules; readout modules; TTL logic circuits; binary information and auxiliary modules; universal digital
instruments; lab instrumentation; servo -chart recorders; power supplies and voltage reference sources; all types of scopes, generators, and operational amplifiers; v.t.v.m.'s and resistance boxes; and spectrophotometers plus hundreds of components, accessories, and expansion circuits designed to be used with the basic equipment.
WIRE, CABLE & CORD Standard Wire and Cable Company, 3440 Overland Ave., Los Angeles, California 90034 has just issued a 110-page technical manual and catalogue covering wire, cable, and cord for every application. The catalogue is divided into five sections: a comprehensive listing of products with complete technical information; a glossary of wire and cable terminology; a complete listing, definitions, tables, and illustrations covering. coaxial cable; a comparison chart which lists military specification wires, uses, construction, and ratings; and general wire tables, charts, and conversion factors.
VISUAL CONTROL SYSTEMS Methods Research Corporation, 105 Willow Avenue, Staten Island, New York 10305 has just issued a new 28 -page catalogue covering 49 sizes of standard boards and over 100 accessories which comprise the firm's magnetic visual control systems. The brochure shows in pictures and text how the boards can be used for handling every type of job a company would want done in maintaining perpetual data for daily, weekly, monthly, or yearly use in scheduling, inventory control, production planning, shipping and ordering, and personnel management.
ZENER -DIODE GUIDE A six-page zener-diode selection guide, detailing more than 700 part numbers in various packages, voltages, and amperages is now available from Microsemiconductor Corporation, 11250 Playa Court, Culver City, California 90230. The material is presented in handy tabular form for quick selection of a specific diode to handle a particular job. Mechanical configurations are also included. Requests for a copy of this guide should be directed to the attention of Sharad Rastogi at the company.
LOGIC HANDBOOK Signetics Corporation, 811 East Arques Ave., Sunnyvale, California 94086 has just re- issued the second volume of its "MSI Specifications Handbook, Series 8000 Designer's Choice Logic." This volume covers the company's arrays and provides information on design considerations, electrical characteristics, and explains the firm's "Sure" program of testing these medium-scale integrated circuits.
PHOTO CREDITS
Page
Credit
6.... KLH Research & Development Corp.
7
Sony /Superscope
29 (top, center)
AT &T
29 (bottom)
Tron -Tech, Inc.
30 (top)
RCA
30 (center) ...Goodyear Aerospace Corp.
30 (bottom) ....United States Steel Corp.
31 (top)
IBM
31 (center)
LaBarge, Inc.
31 (bottom left)
GTE Sylvania
31 (bottom right) .. Delco Electronics Div.
37. 38 (left) ... Eberline Instrument Corp.
38 (right)
Victoreen Company
44. 45
Heath Company
46, 48, 50
Motorola Inc.
ELECTRONICS WORLD
Regulator Nomograms
(Continued from page 33)
we cross the center (W) scale at 0.044 watt. A half-watt resistor would be more than adequate.
Since we have a 10 -volt zener, we enter this value on the first scale on the left. Since the zener will hold the volt-
age on one side of the series-dropping resistor at 10 volts, then the 15-volt noload voltage of our power supply will drop 5 volts across the series resistor.
This can produce a 55 -mA current
through the resistor of which 20 mA will be required in the load, leaving 35 mA through the zener. Entering the far-right scale at 35 mA and joining the
far -right and far -left scales with a
dashed line, we find the zener power to be 0.35 watt. If we assume that it is possible for the load to be disconnected, the latter two numbers could be 55 mA for the zener and 0.55-watt dissipa-
tion. Hence, in either case a 1 -watt
zener would probably provide an adequate safety factor.
The fourth nomogram, Fig. 5, can provide trade -offs to determine the regulation to be expected or can help to determine the parameters necessary to select a zener for a given performance. The first three scales on the left are power-calculation scales using the
familiar:
Pz = ER(load) Iz where: Pz is zener power consumption, ER(load) is zener and load voltage, and I. is zener current.
The three scales on the right make use of the manufacturer's data on the zener temperature sensitivity. The two scales on either side of the center (R) scale, Pz and Rp, are used to determine the final regulation to be expected from our system. These three scales are used with the equation:
RP= CrRT
where: Re is regulation sensitivity in percent per watt, CT is temperature coefficient in percent per °C, and RT is thermal resistance in °C per watt.
For example, repeating the zener power calculations of the last nomogram using E =10 volts on the left scale, 1 =35 mA on the second scale, we reach P =0.35 watt on the third
scale.
Then if the manufacturer gives the temperature coefficient as 0.10 % / °C for the zener we are considering, this value is entered on the far-right scale. If this particular zener also has a thermal resistance of 20°C /watt, this is entered on the RT scale. A line joining these points and extending to the left
will intersect the RP scale at 2.0% /
watt. Now a line joining this point with 0.35 watt on the Pz scale crosses the R scale at 0.7% which is the over -all expected regulation.
July. 1971
The Proven Crimestopper
Everyone knows crime is increasing steadily. h fact. statistics show that one out of
every six homes will be victimized this year. What car you do about it? The DeltAlert Ultrasonic Burglar Detection á Alarm System was developed to helo protect you and your family. DeltAlert effect vely monitors and blanketE. up to 300 sq. ft. of space, utilizing the sonar principle -o pick Lp even the slightest motion. When DeltAlert is activated, horn anc lights automat tally begin operating. The loud ear shattering blasts of the high irrensity horn, coupled with light drives away even the boldest intruder. At home or work, protection begins with the
DeltAlert Alarm and $69.95
Detection System. It's maintenance free, and to install you simply plug
it in. Order yours today, and start enjoying the feeling that comes with DeltAlert protection.
Here Are 8 Reasons to Put
The Mark Ten B On Your Car
The Mark Ten B CD System with exclusive VARI S =ARK` Ci-cuitry will give you
these substantial dollar saving advantages: 1) El minate 3 out of 4 tune -ups;
2) Improve combustion, reduce contaminants; 3) Install in ten minutes; 4) Instant
start in atl weather; 5) Dramatic increase in performance;
6) Hardy switch with redundant contacts for instant
eturn to staidarc ignition; 7) Two -piece hous-
ing with reoprene seals provides total
dust and moisture
protection; 8) Use
on ANY 12 -volt,
negative-ground
engine. Put the
Mark Ten Bon
- - - - - - - -' SuperiorProducts
At Sensible Prices
your car today. It will pay for
itself in do'lars saved.
Mark Ten B (12v neg only)
Oily $59.95 ppd.
Standard Mark Ten $44.95 ppd.
Please send me literature immediately. Enclosed is $_
Ship ppd. C.O.D.
Please send:. _ __DeltAlert(s) @ $69.95 ppd. _DeltaHorn(s) @ $24.95 ppd
Mark Ten B @ $59.95 p pd.
Standard Mark Ten (Assembled) @ $44.95 ppd.
6 Volt: Neg. Ground Onl y Positive Ground
12 Volt: Specify
Negative Ground
Standard Mark Ten (De Itakit) @ $29.95 ppd. (12 Volt Positive Or Ne gstive Ground Only)
1
Car Year
Make
Name
Address
DELTA City/State
Zip
PRODUCTS, INC.
Ar al - - - - - - - IS P.O. Box 1147, Grand Junction, Colorado 81501, (303) 242-9000
1
CIRCLE NO. 142 ON READER SERVICE PAGE
75
ELECTRONICS
MARKET PLACE
COMMERCIAL RATE: For firms or individuals offering commercial- products or services. $1.00 per word (including name anc. address). Minimum order $10.00. Payment must accompany copy except when ads are placed by accredited advertising agencies. Frequency discount: 5% for 6 months; 10% for 12 months paid in advance.
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FOR SALE
GOVERNMENT Surplus Receivers, Transmitters, Snooperscopes, Radios, Parts, Picture Catalog 25d. Meshna, Nahant, Mass. 01908.
CONVERT any television to sensitive big -screen oscilloscope. Only minor changes required. No electronic experience necessary. Illustrated plans, $2.00. Relco -A22, Box 10563, Houston, Texas 77018.
INVESTIGATORS, LATEST ELECTRONIC AIDS. FREE LITERATURE. CLIFTON, 11500 -J NW 7th-AVE., MIAMI, FLORIDA 33168.
SENCORE, B & K Test Equipment Unbelievable Prices. Free Catalog and Price Sheet. Fordham Radio, 265 East 149th Street, Bronx, N.Y. 10451.
ELECTRONIC PARTS, semiconductors, kits. Free Flyer. Large catalog, $1.00 deposit. Bigelow Electronics, Bluffton, Ohio 45817.
METERS Surplus, new, used, panel or portable. Send for list. Hanchett, Box 5577, Riverside, Calif. 92507.
ELECTRONIC COMPONENTS-Distributor prices. Free catalogue. Box 2581, El Cajon, California 92021.
ELECTRONIC Ignition. Various types..Information 10d. Anderson Engineering, Epsom, N.H. 03239.
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o55u4.1r3'311Juaanlrteea$ad5dy95foo,rvbeloirsthhtainueglxe.cd.Ac&DoDnc:da.T,liebak.nt.dat5616o51nAlywait$th1$034995015.
