Elementary M ARCH a IL

U DERSTANDING DIODES: THE ELECTRONIC TRAFFIC COPS elementary M ARCH A IL

EIectroiçsa BE A TARZAN IN THE PARTS BUYING JUNGLE, page 3341

EL ONIC TS THAT LL Guards me t Switch Cuts cial Itch

"Updating the Radio Shack Eli TRS-80 "Universal Whistle Switch "Regency Flight Scanner Vigilite Timer E&L Mini Micro Designer "Edmund Digital Thermometer Percom LFD-400 Floppy Disc " Heathkit TV Vectorscope

FAREWELL TO THE KING OF THE HOBBYISTS, 71 86 0 342 page 57 The Cobra 50XLR CB has it all. Installation Kit makes them the AM /FM Stereo. Cassette. And easiest in -dash radios to instal. And CB. Al in one compact unit. All our Nationwide network of Author- engineered to bring you the same ized Service Centers makes them loud and clear sound Cobra is the easiest to service. famous for. There are four Cobra in -dash The remote mike houses the models to choose from including channel selector, squelch control, AM /FM /Stereo/8- track /CB. But no and channel indicator. So all you matter witch you choose you can need for talking CB is right there in be sure of getting the best sounding your hand. The cassette player fea- radio going. The ultimate car radio. tures t_zrough the dial loading and The Cobra. four -way fader control. Because they're only five inches deep, there's a Cobra in -dash radio b ra to fit almost any car with little or no Punches through loud and clear. Cobra Communications Products modification to the dash. This DYNASCAN CORPORATION 6460 W Cortland St., Chicago, Illinois 60635 feature, plus the step -by -step Write for color brochure Installation Manual and Universal EXPORTERS. firm Plaicvir w. N Y CANADA: P.P,:r., r:., -ti n. CIRCLE 6 ON READER SERVICE COUPON THE ULTIMATE CAR RADIA

OFF/ VOL 4. TONE - MONVANL LO CB FM O PiOFF ST IIIII ECFD)R3 ALL THE MOST WANTED FEATURES AT A MOST WANTED PRICE... BIG ' -UGH LCD DISPLAY USE INDOORS OR OLT 200 F OUR 9V BATTERY LIFE AUTO ZERO, POLARI-Y, OVERRANGE INDICATION ON141195 100 ny DC F.S. SENSITIVITY HICKOK 19 FANGES AND FUNCTIONS

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Here is the handfull of accuracy you've been waiting for. Hand - 3onely encased. Z:ompact. Efficient. Rerz v3ble cover stores tea t Cnly12ounces. set lag- fished as part of the LR Hickok's exciting, HICKOK new LX 303, 3%2 LX 303 digit Mini- Multime- 11 04VmA ter with high quality components, one year guarantee and rugged Cyco- lacl) case offers Ava fable accessories incl_de AC features previously acJYer, padded vinyl carrying case found only in ex- 40.V DC probe, 10 Amp C,C shunt e -Isive units...at a p- ce under $75.00: So why wait any longer? The amazing LX 303 is here. NOW! Another American nade test equip - me -t breakthrough >: J DCV probe adapter ,ailable f: protecting input up tc 1OKV -rom Hickok, The Value innovator. Order today!

e your local Hic ok distribu :or or order below

SPECIFICATIONS: ELECT1CNIC OISTRIE.UTORS,INC. 490C EISTO AVE. DC VOLTS (5 RANGES): 0.1 mV to 1000V; Acc _ -acy CHICAGO IL 60630 ± 0.5% rdg ±O.E % f.s.; Input imped: 10M S2; Ma).. Tel 3'2-283-4800 input 1 kV except 500V on 2COmV range. AC VOLTS (40Hz to 5kHz): 0.1V to 600V; Accu acy: PL ?SE SEND ME MEIN Hickok L).303 Digita Mu timeters @ 74.95 ea. ± 1.0% rdg ±0.5% f.s. ( -2.1E max. at 5kHz); Max. RC -3 AC Adapter, 1-5VAC (ZOVAC avai .) @ 7.50 ea. input: 600V. CC -3 Deluxe Carrying Case @ 7.50 ea. RESISTANCE !6 LOW POWER RANGES): 0.- alto VP -10 X10 DCV Pobe Adapter @ 14.95 ea. -1 10A DC @ 14.95 ea. 20M0; Accuracy: ±0.5% rdg ±0.5% f.s. ( ±1.5; rdg CS Current Slvnt on 20M0 range; input protected to 120VAC1i' VP -40 4C KV DC Prcte ._ @ 35.00 ea. ranges. [ Payment encicsed Bill my: D Waster Charge EIVISA DC CURRENT (6 RANGES; :A1 nA to 100mA: Account Nc. Cep Date Accuracy: -±1.0% rdg ±0.5% l s. DIMENSIONS AND WEIGHT: 5 -7/8" x 3 -3/8" z Norte Signatur Address 1 -3/4 ", 12 oz.; POWER: 9/ batt. (not incl.) or -iickok AC adapter; READ RATE 3 /sec. OPERATINC I Ott State Zip TEMPERATURE: 0 ° -50 °C. .1 do $3.00 Postage and Handling. IL. residents add sales tax CIRCLE 1L9 On Rti11FA CrovIrr rem lamN THE STAFF March /April 1979 Volume 19, No. 2 Editor -in -Chief Julian S. Martin elementary Managing Editor Alan H. Rose, K2RHK Technical Editor Gordon Sell, KBDA1464 Associate Editor Lee Lensky, KAJR2410 Citizens Band Editor Kathi Martin, KGK3916 electronics Editorial Assistant McClean, KBKF3780 Cynthia UNTANGLE THE CONSTRUCTION JUNGLE Workbench Editor 33 The Fine Art of Buying Parts -save big bucks in the parts- buying market Hank Scott 37 Cyclops -keeps an eye on your home day or night Art Director 43 Remote Controller-turn it on or turn it off with the speed of light Ralph Rubino 62 Stoppit -be the quickest guy or gal on your block Associate Art Director David Pindar KEEPING UP WITH COMPUTERS Assistant Art Director punch with Level Il Basic Michael Vessio 42 Updating the Radio Shack TRS-80--add 70 Simply Basic -our computer whiz invents an inventory program Cover Art Director 73 Control That Tape -handy device ends tape handling hastíes Irving Bernstein 77 Computer Readout-how computers talk to other machines Art Editor Joe Groom AND Art Assistants DXING THE FAR WIDE Celeste Barbera 40 Tropical DX- explore the world of Yucatan shortwave Leslie Wallant 50 DXing at the Speed of Sound -ride the copilot's seat in the big jets Advertising Manager Ralph Vega HE PUT A RADIO SHACK IN EVERY TOWN Advertising /Research Associate 57 King of the Hobbyists -Charles D. Tandy, 1918 -1978 Jyll Holzman, KAKZ1490 Production Director Carl Bartee ELECTRONIC THEORY TO CUT YOUR TEETH ON 53 Antique Radio Corner -tuned RFs: how Grandpa made his circuits hot Production Manager diodes, the electronic traffic cops Carole Dixon 79 Basic Course -understanding Production Assistant Annette Simon e/e CHECKS OUT AT THE ELECTRONICS BAZAAR Newsstand Circulation 45 Universal Whistleswitch -the ultrasonic servant Director 49 Regency Flight Scanner -cruise the aircraft band Don Gabree 52 Vigilite Timer -makes your home look lived in when you're far away E -1 electronic classroom in a box Director 59 &L MMD -an Subscription Circulation 64 Edmund Digital Thermometer -get your reading in a flash Robert V. Enlow 67 Percom LFD -400 Floppy Disc -meet the megabyte master Subscription Circulation Manager 75 Heathkit Vectorscope -tune up your color TV like the experts do Eugene S. Slawson Marketing Director COMMUNICATIONS COUNTER James C. Weakley 55 Getting Your BNEE, Semester IV -it's time to graduate 69 Kathi's CB Carousel -Kathi finds out why Thomas J. was elected President and Publisher 72 CB XCVR Checkout -e /e looks at four great new transceivers Joel Davis Vice President and OUR REGULAR DEPARTMENTS General Manager 5 Hey, Look Me Over -new products from far and near Leonard F. Pinto 12 Newscan-keeps you abreast of developments Vice President and Treasurer 14 DX Central -Don DXs outer space Victor C. Stabile, KBP0681 16 Ask Hank, He Knows-don't worry, Hank's.here Cover Stories 22 Bookmark -by Bookworm 24 Hi -Fi Reports -be an audio MD ISSN: 0013-595X 83 Literature Library- there's a lot more than you think to read ELEMENTARY ELECTRONICS is published bi- monthly by Davis Publica- tions, Inc. Editorial and Executive of- .c.eE, fices: 380 Lexington Ave., New York, ,.. NY 10017; all subscription orders and mail regarding subscriptions should be sent to P.O. Box 2630, Greenwich, tig5 CT 06835. In U.S.A. and possessions, 1101010. OF one -year subscription (six issues) $6.95; two -year subscription (12 issues) $12.95; three years (18 issues) $18.95; and tour years $23.95. Else- where, add $1.00 postage for each AUTHORS IN THIS ISSUE year. For change of address, please advise 6 to 8 weeks before moving. Barbarello, Anthony Ca- label James Send us your current mailing Fred, Herb Friedman, with new address. Advertising offices: risti, James New York, 380 Lexington Ave., New Larry Friedman, Harry Helms, York, N.Y. 10017, 212 -557 -9100; Chi- Jr., Don Jensen, Christopher cago, 520 N. Michigan Ave., 312 -527- Kilian, Lewis Kornfeld, Kathi 0330; Los Angeles; J. E. Publishers' Rep. Co. 8732 Sunset Blvd. 213 -659- Martin, Ralph Perry, Hank Scott, 3810. Applications to mail at con- Gordon Sell, Walter Sikonowiz, trolled circulation rates are pending at Thomas Illinois. Copy- Thomas Sundstrom, N.Y., N.Y. and Sparta, by Ron Macarty right 1979 by Davis Publications Inc. Williams Cover drawing 2 ELEMENTARY ELECTRONICS /March -April 1979 Talk yourself into the best. President SSB.

It won't be hard. Channel 9 for emergencies, Channel 19 for the road, and the Just tell yourself about the Adams -President's finest SSB channel of your choice. mobile -and about how you'd enjoy the extra range and per- Now clinch the deal by mentioning President's superior formance of SSB. quality in design, electronics and craftsmanship. Take yourself into a President dealer and show You'III have talked yourself into the best. yourself how beautiful this machine would And, after all, don't you deserve it? look in your machine. Because we want you to have the best in service, installa- Remind yourself of the total tion, warranty back -up and accessories -as command you'd enjoy with the well as the best CB-President is Adams' 19 controls and switches available through independent ...more controls than you'd find on dealers specializing in CB. the average police radio. And don't forget to point out how the Adams PREsiOCnrTM keeps an ear out for you on Engineered to be the very best. President Electronics, Inc. three channels at once- 16691 Hale Avenue Irvine, CA 92714 (714) 556 -7355 In Canada: Lectron Radio Sales Ltd., Ontario

CAR COURTES' OF VROOI)ER CUSTOM COACH, LOS ANGELES, CALIF. CIRCLE 21 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 3 These new Persuader4 niennas low profile, extra long whip deliver performance equal to, or better than anything else on the road! There's a hand -wound, hand -tuned coil in the cup... a major advance in -- antenna technology from the Antenna Pros I - field tested and _. \ field proven by Completely Super-good looking thousands of CBers low silhouette pre -assembled design. and pre -tuned Your choice of Only $34 98 suggested retail. Compare Just take it out of cup colors the package, and design- coordinated with K -40 at $38.50 or any other antenna. You'll see late install it on the to -model cars. there's no comparison. car. No tuning necessary... SIERRA DIAMOND -FIRE check it out with BRONZE BLACK a watt meter and 5 year guarantee see for yourself! Materials and workmanship of PERSUADER ANTENNAS (Modelsl3505 &17605) are guaranteed for a full five years if this antenna is installed by the dealer and a full three years if this antenna is installed by the consumer. Any part that fails within the guarantee period will be replaced absolutely free provided the registration card has been completely filled out and returned to ATLANTIS FIRETHORN Antenna Incorporated. BLUE RED 60" Stainless steel Pro: tapered whip... A word from the Old and NO spring When you buy this antenna, my reputation ...built over 38 years in the antenna business ... will be riding on your roof. I'm confident that the SNOWCAP WHITE Persuader Antennas will persuade you ... you've chosen the Best. M.R. Friedberg, President CLASSIC Antenna Incorporated SILVER There's a AS Coil -in -the -cup SHOW N In stock at your dealer now... or call the Antenna Hotline _1-800-447-4700. AND CRYSTAL (Illinois:800- 332 -4400; Sorry, no Hotline service in Alaska or Hawaii). CLEAR Gel Charge to Visa or Master Charge ... and we'll

J have your nearest dealer ship your Persuader Antenna promptly, in the mount and color of your choice. Hotline Magnet orders add $1.50 for shipping and handling. Applicable local Mount taxes extra. Allow 2 to 4 weeks for delivery.

The family of fine antennas from the fine antenna family. ilnienna 26301 Richmond Road, Cleveland, Ohio 44146 (216) 464 -7075

In Canada: Cardon Import Canada Ltd., P.O. Box 937 Hamilton, Ontario L8N 3P9 Antenna Incorporated, International Division, P.O Box 1002 Rockville Centre, New York 11571 ve ... c n.. n.. nc.nro ccov.rG.tnUR[A.M. These features will noise ratio. With a pair of stereo headphones, simulated stereo reception pro- persuade you... vides the narrow filtered signal to one ear and the unfiltered signal to the The Persuader " Antenna ev, other. The ears and brain reject interference but allow off -frequency calls to is Your Best be heard. The SSB filter dramatically look me over improves readability by optimizing the Antenna Choice audio bandwidth to reduce sideband splatter, remove low and high pitched Showcase of N w Products 60" Stainless Steel Tapered QRM, remove hiss, remove static crash- Whip...and No Spring es, remove background noise, and elim- Wireless Microphone inate 60 and 120 Hz hum. The MFJ -721 requires 9 to 18 VDC and an optional The super -long whip increases the aperture of the A micro -miniature wireless microphone AC adapter is available. The price is antenna. This increases developed by MLI Industries can pick the signal capture area on reception $59.95. To order, call toll -free 800.647- up and transmit voices and other sounds the transmit signal and radiation intensity at the 8660 or mail the order to MFJ Enter- through any standard FM radio. MLI's horizon prises, P.O. Box 494, Mississippi State, Micro Mike has an on -off switch. No bandwidth to well over a 40- channel capability MS 39762. Include $2.00 for shipping need to take the battery out to turn it The .125" diameter whip is tapered, so shock is and handling. distributed evenly. There's no spring to stretch, off. The Micro Mike is a condenser -type break, or bend the whip away from the straightest High Technology TV possible upright position. Webcor has introduced a portable, lightweight TV and AM /FM radio with built -in Exclusive coil -in -cup design LCD quartz alarm clock. The clock's alarm triggers the radio or TV, and the Loading of most low- profile antennas is by a simple clock operates on its own battery so that printed circuit board that can't be tuned and will it is always running. The screen size is eventually burn out. These new Persuader anten- 41/2-inches, and a shadow mask around nas are completely pre -assembled and pre -tuned or and feature an actual hand -wound, hand -tuned the screen facilitates daytime outdoor copper wire loading coil tested with 500 watts, viewing. Large Scale Integrated circuitry rated at 100 watts continuous. It's even more effi- provides excellent sensitivity, picture cient than our base -loaded coils because it's definition, and brightness. Channel selec- wound to a larger diameter, with fewer turns. tion on the TV section is accomplished This unique design also involves fewer mechani- with an electronic varactor VHF /UHF cal and electrical connectors -fewer resistive con- tuner, and tuning of the AM /FM radio tacts between loading coil and cable termina- section is aided by an electronic eye. The tions -less chance for dust, moisture or road unit operates on any of four power gunk to contaminate the contacts. CIRCLE 44 ON READER SERVICE COUPON This concept has been field tested by thousands of CBers in our Model 13503 (shorter whip, plain microphone. Approved by the FCC, the white cup). Your good buddies will tell you every- mike operates on a 1.3 volt battery with thing we say about it is true. a life of 60 -80 hours of continuous use. Micro Mike is continuously tunable to Available with Trunk -Lip or any frequency between 88 to 108 MHz, Magnet Mount and has a range of up to 100 feet from the radio indoors, and 300 feet out- for performance: doors. Priced at $19.95 (including bat- SWR of 1.5:1 or less across all 40 AM and SSB tery) plus $1.50 postage and handling channels. charges, the mike can be ordered di- Shunt -fed loading coil is DC grounded for quiet rectly from MLI Industries, Dept. PR1, performance; bleeds off static from rain, snow, air 50 Hunt St., Watertown, MA 02172. CIRCLE 76 ON READER SERVICE COUPON particles. Performance is virtually identical to body mount antennas. sources: standard AC, D -cell batteries, Center -roof placement of magnet mount pro- CW /SSB Active Filter rechargeable battery pack, or twelve volt vides your most uniformly omni -directional signal. The MFJ Enterprises MFJ -721 Super Se- car or boat electrical systems. Suggested (Can also mount on trunk lid). lector CW /SSB Filter has a built -in 2 retail price is $249. An options package Unique Antenna Incorporated design provides watt audio amplifier, switchable noise including a car /boat cord for twelve volt capacitive coupling. Aluminum plate puts the and an selector switch for rechargeable ground potential right at the mounting surface. limiting, input operation, battery pack, and two rigs. The CW filter is an eight -pole D -cell batteries retails for $49. Webcor for convenience: Magnet and trunk lip, (4 cascaded stages) active filter cen- is a division of Leisurecraft Products, the two easiest installations! Place the antenna tered nominally at 750 Hz. It has four Ltd., 28 South Terminal Drive, Plainview, where you want it, plug the into cable the trans- selectable bandwidths: 180, 150, 110, NY 11803. ceiver. No holes to drill. Readily removed for anti- and 80 Hz. In the 80 Hz position, the theft protection. Magnet mount supplied with 12' Wire Wrapping Kit RG -58 /U coaxial cable with PL -259 type connector; trunk lip mount with 17' of cable. A new Wire Wrapping Kit, Model WK -5B, contains a complete range of tools and for magnet mount adherence: parts for prototype and hobby applica- Heavy -duty '/2" magnet in plastic cup with soft tions, all conveniently packaged in a rubber gasket. Holds at top highway speeds of 55 mph. (Trunk lip mount recommended for vinyl roof handy, plastic carrying case. The kit in- cars.) Since it won't walk, it won't detune! "Oil- cludes: Model BW -630 battery wire wrap- can" effect of cup; resting on gasket, provides a ping tool, complete with bit and sleeve, larger magnet plane than if the magnet itself were Model WSU -30, a remarkable new hand touching the surface -yet there's less weight on wire wrapping / unwrapping / stripping the car, less scratch potential. tool, a universal PC board, an edge con- CIRCLE 69 ON READER SERVICE COUPON nector with wire -wrapping terminals, a All magnet mount benefits response is at least 60 dB down one set of PC guides and brackets, a mini - are standard... octave from the center frequency. It shear with safety clip, industrial quality drastically reduces noise and provides 14, 16, 24 and 40 pin DIP sockets, an not an extra -cost accessory! up to 15 dB improvement in signal to assortment of wire -wrapping terminals,

ELEMENTARY ELECTRONICS /March -April 1979 5 HEY, LOOK ME OVER connection to a computer. It can even be used as a remote paper tape terminal using an RS -232 acoustic coupler. Dump your complex programs on paper tape for long term, safe storage. Ready to plug in, the serial version of the unused units sells for $895.00, and the parallel model sells for $695.00. For

CIRCLE 66 ON READER SERVICE COUPON

vinyl -clad steel cabinet which incor- CIRCLE 59 ON READER SERVICE COUPON porates Johnson's latest performance technology for crisp, authoritative trans- a DIP inserter, a DIP extractor, and an missions, and quiet, clear reception. unique 3 -color wire dispenser complete Johnson's noise blanker and an auto- with 50 feet each of red, white and blue matic noise limiter sig- Kynar insulated, silver -plated solid circuit clean up nals, and the large speaker gives crisp, AWG 30 copper wire. Priced at $74.95, clear audio quality. The built -in ampli- the WK -5B wire wrapping kit is available fied speech compressor eliminates the from your local electronics distributor need for power- boosting microphones or directly from O.K. Machine and Tool and similar accessories. The Viking 430 Corporation, 3455 Conner Street, Bronx, also features PLL frequency synthesizer, NY 10475. solid -state T/R switching, two -position range control, touch -indexed knobs, A Lot of Punch built -in public address capability, and The NCE /CompuMart has a warehouse CIRCLE 49 ON READER SERVICE COUPON can be operated from AC household full of still -in- the -box paper tape reader/ current, or 12 -volt negative ground DC more information, contact NCE /Compu- punches which they interfaced to op- current. The unit comes with a detach- Mart, P.O. Box 8610, Ann Arbor, MI erate with a standard acoustic coupler able hand -held A desk top 48107, or call toll -free at 800 -521 -1534. microphone. or an RS- 232 -compatible interface. A microphone is available. Viking 430 is version of this unit with a parallel inter- U.S. -made and carries Johnson's one - face is also available. The interface con- High -Style Base Station year parts and labor warranty, with ser- verts the mechanical reader contact in- The new 40- channel Viking 430 CB base vice available through Johnson's nation- puts and punch solenoid outputs to RS- station by Johnson is a desk -top unit wide network of authorized service cen- 232 levels and ASCII codes for easy with styling features and a wood -grain ters. Suggested retail price $229.95.

CLIP AND STRIP

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ELEMENTARY ELECTRONICS /March -April 1979 6 r,or, C ZS (1N pFenFa CFRVIC F COUPON The Great Breakthru! C i ár Performance!Duaedóh

Powerwave Powerwave Powerwave of Base Loaded of Top Loaded of Shahespeore's Antenna Antenna Two Load,' Antenna

NEW LONGER RANGE! NEW TALKPOWER! NEW STRENGTH! NEW MOUNTS! Two Loactm Antenna Style 5000 -1 B Trunk Lid Noun: with o Black Wh "Duo- Phased" loading. 41114 Shakespeare's computer engineered Two LoadTmAntenna doubles the advantage of both base and top loaded antennas. Base loading means low SWR. Top loading gets the signal out! With loading coils stacked and co- phased in the vertical mode, the Shakespeare Two Load""multiplies your sigral in all directions...power up to get out over the top of nearby interference...power down to ensure superior performance and low SWR Big New Bonus in Reach and Range TIP LOAD...the top loading coil is completely encased in Shakespeare's exclusive fiberglass process. No bulge. No lump. No exposed coil. And the sleek, thin design stays erect at highway speeds.

BASE LOAD...the Shakespeare base loaded coil is your booster...promising extra performance and delivering a true power match.

PLUS...the new sculptured chromed trunk mount that has Detroit cheering. With built -in electronics. A moulded rubber shield to protect your car's finish. And the new Spin -Off /On Feature lets you laugh at the guys at the car wash. The stud is stainless...the ELECTRONICS AND FIBERGLASS DIVISION housing sealed...making Antenna Group /P.0. Boo 246, Columbia. S C. 29202 the entire unit moisture The Shakespeare Company/Manufacturers of Communications Antennas. Marine proof and completely Electronics. Fishing Tackle. Industrial Fiberglass. Lighting Poles. Wonderthread and Specialized Monofilaments, Golf Equipment. Automotive Products. Saddlery and corrosion resistant! Equestrian Accessories

`1979 The Shakespeare Co. CIRCLE 30 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 7 You gotta shop around.

When you do,yoii'll probably pick CIE,. You can't afford to settle for less when it comes to something like electronics training that could affect your whole life.

8 ELECTRONICS /March -April 1979 hen you shop around for you learn and review the basics - simply this: tires, you look for a bar- perform dozens of experiments. All this training takes Wgain. After all, if it's the same Plus, you use a 3 -in -1 precision effort. But you'll enjoy it. And brand, better price -why not Multimeter to learn testing, it's a real plus for a trouble- save money? checking, analyzing! shooting career! Education's different. Do you prepare for There's no such thing as "same your FCC License? brand." No two schools are Avoid regrets later. Check alike. And, once you've made this out before you ei. roll in your choice, the training you any program. get stays with you for the rest For some troubleshooting of your life. jobs, you So, shop around for your must have your FCC training. Not for the bargain. License. For others, employers For best. Thorough, often consider it a mark in your the profes- favor. Either way, it's govern- sional training to help give you ment- certified proof of specific pride and confidence. knowledge and skills! When you build your More than half of CIE's If you talked to some of our own 5 MHz Triggered- courses prepare you for the graduates, chances are you'd Sweep, Solid -State Oscil- government- administered FCC find a lot of them shopped loscope you take your first License exam. In continuing around for their training. They real professional step. You use surveys, nearly 4 out of 5 CIE pretty much knew what was it as a doctor uses an X -ray graduates who take the exam available. And they picked CIE machine - to "read" waveform get their Licenses! as number one. patterns ... lock them in .. . study, understand and inter- Shop around ... but send Why you should pret them! for CIE's free school shop around yourself. When you get your catalog first! We hope you'll shop around. Zenith 19 -inch Diagonal Mail the card. If it's gone, Because, frankly, CIE isn't for TV everyone. Solid -State Color you cut out and mail the coupon. If There are other options you prefer to write, men- for the hobbyist. If you're the tion the name and date ambitious type -with serious of this magazine. We'll sendyou a copy of CIE's career goals in electronics - FREE school catalog - take a close look at what plus a complete pack- we've planned for you at CIE. age of independent What you should look home study information! for first. For your convenience, Part of what makes elec- we'll try to have a repre- tronics so interesting is it's sentative contact you to based on scientific discoveries answer your questions. - on ideas! So the first thing to Mail the card or coupon - Pattern simulated or write: 1776 look for is a program that starts apply CIE, East with ideas and builds on them! your new skills to some 17th St., Cleveland, That's what happens with real on-the-job-type trouble- OH 44114. CIE's Auto -Programmed® shooting! You learn to trace signal flow... locate malfunc- Lessons. Each lesson takes one tions ... restore perfect operat- or two principles and helps you ing standards master them - before you -just as with any Cleveland Institute start using them! sophisticated elect rtmics CIE1 of Eleotron Ios. Inc. equipment! I 1776 East 17th Street. Cleveland. Ohio 44114 How practical 1 ACt,Sd.d Member National Mom. Study Council is the trainúg? YES ... I'm shopping around Ifor the right kind of career training This is the next big important question. After all, your in electronics troubleshooting -and I CIE sounds well worth looking into. career will be built on what you Please send me my FREE CIE school can do - and on how When - including details about well you do it. you /1 troubleshooting courses -plus my work with a completely FREE package of home study Here are Solid -State Color information! II,-o8 ways some Bar Generator- of CIE's actually a TV signal Print Name trouble- transmitter- you study Address Apt. shooting up to ten different programs patterns on your TV City help you get screen ... explore digi- State Zip your "hands -on" tal logic circuits ... observe Age -___Phone training .. . the action of a crystal -con- (area code) With CIE's trolled oscillator! Check box for G.I. Bill infor nation: Experimental Of course, CIE offers a Veteran Active .luty Electronics more advanced training pro- Mail today! Laboratory... gram, too. But the main point is

ELEMENTARY ELECTRONICS /March -April 1979 11 to sensitive data, devices or locations. In field trials of the system, held at an IBM facility, 2,907 of 2.958 verification attempts (98.3 percent) were ac- newscan cepted. An even greater proportion of forgery attempts, 490 of 492 (99.6 percent), was rejected. The 2,958 valid Electronics in the News! signatures were collected from 248 individuals, who volunteered for the field trials. The "forgery" attempts were IBM Detects Forgeries made by some staff members from the An experimental signature verifica- Thomas J. Watson Research Center IBM Research scientists have invented an tion system invented at IBM's Research who tried to fool the machine. experimental signature verification system Division has detected the difference be- The new system measures data as a which has detected the difference between forged and genuine and genuine signatures in signature is actually being written. Small signatures in realistic tween forged field testing. Two IBM scientists, Nicos accelerometers and a pressure detector J. realistic field testing. The system may Anthony (left) and Noel M. Herbst, look on a linked someday be used in controlling access built within the barrel of pen as a third, Chao N. Liu, registers his signature with a special pen.

to a computer detect the differences in accelerations and pressure, as well as COMMUNICATIONS the revealing hesitations, that can be- RECEIVER tray attempts to forge a signature. Cheapie Chip The 8021 single -chip microcomputer BREAKTHROUGH made by Intel is the lowest -priced 8 -bit microcomputer ever offered to equipment manufacturers. It's priced at $3.00 each to large OEM buyers. Moreover, the 8021 is ideal for applications such as home appliances, test and measure- ment instruments, automotive, sensing/ recording instruments and tele- commu- nications. For this low price, the OEM (original equipment manufacturer) can obtain a complete, stand -alone, single -chip system containing an 8 -bit central processor, 64 bytes of read /write data A FULLY SYNTHESIZED GENERAL COVERAGE memory, 1024 bytes of program memory, 21 input /output lines, and all other RECEIVER AT AN ECONOMICAL PRICE generally required functions, including a programmable interval time /event counter, and very cost -effective on -chip McKay Dymek brings you a fully synthesized general coverage receiver for system clock and oscillator. less than you'd expect to pay for a single channel, single mode unit. The DR 55 The 8021 will find its way into con- is an economical solution to the need for WWV monitors for time and fre- sumer products eventually. Thermostat- gutency calibration, back up capability for main receivers, and point to point ic use for heating and cooking applications are obvious. Toy_ s offer unlimited communications receivers for industrial, governmental and marine uses. applications.

Fully synthesized general coverage (50kHz to 29.7 MHz continuous) Digital Phase Locked Loop synthesis is used providing quick, accurate and quartz crystal stable tuning at all frequencies.

A High Level RF front and design using CATV RF power transistors and a double balanced diode mixer followed by a crystal filter provides immunity from intermodulation and crossmodulation interference without the need for antenna preselector adjustments under normal conditions. (Matching DP 4044 passive RF Preselector available for use near transmitters). Class D AM envelope detection is used providing less than 1.5% T.H.D. at 90% modulation. Automatically adjusting threshold peak noise limiters enhance reception on both AM and SSB -CW-RTTY modes during conditions of impulse noise interference. Any channel can be selected in seconds using the rotary synthesizer programming switches. This extreme simplicity of operation allows frequency changes in a fraction of the time required with conventional mechanically tuned receivers. Ceramic filters are provided as the standard final selectivity element with optional Collins mechanical filters for Upper and Lower SSB, CW and RTTY. The lowest cost single -chip microcomputer ever offered, $3.00 in large OEM quantity, McKay Dymek Co. Order Factory Direct For more information the Intel 8021 microcomputer, shown in '111 South College Ave. E.:4,1 Call or Write today. 30 DAY foreground, serves a wide range of control Box 5000 PO FREE TRIAL 800/854 -7769 applications: telecommunications, auto- Claremont CA 91711 ,, (Applies in U.S. only) Calif. 800/472 -1783 motive, home appliances, and process control are notable examples. 1979 12 CIRCLE 105 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April An Extraordinary Offer to introduce you to the benefits of Membership in

BUILD YOUR ELECTRONICS BOOK CLUB OWN WORKING invites you to take

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J. You :fool n"9''r'.°W Only $1.99 for Get ALL !®I rÌ r ALL FOUR! FOUR Of These Ann°;ó,ees Regular List oteer eKrtar Huge Books canyuoao Price $47.80 For Only Top -Quality $1.99 TÑñaa° Oat/ I Hardbinding Build Your Own Working Robot Contains the Complete instructions- plans, schematics, logic circuits, and very latest wiring diagrams -for building Buster, the most unique pet in info on the world! Not for novices, Buster is a sophisticated experiment in cybernetics. You build him in 3 phases, and watch his Robotics! personality develop as you add progressively more advanced circuitry to his mainframe. The first -phase robot, Buster I, is Almost 800 "leash -led," and dependent on his master for decision -making; Buster II has a basic brain; equipped with a wireless mike, he illustrations can enter a mom and talk with the occupants. Buster Ill responds when called, and when "hungry" finds his charger, and plugs Contains over himself in. Watch his personality evolve as you build him from the ground up in a learning experience unparalleled in electronic 500,000 words Let us send you this 4- volume, construction. 238 pps., 117 illus. List $8.95. 1,302 -page Robotics Library as part of an unusual offer 1,302 data - Handbook Of Remote Control 8 Automation Techniques of a Trial Membership in Electronics Book Club. Here are quality hardbound volumes, each packed pages A practical, step -by -step guide to designing, building, and especially designed to help you increase your installing hundreds of remote control systems, and scores of know -how, earning power, and enjoyment of elec- coming 12 months. You would probably buy automated devices...from garage door openers to light at sensors, tronics. Whatever your interest in electronics, least this many anyway, without from intercom controls to electromechanical timers -to inter- the substantial you'll find Electronics Book Club offers practical, savings offered through Club Membership. facing a microprocessor with household devices. You'll learn how quality books that you can put to immediate use to apply To start your Membership on these attrac- electronic and mechanical techniques to remote-control and benefit. with tive terms, simply fill out and mail the coupon computers, with audible tones, with ultrasonics, with radio This extraordinary offer is intended to prove waves, with light beams, today. You will receive the 4- volume Robotics with dozens of special systems. You to you through your own experience, that these can build light and power failure sensors, position indicators, Library for 10 -day inspection. YOU NEED SEND very real advantages can be yours... that it is pos- tone -operated systems, tone generators, RC hydraulic de- NO MONEY. If you're not delighted, return the sible to keep up with the literature published in vices...and you'll see how to interface mechanical devices, books within 10 days and your Trial Membership your areas of interest, and to save substantially hydraulic systems, and electric motors with electronic systems. will be cancelled without cost or obligation. 294 pps., 250 illus. List $12.95. while so doing. As part of your Trial Membership, you need purchase as few as four books during the ELECTRONICS BOOK CLUB, Blue Ridge Summit. Pa 17214 Digital Interfacing With An Analog World NItiIN MI MN fitl,t(b A GIANT 406 -page handbook that shows you how to design Facts About Club Membership circuits to interface microprocessors, computers, telephones, ELECTRONICS and other digital devices with the analog world...that shows you The 4 introductory books carry a publisher's retail price of BOOK CLUB how to really put your microcomputer to work to measure certain $47.80. They are yours for only $1.99 for all 4 (plus postage/ Blue Ridge Summit, Pa. 17214 conditions, or to control external devices. Tells you all about how handling) with your Trial Membership. to go about it -how to convert energy produced by pressure, You will receive the Club News, describing the current Selec- I Please open my Trial Membership in ELEC- tion, force, position, temperature, etc. into an electrical voltage or Alternates, and other books, every 4 weeks (13w a year) I TRONICS BOOK CLUB and send my 4- volume you want the current your microcomputer can deal with. It shows you, tells you, If Selection, do nothing; it will be sent to you automatically. If you do not wish Robotics Library, invoicing me for only $1.99 describes and discusses things you can do with those I/O ports to receive the Selection, or if you want to order one of the many Alternates offered, you simply give other than connect them up to a prefabricated peripheral! It's a plus shipping. If not delighted, I may return the instructions on the reply form (and in the envelope) provided. "meaty" volume chock -full of practical info on a wide range of , books within 10 days and owe nothing, and and return it to us by the date specified. This date allows you at topics for engineers, computer hobbyists, engineering techni- least 10 days in which to return the form. IT because of late mall have my Triad Membership cancelled. I agree cians, and robotics builders. 406 pps.. 277 illus. List $12.95. delivery, you do not have 10 days to make a decision and so to purchase at least receive four additional books The an unwanted Selection, you may return it at Club ex- Complete Handbook Of Robotics pense. during the next 12 months after which I may How to design and build ANY kind of robot...including ones with To complete your Trial Membership, you need buy only four 1 cancel my membership at any time. microprocessor "brains " -PLUS how to interface robots with additional monthly Selections or Alternates during the next 12 months. You may cancel your Membership any time you computers! It's a single sourcebook that contains all the after , purchase these four books. techniques you'll need for creating, designing, building, and Name Phone All books- including the Introductory Offer -are fully return- operating your own robot from beginning to end...with enough 1 able after IO days if you're not completely satisfied. options to create a whole family of robotic wonders -controls All books are offered at low Member prices. plus a small 1 Address can be electrical or electronic; power can be electrical, hydraulic, postage and handling charge. or pneumatic; your robot can operate by radio control or with a Continuing Bonus: If you continue after this Trial Membership, , full range of sensors to move about on its own. This practical you will earn a Dividend Certificate for every book you purchase. City volume gives ALL the info needed to build a walking, talking Three Certificates.plus payment of the nominal sum of $1.99 will 1 friend and companion, or even a helpful servant. Includes 7 entitle you to a valuable Book Dividend of your choice which you Chapters on advanced robot circuits, controls, and sensors. 364 may choose from a list provided Members. I State Zip pps., 137 illus. List $12.95. (Valid for new Members only. Foreign and Canada add 157.1 EE -39 CIRCLE 24 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 13 Voyageur's Last Voyage. In DX B &K- PRECISION's CENTRAL REPORTING's September - October 1978 column, I mentioned the new fact that the European -style "hobby ox central pirates" appeared to be invading North American shores. digital Perhaps the most interesting of the reporting recent pirates, because of its fairly long life (about eight months), its regular probe weekly schedule, its wide reception area A world of SWL info! (at least coast to coast and perhaps across the Atlantic) and its general offers more BY DON JENSEN wackiness, was the Voice of the Voy- U NORMALLY, IN DX CENTRAL, I ageur. than logic don't get involved in radio amateur The Voice of the Voyageur, the self - doings. There are several fine maga- styled "Free Broadcaster from the zines devoted exclusively to ham radio. Mighty North ", was heard nearly every And, while some of you are amateurs, Saturday night for at least a half an most readers of this column are into hour on 5,850 kHz. It called itself the DX listening. champion of bootleg broadcasting and But because so many readers have "voices" identified themselves by vari- been asking about DX'ing satellite sig- ous names, including Bobby Bootleg- nals, let's take a look at the amateur ger, A.F. Gain, R.F. Wavelength, Disco radio satellite transmissions of OSCAR Dan, Slow Joe, and others. Its loca- 8. tion? According to announcements, OSCAR 8 uses a shortwave frequen- "one mile north of nowhere." cy of 29,402 kHz. Transmissions are in The station's first broadcast was on code, not voice, but don't let this deter Christmas Day, 1977. Its last was Aug- you from trying to tune in this ham ust 20, 1978. Eight days later, the FCC hand beacon as it passes over your part raided and confiscated the Voice of the Model of the country. OSCAR transmits a Voyageur's 100 watt AM transmitter. half dozen code groups, preceded by During its lifespan, the DX'ing com- DP -50 the word "HI" (di- di- di -dit, di -dit). munity speculated as to the identity of An earlier satellite, OSCAR 7, may the operators and the location of the Reveals pulse also be heard on 29,502 kHz, with a station. Some believed it was located presence to 50MHz somewhat similar beacon. It transmits north of the border in Canada, others Priced at only $50 24 code groupings, beginning with the supposed it was in Michigan or in Multi- family, compatible introductory CW (Morse) "HI HI." Minnesota. As it turned out, the latter with TTL, DTL, RTL, OSCAR 8 has an orbit of just over guess was right. After the federal CMOS, MOS, and HiNIL 100 minutes. It usually can be heard agents silenced the station, the self -pro- Clearly displays in- circuit and it can claimed "Top Man" of the station logic activity during the evening hours, be by sheer patience, hanging on identified himself in several DX bul- Memory mode to "freeze" found pulse display the frequency for a number of hours letins as Mike Martin of Crystal, Min- nesota. Pulse mode to "stretch" until you hear the beacon transmission short pulses during OSCAR's passage. Apparently no prosecution will fol- 2 megohm input impedance The exact time for an OSCAR 8 low the raid, although it is possible Typically detects pulses reference orbit is broadcast by the under federal law. If pirate radio blos- to 10 nanoseconds station of the American Radio Relay soms in the United States, it seems Overload and reverse League (ARRL), the national amateur likely that somewhere along the line, polarity protected radio organization, located at Newing- the government will feel it necessary to ton, CT. The OSCAR data is broad- take bootleg broadcasters to court. B DP -50 50MHz The new &K- PRECISION cast by the ARRL station, W1AW on Why has the hobby pirate radio digital probe simplifies the trouble- movement flourished in Europe? It shooting and analysis of all digital cir- 3,990, 7,290, 14,290 and 21,290 kHz cuits by clearly displaying in- circuit at 0130 GMT. seems that the governments of the vari- logic activity and pulse presence. If you live in the central part of the ous countries more or less tacitly ig- This compact instrument includes continent, listen for a later passage of nore these various unlicensed broad- every important logic probe feature the satellite, approximately an hour casters as long as they stay within and more. Three bright LED indicators and three -quarters later. West Coast their own little self -defined frequency display pulse presence and high- and band and as long as they keep their low -logic states. Unlike ordinary logic DX'ers can try about three and a half probes, the DP -50 digital probe will con- hours after the reference orbit time, or power low. Those that have had illu- tinue to indicate pulse presence to check again twelve and three -quarters, sions of going "big time ", with more 50MHz. fourteen and -a -half, or sixteen hours than 100 watts of power, have been Available for immediate delivery at later. Be patient! quickly raided and shut down. your local distributor. This brief introduction is merely in- In the U.S., the FCC's position seems tended as a tip -off to non -hams that to be, from its actions, to try to shut *KPREC/SION amateur radio satellite signals can be off any illicit radio operation. heard by DX'ers. If you want more Any such station that uses much DYNASCAN detailed data about times and uses of power and has anything like a regular CORPORATION the OSCAR satellites, I suggest you broadcasting schedule (which, frankly, 6460 West Cortland Street regularly read the amateur radio maga- is a requirement if a station wants to Chicago, Illinois 60635 312/889-9087 zines or contact ARRL, Newington, attract an SWL audience) will be In Canada: Atlas Electronics, Ontario CT 06111. nailed, sooner or later. CIRCLE 36 ON READER SERVICE COUPON 14 ELEMENTARY ELECTRONICS /March -April 1979 Fcr over a quarter century, buying the very best CB antenna has meant buying Artenna Specialists. From superior materials, like resilient 17 -7 PI-1 stainless steel whips -to

superior engineering, like the cool running coil in the famous ' Big Momma" -these are the finest antennas money can buy. Only now you can buy them for less! Because your Artenna Specialists dealer is offering big 25th Anniversary savings on over a dozen of our newest and most popular models. It's a silver opportunity to move up to the stripes of quality... so see your dealer today'; New "customized" look! Model M -500 sidebody mount, the antenna specialists co. a member of The Allen Group Inc. top loaded fiberglass whip 12435 Euclid Ave. Cleveland. Ohio 44106 with super performance. Export: 2200 Shames Drive, Westbury, L.I., NewYork 11590 Canada: A. C. Simmonds & Sons, Ltd.

CIRCLE 28 ON READER SERVICE COUPON 1 ^ Got a question or a problem with a project -ask Hank! Please remember that Hank's column is limited to answering specific electronic project' questions that you send to him. Personal replies 0 III J cannot be made. Sorry, he isn't offering a circuit design service. Write to: Addon MiniDisc for theTRS80 Hank Scott, Workshop Editor Ask Hank, ELEMENTARY ELECTRONICS .. _ --:-_ -__.-- 380 Lexington Avenue r.______--_ l New York, NY 10017 ' _ 7! He Knows!

Dual and triple drives Same Old Problem also available. Hank, my old hound would whine when 1 sent or received CW. So, I switched to SSB phone. Now the guy next door whines. He's 140 pounds heavier than my dog and we both fear him. What am I doing wrong? -L. J., Detroit, MI

I knew a Dutchman who always put on an Irish brogue when he transmitted, and spent every Friday night at the local pub saying, "Ya, der Irish are dumbkoff hams!" He got away with it for a long time, but you've been caught early in the game. Understand that your neighbor does not enjoy your voice coming through his FM set and herringboning his TV set. Find the trouble. Start at your end. Check your modulation, any splatter? Keep that SWR down and inspect the antenna. Keep power down during prime TV hours. Install filters. Then visit your neighbor and give him a hand in inspecting his TV only antenna. Be a sport, install the TVI filters at your expense. You'll find that both you and your dog will get to like the neighbor. Get him into your shack when you have a pre- PUMA arranged DX contact and let your neighbor chat a bit. If he $399oó PERCOM DATA COMPANY, INC. gets involved with ham radio, your troubles are over. Requires 16K RAM, Dept.EE 318 Barnes Garland, TX 75042 Phone: (214) 272 -3421 Level II BASIC and Sounds Good Expansion Interface. To Order Call 1 -800 -527 -1592 a hate gear. they have PERCOM COMPANY NC. I hear hi -fi outfit now makes quality Do 'RADIO SHACK and 755 -80 are trademarks of Tandy Corporation which has no relationship to OAtH anything for 2 meters? -L. V., Los Angeles, CA CIRCLE 19 ON READER SERVICE COUPON You're putting me on? You are referring to the Trio -Kenwood people at 116 E. Alondra, Gardena, CA 90248. They make a beauty of an FM transciever for 2 meters. It's the TR -7400A that sells for about $400. Whatta rig!

Fails When Cold Why is it TV antenna troubles always occur in the middle of winter? -A. S., Lincoln, NE Because TV antenna inspection and maintenance is never performed in the fall. Would you believe that my TV antenna is over 12 years old, and it is as good today as it was when new. I always replace the coax lead -in every other year. Bolts are checked, corroding rivets and hardware replaced.

Getting BASIC Why can't the Personal Computer companies get together and come up with one cassette tape for loading BASIC language into any computer? -D. J., San Diego, CA Mounts on glass! Sounds like a good idea, but you need different programs for Transmits different chips. The 6800 chip doesn't speak the same machine language as the 8080 chip, so no one cassette tape can do the and receives job. However, the industry should agree on two or three levels thru glass! of basic: i.e.. 4K, 8K. 12K, and put it all on ROMs that inter- Great for auto, truck, RV, with This way, will with a Easy Installation face CPUs. everyone start off and whereby Takes only 5 min. marine, motorcycle universal BASIC language any BASIC program from Mounts Anywhere there's home use one manufacturer will work on another's personal computer, a metal frame window no matter what microprocessor chip is used. including fiberglass bodies. Clearer Communications Youngster Goes Antique Rejects static 1 am 14 years old, and I would like to start collecting 360° Signal Full 1/2 wave design antique radios. I have repaired and built radios before, it's just that I don't know how to find the old radios. Please help if 340 Stewart Ave. possible. ;IN;m1 antennas J Addison, IL 60101 -Carey Sgrtin 306 Radio Road Sulpher Springs, TX 75482 16 CIRCLE 102 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 Advertise, my boy, advertise. First, tell all your friends, relatives, and neighbors about your hobby. Put up a notice in your local supermarket. Your dad can help by putting a notice up in his office or factory bulletin board. Vistit flea markets, tag sales, garage sales. Start thinking, you'll find more ways yourself. Good luck.

Listen To Me Hank, do you hare plans for a voice activated switch? -L. A., Amherst, NH

Sorry, I don't run a design service, so I can't help you with plans, however, do you have 880 If you do, then buy the voice activated solid -state switch from EDI, Dept. EE6, 4900 Elstron Avenue, Chicago, IL 60630. Minimum order is $3.00. Catalog is free. By the way, the 880 special is normally open, then locks closed.

Takes Lots of Pics Hank, I'm a 35 millimeter camera fan, and soon will open my first darkroom. Do you have any plans for a timer? I've built projects before. -J. D., Greenwich, CT

The Fall- Winter 1978 issue of ELEC- TRONICS HOBBYIST has plans for a Pro - Timer project you may want to build. Also, there are several other projects that shutterbugs may want to build.

Book Hunter Hank, can you please provide me with, or refer me to some basic information on AC and DC motors? I need theory as well as applications. -W. L., Richmond, IN

Look into our Bookmark column, and write to the publishers of the reviewed books to send you their latest book catalogs. Also, check your local library.

In the Dark Where can 1 find a book on subjects for the darkroom? -R. E., Sikeston, MO

It may be too late to find a copy on the Build. Rebuild. entry. Our Super -Strip solderless newsstand, but see if you can get the Fall - Stack. Rack. breadboards give you 840 solderless Winter 1978 Edition of ELECTRONICS HOB- Solderless breadboarding plug -in tie points -both 5 -point ter- BYIST. Can't find it? Then write to the is all so easy minal and distribution capability - magazine at 380 Lexington Avenue, New with A P Super- Strips. enough capacity to build circuits York, NY 10017 and enclose $1.50 and with as many as nine 14 -pin DIPs. $.25 for postage and handling. Build a circuit almost as fast as you dream it up. Pull it apart and do And the price is right. Nearest another -everything's as good dealer? We'll tell you. Phone (toll -free) Lend A Hand as new. Any solid hookup wire up 800 -321 -9668 right now. And ask for A, Our readers ask for help, and only you to #20 plugs right in to connect our complete A P catalog, The Faster can do it. Please contact anyone below DIPs, discretes and other compon- and Easier Book. whom you can help. They thank you and I thank you! A P PRODUCTS A Hallicrafters SW Radio, Model S -120, INCORPORATED needs info on alignment; Sean A. Devitt, Box 110C 72 Corwin Drive 2237 Wharton Rd., Glenside, PA 19038. Painesville, Ohio 44077 A CGE Model KL -66 Radio Vintage Tel. 216/354 -2101 1935 -36, needs circuit diagram; James D. TWX: 810 -425 -2250 MacDonald, RR #1, West Bay Road, N.S., Canada BOE 3L0. Faster Easier is what we're all about. A GE Voice Commander 132 -174 MHz and FM Transceiver, needs power pack, literature; Alan P. Summerlin, KA4CUF, P.O. Box 183, Broadway, NC 27505. CIRCLE 26 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 17 Everjyjbodys making money seiiin rnuçrocomputers. Somebody s going to malte money servicing them. New NRI Home Study Course Shows You How to Make Money Servicing, Repairing, and Programming Personal and Small Business Computers

18 ELEMENTARY ELECTRONICS /March -April 1979 Seems like every time you turn around, Assemble Your Own Other Opportunities somebody comes along with a new Microcomputer in Electronics computer for home or business use. NRI training goes far beyond Since 1914, before commercial radio And what's made it all possible is the theory. It includes practical experience, too. was even on the air, NRI has been the way amazing microprocessor, the tiny little As you progress, you perform meaningful to learn new electronics skills. Today's chip that's a computer in itself. experiments building and studying elec- modem offerings include, in addition to Using this new technology the tronic circuits on the NRI Discovery Lab® three different computer courses, TV/Au- industry is offering compact, affordable You assemble' test instruments that in- dio/Video Systems Servicing, with training computers that will handle things like clude a transistorized volt -ohm meter and on the only designed-for - learning 25" payrolls, billing, inventory, and other a CMOS digital frequency counter... instru- diagonal color TV with state -of -the -art jobs for businesses of every size...per- ments you learn on, use later in your work. computer programming. Or, check out form household functions including our Complete Communications Course, budgeting, environmental systems preparing you to enter this booming control, indexing recipes, and more. field servicing, installing, and repairing And thousands of hobbyists are already equipment like microwave, broadcast, CB, owners, experimenting and developing shortwave radio, paging, radar, and more. their own programs. Mail Postage -Paid Card Growing Demand for for Free Catalog Computer 11-chnicians No Salesman Will Call This is only one of the growth Send for your factors influencing the increasing today free copy of our 100 -page, Full -color It opportunities for qualified computer catalog. describes all of our electronics courses in detail, show- technicians. The U.S. Department. of ing kits, equipment, and lesson plans. Labor projects over a 100% increase in Look it over at your job openings for the decade through convenience, then decide how NRI can help you make the 1985. Most of them new jobs created by And you build your own microcomputer. most of your talents. There's no obligation the expanding world of the computer. Each step of construction advances your and no salesman will ever call or bother knowledge, gives you deeper insights you. With more than a million students Learn at Home into this amazing world that's upon us. and unmatched experience in home train- in Your Spare Time This is the only microcomputer de- ing, NRI gives you the most in training NRI can train you signed for learning. It looks, operates, and for new opportunity! If card has been for this exciting, rewarding performs just like the finest of its kind...ac- removed, write to: field. Rain you at home tually does more than many commercial to service not only micro- units. But NRI engineers have designed NRI Schools computers, but their larger components and planned the assembly McGraw -Hill Continuing Education Center brothers, too. Rain you at procedure so it demonstrates important 3939 Wisconsin Avenue your convenience, with principles, gives you working experience tl II Washington, D.C. 20016 clearly written "bite- size" in detecting and correcting problems. "fin i Y lessons that you do evenings And that's or weekends, without what NRI going to classes training or quitting your is all present job. about

ELEMENTARY ELECTRONICS /March -April 1979 21 NEW! OWN BUILD YOUR 1 OR TV! TRONEX F/1.9 LENS SCREEN CO featured in November included. Popular Science. BIG olor TV! TV not any Portables are hours. uired. Convert Ina few P be built Can tools No special S15ONALLOPAICKAGEORDERS! LIFESCREEN III The LIFESCREEN III projection system gives you all tie enjoyment and excitement Place Your Bet. Programmable calcula- of the $4000 systems. Our new injection molded Tron -Ex lens (F /1.9) produces an amazing Image that is over 3 times brighter than most nationally marketed tors will significantly influence the study big -screen TVs -including Sony And the Tron -Ex delivers sharper locus to the and teaching of mathematics. These de- screen edge tor better overall clarity. Our light- enhancing Extron LS-50 screen is 6 times brighter than most movie screens, because the molded parabolic contour vices are the "slide rules" of today, but rejects extraneous light, concentrating a directionally selective TV image for clear, much more powerful and efficient than colorful viewing. The LIFESCREEN Ill plans provide exact dimensions to fit the slide rules have ever been. Take a Chance 13" Toshiba (model C389), but they can be modified to fit most 12" to 19" portables. Pre-constructed LIFESCREEN Ill lens housings available for most With Your Calculator by Prof. Lennart TVs. Order the components catalog below. COMPLETE PACKAGE $319 Rade is a first step in introducing the use LIFESCREEN II LIFESCREEN I of programmable, calculators in the study The self -contained protection system The original independent projection reader that uses any transistor portable TV system from Extron. Works with the of probability and statistics. The (12" to 19 ") requires only 2 x 4 Sharp 13" model 13A29 color TV or will need no previous experience in either feet of floor space .. fits neatly against Sony 15" model KV1541R color ra any wall and lends its beauty to the decor Can be used with any size screen. The

of any room. Includes Tron -Ex F /1.9 LIFESCREEN I includes our new Tron -Ex lens, Extron LS -50 screen, two front F/1.9 lens. one front surface mirror. Your calculator TAKE A CHANCE surface mirrors. and building plans for building plans for cabinet, and the LS -50 YOUR CALCULATOR can do wonders x 40'' /50" diagonal. Willi Me cabinet screen. 32" in the study COMPLETE PACKAGE $369 COMPLETE PACKAGE $339 n.. nrta«r" of probability. EXTRON OUAAANTEES EVERYTHING: the professional quality, accuracy of description and availability of components described in this ad. After building your LIFESCREEN PROJECTION SYSTEM, If you are not satisfied for any reason, Soft cover return al components to EXTRON for instant refund. 163 pages LARGER SCREENS FOR THE LIFESCREEN I AND LIFESCREEN 111 SYSTEMS CAN BE ORDERED FROM OUR CATALOG. $8.95 EXTRON LIFESCREEN PROJECTION SYSTEMS Please send me the Items checked below: 8833 Sunset Boulevard Suite 202 I $9 00 i ONE COMPLETE SET OF LIFESCREEN PLANS West Hollywood, CA 90069 G ONE COMPLETE SET OF LIFESCREEN II PLANS S9 00 CIRCLE 77 SET OF LIFESCREEN Ill PLANS 59.00 Name ONE COMPLETE ON READER COMPLETE LIFESCREEN I PACKAGE $339.00 Address COUPON COMPLETE LIFESCREEN II PACKAGE $369.00 City State _Zip SERVICE PACKAGE $319.00 C7 COMPLETE LIFESCREEN Ill CARO NAME purchase) EXTRON COMPONENTS CATALOG . (Applicable toward any $1.00 CARD NUMBER EXP. DATE All prices F.O.B. factory-Cal. residents add 6: sales tax SIGNATURE TOTAL $ probability theory or in programming to aid the reader CIRCLE 100 ON READER SERVICE COUPON learn both. Simple exercises in gaining expertise. Published by Dilithi- um Press, P.O. Box 555, Forest Grove, Oregon 97116. The world of he ULTIMATE in electronics CHEAP VIDEO Everything About Microcomputers. This BOOK & KIT is the definitive microcomputer book for the gee -wizardry NLY $42.95 hobbyist. The Scelbi Byte Primer is the most extensive and well- organized volume we have seen on microcomputers to date. Over 400 pages long, and containing contribu- .0P ,4d I4 tions from more than 50 recognized authors, 4 it is the "bible" that your bookshelf needs. The book contains many illustrations and photographs, which can help even the green- est hobbyist make the maximum use of his NMI Don Lancaster's "Cheap Video "concept $10.95 (plus $1 postage) Everything about allows almost unlimited options, 400 plus pages microcomputers. including: Soft cover * Scrolling- Full performance cursor. * Line /Character formats of 16/32. 24/80, 32/64 .... or almost anything. * Graphics -up to 256 X 256 B BM, 96 X 128 COLOR (requires low -cost option modules )

* Works with 6502 , 6800 and other micros. SPECIAL OFFER: Buy the Kit (upper case alphanumeric option CIRCLE 79 ON READER -YOURS FREE. included) & get the Book at 1/2 price. SERVICE COUPON Ma ELECTRONICS 1020w WILSHIRE BLVD.. OKLAHOMA CITY. 0K 73116 lists ideas 32 -pages of test instruments -from the or her home system. The Primer latest digital multimeters to the famous I'm Sold. PEASE RUSH () SEND FREE CATALOG, for practical, home -use programming, as EICO scopes. Security systems. Auto- C 7 TVT-6 S43 Kit & CheapVideo Cookbook 1642.95 enclosed well as the theory to back them up. For the motive and hobbyist products. Kits and tt TVT -85,8 Kit only (book required for assembly) -$39.95 advanced builder, there are construction assembled. EICO quality. EICO value. name: plans for 6800 and Z80 computers, just to For FREE catalog, check reader service address' mention a few. If you are a beginner or an card or send 750 for first class mail. old hand, there is something in here for you. city: state: zip ® 108 New South Road Published by Scelbi Computer Consulting, LIMA ELECTRONICS, OEpt 2- E,1020w. 6100010E BLYO.. OULAN06A CITY. OR 73116 133 PP STN, Department B, E/CO `t7 Hicksville, N.Y. 11801 Inc., P.O. Box CIRCLE 18 ON READER SERVICE COUPON Milford, Connecticut 06460. CIRCLE 2 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 22 BUILD 20 RADIO and Electronics Circuits PROGRESSIVE HOME RADIO -T.V. COURSE Now Includes * 12 RECEIVERS * No Knowledge of Radio Necessary * 3 TRANSMITTERS * SQ. WAVE GENERATOR * No Additional Parts or Tools Needed * SIGNAL TRACER * Solid State Circuits * AMPLIFIER Training Electronic' ans Since 1946 * SIGNAL INJECTOR * Vacuum Tube Circuits CODE OSCILLATOR FREI .TRAS YOU DON'T HAVE TO SPEND HUNDREDS OF DOLLARS FOR A RADIO COURSE i SOLDER! The "Edu-Kit" offers you an outstanding PRACTICAL HOME RADIO COURSE at a ELECTRf ESTER rock -bottom price. Our Kit is designed to train Radio & Electronics Technicians, making PLIERS use of the most modern methods of home training. You will learn radio theory. construction practice and servicing. THIS IS A COMPLErE RADIO COURSE IN EVERY DETAIL. VALUA OUNT CARD You will learn how to build radios, using regular schematics; -chow to wire and solder, CERTI' F MERIT In a professional manner; how to service radios. You will work with the standard type of TEST/ UCTION MANUAL punched metal chassis as well as the latest development of Printed` Circuit chassis. HIGH Y GUIDE QUIZZES You will learn the basic principles of radio. You will construct, study and work with TELF 'OOK RADIO RF and AF amplifiers and oscillators. detectors, rectifiers, test equipment. You will learn TRO OTING BOOK and practice code. using the Progressive Code Oscillator. You will learn and practice MEP IN RADIO -TV CLUB: troubleshooting, using the Progressive Signal Tracer, Progressive Signal Injector. Pro - CO' 111:N SERVICE FCC gressive Dynamic Radio & Electronics Tester, Sgaare Wave Generator ng instructional material. and the accompany AP .ICENSE TRAINING You will receive training for the Novice, Technician and General Classes of F.C.C. Radio' P' IRCUITRY Amateur Licenses. You will build Receiver, Transmitter, Square Wave Generator, Code Oscillator, Signal Tracer and Signal Injector circuits, and learn how to operate them. You will receive an excellent background for television, Hi -Fi and Electronics. Absolutely no previous knowledge of radio or science is required. The "Edu -Kit" is ICING LESSONS I the product of many years of teaching and engineering experience. The "Edu-Kit" will provide you with a basic education in Electronics and Radio, worth many times the low You will learn trouble -shooting and price you pay. The Signal Tracer alone is worth more than the price of the kit. Servicing in a progressive manner. You Will practice repairs on the sets that THE you construct. You will learn symptoms KIT FOR EVERYONE and causes of trouble in home, portable and car radios. You will learn how tO You do not need the slightest background ages and backgrounds have successfully use the professional Signal Tracer. the In radio or science. Whether you are inter- used the 'Edu -Kit" in more than 79 coun- dynamic ested in Radio & Electronics because you tries of the world. The 'Edu -Kit" has been unique Signal Injector and the want an interesting hobby. a well paying carefully designed, step by step. so that Radio & Electronics Tester. While you a you you a are learning in this practical way, you business or job with a future, will find cannot make mistake. The Edu -Kit" will be able to do many a repair job for the 'Edu -Kit" a worth -while investment. allows you to teach yourself at your own your friends and neighbors. and charge Many thousands of individuals of all rate. No instructor is necessary. fees which will far exceed the price of the ..Edu-Kit." Our Consultation Service will help you with any technical prob- PROGRESSIVE TEACHING METHOD lems you may have. The Progressive Radio "Edu -KK" is the foremost educational radio kit in the world, and is universally accepted as the standard in the field of electronics training. The "Edu. Kit" uses the modern educational prirfciple of 'Learn by Doing." Therefore you construct. FROM OUR MAIL BAG learn schematics. study theory, practice trouble shooting-all in a closely Integrated program designed to provide an easily -learned. thorough and interesting background in radio. Ben Valerio, P. O. Box 21, Magna. You begin by examining the various radio parts of the "Edu- Kit." You then learn the Utah: "The Edu -Kits are wonderful. Here function, theory and wiring of these parts. Then you build a simple radio. With this first I am sending you the questions and also set you will enjoy listening to regular broadcast stations. learn theory. practice testing the answers for them. I have been in and trouble -shooting. Then you build a more advanced radio, learn more advanced theory Radio for the last seven years, but like and techniques. Gradually, in a progressive manner, and at your own rate. you will to work with Radio Kits, and like to find yourself constructing more advanced multi -tube radio circuits, and doing work like al build Radio Testing Equipment. I en- professional Radio Technician. joyed every minute I worked with the Included in the 'Edu -Kit" course are Receiver, Transmitter, Code Oscillator, Signal different kits: the Signal Tracer works Tracer, Square Wave Generator and Signal Injector Circuits. These are not unprofessional fine. Also like to let you know that "breadboard" experiments, but genuine radio circuits, constructed by means of professional feel proud of becoming a member Of your wiring and soldering on metal chassis, plus the new method of radio construction known Radio -TV Club." as Prin - ircuitr These circuits operate on our regular AC or DC house current. Robert L. Shuff, 1534 Monroe Ave.. Huntington, W. Va.: "Thought I would drop you a few lines to say that I re- THE "EDU -KIT" IS COMPLETE ceived my Edu -Kit, and was really amazed a be had You will receive all and instructions that such bargain can at such parts necessary to build 'twenty different radio and electronics cir- a low price. I have already started re- cuits. each guaranteed to operate. Our Kits contain tubes. tube sockets. variable. electrolytic. mica. ceramic pairing radios and phonographs. My and paper dielectric condensers, resistors. tie strips. hardware, tubing, punched metal chassis. Instruction friends were really surprised to see me Manuals, hook -up wire, solder, selenium rectifiers, coils. volume controls, switches. solid state devices. etc. get into the swing of it so quickly. The Trouble -shooting Tester that comes with In addition, you receive Printed Circuit materials, including Printed Circuit chassis, the Kit is really swell. and finds the special tube sockets, hardware and instructions. You also receive a useful set of tools, a trouble, if there is any to be found.' professional electric soldering iron, and a self -powered Dynamic Radio and Electronics Tester. The 'Edu -Kit" also includes Code Instructions and the Progressive Code Oscillator, in addition to F.C.C. Radio Amateur License training. You will also receive lessons for SOLID STATE servicing with the Progressive Signl Tracer and the Progressive Signal Injector, a High Today an electronics technician or hobbyist re- Fidelity Guide and a Quiz Book. You receive Membership in Radio-TV Club, Free Consulta. quires a knowledge of solid state, as well as vacuum tien Service, Certificate of Merit and Discount Privileges. You receive all parts, tools. tube circuitry. The "Edu -Kit" course teaches both. instructions, etc. Everything is yours to keen. You will build vacuum tube, 100% solid state and combination ( "hybrid ") circuits. Progressive "Edu- Kits" Inc., 1189 Broadway, Dept. 595 -Dij Hewlett, N.Y. 11557 r -I PRINTED CIRCUITRY I I Please rush me free literature describing the Progressive At no increase in price, the "Edu -Kit°' now includes Printed Circuitry. You build I Radio -TV Course with Edu -Kits. No Salesman will call. a Printed Circuit Signal Injector, a unique servicing instrument that can detect many Radio and TV troubles. This revolutionary new technique of radio construction is now NAME becoming popular in commercial radio and TV sets. A Printed Circuit is a special insulated I ADDRESS chassis on which has been deposited a con- ducting material which takes the place of wiring. The various parts are merely plugged I CITY & STATE ZIP. in and soldered to terminals. Printed Circuitry is the basis of modern Automation Electronics. A knowledge of this PROGRESSIVE subject is a necessity today for. anyone in- "EDU-KITS" INC. terested in Electronics. 1189 Broadway, Dept. 595 -DJ Hewlett, N.Y. 11557

CIRCLE 22 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS/March-April 1979 23 ril FI REPOR shown here in their DiscKit set. It his tS HIFl REPORTS HIFl an antistatic pistol (you hold the muz- your SPORTS HIFl REPORTS HIFl hL zel over the surface of the record and Extend PORTS HIFl REPORTS HIFl REPO, give it four or five good shots), an -I REPORTS HIFl REPORTS HIFl REPU REPORTS HIFl REPORTS HIFl REPOR1 CIRCLE 55 ON READER SERVICE COUPON listening FI REPORTS HIFl REPORTS HIFI REPOR1 distance HIFl REPORTS El REPORTS HIFl REPORTS HIFl REPORTS I.FI REPORTS HIFl REPORTS HIFl REPOR. with a I1= REPORTS HIFl REPORTS HIFl REPORT -1 REPORTS HIFl REPORTS HIFl REP( 'SPORTS HIFI REPORTS HIFl REPf `PORTS HIFl REPORTS HIFl P' FINCO... -PORTS HiFi REPORTS N' Discwasher DiscKit ü( FE REPORTc SC -1 stylus cleaner, a special record FM Spruce up your sounds without cleaning squeegee, and D -3 cleaning auto spending a fist -full of dollars. By fluid. All this plus the walnut storage Gordon Sell tray which has storage space for tools and extra cartridges retails for $46.00. amplifier AFTER YEARS OF CAREFUL STUDY I When cleaning records it is very im- have come to the conclusion that there portant to have the proper work sur- are two distinct types of audiophiles - face -you could be cleaning one side the single -play turntable type and the while scratching or linting up the other. automatic turntable type. The extreme single play'er, as I call him, handles his CIRCLE 60 ON LPs only when wearing white, lint -free 9 S.f y;f READER SERVICE ,*01 Drl gloves while the extreme automatic'er - COUPON shuffles records like a poker player on a winning streak. Most of us are no where near these extremes but we do tend to belong to one group or the other. No matter what group you are in Sound Guard Work Pad you either want to, or need to take FINCO's better care of your hi -fi records and Sound Guard makes its non -slip, lint - equipment, and there is no shortage of free Record Care Work Pad to prevent self contained top gadgets to help you do this. Record such occurances. Retails for $7.95. Auto FM cleaners, dust removers, anti -static guns, There are a lot of self tracking rec- of the line stylus gauges and cleaners, tape -head ord cleaners on the market. A popular Amplifier with cleaners, head demagnetizers, and all one is TDB (The Dust Bug) by Watts kinds of record and tape storage sys- which can be mounted in a convenient variable gain control tems. In this issue's Hi -Fi Report I'll spot on your turntable. The combined tell you about what's available. action of a cleaning -fluid- soaked roller 16 Times Increases Signal up to Record Whatsits. One of the more CIRCLE 65 ON READER SERVICE COUPON Will Not Overload in Strong Signal interesting new approaches to record Areas care is Empire Scientific's Disco Film. Provides Crisp, Clear FM Just spread the film over your LP. Reception Switch for FM and AM Reception No Adverse Effect on AM Reception CIRCLE 50 ON Extends FM Reception Range READER SERVICE Watts TDB (The Dust Bug) L.E.D. Indicator Light COUPON Linear Potentiometer Gain and a brush does the job. TDB re- Control tails for $8.99 including cleaning fluid. problems can be SOLID State - Dual MOSFET Many turntable Circuitry traced to vibration in the base. To help CIRCLE 57 ON gain FM READER SERVICE Highest COUPON auto amplifier available... Empire Scientific Disco Film When it dries you peel off the film and write for catalog it takes all the dust and grit with it. of No. 20 -852, Dept. EE 3_79 One $29.95 applicator will take care THE FINNEY COMPANY 70 LPs. Audio Technica Insulators 34 West Interstate Street, Bedford, Ohw 44146 Discwasher, the General Motors of (216) 232 -6161 record care, has a very complete line cure such problems Audio Technica of products. A good cross section is manufactures a set of vibration insula- CIRCLE 13 ON READER SERVICE COUPON ELECTRONICS /March -April 1979 24 ELEMENTARY HOW! An Affordable Digital LED Readout Receiver. that Brings. You Exciting Global News, Action ánd Entertainment, - from 10 kHz to 30 MHz Continuous, in- 30 Bands!

Tune in the worlc with (D Six -range preselec-

R I'st7( the Realistic DX -300, tor, with LED indicators, the general coverage bocsts RF signals and receiver that gives you matches the DX -300 to features never offered at your antenna. this low price. Enjoy 0 Three -way power: English as well as operates on AC, 8 op- foreign -language -3 tional "C" batteries, or shortwave broadcasts frcm world capitals and external 12VDC Automatic AC /battery every corner of tre glece. Pick up aviation switching, too. weather and marine SSB. Get WWV time 1, Quartz -synthesized accuracy and a big signals and the Voice cf America. hear CB 5 -digit frequency readout replace mechanical and worldwide Anateu -adio conversations dials with all- electronic precision -you can and listen to standard AM from all stations dial directly to any statior and re -tune to it across the USA AccLracy, resetabi ity and easily. No more searching for stations. ease of tuning are increcible. Just set the dial to the exact frequency of the station ycu want (4) Dual -gate MOSFET frcnt end, synthesized

-105 international SW stations are I sted in drift -cancelling trip e- conversion mixer the owner's manual alone. For finest system, and 6 -e ement ceramic filter for super reception from any station, the DX -30J has a sensitivity and f-eedom from 3 -step RF attenuatcr, audio bandwidth and RF adjacent -channel interference. gain controls, and two antenna inputs. And ® Relative signal strength and battery what versatility: terminals for remote receiver condition meter. Illuminated for easy reading . muting, tape racorcing, screw -cn whip antenna for portable ase. built -in oscillator © Product detector and fine-tuning control and key jack for code practice. U.L. listed, of for outstandingg receptionreca p of code and SSB. course. Step up to great listening at a great Audio power IC, 1.5 watts output, and a price. Only 379.95` ouys you the world! large speaker for high -intelligibility sound.

DISCOVER REALISTIC: SOLD ONLY AT ftadio J'haek A DIVISION OF TAVDY CORPORATION FORT WORTH. TEXAS 76'02 OVER 7000 LOCATIONS IN VINE COUNTRIES

'Retail price may vary at individual sbres and daaers. HI -FI REPORTS

tors on which you can mount your turntable. These are also adjustable for height and Audio Technica provides a for the Experimenter? compact bubble level so that you can CRYSTALS and KITS make your installation perfectly level. INTERNATIONAL Retails for $24.95. Circle number 57 .02'/ Calibration Tolerance for information about this and the rest OF -1 OSCILLATOR EXPERIMENTER of Audio Technica's extensive line of CRYSTALS audio accessories. $425 (HC 6/U Holder) Tape Tricks. For the tape recording ea. $475 fan preventive maintenance basically ea. clean- The OF -1 oscillator is a comes down to two things, head resistor /capacitor circuit Cat. No. Specifications II ing and head demagnetizing. The best providing oscillation over a range of frequen- 031300 3 to 20 MHz - For use in OF -IL OSC when ordering. thing I've seen for the later, if you have cies by inserting the desired crystal. Specify 2 to 22 MHz, OF -1 LO, Cat. No. 035108. 18 to 60 MHz, 031310 20 to 60 MHz - For use in OF -1H OSC a cassette deck, is TDK's battery - OF -1 HI, Cat. No. 035109. Specify when ordering. Specify when ordering. powered head demagnetizer, model

Enclose payment with order (no COD) Shipping CIRCLE 67 ON READER SERVICE COUPON (inside U.S.. Canada and Mexico only) MXX-1 Transistor RF Mixer and postage will be prepaid by International Prices quoted for 3 to 20 MHz, Cat. No. 035105 U.S.. Canada and Mexico orders only. Orders for 20 to 170 MHz, Cat. No. 035106 $5.50 ea. shipment to other countries will be quoted on re- SAX -1 Transistor RF Amp quest Price subject to change. Address orders to 3 to 20 MHz, Cat. No. 035102 PO Box 32497 20 to 170 MHz Cat. No. 035103 $5.50 ea. M/S Dept.. Oklahoma -City. Oklahoma 73132 BAX -1 Broadband Amp ea. 20 Hz to 150 MHz Cat. No. 035107 $5.75 WRITE FOR BROCHURE

International Crystal Mfg. Co., Inc. 10 North Lee Oklahoma City. Oklahoma 73102 m n TDK Head Demagnetizer CIRCLE 14 ON READER SERVICE COUPON HD -l. It looks just like a normal cassette cartridge and it is inserted in the same way. Just turn it on for a few seconds and the job is done. Reel -to- reel head demagnetizers are available BY POPULAR from many tape and tape recorder manufacturers. First Head cleaning is a real trouble spot The World's DEMAND! for the tape recordist. Heads are often Miniature $20 Gold Piece buried away in the machine and you MS -215 Dual Trace need to be some sort of magician to get Miniscope CIRCLE 72 ON READER SERVICE COUPON

.INISiammommumt

)41)I.II1 I I k tR 1T 1:111.11 - tt\1.1 I..s1.i

J. 11-111 \ll d lai. p Ih annnonr, .111 Gold fier - the minting of :1w w idd- fir-S miniature in maid 1I Lars: mold You have a rare oppormnm to possess thr world's firm miniature 820 00 Gold Pin, in solid 14 karat gold This Loin is an exquisite duplicate minted in emits the same manner With Rechargeable as the first Saint- Gauden's 820 00 Gold Pieor Batteries & Charger Unit. $435 shuck at the U S Mint in I'Oin ACTUAL Maxell Tape Head Care Kit J. DeNINNO & CO. I 15- megahertz bandwidth. Pike 5, Viewmont Village 9mm at them. Maxell has brought out a Scranton. Pa. 18508 (717)461 -0203 External & internal trigger. super tape recorder care kit that not WE HAVE ALSO MADE THIS BEAUTIFUL COIN only has tape cleaning pads and clean- INTO A PENDANT WITH MATCHING E ARRINGS. Auto or line sync modes. ing solution but contains a set of spe- The Pendant With The Matching Ear- cially shaped applicators that make 18" Chain, rings, Containing An Power usage -<15 W. a snap. The kit also has a Also 14 Karat Gold Two Coins Sells cleaning For Only. recorder care that's Sells For Only. Battery line operation. booklet on tape 825.95 $29.95 or well worth the entire kit's $8.95 sug- ALL Con gested retail price. Pend.mt w'Chain 2.9" H x 6.4" W x 8.0" D. THREE Just remember that the secret to t r nn gs is 1 in tip -top condition ITEMS la ts9I Non -Linear Systems, Inc. keeping records ALL N HANDSOME GIFT SOS Originator of the digital voltmeter. a combination of maintenance and Box N, Del Mer, California 92014 storage -keep them away from direct Telephone (714) 755-1134 TWO 910.3221132 CIRCLE 16 ON READER SERVICE COUPON sunlight, heat and free from dirt and CIRCLE 17 ON READER SERVICE COUPON dust. -April 1979 26 ELEMENTARY ELECTRONICS /March e-IL. e , M.. NOW: GETA BIG 20 REBATE ON THESE BES1LSELUNG NO-CRYSTAL BEARCAT SCANNERS.

Now, you can get all the on -the- Bearcat 210. The amazing, 10 -chan- built -in clock. scene police calls, fire calls, any nel, 5-band Scanner that brings $20 back on the incredible Bearcat emergency informat on the second it home over 6000 frequencies as easy 250. America's only 50- channel, happens -and a tzg $20 factory as using a pushbutton phone. Gives micro-processor controlled Scanner rebate -when you buy any of thee you automatic search, selective scan that searches, stores, and all but best -selling Bearcat no- crystal delay, and more. thinks for you. Scanners. $20 back on the new Bearcat 211. See your Bearcat Dealer for our $20 back on the.Scanners Amer- America's mid -priced, spaceage cir- $20 rebate details -good from Feb. ica wants most. Because they're all cuitry Scanner that gives you 18- 1, 1979 thru March 31, 1979. no-crystal, fully synthesized models channel, 6 -band capability at the Then pick your kind of Bearcat that operate with incredible push- touch of a button. Plus direct chan- Scanner. We'll send you back a button ease. nel access, dual scan speed, check tor $20. Good deal. $20 back on the automatic squelch. Even a

BEARCAT SCANNERS FOLLOW THE LEADER TO REAL EXCITEMENT. ELEMENTARY CIRCLE no ON READER SERVICE COUPON ELECTRONICS March -April 1979 27 Train with NTS for the Microcomputers, digital the first name

::.,.t Rn_,...... __.,a_ m.._ ,<_' t ,n..1111_V*...... _u,...,,U_ Mee . L

The world of electronics is daily becoming more background in electronic systems. Kits and lessons challenging. Technology is growing more. specialized, are designed to work together to demonstrate and the importance of digital systems increases electronic principles and applications. The kit -building every day. Test instruments, home entertainment not only shows you how electronic hardware units and industrial control systems are all going functions, but how various circuit designs accomplish digital. And now, NTS training programs include a different purposes. Your lessons guide you through wider choice of solid -state and digital equipment than any number of experiments associated with many ever before offered in any home study course: projects. This is the Project -Method, and it works. Advanced NTS /Heath digital color TV (25" diagonal Step-by -step, you learn how and why digital with optional programming capability), NTS /Heath electronics has become a part of our world, and the microcomputer, digital test equipment, digital stereo even bigger role it is sure to play in the future. receiver (70 watts per channel), NTS compu- trainer, Whether you are looking for training in Consumer, plus much more state -of- the -art equipment to make Commercial, or Industrial electronics, NTS offers your training exciting and relevant. fourteen courses, some basic, many advanced, in The equipment you receive with NTS training several areas of electronics. An all -new full -color programs is selected to provide you with a solid NTS catalog shows you what each course covers,

28 ELEMENTARY ELECTRONICS /March -April 1979 electronics of the future. systems and more...from in home study.

and every piece of equipment included. rl._____ ism __ 1 Send for it today, and see for yourself what's really NATIONAL TECHNICAL SCHOOLS Dept. 222 -039 4000 South Figueroa Street, Los Angeles, California 90037 happening in electronics training technology at NTS. I Please send FREE Color Catalog and Sample Lesson. I Find out how much has changed, and what new Color TV Servicing directions the field is taking. You'll probably want to B & W TV and Radio Servicing I FCC License Course I be a part of it. Electronic Communications Electronics Technology It's free. Just mail the card or coupon. Today. I Audio Electronics Servicing I Digital Electronics I MicroComputers /MicroProcessors I NO OBLIGATION. NO SALESMAN WILL CALL. APPROVED FOR VETERAN TRAINING. I Name I Address Apartment Number Age I I NATIONAL _ SCHOOLS City TECHNICAL -TRADE TRAINING SINCE 1905 State lip Resident and Home -Study Schools I Check if interested in G.I. Bill information. I 4000 South Figueroa St., Los Angeles, Calif. 90037 Check if interested ONLY in classroom training in Los ti MI= - Ili ti

ELEMENTARY ELECTRONICS /March -April 1979 31 From Dynascan Corporation

.. , , ... things packages 4O3A Good ' small ,PRECISIDN CO lH=1 DO i SWEEP RANGE come EX VARI 1k-10k 1Ok 100k SWEEP 100-1k 10-100

ACTUAL -SIZE PHOTO (5.24" x 7.25" x 11.2 ") Model 1403A $250 ...like B &K- PRECISION'S 5MHz 3" SCOPE

The B &K- PRECISION Model 1403A is living proof This feature, combined with a sturdy integral han- of that old adage. We've designed into our popular dle makes the 1403A ideal for field service appli- 3" scope, full features and high performance...all cations. When bench or storage space is at a pre- in an ultra- compact cabinet. mium, you'll appreciate the convenient size even more. The high- brightness 3" CRT produces sharp wave- small forms on a P31 blue phosphor. A smoked glass We think the 1403A is the most cost -effective graticule helps increase image contrast for clear scope available. Compare the specs, features, size agree. Avail- viewing in the brightest rooms. The 1403A is con- and price, and we're sure that you'll the LC -14 carrying case and servatively rated at a 5MHz bandwidth for 10mV /div. able options include vertical sensitivity and will typically sync on sig- PR -21 isolation /direct probe. nals at 8MHz. This rugged small scope has DC For immediate delivery, contact your amplifiers on both vertical and horizontal axes B &K- PRECISION distributor. and direct deflection,terminals for waveform display up to 450MHz! Maximum input is 600Vp -p. Input impedance is 1 megohm for both vertical and DYNASCAN horizontal inputs. A Z -axis is also provided. :4KPRECISION CORPORATION -9087 Perhaps the most striking feature of the 1403A is 6460 W. Cortland Street, Chicago, IL 60635 312/889 Atlas Electronics. Ontario its ultra- compact size (HWD), 5.24 x 7.44 x 11.2 ". In Canada: International Sales. Empire Exporters, Inc.. 270 Newtown Road, Plainview. L.I., NY 1t803

32 CIRCLE 108 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 The Fine Art of Buying Electronic Parts by Walter Sikonowiz

An inflation fighter's guide to buying components

Who are these specialists? They are the mail -order businesses that advertise in the back pages of ELEMENTARY ELECTRONICS (as well as other publications). Some of these companies restrict themselves to new merchandise, which they sell at very agreeable rates because of low overhead. Others sell only surplus, that is, unused components obtained from manufacturers willing to sacrifice some inventory for ready cash. A component's appearance on the surplus market can be caused by a multitude of economic factors which are unfortunate for the manufacturer, but a windfall for you, the sharp -eyed and observant buyer. SK A GROUP of electronics enthu- 8th St., Fort Worth, Texas, 76102), New or Surplus? How can you tell siasts what the single most difficult and Lafayette Electronics (PO Box whether merchandise is brand new or part of project building is, and 428, Syosset, New York, 11791) . These unused surplus? In many instances, the more often than not the reply will be, are the general practitioners of elec- catalog will tell you. If not, there is one "Buying the #$% &* parts." Such an tronics; they dispense a little of just sure indication: If the merchandise is attitude is not unwarranted because, about everything a hobbyist could need. being sold for a fraction of the retail try as you may, you will never find one The Specialists. Once Ohm's Syn- price you would expect to pay, it's sur- distributor capable of supplying all the drome takes hold, however, and your plus. Three firms that deal exclusively parts you need. Even so, there is no sales resistance rises in the face of inin surplus are Delta Electronics (PO reason for the incredible amount of dif- flation (and limited selection), it's time Box 2, 7 Oakland St., Amesbury, ficulty experienced by some people. to see a specialist. This might be any Massachusetts, 01913), B &F Enter- Once you understand what's available, one of several firms selling certain prises (119 Foster St., Peabody, Mas- and who's selling, shopping for parts products, such as integrated circuits, sachtisetts, 01960), and John Meshna becomes downright easy. and little else. Because of specialization, Inc. (PO Box 62, E. Lynn, Massachu- The Big Four. You start by collect- these companies can afford to have setts, 01904). Others, like Poly Paks ing catalogs; the more the better. Ten very complete inventories of selected (PO Box 942, South Lynnfield, Mass., will get you by, but twenty is not too merchandise. Furthermore, although 01940), or Herbach & Rademan (401 large a figure. Begin with the Big 4: you might expect a specialist to slap E. Erie Ave., Philadelphia, Penn., Burstein -Applebee (3199 Mercier St., you with a fat fee, in most cases just 19134), offer a mixture of surplus and Kansas City, Missouri, 64111), Radio the opposite will happen; you'll save brand new stock. Regardless of whether Shack (everywhere), Allied (401 E. money, and that makes it worthwhile. the merchandise is new or surplus, all

ELEMENTARY ELECTRONICS /March -April 1979 33 GPARTS BUYING

You can buy bulk com- firms offer some guarantee of satisfac- ponents at next -to- if you they list the percentage yield. nothing prices tion or surplus In order to get better acquainted buy untested, parts. Poly Paks is a with the various suppliers, let's survey popular bulk supplier the market item -by -item. In the follow- and two of their packs ing paragraphs, whenever a specific are shown here. Most company is mentioned in connection of the parts are use- with a component, it is only because able. that firm is particularly strong in a certain area. Some degree of overlap- ping does exist among all firms, however, so don't assume that any one supplier is being recommended to the some, its service is like the fabled that are most frequently used: 2N3906 exclusion of all others. "greased lightning." PNPs, 2N3904 NPNs, 1N914 switch- Integrated Circuits. Although hu- Occasionally, you are going to re- ing diodes, 1N4003 rectifiers and so man life is based on the chemistry of ceive a dud. When this happens, it's forth. Avoid the high -wattage zener carbon, it is the chemistry of silicon best not to go berserk. A calm request diodes now appearing in surplus. To- that now forms the basis for our busi- for a replacement is usually accom- day, integrated circuits have supplant- ness and industry, thanks to the in- modated very quickly. After all, these ed zeners as regulators at all but the tegrated circuit. Because of their tre- companies want your continued busi- lowest power levels. mendous importance, integrated circuits ness in the future. As a precautionary Resistors. Buying from one of the are sold by almost every electronics measure, you might consider ordering larger retailers, you can expect to pay supplier, big or small. You'll find that two of each IC. The chances of getting around 10 cents a piece for carbon - the Big 4 have quite respectable IC one dud are so small that the proba- composition resistors. Compare that inventories, but prices are relatively bility of receiving two duds simulta- with the typical 4 -cent selling price high, and selection is not complete. neously is infinitesimal. You can use from the specialist firms, and the Jameco Electronics (1021 Howard St., the extra integrated circuit chip, if it choice of a supplier is obvious. Resis- San Carlos, Calif., 94070), and An- is a good one, in a future project. tors are one class of component that crona Corp. (PO Box 2208, Culver Discrete Semiconductors. This cat- can be sensibly stockpiled. Buy half - City, Calif., 90230) feature perhaps egory is an exceptionally broad one. watters with a 5% tolerance. They the widest selections of ICs; linear, Included are: bipolar transistors, FETs, cost only a bit more than 10%a resistors TTL, CMOS, DTL, ECL, LSI and so SCRs, diodes, UJTs and so on. As in and save you the trouble of stocking forth. Jade Computer Products also of- the case of ICs, almost everyone sells two tolerances. fers a very good selection of integrated some discrete semiconductors, but few Power resistors, with ratings from 5 circuits in their comprehensive catalog. vendors stock each part number. Be- to 100 watts, are available from the Circuit Specialists (PO Box 3047, fore giving up an elusive part, try either surplus dealers at incredible prices. sup- Scottsdale, Ariz., 85257) is a nice Hanifin Electronics (PO Box 188, Buy a small assortment. Power company to do business with, since they Philadelphia, Penn., 19405), or the plies and audio amps often need dum- require no minimum -size order. In ad- Ancrona Corp. These two firms have my loads during checkout, and for such resistors are dition to a wide range of the standard perhaps the most extensive listings of purposes these high -power ICs, Circuit Specialists carries special discrete semiconductors available. ideal. If you do not have exactly the serial and numbers from RCA, Motorola, and Most suppliers offer special discounts right resistance at hand, use whose net resis- Mostek. Digi -Key (PO Box 677, Thief to encourage volume buying of parts. parallel combinations River Falls, Minn., 56701) also fea- This appeals directly to the squirrel - tance is the desired value. those high -class resis- tures a wide assortment, including some ish instincts of the electronics hobby- Don't forget units with circuits difficult to find elsewhere. Last, ist, but be careful. Just like that greedy tors, the metal -film precision You can but not least, there is Solid State Sales little tree -dweller, you will probably tolerances of 1% or better. retailers, but (PO Box 74A, Somerville, Mass., horde more than you can ever use. If get these from the larger 02143). Although this company's se- you must stockpile parts, do it sensi- at 60 cents to one dollar apiece (often -piece minimum order) who lection may be a trifle smaller than bly. Choose those discrete components with a ten

a useful aid to sorting Try to build up a supply of transistors, Since a great many people have trouble remembering the color code, diodes, ICs and electro- optical devices. surplus resistors is an old tie box with the color code marked inside the lid.