REDUCEDeSUMMER RADIO- RECEIVER PRICES:
TsLttpKw$$3bRcchhoho2eea22aH3iermyranaks97o9Zmfnh-Mtveee95u0Ai,ecccAg..Hawar50toanhr-at,dzf/a00eneltdovyaUrt..raawialRnnnftcnLiiodpVyRARuolttteoghauNoEr3esgocurrucRr9sa/eclopesr.hs0eYdUch.dracadteRaot6/raonoUscsfgcAbrbo.ieoeRsinmu5t-ntemih8lSyRho4eyaoeIfPsenptc,sfo-hMietrn6u-btds5twyreHf0husi7aoinh1eg0uapzvt9uvt0o.irale-o5tpe0llJrmwaspdr.-wyeXl0hiiliatrscnKut,oie0udohstegspH.meuhCndx...znvWccstomo.iertau.nap.DyerlEbSistgrssculigvitote&.eooaanaea-nsllnnrrlnec.ea-sytdb,ddoDcl.c.ewoon.toisiar5ntvcvvngteg0loreIeyitcrnysr0rtrmCrtewtlysosdsduiihtli$voicma.tIrl5yCnaecolli1i1psbo9rHff90tzvih5zmT0ne9a5mepyo.7Tren%40raoluo7etstYdd00souo-,t,K only $275.00.
If you don't see It here, ask for It!
Or ask for the KIND of material you want. But don't
ask for a general catalog
. we believe that is
nonsense in surplus . we get new things in almost
erery day! We ALSO BUY! So tell us what you
hare. condition, and your asking price.
NEW SEMICONDUCTOR LIGHT EMITTING DIODES. Bright red lights replace light bulbs. Typical life 100 years. Operate'at 1.65 volts, 50 milliamps. Order 2 for $2.98 NOW. Data sheet and instructions included. Mon-
santo 'Company, Hobby Section, 10131 Bubb Road,
Cupertino, California 95014.
CONSTRUCTION PLANS: Laser ... $2.00. Investigation
aids-2 -FM microphone transmitters ... $1.00. FM tele-
phone Space
transmitter ...
monitor- missile
$2.00. tracker
... Sound telescope $2.00. Free
... $2.00.
equipment
and kit catalog. Howard, 20174 Ward, Detroit, Michigan
48235.
FREE ILLUSTRATED CATALOG!! covering wide range of low-cost stock business forms from 2 -Way Radio to TV Service. Write today. Free catalog; samples, too. OELRICH PUBLICATIONS, 4040 N. Nashville East, Chicago, Illinois 60634.
WOULD YOU SPEND 25d to save $25.00 or more? Citizens Band, AM and SSB 2-way radios, USA and export models. Send 250 for catalog to: BAGGY'S RADIO, 6391 Westminster Avenue, Westminster, Ca. 92683. Dealer inquiries invited.
JAPAN HONG KONG DIRECTORY. World products information. $1.00 today. Sekai Shogyo Annai, Hillyard, Washington 99207.
PRINTED CIRCUITS Quick. Free Estimates. Industrial Photo C-18, Oakhurst, N.J. 07755.
EUROPE'S top quality electronic parts, ridiculous prices. Catalog 35d. Electrovalue- America, Box 27A, Swarth-
more, PA. 19081.
TREASURE HUNTERS! Prospectors! Relco's new instruments detect buried gold, silver, coins. Kits, assembled models. Transistorized. Weighs 3 pounds. $19.95 up. Free catalog. Relco -A22, Box 10839, Houston, Texas 77018.
KITS dc power supplies, regulated and unregulated. Free
catalog describing 450 models professional designs at hobbyist prices. Techni -kit, Box 4517, Irvine, Cal. 92664.
OSCILLOSCOPE Dumont 322 -A, Dual -Beam, AC -DC, Perfect Condition, $235.00. Demers, 10355 Wells Ave.,
Riverside, CA. 92505.
NEW amazing telephone recorder automatically records every word each time your telephone is used. Only $24.95. Amplicom, 7153 Reseda, Reseda, CA. 91335.
RECONDITIONED Test Equipment. Reasonably priced, list available. Walter, 2697 Nickel, San Pablo, CA. 94806.
ELECTRONIC GOODIES, new guaranteed. Monarch KW SWR Relative Power Dualmeter. Antenna Bridge $16.45 postpaid. Quote industrial, amateur, CB. Madison Electronics, 1508 McKinney, Houston, Texas 77002.(7131 224 -2668.
SHUR E-A KG -Tu rner-Electro-Voice microphones.
Prices? Randall's, Box 8097, Milwaukee, Wis. 53223.
ELECTRONIC IGNITION $12.95. Include automotive model. EMP Co., Box 1047, Livermore, Calif. 94550.
INTEGRATED circuits, new series 74N at very competitive prices. Send for list. Marco Enterprises, POB 216,
Dayton, Ohio 45401.
ARROW SALES, Surplus Electronics, Seven Zero Four Nine, West Archer, Chicago, Illinois 60638. Write for Free Catalog.
FR-EE CATALOG-Loads of Bargains. R.W. Electronics, 4005 West Belmont, Chicago, Illinois 60641.
BURGLAR ALARM SYSTEMS. We manufacture intruder -fire detection systems, radar and perimeter types. Accessories available. Free Literature. Inquiries for dealer-
ship and wholesale prices must be on letterhead. U.S. and Canada only. Microtech Associates, Inc., Box 10147, St.
Petersburg, Florida 33733.
TOOLS-Woodcarvers Supply, catalog 25d. 3112 West 28th, Minneapolis,' Minn. 55416.
TELETYPE equipment and parts. New and used. Write: R.T.T.Y. Electronics, P.O. Box 655, El Cerrito, Cal. 94530.
ELECTRONICS ENGINEERING AND INSTRUCTION
- LEARN ELECTRONIC ORGAN SERVICING at home.
All Makes including transistors. Experimental kit troubleshooting. Accredited NHSC. Free Booklet. NILES BRYANT SCHOOL, 3631 Stockton, Dept. A, Sacramento, Calif. 95820.
_ELECTRONICS! Associate degree-29 months. Techni-
cians, field engineers, specialists in communications, missiles, computers, radar, automation. Start September, February. Valparaiso Technical Institute, Dept. N, Valparaiso, Indiana 46383.
WANT AN F.C.C. 1st CLASS LICENSE? WANT TO BECOME A DISC-JOCKEY? REI has a school near you VA approved call toll free: 1 -800-237 -2251 or write REI, 1336 Main St., Sarasota, Florida 33577. Florida Residents call: 1813) 955 -6922.
MEMORIZE, STUDY: "1971 Tests- Answers" for FCC First and Second Class License. -plus-"Self-Study Ability Test." Proven! $9.95. Satisfaction guaranteed. Command, Box 26348 -P, San Francisco 94126.
RECTIFIERS & TRANSISTORS Silicon Rectifiers
Ply 1 251 501 1001 2001 4001 6001 800j1000)1200
IA 1 -1.031 .041 .06) 081 .101 .141 171 .22
-1= 18A1.091..151 .191 .291 .391 -1 -1
-I 20A 1.231 -1
.591 .7511.1311.3511.7312.10
-I 40A 1.381
-11.3511.80!2.2512.7013:1513.60
Tophat, Plangelese. Pressfit. 3. 20. 40 Studs
Silicon Controlled Rectifiers
1500 PIV RECT.
- - - PRY
1
25 1
501100
1200
400
1
600
1
1A 1
I
I
I .301 .551 .85
STUD
7A I .111 .141 .201 .451 .30 11.20
1 AMP 18A"1 .151 .23 ! .351 .60 11.10 11.40
250 EA.
20A 1.18 1.32 1.45 1.70 11.15 11.95
Tophat Pressfit. 7 & 20 Amp Stud
Germanium Power Transistors
211456A2N457A-
40V -.25150W60V-.35
TO.3.7A
2N 458A-
2111021A-
80Y -.45 100V-.60
Silicon Small Signal NPN, TO -5
2N696 7/$1.00, 2N697 6 /$1.00, 2N699 5/$1.00
2N3053 Silicon, NPN 3/$1.00; 1N34A Diodes 100/
-3 $2.98; 2N1142 Ger. Hi -Freq. Amplifier 3/$1.00;
Thermistor Beads, 5000 ohm or 1200 ohm /$1.00;
Varicaps-27, 47,
Board 6" x 6" x
or 100pf,
1/16" -
1
4V -$1.25
oz. Copper
ea.; P.C.
-2/980;
Photo Cells, Herm. Glass, 5 Diff. for $1.00; IN661
Silicon Assort.
Switching 25/$1.00,
50/$3.49- 100/$4.98; R.F. Coil I.C. 10.5- 15/$1.00. Epoxy Diodes,
200 MA, Computer
3D0i0o0de-P5iv04/9$3f,.4690-010009/8$04. .98IN;65P8.CS. iliCcoonn-
nector 15 Contact 2/$1.10. Trim Pot 1K 49c
ASSORTMENTS
Precision resistors film
Precision resistors wirewound Ferric Chloride Etchant, 24 oz. bottle Relays 6 different types Terminal lugs, assorted
Tie lugs, assorted Push button switches, on -off, panel Pots. 2 -4 watt, different
58 /$1.00 40/$1.00
$1.49 6/$1.00 200/$1.00 50 /$1.00 6/51.00 10 /51.00
Electrolytic capacitor 1500 MFD
25 WVDC
98c
21/4" 8 ohm speaker....$1.25
Min. order $3.00; send sufficient postage, overage refunded; fully guaranteed; free catalog. 25% down on COD's.
R. E. GOODHEART CO. INC.
Box 1220 -A, Beverly Hills, Calif. 90213 Phone: Area 213 272 -5707
EUROPEAN wholesale new products catalog $1.00 refundable. Deecow, P.O. Box 9308, North Hollywood,
Calif. 91609.
GENERAL SALES CO.
254 E. Main St.
(713) 265-2369
Cluts, Tex. 77531
CIRCLE NO. 139 ON READER SERVICE PAGE
U.S. GOV'T ELECTRONIC SURPLUS
Nattonally Known -World Famous SURPLUS CENTER otters finest, most expansive, Government Surplus electronic units and components at a fraction of their original acquisition cast.
IBM COMPUTER POWER SUPPLY
( ITEM 022 -8881 - - Expensive. regulated unit. Fine for college labs, research ec service shops, etc. Pure DC over awide range of 48, etc. mine`range of AC voltages available.
Finest transformers. filters. transistor load
regulation system. Independent or line voltage fluctuations. Conlalns Ibv separate recttfler
systems. tall
Anil d
Is wbhoiclah
can
Mrwsithitolrut
small made
can
he by-passed. Duo and
diagrams fur-
li" nished. 311" x
o 10" (I_S tbs. 1
r $24.95 Cost 'I
Over 3500.00 ONCE -IN -A- LIFETIME SPECIAL
I t
:*
ì(d1
~ J" !.
BURGLAR -FIRE ALARM SYSTEM
ç
At s
-
,í
)
ß`$Q$29.95
( ITEM 01135 -A ) - -
Dual alarm
gives gaming of lire cc weak -m
Operates
115 -A IC. Control it, 2-
xalde flash fire, 2 -me an column, 3 -door
w" iirdeo,wrnalraucrtuliamto,Srs.,a'j'axlar7m'i'
bell. Inn h. .a 3 ".!716,.1
STANDARD DIAL TELEPHONE
telep(hoITneEM.m0e11a5s )
- used
Standard. throughout
ml
l'.54m Altrac-
polished black, like new condition. I'ae as
etexmte. ntsaiolnlpphhpionhnwsoetnssreutcottgiooentphsreivarareftoerfasmloyiscstahelemdisn- teowrrcl.ocmo9n1nsbyessc.-t
,-`.N
Original r.os,
324.50 $7.49
y STEP -BY -STEP TELEPHONE SWITCH
-i. Ik .cuIrlI,T.EGMrea0t1
-808 ) - 4maeing vpertmenlal Item.
telephone nhen used
selector with ion-
t' 1 ke
telephone drat .111 select any number from ó intercom or encore system. Use to will on
to 100. remote
('C
¡y n.
nl Ç'
$6.29 ss IT ". lights. Klan motors, etc. Complete with contact bank.
o 6" a 5 116 Ihs. I Cost Over $90.00
TIB'F
sa
.
Syr ".
telephone dial foe use sins above switch.
Order as I Item .190 1
$1.97
eeeq!.!
MAGNETIC DIGITAL COUNTER(12to18 -VDC)
At '.. ' 'V;Yb A 1
, r, ll o.I
l'
( ITEM 021-909 ) - cue to count electrically.
t
minwr rd time`hsaa
opened
xIi business
10
etcl.osbetiátlol nInceouxMntutumnI itfor xt h epat
aboraand will
100
4- I4
".
0°,',...n".1 rich $1.99 TOce $4.99
TYPICAL BUYS FROM OUR 1971 CATALOGS
8 10.00 BIOIAO 8 15.00 5200.00
I10 -Volt OPOT Relays Regulated Transformer, Wide Range 20 -Relay Telephone Panel Gyroscope, Twin Rotor, 24V
$1.69
$14.91
$4.39 $9.89
AC PROGRAM TIMING CLOCK
ITEM 01581 -- 7e,m1, t,3 -I Iv
f(or
on ant
í. w
enudo radio, co
lnr&!i!'.n5
sigInlia.lincgVli.penswn&oprekrm%biNtroeOaNhka..fsitg"sIigkssinl,ie.i,.:
be multiple programmed. 15«mti hic r I 8 14.1
en
óli i$ïö.lio
$15.75
: l0
.
._15,743,,
-_
SNAP AROUND VOLT- OHM -AMMETER
s' ,
( ITEM 021E441 - - nleasarec AC current without
opemng the line. Simply press handle and snap the probe
around the conductor. Reads currents from .23 to 125-
-
l
amps. Heads voltages to 300. reads ohms p m Soo. Test
m,Una. appliances. etc. Three current ranges,
agee ranges. wllh ease. lest leads. L''sj' x 3" l'a
volt--
SPECIAL SALE
Correspondence Course In
J (. Ree. Price 539.95
2 lbs. l
ELECTRICAL ENGINEERING
I% $8.79 Prrpa,d m U.S.A.
$10.79 Outside U.S.A.
-- E( ITEM CA Gm I Obtain Iechn,ral training at low cost, Lincoln
ngineeRRring School has suspended its Correspondence Courses because
of
vailable. abuts* thou the
ss,ostr.ts,.of
13 lesson books, Rook describing
are
examinations goading service. The lcours'escon-
each p
with associated winning Home
exams and .standard anExperimental laboratory
lammhed at no , aim i flat.
RUNNING TIME METER
( ITEM 52 IBA I - - Regard number of opp-
c'
esratitningg hour, of electric light-, and electrical
such as refrigerators, fumacea c.
Reeodn total hears. ebs and hundredths pup
$4.39 to 9,990.90
sier 4'i:'x V'
hxolu'zrs'..
For 115-volt. 60-cycles. Shipping weight 21hs.
-
,
Cost ova 329.00
COMPUTER TRANSISTORS ON HEAT SINKS
IBM Computer Qualify Units
( 022 -828) -- Unit consist: of one 150-
watt power transistor on heavy, ribbed,
aulsuems,inuImI
heat lb./
sink.
Many
experimental
$1.99 emit Gov't Over 310,00
(
wall
022-910 power
1 - - Unit transistors
consists 2 pots
or
two 130several
.g
L
1
diodes, capacitors, resistor, etc. n heavy. ribbed aluminum heat sinks. Ideal for use as motor speed control. 1 41ós.1
I
-
$4.91 Coat Gnat Over 335.00
..
+G?0-
`o.,paow
ALL ITEMS SNIPPED F.0.11. LINCOLN. NEBR.
Order Direct From Ad. Money Rack Guarantee.
''I.
SURPLUS CENTER
DEPT. EW -071 LINCOLN, NEBR. 68501
July, 1971
f INTEGRATED CIRCUITS RECTIFIERS
f SEMICONDUCTORS TRIACS
BCD COUNTER KIT
Consisting of:
1
2 2
1
----PS7S4Cei 7tI i6cbooofnaICriddn'sisot1dr2ue7sc0tio7ns
Wtiohnesn, athsissemkbitledwilbl ycoenucnltospeudlseinsstfrruocm-
0 -9 in BCD. These ndeecstieredd.in Esxearimespleto, count to 99. three
bctowoaourdnstbcoaasanrdhbsigehcwoanils-l to 999 etc. $6.95
tEbomrnaiRedec9tihrs0eo0cdotsfioTnRattholIeGGtEtrrbRiigeggsgteeDrrIaOnDddSEioCSdR.ec4'ssh/$eTa1hp.aea0ensrs0deet
TIS 43 GENERAL
PURPOSE UNIJUNCTIONS
2N 3819
s.50
N-Channel FET's2N4303 P channel
FET
with.45
QMS of 2000 uohms
$ .95
TRIACS
PRV
lA
10A
15A
100
.40
.70
1.0o
200
.70
1.10
1.40
300
.90
1.35 1.60
400 1.10 1.60 2.20
500 1.50 2.00 2.80
LIGHT EMITTING DIODES (LED's)
Infra red spectrum
OR
visible
Photo detectors for each
$1.50 ea.
..$1.00
TTL IC SERIES (DIP)
...1 7441
7474 7475 7476 7490
BCD Dual
quad
DFBeliicspitmabFallleopDLeactocdher
Dual Mast -Slave Decade Counter
JK
FF
7492 7493
4DiBviidt eBBinyarTy wCeoluventer
.
.2 00
85
..1
70 00
1 85
..11
85 85
Silicon Power Rectifiers
PRV
3A
30A
12A
100 .09
30
.50
200 .16
.35
.80
400 .20
.45 1.20
600 .30
.70 1.50
800 .40
.85 1.80
1000 .55 1.10 2.20
NIXIE TUBES
Similar to 8754 with
socket
$4.75 ea.
Terms: FOIS Cambridge, Mass.
Send
Money Order.
ostage.. Average 1/t Ib. No C.O.D.'s.