ELEMENTARY ELECTRONICS/ March -April 1979 34 ADDRESSES Digital Research Corp. Mouser Electronics, OF PARTS P.O. Box 401247B, Garland, TX 75010 11511 Woodside Ave. SUPPLIERS: Lakeside, CA 92040 Electronics Distributors, Inc. Ace Electronics New Tone Electronics, P.O. Box 1738 4900 N. Elston Bloomfield, NJ 07003 5400 Mitchelldale Chicago, IL 60630 Houston, TX 77092 Olson Electronics Active Electronics Sales Corp. ETCO Electronics, 521 Fifth Ave. 260 S. Forge St. Akron, OH 44327 12 Merser Rd., Natick, MA 01701 New York, NY 10017 Optoe ectronics ALdelco, 228 E. Babylon Tpk. Formula International, Inc. 12603 Crenshaw Blvd. 5821 N.E. 14th Avenue Merrick, N.Y. 11566 FL Hawthorne, CA 90250 Fort Lauderdale, 33334 Allied Electronics, 401 E. 8th St. Poly Paks, P.O. Box 942 Fort Worth, TX 76102 Fuji -Svea, P.O. Box 3375 Torrance, CA 90510 South Lynnfield, MA 01904 Ancrona Corp., P.O. Box 2208 Quest, P.O. Box 4430 Culver City, CA 90230 Herbach and Rademan, 401 E. Erie Ave. Philadelphia, PA 19134 Santa Clara, CA 95054 B &F Enterprises, 119 Foster St. HobbyWorld, 19355 Business Radio Hut Peabody, MA 01960 P.O. Box Center Dr., Northridge, CA 19324 401247 Bullet Electronics, P.O. Box 1944 Dallas, TX 75238 Integrated Electronics Dallas, TX 75219 Radio Shack, Consult your local 540 Weddell Dr., Sunnyvale, CA 94086 phone book Burstein -Applebee, 3199 Merceir St. Kansas City, MO 64111 International Electronics Unlimited Ramsey Electronics Village Square P.O. Box 449 Box 4072 Chaney Electronics, P.O. Box 27038 Carmel Valley, CA 93924 Roche9ter, NY 14610 Denver, CO 80227 Jade Computer Products Signal Transformer Co., Circuit Specialists, P.O. Box 3047 5351 W. 144th St. 500 Bayview Ave. Scottsdale, AZ 85257 Lawndale, CA 90260 Inwood, NY 11696 Delta Electronics, P.O. Box 2 Jameco Electronics, 1021 Howard St. Solid State Sales, P.O. Box 74A 7 Oakland St., Amesbury, MA 01913 San Carlos, CA 94070 Somer%.ille, MA 02143

Diamondback Electronics Co. John Meshna, Inc., P.O. Box 62 Steven Products, P.O. Box 698 P.O. Box 194, Spring Valley, IL 61362 East Lynn, MA 01904 Melville, NY 11746

Digi -Key, P.O. Box 677 Lafayette Electronics, P.O. Box 428 Surplus Electronics Corp. Theif River Falls, MN 56701 Syosset, NY 11791 7294 NLW. 54th St., Miami, FL 33166 needs them? Actually, for certain ultra - pacitor that money can buy is the side this range, too.) Standard toler- stable or low-noise circuits, precision polystyrene type. It also happens to be ances are 20% and 10%. A great resistors are mandatory. Active filters, one of the cheapest, a fortunate coin- many firms carry mylar capacitors. accurate voltage dividers, and analog - cidence. Polystyrenes are available in Above 1 -uF, most capacitors are alu- computer circuits are but a few exam- the range from 5 pF to 0.5 -uF, but minum electrolytics, which are polar- ples. When you really need precision above .01 -uF, they begin to get bulky ized devices. One of their most im- resistors, Hanifin Electronics can sup- and expensive. Your best and most portant functions is filtering, particular- ply them at about 15 cents each. But complete sources for these capacitors ly in AC power supplies. Tolerances because Hanifin is an industrial sup- are Burstein -Applebee and Allied (ad- tend to be relatively loose since ap- plier, do not send in a 750 order; fif- dresses supplied previously). Standard plications rarely call for very precise teen dollars worth is a realistic mini- tolerances are 5% (super for a capaci- electrolytic capacitors. Capacitances as mum. Since Hanifin offers lots of good- tor), with 2.5% and 1% available at high as 40,000 -uF and beyond are ies besides resistors, you should have higher prices. available to the adventuresome hobbyist. no trouble putting together a good - In the range from 0.01 -uF to 1 -uF, The aluminum electrolytic has a sized, worthwhile order of resistors. you are best off with mylar (polyester) more sophisticated cousin, the tanta- Capacitors. The best all- around ca- capacitors. (Mylars are available out- lum capacitor, which is commonly available in capacitances as high as several hundred microfarads. Relative to the aluminum electrolytic, the tanta- The best way to build up your parts inventory lum features tighter tolerances (10% is to salvage useable typically), lower leakage, and smaller components from size for equivalent capacitance. As a junked pieces of elec- result, tantalums are preferred over tronics gear. Trans- aluminum electrolytics in timing appli- formers, switches, po- cations. Both electrolytic types are tentiometers, crystals stocked by many distributors. and coils are always Surplus capacitors are available, with handy to have. perhaps the best source being Poly Paks (see above), at least in terms of variety. If you do buy surplus capaci-

ELEMENTARY ELECTRONICS /March -April 1979 35 IG PARTS BUYING

tors, play it safe and check each one on a capacitance meter. Ceramic by- pass capacitors for digital logic are available very cheaply as surplus, and so too are mylars. On the other hand, be very cautious when buying surplus aluminum electrolytic capacitors. They have a limited shelf life, and once they dry out, they are useless. Most dealers are scrupulous enough not to do this to you, but you can end up with a relic of the 1950's that looks more like an artillery shell than a capacitor. Choose these components very carefully. Potentiometers. New pots cost about the same no matter where you buy Plugs, jacks, aligator clips, battery clips terminal lugs and IC transistor holders are always them. Imported units may sell for less, missing jut when you need them. They can often be purchased in bulk fora large savings. but cheap materials yield an inferior They are found on parts store display boards and in parts salvage bins. device, one that is often difficult to turn because of high- friction bearings. tronic switching to route calls. The egory, so let's focus on new merchan- While imports are excellent for ex- result of all this phasing -out is a sur- dise. The simplest PC methods involve perimenting, it always pays in the long plus market chock full of relays at placement of a pattern directly on cop- run to use only top -quality potentio- bargain prices. per -clad board. These are fine in the meters in your construction projects. Despite the decline in its commer- beginning, but for serious experiment- Surplus pots can save you a lot of cial popularity, the relay still possesses ers, photographic techniques are a money, but read the fine print closely. some admirable qualities, such as ex- must. Not only do photographic meth- Pay attention to shaft length. Some cellent driver /load isolation and mini- ods yield neater copper traces and a units are intended for screwdriver ad- mal temperature sensitivity. Further- greater density of components on your justment and have short, slotted shafts more, it happens to be one of the easi- board, they also allow any number of which cannot accept a knob. In addi- est devices for the beginner to under- boards to be produced from a single tion, watch out for strange tapers, such stand and use. All things considered, piece of artwork. as "reverse logarithmic." Pots speci- it makes sense to take advantage of the Photographic PC processing can fied as having either "linear" or "au- surplus bargains now, while they last. best be learned from one of the kits dio" tapers are the ones most usually Power Transformers. Here is an- offered by various manufacturers. You called for in projects. other item carried by almost every sup- do not need expensive equipment like For some reason, wirewound pots plier, but inventories are generally lim- a camera or enlarger. All necessary ma- seem to abound in surplus. These are ited in scope. When your application terials and instructions come in the fine for low -frequency work, often at demands just the right transformer, it kit. These PC kits may employ either high power. But wirewounds have poor pays to be able to order directly from negative or positive photographic proc- resolution and should never be used in the manufacturer. Signal Transformer esses, which differ from one another a circuit where very precise adjust- Co. (500 Bayview Ave., Inwood, N.Y., principally in the method used to pre- ments must be made. For the bulk of 11696) offers a wide array of trans- pare a board's artwork. Positive meth- your experimenting, standard carbon - formers, from tiny, PC -mount devices ods are perhaps easier for a beginner composition pots are your best choice. to mammoth, kilowatt isolation trans- to visualize, but negative kits seem to Slide pots are a great convenience formers. Other makers also offer di- be equally popular. Most suppliers car- in audio work, especially if you are verse selections, but some may not ry at least one brand of PC kit, if not building a mixer or music synthesizer. encourage direct mail ordering. more. Choose one that fits your needs Many outlets carry them, but most Undoubtedly the most economical and budget. You'll find the profession- units have too short a path of travel way of securing a transformer is al- looking results to be well worth the it right. (11/4 inches) to be really useful. Slide through a surplus dealer like Delta. extra effort it takes to do pots with twice the adjustment range Many kinds of transformers end up as Although only the tip of the iceberg are preferable, and they can be pur- surplus, and with just a little luck you has been exposed here, you should chased at reasonable cost from Mouser can find one to suit your purpo3es. Dis- have a pretty good idea of how to find Electronics (11511 Woodside Ave., counts greater than 75% off list are supplies by now. To obtain copies of Lakeside, Calif., 92040). common, so the money you save may the catalogs you want, write directly to Relays. These may well share the be substantial. This is especially true if the companies mentioned in the text. fate of the dodo, thanks to fast and you are planning to construct some- Note that our coverage has been by no reliable solid -state switchers like triacs, thing big such as a high -powered audio means exhaustive. Undoubtedly other SCRs and transistors. Industrial control amplifier. Transformers from some of worthwhile catalogs are available, so systems that once bristled with relays the best amps ever to shake a loud- hunt carefully through the back pages, and cam -actuated microswitches now speaker end up as surplus, victims of too. Remember, all companies stock rely on digital logic and thyristors. Even design changes and competition. much more merchandise than they can Ma Bell, at one time the patron saint PC Supplies. There is no surplus economically include in a single mag- of relay manufacturers, now uses elec- material worth mentioning in this cat- azine advertisement.

ELECTRONICS /March -April 1979 36 ELEMENTARY Sleep for 1001 peaceful nights with this electronic genie standing faithful guard

by Anthony J. Caristi

BUILD CYCLOPS. With his space age vied by a flashing light, or you can audio pulses produced, when ampli- magic eye he will stand guard over even place Cyclops in your car and fied and fed to a loudspeaker, is a sim- your house or property and sound have an unique musical horn. This ulation of the familiar whooping sound a musical alarm if an intrusion should and all the other features of Cyclops which is characteristic of some alarms. occur. He does this without the use of can be performed by a single electronic C4 determines the rate at which the any special light source by monitoring assembly which can be constructed at circuit changes from one tone to the the ambient light intensity falling on low cost. Simple modifications of the next, and can be changed to suit in- his eye. Cyclops performs his guard circuit will permit you to use Cyclops dividual tastes. ICI has an additional duty with a very meager appetite for for whatever purpose you desire. digital circuit which produces a second power, consuming only 1h watt while About the Circuit. The eye and heart set of random musical tones which he is on duty. If an intrusion should of Cyclops is a specialized integrated might be described as "Close Encount- occur, Cyclops responds by sounding circuit which is the result of a marriage ers" music. When the chip is in this an attention getting alarm, and auto- betweeri a photodiode and a digital mode of operation, it is also capable of matically resets himself after a speci- and linear circuit on a single chip. Such flashing a 6 volt light bulb in time with fied time delay selected by you. a device is called an Optolinear and is the music. You can also take advantage of available to you from the source spe- Control of the operation of IC1 is Cyclops' unfailing eye by using him as cified in the parts list for Cyclops. This accomplished by feeding a positive volt- an automatic doorbell. When someone is the 14 -pin IC chip shown in the age to either or both control input approaches the door of your house photograph of the Cyclops PC board. terminals, pins 11 and 14. When ter- and casts a shadow, the resulting change in light intensity falling upon Cyclops will cause him to sound a short and pleasant series of musical notes. You The Optolinear IC can extend his detection range by plac- chip is the eye of ing him in your driveway or garage to Cyclops. This nifty announce the arrival of an automobile little package de- at night, when he sees the headlights tects small changes of a car. in the ambient Versatility. Cyclops is quite versatile lighting conditions and can be used for purposes other and triggers the than an intrusion alarm or automatic alarm. You can use this handy device doorbell. For example, you can con - as a burglar alarm struct an electronic rifle range by plac- or as a household ing Cyclops' eye at the center of a remote controller. bull's eye and shooting with a beam of light from a home -made ray gun. Each time the bull's eye is hit, a series of musical tones will sound. An electronic IC1 is an integrated circuit motion minais C and D of the printed circuit ray gun or rifle can be constructed by detector which monitors the ambient are connected together and terminals modifying a small flashlight which light intensity falling on the built -in A and B are open, the circuit is set to emits a narrow beam so that the light photodiode. When a change in light perform as an intrusion alarm. Opening rays are concentrated. In order to pro- intensity occurs, a circuit is triggered the circuit between terminals C and D, duce a "shot," the circuit shown can which produces a series of pulses of and A and B, programs the circuit for be used. This will drive the light bulb varying frequency in the audio range. "Close Encounters" music. Automatic from a charged capacitor and result A digital counter within the chip per- control of terminals A and B of the in a pulse of light. Use a spring loaded mits a specified number of pulses to be circuit is provided by IC2 and IC3, and SPDT switch. generated, and then resets the circuit manual control of terminals C and D Cyclops' built -in musical ability can back to a standby mode to await the is provided by a single pole silde be used as the basis for a "Close En- next change in light intensity falling switch mounted directly on the printed counters" sound generator accompa- upon the photodiode. The series of circuit board.

ELEMENTARY ELECTRONICS /March -April 1979 37 CYCLOPS

Power to drive a loudspeaker is provided by Q2 and Q5 which amplify the low voltage output pulses of ICI and deliver peak currents of up to 1 ampere into the speaker. When ICI is in standby mode, the voltage at the output terminal, pin 1, is about 4 volts. This cuts off both Q2 and Q5 so that current in the loudspeaker is zero. When ICI is activated, Q2 conducts current and provides base drive to Q5 through R3 which acts as a volume control. When the circuit is set for maximum volume, Q5 acts as a switching transistor, driving the loudspeaker with pulses of about 12 volts. The circuit will drive loudspeakers of any impedance. Greatest volume will be ob- Use full -sized printed circuit board template to make your own Cyclops. You might tained with a 3.2 ohm speaker, since this try out one of the new PC kits from Vector that lifts the pattern from a magazine page. this will draw the highest load current from Q5. Peak power delivered to a 3.2 ohm speaker can be as high as 40 with the schematic on the next page. ist. This will help avoid problems when watts when the volume control is set to The printed circuit layout in this the circuit is first placed in operation. maximum. Average power will be article is shown full size as seen from For a slight additional cost, it is strong- much less than this since the circuit the copper side of the printed circuit ly recommended that sockets be used delivers pulses with a duty cycle of board. The component layout is also for the integrated circuits. Their value less than 50%. shown. If possible, make photocopies in a printed circuit assembly cannot be Construction. Cyclops can be con - of the printed circuit, component lay- overemphasized. The use of sockets stucted on a single sided printed cir- out, and schematic diagram and work give you the ability to troubleshoot the cuit board measuring 2'/8 by 41/4 inch- from these copies. This will avoid wear circuit, should a problem exist, in es. This includes all the necessary cir- and tear on the originals which you much less time than if the IC's were cuitry with the exception of the 12 volt will want to keep in good condition for soldered in place. It is extremely dif- power source. If an AC operated pow -. future reference. ficult to remove a multi -pin IC which er supply is desired, it can be added to After etching the printed circuit, go has been soldered into a printed circuit the circuit at the option of the builder. over it with a magnifying glass to pick without destroying the IC or printed A typical power supply circuit is shown up any shorts or opens which may ex- circuit. Do not mount the integrated

This parts location diagram will help you get everything in the right place. This view is of the component side with the parts facing up. The foil PC pattern is on the underside. Building this project is a snap even if you are a beginner.

SPEAKER

POINT B POINT A

ELECTRONICS /March -April 1979 38 ELEMENTARY circuits until instructed to do so in the little heat. Mount Q5 to the printed checkout procedure. circuit board with two 4 -40 screws and The component layout shows con- nuts. Make them tight but not overtight. trol switch S1 and volume contro' R3 Checkout Procedure. The printed cir- mounted directly to the printed circuit cuit assembly should be checked with board. You may want to mount the power applied before installing any of printed circuit board in a small cabinet the integrated circuits in place. This with these components accessible from will avoid damaged components in the the outside. If you are going to use the event of possible short circuits or mis- lamp with the circuit, be sure to place wiring. Apply 12 VDC power to the it so that its light will not fall upon circuit using a battery or AC operated ICI. Should this happen, the additional power supply, observing correct polar- feedback signal from the lamp may ity. Measure the voltage at pin 13 of

cause a circuit malfunction, IC 1 although using the negative side of the DC If Cyclops really appeals to you as a use- no damage will occur. power supply as the meter reference. ful gadget, but you don't have the time or You will note that the power output This should be between +3.5 and experience to put it together, then you transistor, Q5, is mounted to the print- +4.5 volts DC. If the voltage is not might consider ordering Delta Electronics' ed circuit board with no heat sink. within this range, check zener diode Motion Detector. It uses the same IC as None is required since this transistor D1 for a voltage drop of 4.2 to 5.2 Cyclops. It sells for $24.50 in kit form or $69.50 assembled operates as a switch at high current volts. Check also that D1 is mounted fully with NiCad bat- levels, and therefore dissipates very teries and charger. Delta's address is in (Continued on page 85) the parts list of this article.

R7 R8 12 VDC 10,000 47,000 +12VDC VDC R4 C12.1 2,200 IOOpF sR9 RIO R14 QI T 4.7MEG '47,000 4.7 M EG 2N3904

DI C6 TC7220pF *47 220pF C8 R15 .OI pF 4,700 LAMP T R2 OPTIONAL /47,000 -1(-4.,_ 24 8 3 24 83 04 7 --+CIO 7 RI6 2N3904 CI IA 10,000 pF LI 1 -41:)NC- -+ .OIpF NC 47 SEE IS! TEXT 03 555 55556 D pB 2N3904 CII R6 1 T T 4.7pF 7 6 3 13 14 II 02 4,700 ICI OPTOLINEAR 2N3906 C9 RI L 4.7pF 8 9 10 12 5 2 2,200 RII RI3 Parts your problem? 1 1 1 1 1 1 D2 8,200 `1,000 T See HOBBY MART, page 89. LEDI C2 C3 C4 C5 R4. 1 4.7pF 47pF 4.7pF.47pF 5,000 100,000 R 12 VOLUME R5 = 4,700 10 J SPKR -\Q5 2N4231 OFF SHOOT 117 VAC -GUNCIRCUCTICECIRCUIT (SEE TEXT) BI POWER 9VDC= C13 SUPPY 470 p F L2 20 VDC FLASHLIGHT BULB

PARTS LIST FOR CYCLOPS B1 -9 -volt battery L1 -#47 lamp R17- 100,000 -ohm, 1/4 -watt resistor Cl, C3 -47 -uF electrolytic capacitor, 10 VDC L2- flashlight bulb SPKR -3.2 -ohm PM type speaker C2, C4- 4.7 -uF electrolytic capacitor, 10 VDC LED1 -light emitting diode S1 -SPST miniature slide switch C5- 0.47-uF ceramic disc capacitor, 10 VDC al, Q3, Q4- 2N3904 NPN silicon transistor S2 -SPDT momentary-on switch C6, 220 20 VDC C7- -uF electrolytic capacitor, Q2- 2N39 %6 PNP silicon transistor T1 -10-volt, 1.2 amp transformer C8, -uF 10 VDC C10- 0.01 ceramic capacitor, Q5- 2N4231 NPN silicon transistor Misc. -large plastic cabinet (8 in. by 4 in. by C9, 4.7 -uF 20 VDC C11- electrolytic capacitor, R1, R4- 2,200 -ohm, 1/4 -watt resistor 4 in.) screws, spacers, wire, AC plug and zip C12- 100 -uF electrolytic capacitor, 20 VDC R2, R8, R10- 47,000 -ohm, 1/4 -watt resistor cord, etc. C13- 470 -uF electrolytic capacitor, 20 VDC R3 -5,000 -ohm trimmer potentiometer (PC C14- 4,000-uF electrolytic capacitor, 20 VDC board mounting type) Note: ICI is available from: D1- 1N5230 4.7 volt zener diode R5- 100 -ohm, 1/4.watt resistor Delta Electronics D2- 1N4148 silicon diode R6, R12, R15- 4,700 -ohm, 1/4 -watt resistor 7 Oakland St. D3, D4, D5, D6- 1N2069 silicon diode R7, R16- 10,000 -ohm, 1/4 -watt resistor P.O. Box 2 IC1- Optolinear IC (see text for explanation) R9, R14- 4,700,00 -ohm, 1/4 -watt resistor Amesbury, Mass. 01913 IC2 -555 timer R11 -8,200 -ohm, 1/4 -watt resistor Catalog #1072W IC3 -555 timer R13 -1,000 -ohm, 1/4 -watt resistor Price: $8.95

ELEMENTARY ELECTRONICS /March -April 1979 39 a lead instrument. It's a happy, rollick- ing sort of sound: Try it, you'll like it! Now that you have the hang of the rhythm of the country, it's time to head TROPICAL DX upcountry from modern Guatemala City, buzzing west to world- famous Lake Atitlan. Lake Atitlan, ringed by Tune the lands of the ancient Mayan Empire! three volcanoes, features deep blue waters that constantly change ever -so- Ralph Perry slightly in hue, and a dozen Indian vil- lages named for the Apostles perched on its shores. For DX purposes, the im- NOT FAR SOUTH of the border, there because the low frequency "tropical portant one is Santiago (St. James) . lies a land of smoking volcanoes, bands" where the TG (Guatemala) call La Voz de Atitlan, station TGDS, of steaming jungles alive with pan- signs appear are quieter around dawn. presents a good challenge wtih its 120 thers and tropical birds, and of myste- But, if you feel a little static is a small meter band frequency of 2390 kHz. rious stone pyramids. price to pay for a few more Zzzz's, However, this little outlet run by Juan That land is Guatemala and the ad- sleep away! They're there at night, too. Tiney Mendoza, which pumps out a joining Yucatan Peninsula of Mexico, Step number one is to educate those variety of marimba and other indige- the home of primitive Indians de- old "oidos" as the Spanish- speakers say nous tunes, along with educational pro- scended from the famous Mayans. To it (that's ears, chum!). A painless way gramming (in Spanish and Indian dia- experience a direct link with the past, to do that is to tune in on the flagship lects), is sometimes well heard around the with -it DXer can tune in the station of the Mayan Connection, Radio 0230 GMT in the winter. From Jan- "Mayan Connection," a handful of low - Nacional of Guatemala, transmitting uary to June, the main course on the wattage shortwave outlets run by these from downtown Guatemala City, capi- radio menu is spelling lessons. But the great-great -grandsons of the Mayans, tal of the nation that likes to call itself rest of the year, Senor Mendoza said in some using the same language and mu- "Land of Eternal Spring," thanks to a a friendly letter, cultural programming sic popular with their forefathers! pleasant climate that usually keeps it in is the rule. Be sure to write the station How do you get started? Easy, espe- the 70s. Tune in TGW, La Voz (The if you hear them! cially since these flea -powered stations Voice) de Guatemala on its 6180 kHz Another favorite of North American usually poke a king -sized signal into the frequency in the 49 meter band around listeners is perhaps the top station of atmosphere. Added to the bargain is 1200 GMT, when it signs on. Its king - the Mayan Connection: Radio Maya the highly friendly nature of the station sized signal is easy to find without really (Hatch!) de Barillas, noted on 3325 kHz operators (this translates tar fast QSLs trying hard. Just pop up to the top end in the 90 meter band. Radio Maya, for permanent mementos of your tun- and listen for marimba music. located in the pleasant mountain town locals shorten ing experiences!) . Marimba? Why, it's the national mu- of Huehuetenango (the The majority of the stations you'll be sic of Guatemala! It's kind of a bouncy that to the nickname pronounced tuning along the "Mayan Connection" xylophone -type of instrument. There's a "WAY- way "), is under English-speak- are intended solely for a rural Indian saying the marimba is a "smile put to ing operations, but some of the lan- audience that is catching up on spelling music" and one taste of the catchy in- guages used are rather wild! Try Kan - or cultural education ... so don't be strument will prove that to you. Ma- jobal, for instance. No matter -if you surprised at what you hear on some of rimba melodies cover a wide range, hear them, drop a note to. manager these "escuelas radiofonicas" (radio from traditional songs to popular tunes, Loran W. Veithe, who will be pleased experts their 1,000-watt schools) . to "pure marimba" (which the to know you've heard Up And At 'Em! You can scan the air- will tell you is the most authentic type) Gates transmitter. The station offers an waves morning or night to hear these made of gourd sounding- tubes, to or- eye- catching white card with a Mayan but we prefer the early morning hours chestrated selections using marimba as Indian warrior outlined on it in green

The lands of the ancient Mayan Empire still hold some of the most Listen for the catchy beat of the native marimba bands, played atractive scenery in the world, and some of the best DX programs. on authentic gourd instruments to help you find the stations.

1979 40 ELEMENTARY ELECTRONICS /March -April for correct reception reports. (Oh yes. you wish to write, the honcho is Padre If you are really after the big game, Bernadino Ness, director. But don't be shoot for Radio Maya's 120 -meter fre- surprised if XEOM, 6105 kHz your full -data reply, com- R. " PANTERA JUVENIL" quency of 2360 kHz. And, good luck!) plete with pennant, comes from Alberto (YOUNG PANTHER), One of the most easily -logged Guate- Pa Macz, an enterprising individual MERIDA malan stations -but by no means dull - who is announcer, programmer and cor- is La Voz de Nahuala, station TGVN, respondent for R. MAYA DE BARILLAS, Radio Tezulutlan. "HUEHUE" which bills itself as the "Friend of the On our way back to eastern Guate- 3325 kHz Maya -Quiche Culture" broadcasting mala, and the lowlands, we must first from the village of Nahuala, not far check back in at the capital city to from our previous acquaintance, "Hue - make note of the best -known of broad- hue." Try for TGVN on 3360 kHz casters from this country: Radio Cul- about 1200 GMT. tural, TGNA ( "Transmitting the Good ( MIRAMUNO0 ZACAPA You might think the next station News Abroad "), a missionary station 158 1/2 kHz honors that lovely lady who fries eggs heard on 3300 kHz and 5955 kHz, with for you in the morning, Mom, because English at 0300 -0400 G.M.T., and R. CHORTI%, JOCOrAN VOZ that's how you pronounce this outlet Spanish and local languages from 1100 LA 3380 kHz OE NAHUALA located in Cabrican -Huitan: Radio sign-on. TGNA may not exactly fit on NAHUALA, Mam! 3360 kHz R. "TEZULUTLAN" Actually, the Mam Indians are the Mayan Connection, but it does send CORAN 4835k Hz the inspiration for the name of station out a dandy QSL card depicting the LA VOZ DE ATITLAN TBMN, a 1,000 -watter SANTIAGO ATITLAN GUATEMALA CITY that is a relative national symbol of Mayaland: the 2,390 kHz TONA, 3300 8 5955 kHz newcomer to the airwaves, making its Quetzel bird. The Quetzel bird, which R. NACIONAL 6180 kHz debut on Jan. 11, 1975. Gladys Maria sports a long (as in 1- o -n -g!) green tail Landia, the director, says Cabrican is feather, romps around in the deep re- the station schedule. Try at 1100 GMT, "a pretty town about 10,000 feet above cesses of Guatemala's jungles. It cannot when the "Country Dawn" program sea level." You can usually hear this live in a cage and usually dies within features regional music and "saludos " - station catering to these direct descend- a day in captivity. The freedom -loving which are "hello's" to listeners. At 1200 ents of the Mayas, broadcasting in the descendents of the Mayas so admired GMT, it's time for the general cultural unique Mam language, around 0000- the creature that their unit of currency program, "School For All." Of course, 0200 GMT sign -off time on 4825 kHz. is called a "quetzal." It's worth about it's in Spanish. The transmitter is a good And you have to know that any station a buck. of American-built Collins. with a slogan of "Love, Peace and Far in the east of the country, near Radio Miramundo, La Voz del Ejer- Justice" is going to give DXers their Honduras and the Caribbean coast, are cito (The Voice of the Army), located due ... and they do! QSLs are quick two unusual stations: Radio Chortis in Zacapa, is one station that's created coming in, usually with a lovely lime - and Radio Miramundo. quite a stir among US DXers. Up to on -white pennant. Radio Chortis, TGCH, a 1,000 -watter recently, no one was even sure it really It's Coffee Time! The capital city of entering its twelfth year on 3380 kHz was a shortwave station. But Mira - the "Department" (like a state) of Alta in the 90 meter bands is frequently mundo slipped out from underneath a Verapaz is Coban, a rich coffee- produc- heard "like a local" stateside. Affiliated big bopper of a Colombian station and ing district. The residents of Coban with Radio Schools of Jocotan, the vil- now is heard nearly daily with a hotshot most likely enjoy their evening mug of lage location, the station teaches Indians marimba program around 1215 sign -on brew while catching the news and ma- such tricks as mixing and molding a time on 61581/2 kHz. Good news, too, rimba offerings of Radio "Tezulutlan" good adobe brick along with the usual is that QSLs are starting to come in. on 4835 kHz. Try TGTZ with your spelling and history. For a good recep- Try hearing Hugo Echeverria's show, morning coffee, though, because it's tion report, Padre Juan, the boss, may "The Miramundo Festival." Drop him best around 1200 GMT.'The slogan is send you the fascinating local maga- a line, too, if you do! "Culture and Education," and in case zine of Radio Chortis, which contains (Continued on page 86)

The Mayans ruled their part of the world or many years, and they Many of the present day inhabitants of the region live a simple, built an impressive civilization, awesome ruins of which remain. peaceful life reminiscent of the long ago, Imperial ancestors.

ELEMENTARY ELECTRONICS /March -April 1979 41 UPGRADIMINE 116-110

ÇQç;:your Convert IRS-80Radio computer 11 to full Leust $99 specs for l

CIRCLE 32 ON READER SERVICE COUPON was delivered for so little. For only IT'S SAFE TO SAY that the Radio TRS -80 Level I system there is no need you got a computer with a TV Shack TRS -80 with Level II BASIC is to change. Last year when we first re- $599 and a cassette bulk -data twice the computer it was with the old viewed this computer we were, like terminal recorder. Level I BASIC, and when this fact be- everyone else, impressed by how much storage the surface the TRS -80 appeared came apparent to the early purchasers On be a formidable computer value, but, of the TRS -80, which was then avail- to we were to discover and point out in able with Level I only, some were pretty as the Level I BASIC was burned up that their machine was re- our review, limited in terms of effective duced to second -class status after only sharply use for hobbyists and students above a few months. It is rumored that some level. Among other owners were making voodoo dolls the grade- school Level I version of BASIC like Radio Shack Level II ROM things, the shaped variables, and lacks and pinning them so that one has only two string chips package" which input line was open. the "transcendental provides trignometric and math func- Add On Level II. To Radio Shack's for effective use by stu- credit, however, such drastic steps are tions required junior and senior high school, no longer needed. For $99 (the differ- dents in and college. ence in cost between Level I and Level the computer board the On the flip side of Boosting the BASIC. Level II BASIC, II computers) you can have your Level connector plugs into one of the free ribbon came along later, corrected all I TRS -80 factory modified to full Level original ROM sockets. A jumper, resistor which inherent in Level I. Essen- II specifications. Radio Shack does, all installation, and a cut foil complete the the defects 12K Microsoft Extended the work for you. Level Il conversion. It couldn't be easier, tially, it is the without major modifica- which is one of the most pow- Of course, if you, like thousands of yet it works, and BASIC, to the original computer. available to hobbyists. others, are perfectly happy with the tions erful BASICs You name it, and it's probably in Level II. Even named files are included - which is the next best thing to a disc system, along with specific error codes (23 of them), program trace, and well, there's little that's not there. 12K provides a lot of room for "extension," and Radio Shack has packed it with everything, even an edit mode that allows you to correct bits and pieces of programs. For example, you can correct parts of a multiple statement line without retyping the entire line. Finally, the Level II speeds up data the module over the The 12K module has adhesive strips on the bottom. You position handling. The Level I BASIC cassette the module is secured to the edge of the main computer board and press down; voila, baud rate was only 250. The Level II computer. The ribbon connector plugs into the empty right hand socket, as shown. Four board. (Continued on page 95) wires from the module are tack- soldered to foils on the computer printed circuit

ELEMENTARY ELECTRONICS /March -April 1979 42 We all know how annoying TV corn - mercials '(and some programs) can be. Some times you would love to be able to flick off their loud, abrasive chatter until the show comes. back on, but you are watching TV to relax not REMOTE to jump up and down every ten minutes. With this simple remote control unit you can turn the sound on and off with the blink of a flash light. All you do is aim a flashlight at a CONTROL small box sitting on top of the TV. When the unit receives the first flash of light the sound is turned off Kill your TV's sound with the indicator light comes on (verifying blink of a flashlight your signal) . When you want the sound back another flash of the light and the sound is restored. There are a number of good reasons for using a flashlight as the transmitter. First, of course, it is simple and inexpensive. Also it allows the receiver to be simple, and hence easy to build and

troubleshoot. Naturally this system . requires the operator to have a free line -of -sight to the TV, but a viewer always. has that. Further the unit responds to any number of flashlights. How It Works. The circuit operates as follows. The signal light is received by a phototransistor (P1) recessed behind the front panel. A photo -transistor is a transistor where the base signal is effectively provided by a light source, the brighter the light the more it turns on. In this circuit, the photo - transistor is used as one leg of a voltage divider. When the light strikes P1 the voltage across it drops. This "fall- by Christopher Kilian ing edge" is amplified by Q1 and then used to trigger the monostable multi - vibrator (ICI ). trol transistor Q2. When IC2 goes This device (ICI ) is often called a high, the transistor turns on providing "one shot" because it outputs one pulse a path for the relay coil current to of uniform width each time the input ground, thus energizing the relay. goes high or low (depending on how Note the diode D3 across the relay it's connected up). The length of this coil. This is necessary as it provides a pulse is set by C2 and R5, in this case safe path for the built -up energy in the about .5 sec. The "one shot" here is coil to dissipate when the relay is de- acting as a buffer, taking the rough energized. Without the diode high volt- signal from the flashlight and convert- age spikes occur which quite probably ing it into a nice, clean, clock pulse for would cause false triggering in other the flip -flop (IC2). parts of the circuit. The relay performs Install a (light shield over the photo- transis- The flip -flop is used here as a mem -. two functions. first The set of contacts tor so that the unit will not be triggered ory to keep by track of whether the TV (normally closed) controls the sound anything other than the flashlight beam. is sound on or off. One property of by opening the TV speaker circuit. The Installing the project inside a light proof the J -K flip -flop is that if both J and K other set of contacts (normally open) case with only a small hole in front of the inputs are held high (5v), the output controls the indicator light which is photo -transistor will make the unit even will "toggle" with each clock pulse. powered by the 12.6 VAC from the more effective. With a little bit of imagina- In other words if the output is low, it transformer. The function of this light tion this controller could be adapted to will go high with the first clock pulse is more- important than you might almost any device you can think of and then low again with the next clock think as it gives the operator a positive etc. This is just the kind of action we indication of what state the unit is in. ment transformer. The 12.6 VAC is need. When the output of IC2 goes (It's not always obvious from program rectified by a full -wave rectifier using high it will turn the sound off and hold material.) the center tap with D1 and D2, then it off until it gets another clock pulse. The power supply is simple and smoothed by Cl. This unregulated To accomplish this the output of the straightforward. The 110 VAC is run voltage is adequate for the relay coil, flip -flop is used to drive the relay con- thru a power switch into a 12.6 fila- but not for the ICs, so the 6 -V zener

ELEMENTARY ELECTRONICS /March -April 1979 43 1 0 REMOTE CONTROLLER S is employed to provide a regulated 6 -V for these components. Construction. Probably the easiest way to construct the circuit is on a 4% -in. by 6 -in. perforated circuit board FROM AUDIO using push -in terminals for connection AMP points. Start by laying in the transformer, relay and IC sockets. If you use a board with 0.1 in. centers the IC socket pins should stick right through and can be secured with two small screws. Mounting the transformer and relay will, of course, require enlarging some holes. Next, the push -in terminals may be inserted .and the components soldered into place. Note that the phototransistor is mounted directly on top of Q1, facing the front. It should be as far above Q1 as it's leads will Need parts' allow. For a professional looking job PARTS LIST FOR REMOTE CONTROLLER Hobby Mart, page 89. turn the board over and solder the in- C1- 500-uF, 35 -volt electrolytic capacitor or equiv.) terconnecting wires on the backplane. C2- 10 -uF, 35 -volt electrolytic capacitor R1-82 -ohm, 112-watt, 10% resistor The circuit can now be mounted in D1, D2, D3- 1N4003 diode R2- 10,000, 1/4-watt, 10% resistor a case using stand -offs. Mount the D4- 1N4735, 6.2 -volt zener diode R3- 50,000 -ohm, potentiometer power switch, potentiometer, and in- IC1 -74121 monostable multivibrator R4- 2,7000 -ohm, 1/4-watt, 10% resistor IC2 -7476 dual JK master /slave flip-flop R5- 56,000 -ohm, 1/4-watt, 10% resistor dicator on the front panel. Cut a one - 274- R6- 330 -ohm, 1/4 -watt, 10% resistor directly in front of the pho- 11- closed circuit jack (Radio Shack inch hole or equiv.) S1 -SPST switch to allow the flashlight 292, totransistor K1 -12 -volt DPDT relay T1 -12.6 -volt center tap filament trans- to enclose beam in. Finally, it is best 11 -lamp assembly and 12 -volt bulb former the whole unit to keep ambient light P1- matching plug for jack J1 (Radio Shack Misc. -one 16 -pin and one 14 pin IC socket, from activating the circuit. 274 -289 or equiv.) 41/2-in. by 6 -in. perfboard, cabinet, nuts, Installation and Checkout. To com- al, Q2- 2N3904 transistor bolts, spacers, perfboard push -in termi- plete the system a simple modification Q3- phototransistor (Radio Shack 276-130 nals, sheet metal, knob, power cord, etc. to the TV is required. Unplug the set, the viewing remove the back cover, and locate the when the control unit is not plugged erate the flashlight from the pot. Find two wires going to the speaker. As in. But when it is plugged in the relay area while you adjust unit responds to shown in the schematic, cut one of the must be closed to complete the sound the point where the room lights wires and connect the two leads to a circuit. the flashlight but not to have phone jack, which you mount in the Once the system is operational, some etc. Now sit back, knowing you over Madison side of the case. When the jack is cor- adjustment of the senstivity potentio- at least some power rectly wired the sound will be normal meter is necessary Have someone op- Avenue.

perfboard construction make this proj- This top view of the circuit board shows how the photo transistor Point to point wiring and a snap to put together. Take care hooking up the relay. is mounted directly on transistor Ql's base and emitter leads. ect

ELECTRONICS /March -April 1979 44 ELEMENTARY CIRCLE 74 ON READER SEPVICE COUPON

This ultrasonic servant turns appliances off and on at your whim Universal Whistle$wìtch

JUST GIVE A WHISTLE . . . and posite side is a relay -controlled AC of ultrasound causes the outlet to your cassette deck will start or stop, outlet. When the receiver senses the "flip." your video cassette recorder (VCR) ultrasound signal from the whistler it Range. The system has a working will pause for commercials, or your applies power to the outlet. Another range of up to 30 feet, the exact value photo studio modeling and work lights burst of ultrasound removes power depending on the surrounding furnish- will turn on and off. Fact is, just about from the outlet. Each subsequent burst ings. A sensitivity control on the bot- anything you can control with a switch tom of the box allows the device to be can also be controlled without ever adjusted for the minimum signal from leaving your chair by simply giving a the whistler that will trip the relay, whistle, or to be more precise, an ' °ul- thereby reducing the possibility of false trasonic whistle." Your only problem tripping by random noise. will be to decide whether you need to If all you need to do is control AC control 120 VAC. or some other volt- power, such as turning a TV or lamp age or signal source. on and off, the system as supplied is The device that makes it all possible all that's needed. However, if you need is the "Whistleswitch," made by Uni- to control a low voltage circuit, such as versal Controls Corp., and sold by a VCR's pause, or a reel -to -reel re- many parts distributors and hobbyist corder's remote start, or an audio cir- suppliers. cuit, the AC outlet is of no use unless The "Whistleswitch" really consists you want to use an external control of two assemblies: a receiver and relay. However, since the AC outlet is transmitter. The transmitter, or "whis- controlled by an internal relay in the tler," is simply a dog whistle mounted receiver, a few simple modifications are in a small squeeze bag made of plas- all that's needed to provide an ordinary tic, much like the air control device set of switching contacts, making the used by photographers for remote con- device a universal whistle switch. trol of camera shutters. Squeeze the Modification. The first step is to open whistler and air is forced through the the box, whose cover is cemented rather whistle, producing an ultrasonic sound than secured with screws. Simply force which barely is discernable by the user. the tip of a pocket knife against the ce- The ultrasound is picked up by the The foil on both sides of relay terminal. mented joint between the front and receiver, a small plastic box measuring number 5 must be cut away. Although the back of the receiver and draw the 2 % -in. 17g by 43i-in. by -in. On one side job can be done with a knife or an ice knife around the four sides. Don't of the box are terminals that plug pick, a neater cut is done by using a ro- press too hard or the blade might slip directly into an AC outlet. On the op- tary grinder bit in a small; hand -held drill. into your thumb. Repeat the draw until

ELEMENTARY ELECTRONICS /March -April 1979 45 Here, the new control jack is shown installed in place of the original AC outlet. EgAg WHISTLE SWITCH We strongly suggest the use of a miniature jack, as clearance under the cover is severely limited. Use a thin flexible you have cut through the joint. Care- wire to connect the jack to the PC board. fully remove the cover, taking care not to damage the sensitivity control, whose most instantly welds the two pieces by shaft, which cannot be removed, ex- dissolving some plastic from both sec- tends through the cabinet. tions of the box. In a few seconds the Using diagonal or side cutters, clip solvent evaporates, leaving the sec- both wires running to the AC tions permanently "welded" together. receptacle at the printed circuit Using The Whistle Switch. Install cutters, clip both wires running to the the receiver on an AC outlet near the AC receptacle at the printed circuit equipment to be controlled and con- board. Next, locate the relay, which is nect a control cord from the receiver's in a small plastic housing on the PC jack to the equipment. You will prob- board. If you flip the board over, ably have to make up a patch cord you'll find that directly below the re- with the correct connectors. Since the lay is the printed circuit wiring shown whistle switch requires insignificant in the diagram. The relay has five ter- power it can be left plugged in at all minals (the numbering shown is ours), times. with a foil connection between ter- When first plugged in, the whistle minals 4 and 5 which extends on to switch's control contacts are open. The other circuits. This is the only impor- first "whistle" closes the contacts. Aim tant foil; forget about all others. the whistler at the receiver and squeeze. Using a knife or rotary grinder, cut If the relay fails to trip, advance the through the foil on both sides of ter- receiver's sensitivity control, always minal 5, as indicated by the arrows using the minimum amount of sensi- marked CUT. When you're finished, tivity required for reliable operation. floors terminal 5 should have no connection. Unless the room has uncovered prob- It is the wiper contact for the relay. and ceilings, the whistler's signal Terminals 2 and 3 are the stationary ably won't bounce or reflect around contacts. Set the assembly aside for objects, so try not to conceal the re- the moment. ceiver behind the controlled equipment. Using a drill or other suitable tool, Keep in mind the system will be cer- remove the AC outlet from the cover tain to work if there is nothing between and replace the outlet with a plastic or the whistler and the receiver. Bakelite strip. Secure any type of "control'' jack to the strip before installing the strip in the cover. (A small section of ordinary perf -board will be fine.) There isn't too much room behind the strip because the AC ' plug terminals share the same space, so a small jack such as the phono type, or mini -jack used on portable recorders, is recommended. Solder short lengths of #20 or #22 insulated stranded wire to relay PC board terminals 3 and 5, and to the control jack. Polarity is not important because all relay terminals are now isolated. Finally, reassemble the box. Press the front and rear sections together, draw a bead of fast -drying plastic cement around the joint, and hold the parts together until the cement sets. Perhaps the fastest method of assembly is to feed some plastic solvent, such as that supplied in the "G. C. Plastic Repair Kit," around the joint. The "welds" the plastic to- solvent actually The finished cuts around terminal number 5 are shown here, with the new leads to the this is gether in seconds. The way to do control jack soldered into position. Use a magnifying glass to be certain that you have to fill a needle injector with a small removed all of the copper foil, and that no fragments remain on the board which might amount of solvent and inject a drop or cause a short circuit. Allow for sufficient length in the wiring from the printed cir- two into the joint. The solvent runs the cuit board to the control jack, so that when the cover is closed, no strain will be length of one side of the joint and al- placed on new connections. The WhistleSwitch is ready for duty, at your command.

-April 1979 46 ELEMENTARY ELECTRONICS /March 5 4u' ,t h e

Regend Flight Scunner Fasten your seatbelt and you'll be clear for takeoff into a new realm of radio listening

WHILE A VHF -UHF SCANNER puts then let's you program them into a A bank of 16 LEDs (light emitting you where the action is, it doesn't give channel. diodes) indicates whether a channel is you all the action. Specifically, it leaves Tower Finder. The Regency ACT -T- on or off. The diodes used as channel out the 108 -138 MHz, amplitude modu- 720A Digital Flight Scan is just such 1 and channel 2 indicators also serve lated, aircraft band. If you want to an aircraft band scanner. Using an on- as the programming indicators for the hear what's going on at the local air- board microprocessor -in reality a small search: when the channel 1 indicator is ports, or ride along in the cockpit of computer -the ACT- T -720A can actu- lit the lower search limit is entered; an airliner, you'll need a scanner spe- ally search a user-selected range of fre- when the channel 2 indicator is lit the cifically designed for these frequencies quencies between 108 and 136 MHz, upper search limit is entered. Search and AM modulation. and then program any of the "dis- limit programming, however, does not While there are many crystal con- covered" frequencies into one of 16 affect the frequencies programmed into trolled aircraft scanners available, find- channels. Of course, if you know the channels 1 and 2. A 17th LED is used to ing the right frequencies and crystals local aircraft frequencies you can pro - indicate scanner is in the search mode. for your area can prove expensive un- gram them in directly without search- Three "keyboards" determine the less you know someone at the airport ing them out. specific type of operation. The key- who can give you a list of the air and Because the scanner is digitally pro- boards are similar to those found on ground frequencies. A much easier way grammed there is never a need to pur- electronic scales used by food stores. to get on the aircraft band is with a chase crystals as you discover new fre- The keyboard itself is a flexible plastic programmable scanner, one that quencies or move from area to area. To sheet with alphanumeric symbols. Be- searches out the frequencies in use and change frequency you simply punch (Continued on page 87) the new one in through a keyboard (more on this later). The Digital Flight Scan has 16 programmable channels, a battery maintained non -volatile memory (in the event of power failure you don't lose programming), a volume control, squelch control, and a seven -digit LED display used to indicate the frequency programmed into a channel, the fre- The rear apron has sockets for the AC and quency scheduled to be programmed The L.E.D. frequency readout indicates the DC power cords, and jacks for a remote into a channel, d (delay before resum- channel or received (searched) frequency. speaker and the antenna. The supplied tele- ing ,scan), and L (channel locked out The letter "P" following the frequency indi- scopic whip antenna plugs directly into the cates it is one of two -programmed of scan). In addition, there is a search user antenna jack as shown; it is simply un- priority channels. An "1" following the fre- mode that scans between user- selected plugged if you want to use an outdoor an- quency indicates the user has locked that frequency limits, tenna. The 9 -volt battery for the channel stopping on active channel out of the SCAN, though it can be memory protection slides into a small com- frequencies and indicating the frequen- manually selected. A letter "d" following partment that is normally protected by a cy on the LED display. The frequency the frequency indicates that a 2- second de- metal plate; we have removed the plate so can be logged or instantly programmed lay has been programmed before scanning you can see how the battery slides. into one of the channels. resumes after the station carrier goes off. 1

ELEMENTARY ELECTRONICS /March -April 1979 49 DXing at the Speed of Sound by Harry Helms Jr.