MinimerumpaOckrdaeger
$3.0R0ated companies 30 days net
DECADE
C1111----o77N7n444isx47i9si15e0tingtuboef
COUNTER Ac socket
KIT
Specially priced at $9.95
709C OPER AMP SE 501 VIDEO AMP. 741 OPER. AMP. 723 VOLTAGE REGULATOR
Controlled Avalanche Rectifiers 1 AMP.
or
10 .06
200 .07
400 .09
600
.11
800
.15
1000
.20
$$11..Ó2Ó5 $1.25 Epoxy
Silicon Control Rectifiers
PRV 3A 7A 20A 70A
So .25 .28 .60 100 .30 .38 .85 3.50 200 .50 .60 1.10 6.50 300 .60 .68 1.30
'400 .70 .75 1.50 9.50
500 .80 .85 1.70 600 .90 1.20 1.90 11.00
Send for our Latest catalog featuring Transistors and Rectifiers; 325 Elm St., Cambridge, Mass.
ALES
Post Office Box 74B
Tel. (617) 547 -4005
-CIRCLE NO.
121 ON -
READER
SERVICE
PAGE
FCC LICENSE THROUGH TAPE RECORDED LESSONS. Radio License Training, 1060D Duncan, Manhattan Beach, Calif. 90266.
LEARN DIGITAL LOGIC and integrated circuits. Free brochure. Performance Enterprises, Inc., 4706 NE 12th Ave., Fort Lauderdale, Fla. 33308.
DEGREE in Electronics Engineering earned mostly by correspondence. Free brochure. Dept. G -9, Grantham School of Engineering, 1505 N. Western Ave., Hollywood, California 90027.
... FCC Type Exams guaranteed to prepare you for FCC
3rd, 2nd, and 1st phone exams. 3rd class, $7.00; 2nd class, $12.00; 1st class, $16.00; complete package, $25.00. Research Company, Box 22141, Tampa, Fla. 33622.
MATHEMATICS, ELECTRONICS. No contract, no obligation. Satisfaction guaranteed. Free brochure. Indiana Home Study, P.O. Box 1189, Panama City, Florida 32401.
SERCOLAB. Science Fair Projects, amazing kits. P.O. Box 78E, Arlington, Mass. 02174.
FCC Questions on 1971 First and Second Class Exams, with answers. Guaranteed Results. $8.95. Electronic Tutoring, Box 24190, Cleveland, Ohio 44124.
TUBES
TUBES- Lowest prices. Foreign -American. Obsolete, receiving, special purpose, transmitting tubes. Send for tube, parts catalog. United Radio Company, 56 -E Ferry St., Newark, N.J. 07105.
TUBES, SEMICONDUCTORS, ELECTRONIC EQUIPMENT & COMPONENTS. Quality merchandise only! Serving engineers, Purchasing Agents, TV/Hi -Fi Servicemen and Hams for 20 years. Write for Catalog or call 212 -WA 5-7000. BARRY ELECTRONICS, 512 Broad way, New York, N.Y. 10012.
RECEIVING & INDUSTRIAL TUBES, TRANSISTORS, All Brands-Biggest Discounts. Technicians, Hobbyists, Experimenters- Request FREE Giant Catalog and SAVE! ZALYTRON, 469 Jericho Turnpike, Mineola, N.Y. 11501.
TUBES -364 each. Year guarantee. Tuner Cleaner $1.00.
Free catalog. Cornell, 4213-W University, San Diego, Calif. 92105.
DO -IT- YOURSELF
PROFESSIONAL ELECTRONICS PROJECTS-S1.00 up. Catalog 25d. PARKS, Box 25665A, Seattle, Wash. 98125.
RECORDS
POPULAR organ albums factory direct. Concert Recording, Lynwood, Calif. 90262.
PLANS & KITS
INTEGRATED CIRCUIT KITS-Free Catalog. FRAZER & ASSOCIATES, 3809 Surfwood Road, Malibu, California 90265.
CONVERT your scope. Dual trace FET switch, $10.00. Trigger-sweep $24.95. Kits include semiconductors, boards, instructions. Hamlin Technical Products, Box 901, Cupertino, Calif. 95014.
... IMPOSSIBLE? BARGAINS IN SURPLUS
ELECTRONICS (AND OPTICS)
D TACHOMETER /DWELL METER KIT
$6.50
Obviously the only way we can
provide an astounding value like thi é is by utilizing surplus parts. The 270
. 8B B
meter movement, surplus of an auto manufacturer, is worth several times i 8
, )4
required1eC our kit price alone. But we also s
B
include all the components
r
to build a fine auto Tach /Dwell
Meter including transistors, zener
diode, switch, printed circuit board and full instructions.
D LOWEST COST DIGITAL COUNTER KIT
$6.50
Here is another astounding surplus bargain kit. To the best of our knowledge this is the lowest cost decade counter complete with readout anyone has offered yet! We supply two M.S.I. integraged circuits, a 7490 decade counter, and a 7441 count of 10 decoder, 10 light bulbs that operate directly from the 5 volt supply, a printed circuit board, and full instructions for building a decade counter. Of course several of these counters can be cascaded for as many decades as you wish.
D A DIGITAL COUNTER KIT
$7.50
Same as above but with 74130 bidirectional counter for counting forwards or backwards. Used in preset counting, encoders, etc.
D NIXIE READOUT DECADE COUNTER
$11.75
Same as above but nixie readout instead of lamps. Includes B5750 nixie, which solders directly on P.C. board. Add $1.00 for up /down option.
D IEE PROJECTION DISPLAYS
S7.50
This decimal readout jests numbers onto a plastic sccrreeneen. Can easily be viewed from many feet away. Original cost $25.60. Used in perfect condition.
D PRINTED CIRCUIT BOARD KIT
$5 -50
With 7490 decade counter, 7441 decoder and transistors to provide decade counter and driver for IEE readout above.
D B5750 NIXIE, NEW, ORIGINAL, PKG.
$6.00
D 4.5 VOLT 100 MA MINIATURE WIRE
LEAD BULB
10 for $2.00
D GIANT 80 PAGE ILLUSTRATED CATALOG
.25
Free with any order or send .25 cents
- Charges Welcome $10.00 Min.
BankAmericard Mastercharge ALL ITEMS POSTAGE PAID IN THE U.S.A.
B. & F. ENTERPRISES
Phone 617 532 -2323 P.O. Box 44 Methane. Massachusetts 01937
CIRCLE NO. 148 ON READER SERVICE PAGE
1 LIBERTY PAYS MORE!
WILL BUY FOR CASH
ALL TYPPEESS::
* ELECTRON TUBES * SEMICONDUCTORSS * TEST EQUIPMENT
* Military Electronic Equipment
WIRE -WRITE -PHONE COLLECT! We pay freight on all purchases-
LIBERTY OFFERS MORE!
PRESTEL FIELD STRENGTH METER
(Model 6T4G'! .:w;
Only
$12000
F.O.B. New York
* Never Anything Like It!
* 1 -Man Can Do A Better lob than 3 in the * Same Time!
A Gold-Mine for Antenna Installers!
Calibrated from 40 to 230, and 470 to 860 in 4 Bands Megahertz, from 10 to 50,000 Microvolts. Nothing makes it easier to properly and speedily find the correct place to install iV. FM and Communication Antennas. You can measure and hear the signals with this 41/1 volt battery economically powered unit.
LIBERTY ELECTRONICS, Inc.
548 Broadway, New York, New York 10012
1 PEP i Phone (212) 925 -6000
CIRCLE NO. 132 ON READER SERVICE PAGE
Dollar Sale
EACH PACKAGE
MONEY BACK GUARANTEE
1 AMP
Silicon Rectifier
Choice of Package
Bullet-Glass- Min -Metal
20 -50V 17.100V 12 -200V
54--810000vv 3.1200v
3 AMP
1150-.5100V0V
13
4.600V 3 -800V
8 -200V
2 -1000V
5 -400V
1 -1200V
so1-loAoMt'P GsLiA:iS.0S0
000vR 10/01.00
15
AM!MP X'.
s -50V
1T4/,1s7.rP.0R0[SFIT
rpMP5S.1CoRoFyLA1N0G/'5E1P.0A0CKAGE
2 AMP BULLETS
12 -200V $1.00
180--S8O0O0VN
$1.00 $1.00
CIRCUIT BOARD SPECIAL
A- Approximately 200 diodes-7 transistors-
............. over 50 resistors complete with hoard! -$1.25
4P0lasAtimc pl.owStpuodw2e4r tVra. ns..istors PNP No
7 Test 25
ffoorr $$11..0000
PRV 50V
1001.9
200V 400V 600V 800V
FULL WAVE BRIDGES
2Amp 13Amp SAmp
1.25
1.35
1.50
1.50
1.60
1.75
1.75
1.85
2.00
2.00
2.10
2.25
2.50
2.60
2.75
3.00
3.10
3.25
11OAmp 1.70 1.95 2.20
2.45_ 2.93 3.45
SILICON CONTROL RECTIFIERS
PRV
1 AMP
3 AMP
7 AMP
50
.20
.25
.30
100
.25
.30
.35
200
.40
.45
.50
403000
.60 .75
.70 .85
.80 .95
500
..
..
1.00
600
..
..
1.30
TRIACS
PRV I 1 AMP 3 AMP 16 AMP 10 AMP 115 AMP
100 I .40
.50
.75
I
1.00 I 1.20
200
.65
I
.75
1.00
I
1.40 I 1.80
300 1.00 I
1.10 I 1.25
1.90 2.20 I
400 1.30 I
1.40 I 1.80
2.30 I 2.60
500 1.60 I
1.80 I 2.10
2.75 3.10I
NO SALES TAX -WE PAY POSTAGE
OTHER PRODUCTS ON REQUEST
PARK ELECTRONIC PRODUCTS P.O. Box 78, N. Salem, N.H. 03073
603- 893.0276
CIRCLE NO. 127 ON READER SERVICE PAGE
WANTED
QUICKSILVER, Platinum, Silver, Gold. Ores Analyzed. Free Circular. Mercury Terminal, Norwood, Mass. 02062.
QUICK CASH ... for Electronic Tubes, Semi-conductors,
Equipment (Receivers, Transmitters, Scopes, Vacuum Variables, etc.) Send lists now! Write: BARRY ELECTRONICS, 512 Broadway, New York, N.Y. 10012 1212 -WA 5- 7000).
TAPE AND RECORDERS
OLD Radio Programs on tape. 6 hours for $8.00. Catalog 50d. Don Maris, 1926 Cherokee, Norman, Okla. 73069.
STEREO TAPE TRANSPORT -7" reel-2 speeds-pause
control -made for famous manufacturer -50 to 15,000 Hz-with rec/play and erase heads, without case. Send
m.o. or check for $19.50 to Alsheimer Audio Electronics, 218 Columbia St., Utica, N.Y. 13502. $2.50 for prepaid shipping and insurance.
STEREO TAPE RENTAL for particular people. Free catalog. Gold Coast Tape Library, Box 2262, Palm Village Station, Hialeah, Fla. 33012.
RENT 4-track open reel tapes-all major labels-3,000 different-free brochure. Stereo -Parti, 55 St. James Drive,
Santa Rosa, California 95401.
BARGAIN MUSIC, Tape, Equipment Catalog 250. Saxitone, 1776 Columbia Road, Washington, D.C. 20009.
TRADE stereo tapes. $1.25 each postpaid. Minimum three. Tapetrade, Box 2181, LaJolla, Calif. 92037.
VIDEO TAPE, 1 inch. x 1 mil x 1700 feet. Used. On computer reels. $12.00 each. Lahill, P.O. Box 656, Martinsburg, W. Va. 25401.
RECORDING TAPE made by top American manufac-
turer, guaranteed not "seconds" or "white box" 2400'
mylar, $2.29; 1800' mylar $1.69; 1200' acetate $0.79. Send for information and quantity pricing. Alsheimer Audio Electronics, 218 Columbia Street, Utica, New York 13502.
RECORDING TAPE. Most brands available at lowest prices anywhere. Recording Tape Wholesalers, Box 844, Orange, Conn. 06477.
OLD Radio Programs. Catalog $1.00 (Refundable). Radio Vault, 1533 50th SW, Wyoming, Michigan 49509.
HIGH FIDELITY
HI -Fl EQUIPMENT-GET Our "ROCK BOTTOM" prices on NAME BRAND amplifiers-tuners-tape-recordersspeakers FRANCHISED -60 YEARS IN BUSINESS. Write for this month's specials -NOW! Rabson's 57th St., Inc., Dept 569, 119 W. 57th St., New York, N.Y. 10019.
LOW, LOW quotes: all components and recorders. Hi -Fi, Roslyn, Penn. 19001.
HI -Fl components, tape recorders, sleep learning equipment, tapes. Unusual Values. Free catalog. Dressner, 1523 R Jericho Turnpike, New Hyde Park, N.Y. 11040.
DIAMOND NEEDLES and Stereo Cartridges at Discount prices for Shure, Pickering, Stanton, Empire, Grado and ADC. Send for free catalog. All merchandise brand new and factory sealed. Lyle Cartridges, Dept. E, P.O. Box 69, Kensington Station, Brooklyn, New York 11218.
STEREO speaker enclosure literature for custom Hi -Fi enthusiasts, $1.50. Richard Marano, 44 St. Nicholas Avenue, Brooklyn, New York 11237.
HYPNOTISM
SLEEP Learning. Hypnotic Method. 92% effective. Details free. ASR Foundation. Box 7021 EW, HC Station, Lexington, Ky. 40502.
FREE Hypnotism, Self- Hypnosis, Sleep Learning. Catalog! Drawer H400, Ruidoso, N.M. 88345.
GOVERNMENT SURPLUS
JEEPS Typically From $53.90 ... Trucks from $78.40 ... Boats, Typewriters, Airplanes, Multi meters, Oscillo-
scopes, Transceivers, Electronics Equipment. Wide Variety, Condition. 100,000 Bid Bargains Direct From Government Nationwide. Complete Sales Directory and Surplus Catalog $1.00 (Deductible First $10.00 Order.) Surplus Service, Box 820 -K, Holland, Michigan 49423.
AMAZING SURPLUS BARGAINS. Government Surplus never before offered, for Pennies on the Dollar! Hardware, Tools, Motors, Electronics, Optics, Hobbycraft! Illustrated $1.00. Refundable. Surplus World, Box 785, Rochester, N.Y. 14603.
GREGORY ELECTRONICS
Your Best Buys In
QUALITY USED FM 2 -WAY RADIO EQUIPMENT
BIG SAVINGS
ON
MAMMOTH RCA
EQUIPMENT
PURCHASE
RCA LOW BAND
CMFT 50 27 -54 MHz, 50W, Checked out,
with accessories. Transistor power
supply; ceiver
partially
transistorized re- $1 78G
Sreacmoendiatisonaebdo,vree.pabiunttefdu-lwly itfhactnoerwy
accessories
$228O
RCA HIGH BAND CtarcaMcrCessTisstoo3rri0iez.sed30Wr,ecCeihveecrk, edcomouptl,etepa$rt11iaLvll08y
60 Watts
$208
Same as above, 30W, conditioned, repainted,
but fully with new
faacc-to$r2y 0re8-
cessories
60 Watts
$248
UHF 450-470 MHz CMUE 15, 12V/15W,
transistor
sonies
power
supply
with
acces- $7908
Same as above, but fully factory recondi-
1f0 tiored, with new accessories, nan- $ 1 8
row banded
RCA CMU 15B 6/12 volt, MHz less accessories
450470 $2v8
accessories (sold separately) $20
SEND FOR NEW 711/2 CATALOG
s GREGORY z
GREGORY
ELECTRONICS
CLLCTAONrCS.... CORPORATION
249 Route 46, Saddle Brook, N. J. 07662 Phone (201) 489-9000
CIRCLE NO. 136 ON READER SERVICE PAGE
PERSONALS
MAKE FRIENDS WORLDWIDE through international correspondence. Illustrated brochure free. Hermes, Berlin 11, Germany.
PHOTOGRAPHY -FILM,
EQUIPMENT, SERVICES
SCIENCE Bargains- Request Free Giant Catalog "CJ" -148 pages -Astronomical Telescopes, Microscopes. Lenses, Binoculars, Kits, Parts, War Surplus bargains. Edmund Scientific Co., 300 Edscorp Bldg., Barrington, New Jersey 08007.
MAGAZINES
OVER 2,000,000 Backdate magazines! Specify needs. Midtown, Box 917EW, Maywood, New Jersey 07607. JAPAN PUBLICATIONS GUIDE business, pleasure, education $8.00. INTERCONTINENTAL, CPO 1717, Tokyo 100 -91.
EDUCATIONAL OPPORTUNITIES
LEARN WHILE ASLEEP. Hypnotize! Strange catalog free. Autosuggestion, Box 24 -ZD, Olympia, Washington, 98501.
INVENTIONS WANTED
PATENT Searches including maximum speed, full airmail report and closest patent copies, $6.00. Quality searches expertly administered. Complete secrecy guaranteed. Free Invention Protection forms and "Patent Information." Write Dept. 23, Washington Patent Office Search Bureau, 711 14th Street, N.W., Washington, D.C. 20005.
BUSINESS OPPORTUNITIES
I MADE $40,000.00 YEAR by mailorder! Helped others make money! Start with $10.00-Free proof. Torrey, Box 318 -N, Ypsilanti, Mich. 48197. FREE BOOK "999 Successful Little -Known Businesses." Work home! Plymouth 445 -G, Brooklyn, N. Y. 11218. $200.00 DAILY In Your Mailbox! Your Opportunity To Do What Mailorder Experts Do. Free Details. Associates, Box 136 -EW, Holland, Michigan 49423. MAKE $1.00 Per Sale selling engraved metal Social Security plates. Free Sales Kit. Engravaplates, Box 10460 -7507, Jacksonville, Florida 32207. FREE CATALOGS. Repair air conditioning, refrigeration. Tools, supplies, full instructions. Doolin, 2016 Canton, Dallas, Texas 75201. JAPANESE Electronics New Products Monthly! Specimen copy $1, deductible. Dee, P.O. Box 9308, North Hollywood, Calif. 91609. START small, highly profitable electronic production in your basement. Investment, knowledge unnecessary. Postcard brings facts. Barta -GRA, Box 15083, San Francisco, California 94115.
RUBBER STAMPS
RUBBER Address Stamps $2.00. Signature $3.50. Free Catalog. Jackson's, Box 443 -G, Franklin Park, III. 60131.
PRINTING
.411111I.