Tune in on the high -flying excitement of aircraft radio

group of five VOLMET AMOVING TARGET may be harder to nautical stations to hear are known as route." Another hit, but not for DX, even when the VOLMET stations. These stations stations serve the Pacific area route. at 1200 miles transmit weather information to air- Our chart shows the times and fre- the target is moving VOLMET per hour at an altitude of 29,000 feet! craft operating on various international quencies that easily -heard is of- SWLs can "reach for the sky" by tun- routes. One of the best -heard stations stations use. Station identification the city where ing in the international aeronautical is operated from New York's Kennedy ten simply the name of frequencies, receiving many fine catch- International Airport, giving weather the VOLMET-is locaed, such as "New Both air- York Radio" or "Gander Aeradio." es and QSLs for their efforts. VOLMET craft aloft and airports can be tuned Major Aeronautical Bands There are many other sta- are in, with transmissions ranging from All Frequencies in kiloHertz tions around the world, and most routine weather broadcasts all the way very good verifiers of DX reports. Lists 2144 -2170 10005 -10100 of VOLMET stations, along with their up to top- secret, coded instructions for 11175 -11400 2850 -3155 be found in the nuclear bombers of the Strategic Air 3400-3500 13200 -13360 addresses, can Command! 4650-4750 15010 -15100 SPEEDX Utility Guide, available from While over land, most air traffic is 5480-5730 17900 -18030 SPEEDX, P.O. Box E, Elsinore, Cali- aero- 6525 -6765 21850- 2200(1 fornia, 92330. confined to the 108 -136 MHz VOLMET nautical band. However, this band has 8815 -9040 23200 -23350 Old Sod DX. One foreign that should be of particular interest to limited range and is not useful when bands. The above list is of the major aero North American SWLs is "Shannon aircraft must travel far away from land from frequency to fre- Pilots will switch Aeradio," located at Shannon Airport (such as on trans -oceanic flights) or quency according to propogation and need. is the only where aircraft are frequently operating in Ireland. This VOLMET to log and far away from their home base (such information for cities located in the chance most DXers have Tune for it on as in the military). For such situations, eastern half of the United States. Trans- verify this rare country! If certain frequency ranges have been set missions last for twenty minutes, begin- 8833 kHz from 2200 -0700 GMT. send your report aside in the shortwave spectrum to ning on the hour and half -hour. Dur- you hear it, you can communications to and from ing the twenty minutes of each hour to Shannon Aeradio -EIP, Ballygirrein, handle Clare, aircraft. Our chart gives these frequen- that this station is silent, another Newmarket -on- Fergus, County cy ranges. Almost all air traffic today VOLMET station located at Gander, Ireland. Flights. Commercial air - is in the single sideband (SSB) mode, Newfoundland is on the air on the Commercial along international usually upper sideband, although aero- same frequencies giving weather infor- linèrs traveling using several nautical weather transmissions are still mation for various Canadian cities. To- routes keep in touch by Frequencies used largely in the AM mode. gether, New York and Gander serve assigned frequencies. the airliner is Aviation Weather. The simplest aero- what is known as the "Atlantic area depend on which route

ELEMENTARY ELECTRONICS /March -April 1979 50 taking. Flights in the Caribbean area use 8959 kHz for example, while those in the Far East use 8868 kHz. Trans- missions are in the upper sideband (USB) mode and you'll find English If you live along the Atlantic, Gulf Pa- to be the most widely used language or cific coasts you might on international flights. chance to tune in Airplanes will identify by the name some naval air action of the airline and the flight number, such as this McDon- such as "Air France 102" while air- nald Douglas A -4E ports will simply use the name of their Skyhawk close -sup- city, such as "Miami." However, all port and attack plane. British Airways (formerly BOAC) Watch your newspa- flights are identified as "Speedbird." pers for reports of Similar, all Lufthansa aircraft identify training exercises. themselves as "Bluebird." Our chart will show you where to tune to hear commercial air traffic. Of particular interest to East Coast listeners should be 11367 and 13328 kHz, which are often used by the supersonic Concorde. Most commercial aeronau- Commercial Airliner Channels and Routes tical stations will QSL, although a freq. prepared card is usually necessary. kHz Routes: Transmissions 5589 North Pacific This chart shows the from airports can be re- frequencies commonly ported to the Communications 5610 North Atlantic Officer - 5638 used on various inter- in- Pacific and Atlantic Charge of the airport heard; trans- 5673 Atlantic, Caribbean, Southeast Asia national air routes. Lis- mission from airplanes can be reported 6540 Caribbean (very busy channel ) ten up for the Con- to the Flight Communications Manager 8868 Far East corde (the plane shown of the airline operating the aircraft 8889 North and South Atlantic at the beginning of heard. 8931 North Pacific this article) on the fre- Uncle Sam's Planes. The United 8959 Caribbean quencies indicated.The States Air Force maintains perhaps the 10049 South Atlantic British Airways flights most extensive and sophisticated air 11343 Caribbean identify as 'Speedbird.' communications system in existence. 11367 North Atlantic (used by the Concorde.) Some of the most fascinating listening 13205 Soviet flights to Cuba 13288 Central Atlantic available to the SWL can be found 13328 North and South Atlantic (Concorde channel) here. 13344 South Atlantic Our chart lists some of the more commonly heard frequencies used by various Air Force bases. All transmis- Panama Canal Zone and Alaska! Most ever, stations of the Strategic Air Com- sions are in USB and are identified by Air Force bases will verify correct re- mand (SAC) often use tactical call the name of the air base. DX'ers should ports by QSL card, and you can send signs to disguise the location of their pay particular attention to the frequen- your reports to the Chief Radio Officer ground stations and planes aloft. These cies used by Albrook Air Force Base at each air base. tactical calls are changed frequently, (AFB) and Elemendorf AFB, as these Ordinary Air Force flights will iden- but among those used in the past have two targets are among the easiest ways tify themselves simply by aircraft num- been "Bagman," "Aerosol," "Dog - to hear and verify, respectively, the bers, such as "Air Force 27856." How- (Continued on page 86)

While it's doubtful you'll ever catch a U -2 Strategic Air Command Frequencies spyplane like the one shown here, you might DX these Air Force bases, and S.A.C. 4725, 6761, 9027, 15041 kHz intercontinental bomber frequencies.

freq. kHz Base and Location 8995 Albrook AFB, Panama Canal Zone 6727 Scott AFB, Illinois 9017 Andrews AFB, Maryland 6738 Elmendorf AFB, Alaska 9023 Scott AFB. Illinois 6750 MacDill AFB, Florida 11176 Albrook AFB. Panama Canal Zone 8964 Hickam AFB, Hawaii 13201 Andrews AFB, Maryland 8967 Andrews AFB, Maryland 13201 McClellan AFB, California 8989 McClellan AFB, California 13244 Loring AFB, Maine 8989 Elmendorf AFB, Alaska 15015 Loring AFB, Maine

ELEMENTARY ELECTRONICS /March -April 1979 51 e% installs the... VIGILITE ELECTRONIC HOME

CIRCLE 70 ON READER SECURITY SERVICE COUPON

Microprocessor timer gives your home TIMER that lived in look while you're away

VIGILITE IS A NEW microprocessor - server on the outside thinks people are How it Works. Before discussing the based, pre -programmed light control moving about in the house. Since there very simple installation procedure, let's unit that permits unusually efficient au- is no installation cost (you can install see exactly how this ingenious inven- tomatic control of home lighting to the Vigilites yourself), the total cost of tion works. First you press and hold make would -be intruders think your your lighting security system is calcu- down a "Time" switch. After one sec- unoccupied home is inhabited. It does lated by multiplying the unit cost of ond, the digital readout will count min- away with all those plug -in clocks that $39.95 by the number of locations you utes from 1 to 60. Continue pressing clutter tables and floors, and that re- wish to control. until the minute is on the correct num- quire dangling power cords that your Note that a Vigilite can control built - ber, then release the "Time" switch. do, or cat runs into constantly, or that in overhead lights, as well as table Next repeat the same procedure to set your two -year -old uses as a teething lamps plugged into a switch -controlled hours. Note that P.M. time is indicated device. Vigilite (made by Hutec Corp. wall receptacle, which is something by two lighted dots that appear be- in California) installs neatly and per- that a conventional clock control can- tween the hours and minutes displays. manently as a replacement for any not do. Just understand that the device You have now quickly and easily set conventional single -pole wall switch. must not be used to control such things the clock to indicate the correct time When automatic lighting control is as a TV set, appliances, or any other of day or night. not required, the unit functions exactly motor -driven equipment. To select the desired automatic on/ like a normal on /off switch, except that off switching pattern, push and hold it also constantly shows the correct down the "Room" button until the dis- time of day by means of a digital read- play indicates symbolically the room - out. When you intend to leave your pattern of your choice. For example, home unoccupied, simply press a when symbol "F" appears, release the "room" button to activate the auto- "Room" button if you want the fam- matic timing system. The unit will then ily /living room program. When this is turn any 40- to 300 -watt lighting fix- done, the correct time of day again're- ture on the circuit on and off accord- appears on the digital display. ing to a pre -programmed schedule. Activation of the program- selected Five Patterns. Five different timing mode is done by depressing the "Room" patterns are factory pre- program- button for less than 1 second. Pressing med into each Vigilite (see chart) to longer would start changing the pro- simulate typical use of lights in key gramming again. After this fraction -of- home locations, a bedroom, outside, a- second activation procedure, the digi- kitchen and family /living room. You tal display alternately shows the correct can quickly and easily select the ap- time and the selected room pattern propriate timing sequence by means of symbol. To deactivate the system, sim- a pushbutton. Obviously, for maxi- After cutting off power at the fuse box, reply once again press the "Room" but- mum protection, you need two or more move the light switch and install Vigilite in ton for less than 1 second. Vigilites in your home so that an ob- its place. The whole job takes five minutes. (Continued on page 88)

ELECTRONICS -April 1979 52 ELEMENTARY /March by James A. Fred Troubleshooting Antique Circuits

U MANY ANTIQUE RADIO collectors are ple that the only test instrument need- and a signal generator. Since trouble- older men who started radio repairing ed to troubleshoot most radios was a shooting of solid state devices is usu- in the 1920's. They remember the mag- volt- ohmmeter. Of course it would be ally done with an oscilloscope, the netic speakers, WD -11 tubes, TRF and helpful to have a simple tube tester modern technician may not have sim- Neutrodyne receivers, catwhiskers, etc. capable of testing the real old tubes, ple test equipment or know where to But what about the younger collectors buy it. It is fine to own and use a who were trained on transistors, diodes, digital VTVM, an oscilloscope, and a phase -locked loops, emitters, collectors, function generator, but look at the fun etc? 1 hear from this group of collec- he is missing by not troubleshooting his tors, who are usually between 20 and 192O's radio with 1920's test equip- 35 years old, quite often. Many have ment. taken up collecting so they will have a Since we have already discussed an hobby to turn to at home. They tell me ohmmeter and the voltmeter, we will that it is very satisfying to restore a tell you how to trouble shoot a 1924, 3 1920's radio with its superior hand- dial, TRF radio receiver. To trouble- made construction, large, easy -to -see shoot this set, the only instrument you and repair components, and fine wood- will need to perform all the necessary en cabinets. There is nothing to com- tests, is an ohmmeter, unless the set still pare with the thrill of turning on the doesn't play after you have resistance power and tuning in a station on a checked it and turned it on. If it still set you have brought to life with your Using special batteries for old radios is doesn't play, you will need the volt- expensive. I use this own hands. special power supply meter and perhaps a tube tester. which is Simplicity. The old sets were so sim- described in detail in the text. Troubleshooting. To start trouble-

AUDIO AUDIO TRANSFORMER TRANSFORMER

RF AMP RF AMP 1st AUDIO goon 201A 800.11 201A CI DETECTOR AUDIO AMP OUTPUT 201A 201A 2014 P G P G C i i RI SPEAKER B+ F J+1 "02 1 o B+ 90 VDC

1 1 A+ 6 VDC

R2 R3 R4 o C C3 -4.5VDC OFF -ON

B+

CI GRID CAPACITOR R4 FIXED FILAMENT RESISTOR RI GRID LEAK RESISTOR C2 PHONE CAPACITOR o C+ 67.5VDC R2 RF AMPLIFIER RHEOSTAT C3 FIXED CAPACITOR R3 DET. CONTROL RHEOSTAT o B- This TRF receiver from the mid '20s shows the wide variety of voltages that are needed to operate the circuit. The triode tubes used predate the more familiar triode as they use the filament as the cathode. Troubleshooting these circuits is a snap with schematic.

ELEMENTARY ELECTRONICS March -April 1979 53 former will not operate properly, if at trouble seeing the filaments light in all. Repairing transformers is a diffi- 71 As, 112As, most 201As and 200As. VGANTIQUE RADIO cult task, with most needing to be The WD -11, WD-12, and WX -12 fila- rewound or replaced. Repairing and ments have to be viewed in total dark- rewinding will be the topic of a future ness to see them. If there are no lighted With shooting a dead set, remove the batter- article. filaments, turn the rheostat knobs. resis- ies or power supply so you have just The filament rheostats will measure the rheostat turned to minimum the radio standing alone. Pull the tubes, from 6 to 30 ohms. Grid leaks are tance the filaments should glow at their noting the location of each, in case you resistors too, but will vary in resistance brightest. If there is still no light in the have more than one tube of each type. from 100,000 ohms to 10 million tube, it will be necessary to measure the With the tubes removed, use the ohm- ohms. Most inexpensive volt- ohmme- filament voltage and trace the circuit meter to check the filaments for a con- ters will not measure the value of a all the way from the battery or power tinuous circuit. The three tube bases grid leak. Fixed capacitors (called con- supply through the connecting wires, or you will find, with the pin locations in- densers from 1920 to 1940) should cable, to the tube socket. There is the dicated, are illustrated. Before checking show an open circuit when measured possibility of a bad solder joint or cor: the WD -11, WX -12, or 864/VT24 tube with an ohmmeter. If they show any filaments, be sure your ohmmeter does resistance at all, they should be re- not apply more than 1.5 volts to the placed. Use only mica, ceramic, or tube filaments. Either open up your dipped mylar capacitors in the old bat- meter and visually check its battery tery radios. If the capacitors are sealed voltage, or use another voltmeter to into metal boxes or plastic containers, measure the voltage across the test (Philco has these) you can melt out Ux200A prods. The reason for this is because the tar and put new small capacitors Ux300A listed tubes only require 1.1 of the same value into the containers. UX201 A the above Ux301 A volts on their filaments and a voltage When they are remounted in the radio 112A higher than 1.5 could burn them out. chassis, no one will ever know that the 7I A fila- inside capacitors are new. If every 864 After you are sure that your tube wx -12 ments are OK, lay them aside until component passes the ohmmeter test, UX199 later. Take your ohmmeter and check you can now check the headphones or 30 all coils, (those connected to turning speaker. Old headphones and loud- condensers) rheostats, and audio trans- speakers will have from 2000 to 5000 You can use this guide to find out the pin former windings for continuity. The ohms of impedance. Do not use crystal locations of some of the popular old tubes. resistance of the tuning coils will be or dynamic earphones with these old very low, between 2 and 20 ohms. radios because they will not work prop- roded tube socket contacts. Be sure Visually check the tuning condensers erly, if at all, due to the impedance, your battery is good, or that your at this time to be sure that the movable mismatch. power supply is furnishing the correct plates do not touch the stationery plates Firing Up. Now you are ready to put voltages for the tubes you are using. as you turn the tuning knob. The pri- good tubes into the radio, connect up With the filaments lighted, you mary of the audio transformer will the headphones or speaker, power sup- should begin to hear noise in the head- measure around 1000 ohms, while the ply or batteries, and antenna and phones or speaker. Touch the grid secondary will measure 5000 or more ground. Turn on the power and the leak or the grid terminal of the detec- ohms. If either of these windings are radio, and watch for the tube fila- tor tube and you should get a loud hum open (no resistance reading) the trans- ments to light. You will have no or howl. If you get a noise here, proceed with this paragraph. Otherwise, skip to the next paragraph. If your radio has 3 tuning condensers, find the one connected to the grid leak and touch the antenna lead to it. By turning the knob on that condenser, you should he able to hear a local radio station. If you get a station at this point, move back to the next condenser and try the lead here. If you do not hear the station with greater volume, you have trouble in this stage. If you do hear the station here, but not with the antenna wire on its binding post, then the problem is in the first stage. If you did not get a sound when you touched the grid or grid leak, your trouble is in the detector or audio amplifier stages. Go to the tube feeding the signal to the speaker and touch the grid with a metal screwdriver. You should hear a click or a hum. If you anything, check this stage radios with the filament connections don't hear This Metrodyne receiver is one of the first AC operated for trouble. If you do hear a noise. top ends of the tubes. In this photo you can see the filament harness running at the (Continued on page 84) across the tops of the tubes. The lack of batteries was a boon to radio sales.

ELEMENTARY ELECTRONICS/March-April 1979 54 IL

GETTING YOUR BNEE FOURTH SEMESTER

Now THAT YOUR STATION is as- Basic operating procedures- sembled, let's make a contact. To do this, we'll first talk about "why morse how to make a contact code ?" and then get into some operating procedures. In the meantime, get your rig warmed up! Thomas R. Sundstrom W2XQ The Morse Code. The code may seem senseless to bother with for you at first, but it is the most efficient use of radio deciphered. Examples include: your spectrum space there is, due to its small = UR; receiver RCVR; weather bandwidth. Once you build some speed = WX; antenna ANT; longwire and become somewhat relaxed when = LW; etc. One of the best lists of com- conversing with other stations, it is fun. mon abbreviations I've seen is in the The necessity to concentrate on the Radio Amateurs' DX Guide, published code forces you to forget about the by Radio Amateur Callbook, Inc. problems of the job or other worries Let's construct a QSO as an exam- and, in that way, it can be a welcome mean. Using an old 50-watt output ple. A QSO can be initiated by change. calling transmitter and an end -fed 135 -foot CQ, or replying to someone else call- Code is a great equalizer of amateur longwire antenna, I just collected a ing CQ. If you call CQ: radio stations. - Modest antennas, long WAC (Worked All Continents) Cer- CQ CQ CQ DE W2XQ W2XQ W2XQ wires, dipoles, and ground planes, and tificate on 40 meters CW. It can be K low power (less than 300 watts input) done. "Calling any station, from W2XQ, can and do work around the world. The QSO. Over the years, telegraphers go ahead." This is a 3 by 3 call (3 Virtually all of the European and Rus- and amateur radio operators have de- CQs and the call 3 times); in an in- sian stations that I've worked on all veloped a "shorthand" known as the active band, something up to a 10 by 3 bands are running 100 or 200 watts in- "Q" signals. An example of these is put. An exception is to find someone on. the QSO, short for two -way conversa- This is the last of our series Getting 10, 15 or 20 meters CW using a 3- tion. Your BNEE (Bachelor of Novicetry element beam. QSOs normally follow, a standard from ELEMENTARY ELECTRONICS). If you An example of how- not -to operate, format. Usually the first exchange con- want to go beyond this course then using high power and high -gain an- sists of: An RST report, the location of pick up a copy of our sister publica- tennas, to create a morass of bad oper- the station, and the first name, in that tion AMATEUR ating habits, rudeness, interference, and RADIO TODAY, available order. newsstands malfunctioning, splattering equipment on everywhere. It is jam - An RST report consists of three packed with information about ama- can be found on the bottom end of the numbers reporting on readability, teur radio and radio equipment. 20 meter SSB phone band (14,200 kHz strength, and tone of the received sig- and up). nal. If you get back anything less than 10 CQs) would be OK, but don't call It's a very pleasant change to move a T of 8 or 9, you should check your to the peace and quiet of the CW band. equipment. CQ 50 times, as I've heard some stations do, without signing a call or There's plenty of room, and even the Procedural signals and Q- signals pausing to listen for a reply. pileup of stateside operators chasing a that you are likely to encounter are W2XQ W2XQ DE WB2AYA rare foreign station is less chaotic. also detailed in many listings. Other WB2AYA K Once you upgrade, you'll see what I words are abbreviated, but are easily "W2XQ, from WB2AYA, go ahead." A 2 by 2 call should be sufficient unless the band is extremely crowded or With an automatic signals are weak. Once the contact is keyer such as this established, send the calls only once MFJ model, you can (since you know the call, there is no send a "CQ" or a need : pre- recorded mes- to repeat it) sage with just the WB2AYA DE W2XQ BT TNX FER touch of a button. CALL ES GM BT It makes operating UR RST 599 ES QTH WILLING - easier and a lot BORO, NJ BT NAME more interesting. TOM BT HW CPY? AR BK (or WB2AYA DE W2XQ) "WB2AYA from W2XQ ... thanks CIRCLE 69 ON READER SERVICE COUPON

ELEMENTARY ELECTRONICS /March -April 1979 55 Q= Signals & Procedural Signals IV I BNEE SEMESTER In transmitting and receiving morse code, GE -good evening a "shorthand" has been developed that GM -good morning is universally understood; the incomplete GN -good night for the call and good morning . . . list that follows covers almost all of the HI- laughter (in morse code) your signal report is: perfectly read- Q- signals and procedural signals that you K -go ahead (invitation to transmit) able with very strong strength and per- are likely to encounter. KN -go ahead to specific station (all others keep out) fect tone . . . my location is Willing- AR -end of message QRM -I have interference (from other boro, NJ . . . name is Tom . . . how AS -wait stations) on your signal do you copy? end of message ...... BK -break (interrupt transmission) QRN -I have atmospheric static on your break (or WB2AYA from W2XQ)." BT- separation between thoughts/ signal Actually, operators tend to repeat the sentences QSB -I have signal fading on your signal critical data, RST, QTH, and name, CQ- general call to any station that will QSO- two -way contact twice. You should not be sending any reply QRT -stop sending (closing down station) faster than you wish to receive. The CUL -see you later QSL -I will send a verification card DE QTH location is overslash ( -) means the letters are -from -my ... (if CQ DX is sent in one continuous motion. The DX- distant /rare station R- roger; all understood sent by a US or Canadian station, no SK- signing clear RST -QTH -name is a standard opening stateside station should answer) 73 -best wishes find abbreviated format; you may an GA -good afternoon 88-love and kisses version coming back to you. As it is not necessary to identify but every ten minutes, the use of BK speeds up the break." WB2AYA missed my name and heard some that were longer than the QSO. Unfortunately, not everyone rec- has quickly asked for a repeat. Don't original QSO. If you are shutting down ognizes it for the useful procedural waste motion and send something like: the station, send QRT after the second signal it is. Note that the "Q" signals WB2AYA DE W2XQ BT SRI QRM SK. are complete statements in themselves; ES MISSED UR NAME BT PSE One very useful procedural signal they can be turned into questions by SEND AGN TNX AR WB2AYA DE hasn't been mentioned yet. It means adding a question mark (or example, W2XQ K. What a waste of time! Sim- "wait ", while you answer the door or QTH? means "what is your location ? "). ply repeat your name, and then break the telephone, and can be sent anytime BK NAME? BK hack to him or her. (Continued on page 95)

. . . "break . . . your name is ? . . . R BK OK ES RIG HR IS "Roger (everything received) and the Addresses"` RST System rig here is .. ." Only send R if every- Manufacturers' was for complete under- thing copied Autek Research R= Readability standing. If you have to ask for a Box 5127B 1- unreadable "fill" on something missed, don't send 2- barely readable, occasional words Sherman Oaks, CA 91403 the R. To the QSO, you might distinguishable continue (active audio filter) 3- readable with considerable difficulty tell the other station about the weather 4- readable with practically no difficulty (WX ), your age, what you do for a Hy -Gain Electronics Corporation 5- perfectly readable living, how long you've been licensed, 8601 Northeast Highway Six etc., and conclude by asking a question Lincoln, NE 68505 S= Signal Strength (other than "how copy ? "). Conclude (antennas) 1 barely perceptable a QSO by sending something like: -faint signals, Gotham, Inc. 2 -very weak signals TNX FER FB QSO ES CUL BT 73 2051 N.W. 2nd Avenue 3 -weak signals SK WB2AYA DE W2XQ SK Miami, FL 33127 4 -fair signals . . thanks for a fine business QSO fairly good signals (antennas) 5- and see you again . . . best wishes 6-good signals signing clear . . . WB2AYA from 7- moderately strong signals ... MFJ Enterprises W2XQ . . . signing clear." Make the 8- strong signals P.O. Box 494 9- extremely strong signals closings reasonable in length; I've Mississippi State, MS 39762 (active audio filter(s) T =Tone Mini -Products, Inc. 1 Hz AC or less, very rough and -60 r CooNTT 1001 West 18th St. broad eALt urr,?nw Eire, PA 16502 2 -very rough AC, very harsh and broad MASS N "NO moat (antennas) 3 -rough AC tone, rectified but not AeNtlT7S CooNTY filtered *on Telex Communications, Inc. 4èJ a+w «NFLLA 4 -rough note, some trace of filtering vY JACpso, WMpy A,s io CN 9600 Aldrich Avenue South 5- filtered, rectified AC, but strongly Wt44y so+t,Fpk AtAj KAALALlU$,tA WH,,,A! Y(Pi`yAiW Minneapolis, MN 55420 ripple-modulated tGAlP " ... M MENT AMaSN/gF w}! 4. KEWEENAy,. (headphones) 6- filtered tone, definite trace of ripple y w LANE LOUP modulation ,ÿRCAET kV b6

ELECTRONICS /March -April 1979 56 ELEMENTARY King of the Hobbyists

Charles D. Tandy, the man who put a Radio Shack in almost every town and village by Lewis Kornfeld

practice, profits which could be imme- activity was to bring electronics parts diately redeployed into the creation of and equipment from the big cities and still more stores, and eventually, the the occasional town, right down to the setting up of factories, R &D facilities, grass roots and neighborhood level giant warehouses and transportation where surely -without the foresight, complexes. compulsion and daring of this one man A New Concept. He defied the con- -they might never have come. ventional wisdom of the consumer elec- Although the typical post -war electronics world of the early 1960s by de- tronics shop offered a range of 10,000 ciding to quit the mail order business to as many as 30,000 items, Radio at the very time when Radio Shack's Shack, in order to make its Tandy -size Charles D. Tandy larger competitors were secure in their expansion affordable, cut back to 2400 opinion that mail order was the best items. In Mr. Tandy's experience, 1918 -1978 way to sell electronics in quantity, par- gleaned from years of operating his ticularly its "parts and pieces" mer- Tandy Leather Company chain, 2400 chandise. His theory was deceptively was "just about the right number." WHEN CHARLES D. TANDY, founder simple: "We'll put a store everywhere While it might deprive the customer and boss of the corporation that mail orders originate, and then we'll see from being able to find exactly the de- bears his name, died on Novem- how many people will want to mail sired size, value and type of compo- ber 4, 1978, the electronics hobbyist their money into Chicago, New York nent, he would find enough to satisfy lost a fabulous friend -probably without and Boston ... and wait." his basic needs. even knowing of his existence, much In the 15 years during which he Dynamic Inventory. Additionally, the less his connection with the industry piloted Radio Shack from a $12- million sale of each part would be carefully and his enormous contribution to its weakling into a $1- billion colossus, he monitored, to allow for weeding out do- it- yourself fraternity. opened an average of over 470 stores slow movers and replacing them with Among the many paradoxes involv- and authorized dealers per year! Mid- more current and fast moving stock - ing this man's spectacular career, per- way in his efforts at placing a 'Shack' keeping units, thus maintaining Tandy's haps the most curious is that Charles in every corner of the United States, magic 2400 -item assortment, a number Tandy, having entered the business in he did the same thing in Canada. And known to be affordable and consistent 1963 by acquiring an elderly, failing to cap it all off, he decided to expand with his ambition to open pay- as -you- New England company called Radio abroad, setting up chains in Australia, grow stores in hitherto inconceivable Shack, knew absolutely nothing about England, Belgium, Holland, France, numbers. Needless to say, the hobby competi- electronics. What he did know, Germany, and Japan, adding 500 over- tion thought his tiny assortment laugh- perhaps better than any man who ever seas places where Radio Shack goods able. But Charles David Tandy, the in- lived, was the art of serving special - could be sold. At his death, the com- nocent newcomer from Texas, thought interest hobbyists via systems of small pany total stood at a staggering 7100 he "just might laugh all the way to the stores managed by highly motivated outlets, only nine of which were in bank." salespersons, and the art of making existence in 1963! In the beginning, he ran into prob- profits consistent with good business The net effect of this extraordinary lems he'd never encountered in the

When Charles D. Tandy took over Radio Shack in 1963 the stores The typical modern Radio Shack store is designed to meet the were typical electronics houses supply with tens of thousands of needs of electronics hobbyist with a well -planned inventory of items. Hardly a place for an electronics hobbyist to browse. components, not to mention a full line of consumer electronics.

ELEMENTARY ELECTRONICS /March -April 1979 57 and I don't mean tomorrow," as he so

I often told employees, with his own spe- KING OF THE HOBBYISTS cial brand of conviction laced with leather business- repairs and mail -order laughter and motivational hustle. returns. The latter he eliminated by the In Tandy's mind, the hobbyist was simple means of discontinuing all solici- the key ingredient in Radio Shack's tation of mail orders, terminating the program for success. His proudest many costly clerical systems associated achievements, aside from Radio Shack, with filling orders by mail, and handling were in building such other strong lei- lost orders and disgruntled customers. sure- related companies as Tandy Leath- The worst offender was the mail order er Company and Color -Tile, leading credit department where Radio Shack - divisions of what is now known as and later Allied Radio -were to meet Tandycrafts, Inc. Like Tandy Corpora- their Waterloo. "I pay cash, I'll sell for tion -which is now entirely an electron- cash," Tandy vowed, possibly echoing ics enterprise -Tandycrafts is listed on the sentiments of James Cash Penney, the New York Stock Exchange. one of his early idols and father of Do It Yourself. He reasoned that the J. C. Penney. person who did things with his hands Repairs, however, were another mat- was not only influential in his com- ter. Much to Mr. Tandy's surprise and munity but also was a likely candidate indignation, electronics merchandise did for buying finished equipment such as Lewis Kornfeld, is a longtime not always work or retain its original radios, tape recorders, audio systems, The author, friend and associate of Charles D. Tandy. There was nothing to and even costly and complex things like functional ability. He is also the president of Radio Shack. do but to face the music: buy or man- the company's famous TRS -80 com- ufacture more reliable goods, and set puter. "If I can make him happy at my the 2400 best sellers." Excuses, up yet another profit (or loss) center to parts counter, why should he go next ing only as concern with the several keep the goods sold and to satisfy the door for something already built and such their stores they were in the customer even if it meant "walking an finished ?" hundred new supplying, were dismissed extra mile." Radio Shack, in the USA Nothing made Charles Tandy angrier process of wave of his cigar -holder and . a alone, now has 55 strategically located (or more contemplative) than empty with a but jovial warning: "Just tell me service centers plus another 50 being hooks in the parts department. He spent stern not going to keep us 100 percent put on stream to handle its personal millions developing computerized re- you're in he'd roar, "and I'll do it my- microcomputer business. stocking and inventory control systems. stock," because I know how to get it done!" To his dying day, Tandy was never He poured over "out reports," querying self, It mattered little to him that he didn't too proud to personally answer his own merchandisers and inventory controllers an IC, an RF circuit, a telephone, handling complaints with as to why they could have even a sin- understand or even a DPDT switch. It was booming good nature and leaving the gle out-of -stock item "when, damnit, crystal, wasn't it? He under - offended customer absolutely certain I've made your life simple by eliminat- all merchandise, his problem would be solved "that day, ing thousands of slow movers and keep- (Continued on page 84)

UPER our 3 IV ''474.1 SPEW ycad

The first Radio Shack store (left) is contrasted to a modern store (above). There are now more than 7,000 stores worldwide, with many more opening every day of the year.

ELECTRONICS /March -April 1979 58 ELEMENTARY e/e checks out...

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You COULD RENAME this Mini - However, most of the time, your at- Micro Designer (MMD -1) computer tention is directed to the octal -style a "Designer's Dream Machine" or keyboard and to the row of 24 red in- "Student's Salvation ", depending on dicator lights that light or extinguish as whether you are a digital design engi- you tap in data or watch a program neer or a befuddled student still labor- run. ing to understand what really makes a INSTRUMENTS As you may already know, the octal computer tick. It may be hard to be- counting system has digits only from lieve, but this relatively low cost com- 0 through 7, which is why you see puter from E & L Instruments is at The key word is flexibilit only these eight numbers on the key- once a remarkably effective self- teach- for this miniature maree board. The H and L keys tell the coming aid, and a tool that any advanced puter when you are interested in either computer experimenter would soon the "Hi" or "Lo" half of a memory hold virtually indispensable. address (location); each memory loca- The MMD -1 was created not for tion is divided into two parts to facili- Star Trek and ping pong fanatics, but tate processing. The G key is for "Go" for experimenters. If you know little and is used to start a program running. or nothing about how computers really The S key is for both "See" and work, but want such understanding "Store" since it is used for the dual without plodding through endless tech- functions of depositing data into mem- nical jabberwocky, take a look at the ory and examining data already stored. MMD -1. If you want a computer that COMPUTER The Reset key, as the word implies, can lead you to automating a robot or resets the computer to the start of the running your household from a key- The first thing you notice about the program being run. The A, B and C board, take a look at MMD -1. If you MMD -1 is that most of the compo- keys are for optional applications and want a machine that can quickly test nents are out in plain sight, not buried need not concern us now. your electronic inventions, without the inside a plastic or metal box. Admit- The readout of the MMD -1 consists need to risk burning expensive ICs tedly this makes the components some- of 24 red LED (light- emitting diode) with a hot soldering iron, take a look what more vulnerable to damage if you indicator lights. The 24 LEDs are sep- at MMD -1. And if none of these sit- are careless; on the other hand, the vul- arated into three groups of eight, each uations apply, take a look anyway; the nerability makes you treat the machine group comprising a "port" with the left odds are that you'll think of more than more respectfully than you might oth- and middle ports used to indicate ad- one good reason to send for manufac- erwise. More importantly, you sense a dresses in the Hi and Lo memory lo- turer literature. psychological rapport with the machine cations and the right hand port used to Features. Before examining the that becomes stronger as your under- reveal data in memory. MMD -1 hardware, and the truly com- standing of the machine grows. You The eight LEDs in each port are plete line of supporting software, let's are able to put a finger on specific ICs sub-grouped into 2 -3 -3 patterns to pause for an overview of this 8080A- and say, "that's where it happens" or, make interpretation of their numerical based computer for training and hard- "that's where the programmed data is octal values easier. You might wonder ware development. now ". why the MMD -1 does not utilize more

ELEMENTARY ELECTRONICS /March -April 1979 59 boards. E & L Instruments sells a broad paper tape, that provides advanced de- variety of such outboards as optional bugging and editing procedures for a MINI MICRO DESIGNER equipment, both as kits and in factory - software developer. This program re- assembled form. quires the use of a Memory Interface familiar numeric readouts as do other Monitor Option. Most of the inte- Board (about which more later) and computers. Because, for an experi- grated circuit chips on the MMD -1 an ASCII device such as a teleprinter menter, the binary type readout is are installed in sockets, instead of be- or CRT terminal. faster and easier when there is a need ing hardwired to the circuitry, to make Incomparable Bugbooks. E & L's to know exactly what is happening replacement and alteration of chips Bugbooks V and VI are indispensable during programming and running. fast and easy without risking heat or guides to learning with the MMD -1. There is no need to convert a numeric static electricity damage caused by a Each volume contains almost 500 pages readout to binary to find out, for ex- soldering iron. of text written, not by electrical en- ample, what is happening to a particu- You should start your experimenta- gineers, but by professional educators lar low order bit because the answer is tion using the standard Keyboard Ex- who obviously not only understand right there before you. If all this is ecutive (KEX) PROM chip because computers, but also know what con- not entirely clear, be assured that it will the excellent training instructions con- fuses students and how to lead learners be before you get very far into the tained in Bugbooks V and VI relate to through difficult concepts in the most Bugbooks that explain how the MMD - this particular PROM. Later you may painless way possible. The texts provige detailed explana- 1 (and other microcomputer systems) wish to replace KEX with a KEX/ work. LD chip so that you can add a special tions of all compúter components and Operation. To run a program on the MONITOR PROM to an adjacent systems, from simple gates to complex MMD -1, just punch in the starting ad- socket. The Monitor enables you to interfacing circuits. Most chapters have dress (hitting the reset key usually run a program one step at a time, does this automatically) followed by rather than all at once in normal rapid the run key. Data is displayed in what- sequence, in order to check the regis- ever port you choose through program- ters (places where data is temporarily ming, and is evidenced by the LEDs, stored and manipulated) for proper through breadboard terminals, or contents. It's important to understand through any interfaced peripheral that running a program one step at a equipment you may have added. time is not the same as simply stepping The HALT light, a very convenient through a memory to check its con- feature, simply tells when the com- tents. You can do that much even with puter has encountered a halt statement the standard KEX. The Monitor en- in the program. It is extremely handy ables you to determine much more for debugging any program. Just insert quickly at what step your program has a halt instruction anywhere in the pro- gone off into the wild blue yonder in- gram, run the program and see if the stead of staying on track, hence "de- HALT light comes on. If it does, the bugging" a program is considerably computer made its way to that particu- simplified. The two operating manuals, one for basic lar part of the program. If it doesn't Incidentally, also available is a and one for expanded equipment, as well as light, your program has gone off into DBUG 1K program, in PROM or on the Bugbooks, are learning tools also. Gonzo Land during some earlier step. This highly desirable feature is lacking in many other training machines. .S --Sa.e IT -Ow .IT ENORE next to the 1/9 R B/W The built -in breadboard, mu IA./ -S TO SYSTEM I/E N PBOLE * keyboard, permits interfacing all kinds Ri Gin AIORS equipment to MMD -1 of peripheral MUMS ports without soldering. Just poke the bared ends of leads and components RIso,> 1:1IlCN Nn ;MING to discon- CPu into the breadboard holes; RISII ~- CnNIR.1 nect, pull out the wires. It's all very fast and easy. There's a connecting pin CONIROI BUS el OIREC, ION in front of each of the 24 indicator NEL. READ CONTR. on- DATA BUS l< "NIT SI-DINECTIDNRE D.T. Iwo .,,J WRITE r11EL BUTTERS LEDs through which you can interface BIB L/, JII I - IÑ o gizmo with the IN DECODING your breadboarded 1 OGIC computer. In practice, for heavy ex- OUT perimentation, it is advisable to use a separate "outboard" breadboard to INTERRUPT ÌACRNOWI EDGE LATCH and on the built -in board save wear tear EOS EOS LEDS which would be difficult to remove and replace, if damaged, because of BPTB. CE:II 1.=.125j the many solder connections. NENOBD 1_ ___ NOTE NOT ALL SIGNALS SHOWN On the breadboards you can assem- jp L.IEIMUY I AN SUMP) IED ble all kinds of gadgets and intercon- nect them to do whatever you have in The MMD -1 features the popular 8080 microprocessor system in a self- contained struc- mind -including ICs, switches, LEDs, ture which includes octal keyboard, LED displays, and access to the full bus structure. pots, and more complex outboards con- The flow chart shows some of the signal paths within the computer. With the flow chart in the unit. sisting of specialized circuits on PC and Bugbooks, you can literally put your finger on "where it's happening"

60 ELEMENTARY ELECTRONICS /March -April 1979 actual programs that illustrate the con - cepts discussed in the chapters, plus a series of related experiments (about 60 in all) you can perform on the MMD - 1, plus review questions and answers. Each experiment asks you to compare The two indicated the results you obtain with results the chips on the lower writers of the Bugbooks obtained deck are the standard when they ran the same experiments. KEX (keyboard executive) and L/D option- Thus never there's any question about al memory. These can whether your computer readouts are be replaced with KEX/ right or wrong. You should note the LD and "Monitor" index for both Bugbooks V and VI PROMs to permit sin- is at the end of Bugbook VI. gle instruction exe- You don't really need Bugbooks I cution of programs in through IV because the essential ma- the MMD -1 memory. terial contained in these earlier volumes has been consolidated into Bug - books V and VI for more convenient use with the MMD -1. Even if you can't afford the MMD -1 now, these Bug - books can teach you much about the CIRCLE 62 ON READER SERVICE COUPON way microcomputers work. Also now available is Bugbook VII which deals with advanced techniques related to recorder's earphone and auxiliary jacks trial laboratories. Thus the computer, analog converter software and hard- to the MMD -1 CAS interface using through its predecessors, has been ex- ware interfacing. It too contains many two connecting cables. tensively field tested under the most interesting and illuminating experi- Options. Many options are offered demanding applications conditions. A ments. so that you can tailor your learning compitely assembled and tested MMD -

Cassette storage of program material and experimenting computer to your 1 costs $525, down from its original is fast and easy, provided you have personal needs and budget. If funds $600 cost. In kit form, with all parts the Memory Interface Board which are limited, you can obtain the basics ready for assembly plus all instruction- comprises the upper deck of the unit and add to it more equipment as you al materials, the price is $350. shown in this article. A Radio Shack go along. The basic MMD -1 computer pro- CTR -43 portable Cassette tape record- The MMD -1 is a lower cost, simpli- vides the following hardware: a com- er is shown, but is not available from fied version of the original Micro De- plete 8080A microprocessor set includ- E & L. You can use your own com- signer (MD -1) now widely used in ing read -write and read -only memory; parable recorder just by interfacing the vocational schools, colleges and indus- direct keyboard entry of data and instructions in machine language (no data entry terminal is needed); light - emitting diode status and data indicators; an integral solderless breadboarding and interfacing socket with direct buffered access to the microprocessor set; a complete, self- contain- ed power supply. The MMD -1 is designed around the following integrated circuits: One 8080A 8 -bit single chip central processor; one 8224 clock generator and driver; four 811 -2 1024 -bit (256 x 4) static MOS Random Access (read - write) memory (RAM); two 8216 O- bit parallel bi- directional bus drivers; and, a choice of two 1702 2048 -bit (256 x 8)- electrically programmable read -only memory chips (PROMs). You can obtain either a KEX (Key- board Executive) and a separate L/D (Load /Dump program) PROM or you can opt for the upgraded version which has the KEX /LD combination on one chip and a Monitor PROM on the second chip. However, if you obtain the As indicated by the drawing above, and the other photos, the wide-open construction Monitor with KEX /LD, you won't of the MMD -1 not only makes for use as a teaching tool, but obviously makes it easy to have the convenience of the reset fea- troubleshoot circuit paths and individual) components. If you desire to experiment with ture that is coordinated with the Bug - modifications to the circuit paths, all you need do is reach right in! (Continued on page 98)

ELEMENTARY ELECTRONICS/March-April 1979 81 S TOPP!T!

Are your reflexes faster than a speeding LED?

by James J. Barbarello

NOW FAST CAN YOU REACT? One way is low until the last count, allowing IC2 to find out is by playing our LED to sequence. At the last count, pin 11 game, named Stoppit. Start by goes high, energizing LI and disabling pressing and holding the ready button. IC2. The ready LED will light and remain Another way of stopping the count on for an unspecified time. Then the is by stopping the input clock signals. light will begin "falling" at a speed IC1, a Quad 2 -input NAND gate serves determined by the skill control (the two purposes. It is used to form a illuminated light will extinguish and the gated clock oscillator (IC1C and D) one below it will go on, and so forth). and an R/S (Reset /Set) Flip Flop If the zero position is reached, this light (IC1A and B). When S1 is closed, a will remain on until the game is reset negative pulse is transmitted through by pressing the ready button. C2 which resets the R/S Flip Flop The object of the game is to stop the through D2. This causes the "Q" output action as quickly as possible (thus earn- (Pin 4 of ICIB) to go low and the ing a high score) by momentarily de- "Q" output (Pin 3 of IC1A) to go pressing the stop button. Since the high. The negative pulse is also in- ready button must be held down until verted in IC3F and resets IC2. At the the action starts, you must be quick to same time, Cl begins to discharge reach the stop button and obtain a The LEDs are mounted carefully on the PC board so that they just fit through the holes in high score. the front panel. You may have to fiddle around with the spacing between the PC board Stoppit uses readily available CMOS and project box. The diagram below shows how the various components fit on the PC board. devices, is powered by a single 9 volt battery and can be built for between $15 and $20. How It Works. The "heart" of Stoppit is a 4017 CMOS Decade Counter with decoded outputs. It contains 10 output pins that are sequen- tially energized (count from 1 to 10) with each input clock pulse. Only one output at a time is high. A high input ...... _....., . ..._...... to reset pin 15 will set the count to 1. A a44+i high input to enable pin 13 will stop iii+ the counting. ,t5r..`_i As seen in the schematic diagram, ...... wI the decade counter's (IC2) outputs drive 10 inverting buffers. When any one of the counter outputs goes high, ,r/ AMIN the corresponding buffer output goes low and sinks sufficient current to allow the associated LED to light. R7 Al .:A: .A: by the LED. Fi ü ii i:¡,, y. y; .y 'H, limits the current drawn .. Y Y , cn The last output (pin 11) is also connected to the enable pin. This output

62' ELEMENTARY ELECTRONICS /March -April 1979 through R2 and SI to ground. When the voltage across Cl decays to the CMOS low level (I/z V'), the R/S F.lip Flop is set, forcing the "Q" output high and the "Q" output low. The high "Q" output enables the clock oscillator and allows IC2 to begin counting at a rate determined by R5 (Skill), R6 and C3. R6 limits the upper frequency of the clock oscillator. Closing S2 (Stop) resets the R/S Flip Flop, disabling the clock and stopping the count. Since the set pin of the Flip Flop must be high before it can be reset, SI must be released to allow Cl to recharge through RI and D1 before S2 has any affect. Since R1 is relatively small, Cl re- charges "instantaneously." Thus, in operation, Si is depressed until the counting begins. SI is then released and ST-1 O ó bbbb S2 is quickly closed to stop the count. Power is supplied by a 9 volt battery. You can use the above, PC board template to build your own or from the Construction. Stoppit can most easily order one supplier listed below. If you do it yourself watch for those pesky PC -board short circuits. be assembled using our PC Board layout and components placement. In this way, all components except for the switches and ' skill control are mounted Got parts problems? Solve 'em with Hobby Mart, page 89. directly on the board. Note that there are 18 jumpers, 3 of which are insulated. Standard handling precautions should be observed for the CMOS devices and I.C. sockets may be used. To be compatible with the PC Board lay- RI out, 1/2" diameter LEDs should be 4700 used. The leads should be long enough so that, when mounted, the top of the LED is at least 3/a " above the PC DI Board. Mount the LEDs so that they R? form a straight line and are of uniform 2.2M 31 height. The finished unit can be mount- READI' CI gq ed in any convenient case. A simple battery holder can be made from a 3/a" x 13/a" piece of aluminum stock by forming it into a "Z;" the vertical portion of the "Z" being the dimension of the wider side of the battery. A hole I C I P14, IC3,4, PIN I = V+ can then be drilled in the lower hori- ICI, PIN 7, IC3,4, PINO C,NI zontal portion of the "Z" so that it can be anchored to the bottom of the case with a machine screw and nut. PARTS LIST FOR STOPPIT Playing The Game. When the unit is first turned on, the lights will sequence S3 C1 -1 -uf, 10 volt electrolytic capacitor -SPST slide switch and stop on the zero position. Place C2, C3- 0.1 -uf, 25 volt disk capacitor Misc -9 volt battery and battery clip; suitable the skill control near the posi- amateur D1, O2- 1N4148 or 1N914 diode case (such as Radio Shack 270 -627); one knob; tion. Depress and hold the ready but- IC1 -4011 Quad 2 -Input NAND Gate (CMOS) two #6 -32 x 11/4 " machine screws and nuts; ton. After a few seconds, the ready IC2 -4017 Decade Counter with Decoded Out- one #6-32 x 1/2 " machine screw and nut, wire, LED will extinguish and the numbered puts (CMOS) etc. LEDs begin to sequence. As soon as IC3, IC4 -4049 Hex Inverting Buffer (CMOS) this happens, release the ready button LED 1 -LED 10 -1/s" dia. LED (Such as Conti- Note -Th3 following are available from BNB and momentarily depress the stop but- nental Specialties Corp. LD -12) Kits, R.E. #1, Box 241 H, Tennent Road, ton. Repeat this process five times, not - RI -4700 -ohm, 1/4 watt resistor Englishtawn, N.J. 07726, Kit containing all ing your score each time. Your total R2 -2.2 Megohm, 1/4 watt resistor pars and P.C. board (less case and mounting R3, R4- 100,000 -ohm, 1/4 watt resistor ( STOPPIT) at $17.50; P.C. Board only score is then the sum of the five indi- hardware) R5- 220,000 -ohm, 1/4 watt resistor (STOPPIT-PC) at $6.00. Prices include postage vidual scores. As your proficiency nn- R7 -470 ohm, 1/4 watt resistor and handing. Canadian residents pleasse add creases (as noted by an increased total R6- 470,000 or 500,000 -ohm, lh watt poten- $1.00. U S. Funds only. N.J. residents add 5% score), advance the skill control. You tiometer (Audio Taper) sales taa. Please allow 3 to 6 weeks for de- may wish to challenge your family or S1, S2- Pushbutton Switch, normally open livery. friends in a test of quick reactions.