It's The Biggest! It's The Most Popular PENNY SALE IN THE INDUSTRY!
nE CENT
"EYE SEE" BONANZA
'rh ' ec
BY
POLY
PAK
aN
sheers Lowest Prices In U.S.A.
gtao
Buy ONE at the special "Sale"
Type
Description
Each 2 for
price get the SECOND for
SN7400N SN7402N SN7410N SN7420N SN7430N SN744oN SN7441N SN7460N 5N7473N SN7474N SN7475N
Quad 2 Input NAND Gate . . $0.88 $0.89
Quad Input NOR Gate
.88 .89
Trip :3 Input NAND Gate ..
.88 .89
Dual 1 Input NAND Gate .
.88 .89
Input NAND Gate
.88 .89
Dual 4 Input NAND Buffer
.88 .89
I3C'l) -to-Nixie Driver
3.95 3.96
Dual .1 Input Expander
11u:ó
Dual
.1"D-E"
Flip Flop Flip Flop
.88 .89 1.I9 1.20 1.19 1.20
Quad Latch.
2.99 2.96
SN7481N SN7490N SN7491N SN7492N 9874938
only ONE CENT!
16 Bit Memory Decade Counter R Bit Shift Register Divide By Twelve Counter .1 Bit Binary Counter
4.50 4.50 4.95 4.95 4.95
4.51 4.51
4.96 4.96 4.96
GENERAL ELECTRIC
3.5 WATT AUDIO
PA263
0n1y $3.95
AMPLIFIER 3 for $10
D3mh0eeoVanlivtoessri8usn.pk3psS.l;y5te.mrweiHocaritgotpsh-hmocsnoineoninsti,snsiuittziaovepui:tesy.,3. /1F80Mz.wto+aA/tMt1s.x6
peak. With 1/2". 9 to ohm. For TV, servo.
FAIRCHILD IC "AMP"
Any 3 10% Discount!
Type
Description
709 Operational 710 Ili Speed Diff.
711 Dual Comparator
Each .88 .88
.88
723 V. Regulator .
741 Fret. ('amp 709
2809 Dual 709
2747 Dual 7 t 1
.
.
.
1.19 1.50 1.50 1.98
908 Full Adder
909 Buffer
Your Choice 1pf1
912 Half Adder 913 Shift Register
3 for $1
915Dual 3 In. Gate
- !
4
2N4409 Nixie tube drivers
-10 lAmp 800 piv silicon rectifiers
- [-I 8 lAmp 1000 ply silicon rectifiers
1.011
1.00 1.00
LIGHT EMITTING DIODES
$1.50 Any 2 for $2.69
E Visible LED " brite red"
[LÍ ,
Visible "brite red" sensor* Invisible infra -red LED
EJ Invisible infra-red sensor*
.
With built-in Darlington amplifier.
10G Catalog on Fiber Optics, 'ICs', Semis, Parts
Terms: Phone
Retail:
add postage. Rated: net Orders: Wakefield. Mass. 211 Albion. St. R'akfield,
30, cod's (6171 245
Mass.
23%. -3929,
POLY PAKS P.O. BOX 942 W LYNNFIELD, MASS 01940
CIRCLE NO. 125 ON READER SERVICE PAGE
MOTOR SPEED & LIGHTING CONTROL
BUSINESS CARDS, Envelopes and Letterheads. Free Samples. Stewart Printing, P.O. Box 19284, Dallas, Texas 75219.
TREASURE FINDERS
FREE: Jetco Electronics free 24 page treasure finder catalog. Find metals, minerals, gold, silver, coins, and relics, Jetco, Box 132EW, Huntsville, Texas 77340.
MUSICAL INSTRUMENTS
8 Push button selected controls, stop & start indicator lights. Overrun of famous blender manufac-
turer. Used for controling speed of drills, saws, fans, lathes, lighting, etc. Controls up to 1500 watts.
Stock No. H5002-ready to use .$3.95 ea., 2/$7.00
Stock No. H5003- slight factory seconds, easily re-
paired
$2.95 ea., 2/$5.00
Wiring diagram furnished.
30% DISCOUNT name brand musical instruments. Free catalog. Freeport Music, 127 -L Sunrise Hway, Freeport, N.Y. 11520.
AUTHORS' SERVICES
AUTHORS! Learn how to have your book published, promoted, distributed. FREE booklet "ZD," Vantage, 516 West 34th St., New York 10001.
MAGNETS
MAGNETS. All Types, Specials -20 disc magnets, or 2
stick magnets, or 10 small bar magnets, or 8 assorted magnets, $1.00. Maryland Magnet Company, Box 192 -E, Randallstown, Maryland 21133.
MISCELLANEOUS
WINEMAKERS: Free illustrated catalog of yeasts, equipment. Semplex, Box 122 -76, Minneapolis, Minn. 55412. WINE Recipes and Catalog, 254. Country Winemaker, Box 191E, RFD 1, Mattapoisett, Mass. 02739.
HONEYWELL COMPUTER BOARDS
Honeywell Computer boards, 41/ "x12", Transistors, diodes, zeners, capacitors. precisio resistors, heat sink, trimmers, etc. 2 different boards $1.00. 3 lb.
Stock No. H9082
Honeywell Boards 51/2" x 8". Loaded with late no.
transistors, diodes, resistors and capacitors. 2 dif-
ferent boards $1.25. 2 lb.
Stock No. H9094
COMPUTER GRADE CAPACITORS
H2049 3500 Mfd. 55 volt 4,/4" x 13/4" $.65 ea., 5/$3.00
H2062 40,000 Mfd. 10 volt 3" x 4t,4" Brand new $1.25 ea., 6/$7.00
$1.00 FREE WITH $10.00 ORDER MINIMUM ORDER $3.00
Lots of other items-send for free flier; all merchandise fully guaranteed. Please include postage; excess will ba refunded.
A DELTA ELECTRONICS CO. BOX 1, LYNN, MASSACHUSETTS 01903 CIRCLE NO. 141 ON READER SERVICE PAGE
RCAF Genuine
Watches
lir Gov't issue, used, guaranteed OK $20. ea. OMEGA models, only $25.
Projection type decimal counting units 0 -9 digits.
From used eqpmt. $6 ea
SOLID STATE LAMP DRIVER completely wired with plug for use with above DCU or any similar DCU. A $50.00 value for only $3.50
'c
EJ :Julli 1 ,
LjL,'
Wired memory horn
UNIVAC computer 2640 byte on plug -in
board .Exlnt cond. $10
DIP PACKAGE IC brand new 350 ea. or
,
$3.50/12. 7400- 741)1 -7402-
7410- 7420 - 7430 - 7440 -7451-
7453- 7454 -7460. The Following
are $ 2.50 ea. 7441- 7475 -7490- 7493 -74121.
FIBRE OPTICS the most comprehensive list
of FO material available.. face plates, jewel-
ry, light pipes, coherent peepscope, light
sources, magnifiers, circle to line converter,
lamp kits.
Send For special listing.
METAL LOCATORS, become a millionaire, find jewelry, gold, silver, lost treasures.
Send for special sheet.
Send 25% for Surplus Catalog.. JOHN MESHNA JR. ELECTRONICS
P.O. Box 62 E. Lynn, Mass 01904
CIRCLE NO. 129 ON READER SERVICE PAGE
KEEP PACE WITH SPACE AGE! SEE MOON SHOTS -LANDINGS, SPACE FLIGHTS, CLOSE-UP!
='e AfMorMFIUNNG. STSUCDIYENorCPEROBFUITYS
FREE
CATALOG!
LOW COST TREASURE FINDER
Discover the of treasure
fhuunntianngd
profit inex-
cmmSotouescttlaltkyil--paNeudxord.tprosa7s1etco,i3r9cep5fulfAiaitcsrKityei,nccyw.heaingNdholte, tpffmmmjbbtaruerdaenaeeancdieiaaycnfrnanntitnitnekssnaohecessdgi.yglrrcihe,vulasaaorie,tcrldnlnmlosdseyeegt.r.Gsmehjt.eedcurwowcfbeeasrntadaiRieomormDt.tolmertrezpA.smyi.-e.qgsM)f$,fweiltor1nuidimoArodm4nsiituosare.rdgr9pkitlntaejeiuanr5suhsnddselciasis-csdhtswtiaPiahdsitooroabpnit9eeouetobotdlVnghlesase-.rr,
EMOTION METER "TESTS" YOU
AdRlacctmriienahekoemseudvaenvpnsniaseaocetzg.alednilensEssagesiabncttshyacdhiy(ntaunliieicdtroce.taadohtbtteaoeerwdNnndues.ehgysaeteeelee.llstdicyhrekltSMemeeoeisersnreionw,smaftstiasoaeiootvudtrmynvnikoirvpcesaeosr-ee-e-l.s-
atttipiiinbaovotlrneneetnns.ieedossear.sdsUkIunsendntideqrcfipau.cv.eeatlnony9rddavsb1fol0ibenor-a)not.teeztren.pErqtyrefuefr,eesttscaaec---itonmmpeln. t,inesdtrusc.ation. Great fun at
Stock No. 41,422AK
$15.00 Ppd.
3- CHANNEL COLOR ORGAN BARGAIN!
Ppd. phone plag. 51/4" x Grp" cord. Stock cNo. 71,223AK
xInc2l1u/Cuet(ptlttCh2dioewii5nfoan"gvirhnpf0nu.rdeiuhier-ec0tsgaiist2cqyces,et1LutueatwsW5matactpc0oltilho.artoclirwshemeu<sWnuobypmlsituiprsetolr.gbphr.erirloitgeehcrennh1lTitehtnsaddcce5eshtsutohetri.0sp-hvest.ua.0aiiroawiinnfsCnsmd4t-utnssdta/Wus4HUlteRaaevn"ralcllauaCsallll)choiirsoe.ctos0AgnhitwestpeesrhgiasCeettop--nutyt2rtcrnoniiiyneannolfn0smsopgototeisgi0.goet-e-ftl.tr
LONG -WAVE BLACK LIGHT FIXTURE
Extremely versatile. com-
- p(bla3occ2tkl0y0li.dg4eh0sti0g(0nueldtra.anvlgioosnltgerto)wmafivsxe)-
tlaumrep. wHitahs b6ui-lwt -aitnt, fil1te1r0 -v
cLlot.r.n.n1oi1n,/5lco"l gWadp.i,luu.1gt1..i/b4"lMe oHau.lnutmvineurtm..ewtbfpfcollhlraeauaiebcramwvofftliOeerlekdsieecn,rr,ecsirtanua.cot,totle-cieitlrnfcrfrs,yaoOathayrvrpnemoihudocOnpsaildsknhngrae,imepats-rscpepfaftOruulrolrl,aalslraerlyc,nyaseesssskpruwh.f.aauroiwpifgntnUraoc1tgitecwehsts0ieh-er..,'-
Stock No. 70,364AX
$12.50 Ppd.
REPLACEMENT BULB Stock No. 60.124AK
$4.75 Ppd.
SPECIAL VISUAL EFFECTS PROJECTOR SET
Duetayalz- zleifnfIgen,cctrse-advibaFnlaytn-tgaasbrtedicaeutvifvauirsli,--
Stapinecsiaal llpancekcaegsesaroyffearppcaorna--
tinugs., fCierreyabteurfsltosatoinf gc,oeloxrp-lloikde-
. /ì`:: m(sDoirrirryireeoesreK(d8al"eiwliidCaoollselcotorepdePCe&rlofeucHdtefsoldr5o"se"""tbAcncuoSCtCiotcogrepyorcehreymelstirerp)psama,pdottiiasnhanm3lgio2itn5nwenapmggytSor,c,iamoctytapjlleriaioswnbcrhf5ddtut/oS0iosrirer0itiasrtcsaxm-tS,ar.pdp"lb.iWDprinuswohtaht.redeahcosrurFncettenoscefceesaag,seae,l1""n-s-sl-.s
71.212 instructions.
SDtoeclukxeNoM. o7d1e,l21N2oÁ. Rlens) ÁK
(w/Kaleidoscopic lens)
579.50 Ppd. 599.50 Ppd.
MIGHTY MITES
Rtuerleastivelygivsemallsur(1p2ri"s)ingfilxybright blacklight. Mirror -
fswiitnnaetintesttnheesr.idsttyarUretbpifunlelgbtcoto8lro5-ow,0kma0ta0ltki,keehshoig4ui0hnrs---
of safe, long -wave (3660A)
bpslhaaorctwkieslsi,g, hptlsiygtochhterde&eallilcythetduaetrrcnioc-raosnl,
holiday decorations. Shock-
bulb
and
starter.
Stands
proof uprighstafoer,
eeansdy-carpesplarcememovenet
for of
horizontal. Alum. case.
Stock No. 71,274ÁK
DELUXE Stock No.
O7U1T,2D9O9OÁRK/INDOOR
MODEL
$14.95 Ppd. $19.95 Ppd.
HELIUM BALLOONS MAKE A "BALL"
Atwwa2ohn5unhhedsyeicttnaaiihcmmdiorvtm6elheeo"iseasnrketdttudfehhi"earseeosamrtuabiieresfva'"b-ulstelea.onlrNloi-aEosnowossw2pnhhb5eeehapoclnleifveiluaorraemlkiornl4i'yyns--:,
fscluoarntieztdaei.dniWn(3gi0th025ltbhslei/mtse,qrs
a presino.f) hcealn-
iaamiunwdmoeuarnlyttsssttg,oraaostbri.inankgzfiladaast"re'lsigpahaolrltrteire2jus5t,sh.tagniFvdoeea-ri-r ". Helium is a safe non -toxic
Stock No. 71,289ÁK NEW
M t
5ìo2í
$3.00 Ppd. MINI -MODEL
PERFECT AddePtct-psTFpp4SSweew1rraarrstrIetcr/ooeo/aoMoazciia2bnitafcnscgjdzcturt.sei,EtktkulclunhaigiiciinrnelnlcnenNteblNgaegbiggysiadgssoosc,nsowome.h,.nh.xlaiaibfp"44et-tpcfrihslsscbd11fiIUgoeaitw,enoNaeif,,ird11sosinednahoetiedp24nut"iatairwtcsavaaa40rhpstntlilnitisnui.AÁnweoicfdtntmcnberueeiruKKigeicgsrtdlstnuuaagn,h.msglnb-ss(iiLicuchcnqlupcoaa-soaiP1ouoPwatnnnlipm1tyoeecmtAiddeie-ni0t,r.r.-tDbfh-eo)1cs2lt,o0wVfpo.arlretviwLee-silP-nsaddoowfSntseadoeniuddsSSnepdSdlao28yr,,as5f0to,00r"hsParPhuenppoasdgdrer...t
LOW COST XENON STROBE
Prerliicaeblbereaekltehcrtoruognhic instbrroibgehst,,
- mEpdp5V5PS1eela4f0x0aroaaflriWf0tierstrneeceitcio,t,reia/tezpncSstsb.dhdea,elarfelusscclonPtrhydoimoraerinifpbec1hsrlid-lfapulnu,deea0simlmuc.htac0tttyeBoe0xib8sou.e,ar1o.0flnnnkai/oaL0g2ttoerreeox0hdlndin3-ttlpg36eifdsgsl/eh0a4yhbtlcsosxciutuiahwfih2gblsneeebonsetegso-,.,....
Stock No. 71,342AK
$24.95 Ppd.
BUILD -IT- YOURSELF STROBE KIT Stock No. 71,343AK .
$19.95 Ppd.
GIANT WEATHER BALLOONS
AdhyutfmtputFlsoiwaromoaikrtsvaiiaeieciroeylrlnacdmtlasidedmeiztslctlioldeooueaolfyesetrsupbrn)teawoaeenoelsf.srlnne,otn.rpi.uuotetesrBiersrhgnaraiCEheeelsintlgocdusioxhrssowttob,emwcea,sbnrcaaillc-itli.ieltgcuaiodruleesnuoouoptutim,egGscsttwo8adeoy-mtwn'rdneb(asipaasAaeatanabhe,ieehtihvtnranaemgrraiacdlioiahgldabvhvgiahoutlbhvlaaotuahaone1occesrrtbanucip6kuriesretnlose--r--,'h.-,euostohs.eiMghatdse.
Photographers cast of heavy duty neo-
Prene.
Stock No. 60,568AK Stock No. 60,632AK
8' Diam, 16' Diam.
....
$2.00 Ppol. $7.00 Ppd.
PSYCHEDELIC LIGHTING HANDBOOK
Q 1mmdbtcoecpatohlu0caslaeel.eyscg0pcnnol,ditcekstgtri,ehoyssohl(.eilSncoiritndhzhggtrFeefeCeogahbolcu"dwnaiootihnscrelnixvsl.cmcnlyseeiplpi.crslusqaaishr.elgdlroupotiixthidig,eaMwoinpojteeslhel-gllusn.saasct-,irshtintinofloodzcgsmasrpmweeVtcsravdei.euiorl"cscqeatsrbprsilukpoitocyoesceirernopsyspaoossd-,.l---lf-,t
ulSoptoocske"leeNlaeofc.tpr9ia1cp0e0trÁripKpusn"chefodr
fporriv3agterroinuggpas.tbhiensrhdionewgr.ss.
or how to set 81/2" x 11" 53.00 Ppd.
MAIL COUPON FOR GIANT FREE CATALOG
ASTRONOMICAL TELESCOPE KITS
Grind your own mirror for powerful telescopes- Kit contains fine annealed pyrex mirror blank, tool, abrasives, diagonal mirror, and eyepiece lenses- Instruments you build range in value from $75.00 to hundreds of dollars.
erettariRmr
Stock Stock
No. No.
70,O03AK 70,OO4AK
.4.1/64""
diem., diam.,
x/a" thick .$10.75 Ppd. 1" thick .$13.95 Ppd.
Stock No. 70,OOSAK'.. 8" diam., 13/2" thick .$21.50 Ppd.
Stock No. 70,O06AK . 10" diem., 13/4" thick, 3$052lb.s5.0 FOB
148 PAGES- 1000's OF BARGAINS
CccEfiaaenuolte'omensagr.ipmnuowldsrMeoioteuaeerissklgtl,yeesnchmseetnIotrl.lsepo:le.wu.cmstfitLaoor1fgaeran9nntc7ieshto1oetoonisrfcbys,eBb..AdyDiinDsitMastoiorrotcotsaznsu.nei.-llnoasamreNccsxooci.MecpeufwasepalrnosiIynmDtaTerewemineflaoesst-.rr,catalog ''AK"
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CIRCLE NO. 140 ON READER SERVICE PAGE
ELECTRONICS WORLD
July 1971
ADVERTISERS INDEX
R,S. No.