ELEMENTARY ELECTRONICS/March-April 1979 63 e/e checks out... h

B 1. Edmund Scientific's

,1,.6101 Outdoor DIGITALTHERMOMETER

Indoor /outdoor, fahrenheit /celsius thermometer lets you know when to button up your overcoat INDOOROUTDOOR THERMOMETER No 61175 coming through a window. You can in fact place the thermome- (7 EDMUND SCIENTIFIC CO. Barrington. New Jersey ter just about anywhere that it would provide the most accurate average room temperature because the wire bigltal Thermometer leading to the sensor is 12 feet long and can be extended to as much as 100 CIRCLE 52 ON READER SERVICE COUPON feet without adversely affecting accuracy of temperature readings. When a THE ONLY PRACTICAL WAY to ease suitable location is found, mount it with into the forthcoming metric age -if you two small screws provided with the are not there already -is to daily use thermometer. equipment and devices that are cali- Locate the outside sensor on the brated in the metric system. Your new north side of the house, in the shade. car, for example, probably has a Hardware is provided for mounting the speedometer /odometer calibrated in sensor in an upright position. It will be kilometers as well as miles. Now you inconspicuous anywhere because it is can enjoy and learn from a digital - only % -inch long. Again, keep the readout indoor /outdoor thermometer sensor well away from such possible sources of heat or cold as outdoor light- that permits immediate comparison of Tiny outdoor temperature sensor is only ing fixtures, kitchen and bathroom ven- Fahrenheit and Celsius readings. about 5/s -inch long and barely more than tilator outlets, clothes dryer vent or air Edmund Scientific's Indoor /Outdoor 1 /2-inch in diameter. It is inconspicuous Digital Thermometer (Stock No. 61, wherever you decide to have it located. conditioning equipment. 176) shown here is priced at $49.95. There's no need to drill holes It is ready to use after the addition of a one -digit maximum deviation test. through the house wall to pass the sen- nine -volt battery. Just mount in a con- In normal use, you move the top sor wire outside. Just run it out near venient place on an inside wall and run slide switch to either Celsius or Fah- one corner of a window. Chances are the thin connecting cable with attached renheit, and the lower switch to either that there's enough space for the thin sensor to a suitable place outdoors. Indoor or Outdoor setting. The tem- wire without the need of any cutting Three -digit Readout. The thermome- perature is indicated by red digits, or drilling. At worst, all you need do is ter is contained in a grey plastic box about % -inch high, that flash on and cut a small channel with a sharp knife will measuring 41/2 inches by 3 inches by off at about one second intervals. To in which to place the wire so that it 11/4 inches, and has a gold -colored conserve battery power, keep the ther- not be damaged by window move- faceplate with two switches and a three mometer switch off except when mak- ments. digit LED (Light Emitting Diode) ing readings. You know when the 9- In addition to having accurate infor- readout window. The faceplate pops volt battery needs replacement because mation about inside and outside tern - off easily for battery replacements. a weak battery shows only a series of peratures, you benefit additionally in Range of the thermometer is from decimals instead of the digits. having a means of teaching yourself, -31 to 122 degrees Fahrenheit and Installation. Installation of the ther- and others in your family, Fahrenheit - -35 to 50 degrees Celsius, with an ac- mometer is quick and easy, but to en- Celsius equivalents. Make a practice of curacy of plus or minus one digit. You sure accurate readings you should se- predicting what the Celsius reading will can test the instrument, before installa- lect locations for the thermometer and be after first observing the Fahrenheit tion, by placing the outdoor sensor next the outdoor sensor with reasonable reading. Or if the initial reading is on to the thermometer box in which case care. Do not place the thermometer the Celsius scale, predict the Fahren- both "outdoor" and "indoor" readings too close to a source of heat, in par- heit equivalent before checking with should be the same. If the readings ticular a radiator, or where it would be just a flick of the switch. Your kids agree within one degree, the unit is unduly cooled by air conditioning will enjoy playing the game, and will operating within the specified accuracy equipment. Also avoid a wall that is soon become very expert at making range. The unit shown here met this warmed by the direct rays of sunlight mental temperature conversions.

-April 1979 64 ELEMENTARY ELECTRONICS /March IL

e/e checks out the PERCOM LFD -400 Minifloppy Disc Compact disc system adds kilobytes of brain power to your SWTP -6800 ON READER SERVICE COUPON

ONCE YOU GET OVER 0 the initial thrill your existing SWTP 6800 software as- When you SAVE a program, the ter- of getting a computer system up and is. For example, let's assume you have minal indicates the last sector used running, and you've gotten the most the program Electro on cassette and for storage. For example, if a program complex software debugged and ready you have the Percom LFD -400 disk is saved at sector 045 and uses up two for use, there comes the time when you system connected. You simply load the sectors, the terminal will indicate LAST realize it is often more trouble to use cassette just as you did before, using a SECTOR -047. You now know your next the computer than to crawl along with cassette interface. Then you dump the program SAVE must start at sector 048. pencil, paper, and pocket calculator. program to the disk with the simple "Aha!" You say, "The Percom does Storage. The problem lies in some- command SAVE 1xxx. The numeral 1 not file by name, it requires sector thing called "storage," usually a punch- means drive unit #1 (you could use a numbers for identification of soft- ed paper tape or a cassette recording. #2 or #3 drive) and xxx is the disk's ware." Yes. It's true, sector numbers For example, assume that you want to sector number. We'll explain sectors are required in the basic no -fuss, budg- run. the program Electro we featured later. et version. You can update to number- in an earlier issue of e/e. First you That's all there is to it. The pro- ed or even name files later, but what have to load BASIC, which could take gram Electro is now on the disc. To you get for a basic price of $599.95 from 1.5 to 17 minutes depending on load Electro at a future time you would fits most all requirements for speed, whether you are loading from a 300 or simply enter the command LOAD lxxx. convenience, and price. 1200 baud cassette, or teletype punched If the starting sector was # 10, the As far as loading speed is concern- tape. Then you have to locate the cas- commands would be "SAVE 1010 and ed, SWTP's version of 2.0 BASIC loads sette or tape with Electro and take LOAD 1010." in under 10 seconds. The program another 1 to 5 minutes to load the In this manner you can transfer all Electro loads in the time it takes to program. If something goes wrong your present software to disk without a look up from your keyboard to the along the line, like a dropped bit due to major, or even minor, rewrite. CRT screen or printer. Need a differ- humidity effects on the tape player, Each disk is electrically divided by ent program? No need to search for you might have to reload, and a full a disk operating system into 350 sectors, cassettes or punch tapes and then cue 20 minutes might pass before you and each sector can accommodate 256 them to the beginning of the new pro- could use the computer to solve a bytes of storage, providing a total of gram. Just type LOAD lxxx and in the simple series of calculations. Basica;ly, 89.6k bytes of storage per diskette. time of a blink to a few seconds, the it comes down to the fact that simple storage systems are inconvenient, often making use of the computer more trouble than it's worth. For maximum utilization of a personal computer, your storage system must be extremely fast, extremely con- To load or save soft- venient, and of course, reasonably ware simply install a priced. One of the best systems we've diskette in the drive, run across in terms of speed, con- close the door, and set venience and price is the Percom LFD - the computer's stack 400, a minifloppy system specifically pointer, address A048, designed for the SWTP 6800 computer. to C000. That's the address of the Convenience. Perhaps the most con- ROM operating system. venient feature of the Percom LFD -400 disk system is that it doesn't require rewriting all the software in order to use the disk storage. You can use all

ELEMENTARY ELECTRONICS /March -April 1979 67 PERCOM FLOPPY DISC program is loaded. The controller PC The next logical question is, how board can be installed much extra memory does your com- in any motherboard puter need to use the Percom LFD -400 slot. For convenience, disk system? The answer is . . . the best location is in none. Unlike most disk systems that the last slot; the one at require at least 4K of rather expensive the rear, so the con- memory just to run the disk operating necting cable can run system, the Percom has its system, call- out the back without ed miniDOS, in a ROM that's supplied crossing any of the with the LFD -400. If your computer memory or the CPU board. Space the has, say, 12K of memory handling an boards to attain maxi- 8K BASIC, the Percom runs in the mum ventilation be- same 12K. At the time of loading tween circuit boards. BASIC from disk, only 114 bytes for the disk system are added to your "normal" BASIC. How it works. The disk system requires a PATCH to your BASIC. PATCH is simply a buzzword (or computerese) troller board on the mother board of disk operating system. (If you require meaning modification. In this instance, the SWTP 6800. That's the whole bit. anything more than the basic miniDOS it's the addition of instructions from ad- The controller board has three supplied with the LFD -400, be sure you dress 1EFO to 1F6F. Percom sup- sockets fix the 2708 type PROM One obtain the technical memos to be cer- plies a listing and a diskette for this is used for the miniDOS ROM sup- tain you know what you're getting and PATCH. You first load your BASIC in plied with the system. The other two how it can be of service to you.) the usual way, then enter the patch sockets can be utilized for user -pro- If you don't want too great an ex- through MIKBUC, and then dump the grammed PROMs, or for upgrading to pansion but could use a data file sys- BASIC with the PATCH to a disk. Next a named file system, available in ROM tem that permits up to four data files time you want to load BASIC, you sim- from Percom. The miniDOS ROM to be open at the same time, a PATCH ply load the disk, and in a few seconds provided with the basic system is al- for SWTP BASIC is available on "Soft- you have your new, patched BASIC ready programmed to handle expan- ware Diskette #2" for $10. ( "Software loaded. sion. It looks over at the next socket; if Diskette #1," which contains the basic For those who want to use the disk the socket is empty it simply provides patches for SWTP BASIC, is supplied system with the 6800 mnemonic assem- basic storage and retrieval. If the soc- with the LFD -400 system. If you need bler or the TDC text editor, Percom ket is fitted with a PROM or ROM it another one, it's also $10.) will supply the necessary patches in follows the programmed instructions. Using The system. Typical of every- technical memos at very nominal cost The LFD -400 system uses a 51/4 - thing we've received from Percom, the (ask Percom for a technical memo inch minifloppy disk of the 10 sector LFD -400 system worked instantly, catalog). "hard- sectored" type. We don't have with no debugging hassles. Also typical The LFD -400 system, priced at to get into the nitty- gritty of what of Percom, the instructions are nota- $599.95 with one disk drive, is supplied hard -sectored means, just be certain you bly clear. A small glitch with plug completely wired and tested. It is not a get the right type of mini -disk, or disk- polarity we uncovered -has been re- kit. All the user need do is install the ette as it's also called. solved by Percom in all shipments to disk drive in its cabinet (two screws), To get the system up and running users, so there's no need to go into a fit two connectors, and install a con- you just plug in the controller board (Continued on page 85) to your computer, connect the cable from the controller to the disk drive, turn on the power, and set address A048 (the pointer) to C000, the address of the ROM miniDOS. Type "G ", and the DOS (disc operating system) is ready for any loading or stor- ing operations. You can save or load the entire core (memory), part of a core, a program, or whatever. Several low cost options are available for the Percom system. The basic miniDOS can be upgraded to mini - DOS+ with an optional PROM (for circuit board has The controller printed the socket) that supports up to three sockets (on the bottom to the right #2 files Then there's of center) for EROMs (erasable read only 32 named per diskette. all its electronics are sup- memories) and PROMs (Programmable the FMS -6800 full blown file manage- The disk drive and assembled and tested as a ROM). The #1 socket is used for the mini - ment system, but it requires 4K to 8K plied completely in factory shipping cartons. DOS ROM supplied with the disk system. of additional RAM just to support the factory unit,

68 ELEMENTARY ELECTRONICS /March -April 1979 by Kathi Martin, KGK 3916 Rathi's CB Carousel President's Thomas J. is destined to go down in CB history

To MEET THE NEEDS READERS Who have taken the time to write and ask what's available in a good reliable rig, I went back over my notes and test reports and checked the 1979 CB YEARBOOK (chock full of test reports on all types of CB rigs), and found there are still good buys available. Not many, but enough to give you a decent selection. One of my favorites is Presi- dent's Thomas J., a 40- channel AM transceiver with a list price of only The front panel of the President Thomas J. doesn't look too much different because the $159.95, the last time I looked. mike /RF gain and volume /squelch controls are concentric, cutting down on the overall Performancewise, it's similar to a few total number of controls and switches. One selector switch is used for the single meter other rigs in the same general price that indicates received signal strength (S- units), RF- output, modulation, and antenna system VSWR. The black range, but it has some specialty features space to the right of the meter is the blacked -out LED digital channel indicator. If you push the extreme left hand switch under the I'm attracted to; features that, in my channel indicator the receiver and transmitter instantly switches to channel 9. For more info. circle number 46. opinion, make it an excellent value. Starting off, the President Thomas high mike sensitivity rigs with 100% a J. is housed in a cabinet 2s/í6 -in. high by modulation limiting suffer from high 71 %i6 -in. wide by 8% -in. deep. It's sup- level distortion. With the Thomas J., plied with the usual mobile mounting however, you simply back off on the bracket, a plug -in power cable for 13.8 - mike gain control until the modulation VDC with positive or negative ground, meter occasionally peaks at the "100 %" and a plug -in microphone. It has the scale calibration. (It's really better to usual LED digital 40- channel indica- start with the mike gain at full off and tor, volume and squelch controls, an advance the control until the meter just RF gain control, both a noise blanker peaks at 100% as you modulate.) The The rear apron is strictly standard: minijacks and ANL, a PA /CB selector switch, end result of setting proper mike gain and outputs for for the P.A. and external speaker; a positive/ external and P.A. using the modulation meter is some of negative ground power connection; speakers: all features and an more or less com- the cleanest, most crisp modulation to antenna receptacle. Easy to hookup. mon to the better quality transceivers. be heard on the band. Fact is, because The Frosting. The extras, which I find the signal is so free of distortion many receiver is the AGC action. An input are decided a convenience even for rou- stations claim my signal's undermodu- signal range of 2 to 10,000 µV, repre- tine CB communications, are a micro- lated, but they somehow seem to re- senting very weak and very strong sig- phone gain control, a tone control ceive every word, even when there's nals, produced an AGC action of 10 (actually a treble cut), a built in VSWR severe adjacent -channel bleedover. dB; adequate but not great. In plain meter, a panel lamp dimmer, and Speaking of bleedover, there's little terms, it means that if you have the modulation metering. Actually, all the of it in the Thomas J. The receiver volume cranked open to work a weak meter functions are provided by a sin- section, whose sensitivity I measured at station a strong signal coming on the gle meter that is switched by a front 0.4 V. for 10 dB S +N /N ratio, has channel is going to come in a bit on panel selector to indicate the usual S/ 62 dB adjacent channel rejection, and the loud side. RF- output, and modulation and VSWR. a Delta tune covering ±1.5 kHz helps Calibration. One the flip side of the The microphone gain control pro- you tune in stations which might be out the coin, however, there's a calibrated vides sensitivity adjustment from full at the limits of permitted tolerance. S- meter. S9 represents 100 FV, and off to about -38 dB, meaning it can (It's hard to tune a station out at the each S -unit is 5 dB. If you're helping fully modulate the rig with little more tolerance limits when your rig has high someone make antenna system adjust- than a whisper. The problem with high selectivity if you don't have some form ments you can give a reliable measure- mike sensitivity is the distortion if you of Delta or fine tuning.) ment that means something, not some speak in a normal voice. Almost all The only complaint I have with the (Continued on page 88)

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ELEMENTARY ELECTRONICS /March -April 1979 71 CRAIG 1 -131

MIDLAND 18 -999

CB XCVII R1 -3600 PANASONIC CH ECKOUT ROYCE 582

Modulation limited to 100% yes CRAIG L131 nel indicator, S /RF- output /SWR Editorial Remarks: The 78 -999 has $299.95 (Craig Corp.) meter. Mobile bracket automatically General Description: A 40- channel disconnects antenna and speaker con- a 5 dB per unit S- meter, double con- AM /SSB transceiver for mobile and nections when transceiver is removed version, jacks for P.A., remote speak- P.A. operation. Fine tuning ±800 from the car. ers and headphones, L.E.D. digital indicator, separate meters for Hz is provided. Power supply is 12 channel to 13.8 VDC with negative or posi- MIDLAND 78-999 percent modulation, RF- output/ tive ground. Overall dimensions are $699.95 (Midland International) SWR, and S -unit. General Description: A 40- channel AM /SSB transceiver for mobile, P.A., base operation. Fine tuning ±800 Hz is provided. Power supply is 12 to 13.8 VDC with negative ground and 120 VAC. Overall dimensions are 6 -in. H x 14- 27/32 -in. CIRCLE 54 ON W x 11- 13 /16 -in. D. There are front READER SERVICE COUPON panel controls for: channel selection, PANASONIC R1.3600 CIRCLE 42 ON READER SERVICE COUPON volume, squelch, clarifier, RF gain, $299.95 (Panasonic) 21/4-in. H x 81/2-in. W x 101/4-in. D. MIC gain, tone, P.A. gain, SWR General Description: A 40- channel There are front panel controls for: CAL. Switches for: Antenna A /B, AM transceiver for mobile or base channel selection, volume, squelch, SWR CAL, noise blanker, ANL, operation. Power supply is 12 to 13.8 clarifier, SWR Cal /local- distance AM /SSB modes, CB /PA, high Audio VDC with negative or positive ground sensitivity. Switches for: CB /PA/ and 120 VAC. Overall dimensions Panel lamp dimmer, noise blanker/ are 5-3/16-in. H x 13-9/16-in. W x ANL, AM /SSB mode, S /RF /SWR/ 83/4 -in. D. There are front panel con- Cal. meter function. Standard acces- trols for: channel selection, volume, sories include a microphone, DC squelch, and RF gain. Switches for: power cable, quick-release mobile noise blanker /ANL, and preset chan- bracket. CIRCLE 48 ON nel selector. Standard accessories in- SERVICE COUPON Receiver Section Test: READER clude a microphone, mobile mount Input sensitivity 0.3 Al frequency filter, channel lamp dim- and DC power cable. Adjacent channel rejection 77 dB mer. Standard accessories include a Receiver Section Test: AGC action 13 dB microphone, DC power cable, A.C. Input sensitivity 0.3 µV SSB opposite sideband power cord. Adjacent channel rejection . 64 dB rejection 50 dB Receiver Section Test: AGC action 13 dB Input level for S9 meter Input sensitivity 0.6 µV Input level for S9 meter indication 1000 AV Adjacent channel rejection 52 dB indication 60 µV Transmitter Section Test: AGC action 13 dB SSB opposite sideband AM RF output 3.7 watts Transmitter Section Test: rejection 50 dB SSB RF output 11 watts P.E.P. AM RF output 3.5 watts Modulation to 85% yes Input level for S9 meter Modulation to 85% No 75% Max. 150 µV Relative sensitivity for 85% indication Relative sensitivity for 85% mod. -32 dB Transmitter Section Test: mod. -39 dB 3.8 watts Modulation limited to 100% yes AM RF output Modulation limited to 100% yes Editorial Remarks: The L131 has a SSB RF output 11 watts P.E.P. Remarks: The RJ -3600 has relative reading S- meter, double con- Modulation to 85% yes Editorial relative reading S- meter, jack for version, jacks for P.A. and remote Relative sensitivity for 85% a speakers, incandescent digital chan- mod. -40 to -12 dB (Continued on page 98)

ELEMENTARY ELECTRONICS /March -April 1979 72 111 j computer of Yyour est. chargeia Keep in prof ne v, With this ° Herb Friedman

cable is plugged in, and to also monitor the recorder. loads and dumps. The complete controller is amazing: THOUGH THE COMMON CASSETTE re- The monitor hookup depends on the No power supply, ICs, transistors, bat- corder, used as the data storage sys- particular model cassette recorder you teries, or LEDs! A few jacks, switches, tem for many hobby and personal use. The audio feed from the recorder a small speaker and some patch cords computers, is both inexpensive and re- to the computer is generally taken from are all that's needed. (We could have liable, it is also a pain -in- the -RAM. the monitor jack of the recorder, which done it the hard way with a few ICs Most computers control the start- is an output for an external speaker or and transistors, but why waste money ing and stopping of a recorder's motor earphone that disconnects the recorder's on unnecessary parts.) via a control cable and plug from the internal speaker when a patch cord is The only critical area is the cabinet, computer's recorder interface to a jack plugged in. Most inexpensive recorders or the front panel on which the jacks on the side of the recorder. It is impos- also provide a monitor jack output for are installed. It must he made of plastic sible to run the recorder manually. You the record signal even though the or some other insulator. Many com- must pull out the remote control plug speaker is turned off. By bridging a puters are sensitive to ground loops be- if you want to rewind the tape, or do small speaker across the connection to tween a recorder's input and output anything else to the tape, such as skip- the monitor jack it's possible to hear the jacks, and for this reason there must be ping forward to other data, or to a signal feed to and from the computer. no common connection between the two "clear" section of tape for additional You might have other problems with in the controller. Similarly, the remote data recording. Then you must reinstall load and dump, but by hearing the sig- motor control jack (J3) must also often the remote control to return the re- nals you'll at least know there actually be electrically insulated from J1 and corders' on -off operation back to com- is a computer signal going in and out of J2's common connection. By mounting puter control. Another problem with most cassette installations is that you can't hear what's going on. Is the tape really feeding data to the computer? Is the corn- puter really feeding data to the cassette? If we had a dollar for the times many of us hit the LOAD key -only to realize minutes later there was no feed to the computer-we could probably afford a disk system, Surely, we could afford a disk if we also had a buck for every time we dumped from the computer only to discover too late the recorder wasn't in the record mode, or there was no dump when we thought there was. Though many personal computers provide some form of bell, whistle, or terminal indication that the computer is loading or dumping, it's most convenient to hear what's going on. For something like ten dollars and a short evening's work you can build a Personal Computer Tape Controller that allows you to manually control the The Tape Controller connects between the computer's record interface and recorder's the cas- motor and functions even sette recorder, allowing monitoring of both the record and playback signal(s), as well when the computer's remote control as providing forward and reverse control without pulling the remote control patch cord.

ELEMENTARY ELECTRONICS, March -April 1979 73 TAPE CONTROLLER

all three jacks on a plastic panel or cabinet the whole ground loop problem is avoided and the controller is truly universal. The speaker can generally he any 8 or 16 -ohm miniature type 1.5 inches or larger. It is cemented with "airplane" or "model" cement directly to the panel -its muffled sound will be adequate for monitoring. Resistor R1 is used only if you want to lower the speaker volume (which is 'often unnecessary because of the muf- fling). Experiment with 1/2 -watt values from about 15 -ohms upwards until you get the desired sound level. While you could install a potentiometer (about 50 or 100 -ohms) to provide a variable tape couldn't be more straight -forward. There's no power volume adjustment, such is not an easy Construction of this controller However, there is one critical area -the front local parts dis- supply, ICs, transistors, batteries or LEDs! value to locate at your installed thereon must be electrically isolated from each other. This extra conveni- panel. The jacks tributor, and the slight is because many computers are sensitive to ground loops between a reorder's input ence isn't worth the extra cost. and output jacks so the controller must not make a connection between the two. The best Jacks J1, J2 and J3 match the exist- bet is to just avoid the entire problem from the beginning. Use a plastic panel /cabinet! ing plugs on the connections from your computer's recorder interface, and plugs control, are the sub -miniature type. ally, set S2 to manual (closed), there- P1, P2, and P3 should be identical with Using The Controller. Connect the by shorting the recorder's remote con- the interface plugs. As a general rule, wires from your computer or computer trol circuit. When you want the corn - J1, J2, P1, and P2 carry the audio sig- interface to J1, J2, and J3. Connect Pl, puter to start and /or stop the recorder, nals and are the miniature type. J3, and P2 and P3 to your cassette recorder. set S2 to the open position. (When S2 P3, which are the recorder's remote To operate the cassette recorder manu- is closed it's the same as if you had pulled out the remote control plug from the recorder's remote jack.) ---1111parts? Hy art: page 89. { To monitor either the output from, or input to, the recorder, close Si. If `0 RECORDER'S you find the monitor sound disturbing MONITOR JACK after the load or dump starts simply open SI; it has no effect on the load or dump. If your computer requires the load start on the recording's marking PL2 avoid, a entry at the TO RECORDER'S tone to "garbage" INPUT JACK point where the marking tone corn - mences, close S1 so you can monitor the recorder output, close- S2 so you can operate the recorder manually and PL3 until you hear the start J3 ¡ play the tape v TO RECORDER'S (.) ) REMOTE CONTROL of the marking tone, then open S2 as S2 JACK soon as you hear the tone. This returns cassette control back to the computer.

PARTS LIST FOR TAPE CONTROLLER You can now commence the load without fear of "garbage" caused by the 11, 12- Miniature jack, see text. St, S2 -SPST switch. start of the marking tone. 100 -ohm resistor, 1/2-watt, see text. 13- Subminiature jack, see text. R1 -50 to (Note. This controller is intended for 11, 12, 13. See text. Pl, P2, P3 -Plugs to mate with recording systems that utilize audio text. Mlsc.- Cabinet or panel made of plastic or tones to represent data, such as the so- SPKR -8 or 16 -ohm miniature speaker, see other insulator; wire; etc. text. called Kansas City, or Byte /Manchester systems. It is not intended for record- even be smaller if ing magnetic impulses, such as NRZ, Speaker SPKR 1 can be anything from 1.5- inches and larger. It can which generally provide input you happen to stumble across one of those surplus mini- speakers that still sell for an /out- about 50- cents. The speaker is cemented to the front panel with silicon rubber (RTV) put monitor as part of the recorder.) adhesive, or "airplane" or model cement. Do not try to use one of the new instant - Be in control of your computer by The drying cements such as Krazy -glue -they won't stick to the speaker's fiber "front." building this little device. We think switches shown have more terminals than needed for SPST. They are "surplus," selling you'll agree it will be one of your most for much less than a "new" SPST switch. Use whatever you can get most cheaply. useful computer accessories.

ELEMENTARY ELECTRONICS !March -April 1979 74 WHETHER YOU SERVICE your own screen. Sync signals are also available the 3.56 MHz oscillator. Be sure that color and /or black- and -white television at a front panel jack, for servicing sync any TV receiver you use as monitor equipment because you truly enjoy elec- circuits without video, or sets having during these adjustments is in good tronic troubleshooting, or because you separate video and sync demodulator working condition because a malfunc- are primarily interested in holding down phase adjustments. There's RF output tioning set can lead to endless con- spiraling professional TV repair costs, for channels 2 through 6, and an RF fusion. you need more sophisticated test equip- level control varies the RF output for Two methods are provided for check- ment than your battered, but faithful checking relative sensitivity and to pre- ing the video output signals. The first old VOM. Basically, you must have a vent overloading the RF and IF circuits method utilizes an oscilloscope. The generator capable of producing a broad of the receiver. A switched, crystal - clarity and details of the patterns are variety of test signals to reveal what's controlled 4.5 MHz sound carrier aids directly related to the bandwidth and right or wrong in complicated TV cir- in fine tuning the Vectorscope to the triggering of the oscilloscope used. This cuitry. One of the most versatile in- receiver channel frequency. is the procedure to use if you have a struments you are likely to find for A video signal is available for scope. A chart shows how to set os- either home or pro -shop TV repair is Heath's model I0-4101 Vectorscope. Not the least remarkable feature is the modest price of $169.95. /e assembles the... First, a word of caution. Although you should have no difficulty assembling the kit if you follow Heath's typically excellent assembly instructions to the letter, give a thought to how ready you are to actually use the instrument. The Vectorscope is not a magic solution to all TV problems in the hands of one whose only acquaintance with TV equipment is through channel -selector buttons. To use the Vectorscope, you must already know a fair amount about the inner workings of a TV set, or be prepared to spend much time and effort- educating yourself in such knowledge. Super Test Set. This all -solid -state instrument generates all the stable crystal- controlled test signals needed to CIRCLE 1 ON produce color and convergence patterns READER SERVICE COUPON required to adjust color circuitry and tri -gun convergence systems. Twelve patterns, including dots, crosshatch, horizontal and vertical lines, gray scale, and color bars are available in either the standard 9 by 9 display or an exclusive Heath 3 by 3 format. Heath A clear ras- ter for purity adjustments can also be produced. The Vectorscope is much more than a typical pattern generator because it ØEGTHIIXGHPE includes its own cathode -ray -tube dis- Budget TV tester does almost everything but change tubes play that shows a characteristic waveform for each type of color TV receiver. The petal -pattern or "Daisy" troubleshooting video circuits; it's ad- cilloscope controls and what waveform display waveform is a voltage represen- justable with a level control. The characteristics to expect for various dis- tation of all ten color bars, an exact chroma signal is also adjustable for play settings such as purity, dots, cross- representation of the chroma signal be- amplitude and is used to check color hatch, horizontal and vertical lines. ing fed to the guns of the CRT in the hue and sync with different signal lev- If an oscilloscope is not TV receiver. available, It can reveal a missing, els. Front panel switches are provided you'll have to connect the Vectorscope or weak color, and show the correct to turn the individual red, blue, and /or to the video detector and sync detector setting of the burst phase transformer, green beam currents on or off during output of a TV receiver. Heath doesn't reactance coil, oscillator coil and band - convergence checks. hold your hand at this point, or attempt pass controls. The color demodulathon Generator Tests and Adjustments are to tell you where to find these detectors angle may also be checked." needed, after assembly, to put the Vec- in your TV set; it's assumed that you ,Crystal-controlled horizontal and torscope itself into proper operating already know your way around inside vertical sync pulses are incorporated condition. A black- and -white TV re- a TV set. Instead of observing wave- into the Vectorscope output signals to ceiver may be used, for all adjustments forms, as with the oscilloscope, you provide necessary blanking and to lock except for the color bar displays, the now compare TV screen patterns with , the various patterns firmly on the TV vector displays, and the adjustment of a set of drawings of normal patterns.

ELEMENTARY ELECTRONICS /March -April 1979 75 VECTORSCOPE

Vector Display Adjustment. A four - wire cable coming from tho Vector - scope terminates in four alligator clips. Three have insulation -piercing needles built into the jaws which make quick and easy connections to chroma leads going to your TV receiver's picture tube. You have to know how to identify these normally color-coded chroma leads. The fourth alligator clip, without needles, goes to chassis ground. You also need to know whether the chroma signal in your TV receiver is fed to the cathodes or grids of the CRT, and then set a switch at the rear of the Vectorscope to either "Cath" or "Grid," as the case may be. The luminance (black- and -white) signal must be bypassed to ground on receivers that have their chroma signals applied to the cathodes of the picture tube. If there is no service switch in the receiver that grounds the luminance signal, the Right,The internal connections of signal must be bypassed by insertion of required for the generation the vector patterns. Left, the sim- an electrolytic capacitor bet*een the back of and ple connections on center lug of the contrast control the set for dot, line, and color chassis ground. bar generation. The channel, chroma and RF controls on the Vectorscope are used to, you must have basic knowledge about proper setting before going on to the one create the proper petal ( "Daisy ") pat- TV circuitry, we mention in passing next one. If you have more than on tern as shown in photographs in the that adjustment of the vector display TV receiver available, try the tests Heath manual; the shape depends on also calls for disabling the burst am- all of them and note any small differ- whether the receiver is grid -fed or plifier by removal of a transistor or ences in the displays. cathode -fed, and on whether y au are tube, depending on the type of TV re- Color guns in TV receivers that using the 9 by 9 or 3 by 3 format. ceiver used.. And you must know how apply chroma signals to the grids can Don't overlook the important fact that to adjust the reactance coil for the most be turned on or off with the gun the size and shape of the petal pattern stable color picture. switches on the front panel of the is also influenced by the color, tint and Using the Vectorscope. To effectively Vectorscope. If the chroma signals are horizontal hold controls of the TV re- and properly use the Vectorscope, you applied to the cathodes, the guns can ceiver. Although you will have pre -set must know the correct pattern display be turned off by turning down the the focus and astigmatism, pull off the of an aligned TV receiver. Use manu- screen (drive) controls, using the actual knobs on the Vectorscope's horizontal facturer specifications if they are avail- procedure that pertains to the type of and vertical position controls to get at able. Otherwise hook the Vectorscope TV receiver under test. the hollow shafts, and use a small to a properly functioning receiver, and The Heath manual tells how to use screwdriver to touch up the petal pat- misadjust each coil carefully as you the Vectorscope to perform standard tern if it seems too fuzzy. However, observe its effects on the pattern on the adjustments of TV receivers, but you don't expect to get razor -sharp edges TV screen or Vectorscope CRT. Attach may wish to obtain a good color TV on the petals. a "tape flag" to the alignment tool so servicing book for additional informa- To further emphasize the fact that that you can return the coil to its tion, especially to understand how to judge receiver performance by obser- vations of variations in the color bars of your particular set. Summing Up. Clearly, the Heath Vec- torscope is an extremely versatile tool that can help squeeze out every last bit of performance inherent in the design and construction of your color or black- and -white TV receiver. But it can do that only if the instrument is used knowledgeably. If you take time to become truly familiar with your Vec- torscope's Daisy and other patterns, you'll be in clover for the rest of your The lefthand TV screen shows the pattern used for convergence and linearity adjustments. TV troubleshooting days. The right screen is for vertical linearity and pincushion adjustment. Both use a 9 -by -9 setting.

ELECTRONICS /March -April 1979 76 ELEMENTARY IMPUTER READOUT by Tom Williams

How computers communicate with the real world

MOST PEOPLE WHO HAVE begun in- This means that an incredible variety Each sample that is read by the com- vestigating the world of computers are of specialized I/O devices and pro- puter represents the value of the analog. probably familiar with the most com- grams must be devised and tailored to signal at a given point of time. For an mon means of communicating with the the specific application. These can range eight -bit A/D converter, this value can machine -the keyboard terminal. This from sensors of all kinds to stepper be resolved into 256 increments (28 = type of input /output, or I /O, device motors, valves and electric trains. We 256). For example, it would be possi- reads the different keystrokes typed by will now look at some of the general ble for such a device to measure a the operator and converts each into a methods that are used to interface a range of temperatures from 0 degrees distinct pattern of l's and 0's which computer to the outside world. to 100 degrees Celsius to an accuracy are then transmitted to the computer through one of its I/O ports. A port DOTS ON WAVE FORM SHOW VALUES SAMPLED BY COMPUTER is simply a location (sometimes a memory address) where the CPU looks for incoming information from the terminal and to which it transfers data to be 256 POSSIBLE read by the terminal. INCREMENTS FOR For the computer to receive mean- 8 BITS ingful data from a keyboard terminal, the operator must first formulate it in terms of the alphanumeric characters O TIME available on the keyboard and the com- SAMPLING RATE I l l l l l l l l l l l l l l l l l l I I l puter must be programmed to interpret l l l l l l l l l the symbols sent to it. This works quite well for a great many applications, but A computer can represent a wave form by sampling the level of the wave at a given point in time. The computer what if we want the computer to do can interpolate the wave in between the points. The audio industry is just starting to use this same technique to make something that requires so much con- master recordings at the studio. The record albums that are produced are clearer and have more range than analog stant input that the task of formulating recordings. it and typing it in all the time would Analog to Digital. Since the real world of better than 0.4 degrees Celsius! This be too dull and repetitive for a human does not normally present convenient accuracy can be enhanced by more to put up with all the time? digital data, some method must be complex (and more expensive) 10- or Computer Control. Let us take for an found to translate analog signals into 16 -bit converters. example, the task of reading -and later digital data. The general device for do- The opposite of A/D conversion, controlling-the temperature in some ing this is called an analog to digital, digital to analog conversion, is also device. While that job could be done by or A/D converter. An analog signal done, often on the same circuit board a simple thermostat, we will see that such as an audio wave, has constantly known, naturally, as an ADAC. Here, using a computer will enable us to ex- changing values so the best a digital de- the digital information is output at a pand incredibly the possibilities for vice can hope to do is to sample posi- specific rate to a network of resistors, using the temperature data it reads. tions of the wave and to approximate filters and op amps to produce an ana- The first problem is to get the infor- its shape in the form of digital informa- log signal. The most sophisticated D/A mation into the machine. We could tion. Given the speeds at which corn - converters are used in computer music have an operator read a thermometer puters operate, this can be done with applications where the highest quality and type the readings in via the key- surprising accuracy. complex waveforms are essential. board, but he would soon get frustrated, Let us look at the wave form shown One inexpensive example of these especially if we wanted readings every here. It is applied as a continuously principles, now available to hobbyists, half second or so. With the computer, varying voltage to the input of the A/D is the Data- BagTrt speech processor we can do it automatically. This whole converter which is at one of the com- made by Mimic Electronics (P.O. Box subject of automatic data gathering and puter's input ports. The computer then 921, Acton, MA 01720). This device external control is called process con- reads the instantaneous value at regu- allows the user to digitally record his trol. It is simply obtaining information lar intervals and accepts the digital voice in the computer's memory and from the real world, processing that value through its port. It can thus form then play it back by having the com- information according to a program in an approximation of the wave form. puter output those memory contents the computer's memory and performing The greater the frequency of this sam- through the D/A section of the Data - actual operations based on that infor- pling rate, the more accurate the digital Bag to a speaker. In all this there mation. is a approximation will be. tradeoff the user must be aware of. The

ELEMENTARY ELECTRONICS /March -April 1979 77 A typical such device can monitor 16 and destroying components. The solu- channels by rapidly scanning the inputs. tion for simple on -off functions is to COMPUTER READOUT In much the same way, an automobile isolate the voltage with an opto- isolator. distributor can service 8 different spark As the diagram shows, this is a device plugs seemingly at the same time. consisting of a photo transistor and an faster the sampling rate, and hence the Parts of the computer's program can LED. The LED is connected to the more accurate the representation of the then store the different values in mem- computer output and is totally electric- wave form, the more information must ory locations alloted to the different ally isolated from the phototransistor. be stored -and the more memory must input channels. This information can The phototransistor is turned on by the be taken up with stored data. then be manipulated analysed and out- light emitted when the LED is on. It Of course, most real world applica- put in whatever manner the program- can thus be used to turn on any type tions are concerned with more than just mer thinks best. of relay or other device while protect- inputting and outputting the same information. The real power of the computer, after all, is to process the information and make decisions based on it. And the true purpose of real -world con- HOW AN OPTO - ISOLATOR nections is to enable the computer to CONNECTS COMPUTER act independently on those decisions. In OUTPUT TO AN EXTERNAL this context, then, they are merely the LOAD things which implement the end results the weak of the processing which is the com- Connecting output of a computer puter's main task. to a high- powered Control. By outputting analog signals, electro mechanical the machine could be used to control device requires a de- conventional analog devices. Let us take vice like this opto- a look at our example of temperature isolator. The only control. The A/D coverter, under soft- link is the light from to the pho- samples and presents tern - the LED ware control, There to the computer totransistor. perature readings be no feedback this data can which reads and compares with a circuit like the with its program information. If the one shown here. temperature is outside the specified par- ameters, the computer outputs a digital value to the D/A converter which applies the proper analog voltage to the danger- motorized temperature control until the There are two more devices that are ing the computer circuits from readings again satisfy the limits in the very important in process control appli- ous voltage. program. cations. The first is the real time clock. This is the type of device we would and activate Well, we certainly don't have to in- Since all computer functions are con- use to sound alarms in computer de- vest in a computer simply to use it as trolled by various timing circuits sprinkler systems if our conditions, in our a thermostat! As I said and will empha- "clocked logic" there is a central timing tected dangerous oscil- Of course, with the size again, the power of the computer reference in the form of a crystal chemical process. of things that lies in its speed and its ability to ana- lator known as the system clock. It's computer in charge lyze large amounts of data and make typical frequencies in home computers should not happen. could use the decisions based upon it. So let us set are between 2 and 4 MHZ. Since a If it did, the operators the recorded data our machine a somewhat more chal- crystal controlled clock is extremely ac- computer to analyse functions lenging task. curate, divider circuits can be added to and the records of its control entire proc- Multiple' Data. We have a chemical give the system an internal source of to generate a report on the then be printed process in which the computer must time reference calibrated in hours, min- ess. This report could for the chem- simultaneously monitor several ther- utes, seconds and fractions of seconds. out in an orderly format decisions as mometers, flow meters and pH meters, The computer can then be programmed ists to look at and make changes would be control various valves and 'temperature to refer to this time standard in order to what program control to controls, and, in addition, prepare a to time and delay the external processes necessary in the process did not human -report on materials used, tem- it is controlling. make sure such a disaster perature variations and the like. In ad- The other important device is one reoccur. us back to the point dition, it must be alert for critical con- which enables the computer to turn on And that brings ditions (or combinations of conditions) and off high voltage or high power I have been emphasizing. The program data are and sound an alarm, and shut down devices safely. Obviously, the low volt- control and analysis of the external de- operations if necessary. It should be age levels present at a computer's out- the crucial aspects. The and carry apparent that the main problem here is put port are not capable of controlling vices must sense accurately But not so much in the various on -off or large devices by themselves. One solu- out the machine's orders exactly. tool analog devices at the machine's ports, tion is to use them to turn relays on the whole system is still merely a the power of but more in the considerations put into and off which in turn controls the which is used to extend the software program. devices that do the actual work. The the human mind in the same way the Having the computer monitor many problem with relays and transistor lever extends the power of the human different inputs simultaneously is ac- switches is that there is danger of high muscle. Whether we use it properly is complished with an analog multiplexer. voltage getting back into the computer still up to us.

78 ELEMENTARY ELECTRONICS /March -April 1979 BASIC COURSE IN ELECTRICITY 010 &ELECTRONICS

ELEMENTARY ELECTRONICS takes a look at the diode -the electronic one -way street. By its ability to pass current in only one direction it allows us to change alternating current into direct current. Try to imagine what electronics would be like without these dynamic little devices. This series is based on material appearing in Vol. 1 of the 5- volume set, BASIC ELECTRICITY /ELECTRONICS published by Howard W. Sams & Co., Inc. C $25.50. For information on the complete set, write the publisher at 4300 West 62nd St., Indianapolis, Ind. 36268.

UNDERSTANDING DIODES SEMICONDUCTOR DIODE AND SYMBOL What you will learn. Diodes are used in virtually all electronic circuits. They are simpler than, CATHODE N-TYPE 111114 ANODE but similar to transistors. When you under- EXCESS ELECTRON stand simple diode action you are halfway to un- D RECTION OF ELECTRONS DEFICIENCY -..,RRENT FLOW derstanding transistors. The diode is a device JUNCTION through which current passes easily in one direction, but very little or not at all in the other direc- preventing the electrons in the N material from moving tion. In this article you will learn of the common over to the P material. However, when a voltage is ap- uses of diodes, and how they work in circuits. plied (as shown in the drawing) the barrier is over- come and electrons flow from N to P. The schematic WHAT IS A DIODE? symbol used for all solid -state diodes is also shown. A diode is an electrically operated device which has Voltage polarities necessary for current to flow are two elements (or terminals). If a voltage source is ap- labeled on the symbol. Current flows through the diode plied to these elements in the correct polarity, current toward the arrowhead. flows through the diode. However, if the polarity is reversed, very little (if any) current passes through. QUESTIONS A solid -state diode contains two dissimilar metals 01. N -type germanium has an (excess, deficiency) of or two different types of semiconductor materials. Cur- electrons. rent flows across the junction formed between the 02. From anode to cathode in a diode is a direction differing materials. of resistance. Q3. The identifying symbol for the anode is a +. DIFFERENT TYPES OF DIODES ANSWERS Al. N -type germanium has an excess of electrons. A2. From plate to cathode in a diode is a direction of high resistance. A3. The symbol for the anode is +.

HIGH - CURRENT DIODE REACTION TO AC AND DC It can be easily SILICON shown that a diode allows current to flow in one direction and not in the other by con- LASS- ENCASED structing the circuit belcw. A 1.5 -volt lamp, an am- HIGH - FREQUENCY meter, and a diode are connected in series across a 1.5 -volt cell. (Semiconductor diodes are distinguished Semiconductor Diodes -A semiconductor diode is made of the same materials as those used in transis- CORRECT DIODE CONNECTION tors, usually germanium or silicon. The silicon diode CURRENT is more expensive than the germanium diode, but is able to handle a greater amount of current. During manufacture, a tiny block, identified as P -type, is treated in such a way as to have a deficiency of electrons. Another block is identified as N -type, and is treated to have an excess of electrons. Such a diode is often called a PN junction. When joined, a voltage barrier forms at the junction,

ELEMENTARY ELECTRONICS /March -April 1979 79 upper terminal. Therefore, the anode of the diode is positive with respect to the cathode. A changing half cycle of current flows. If an oscilloscope is connected across the load resistor, an exact picture of the changing voltage drop will be shown. This changing voltage will look exactly like the waveform at the voltage source. DIODE REACTION TO AC POSITIVE HALF -CYCLE from each other by a number -letter designation. The diode recommended for this circuit is a 1N34). With the connections made as shown, current will flow and the lamp will light. The ammeter will record very close to 200 milliamps. Now reverse the connections of the diode. Will the lamp light? No. And, as in the next drawing, the meter pointer will indicated NEGATIVE remain on zero. The anode -to- cathode resistance of HALF-CYCLE- the diode is sufficiently high to prevent a flow of cur- P K rent. A small amount may leak through, but it is not AC VOLTAGE LOAD enough to record on the meter. SOURCE RESISTOR RECTIFYING AC NO CURRENT NO VOLTAGE To rectify means to convert AC to DC. a rectifier is a device that accomplishes this, and a rectifying During the next half cycle, the upper terminal voltage circuit is one in which it is done. A diode is a rectifier. becomes negative with respect to the lower, and the diode anode is negative with respect to the cathode. ALTERNATING CURRENT As you know, current will not flow under these condi- ONE CYCLE ONE CYCLE ONE CYCLE tions. Since the diode presents a very high resistance +15 in the circuit, all of the source voltage will be dropped + I O -A2AYCLES; across it. No voltage will be displayed across the load resistor. 0

-5- NEGATIVE QUESTIONS -Io- HALF 04. As the circuit is connected above, only the -Is - CYCLES half cycles of the AC voltage will appear TIME IN SECONDS across the load resistor. 05. A rectifier converts to the waveforms that will You know that an alternating voltage increases and 06. Draw a diagram showing R in the above circuit. decreases in positive voltage during a half cycle and appear across in the next half cycle makes the same changes in ANSWERS negative voltage. A4. As the circuit is connected, only the positive half As long as the voltage is generated, the positive and cycles of the AC voltage will appear across the negative half cycles repeat themselves alternately. load resistor. to DC. PULSATING DC A5. A rectifier converts AC A6. See diagram below. A DC POWER SUPPLY Most electronic equipment requires DC voltage to operate its circuits. Since alternating current is the normal supply, a power -supply circuit is used to pro- DIODE REACTION TO AC vide the required DC voltage. current flow in a diodç circuit with AC How does FILTER CIRCUIT voltage applied? Remember, current flows in one di- voltage obtained from rection through a diode only when the anode is more The diagram shows the output flows in only one positive than the cathode. the rectifier circuit is DC- current DC. In fact, How does current flow in a diode circuit with AC direction -but it is not smooth, nonvarying is a series of voltage applied? Remember, current flows in one di- it is called a pulsating DC. The waveform rection through a diode only when the anode is more pulses. valleys of the pul- positive than the cathode. Filtering Action -The peaks and out by a filter cir- During a positive half cycle, the upper terminal of sating waveform can be smoothed to (smooth) out the source is positive with respect to the lower termi- cuit. A capacitor can be used filter nal. This means the lower terminal may be at zero some of the changes. to maximum positive, volts, but it is negative when compared to the positive As the source voltage rises

ELEMENTARY ELECTRONICS /March -April 1979 80 1 or

ANSWERS A7. The pulse -like waveform developed by a rectifier circuit is called pulsating DC. A8. The changing voltage pattern made by these pulses can be smoothed out by a filter circuit. A9. The filter capacitor begins to discharge as soon as the positive voltage input begins to decrease. A10. The filtered output is called a DC ripple. FULL -WAVE POWER SUPPLY The preceding circuit is a half -wave rectifier. It al- current flows through R1 and the rectifier. Some of lows only half the AC wave (positive half cycles) to the current also charges the capacitor to the value of appear across the load resistor. Full -wave (both posi- the source voltage. tive and negative half cycles) rectification can be obtained with the switching action of the diodes in the DISCHARGING CYCLE circuit below.