ADVERTISER
PAGE
A.P.M. Systems 150 Akai
Allied Radio Shack 149 Audionics
69 26 21, 73 66
148 B. & F. Enterprises
77
147 B &K
54
CREI, Home Study Division,
McGraw -Hill Book Company
5
145 Cleveland Institute of Electronics Engineering 56, 57, 58, 59
144 Computronics Engineering
71
143 Crystek
4
141 Delta Electronics Co.
79
142 Delta Products, Inc.
75
140 Edmund Scientific Co.
80
116 Edsyn Inc.
54
114 Electro- Voice, Inc. FOURTH COVER
139 General Sales Co.
76
Goodheart, Co., R. E.
76
138 Grantham School of Engineering
22, 23, 24, 25
137 Greenlee Tool Co.
20
136 Gregory Electronics Corporation 78
115 Health Company
49
134 Johnson Company, E. F.
69
133 Judson Research & Mfg. Corp.
51
Lampkin Laboratories, Inc.
51
132 Liberty Electronics, Inc.
78
131 Mallory & Co., Inc., P. R.
2
130 Memorex Recording
Tape
SECOND COVER
129 Meshna Jr., John
79
National Radio Institute..16,17,18,19
National Technical Schools
9
128 Olson Electronics
53
127 Park Electronic Products
78
126 Penwood Numechron Co.
53
125 Poly Paks
79
RCA Institutes, Inc. 62, 63, 64, 65
124 Record Club of America
,,10, 11
123 Schober Organ Corporation, The .... 61
122 Sencore, Inc.
1
121 Solid State Sales
77
Surplus Center
77
Sylvania
12
119 TEAC Corporation of
America
THIRD COVER
110 Toyo Radio of America, Inc.
55
118 V-J Products, Inc.
20
Valparaiso Technical Institute
66
117 Xcelite, Inc.
8
Classified Advertising ,,,.76, 77, 78, 79
Printed in the U.S.A.
TUNER
SOURCE
PHONO
AUX -1
AUX -2
TAPE MONITOR
SOURCE
TAPE -1
TAPE-2
The TEAC Consort series: Tape-ability
is its most important capability.
This total -capability component system is designed first Other fine instruments in the Consort Series include the
and foremost for tape, as if tape had just been invented. AF -201 Multi -Channel Filter Unit for matching three -way
With it, TEAC launches a new age of magnetic recording speaker systems to any room acoustics, and the AE -201
and listening.
Stereo Power Amplifier (50 W/channel) for use in multi-
Lead instrument of Integrated Amplifier
-tahe
TEAC Consort is the AS -201 complete tape- oriented audio
control center. It permits simultaneous recording and
monitoring on as many as three tape decks, from as
many as five inputs: tuner, phono (hi & low) and 2 Aux.
The AS -201 incorporates differential -type amplifier cir-
channel installations. Crowning touch to the TEAC Consorts is the AZ -201 Total Performance Indicator for real -time scope monitoring of FM and audio stereo separation, phasing, balance and signal strength. Also avail-
able in the series is the LS -80M 3 -way speaker system with a frequency response of 30- 20,000 Hz.
cuitry- originally designed for precision computer and data recorders -as well as FET pre -amp sections to
Step into a new era with the whole TEAC Consort Series. As the first step we invite you to write for a brochure of
achieve very low distortion characteristics, wide fre- specs, graphs, and details.
quency response (20- 80,000 Hz ±0.5 into 8 ohm load),
A -1230 STEREO TAPE DECK
S/N ratio of 70 db or more for phono inputs and 90 db
AE -201
or more for high level inputs and power output of 60W
STEREO POWER AMPLIFIER
per Channel (rms) into 4 ohm load with under 0.5% harmonic distortion at rated output. Other features
AZ 201 TOTAL PERFOR-
include stepped tone controls, constant S/N volume controls, automatic protective muting- circuit and many other quality conveniences.
Another AM /FM
major Stereo
CTuonnesro-rtainssptreucmtaecnutlaisr
the AT-201 performer
for both primary and fringe -area reception. It
MANCE
CINDICATOR
° I
igAill
jii»\
utilizes FET FM inputs for selectivity of 70 db or
better, capture ratio of less than 0.1 db and
distortion of less than 0.3%. Other features include variable -level FM muting, two tuning meters and output -level control.
AF -201 MULTI- CHANNEL
FILTER UNIT
at-
r.
AT -201 AM /FM STEREO TUNER
AS-201 STEREO INTEGRATED AMPLIFIER
T E AC.
TEAC Corporation of America, 2000 Colorado Avenue, Santa Monica, California 90404 TEAC Corporation. 1 -8-1 Nishi-shinjuku. Shinjuky -ku, Tokyo, Japan TEAC EUROPE N.V., Kabelweg 45 -47, Amsterdam -W.2, Holland In Canada: White Electronic Development Corp., Ltd.. Toronto
CIRCLE NO. 119 ON READER SERVICE PAGE
4- CHANNEL SOUND
Electro -Voice
takes the first practical step:
EV STEREO-4
compatible four channel
Being more a progress report than an advertisement.,
The Promise
Thousands of people have heard 4-
channel stereo reproduction at hi -fi shows and special demonstrations in the last few years. Others have read about this fascinating and rewarding technique that promises more faithful reproduction of musical performances. Early experiments have also shown 4- channel to be an effective tool in creating new sonic environments for both serious and popular musical forms. The concept has met with almost universal critical acclaim, and strong general approval.
The Problem
But alas only a handful of enthusiasts can actually enjoy this advance today. Because only a few 4-channel tapes have been produced for sale. The problem is simple, but basic: 4-channel means just
that -four separate signals. And to repro-
duce it properly demands four of everything, right down the line.
Using four amplifier channels and adding four speakers is easy. Even creating a 4channel tape recorder is practical (although expensive). But the stumbling block has been finding a way to put four completely independent signals in a record groove, or broadcast them over a standard stereo FM station.
And if you can't buy a 4- channel disc, or hear it on FM, the market is limited to a precious few 4-channel tape owners. But their numbers are so small that record companies just can't afford to release four
channel material. So they continue to produce 2- channel stereo that you can play (and that they can sell in volume).
The Way Out
Now Electro-Voice has moved to break the impasse. With a system that can offer the significant advantages of discrete 4channel, yet is compatible with present record playing equipment and present FM broadcasting. It is called STEREO -4.
STEREO -4 is a system that encodes four channels into a stereo signal that can be transmitted over FM or recorded on a disc. In the home you add a STEREO -4 decoder, plus another stereo amplifier and a pair of rear speakers. The result is reproduction that closely rivals the original 4- channel sound. Four different signals from your speakers, with a feeling of depth and ambiance you have never before heard from any record.
Admittedly, STEREO -4 is not quite the equal of 4 discrete signals. But while there is some loss of stereo separation, there is no reduction in frequency response or overall fidelity. We might note that this reduced separation actually seems to aid the psychoacoustic effect for many listeners in normal listening situations. And on the plus side, STEREO -4 offers an advantage that even discrete 4- channel cannot provide.
The Remarkable Bonus
Playback of almost all of your present 2-channel stereo library is greatly enhanced when fed through the STEREO -4 decoder. It's the result of multi-microphone recording techniques that include a remarkable amount of 4-channel information on ordi-
nary stereo discs and tapes. Add-
ing STEREO -4 releases this hidden information for you to enjoy.
you're equipped for almost any kind of sound available. Encoded 4- channel, enhanced stereo, regular stereo, and discrete 4- channel (assuming suitable source equipment). Even mono. So you have the one system that is completely compatible with the past, present, and foreseeable future.
The Present
And what about encoded 4-channel discs and broadcasts? Well, recording companies have already started mastering STEREO -4 records, and more are joining in. And STEREO -4 is now being broadcast in many major cities around the country.
The Future
Like you, we hope for the day when discrete 4- channel sound will be common-
place on records and FM, and your
STEREO -4 decoder will be relegated to enhancing your present library. But that day will have to wait until some very knotty design problems are solved. And probably after a host of new FCC regulations define an utterly new system. Indeed, there is serious question whether these problems can be solved at all.
In the meantime, the STEREO -4 system is getting 4-channel recordings into the marketplace in increasing numbers, in a form that people can enjoy. Hear STEREO4 at your E-V soundroom soon. And ask your local FM station for a schedule of STEREO-4 broadcasts. Or write us for complete information. It's not too soon to start planning for tomorrow.
ELECTRO- VOICE, INC., Dept. 714N, 629 Cecil Street, Buchanan, Michigan 49107
In Europe: Electro-Voice, S.A., Lyss- Strasse 55, 2560 Nidau, Switzerland
The Details
,,
r
A STEREO -4 Model EVX-4 Decoder
costs just $59.95. And with it, plus 4
speakers and dual stereo amplifiers,
refer®
a GULTON subsidiary
EVX -4 Stereo -4 Decoder
FOR INFORMATION ON E-V PRODUCTS: Microphones
CIRCLE NO. 111 ON READER SERVICE CARD PA Speakers /Accessories CIRCLE NO. 112 ON READER SERVICE CARD
Musician's speakers/microphones
CIRCLE NO. 113 ON READER SERVICE CARD
High Fidelity speakers/electronics CIRCLE NO. 114 ON READER SERVICE CARD
PdfCompressor 6.0.543 CVISION Technologies