P FULL -WAVE RECTIFIER

+ CI R

NO CURRENT DISCHARôE

GI + RI At the instant the applied voltage begins to decrease, Cl starts discharging, trying to maintain the same voltage level. The discharge path of Cl, however, DISCHARGE I is through R1. The current from Cl cannot flow back- ward through the rectifier. Since resistance regulates POLARITY REVERSAL the time of discharge (10 RC time constants to dis- I - - charge completely), the discharge time is slow. As shown in the diagram below, the output waveform does \ J 2 4 not follow the descending curve of the input. It decreases at a much slower rate. + 1 HALF -WAVE RIPPLE VOLTAGE L...imn

NEGATIVE HALF CYCLE DISCHARGE J

1 / L_ L _ J L _j On the positive half cycle, current leaves the lower During the negative input half cycle, the rectifier terminal of the AC voltage source and enters terminal does not allow current to flow, but the capacitor con- 3 of the 4 -diode network (called a bridge). The bridge tinues to discharge. The discharge current decreases is positive to negative from top to bottom because of as the capacitor charge grows less. On the next posi- the source polarity. Diode B has a negative cathode tive swing, the rectifier does not conduct current until and a positive anode, but diode D has reverse polarity after the input voltage has increased to an amount across it. Current must therefore flow through diode B equal to the charge on Cl at that instant. The anode to terminal 2. This current charges Cl and flows must be more positive than the cathode for the recti- through R to terminal 4. Because of polarities, this fier to conduct. The sequence continues. The resulting current must flow through diode C. Diodes D and A output waveshape (in solid lines) is shown below. Such are of the wrong polarity. an output is called DC ripple voltage. QUESTIONS FULL -WAVE RIPPLE LTA c" Q7. The pulse -like waveform developed by a rectifier circuit is called / \ 1/ \\/ \ \/ \\/ \/ \`/ 08. The changing voltage pattern made by these I POS. r NEC. POS. + ) NEG. V POS. i NEG. j pulses can be smoothed out by a circuit. Cl charges as the voltage increases and discharges 09. The filter capacitor begins to as during the voltage decrease, just as in the half -wave soon as the positive voltage input begins to circuit. decrease. During the negative half cycle, the polarities of the 010. The filtered output is called a voltages on the four diodes are reversed. Current leav-

ELEMENTARY ELECTRONICS /March -April 1979 81 the changes from occurring. The iron core in- ing the upper end of the source arrives at terminal 1. venting a choke coil. The voltage on diode C is of the wrong polarity, but ductor is called diode A will conduct. Current leaves terminal 2, and LOAD RESISTORS then follows the same path as the positive half -cycle Some electronic equipment requires two or more Cl has just begun to discharge; the rising current. values of DC voltage for proper operation. These volt- restores the charge to full voltage. The re- current ages can be selected from the load resistor. of the current flows through R1 in the same mainder Suppose that the DC requirements of the rest of the the positive half -cycle current did. At direction as equipment were +200, +100, and +50 volts. A power 4, only diode D has the correct voltage polarity terminal supply can be selected or designed to produce a cur- Current flows through diode D to terminal to conduct. rent large enough to cause a drop of at least 175 volts 3 and the AC source. across R1. QUESTIONS 011. A (an) rectifier provides better fil- THE LOAD RESISTOR CAN SUPPLY tering action than a (full -wave, half -wave). DIFFERENT VOLTAGES Q12. In the diagram at the top of this page, current C beat terminal 1 will not flow through diode +200V cause current will not pass from to

1 TO DC 013. Current at terminal 4 will not go through diode VOLTAGE +100V C because its cathode is and its SOURCE plate is +50V

ANSWERS COMMON All. A full -wave rectifier provides better filtering than a half -wave. terminal 1 will not pass through diode Al2. Current at Either three series resistors of the correct values, C because current will not pass from plate to or a bleeder resistor capable of being tapped at the cathode. desired values, can be used. The drawing above shows A13. at terminal 4 will not go through diode Current a bleeder resistor symbol. C because its cathode is positive and its plate By making connections to terminals A and Common, is negative. 200 volts will be available. To obtain 100 volts, the half IMPROVING THE POWER SUPPLY bleeder is tapped at the halfway point to obtain For 50 volts, the resistance is tapped The DC ripple remaining on the full -wave rectifier the total voltage. the 100 -volt point and the common output may be smooth enough voltage for some equip- halfway between ment but not for others. The output can be made still terminal. improving the filtering action. smoother by QUESTIONS another capacitor in parallel with the load By adding 014. A capacitor opposes changes in current by stor- and another current- Imiting resistor in series resistor ing a on its plates. path, the filter network can reduce with the discharge 015. A coil opposes a change in current by develop- the ripple. more of ing a changing Assume in the above figure that the bleeder FILTER 016. A CAPACITOR -RESISTOR - CAPACITOR must be replaced with three separate resistors. If you know that 0.1 amp flows through the bleeder to produce a total of 200 volts, what is the value of R R2, and R5? ANSWERS A14. A capacitor opposes changes in current by stor- ing a charge on its plates. A15. A coil opposes a change in current by developing a changing magnetic field. A16. R1 = 1,000 ohms; R2 = 500 ohms; R3 = 500 ohms. If 0.1 amp developed 200 volts across the Both capacitors are charged and recharged by the total resistance, the bleeder would have to be positive and negative currents switched into the filter 2,000 ohms. (R = E /I). There would have to be by the bridge. Both capacitors discharge together 1,000 ohms on either side of the 100 -volt tap, B. load resistor R1 as Cl did previously. R2 aids through And the two resistors from B to Common must be by limiting the flow of current through the filter. 500 ohms each. Further improvement to the filtering action can be an iron -core coil called a made by replacing R2 with WHAT YOU HAVE LEARNED choke. Such a coil is wound on a bar of iron. The re- 1. Solid -state diodes allow current to flow in one di- a coil (inductor) to AC is, as you recall, one action of conditions of proper polarity because in current. Magnetic fields, rein- rection under of opposing changes (Continued on page 94) forced by the iron core, smooth out the ripple by pre-

ELEMENTARY ELECTRONICS /March -April 1979 82 LITERATURE LIBRARY 381. Fordham Radio's handy catalog covers test 320. Edmund Scientific's new catalog contains over 356. Now you can get the "Break- through Book" instruments, tools, parts, home and car audio prod- 4500 products that embrace many sciences and with its 105 innovations in breadboarding and test- ucts, scanners and lots more. your Get free copy fields. ing. Continental Specialties. The break -through is today! , 321. Cornell Electronics' "Imperial Thrift Tag Sale" twofold -products and price! 373. 48 -page "Electronic Things and Ideas Book" Catalog features TV and radio tubes. You can also 359. Electronics Book Club has literature on how to from ETCO has the gadgets and goodies not sound find almost anything in electronics. get up to 3 electronics books at $58.70) in stores and elsewhere. (retailing 322. Radio Shack's 1979 catalog colorfully illus- for only 99 cents each ... plus a sample Club News 382. Buys by the dozens in Long's Electronics super trates their complete range of kit and wired prod- package. "Ham Radio Buyer's Guide." Good reading if ucts for electronics enthusiasts ham, you're in -CB, SWL, 362. B&F Enterprises' Truckload Sale catalog of- the market for a complete station or spare hi -fi, experimenter kits, batteries, fuses. tools, tubes, wire, fers 10% off all merchandise: (military or indus- cable, etc. trial surplus) speaker kits, TV games, computer 383. If you're a radio communicator, either ham, 323. Lafayette Radio's 1979 catalog offers almost terminals, tools, TV components, lenses, and more. SWL, scanner buff or CBer, want a you'll copy of everything in hi -fi, CB, ham and many electronic 364. If you're a component buyer or specifier, you'll Harrison Radio's "Communications Catalog 1979." parts. A product index will help you find anything want this catalog of surplus bargains: industrial, Just what the shack book shelf needs. from auto equipment accessories to wire wrapping military, and commercial electronic parts, all from 372. Just what the experimenter needs cal be tools. Allied Action. found in Olson's bargain flyer- parts, assemblies, 327. Avanti's new brochure compares the quality 365. Electronic Supermarket has a new catalog of semiconductors, components, and more. Even more difference between an Avanti Racer 27 base loaded almost everything in the field -transformers, semi- interesting are the prices. mobilie antenna and a typical imported base loaded conductors, tv parts, stereos, speakers, P.C. boards, phones, wire and cable, tools, motors. 384. Looking for precision test instruments? Then antenna. 366. How a hybrid 13 you want B&K- PRECISION's BK -79 catalog on 328. If you are into audio, ham radio, project build- about -watt audio module for $8.88? Or scopes, multimeters, freq. counters and other test ing, telephones, CB or any electronics hobby you'll ultrasonic transducer for $1.49? You instruments find these and other exotic parts and products for CB, radio and TV repair. want McGee's latest catalog of parts and gadgets. Hard aplenty in Poly Paks flyer. Get your copy now! 301. Get into the swing of microcomputer and to find parts fill each page, so get a copy of the 371. Your microprocessor technology with CREI's new Pro- catalog from McGee today! computer system needn't cost a fortune. gram 680. New 56 Southwest Technical Products offers their 6800 page catalog describes all pro- 329. Semiconductor Supermart is a new 1979 cata- grams of computer complete at $395 with features that cost electronics advancement. log listing project builders' parts, popular CB gear, you extra with many other systems. Peripheral bar- 302. Big catalogs are coming back. Burstein- Apple- and test equipment. It features semiconductors - all from gains are included here. bee will send you theirs. It's a parts bonanza every Circuit Specialists. 374. Radatron's Catalog 1006 lists many projects experimenter would want to see. Latest catalog is 332. If you want courses in assembling your own from a self- contained portable lab station for an over 200 pages. TV kits, National Schools has 10 from which to electricity -electronics course to many texts, choose. There is a plan for GIs. lab 303. Graymark's catalog reveals a host of products manuals, and applied activities. and kits every experimenter would like to have. 333. Get the new free catalog from Howard W. 375. Compucolor Corp. has a personal computer Unusual binary clock is a winner. A must catalog Sams. It describes 100's of books for hobbyists system with an 8 -color integral display, a type- for the beginner. and technicians -books on projects, basic elec- writer -like keyboard, a tronics and related subjects. and mass storage device. 305. A new 4 -page directional beam CB antenna Programs are ideal for checkbook and income tax brochure is available from Shakespeare. Gives 335. The latest edition of the TAB BOOKS catalog figuring. complete specs and polarization describes over 450 books on CB, electronics, radiation patterns broad- 376. Sparkomatic offers all the car for their new fiberglass casting, do -it- yourself, hobby, sounds for the directional antennas. radio, TV, hi -fi, and "travelin' man " -speakers, amplification CB and TV servicing. systems, 306. Antenna Specialists has a new 32 -page CE and radios, speaker accessories along with CB anten- 338. "Break Break," a monitor antenna catalog, a new amateur antenna booklet which came into nas, all presented in 4 -color pics with descriptions. existence at the request of hundreds catalog, and a complete accessory catalog. of CBers, con- 377. We can't enumerate all the products in John tains real life stories of incidents taking place on Meshna, Jr.'s catalog of surplus electronic parts: 307. Atlas calls their 210X and 215X the perfect America's highways am- and byways. Compiled by the power supplies; computer keyboards; kits ateur mobile rigs. Their 6 -page, full -color Shakespeare for detailed Company, it is available on a first alarms, clocks, speakers; and more. spec sheet tells all.- Yours for the asking. come, first serve basis. 378. Delta Electronics is a complete parts source 330. There are nearly 400 electronics kits in Heath's 345. For CBers from Hy-Gain Electronics Corp. there for electronics experimenters. Discrete parts, mod- is a -page, 4 new catalog. Virtually every do- it- yourself interest 50 -color catalog (base, mobile and ules, boards, subassemblies and complete gadgets. is included marine transceivers, antennas, and accessories). -TV, radios, stereo and 4- channel, hi -fi, Colorful literature Get Delta's 120 -page catalog today. hobby illustrating two models of moni- computers, etc. tor- scanners is also available. 379. There's everything in the area of musical 308.Your guide to equipment for radio communi- 354. A government FCC License can help you synthesizers for drums, strings, other instruments and full orchestras, cation is an informative product booklet offered by qualify for a career in electronics. Send for Infor- as well as audio gear, video display modules, R. L. Drake Co. Hams and SWLers alike should mation from Cleveland Institute of Electronics. and a computer in PAIA Elec- scan this 20 tronics' catalog. -page shopper's guide. 355. New for CBers from Anixter -Mark is a colorful 380. If your projects Transistors 4 -page call for and FETS, 310. New and used personal computer mach,nes, brochure detailing their line of base station linear and and digital ICs, or special solid -state parts, and peripherals you never dreamed existed, or mobile antennas, including 6 models of the then look into famous Adva Electronics' mini- catalog for were available are in the Newman Computer Mark Heliwhip. rock bottom prices. Exchange catalog. Get yours today. 311. Midland Communications' line of base, mobile ELEMENTARY and hand-held CB equipment, marine transceivers, ELECTRONICS March /April 1979 scanning monitors, plus a Box 1849, sampling of accessories G.P.O. Void After August 16, 1979 are covered in a colorful 18 -page brochure. New York, NY 10001 312. E.D.I. (Electronic Distributors, Inc.) carries Please arrange to have the literature whose everything from semi-conductors to transformer/ numbers I have circled below sent to me as soon as possible. I am enclosing 500 relays to video cameras. In prices ranging from 190 for each group of 10 to cover handling. (No stamps, please.) Allow 4 -6 to $500, products appear from over 125 electronic weeks for delivery. parts manufacturers. The catalog is updated 3 times 301 302 a year. 303 305 306 307 308 310 311 312 313 314 316 318 313. Get all the facts on Progressive Edu -Kits Home 320 321 322 323 327 328 329 330 332 333 Radio Course. Build 20 radios and electronic cir- 335 338 345 354 355 356 359 362 364 cuits; parts, tools, and instructions included. 365 366 371 372 373 374 375 376 377 378 379 380 381 382 314. Cover the Ham bands from 80 to 10- meters with 383 one classy rig -Swan Electronics' 100 -W 100 MX 384 mobile transceiver. Get the details direct from Swan, 300 CI Enter my subscription to ELEMENTARY ELECTRONICS for 9 issues at $5.97. Check enclosed. 316. Get the Hustler brochure illustrating their com- Add $1.00 for Canada and all other countries. H9C008 plete line of CB and monitor radio antennas. 318. GC Electronics offers an "Electronic Chemical NAME (print clearly) Handbook" for engineers and technicians. It is a "problem solver" with detailed descriptions, uses ADDRESS and applications of 160 chemicals compiled for electronic production and packaging. They are used CITY STATE for all types of electronic equipment. ZIP

ELEMENTARY ELECTRONICS /March -April 1979 83 and unique spark within King of the Hobbyists parent inability to achieve a decent some great gross margin. "Okay," Tandy said, "you him." page 58) (Continued from guys buy out my position in Tandy and And in a moving eulogy in the New I'll take on Radio Shack myself-with- York Post, financial writer Irwin Lain - stood the sort of buyer commonly out you." To its ultimate credit, the off put it all into perspective: "Charles Wall known as a hobbyist. How to cater to Board capitulated. Charles Tandy came Tandy used to swing through his needs without losing money. How to Boston in April, 1963, and took Street with a warmth that set him apart to attract him by store location, service, charge personally. He had no team. from most businessmen who like to price and advertising. Especially adver- He'd create a team out of the employ- fashion themselves in granite." He'd tell tising. "If you want to catch a mouse ees who would be left after his first anyone who listened about "how many you've got to make a noise like a clean sweep of the overhead. Radio Shacks he was opening this year, cheese," was one of the dandiest Tandy - "Don't fire anybody," was his first store sales, margins, and advertising the isms on record. instruction, "without first offering them outlays. Late in the night, though, All through 1961 and 1962, Tandy a job as Manager of a new store." That man from Texas would sit quietly and fretted' over his urge to get into a busi- there were no new stores in the works explain how Tandy (Radio Shack) had ness with a bigger horizon than leather - was irrelevant to Radio Shack's new filled the vacuum as a retailer of con- craft. He'd already mastered the latter, leader. There would be stores -soon. sumer electronic products. Before long, garnering a reputed 80 to 90 percent One of the company's top chieftans was you'd realize that here was one of the of the market. Somehow he arrived at offered "the entire city of Philadelphia." true marketing giants of our age." the conclusion that electronics was right At that time there were zero stores in Radio Shack's 20,000 employees, and up his alley; exciting merchandise, con- or planned for Philadelphia. But 15 25,000,000 customers -including those stant growth, scads of hobbyists, great years later there would be 80! to whom electronics is a vocation or an tie -ins to leisure time and education. The Salesman. "Charles Tandy Keeps avocation -might be surprised that a He started knocking on doors, but as on Selling," was the title of a recent man who didn't know a resistor from a to the a buyer, not as a salesman. After mak- Fortune article about the chairman. transistor could be so important ing the rounds of all the consumer elec- But Chancellor J. M. Moudy of Texas recent past and present of electronics tronics catalog houses-not once, but Christian University observed that for the masses. But to Charles Tandy, several times -he finally consummated a "Charles was more than the sum of his who explained and practiced his busi- deal with Radio Shack and its major family and TCU and Harvard and ness theory in the full glare of the pub- lending institutions. Navy experiences. More came from the lic spotlight, "they'll say it was easy .. . Then there was the matter of the man than went into him for he had after we've done it." Tandy Corporation Board of Directors. It vetoed the deal on the basis of The Shack's financial condition and its ap- are missing for one of your radios. He Antique Radio Corner has no 200As, 201As, 199s, WD -11s, (Continued from page 54) or WD -12s, but he does have most any other number you might need. Write for his tube list, with prices to: Stein- ®CATCHAPULSE II hum, etc., your set will play. metz Electronics, Dept. ARP, 7519 It is quite expensive to buy all the Maplewood Ave., Hammond, IN ;LOGIC PROBE batteries necessary to make your radios 46324. x-10 Nsec SPEED AT play. Most collectors have one or more Several years ago, I bought a radio and tube collection from the widow of 4 to 1511 LEVELS AC operated power supplies for their old radios. The ideal power supply a deceased owner of 6 radio parts Compatible with DTL, TTL, stores in the Washington, DC area. CMOS, MOS, and Microproces should furnish the necessary "A" volt- 'l sors using a 4 to 15V power age for the filaments at a current ade- Among the tubes were two spherical supply. Thresholds automatically quate for a 6 tube radio. It should glass bulb types. One of the tubes had programmed. Automatic resetting base for the memory. No adjustment required. supply up to 6 different "B" voltages to a double contact bayonet Visual indication of logic levels. using cover all types of sets, and it should filament leads, similar to an automobile LEDs to show high, low, bad level or bulb. The exhaust tip was broken, open circuit logic and pulses. Highly supply several different "C" minus volt- lamp sophisticated, shirt pocket portable ages for sets that require them. There but the filament was still OK. The tube healer (protective tip cap and removable was a duo -diode; it had two plates and nownes coil cords. Eliminates need for heavy are several manufacturrs of power sup- welcome© test equipment. A definite savings plies for the old battery radios. The a filament. I was never able to find out 0fl in time and money for engineer a definitely who made it, but an educated and technician one I use is manufactured by radio a guess was that it was a Fleming valve. 10 Nsec pulse response collector who knows exactly what ONLY Stu Recently I sent it to Sam Diaz, Pine covi Open circuit detection power supply should do. I've found well Grove Mills, PA 16868 and he pumped $44 95 Replaceable tip b cord this power supply to be rugged, built, conservatively rated and hum it, de- gassed it and resealed it. I am High input impedance building some type stretching free. I have operated several sets from looking forward to Pulse tube. Multi- family a Philco portable to a Silvertone con- of radio receiver with that sole radio. It is reasonable in price and Sam Diaz is a glass blower, and has contains solid state rectifiers and volt- the pumps and other necessary equip- +, SPECIAL. PAK -Il 551.95 age regulators. You can get a brochure ment to repair receiving and small Includes a- standard coiled cord, coiled cord tubes of the filament typt. with micro hooks, adapter for using CATCH - containing complete information about transmitting A -PULSE on logic families whose power this power supply by writing to: Gary He tells me that he is making replicas supply is 15V to 25V. Shipping add $ 2 00 per which were probe. Schneider, 6848 Commonwealth Blvd., of some 1917 -model tubes Parma Heights, Ohio 44130. You will originated in France by the Methal .LVELECTRONICS be glad you did. Co. If you have any rare tubes that CA 92119 Box 19299, San Diego I recently ran across another sup- need to be restored, I would advise you (714) 447 -1770 plier of old radio and TV tubes who to contact Sam Diaz and ask for help. may be able to supply that tube you Tell him I sent you. CIRCLE 103 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 84 , , .--- na....w,a..-

Percom Floppy Disc tems. And, while the Percom chugs away without errors under humid con- FREE SiITI (Continued from page 68) ditions that knock out our data cassette recorders, at the point where the hu- minor problem that no longer exists. midity starts to separate wallpaper CATALOG As with all minidisk drives we have from the wall, the Percom has failed seen and used, a small red lamp on the to Ioad once or twice. But normally, Audio-Computers front of the drive indicates when it's air circulation generated by the inter- Instruments operating. To extend life of the drive, nal motor flushes out the drive and we Percom has built in a timing circuit have never experienced a third failure. Kits & Assembled that turns off the drive motor after Summing Up. Overall, from virtually 3 seconds of non -use. every viewpoint, the Percom LFD -400 The miniDOS has its own error mes- is an excellent value for the personal sages independent of BASIC's errors. For computer user or hobbyist with an example, if you get the special disc SWTP 6800 computer. With it, you error symbol and a "O you have been actually get all the advantages and told you're trying to run the system services of a "full blown computer," without a disk, or with the disk gate and it meets our requirements of rea- open. If the error is a "3 ", you've tried sonable price, speed, and convenience. to load a blank sector. There are five All the possible uses of the LFD -400 disk system errors, ranging from the system are too great to cover in an disk missing-gate open to read error, article, so we suggest you write for meaning the sector was tried nine times additional information to Percom Data without success. Company, 318 Barnes, Garland, Texas High humidity is the curse of vir- 75042, or circle number 63 on reader tually all media computer storage sys- service coupon. the cycle can be repeated. Cyclops To generate the "Close Encounters" (Continued from page 39) music sound, throw S1 to the OFF or open position. When you apply power to the circuit, Cyclops will generate the Southwest Technical Products Corporation so that the cathode side is connected whooping sound for 30 seconds, and 219 W. RHAPSODY to the base of Q1. Do not proceed then will switch to the "Close Encount- SAN ANTONIO, TEXAS 78216 further until the voltage at pin 13 of ers" music for another 30 seconds as ICI is within the range of +3.5 to IC2 and IC3 switch on and off. This CIRCLE 39 ON READER SERVICE COUPON 4.5 volts. sequence will repeat indefinitely. If you Put Professional Knowledge and a Measure the voltage at pins 2, 5, 6, wish to generate only the "Close En- 7, 8, 9, 10, and 12 of ICI. This voltage counters" sound, remove IC2. COLLEGE DEGREE should be zero. Measure the voltage at Applications. Cyclops can be used in in your Electronics Career through pin 8 of IC2 and IC3. This voltage many applications depending upon the should be about +12 volts. Measure connections between terminals A, B, the voltage at pin 1 of IC2 and IC3. C, and D of the circuit and whether This voltage should be zero. or not the timing circuitry of IC2 and Disconnect the power from the cir- IC3 is included in the assembly. cuit. Very carefully insert the integrat- For a short timing interval, such as ed circuits in their sockets, paying would be needed for an automatic strict attention to the proper orienta- doorbell or light operated rifle range, tion for pin 1 as shown in the cam- the circuit shown on the right of the . ponent layout. Pin 1 of the Optolinear dotted line of the schematic can be de- Earn Your IC is indicated by a red dot or "U "- leted. Si should be set to the ON or DEGREE shaped indentation molded into the top closed position and terminals A and by correspondence, while continuing of the plastic case at one end. B of the printed circuit board your should present job. No commuting to class. Study Be sure the speaker is properly con- be connected together. For these ap- at your own pace. Learn from complete and nected to the circuit between the +12 plications, as well as using Cyclops for explicit lesson materials, with additional volt bus and the collector of Q5. Set a musical automobile horn, you may assistance from our home -study instructors. S1 to the ON or closed position. Ad- want to slow the whooping rate for a Advance as fast as you wish, but take all the just the volume control about halfway more pleasant sound. This can be easi- time you need to master each topic. Profit and apply 12 volts of power to the ly accomplished by changing the value from, and enjoy, the advantages of directed circuit, observing correct polarity. You of C4 to 10 microfarads or more. but self-paced home study. should hear the whooping sound gen- The circuit can be used as an inru- The Grantham electronics degree pro- erated by the circuit, and the LED sion alarm with a long timing interval gram begins with basics, leads first to the should light. A.S.E.T. degree, and then to the B.S.E.T. The LED should remain by building the . complete circuit as degree. Our free bulletin gives lit for about 30 seconds, and shown complete when it in the schematic. Set S1 to the details of the program itself, the degrees goes out, the sound should continue for ON or closed position and short ter- awarded, the requirements for each degree, a few seconds more. Once the sound minals A and B. and how to enroll. Write for Bulletin G-79, stops, you can wave your hand over A combination whooping sound and ICI and cause the sound to start again. "Close Encounters" music can be pro- Grantham College of Engineering 2500 S. Lacienega Bhd. This time the circuit will reset itself duced by building the entire circuit and P. 0. Box 35499 after a few seconds, since IC2 is being setting S1 to the OFF or open position. Los Angeles, CA 90035 inhibited by the timed cycle of IC3. Delete the timing circuit for continu- After another 30 seconds has passed, ous "Close Encounters" music. Worldwide Career Training ihru Home Snide CIRCLE 10 4 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 85 Those Mayan outposts make Merida Tropical DX the last stop on the Mayan Connection. projection (Continued from page 41) Broadcasting from a second -story walk- up a block off the downtown square in television Merida is the only shortwave station in Toward the end of what historians Yucatan, "Young Panther Radio," Pan - call the Mayan "Classic Era," around tera Juvenil, on 6105 kHz, 49 meter 900 A.D., they all inexplicably migrated band. "Su Pantera" Radio is a far cry northward, up the Yucatan Peninsula. from the rural stuff your ears have been So to round out this guide to the drinking in elsewhere on the Mayan Mayan Connection, we'll do likewise. Connection! The programming, starting Onward, to Merida, at the very peak of around 1100 GMT, is young, jazzy and Yucatan! modern! About that morning show, Merida, at the edge of the "thumb" manager Mario Gonzales Peraza says, of the Yucatan (which is actually Mex- "In 'The Early Morning Riser' show, ico) is a pastel and chatering little town we transmit some of the best music and of well -manicured green parks, horse - send greetings to the 'radio sentries'. drawn carriages and an epic past. At who phone us." EQM only pumps out PROJECTION one time, Merida was a boom town as 250 watts, but Peraza says they get re- TV HARDWARE the center of a hemp industry, thanks ports from Europe, S. America and AND COMPONENTS to the sisal plant which flourishes on Asia ... so why not you? Every so Whether it's simply our brilliant lens, our hoods, bases, cabinets or screens the Yucatan scrub land. That has died often, they really pound through in ...to a complete projection system... industry is the the morning hours. QSLs? Of course! you deserve the best. So, write to the down now, but a growing largest supply house and manufacturer tourist trade Merida has, thanks to the So there you have the Maya Connec- of quality parts for Projectapix's big catalog on parts, components, acces- famous pyramid ruins of Chichen Itza tion. And "maya" your listening be sories, screens and stands. Everything muy bueno! shipped is guaranteed or your money and Uxmal, both nearby. refunded. Can we promise any more? MFR. & DLR. INQUIRIES INVITED thing which must be kept in mind Send $1 For Complete 8-Page Booklet At the Speed of Sound when DX'ing the aeronautical channels On Projection Tv Construction Plans. (Continued from page 51) is that it is a federal offense, punish- able by a fine of $10,000 and a jail pound," and even "Ouch!" Of course, term of one year, to reveal the contents 300 WEST 53 STREET these humorous calls do have the seri- of any transmissions you may intercept NEW YORK. N.Y. 10019 ous purpose of attempting to confuse on the aeronautical channels (or any except TELEPHONES: (212) 765 -7869 the enemy in the event of actual con- other non -broadcast stations, flict. list of SAC frequencies will amateurs, for that matter). You may CIRCLE 38 ON READER SERVICE COUPON Our indicate where to tune for such tactical report the time, date,, frequency, and stations. call signs of other stations contacted Sometimes, on Air Force channels, in your reports for a QSL card, but you will hear the word "foxtrot" fol- you may not quote any of the message N WIFOR McGEE'S lowed by coded groups. These are itself. Even if you escape prosecution any of the received trans- BIG SPEAKER CATALOG coded instructions to aircraft aloft. for quoting You may also hear the term "skyking" mission, the station heard will likely IN 1001 BARGAINS used, which is a general term for any refuse a QSL if you quote any of what in report! SPEAKERS- PARTS -TUBES - HIGH FIDELITY SAC aircraft. you heard your reception COMPONENTS-RECORD CHANGERS Alert SWLs should keep a check on The one exception to this rule is a Tape Kits -Everything in Electronics Recorders- the frequencies used by Andrews AFB VOLMET transmission, which is con- 1901 McGee Street, Kansas City, Missouri 64108 whenever the President or Vice- Presi- sidered as a broadcast for general re- dent is scheduled to leave or arrive in ception. Washington. Both Air Force One and As mentioned earlier, the SPEEDX YOUR PHONE Two communicate through Andrews, Utility Guide is a big help in deter- and some SWLs have even been lucky mining frequencies of aeronautical sta- CALLS ON TAPE tions and addresses for QSLs. Another Record incoming and outgoing calls automatically enough to hear telephone calls placed to your valuable reference is the Confidential with this all solid state unit connected = through Andrews AFB by members of telephone jack and tape recorder. Starts record- li r Frequency List, available from Gilfer ing when phone is lifted. Stops when you hang the Presidential party!

a permanent record. Easily installed. Associates, Box 239, Park Ridge, NJ up, making Y Wrapping It Up. One very important monthly phone charges. FCC APPROVED No extra ``%.- 07656. 2 -1/4 x , -3/4 x 3.4 $24.50* Commonly Heard VOLMET Broadcasts It also pays to join an SWL club VOICE r ' ACTIVATED which features coverage of aeronau- of operation are given as minutes VOX CONTROL Times tical DX. SPEEDX (Society to Pre- x x SWITCH past each hour. 2 -1/4 3/4 yr l, serve the Engrossing Enjoyment of Self contained solid state. Excellent adjust - ?. i Atlantic Area broadcasts on 3001, 5652, DXing) has the largest stich coverage. able sensitivity. Recorder activated by voices or other sounds. Uses recorder mike or 8869, 13272 kHz. Good coverage is also offered by the $24.95' remote mike. Great for home. business, etc. New York: 00 -20 and 30 -50 American Shortwave Listeners Club, FCC APPROVED AMAZING ELECTRONIC Gander, Newfoundland: 20 -30 and 50 -60 16182 Ballad Lane, Huntington Beach, MIKE 5519, MICRO MINI Pacific Area broadcasts on 2980, Calif., 92649. Both clubs will send Among world's smallest, solid state, self contained 8903, 13344 kHz. WIRELESS MIKE. Mercury Bat. furn. Picks up most sample bulletins for $1.00. - sounds and transmits without wires up to 300 ft. thru Oakland, California: 05 -10 and 35 -40 FM Radio. Tuneable. Use as mike, ampi., alarm & alert Tokyo, Japan: 10 -15 and 40 -45 see, there's no need to system, baby sitter, hot line, etc. ('Plus $1.00 Pstg. & As you can add Hong Kong: 15 -20 and 45 -50 -- Hdlg.) Money back guarantee. California residents restrict your DX'ing to earth -bound tax. Free data. Mail order. Visa, M /C, Cod's o.k. Quantity Honolulu, Hawaii: 20 -25 and 50 -55 AMC Sales, Depf.24, 9335 Lubec stations. The sky can be the limit for discount available. Alaska: 25 -30 and 55 -60 $18.95x St., Box 928, Downey, Calif. 90241 Phone 1213) 869-8519 Anchorage, 2.,/4. a/4 ., /a" SWLing! ELECTRONICS /March -April 1979 86 ELEMENTARY ..n....y .. 9i.r+.. .dr11111-..

Permanent Memory. Though the Regency Scanner . Flexible production power switch turns the receiver off in I.C. dispenser (Continued Iront page 49) the usual sense (all lights off, etc.), Expandable to power is still 40 stations maintained to the channel Safe for CMOS/ hind each symbol is a mechanical memories so the programmed frequen- MOS devices switch. Pushing on the plastic directly cies are remembered. In the event the ..300 " -.600" over the symbol causes the associiated AC mains center spacing (powerline) should fail the Holds Tubes firmly switch to be activated. memory programming would crash be- One keyboard is labled 1 through cause there would be no power what- 01P- speosen'" 16, and these are the channel selectors. soever to keep them alive. To handle An LED directly adjacent to each num- this type of emergency there is a com- ber indicates whether channel is turned partment on the rear apron for a 9- The Complete on or off, or is active (on for active). volt "transistor radio" battery that A second keyboard is labled 0 serves to keep the memories alive even through 9, manual, scan, priority, delay, if the main power is removed. I.C. Handling and enter. It is used to select the The Digital Flight Scan is housed in manual or scan mode, and for pro- an attractive wood cabinet 121/2 -in. gramming the frequency System limits of a wide by 33/4 -in. high by 93/4 -in. deep. search, or the frequency to be pro- Weight is 9 lbs. The scanner can be grammed into a channel. The delay powered either by 120 VAC, or 11.5 to little changes the "normal" scan delay from 15 VDC. Both the AC and DC power 0.2 to approximately Oipper 2- seconds, hold- cords plug in. In addition to the AC ing Fastest manual DIP the scan through the pause in a and DC. power connectors, the rear inserter on market two -way contact. apron has the jacks for the antenna and a 5 models .300 " -.600" Priority refers to channel 1 and any remote speaker. other channel the center spacing user selects as the A telescopic antenna that plugs into Only tool to work with second priority channel. Whenever the antenna jack is supplied with the sockets -aligns leads either priority channel alone is pro- scanner. The 9 -volt battery required for when inserting I.C.'s into grammed on and the scanner is stopped the non -volatile memory is optional and zero force sockets Free on an active channel the priority chan- is supplied by the user. Safe for CMOS /MOS Catalog nel will be sampled approximately once Inserts with no stress on lead seals a second for activity, and the scanner Overall Performance. Rattling off a will switch to the priority channel the stream of specifications is useless, as TECHNI-TOOL inc. instant activity is perceived. we've well learned from testing VHF Apollo Road, Plymouth Meeting, PA 19462 (215) 825 -4990 Tlx. 83 -4763 When both priority channels are pro- receivers; for under crowded band con- grammed on and the scanner is stopped ditions what appears good in print CIRCLE 101 ON READER SERVICE COUPON on another active channel the priority might not work out so well when actu- channels will be sampled ally monitoring. In the area sensitiv- Big opportunities. Big prof- alternately of its. Earn quickly. Full or for activity. Regardless what channel ity the Digital Flight Scan is rated at part time. Learn at home, it's easy. Do the scanner stops on, even 1 uV and that's just about what we real jobs: All the second Tools- Materials Sup- priority channel, the scanner will al- measured using a signal generator. In plied. Accredited member NHSC. Lic. State of ways switch to priority channel 1 if it comparison to other high quality flight NJ- receivers Appd. for Vet Send name, becomes active. When the scanner stops the sensitivity appeared about and address for FREE book: on either the Lac smit Ilse Institute, Dept 1472 -039 priority channel the frequency same. Div. Technical Home Study Schools, Little Falls, N.J. 07424 readout will display the frequency fol- As for selectivity. We ran across no lowed by a letter "P." condition where there was splash from one utilized frequency to another, so tS ELECTRONIC Searching. A third keyboard has but PROflt ASSEMBLY BUSINESS two switches, labled search program, we must assume the 55 dB adjacent channel rejecion Start home, spare time. Investment, knowledge or and search scan. Search program is specification is ade- experience unnecessary. BIG DEMAND assembling quate for the Aircraft Band. electronic devices. Sales handled by used when the user enters the upper professionals. Unusual business opportunity. Overall sound and lower search frequency limits. quality is very good. FIFE: GgleN illustrated Marshal When there is distortion it's the fault amp BARTA, Box 248m ION Search scan starts the search. Once the Walnut Creek, Calif. 94597 search finds an active frequency it locks of the transmitting station, either ground or to that frequency, which is displayed airborne. When the transmitting sta- on the readout, until the frequency goes tion's modulation is clean and crisp it is received "dead," or the search is once again re- the same way by the ACT -T- sumed by pressing search scan. A 720A. FREE "found" frequency can be entered into Summing Up. Overall, the Regency SHORTWAVE CATALOG a channel by simply pressing the enter Digital Flight Scan is an admirable per- AC; /LFER switch followed by the channel selector former. Of noteworthy merit is the fact number. You can switch to manual, or that though computer controlled, the scan, or search by simply pressing the overall operaion isn't so complicated it appropriate keyboard entry. The only takes a read -thru of the instruction limitation on search is that the range is manual anytime you want to change are split into two increments: From 108 to ,functions or programming. 118 MHz a 50 kHz increment is util- The Regency ACT- T -720A Digital NEWEST EDITION -ONE -STOP SHOPPING FOR SWLS ized; from 118 to 135.975 the incre- Flight Scan complete with AC and DC RECEIVERS special DX mods ANTENNAS PRESELECTORS TUNERS ment is 25 kHz. Any increment is power cords and CALIBRATORS that telescopic antenna is CLOCKS HEADPHONES BOOKS LOGS keyed in that does not match either priced at $349.00. For additional infor- specified range will be automatically mation circle No. 40 on the Reader's GILFER SHORTWAVE Dept.EE..3 , corrected by the computer. Service Coupon. U Box 239, Park Ridge NJ 07656 ELEMENTARY ELECTRONICS /March -April 1979 87 at more than one location. Only a formerly held the old switch in place. Vigilite Timer screwdriver is needed for the installa- Then add a cover ( "flash ") plate and (Continued from page 52) tion. a small spacer to keep the plate the First, turn power off the branch cir- proper distance from the Vigilite. Final- back The only time you will ever need to cuit at your fuse panel or circuit break- ly peel protective paper from the and the go through the program -selection pro- er board, and check the existing wall of the outer front panel press flash All that re- cedure is when you have a power fail- switch to be sure you flicked the right panel onto the plate. to branch ure or when a burned -out bulb must circuit breaker. Remove the wall plate mains is to restore power the switch to be replaced. When changing bulbs, you and old switch. After pushing the mas- circuit and pull the master The LED dis- push a master switch just above the ter switch at the top of the Vigilite unit power the Vigilite unit. are digital display to turn all power off the to its "Off" position, connect the two play comes on to show that you lighting fixture, for safety reasons. wires in the wall switch box to the two ready to go through the program- selec- Installation. The Vigilite system in- Vigilite wires using wire nuts. Be sure tion procedure and start using this stalls in minutes as easily as a dimmer that no bare wire is visible outside of space -age crook -foiler. switch. Just remember that it must be either wire connector. used only on a single- switch branch Mount the Vigilite unit into the Kathi's Carousel circuit, not on a circuit having switches switch box using the same screws that (Continued from page 69)

vague relative value which might rep resent a very large change, or a very A SPECIAL OFFER variation. (An early model of the MAGAZINE small TO THE READERS OF THIS Thomas J. that I saw had a relative reading S- meter. ) One feature I find has no value is instant Channel 9 selection. Simply press a button and both the receiver and transmitter instantly shift to channel 9, the regular LED channel indicator blanks out, and a small LED indicates that the instant channel 9 switch of Fiction in Masterpieces is on. As I have often said, my travels I have never gotten a single for only 54.95 response to an emergency call on channel 9. As far as I'm concerned channel By special arrangement wtih DALE BOOKS, we are able to offer you this 9 emergency monitoring is a myth. unprecedented opportunity to purchase eleven Masterpieces of Fiction for From the rock -bound coast of Maine only $4.95. The titles included are: to the sunny skies of California, I call AUTHOR TITLE for assistance on channel 19, or what- is used as the local highway/ Crane, Stephen THE RED BADGE OF COURAGE ever trucker channel. TWO CITIES Dickens, Charles A TALE OF The tone control is no earthshaking Dickens, Charles GREAT EXPECTATIONS feature except for the times when a Doyle, Sir Arthur Conan THE HOUND OF constant background noise -which can't THE BASKERVILLES be suppressed by either the noise blank- Hawthorne, Nathaniel THE SCARLET LETTER er or ANL- starts to grind me down. Melville, Herman BILLY BUDD It's nice to be able to tune down the frequencies, which is the most an- Shelley, Mary FRANKENSTEIN high noying noise component; it's like hav- ISLAND Stevenson, Robert Louis TREASURE ing a third type of noise limiting. Twain, Mark THE ADVENTURES OF Of course, the built in VSWR meter HUCKLEBERRY FINN is a big plus when installing a new Twain, Mark THE ADVENTURES OF antenna or testing the old one. I usu- TOM SAWYER ally keep the meter set so it continu- Wells, H. G. THE TIME MACHINE ously indicates the antenna system VSWR. In the winter, with the salt DALE Classics come in the handy mass market paperback These special used for melting road ice constantly format which has been universally accepted by schools, libraries and away at a bumper mounted an- leading bookstores throughout the country. eating tenna, it happens -once or twice each will be shipped directly from the DALE printer and are in mint All books year -that a connection corrodes or Merely fill out the coupon to insure hours of reading enjoyment condition. opens. The VSWR meter instantly tells of this very unique collection. me something's wrong. Summing Up. Other than the instant TO: DALE BOOKS Classic Editions channel 9 selection, the President 380 Lexington Avenue, New York, N.Y. 10017 E]IA -%9 Thomas J. is a heavyweight in features group of 11 DALE Classics plus $1.55 for I enclose $4.95 for each and performance, particularly in view Postage and Handling. (Total of $6.50 per order). of its modest price. You'd be hard sorry but Credit Orders will not be accepted. We are pressed to find its equal in wall to wall New York State residents add 8% sales tax. modulation and high receiver selectiv- NAME ity for about $160. For additional in- ADDRESS formation circle No. 46 on the readers CITY STATE 7IP service coupon. ELEMENTARY ELECTRONICS /March -April 1979 THE GREAT ELECTRONIC ELEMENTARY THINGS & ELECTRONICS SURPLUS CATALOG! Many SG"!, Unusual Items & Specials not found *elk in stores or catalogs anywhere' aD Circle Reader Service Coupon or write today for exciting Free CatRlo¡ff MAGIC SOUND SWITCH!! SURPLUS BARGAIN. Sensitive crystal mike picks up Sound which HOBBY Is amplified to trigger 4 an SCR switch. Opera- tes on 3 -6 VDC. With schematic. 12 ca.) 9 024SU210. 10/59.95 100f$79.95

.s,wcn s..PVLV 12 VOLT 2 AMP POWER SUPPLY! - 10489.95 VIART Sensational purchase of Eur pean Inventory! 3-4 amp surge. Excellent for CB, car stereo arid 99S general hobby and school Shop applications. Excellent battery Charger. Excellent dealer Item. 024HP233. (2 lb.) DIGI-KEY BUILD A PARABOLIC CORPORATION MICROPHONE! (leudilr Lh"Tr nir Giant 22" diameter plastic parabolic I.G'f RESISTORS rRNSItTOeS CAPACITORS DIODES I.C. SOCKETS L PINS SWITCHES sound reflector. For DON'T FORGET OUR: DISCOUNTS WHEN COMPARING PRICES nook MODULES PTOELrtTRONl6 !sneeOADING L TESTING DEVICES LIRA/TING SUPPLIES construction of long 95 DATA LOOKS MEAT SINKS WIRE .. TOOLS... AND MORE ... WRItE EOR FRIS CATALOG distance mikes and INTEGRATED CIRCUITS sound projectors. ME MA0073 by The "NIBBLER" 'Construction Ideas VISIT NATIONAL A MICROCOMPUTER C Included. (5 lb.) 0Vß SEMICONDUCTOR AT A MICROPRICE! THE "PROGRAMMABLE 024MP233. STOFF! CLOCK MODULE Rush your order with full remittance please. Visa & Maetercharge OK. Allow 15% for UPS & handling. (N.Y. state residents add 7% tax). 24 hour - 7 day telephone order desk. Call when rates are low! ELECTRONICS, EITICIO Dept. 024 NORTH COUNTRY SHOPPING CENTER, PLATTSBURGH, N.Y. 12901

CIRCLE 12 ON READER SERVICE COUPON

YAN.0M1.1.. P01....104 CAPACITOR.

'r, WAIT LUMPS AfnORTMENrS PANMDxKUñaiúi HOBBY WORLD =mh,=r CATALOGUE The new Hobby World Catalogue. 20 pages of factory prime, professional quality equipment (no surplus). Comput- ers, add -on boards, prototype boards, IC's, sockets, resistors, supplies, tools, test equipment, books, and more. Shop your $4.95 buy list. You'll find what you want in Hobby World, and at a solid savings. iq);ve-YILSE SPECIAL 16K MEMORY ADD-ON FOR 8080A I DOUBLE DIGIT DISCOUNTS SAVE VOU EVEN MORE( APPLE OR TRS 80. HANDLING =.=r VOLUME ONLY $98.00 SETZ CHARGES DISCOUNT s Nr o.MafAM MASON( MIMMUqTINTqMS-o.. TERRIFIC PRICE! . 3 23.1.4003 WMM . MR Ill, (specify when ordering) - S I110.EfaMI.M.1HIS% 3 SpAENEI.M . os T>' To order or request free Catalogue .ioeoeau IgO¡p. REIO.MaUr...Inas% write Hobby World 19355 Business Center Drive 06 Northridge, California 91324 TELEPHONE ORDERS DIGI-KEY E. CORPORATION Inside Calif 213- 886 -9200 UREI( CATALOG Qunliry EIPrI " Crrn{NnNnr.N Outside Calif: 800- 423 -5387 PO. MU7 1w. iS.. i IN 54751 miluleer CIRCLE 15 ON READER SERVICE COUPON CIRCLE 25 ON READER ELEMENTARY SERVICE COUPON ELECTRONICS /March -April 1979 89 E ASCII KEYBOARD Bookshelf A '10" WooferSPEAK ONSOLE '5" Midrange SPEAKER '4" Flare Dome Tweeter KIT ' (fluid damped) Big enought to utilize full size speakers: 'Ducted Port 10" woofer, 5" middler & 4" super 'Presence Control tweeter. Big enough to handle 50 'Freq. Resp. 30. 22.000 Hz Watts /channel, small enough to fit your Hz. An advanced system at a modest price. budget. Freq. Resp. 30 to 22,000 Employs presence control for fine Ferro -Fluid Damping. Cabinet size come in fining each system to the acoustic 20x11x9y: "dp. Good things 3 -Line, 5-Line. 11 -Line. wit rotary dial. - a nice extra set for the Please state choice! requirements of the environment. With small packages This Honeywell No. 74100903 -001 reconditioned, capacity it can other room..? Sh. Wt. 60 Lbs. (allow for Sh. Wt. 10 Lbs 3 Line .8C30277 $28.88 a 50 Watts RMS power ASC1 1 encoded microswitch data entry Lbs .5 Line. 8C0549 .$39.88 handle most moderately priced amps on two 30 Lb parcels) format keyboard. Comes with fully pop- Sh. Wt. 10 IT No. 8Y0542 $88.88/Pr. 15 Lbs 11 Line .800550. $49.88 today's market. Sh. Wt. 35 Lbs /ea. Order ulated I.C. boards. Some 100 I.C.'s, 7100 Sh. Wt. TOUCH TONE -PAY STATION Pairs allow for two (2) 35 Lb. pacels. EQUIPTO RACK CABINET & 71400 series, or some are dot matrix ALSO: TELEPHONES 50 WATT SYSTEM .... Order 118Y0478 Size 24x24x68" with I.C.,s, LSI chips TMC 4907 a 4 mhz

. front back List $279.50/pr. Your C ost $179,88/pr. rails on & crystal, a Mostek MK2002, plugs into a MTIN !ETECTgR for mounting equip- wire wrap board of 120 sockets. Also Max amp power 65 MARK VI ment on 19" centers. 2 -large heat sinks, 4- 2N3055 xistors, watts RMS per channel, No doors or sides. List 2- 2N3668, 4- jumper cables with dip plugs 8" passive 10" woofer, Price $185.00 - NEW attached, 30 lamps No. 382 & other stuff. middler, 4" radiator, 5" SURPLUS! Your cost Power required for keyboard +5VDC, This a arm sensor has up to 50' range Cabinet super tweeter. only $50.00 each. Qty to 12VDC regulated. Pin out supplied and fills the protected area with an en- size: 26x15x11 3/4 ". *I Ltd. (Frt Collec for keyboard only. Keyboard in console ergy screen that cannot be seen, felt or it Controls: Continuously 78820469 ... S50.00 is a complete assembly ASCII encoded & heard. Triggers your alarm whenever bur- variable controls for ULTRASONIC is easily removed to fit or use as is. The glar moves through detector field. Moun- tweeter. middler and additional circuitry was used to drive ts on ceiling, wall desk, shelf etc. Op in kit form or REMOTE Available status indicators; Format, program level, tional delay mode, auto-reset. Operates assembled. 1 completely check & display etc. Console size: 19" on 12.5 VDC. A close -out that originally 48 Lbs. Each INFINITE CONTROL Sh. Wt. wd.x16 "dp.x8" hg. rear, front slopes to sold for $179.00 3 Lbs. Qty ITdI for two -48 DESIGN (Pairs -allow SYSTEM 2 3 /4 "hg. Removed from equipment. 8D30336 No 81130376 9.95 Lb. parcels). ()flier This handy control was part of an Ad- Good to excellent condition. Power Supply Kit ...8D0472...$3.88 Kit I IFnn S23888 /l'air miral remote control package for color Sh. Wt. 16 Lbs ... 8W0584 $68.88 Connector Kit ... 8D0504....$1.50 \ > -, nibh d 'rested $368.88 l'air \ TV. The original functions were On- 3 for $188.88... 8W0584 ...$188.88/ POSTAGE: Please add postage, All material is MARK-VII Off, volume, VHF -UHF, and channel I .O.B. Peab 1dy, Ala. No C.O.D.'s please. wTO05 EttsRMS select. Receiver contains 3- relays and one Ilassachusetts Besidentsydd 5% sales tax. SPECIAL! PHONE ORDERS WELCOME! per channel. 12" woofer, 10" four position stepping relay. Also in- Use your Bank Americard, Master Charge passive radiator, 5" middler, cludes a complete data pkg. Control TOUCH or American Express Credit Card! 4" Freq. Resp. operates on 115 VAC. Good for super tweeter. section $10.00 min. on all charge orders. 20 Hz. to 24,000 Hz., Size: toys, garage door openers, TV, stereo SWITCH 42 "x15 "x15 ". The Ultimate! systems or any of those STAR TREK ino- B &F ENTERPRISES Available in kit form or com- vations you would like to make on your ALARM pletely assembled. Sh. Wt 150 own. (Energize or de- energize your NEW packaged system. A super close- 119 Foster Street Lbs. /Pair alarm system remotely. Range 30' out item Protects your valuables; gun's, Peabody, MA. 01960 Mark VII Order No. 8H30377 Transmitter requires AA cell (not CB's, stereo equipment, test equipment, 1617) 531-5774 Kit Form $398.88 /Pair included). Qty ltd etc List Price $22.88 SAVE

. 1 WITH Assembled Form $688.88/Pair Sh. Wt 1 Lb..... 8030372 $25.00 Sh. Wt Lb ßM10474.. $7,88 f2) 3 for $69.88....8C30372... $69.88/3_3 for $22.88....8M10474... $22.88 /3 SURPLUS (Shipped by truck,freight collect to you). 12) READER SERVICE COUPON »` A FREE JUMBO CATALOG! JAM.PACKED WITH SURPLUS ELECTRONIC PARTS GADGETS KITS AND MORE! CIRCLE ) CIRCLE 5 ON READER SERVICE COUPON AMAZING THE NEWEST, MOST HELPFUL, MA1003 MOST INFORMATIVE MAGAZINE DEVICES FOR BACKPACKERS AND HIKERS MODULE THE MAGAZINE FOR HIKERS AND BACixn94 KERS CLOCK Itl((( PHASERS )))llr PPF -1 PHASER PAIN FIELD - This device recently developed and patented in our labs is being evaluated by law enforce- akin9 WITH CASE ... ment agencies for not and crowd control. It is now available but soon will come under the Jurisdiction of weapons and infernal machine control making it unavailable to the public. The device rsto is hand -held and looks a BUCK ROGERS ray gun. It is hazar- Guide ' dous it not used with discretion Lightweight $19.95!! PPF -1 ...... PLANS - $10.00 --r l9G -1 INVISIBLE PAIN FIELD GENERATOR - This amazing. simple hand -held device is about the size of a pack of cigarettes and generates a directional held of moderate to mien- xxower save pain in the lower part of the head up to a range of 50' De- tpr/ ryptoah: vice is simple and economical to make. y!DIREWcaPIIBR IP01 PLANS. $6.00 IPG4K. ALL PARTS $39.50 IPG.IOASSEMBLED d TESTED FOR ANIMAL CONTROL$44.50 -17tt`aIO, íß.E. aEVISt1EDTRAIL LASERS AIR' HIGH POWERED CARBON DIOXIDE BURNING AND CUTTING ASWISS AiCCO1Mt Complete plans and all pans sources - $10.00 SOLID STATE IR 12 WATTS with built in power supply plans Complete kit with collimator $44.50 $6.00 FAvess a

? > sS; "ONE PENNY GETS YOU TWO"

F any $1 item Buy HOW TO ORDER 1. page PLESSEY CAPS Mld Mld Mld on this When ordering, always use 7 .0015 .068 .27 .01 .1 item catalog number, type i lo for SI 20 for $1.01 ' .47 2nd no.. the .015 .12 1.00 choose name and of the magazine you a re Half and full postage stamp white .047 .12 sire, ceramic. Vertical nag. for ordering from and Unit,. unmarked so please order openn'y!e the month MINN' only same values per item. All Cat. No. 5399A ONE DOLLAR PLUS A PENNY GETS YOU TWO TWO DOLLARS PLUS A PENNY GETS YOU TWO

SO IF TRANSFORMERS, tost sins (°3596) 1.00 SO for 1.01 100'CAPACITOR 30 RADIO AND TV KNOBS, ant styles. sins SPECIAL disc, mylar, lytica, mere (0273$) 2.00 200 for 2.01 (x8217) 1 00 60 for 1.01 10- VOLTAGE REGULATORS, bobby LM320, 340, TO 3 50 TUBULAR CAPACITORS, net volt. and sises (3330) 2.00 20 for 2.01 108219) 1.00 100 for 1.01 30- WITCHES, slides, rotaries, mod. etc )a320H) for 2.01 SO LOW NOISE RESISTORS K, NW. MIR. etc 2 00 60 (.220) 1 00 100for 1.01 200 -RESISTOR SPECIAL A to 1W, carbon, metal 103054) 2.00 400lor 2.01 40 POWER RESISTORS, 3,5,7 w. axial, pop sixes ('B226) 100 80 for 1.01 SURPRISE, 200 -HALF WATTERS, resisters, carb., motel 1.3046) 2.00 400lor 2.01 $25 all kinds of parts in a pah ( ^8294) 1.00 50 for 1.01 100- NATIONAL IC BONANZA, linear.. 7400a ROMS (2560) 200 2001. 201 12 WITCHES. , slid., toggle, etc ( "8295) 1.00 24 for 1.01 I5- LM340T VOLTAGE REGULATORS, Ste 240,70-220 2.00 201 SO COILS AND CHOKES, rt, parnitic, IL etc Ia263S) 30fer ("8297) 1.00 100 for 1.01 100-POLYSTYRENE CAPS, asal'd 0.1000, voltage, M -Q 50 TERMINAL STRIPS, up to 4 solder lugs ("8334) (2729) 2.00 2001er 201 100 100 for 1.01 SO-THERMISTORS,r.sl thatch Ith temp(x4059) 2.00 2.01 SO PRECISION RESISTORS, 1/2W, 1%, axial 1001. (083631 1.00 100 for 1.01 20- BRIDGES. untested. 2.4, 6, amp, wave 1.4022) SO MICA CAPACITORS. fall 2.00 40 for 2.01 ant valus I "H3731 1.00 100f. 1.01 15 .3, .0, etc. 10 SETS RCA PLUGS AND -MIXED READOUTS, hobby, untested, .127, (036191 2.00 301er 201 JACKS, phono ('11402) 1.00 20 for 1.01 150 -QUARTER WATTERS, resistors, metal film, arked 2.00 3001er SO DISC CAPACITORS, ont values long Lade (a3413) 201 (.8437) 1.00 100for 1.01 100 -PLASTIC ISTORS, an TO- 92102604) 2.00 2001er 2.01 20 TRANSISTORELECTRO'S. ant up and ax (08453) 1.00 40 for 1.01 75 HALF 200 -PREFORMED RESISTORS, V. SS, IW, marked, asst'd (02006) 2.00 400 for 2.01 WATTEHS, rosi ston, color coded, ant ( "8454) 1.00 150 for 1.01 150 -PRECISION RESISTORS, Sc, 1W, IX, 2% 1.24210 2.00 300 for 2.01 30 SILVER MICAS, red backs, axial, net. 'BASS) 1.00 70for 1.01 110-DIPPED MOLARS, shiny finish, amen' values ) 2.00 120 for 2.01 5.50 AMP RECT, asst volts up to 25, stud "L717) (02597 1.00 10 for 1.01 30- VOLUME CONTROLS. audio. Ileasr. asst'd values 1024211 2.00 60 for 2.01 100 GERMANIUM DIODES, axial a Inds. test ) °L642) 1.00 200 for 1.01 micro, glass, anon tool SO% yield 100 -STABISTORS, Regulator. 300 -SILICON SIGNAL DIODES, (a2025) 2.00 600 for 2.01 sensing and compute. Axial. excellent yield (.31401.. 1.00 200 for 1.01 may include MMS378. MM5375 2.00 for 100 PRINTED CIRCUITY, WATT RESISTORS. 15- CLOCK- CALCULATOR. 1056381 30 2.01 .est ('01040) 1.00 200 for 1.01 10-PUSH SWITCHES. push -lo -break, ant, alarmo 1.6289) 2.00 20 for 2.01 12 TRANSISTOR SOCKETS, asst npn and types pap ( °0651) 1.00 24 for 1.01 12- MICROPROCESSORS, and support IC's. 2.00 SO -3 AMP SILICON RECTIFIERS, 1.5639) 24 for 1.01 axial, stet V ( °0065) 1.00 100 for 1.01 SO POLYSTYRENE ISO -GLASS 400 MW, untena, bettor than 80% ylald 04740).... 2.00 300 for 2.01 CAPS, plastic coated. Pr.c. ( "010521 1.00 1001. 1.01 7S- CARBOFILM RESISTORS, 14, 45 watt, S L 10%, marked, east's 03534).. 2.00 150 for 2.01 1000.2 bulbs, for 110v.0 hobby, etc I "012221 prol.cts, 1.00 20 for 1.01 250 -UNMARKED CAPACITORS, polystyreee,melded. 10 PROXIMITY REED SWITCHES, ass. sins (.01256) 100 pep values 03505)..2.00 500 for 2.01 20 for 1.01 100-1N4140/114 SWITCHING DIODES, 503+ yield. 111est.d1 2.00 for 6 20915 UHF TO. IS TRANSISTORS (= 01423) , 00 12 for 1.01 (02415).... 200 2.01 30-PC TRIM POTENTIOMETERS, thumbwhael, acrewdrlver ass'I. 2.00 601or 2.01 30 MOLEX CONNECTORS. nylon. asst. sin. 56421 1 (33461.. (° 00 60 for 1.01 15 -SLIDE VOLUME CONTROLS, asat'd valgan. duds, skiff. 200 50.MINI BLOCK CAPACITORS. Erie, red square discs. Ast. values. ('3528) 2001or 1.01 (030571 301.201 100 75-4" CABLE TIES, plastle, like "Ty -an p 2.00 C, 6- CALCULATOR AC ADAPTOR JACK, standard threads 3 terminals. 0,23161 ")5210) ISO for 2.01 100 12 for 1.01 JO-CRYSTALS, map Include CB, Nam L more 2.00 for 50 ONE AMP ZER DIODES, oast, anial,u test 1.01964) 1.00 100 for 1.01 (03250) 20 2.01 C 5-PA-263 THREE WATT 100- TERMINAL STRIPS. from 2 lugs up (313$) 2.00 2001er 2.01 PC BOARDS. for amps ( "112013) 1.00 10 for 1.01 30- NE -2NEON LAMPS, all 100% good 2.00 5-MICRO MINI SLIDE SWITCHES, SPOT 1'02354) 1.00 101.1.01 (02613) 60 tor 2.01 40-ft. SHIELDED CABLE. lend, mlkea. 2.00 BON. 2.01 S MINI MOTORS. 11/2 Odc, for many hobby prof 1'02551) 1.00 lO for 1.01 Ones, (3677) fer 3 -SOUND TRIGGERS, .erred triggers ear w /amp(34251 2.00 for 501144000 RECTIFIERS, n. to 000V, u test 1'02594) 1.00 100 for 1.01 6 201 15 PRINTED CIRCUIT BOARDS, 10-CB CRYSTALS, for phase look loop, HAM. NC /10(a5050) 2.00 201or 2.01 asst sins, hobby ( °020101 1.00 30 for 1.01 2 MERCURY SWITCHES, 50.4 LAYER SHOCKLEY DIODES. Asst. pop. voltaeeal 01072) 2.00 100 for 2.01 silent touch, SPOT 1 "U2123) 1.00 4 for 1.01 ITS A 7S- $07400TTL ICs, SOX+ yield, rep typos (241* 2.00 /SO ter 2.01 6 SNAP, 9 VOC BATTERY, rod n black load . ('02152) 1.00 12 for 1.01 100 -MINI DIP ICI, II ,an 50%+ yield, pep types 2.00 8 1400 VOLT "REO BALL" RECTIFIERS..xi.l 1 AMP (03246) 2001.201 I.U25901 1 00 16 for 1.01 30-LM3$0 2 20 154140 SWITCHING DIODES, 4 AUDIO IC's, watts en -a-dlp 50%+ yield ('5204) 200 101.201 nec. axial 1 "030051 1.00 40 for 1.01 75 -LI OP AMPS, unleslod 50 %+ yield, ampo -dIpU. I.Mlps 2.00 1301or 2.01 6 -10 AMP pUADRACS, w /trigger diode up 600V (- U3620) 1.00 12 for 1.01 ("2416). 100 -T7L. L LINEAR MIXED, with 7400s, 505.1- yield 2 00 5 MICRO SWITCHES, push, west [y04,1.03011) 1,00 lO for (02431) 2001. 2.01 1.01 ISO- PREFORMEDDISC CAPACITORS, mark.d values, aset'd 2.00 300 for 2.01 40 SQUARE DISC STYLE CHOKES. color coded "03203 1.00 SO for 1.01 (.24051 30 TRANSISTORS 7092 2.00 20 for 2-01 204400 s....n, u tool 1 "032911 1.00 60 for 1.01 4- TRANSISTORS TRANSFORMERS, audio, 2000. FACTORY REJECT DIODES. roc. signal, inter, etc mini ( °02295) 1.00 8 for 1.01 I5 PRINTED CKT TRIMMER 40-AXIAL ELECTROS, asat'd valsa capacitance. (.3227) (033$P) 2.00 SO for 2.01 POTS, asst values, etc ( °113346I. 1.00 30 for 1.01 i 6 UTILITY AC 40-UPRIGHT ELECTROS, ust'd values A capacitance. (032261 2.00 10 1e 2. 0 1 OUTLET JACKS. Hlfi, .quip, etc 1' 113502) 1 00 12 for LOl 2011 150 -RED DISC SPECIAL. Erie, mostly marked. pop values 2.00 3001er 2.01 CABLE, 1 tond shielded. 1 -24, for phono 1.03653) 1.00 soft L01 (53411 7- "WATCH GUTS ", LED. who knows how good 2.00 2 for 201 2143055 HOBBY MPH TRANSISTORS, TO 31 "U3771) 1.00 14 for 1.01 1 5267) 10 1 AMP RECTIFIERS, ( 20 for 2.01 10 -PNP 30 WATT TO -3 TRANSISTORS, hobby ('U3772) 1.00 20 for 1.01 of 10000 104007 - 23841 2.00 150 MOLEX IC connectors, for 14, 16, 18, 40 sod ( 2.00 300 for 2.01 SO TUBE SOCKETS, 4, 5,8,7 pin tuns. east 1.03039) 1.00 100for 1. 01 "3324) 25 POWER TAD TRANSISTORS, TO- 202, 30 watts 1 24251 200 SO 201 1.30 AMP POWER TAB QUADRAC. 200 PRY, 70220, 2/trigger ('15901 1.00 2for 1.01 I. 10 PUSH MICRO TOGGLE SWITCHES. .pst I 5635) 2.00 20 for 2.01 10- BULLET RECTIFIERS, 2 amp, 200V. axial 1.841 1.00 201. 1.01 10 MICRO TOGGLES, spat, dpdt. for panel, etc. 1 -8636) 2.00 20 for 2.01 2.MAN4 READOUT, RED. tom anode, sin -,I9" (01503) 1.00 4 for 1.01 10- READOUTS, MAN 3, 50 2 AMP METAL CASE AXIAL RECTS. up to 100 1.40061 2.00 100 for 201 common nth, LED, the claw, RED ( °3:3$) 1.00 20 for 1.01 8 -LEDS, :J 100 -MINI BLOCK CAPACITORS. Erie. Red sq disc style. `03525) 2.00 200 for 2.01 .set. sines and shapes, rod. green, yellow, amber ( °33891 1.00 16 for 1.01 20 PLESSEY 0.1MF 100 SOC 1" SQUARE CAPS 2.00 40 for 2.01 PHOTO FLASH ELECTRO. CAP, 600 MF 360V (038971 1.00 2 for 1.01 1° 55511 10 TV-FM 300 OHM TWIN LEAD SPLICERS ('55471 2.00 20 for 2.01 2- CIRCUIT BREAKERS, glass sealed, axial, " 1 amp 1.2005) 100 41or 1.01 2.95 NICAD BATTERY CHARGER 110x. In ( =40501 200 2 for 201 MICRO MINI TOGGLE, SPST, 2 ins, on -e11, 125V ' 3 amps 1"39361 1.00 2 for 1.01 4 MIKE MOLDERS, for CB's and other mobile 2.00 B for 201 S -CB CRYSTALS. ong. used w /syntholler, asst. Iraq. HC. 18/0 holder ("S051) 1.00 )or 1.01 rigs ) -56341 4 -PUSH , 10 PLESSEY CAPS, IMF 1000 1" eq. CERAMICS( unmarked) 20 for 201 BUTTON. SPOT. PANEL, N.C. 125V 1 A (05289) 1.00 foror 1.01 1 °5633) ,2.00 100 PLESSEY SO for 2.01 10- INSTRUMENT KNOBS, asst. styles and colors, W" shaft (.5121) 1.00 20 for 1.01 CAPS, mixed values marked and unmarked (05613) 2.00 4 -TAPE HEADS, 11111 types 1" 51121 100 8 for 1.01 S- TANTALUM ELECTROS, TEARDROP style, 2.2uí " 25V ("52051 1.00 1 for 1.01 2- INLINE FUSE HOLDERS, camyleto w/5 amp fuse (05213) 1.00 for 1.01 30-4" CABLE TIES, non -dip white plastic 1 "02171 1.00 60 for 1.01 30pc -NEAT SHRINK. asst. sizes, SO% slotrrrg. (x52411) 100 1.01 X 20.TOROIDS, some with n118 1 °54311 100 1.01 Çóp 15-15V ZENERS, 400mw,axial, glas case ( "54041 1.00 ofor to 1eiNECh*pL b Order by Cal. 2- ALUMINUM NEAT for ZENERS! Ne. 52101 SINKS, TO. 220(05336) 100 1.111 m 1 No. 5210A voltage L wattage D.dI 2-5.10. S %, IoW. STUDZENER. DO -4 case ('52871 100 bY Ty Pe SÓ i .fo. : ; 5 10 SALE WATTS Sale 12'SKINNY TRIM POTS, PRECISION. asst. styles, values SO% leld 1x3389) 1.00 24 for 1.01 0Ee1 SO t,AO 1 Watt Sale 10 SALE BOpc- PRECUT, PRETINNED WIRE. 7.5V 5 for SI. IO for $1.01 venous lengths and colon =1971) 1.00 120 for 1.01 rings* 39 %St 6. V 3 for 1. 6 for 1.01 80-MINI RESISTORS, for PC apple, vert, 1/SW, color ceded 5.25 S for 1. 10 for 1.01 ( =3235) 1.00 120f or 1.01 0 0 .48 8.2v 3 for 1. 6 for 1.01 6- TRANSISTOR RADIO EARPHONES, 8 ohms lmped 9.10 S for 1. IO for 1.01 I. 2846) 1.00 16 for 1.01 LM" 558 t,AS 30 E 15. V 3 for 1. 6 for 1.01 10 -5K POTS, audio laper, plastic songe -In 10.V S for 1. 10 for 1.01 mounting I "5124) 1.00 20 for 1.01 LM' S6/ 29 50 18. V 3 for 1. 6 for 1.01 10-182 MEG DUAL POTS, audio laper, "snap LM' 11.V 5 for 1. 10 for 1.01 -In" lent 1051251 1.00 20 for 1.01 X030 79 A0 24. V 3 for 1. 6 for 1.01 SDI AMP ZENERS, asst. values, 39 12.5 S for 1. 10 for 1.01 wide of unteoled 1 "1964) 1 00 LM' j09H 100 1001. 1.01 LM. I 30. V 3 for 1. 6 for 1.01 12 -SCR'S TRIACS. 10 AMP, asst. values, untested SO 13.9 Sfor I. IOfer 1.01 i ( "2087) 1.00 24 for 1.01 71tON05 99 3- pUADRACS, 10 AMP, 100 %prim., 50-100 -200V, TO -220 .30481 1.00 Olor 1.01 LM -7 gA :W 1.00 b for 1.01 tMp3 39 s0 51144007 10000 MINI RECTIFIER,ER epoxy Cato. axial Inds)1 "23831 1.00 10 for 1.01 LL00 00 WE'RE OVERLOADED WITH 60 MOLEX CONNECTOR Type M1938 -4, mobes 1410 40 pin sockets 1°1609) 1.00 120 for 1.01 S 2 -T.V. CHEATER CORDS, for AC power, w /e' cable (055521 1.00 for 1.01 .292 BRAND NEW IC'S -T.V. CHEATER CORD JACKS. : Sale 1 for Order by typo number l0 for use with ( °5520) 1 00 20 for 1.01 10 -1 AMP 200V MINI RECTIFIER, 1114003, $ .10 S .19 Typ. Sale 2 For epoxy, axial I a23791 1,00 20 for 1.01 LYTIC 507401 2.1.5V SILVER OXIDE WATCH BATTERIES, Ispeoltay dia.) ( -5063) 1.00 4 for 1.01 KLINIC 507403 .1 .19 0 5917470 .29 .30 3 -LCD WATCH READOUTS, 315" digits, 7 gag, dim 145 1" ('5066) 1.00 6 for 1.01 SN7406 .29 .30 O 5117472 .29 .30 10 -IC DICE CHIP, Complete ELECTRO'S .18 .19 SN7474 .35 .36 circuitry, asst. .Ia.s ( °505) 1.00 20 for 1.01 SN7410 2100KOx MARKER Order by Cat. 6e. "3269 and value .21 CRYSTALS, .pacify 104.067, 104.092, or 114.00 KID I "3088) 1.00 4 for 1.01 SN7420 .20 SN7410 .50 .51 12.1.50 LAMP AND SOCKET SET. 200ma, T2 style (.39561 1.00 24 for 1.01 F V Sale le SALE SN7426 .29 .30 O 5N7496 .65 .66 10 15 IO f,, $1 20 /or 51.01 .26 .90 10 -RCA PHONO JACKS, chassis mount, letlon base ( °5119) 1.00 20 for 1.01 SN7437 .25 5074164 .89 10- PIN HEAD 10 25 Bloc $1 161or $1.01 .21 COAXIAL LEDS. RED ( "56171 1 00 20 for 1.01 507440 .20 S074165 ,89 .80 ILO SO 6for $1 1210r $1.01 .21 O 4.5 -DIGIT 7- SEGMENT RLUDOUTS. in fiat pak cas. I "5818) 1.00 for 1.01 SN7450 .20 5074192 .79 .90 4 20 IS 9tor S1 18 for 51.01 -w" BLOCK TRIM POTS. SK to 200K ( "2536) 1.00 8 1.01 507455 .20 .21 0 SN74193 .79 .BO for 15 25 1 "FOTO -FET" N CHANNEL, J. 1. 51 161or $1.01 507464 .20 .21 SN74195 .69 Crysl.lonics. Sealed Effect Transistors. (11891 .... . 1.00 2for 1.01 .70 1-VOLTAGE REGULATOR, 10202 cas., 12V SO 15 Bfor SI 1210,91.01 600MA 1 1.00 21or 1.01 °19001 50 25 4 for 1.3 DIGITS ON A DIP, LED. rad, DL- 331^ 1887) 1.00 2for 1.01 51 81r01.01 IGO 15 3for 6for 3- MM52822K DYNAMIC RAM, smelly type ("3459) 1.00 2 for 1.01 51 $1.01 100 2S 21.r RIBBON CABLE AT THIN PRICES 10 -2N711 HIGH SPEED SWITCHING TRANSISTORS, TO IS, op. 1°3374) 1.00 20 for 1.01 5l 4 for 51.01 1000 3 2for SI 4for 51.01 2 -15W HI POWER TRANSISTORS, 220V, npn, 7066102797).- 1.00 41or 1.01 'ond Sale 2 for Ultra flat! 1000 16 1 for 2 for 424 PIN IC SOCKETS ('21601 1.00 0for 1.01 SI 51.01 28 AWG 11 PC for 'Axi.1 ft 20 ft 1-MM 5312 DIGITAL CLOCK SHIP, 100% ("1525) 1.00 210, 1.01 type e000. 10 10 51.90 51.88 14' fl ft 1.90 16 ft 1.89 I.MM57254 FUNCTION CALCULATOR CHIP, 100 %( "2036) 1.00 2 for 1.01 20 511 1.98 10 ft 1- MM5202 ERASABLE PROM, 100%1.1525) 1.00 Ifer1.01 1.99 3.10 AMP BRIDGE 25 4 8 1.98 N 1.99 25v RECT, comb sty'. 1"2447) 1.00 6ler 1.01 2 AMP METAL SILICON Order by Cat. 10-203565 RF 26 4 ft 1.98 8 ft 1.99 TRANSISTORS, 70106, 2HS1331.3372) 1.00 20 for 1.01 and 4 10- CYLINDER RECTIFIERS 34 3 N 1.98 6 N 1.99 No. 3939 LINEAR SWITCHING TRANSISTORS, 202905. pop, TOS ( °33751 1.00 20 fer 1.01 36 3h 1.98 Eft 1.99 conductors. n 50-2 AMP CYLINDRICAL RECT. up to 1K,u toot 104006) I00 100 for 1.01 Class sealed Order by Cal. Ne.084 S.OPENFACE READOUTS, Axial loads and voltage 40 2 N 1.98 N 1.99 LED, rad. some togs missing mostly duals ( "3952) 1.00 lO for 1.01 50 2 N 1.98 ft 1.99 30 202222 for aquiv.l. TO 16 morel case I" 19!12) 1.00 20 for 1.01 500 10 S.59 20 for 5.60 40-TERMINALS, Incl. ring and spade typos, for .12 to ..20 wiro f. 60 1 N 1.98 2 N 1.99 ( "3955) 1.00 80 /or 1.01 , 100V 10 f. .69 20 for 70 10 -DATA ENTRY SWITCHES, SPIT, lamp, 125V norm open (.3961) 1.00 20 for 1.01 ' 200V 10 fo .79 20 for .SO color coded. - 10- FLUORESCENT OVERFLOW READOUT TUBES. w /leads 1.32881 1.00 20 for 1.01 400V 10 for .19 20 for .90 10- 203704 7092 TRANSISTORS ( "35051 1.00 2010, 1.01 1- ZHSOOI OOV TRANSISTORS STUD I "2800) 1.00 210, 1.01 t LEDs: S YOUR CHOICE 5 for 51.00 POLY PAKS® lc SALE 10 for 53.01.0 1 MAY P.O. BOX 942.N3 -O -LITE IN4000 Epoxy Rectifiers Order by Cat. No. cE0. "BEEN 1700 MICRO TOPHAT 8E Peorleo' SO. LYNNFIELD. MA Cat. Type001 Vol Salo lc SALE! RED 1785 JUMBO TAPER CLOUDY 01940 DIODES SO for 20 1002 MICRO LASER 2378 1144002 100 10 for .85 20 for .86 SINGLE PIN RED Term.: Add Postage Rated: Net 30 1940 MICRO YELLOW S 2379 144003 200 10 for .95 20 for .96 Phone: 2135 JUMBO RED (617) 245 -3828 $ $88 2380 1.14004 400 10 for 1.19 20 tor 1.20 Retail: 16 -18 wa 2 for 8.89 2381 1,4005 600 10 for 1.39 20 for 1.40 2136 JUMBO TAPER RED Del Carmine St. each 2137 MICRO RED 3 508 2382 1 .14006 800 10 for 1.49 20 for 1.50 :MINIMUM MA 2790 JUMBO RED CLEAR ORDER: S8 Wakefield, - - 2383 1144007 1000 10 for 1.59 20 for 1.60

COPYRIGHT 1978 - POI.Y PAKS ", INC. CIRCLE 20 ON READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 91 ELEMENTARY ;h;1:. FREE!: ELECTRONICS EDMUND SCIENTIFIC OBBY AT Explore Astronomy, Biofeedback, Computers. . Health Lasers. Magnets, Microscopes, Optics. Photography, Weather... Over 4,000 Fascinating Items. More Than 160

Colorful Pages .. . MART ,``, The Exciting. FREE Edmund Enclose sufficient postage.s1 Catalog' a; te DELTA saves you $$ in electronics R Currently sold at $85 Itl'-1111111 l':spel>tarl Bodine Motors 2 for Years of 4 Stereo System $45. No. 108 Dena 556645 Service! Edmund Scientific Co. 1979

f r Yes! Rush me your FREE Catalog so that 7 $ßßß5 I can explore Edmund's World of Science.

ORIGINAL Name RETAIL (Iodine Ncl- 1252- It,I ).', fid IT, Motor apeed I1 , FI I l,nlrpml $99.95 :, Mf capacitor. cut. duty. Address torque 5.7 mein. Shaft apead Cat rpm. Fur horixontl \1 INS City mtg. 1 III. :i2 tapped holen in tare of g' r motor..Shaft is 3 a" dia I" lung. Current net price is State ZIP LESS THAN roler, plus llt.ii l fur the rapo itor. Each WHOLESALE!!! Wc include capacitor 055705 Clip and Mall Coupon Today to The RP -1000 system consists of an AM /FM steno Edmund Scientific Co., Dept. EKO6 radio /phonograph. TWO twin dual cone speakers in molded dust caver, MINI -DIPPED Edscorp Building, Barrington, N.J. 08007 enclosures (to make a 4-way speaker system), phone N 45 rpm adapter and a headphone jack. The RP-10q ta rated at 30 TANTALUM 147 109 MHz. are J watts AM: 5.35 to 1605 Min. and FM: to All hmnd new in original factory cartons: and are complete with a CAPACITORS \ factory 90-day warranty. The original retad wan $9!! n5. Delta // 027555N .001mf 027605 S0V. 4 for $1.00 .002mf4+100v, 4 YOU'RE UNDER SURVEILLANCE!! DOES YOUR SMALL PROJECT NEED A a 27615 .01 for $1.00 027645 mf@ 50v. 3 for $1.00 0.1 WO 35V. 3 for 51.00 A HOST OF PEOPLE, AGENCIES, AND COMPUTERS POWER SUPPLY x27705 2.2 mf@ 35V. 5 a limited tity of SONY SWITCHING for $1.50 Wave obtained a27655 3.3 mf@ 16V. 3 ARE BUSY SPYING ON YOU AND YOUR BUSINESS POWER SEIPP! JES AT n ridi cable price! thin power supply is V 027665 for $1.00 efficiency, smaller atm & 3.9 wife (6V. 3 for the "State of the Art' for greater a2767$ 22 mfel 16V. $1.00 EVERY DAY, OFTEN ILLEGALLY... . or 20V (0 I amp; and are removed $ for $1.50 They are rated at 26V a 27575 22 mf@ fweight.rom new TV seta. With a little ingenuity and yourself'"do-it- 35V. 5 for $2.00 supplies 5.0V n These kit from Delta you can build 3 very valuable (u capacitors In limited quantities! HOW TO STOP IT OR DO IT BACK! IA: .12V n 500 ma or 5.OV (d 5110 fina, & .I2V de 250 ma.) Note: these auppliet are great for small project,. using TTI _ Op 2 For Amps. Description Sala I 066465 249 or 29V (0 1.0A 17Ú51e. $15.00 a56475 90V ra 1.0a 646 17.00 a5«$ -129 [.x500 ma . 9.95 19.00 MEM."O x56495 5.0V .a & .12V ,d 250 TA 10.95 21.00

takes some MAN 6040 When there is a new development in electronics, it lime before that development is available to hobbyists and Dual Digit Readout experimenters, especially at surplus Thai time. we have reversed the trend. and announce a DELTA EXCLUSIVE, the [03 DELTA I1EI.TA DETECTOR. Thin device detects any motion MOTION movement for a minimum distance of &R The secret is in the B a Burglar ultra-complex cuatam LOI chip, which trombines the latent in linear & digital circuitry. The device is completely self 3 x 2 /i ", and operates from four "AA" contained. in a cane 6x 5 NiCad batteries. Nothing else is needed,ee for the device to perform or ALAR its basic function, motion detection. When motion or movement ft©Th[ I I P ia detected, a "whoop" alarm la sounded. The MOTION $5 DETECTOR is designed to provide either an audible or silent W-K.O therm. The silent alarm is controlled by a timer, which delays Me. the alarm up to 30 seconds. The oient alarm activates e relay, 50D' ! w- 1 µ2.N O.O'l'.l whose contorts are brought oui to pia q, and will activate ANY A ,ii____'''', 1° device, each sa men. ham, tape recorder, telephone dialer. etc. 'J Only The Motion Detector works on a CHANGE OF LIGHT. Any j i change of 594 or more, triggers the detector. Works within a rye ,{ em 100 h to candlepower, . rangeange of 0.1 candlepower (almeet dark), brae), a range of 1000 to I. NO external light source fia ia ,fil lot A Large Format (8'/2" x 11 '') Quality Paperback, 240 Pages needed. rtiu y. :? or room, the Motion i When left in a darkened j' ._ISi Detector acte ae a fantastic FIRE ALARM. The light `MMAN-6640 high perform single match, anywhere to the room, trigq a the alarm, so that compact a ,11 GIT the device becomes an intrusion alarm and fire alarm, alt la 0CC. readout having a brightb fight orange BUGGING ht und Doha Sole display with a WIRETAPPING me $995 S61Ì5 ComNate 'notion dettektr kit (less decimal land Common batteries 524.50 Cathode). Each digit is .560 x TAILING Motion Detector Chic only, alti) date 9.95 '120" for easy reading. tae 1 for 10725 ya OPTICAL AND b 5611 P.C. boards, set ot2 6.50 digital readout displ MOTION instrument panels. digita l ELECTRONIC SURVEILLANCE 5.95 locks, TVs, radios, etc. S6S62 Battery charger for above SURREPTITIOUS ENTRY DETECTOR 56355 Completely assembled kit. w/batterM. & ('omplcae with charger 69.50 B dais and pinnule DETECTIVE TECHNIQUES No. 11035 S 1 WEAPONS I mir COUNTERMEASURES -1111 Ihnir VIRTUAL ENCYCLOPEDIA ON SURVEILLANCE ji01= "A .,,.ifil ..,_,.,...,_.,_ 9 1 EVERYTHING YOU'VE ALWAYS WANTED TO KNOW ABOUT SPYING." - PLAYBOY MAGAZINE it 1 577:. i:' / í -_. ... 1YR. L - ELECTRONICS :i l With Each Order You Receive Free Other Material And Literature /Ill TO DELTA'S l SUBSCRIPTION II"_ P.O. BOX 2, DEPT. 2S For Investigative Procedure NEWSPAPER' ST., I `SURPLUS 7 OAKLAND PLUS FREE 120 -PG. CATALOG AMESBURY, MASS. K 01913 DELTA ELECTRONIC HOBBIES-1, QUIMTRONIX r L2151 9OrORD gWY. 00RaVIl LE. ATLANTA CA i TEL. (617) 388 -4705 Postpaid -P.O. Box 548 -RE Itlhell in nur area, northeastern Blass. or southern N.JI. I,isit our new showroom! Seattle. Washington 98111 CIRCLE 34 ON READER SERVICE COUPON CIRCLE 9 ON READER SERVICE COUPON / -April 1979 92 ELEMENTARY ELECTRONICS March LINEAR I.C.'S

LM324N .49 Quad Op Amp LM339N .49 Quad Comparator LM555N-8 .29 Timer LM556N-14 .59 Dual Timer LM723CN .34 Voltage Regulator LM723CH .39 Voltage Regulator LM741CH .37 Op Amp LM741CN-8 .24 Op Amp LM 1458N-8 .39 Dual Op Amp

VOLTAGE REGULATORS

UNIT PART NO. PRICE DESCRIPTION LM323K $5.50 3 Amp 5 Volt Regulator 78H05KC $5.75 5 Amp 5 Volt Positive Regulator BRAND CMOS's TO3 NEW! 7800ÚC Series .79 Positive Voltage Regulators TO -220 /LM340T (Plastic) l Amp CD40008E .17 CD4042BE .59 CD4515BE 5, 6. 8, 12, 15, 18, JUST RELEASED $1.95 24 Volts CD4001BE .17 CD4043BE .57 CD4516BE .69 1979 CD40028E .17 CD40448E .55 CD4518BE .79 78MOOHC Seres $1.50 Positive Voltage Regulator IC MASTER CD40068E .87 TO.5 /LM340H CD4046BE .99 CD4519BE .47 1/2 Amp 5.6,8, 12, 15, 18, 24 Volts CD4007HE .17 CD4049BE .33 CD4520BE .69 7800KC CD40088E .75 CD4050BE .33 CD4522BE .99 Series $1.60 Positive Voltage Regulator t Amp 2500 CD40098E .39 CD4051BE .54 CD4526BE TO -3 / LM340K 5. 6, 8, 12, 15, 18.24 .99 Volts C040108E .39 CD4052BE .54 CD45278E $1.09 78LOOAWC Series .29 Positive Voltage Regulator pages CD40118E .17 CD4053BE .54 CD45288E 69 100 MA 70.92 2.6, 5, CD40128E .17 CD40608E .99 CD4531BE .74 6.2, 8.2, 12, 15 Volts CD40138E .32 Complete integrated circuit CD4066BE .44 CD4532BE $1.19 7900ÚC Series $1.10 Negative Voltage Regulator CD40148E .73 CD4068BE .21 CD4539BE .99 TO.220/ data selector. Master guide LM32OT 1 Amp 5, 6, 8, 12, 15, 18, 24 Volts CD40158E .69 CD4069BE .21 CD4543BE $1.39 to the latest I.C.'s 79MOOHC including CD40168E .35 CD4070BE .29 CD4555BE .65 Series $1.50 Negative Voltage Regulator CD40178E .62 TO.S/ LM320H microprocessors and CD4071BE .21 CD4556BE .65 1/2 Amp 5, 6, 8, 12, 15, 20, 24 Volts C04918I3E .69 CD4581BE $2.25 consumer circuits. C04072BE .21 7900KC Series $1.95 CC/48198E .39 C045828E .79 Negative Voltage Regulator CD4073BE 21 TO.3 / LM320K 1 Amp 5. 6, 8, 12. 15, Free Quarterly Updates CD492013E .69 C040758E .21 CD45848E .60 18, 24 Volts 0040218E .69 CD4076BE .79 CD4585BE .90 78MGT2C $1.25 Dual In Line Adjustable CD40228E 4 Terminal .69 CD4077BE .25 40014PC .59 Positive Voltage Regulator CD40238E .17 CD4078BE .21 40085PC $1.09 78GU1 CD40248E .49 CD4081BE .21 40097PC .60 70.220 $1.45 1 Amp Adjustable Positive Vollage CD40258E .17 CD40828E .21 40098PC .60 Regulator C04326P3E $1.39 CD4085BE .69 40160PC .89 78S4OPC $2.50 Switching Regulator Texas Instruments CD44278E .39 CD4086BE .69 40161PC .99 CD4N288E .57 0040938E .40 40162PC .89 Low Profile Sockets C0411298E .74 CD4104BE $2.25 40163PC .99 CD4e30BE .35 CD4502BE .85 40174PC .89 CD4R338E $1.45 CD4508BE $2.25 40175PC .89 Finest Quality Socket available in the CD4N34BE $2.25 Co4510BE .88 40192PC $1.19 CD4H358E .64 All new major manufacturer prod- world. CD45118E .99 40193PC $1.19 Nobody can match Texas Inst- CD41i40BE .74 CD45128E .59 40194PC $1.10 CD41W1BE uction material offered. ruments .74 C04514BE $1.95 40195PC $1 10 quality -a unique combina- Largest variety of device types tion of I.C. technology and multi - available anywhere. metal expertise. c Over one million pieces in stock. 4 MICROPROCESSOR sh. Contacts Price Contacts Price MOS Static RAM's 8 PIN .08 CHIPS 22 PIN .22 Stock level Part 14 PIN .12 24 PIN .24 CPU's No. Price 16 PIN .14 28 PIN .28 1 Stock level Part No. Price 11400 2114 $7.50 18 PIN .18 40 PIN .40 4600 8080A :9,(5.50 4K(1Kx4)300NS 20 PIN 20 16000 6800 X7.95 74000 2102LFPC $1.19

INTERFACE 1K 350NS ( Low Power) GENERAL INSTRUMENT SUPPORT CIRCUITS 19700 2114 $6.95 1 Amp Rectifiers (Epoxy) 1.5 Amp Single Phase Stock level Part No. Price 4K (1K x 4)45ONS Silicon Bridge Rectifiers Stock level Pan No. Price Stock level Pan No. Price 4000 8212 1.98 MOS Dynamic RAM's 1.1 Million 1N4001 50V .029 320000 WO6M 600V 34 .6Million 1N4002 1400 8214 3.95 100V .039 110000 WO8M 800V 39 Stock level Part No. 1.4Million 1N4003 200v .045 Price 1.9Million 1N4004 400V .049 2800 8216 1.98 1N4005 16000 4K .9Mdlion 600v .055 1500 8224 2.75 4027 $2.95 .4M0Iion 1N4006 800V 065 4K (4K x 1)300NS 16 PIN I.7Million 1N4007 1000V 07 4000 8226 1.98 1700 8228 4.75 21500 416.3 $9.95 200NS 700 8238 4.75 Part No. SWITCHING Price 5800 8251,,y 4.95 93000 416-5 $7.95 DIODES 1N914 (100V 4NS) .027 300NS 1N4148 (100V 4NS) .027 550 8253 14.95 11000 8255 5.95 UART's 400 8257 9.95 Stock level Part No. Price Z80-CTC $10.90 800 8259 14.95 Zilog Z80A-CTC $13.10 44000 AY5 -1013A $4.95 3300 6810 3.50 3800 AY3.1015 Z80-DMA $32.20 $5.95 2200 6820 3.95 1K 780-CPU CMOS RAM $13.60 Z80-SIO/0 $45.00 4200 6821 3.95 Z80A-CPU $16.20 Z80A-S10/0 Stock level Part No. Price $50.00 3000 6850 4.95 21400 Z80-PIO $10.90 Z80-SIO/1 $45.00 1200 685 4.95 5101 $4.95 Z80A-PIO $13.10 Z80A-S10/1 $50.00 45ONS (Low Power) I P.O. BOX 1035, EE -2, FRAMIfNGHAM, MASSACHUSETTS 01701

Over . tie . counter sales. MINIMUM ORDER $10.00 ADD 12 MemerlRd., Natick, Mass 01760 $2.00 TO COVER POSTAGE & HANDLING Behind ayes on Rte. 9 -Active Telephone Orders & Foreign customers please remit payment Enquiries 16171879.0077 on an international bank draft or international postal IN CANADA 3 LOCATIONS money order in American dollars. *E1ectronic 5651 FERRIER ST. 4800 DUFFERIN ST. BAXTER CENTRE MONTREAL, QUEBEC DOWNSVIEW, ONTARIO 1050 BAXTER ROAD H4P 2165 M3H 559 OTTAWA, ONTARIO SalPS Corp Tel: 1511) 735.6425 Tel: (416) 661 . 1115 K2C 3P2 Tel:(613)820-9471 41112

ELEMEN ï ARY ELECTRONICS /March -April 1979 CIRCLE 4 ON READER SERVICE COUPON 93 C CMMAND >? SEARCH Simply Basic ITEM >? TRANSISTORS (Continued from page 71) ITEM TRANSISTORS FOUND IN LOCATION: BOX B

COMMAND>? QUANTITY DELETE FOR DELETION OF A PARTICULAR ITEM LOCATION CHANGE TO CHANGE THE LOCATION OF AN ITEM ITEM >? RESISTORS QUANTITY CHANGE TC CHANGE THE QUANTITY OF AN ITEM ITEM RESISTORS QUANTITY: 56 LCCATICN FIND LISTS ITEMS IN SPECIFIED LOCATION END TO CLCSE FILE AND EXIT FROM PROGRAM >7 DELETE SECTOR START? 1104 COMMAND ITEM >? SCREWS

COMMAND >7 START COMMAND >? DELETE LINES

START FILE ENTRIES HIT RETURN TO ADVANCE ITEM. D TO DELETE ITEM LOCATICN. & QUANTITY (SEPARATED BY COMMAS) ENTER ITEM. CR T TC TERMINATE DELETE LINE FUNCTION

RESISTORS,BOX 8.56 RESIST CRS? CAPACITORS,UNDER BENCH,82 CAPACITORS? SCREWS.BOX 11.200 TRANSISTORS? D TRANSISTORS.BOX 8.11 R OUND STAPLE 3 UN? ROUND STAPLE GUN,GARAGE,I DIODES? D DIODES,BCX 11.32 NAILS? STOP..0 SOLDERING IRON? T

COMMAND>? CATALOG COMMAND>? CATALOG

ITEM LOCATION QUANTITY ITEM LOCATION QUANTITY RES IST CRS BOX 8 56 RESISTORS 3CX b 56 CAPAC IT CRS UNDER BENCH 62 CAPACITORS UNDER BENCH 62 SCREWS BOX 11 200 R OUND STAPLE GUN GARAS E 1 TRANSISTORS BOX 6 I I NAILS B CX 4 60 RCUND STAPLE GUN 3 ARAG E 1 SOLDERING IRON CN TOP OF WORKBENCH DIODES BOX 11 32 5 ITEMS IN CATALOG 6 ITEMS IN CATALOG

END O-CMMAND >? UPDATE COMMAND >?

UPDATE FILE ENTRIES ENTER SECTOR FCR DUMP? 1125 SECTOR . 1126 / 7 ? NAILS,BOX 4.60 NEXT AVAILABLE / 8 ? SOLDERING IRON. ON TOP OF WORKBENCH1 / 9 ? STCP..0 READY

PRINTED CIRCUIT KITS Understanding Diodes MAKE CARDS QUICKLY (Continued from page 82) of the materials from which they are made. 2. A diode converts AC to DC because it forms a one - way street for current. A device that does this is called a rectifier. 3. Output from a rectifier is pulsating DC. To smooth out the pulsations, a full -wave rectifier can be used. By adding a filter circuit- capacitors and resistors, or capacitors and a coil -the ripple can be made relatively smooth. 4. The smooth DC voltage can be taken from the power supply in desired values by tapping a bleeder resistor.

32X.0-1 kit

ONLY Vector kits contain: jó] Positive photo -resist coated AND uncoated copper laminate -no o SERVICE messy photo - reversal -no spraying, dipping, or baking. i 4 types of art aids: rub transfers, ink, tape, cut and peel -use 1 or all. 1:1 circuit art rub transfers -IC sets, pads, lines, connectors, symbols, letters, and numbers. Everything included -just add water and sunlamp or bright sunshine. . Liquid etchant and developer -no dry chemical mixing problems. I °r AND . . Process choices -make circuit on copper and etch for 1 card. Make circuit on film, expose, develop and etch for 1 or many cards 116,_ Al llEir- Ú' sunlamp mytar !cardsI developer 1 or many PC's ART film & etchant "Hey, Tom.... Fella here can't AIDS find his CB handle. He wants to 4. card + etchant = 1PC know if it might have fallen out 32X.0-1 kit makes 7 PC cards, $28.00, 32X -1 starter kit makes 2 cards, $11.50 of the box!" Prices subject to change without notice. 510177 Vector Electronic Co., 12460 Gladstone Av., Sylmar, CA 91342

CIRCLE 1110N READER SERVICE COUPON ELEMENTARY ELECTRONICS /March -April 1979 94 Three Into TRS Two. The Level II mod up- yourselfers by providing free in- -80 Update kit consists of a small printed circuit stallation. (Continued from page 42) board with the three ROMs for the With Level II BASIC the TRS -80 12K BASIC and an empty socket, a becomes a really powerful, and more ribbon connector set, a DIP jumper, a important, useful computer for the hob- BASIC actually runs at 500 baud, small resistor, and three cassettes, two byist and student. It's only limitation meaning everything loads and dumps of which are shown. The two 'cassettes remains lack of a hard copy permanent in at least half the time. provide conversion programs so data record, but that's taken care of with How to Order. Here's how the modi- and programs originally recorded in Radio Shack's optional "Screen Print- fication works. You order the Level II 250 baud Level I BASIC can be run, er," a relatively low -cost, unusual de- modification kit at your local store. and rerecorded in 500 baud Level II vice we hope to bring you a report When it arrives you give your com- BASIC. The third cassette has the free- on in the coming months. puter to the manager. He sends your bie games of blackjack and back- One note of caution. The Level II computer and mod kit to the local ser- gammon Radio Shack gives with all 500 baud cassette interface is a rather vice center. They do the installation, their computers; it has nothing to do finicky device, and is extremely sensi- check it out, and return a tested, up- with the conversion. Not shown is a tive to input level and "tone" from the graded computer to your store. A fairer rather extensive, advanced, Level II cassette recorder. It works fine with the deal you're not likely to find anywhere. BASIC Programming Manual. This low cost Radio Shack CTR -41 cassette But what goes into the mod kit? Like manual is not like the beginner's Level recorder, but requires hours of experi- every hobbyist we had the itch to know I manual which teaches programming mentation to get the correct adjustment not only what went into the mod kit, to people who never heard the word with other recorders, particularly those but how it was installed. "BASIC" before. Level II assumes you not sold by Radio Shack. Don't think Since the service manual is available now have learned how to program. you can improve performance by using only to Radio Shack service Centers, we (Yes. The Level I book is available for a more expensive, or "better" recorder. had to make special arrangements to get beginners.) Do it the way Radio Shack says, with the mod kit and the manual into order No Do -It- Yourself? You might ask the equipment Radio Shack specifies, to show our readers how the "magic" why the user can't do the job himself. and you'll have no problems with data of upgrading was done by Radio Shack Well, firstly, to protect the CMOS ICs handling. for no more than the basic cost of the the installer must wear a "ground brace- If you already have the TRS -80 Level II BASIC. let" to avoid zapping the ICs with a Level I you owe it to yourself to get But before we get into the actual high static voltage. Then there's the the upgrading to Level II as soon as conversion let's take time out to see DIP jumper. (Aha! Thought we forgot, possible; . it virtually gives you a whole what we're upgrading. The TRS -80 eh ?) The jumper must be programmed new computer. If you haven't made up Level I model has the 4K BASIC in for the amount of RAM. Make an your mind between Level I and Level one or two ROMs, depending on which error and everything gets fouled up. II, go Level II for it's well worth the one of two models you have. It's a simple thing to cut the appro- extra $99. As for those afraid to let The 12K Level II BASIC is in three priate jumper, but if you make an error their "baby" out for upgrading to Level 4K ROMs; obviously, we can't force a service technician could spend hours II, Radio Shack guarantees you get three ICs into two sockets, so that's searching for an unsuspected problem back a fully working and checked out where the main conversion must take with memory addressing. This way Level II. Have no fear; it's the only place. Radio Shack avoids disgruntled foul -it- way to go.

BNEE Semester IV 10 -to -12 words per minute and 20 -to- Operating Aid CD -5/9 W1AW Sched- (Continued from page 56) 25 words per minute. ule). The secret is to copy code at speeds Among other times, W1AW airs the significantly over your present, com- code bulletins nightly at 8 p.m. East- fortable level. Assuming that you have ern time on 1835, 3580, 7080, 14080, that you have a momentary interrup- moved to something around 10 words 21080, and 28080 kHz. You can check tion. It is not necessary to follow it by per minute with solid copy, make a your copy by listening to the phone callsigns or an explanation., For exam- jump to 18 words a minute. Do not at- bulletins at 9 p.m. Eastern on 1835, ple, if I were interrupted in signing tempt to build your speed incremental- 3990, 7290, 14290, 21390, and 28590 off: ly; at 13, then 15, then 18 w.p.m. kHz. TNX FER FB AS Where do you get this high speed The Code Exam. What should you WB2AYA ex- should recognize this and code practice? Code tapes are one an- pect when you take the code test for just sit tight. Perhaps he'll send an R swer, but they tend to be incremental the General (or Advanced) acknowledging class li- my request to "wait." in speed or they can be memorized. cense? You'll take the exam with other I'll be back to finish the thought. The best code tapes, in my opinion, persons. After filling out the applica- Logging your QSOs. FCC rules have come from 73, Peterborough, NH tions, the code test is the first piece been relaxed over the years on what 03048 ($4.95 plus 25¢ postage). The administered. must be retained as operating records, 14 w.p.m. tape is an hour's worth of You'll copy a mock QSO (at 13 but I would recommend a formal log cipher groups (5 characters per group) w.p.m.) and then you must answer a of your QSOs be retained. One of the that is impossible to memorize. I found minimum of 8 (out of 10) multiple best logbooks (and certainly the mostly I could copy 18 to 20 w.p.m. straight choice questions based upon the mes- widely known) is the one published by text after getting sixty percent of the sages sent. This new test, in some ways, the American Radio Relay League. 14 w.p.m. tape. is easier than the old -style test wherein Follow the directions in filling out the An alternative is the on- the -air code at least 1 minute out of 5 had to be pages. practice stations (see the list on form error free copy. Upgrading your code speed. Although . CD -139 published by the American The second part of the examination the code is a barrier for many ama- Radio Relay League) or, preferably, is the writing. If you pass the code and ;eurs, it is possible to solve the psycho- the 18 w.p.m. news bulletins aired on fail the written, you can retain logical plateaus credit that crop up around the ARRL's station, W1AW (see the for the code for up to a year. ELEMENTARY ELECTRONICS /March -April 1979 95 11111 ...... 1111...... M....i Classified : IVIARKET li ...... mulo...... mim ELEMENTARY ELECTRONICS -is published Bi- monthly. The rate per word for CLASSIFIED ADVERTISEMENTS is $1.30 payable in advance -minimum ad $15.00. Capitalized words 400 per word additional.

DO -IT- YOURSELF Cont. ADDITIONAL INCOME BUSINESS OPPORTUNITIES - Cont'd - LES- TELL US YOUR PROBLEM, we'll tell you how to MECHANICALLY INCLINED INDIVIDUALS $1200.00 MONTHLY CORRECTING PUPIL'S IN SONS!!! Start Immediately. Free Report. Send self - fix it. TV repair. Personalized Instructions. CHC WANTED -ASSEMBLE ELECTRONIC DEVICES Info., Inc., P.O. Box 128, Horsham, PA 19044. YOUR HOME. Get started in spare time. Experi- addressed stamped envelope. Home, Box 9201 -SBBK, ence, Knowledge or Investment Not Necessary. Ex- San Diego. CA 92109. PRICE BREAKTHROUGH. Do it yourself GIANT pect big profits: $300 -$600 /Wk. Possible. Write for SCREEN t.v. projection kits. 5x6' pictures from your NEW! 5 "proven" wholesaling opportunities. $100.00 Box 3002, free literature telling how. Electronic Development daily! " Capital /experience unnecessary." Free bro- t.v. set. $19.95 ppd. Mark V Marketing, Lab, Box 1560E, Pinellas Park, FL 33565. chure! Allrightco, Box 91309-E3, Cleveland, OH 44101. Springfield, IL 62708. $200 WEEKLY: BECOME COMMISSION MAILER. HUGE PROFITS selling gifts, novelties. Newberry, EDUCATION & INSTRUCTION FREE REPORT. GRAHAMS, DPBX 99371, TACOMA, 1975A4 FM464, Seguin, TX 78155. WA 98499. EARN EXTRA MONEY in your spare time mailing USED Courses! Books! Lists 25# SMITH'S, 124 Distributing. Mail- commission circulars. Rush a stamped addressed en- Marlborough. Salem, MA 01970. PROFIT 1000'$ in Independent velope for free details. RAL, Route #1, Ogden, Iowa t List Included. Guaranteed $5.00. Glass, 150 Lee, GET INTO BROADCASTING: Become DJ engineer. LA 50212. Start your own station. get free equipment. records. NEW EXCITING BUSINESS. CONSOLIDATED Free deaths. "Broadcasting," Box 130 -G3E, Paradise. ACCOUNTING & TAX SERVICE GARAGE SALE, FLEA MARKET OR AUCTIONS. CA 95969. home. watch it grow. Write for Free Start small at LEARN CB Radio repair with no electronic knowl- YOUR INCOME TAX! Amazing report re- details. SEMCO ENTERPRISES, DEPT. 45E, 288 CUT Trail, Williamsville, NY 14221. edge or expensive equipment. Unique guaranteed veals 20 money saving secrets. $1.00 refundable! John Sundown method already taught thousands. Write: CB City - Matson, 256 EE(3) South Robertson, Beverly Hills, $300.00 WEEKLY Mailing Circulars. Write: EE, 6241 Glade, Suite L -303, Woodland Hills, CA California 90211. McGuire, Box 91054, Tacoma, WA 98491. 91367. AUTHOR'S SERVICE MAILORDER . $2,000 monthly selling informa- COLLEGE degree by mail, via resume. Education, tion by mail, Free Proof! Images, 550 Frontage, 2560 South Robertson, Beverly Hills. CA 90311. Northfield, IL 60093. AUTHORS make money writing. No Gimmicks. LEARN Computer Programming (BASIC or FOR- Free Details. Fred Fleet, Box 235, Washington, PA $480 weekly. Home mailing program. Alltime, Box TRAN), Electronics, FCC. License, Mathematics, 15301. 25131 -J1C, Tamarac, Florida 33320. through correspondence study. Free informatidn: In- Technical Institute, (Room 13), Box $5,000 Monthly Possible, Proven Mail Order Pro- termountain BIG MAIL gram. Rasmussen DP39, 1747N., 450E., Ogden, UT 258, Jerome, ID 83338. 84404. FINANCIAL AIDS CONSULTATION. Personal RECEIVE MONEYMAKING OPPORTUNITIES. BUSINESS. evaluation may enable you to obtain loans, grants, Your name placed with 2,000. importers, wholesalers, START YOUR OWN WHOLESALE scholarships for college. Free Details. College Ad- manufacturera, etc. Year listing -$1.00 (SAVE $180.00 Details Free. The Mail Sack Dept. C1379, 600 Welch visory Services, 120 Parr Blvd., Richmond. CA Postage!) Advertising Agency, Box 123 -YNA, We- Blvd., Flint, MI 48503. 94804. nonah, NJ 08090. $128.00 In Sales from $12.00 Material. Write: Cew INSTANT MEMORY ... NEW WAY TO REMEM- Company, 533E Wooster Road, Mt. Vernon, Ohio BER. No memorization. Release your PHOTO- BLUEPRINTS. PATTERNS & PLANS 43050. GRAPHIC memory. Stop forgetting! Free informa- "REVEALED!!!" New "Success Guidebook: 1979" tion. Institute of Advanced Thinking. 859DP Via - LINEAR AMPLIFIER DESIGNER KIT: 25 -30 MHz, Lapaz, Pacific Palisades, California 90272. designer -All Incomes Inflation /Recession Foolproofed. $3.00, 125 watts output. Solid -state 12VDC. Each Guaranteed, Amazin,g Free -Information Catalogue: - EASILY IMPROVE YOUR kit contains complete parts list, step -by -step assem- LEARN "HOW TO Only "Vistavision"- Barker, Texas 77413. WRITING" by Dr. Benjanmin White, a university bly instructions and schematic diagram. $19.95. Teach Inc., Box 09468, Send check or money order to DAYSTRUM ENGI- GUARANTEED $480 weekly mailing circulars!!! professor. Send $2.00 to NEERING COMPANY, Box 8869, Stockton, CA 95208. Everything Supplied. Legal. Free Information: Rice Columbus, Ohio 43209. Enterprises -A4, 3000 Montello, Bakersfield. CA 93306. EQUIPMENT & SUPPLIES BOOKS & PERIODICALS ELECTRICAL BUY IT WHOLESALE COMPUTER INTERFACE RF MODULATORS. Video FREE! CATALOG SELF IMPROVEMENT BOOKS. Free Catalog. Phone or 1379, 600 Welch Blvd., Flint, 400,000 BARGAINS Below Wholesale! Many Free! Monitors. TV Cameras. The Mail Sack, Dept. Write. 402- 987 -3771. ATV Research, 13 -E Broadway, MI 48503. Liquidations . Closeouts . Job Lots Single Samples. Free Details Worldwide Bargain - Dakota City, NB 68731. BUSINESS OPPORTUNITIES hunters, Box 730 -IO, Holland, MI 49423. TUBES, some oldies, $1 up; Price, 804 Mosby, 100 -300% Profit- Wholesale 1000's of Items-Giant Abingdon. VA 24210. 703 -628 -7275. BECOME our Mail Order Distributor with $150 Catalog $3.00. Complete Jobber's Program $10.00 PARTS LOCATOR SERVICE. Let us find your investment. Free brochure. Audit Controls, Box D -35, (Refundable). Peko, P.O. Box 5476, Sherman Oaks, hard to get electronic parts. Send ease to: P.O. Box Emerson, NJ 07630. California 91413. 2186, Van Nuys, CA 91404. A -1 Keep BORROW ANY AMOUNT. Enjoy credit. CAMPING EQUIPMENT & TENTS FARMS, ACREAGE F. REAL ESTATE money In bank, get 80% more. Send Stamp. Vernon. Box 75010 -HH, Oklahoma City 73147. NEW! Patented CAR TOP KITCHEN. Information, AVOID PROPERTY TAXES using Federal law. Transworld -3, pictures $1.00. Car Top Kitchens Ltd. Dept. DP139, Details $4. Central Valley Information Service, Box MILLIONS in Mall! Free Secrets. 429, New Berlin, WI 53151. Box 6226, Toledo, OH 43614. Box 15145D, Sacramento, CA 95813. NEW Luxury Car Without Cost! Free details, CB RADIO FOR THE HOME CODEX-A, Box 6073. Toledo, OH 43614. INVISIBLE CB MOBILE ANTENNA. Complete kit PRACTICAL tips for home, garden and workshop 1000% PROFIT Bronzing Baby Shoes. Free Lit- installs INSIDE and turns metal frame of AUTO, can be found in '1001 How -To Ideas." Send $1.50 erature. NBC Box 1904 -DO, Sebring, FL 33870. VAN, WAGON, TRUCK, TRACTOR into efficient for your copy (includes postage) to 1001 How-To antenna. FREE details: send stamped envelope and Ideas, 380 Lexington Ave., New York, NY 10017. HOME! EARN BIG MONEY addressing en- DEPT ESCA. MFC, Inc.. STAY Peter- vehicle make and year. velopes. Genuine offer 10#. Lindco, 3636 -DA, Box 486, East Syracuse, NY 13057. GOVERNMENT SURPLUS son, Chicago 60659. GET a CB Installer's Kit Free! You're just 10 WHOLESALE Rubber Stamp Outfits. Supplies. Cat- days away from making $12 to $25 an hour in your JEEPS - $59.30 -CARS- $33.50! 200,000 ITEMS - alog $1.00. Martin, 14320 Major, Jefferson City, MO spare time. Our self -study CB radio repair course GOVERNMENT SURPLUS -MOST COMPREHENSIVE 65101. can prepare you for a career in electronics. For DIRECTORY AVAILABLE tells how, where to buy - more information call toll free 1- 800 -654 -6785 or YOUR AREA $3.00 MONEYBACK GUARANTEE. - - E3, $500 Monthly Clipping Newspaper items. Experience write CB Radio Repair Course, Inc., Dept. EE -039, Government Information Services. Deparmtent unnecessary. Free Details. American 1108 Colonial, 531 N. Ann Arbor, Oklahoma City, OK 73127. Box 99249, San Francisco, 'CA 94109 (433 California). Inkster, MI 48141. JEEPS!-$49.30- 425.000 Items! Buy In Your Area! DETECTIVES Sur- free! indefinitely! Any- -How! Where! "Professional GUARANTEED BORROW $25,000 interest plus Directory" - $2.00. "Buy Government Lands one! Free report: "Executive I03, Box 368, Buford, TELEPHONE FM WIRELESS MONITOR CON- Guide " -$2.00. "Government Oil -Gas Lottery Guide" GA 30518. NECTS TO ANY PHONE. VOICE OPERATED -$2.00. GSURPLUS, Box 2009 -EEM, Syracuse, NY SWITCH ACTIVATES RECORDER, STEREO, ANY- 13221. BUMPER STICKER PRINTING DEVICE. Cheap, LISTENS Details. Bumper, POB 22791 THING. ELEC'T'RONIC STETHOSCOPE. Simple, Portable. Free TO ANTS WALK, ACOUSTICS AND VIBRATION HYPNOTISM (JT), Tampa, FL 33622 PICK -UP HEAD. SEND $2.00 FOR BROCHURE 125 E. MICHIGAN, SUITE-C, KALA- $30.00 HUNDRED stuffing our circulars into TO AM -TRON, FREE Fascinating Hypnosis Information! Startling! stamped addressed envelopes. No limit. Beginners Kit MAZOO, MICHIGAN 49007. DLMH. Box 487. Anaheim, California 92805. $2.00. Colossi, Box 318 -DC, Brooklyn, NY 11204. DO IT YOURSELF INVENTIONS WANTED MAKE More Money In Mailorder. NACO, Box 846, Nashua, NH 03061. REPAIR TV'S, ANYONE CAN. Easy. Guaranteed. IDEAS,, inventions, new products needed by inno- Free Details. Publication, Box 517E, Brea, CA 92621. vative manufacturers. Marketing assistance available ASSEMBLE products at home. Many opportunities tinkerers, universities, companies with high weekly presently available With- FREE Encyclopedia Winemaking, Beermaking Sup- to individuals, paying profits plies, Equipment, Ingredients. Vynox Industries, Box feasible concepts. Write for Kit -EE, IMI, 701 Smith- out Investment. Businesses, 92 -D2 Brighton 11th, field, Pittsburgh, PA 15222. Brooklyn, NY 11235. / Ir tsren.NY

THERE IS NO CHARGE FOR THE ZIP CODE -PLEASE USE IT IN YOUR CLASSIFIED AD

ELEMENTARY ELECTRONICS /March -April 1979 96 Classified PLACE MOM ...... omit uu. ro be included in the next issue, pelase send order and remittance to R. S. Wayner, ELEMENTARY ELECTRONICS, 380 Lexington Ave., New York, N.Y. 10017

INVENTIONS WANTED- Cont'd MONEYMAKING OPPORTUNITES- Cont'd PERSONAL -Cont'd INVENTIONS, patents, wanted cash, royalty. Auto. $200 WEEKLY stuffing envelopes spare time pos- SURPRISE -send 250 to: Langen, Box 191 -DC, electromechanical, mechanical devices. Housewares, sible. Details, stamped, self -addressed envelope. Mall Downsview, Ontario M3M 3A3. etc. We develop, finance, manufacture and market Sales -I, 8023 Leavenworth Rd., Kansas City, KS from an idea to perfected product. Free evaluation 66109. NEW Luxury Car Without Cost! Free Details. and brochure. Request Kit DP, Pixonic Corporation, Codex -CC, Box 6073, Toledo, OH 43614, 250 West 57th Street, New Yotk, New York 11019. $300 WEEKLY! Home Mailing Program. Details: Thomas, Dept -D1, Box 11773, Charlotte, NC 28220. DATES GALORE! Meet singles- anywhere. Call JEWELRY DATELINE, toll -free (800) 451 -3245. $500 WEEKLY! FANTASTIC HOME MAILORDER PROFITS! (DEALERS WANTED) GRAHAMCO RECORD Telephone conversations privately -auto- COLORFUL 48 page jewelry catalog. $1 refundable. DPBX, 99371 TACOMA, WA 98499, matically. Leave recorder Unattended. Robert's, 2618 Russo, Box 1106 -D, Wayne, NJ 07470. Elmwood Blvd., Wausau, WI 54401. BIG PROFITS In becoming a supplier to major CONFIDENTIAL REPORT. Electronic Surveillance LOANS BY MAIL industry through electroplating small parts and Devices. Send $10.00 -CPS, Attn. Leroy K. Thompson, metalizing non -metallica. Write for free particulars: 5420 N. College Avenue, Indianapolis, Indiana 48220. GET cash grants -from Government. (Never repay.) Mason, Room MC- 107 -IC, 1512 Jarvis, Chicago, IL Also, cash loans available. All ages eligible. Com- 60626 JAPANESE Girls Make Wonderful Wives. We have plete information, $2 (refundable). Surplus Funds- large number of listings. Many interested in mar- DG, 1001 Connecticut, Washington, DC 20036. AMAZING! $265,000 Yearly with classified ads. riage, Only $1.00 brings application, photos, names, Free Proof. Moneycraft, 2316 Dale, Ceres, CA 95307. descriptions, questionaire, Etc. Japan International, BORROW $25.000 "overnight." Any purpose. Keep Box 158 AA, Carnelian Bay, CA 95711. Indefinitely Write: Success Research, Box 29263 -SO, HOW to get paid in advance stuffing envelopes, Indianapolis, IN 46229. make a fortune doing it. Details $1.00. Martin, 3610 A Card Players Dream. 25( to: Langen, Box 191 - Toy, Wisconsin Rapids, WI 54494. DB, Downsview, Ontario M3M 3A3. FINANCING! $1,000 -$50,000 available- "overnight." Entirely by mail. Any purpose. Repay anytime. In- MAILORDER Dealers Wanted. Earn outstanding BEAUTIFUL Mexican -Oriental girls Needing Amer- credibly low interest. No collateral, cosigners, spe- profits. FREE Details. Send SASE: D. Z. Enterprises, ican Boy- Friends. Free Details "actual" photos. cial conditions. Full information, $2 (refundable). Box 408, Erie, PA 16512. World, Box 3878 -DC, San Diego, CA 92103. Spectrum, 79 Wall St. -16F2, New York 10005. $350 WEEKLY MEET SEXY SWINGERS Nationwide. FREE De- Mailing Letters. FREE Details. tails. (State Age). Gateway, Box 338-DC, Lafayette, MACHINERY. TOOLS & SUPPLIES Karmchell, 628FD Cherry, Albany, GA 31701. CO 80026. AMAZING NEW MINI -HOE, steel adjustable rake GUARANTEED big money making program. FREE: 1,000 LADIES PHOTOS. World's largest attachment. HOES weeds: Abraxas Ent., P.O. Box 6072, Evansville, IN 47712. Matrimonial Catalog. Postage /Handling $1.00. Inter - plants, cultivates, with- contact, Box 12, Toronto, Canada M4A 2248. out changing tools. RUSH $1.98 ppd.T. J. WEYMER, HOW TO EARN RD #1, BOX 134 -A, ASHVILLE, money at home mailing com- PA 16613. missior circulars!! Excellent PROFIT potential!! Of- JAPANESE introductions! Girls' photographs, de- fer details -rush stamped addressed envelope 25e. scriptions, brochure, details, $1.00 INTER- PACIFIC, MAGNETS TP Grzywinski, 314 Walnut Ave., Scottsdale, PA Box 304 -SC, Birmingham, MI 48012, 15683. BEAUTIFUL MEXICAN GIRLS! Correspondence. MAGNETS. All types. Specials -20 disc, or 10 bar, HOW Photos, details free! "Latins," Box 1716 -DE, Chula or 2 stick, or 8 assorted magnets, $1.00. Magnets, TO START YOUR OWN CONSOLIDATED Vista, CA 92012. Box 192 -E, Randal)stown, MD 21133. AUCTIONS, GARAGE SALES, FLEA MARKETS. NEW, EXCITING, PROFITABLE /ANYONE CAN DO RADIO & TELEVISION MAIL-ORDER OPPORTUNITIES IT. FREE DETAILS. WRITE TO: SEMCO ENTER- PRISES, DEPT. 25E, 288 SUNDOWN TRAIL, WIL- LIAMSVILLE, NY 14221. TV TUBES 384 each. Send for Free 48 page color BEST Mall Plan Yet. Terrific Sales. Simple in- catalog. Cornell, 4217 -W University, San Diego, Cal- structions. Most anyone can handle. Andy's, POB $500 CASH ADVANCE; ifornia 318, SC 29304. stuff 1000 envelopes. Infor- 92105. Sptbg, mation: SASE. Freedom M145, Box 1060, Orange Park, FL 32073. LINEAR AMPLIFIERS, 25 -100 watt solid state. $500 /THOUSAND immediately, stuffing envelopes, OMNIPOLARIZED BASE ANTENNAS. Portable /mo- free supplies. Rush stamped, addressed envelope. EXCELLENT SECOND INCOME OPPORTUNITY. bile/memory /300 MHZ FREQUENCY COUNTER. L&M Kellander, P.O. Box 25, Talmage, PA 17580. FREE DETAILS. STAMP APPRECIATED. Hanson, Construction plans: $3.00 each, 3/$7.50. Specify fre- 5423 Rushhlll, San Antonio, TX 78228. quency band! Kits available, Free catalog! PANAXIS. EXCITING Excellent Second Income Working. At Box 130 -G3E, Paradise, CA 95969. Home. Free Details. Write: C. T. & S. Enterprses, $4,500 weekly possible, Box 2442 -B, Loves Guarantee, free report. Park, IL 61132. Dept. CMB, P.O. Box 1175E, Pinellas Park, FL 33565. TUBES Oldies, latest. Supplies, components, schematics. Catalog free. (Stamp appreciated), Steinmetz, GREATEST proven moneymaker -Sell First Settlers MAKE 7519 -EE Maplewood, Hammond, IN 46324. of MONEY IN MAIL ORDER. New!, Easy, North America Recipes and keep all proceeds. Exciting. Details free. Publications, Box 235A, Brea, Special Offer. Send $2.00 and SASE -Omega Mail CA 92621. "DISTANCE One Tuber" Handbook -504. 15 Dis- Order, Box 243 Station A, Fredericton, New Bruns- tance one tube plans-25e. Kit catalog 50e. Labora- wick, Canada E3B 4Y9. AMAZING Profits! Woodworking! Information! tories, 1477 -G, Garden Grove, CA 92642. Charles Pollard, 27 Snowhlll, Agincourt, Ontario M1S 3T4. SAVE 50% build your own speaker system. Write MISCELLANEOUS McGee Radio Electronics, 1901 McGee Street, Kansas GET RICH QUICK. You've seen the ads! Fast City, MO 64108. NEWLY developed consumer items of interest to Buck Newsletter analyzes electronic manufacturers. Patents pending. A.I.M.S., the plans. Information VERY Interesting! Next 5 issues $2. Electronics free. Investor's Services, Box 631D, Port Washington, Trader, Folly Beach, SC 29439. 4033 Pleasant, St. Louis, MO 63107. New York 11050. LINEAR Amplifiers 3.5 -30 MHZ. Schematics, De- ANTENNA LIGHT!!! Lights when you transmit! $2000.00 MONTHLY possible stuffing envelopes! De- tailed Instructions For Base BL -200, Mobils BL -100 Slips on tip -$3.95 -Tenalite, Box 879, Mattapoisett, tails, send stamped self -addressed envelope. Craft, and BL -200. All, $6.00. Bomar's, Box 541, Pendleton, MA 02739. Box 3419D, Mission Viejo, CA 92690. SC 29670. FREE! HUNDREDS of things yours, just for ask- YOU could make $3,500 monthly. Free details send FM 2m POCKET Receiver. Long battery life. De- ing. Revealing 62 page report, $2.00. D&W Enter- 154 stamp. George, Box 506, McAllen, TX 78501. tailed assembly /checkout procedure. Plans -64 pages. prises, 13504 Hillendale Drive, Woodbridge, VA 22193. $3.75. ROSA, G.P.O. Box 10435, Hong Kong. $1000 MONTHLY POSSIBLE mailing commission SUCKERS LOSE-PLANNERS WIN. Sure Fire Bar circulars! National, Box 8 -DG, East Rockaway, NY SCIENCE & CHEMISTRY Bets $3.00. Phoenix Books, P.O. Box 17331, Wash- 11518. ington, D.C. 20041. FIREWORKS! Spectacular novelties. Simplified OF INTEREST TO ALL manufacturers textbook. $5.00. Tropic, Box 95M, MONEYMAKING OPPORTUNITIES Palm Bay, FL 32905. ASTONISH your friends with magic, ESP, card $250.00 profit /thousand possible -stuffing- mailing tricks You can do. Details: Langen, Box 191 -DA, SONGWRITERS envelopes. Offer: Rush stamped addressed envelope: Downsview, Ontario M3M 3A3. Universal -ADVS X16180 Fort Lauderdale, FL 33318. SONGWRITERS: Exciting offer -poems, songs need- PEN PALS ed-Free evaluation- Creative Music Productions, Box $180.00 WEEKLY Mailing Circulars. Start im- 1943 -A3, Houston, TX 77001. mediately. Everready, 422A Clermont Ave., Brooklyn, JOIN North America's leading penpal club. Details NY 11238. from Friends Worldwide CP -95/F Anjou, Montreal, START YOUR OWN BUSINESS H1K 405. MAKE YOUR CLASSIFIED AD PAY. Get "How to ARE YOU ABLE to own your business? Evaluate Write A Classified Ad That Pulls." Includes certifi- PERSONAL your aptitude with copyrighted booklet, questionaire. cate worth $2.00 towards a classified ad in this publi- $2.45 plus $0.50 postage. Enrichco 3CJ1, 1023 Fair- lawn, Duncanville, cation. Send $1.50 (plus 254 for postage) to R. S. BEAUTIFUL GIRLS from all continents want cor- TX 75116. Wayner, Davis Publications, Inc., Dept. CL, 380 respondence, Lexington Ave., New York, friendship, marriage. Sample photos NY 10017. free. Hermes -Verlag, Box 110660/D, 1000 Berlin 11, WATCHES. WATCHMAKING & REPAIRING Germany. "WIN thousands! Thoroughbred, Harness, Dog! WATCH and clock repairing books, tools, materials. Guaranteed. Free report. Finish -A, Box 6226, Toledo, SINGLE? Widowed? Divorced? OH 43614." Nationwide Intro- Free Catalog. North American, Box 77, EE51, Fox ductions! Identity, Box 315 -DC, Royal Oak, MI 48068. River Grove, IL 60021,

THERE IS NO CHARGE FOR THE ZIP CODE -PLEASE USE IT IN YOUR CLASSIFIED AD

ELEMENTARY ELECTRONICS /March -April 1979 97 CB Xcvr Checkout Mini Micro Designer Q. Which (Continued from page 72) (Continued front page 61)

remote speakers, L.E.D. digital chan- book exepriments. Either choice brings 512 words magazine has nel indicator, S /RF- output meter, fully 512 words RAM and modulation /VU meter, instant selec- PROM. Versatility. For a truly versatile unit, tion of any channel programmed by you should also go for the accessory selector located on the widest 40- channel preset Memory- Interface Board which mounts the rear apron. directly over the main unit as shown here. The MMD -1 /MI board. com- ROYCE 582 scope of pletely assembled and tested, sells for $179.95 (Royce Electronics Corp.) $250. In kit form, including all parts A 40- channel General Description: for assembly, the price is $194.50. AM remote transceiver for mobile, equipment The MMD -1 /MI offers the follow- P.A. operation. Power supply is 12 ing features: 2K RAM memory capa- to 13.8 'VDC with negative or posi- bility, with 1K supplied; teletype in- test reports? tive ground and 120 VAC. Overall terface (20 MA current loop); paper dimensions are 13/4 -in. H x 6-9/16- tape reader control for ASR33 tele- in. W x 6 -1 /16-in. D. All controls typewriters; audio cassette interface; are on microphone: channel selec- sockets to accept up to 1K PROM or -1 /MI tion, volume, squelch and ANL/ ROM. Addition of the MMD board to the basic MMD -1 Microcom- hi-fi stereo CB selector. S ' RF meter and BUYEFFt S' GUIDE /PA the on -board memory A built into microphone. puter increases speaker are capacity to 2.5K RAM and 1.5K Read it regularly for the PROM or ROM. computer games is what most in consumer audio If playing turns you on, the MMD -1 is not for information and advice. you. But if you want to learn how microcomputers really work, by studying at home at your own pace, the Allow 6 to 8 weeks for delivery of first copy. MMD -1 /Bugbook combination looks unbeatable.

Hi -Fi /Stereo BUYERS' GUIDE ELEMENTARY ELECTRONICS gives you the absolute tops in INDEX TO ADVERTISERS number of equipment test RS.# ADVERTISER PAGE reports per issue. We don't just CIRCLE 71 ON READER SERVICE COUPON test the top of the line, we 4 Active Electronics Standard accessories include a mi- 29 Antenna Incorporated 4935 report on all levels of more 28 Antenna Specialties 15 crophone, DC power cable, auto 26 A.P. Products 17 manufacturers' lines than any- hard- - AMC 86 speaker cables and mounting 103 AVR Electronics 84 one else. 16 ware. 102 Avanti Antennas If you're a Barta 87 5 B & F Enterprises 14 "best -buy" Receiver Section Test: 36 B & K Precision 108 B & K Precision 32 buyer, don't Input sensitivity 0.4 AV Cleveland Institute of Electronics -11 66 dB 6 Cobra miss a single Adjacent channel rejection 8 Continental Specialties CV3 9 Delta Electronics issue! AGC action 11 dB 16 Dinnio lames 26 Input level for S9 25 Digi -Key 89 Mail this coupon to: - Edmund Scientific Co. 92 Hl -Fi / Stereo meter indication 200 µV 2 Eico 22 24 Electronic Book Club 13 BUYERS' GUIDE 110 Electra Company 27 Box 1855 GPO Transmitter Section Test: 12 ETCO .... 89 100 Extron Life Screen 22 New York, NY 10001 _ . _ 3.8 watts AM RF output 13 Finney 24 Modulation to 85% yes - Gilfer 87 Enclosed is $2.98 for 6 issues of HFSBG 107 Godbout 90 (outside U.S.A., possessions send $4.00) Relative sensitivity 104 Grantham College of Engineering .85 1 Heath Company ...... 47, 48 dB Name for 85% mod. -31 109 Hickok ._.. 1 15 Hobby World .. 89 to 100% . yes Address Modulation limited 14 International Crystal 26 - Locksmithing Institute 87 City The 582 has a McGee 86 Editorial Remarks: 105 McKay Dymek 12 State Zip relative reading S- meter, double - N.R.I. Schools 18.21 - National Technical Schools 28 -31 SAVE$2.97 oft regular subscription rate. conversion, connectors for P.A. 17 Non Linear 26 HM C $5.12 newsstand rate. 35 OK Machine & Tool 6 off and remote speakers, L.E.D. 18 PAIA Electronics 22 16 and 5 -step 19 Percom Data Company, Inc. H9BO34 digital channel indicator, 20 Poly Paks 91 S output meter. Can 21 President Electronics 3 L.E.D. /RF- 22 Progressive "Edukits" Inc. 23 utilize auto stereo speakers for CB 38 Projecta Pix 86 34 Quimtronix 92 Please support our monitor when listening to auto radio. - Radio Shack 25 to - Radio Shack CV4 efforts. "Memory control" returns tuning 23 Scientific Systems 90 American when transceiv- 30 Shakespeare 7 the channel selected 39 Southwest Technical 85 Cancer Society was turned off. 101 Techni Tool 87 er 111 Vector 94 98 ELEMENTARY ELECTRONICS /March -April 1979 EVERY PROJECT IN THIS BOOK IS ANOTHER REASON TO OWN CSC'S 61T SOCKETS AND BUS STRIPS.

With QT solderless bread- Variety - 10 models from 70 to 590 solderless boarding sockets and bus strips, tie -points feature snap/lock design to expand or you can contract your breadboard to fit every circuit build twice the projects in and budget requirement. half the time. Because making Versatility- Use with virtually all types of parts, connections or circuit changes is including resistors. capacitors, transistors, DIP's, TO -5's, LED's, transformers, as fast as pushing in relays, -or pulling pots, etc. Most plug -in directly and instantly, out - component leads. No special in seconds. No special jumpers required -just clips or jumpers required, either. lengths of #22 -30 AWG solid hookup wire. When you're building Molded -in holes let you mount QT units circuits securely on any flat surface with 4 -40 flat just for the fun of it, you can take head screws, or 6 -32 self -tapping screws, them apart in minutes -not hours. from behind panel. Economy Sockets are priced as low So you save money by re - as -using parts. $1.75 Save more money by eliminating while eliminating heat damage to heat and mechanical damage to expensive components. Interlocking expensive parts, re -using components. Speed- For fast circuit layouts. QT Sockets and Bus Strips are QT Sockets have 5 interconnecting tie - infinitely expandable, too: start small points per terminal: Bus Strips feature and grow.' breadboards as large as 2 separate rows of interconnecting you wish. terminals. Both connect and disconnect easily, without damage to For as little as $1.75, you can get socket or parts. a lot more out of your time in electronics Visibility All parts are instantly and so why not treat yourself easily visible and accessible, for - to a QT quick signal tracing. circuit analysis Socket today? and diagramming. Durability Higher- temperature 4 - Length -pi - -- Hole- Length Un i sockets with abrasion- resistant, 0- Hole - to-Hole lo-HOIe Ter minasl s - Pr,ce glass -filled plastic. rated better than 100 °C. Screw- down -and- IIIIIIIIIRQT-59S 6.5" 6.2" 118 10.00 interlocked design provides high tIllakallialibilleittiamet.tel OT-59B 6.5" 6.2" 20 2.25 mechanical strength. Reliability- Ruggedly designed MM.OT-47S 5.3" 5.0" 94 8.00 to professional engineering ->;- QT-478 5.3" 5.0" 16 2.00 standards. for heavy day -in,

1 32" day -out use. Non- corrosive _T_ QT-35S 4.1" 3.8" 70 6.00 prestressed nickel -silver contacts INIMMENNIIIM QT-35B 4.1" 3.8" 12 1.75 insure more secure mechanical --r- and electrical connections. Vinyl k MN QT-18S 2.4" 2.1" 36 4.00 backing prevents shorting when mounted on conductive surfaces. QT-12S 1.8" 1.5" Ill 24 3.00 CONTINENTAL SPECIALTIES CORPORATION

IIII QT-8S 1.4" 1.1" 16 2.50 All 01 Loll(' QT-7S 1.3" 1.0" 14 2.25 ,f i° Ihirk ll Corporate Headquarters: Continental Specialties Corporation =070 Fulton Terrace, Box 1942, New = Haven, CT 06509 NEED MORE INFORMATION? CALL TOLLFREE: 351 California St., San Francisco, CA 94104 800-243-6077 to order, or for the name of your local (415) 421-8872, TWX 910 -372 -7992 distributor. Prices slightly higher outside U.S.A. Europe, Africa, Mid -East: CSC UK LTD. Shire Hill Industrial Estate. Units 1 and 2 Saffron Walden, 'Manufacturers suggested list Prices and specifications subject to change without Essex CB 11 3A0 notice Telephone: SAFFRON WALDEN © 1978 Continental Specialties Corporation 21682 Telex: 817477 Canada: Len Finkler Ltd.. Ontario CIRCLE 8 ON READER SERVICE COUPON -!_/1 ,'/i, ,',rem SEVEN RECEIVER

rM I I 1 ßß I N 1 92 1 04

1 1 - AM I 1 I :',' : 6a0 90 Óoo 94

Realistic's System Seven... a new size and shape for stereo

FM in- iniaturizat ion breakthrough! total harmonic distortion) and a even 75 and 300 -ohm pair of our amazing Minimus"-7 puts. U.L. listed, of course, and Realistic's fabulous new System jet -black beauty, elegant speaker systems featuring housed in a stunning Seven combines - metal cabinet with blackout dial. small size and a level of acousti- large -excursion woofers and cal quality you've never heard, soft -dome tweeters in diecast until now, in low -priced book- enclosures only " I /In" high. shelf stereo. . Bass without bulk. Despite its System Seven includes our new small size, System Seven delivers STA AM /FM receiver (10 rich, satisfying bass to 50 Hz and watts per channel, minimum sound levels up to 90 dB for ac- RMS into 8 ohms, 20- 20,000 curate reproduction of anything Hz, with no more than 0.5( , from classical to rock music. a little taller What's the secret? The receiver Receiver is briefcase -sized, than a credit card -just 3 -1/2" high. has a unique equalization net- of two for Each speaker is about the size work engineered especially average books. the speakers. And its switchable so you can use full -size speakers, The price for all this may be the if you wish. surprise of your audio life -only of S39.90 off but no compromises. 239.95", a savings Compact, the -each" price! You get "full- size" high -fidelity System Seven. Small a features with System Seven - Audition At last -true hi -ti perfectly sized for magnetic and aux inputs, tape has never been so beautiful! The 4+ -I 2 -lb. speakers can bookcase. 'Price nla ,.us at individual srnres and dealers. even be used for bookends! monitor, A/B speaker switching,

A Division of Tandy Corporation Sold 0n1l'al nadie IhaeK Fort Worth, Texas -6102 The nationwide supermarket of sound'"