Popular Electronics

Build a Super -Simple Laser Power Supply 48784 Popular Electronics Make a Mac The Electronic Get a better, more expandable machine, Dragonfly and save some cash in the bargain, when Turn pieces of piezo- you build your own Macintosh computer electric film into a fun - to- build, fun -to -use conversation piece All About Receiver Sensitivity Find out what those receiver- sensitivity specs really mean

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rocct Reviews Build the Socket Sentinel onyjo a e A surge -protected, "smart" power strip system, Pulsar that let's you use one device to control 72 -inch up to three others projection TV, and much more What Do Electrical Engineers Do? Is a career as an electrical engineer right for you? After you read this article, you may be better able to answer that question t -L=-s:: . v r-r r C-gn ^ri _i : .t :. . .Ç é-~nifrti:i:1_ -n'z ___ `. _ . _''11_ . __ 09 ;.!_:.!'::.. :, ._ [ r, , }:a 3 NEW .__Pi t?+¡'i!i $2.95 U.S. FactCards Jf7 T.ift' i:..fi $3.75 CANADA IN THIS ISSUE IL i o 09128 4878 7

www.americanradiohistory.comAmericanRadioHistory.Com r 7 Electronics Paperback Books GREAT PAPERBACKS AT SPECIAL PRICES

BP248 -TEST BP267 -HOW TO BP265 -MORE An Ie1rcAYeLCn to BP256 -INTRO TO EQUIPMENT CON- Test Equìn,ont USE OSCILLO- ADVANCED USES taue.n..o.r. and LOUDSPEAKERS Construction OWPr AND STRUCTION n°''"`°0"w om«i.0 SCOPES AND OF THE MULTI - ENCLOSURE $5.95. Details con- OTHER TEST EQUIP- METER $5.95. Use DESIGN $5.95. We struction of simple, in- MENT $6.95. Mas- these techniques to explore the variety of expensive, but ex- tering the oscilloscope test and analyze the enclosure and speaker tremely useful test is not really too difficult. performance of a vari- designs in use today so equipment. AF Gen. This book explains all ety of components. the reader can under- Test Bench Ampl, Au- the standard controls Also see how to build stand the principles in- dio Millivoltmeter, Tran- and functions. Other ad -ons to extend multi- volved. sistor Tester and six equipment is also de- meter capabilities. more. scribed. BP249 BP263 -A CON -'. BP260- CONCISE AConoW -MORE CISE INTRO TO INTRO TO OS /2 tnnoduceontoOS/2 ADVANCED TEST dBASE $6.95. The $5.95. If you are a mul- EQUIPMENT CON- dBASE series of pro- titasking PC user and STRUCTION grams are probably the want to get the most $6.95. Eleven more best known database out of your computer test equipment con- programs for micro- then you must learn its struction projects. OS./2 operating sys- They include a digital 0.)(±,} computers. This book ..6.. is designed to help you tem. This book shows 0512 voltmeter, capacitance get started working you just how to do that. meter, current tracer IIIMRMz.ll IIIY with them. quickly and easily and more. rl PCP102- INTRO- DIGITAL 'BP257-INTRO TO DUCING DIGITAL AU- oiaoeiAmro BP245- BP247 -MORE Protects AUDIO PROJECTS ADVANCED MIDI AMATEUR RADIO DIO $9.95. Covers $5.95. Practical cir- PROJECTS $5.95. $6.95. Amateur is a all kinds of digital re- cuits to build and ex- Circuits included are a nique and fascinating cording methods - periment with. In- MIDI indicator, THRU hobby. This book gives CD, DAT and Sam- cludes A/D converter, box, merge unit, code he newcomer a com- pling. Bridges the gap input amplifier, digital generator, pedal, pro- prehensive and easy to between the technician delay line, compander. grammer, channelizer, understand guide to and the enthusiast. echo effect and more. and analyzer. the subject. Principles and methods are explained.

I 1 PCP108 -COM- COMPUT- L 1 PCP107- DIGITAL BP251- PUTERS AND MUSIC LOGIC GATES AND ER HOBBYISTS $9.95. Explains the FLIP FLOPS HANDBOOK basics of computers $10.00. Thorough $8.95. A wrapup of ev- and music with no pre- treatment of gates and erything the computer vious knowledge of flip -flops for enthusi- hobbyist needs to computers needed. asts, student and tech- know in one easy to Covers types of music nicians. Only a basic use volume. Provides a software and explains knowledge of elec- range of useful refer- how to set up your own tronics is needed. ence material in a sin- computer music stu- gle source. dio.

BP195-INTRODUCTION TO SATELLITE TV $9.95. A definitive introduction to BP239- GETTING THE MOST FROM YOUR MULTIMETER $5.95. Covers the subject written for the professional engineer, electronics enthusiast, Or others basics of analog and digital meters. Methods of component testing includes who want to know more before they buy. 8 x 10 in. transistors, thyristors, resistors, capacitors and other active and passive devices. FOR BEGINNERS $5.50. Power supplies, radio and BP190-ADVANCED ELECTRONIC SECURITY PROJECTS $5.95. Includes a BP97 -IC PROJECTS circuits, oscillators, timers, switches, and more. If you can use a soldering iron passive infra -red detector, a fiber -optic loop alarm, computer-based alarms and an audio you can build these devices. unusual form of ultrasonic intruder detector. BP37 -50 PROJECTS USING RELAYS, SCR'S a TRIACS $5.50. Build pri- BP235 -POWER SELECTOR GUIDE $10.00. Complete guide to semiconduc- ority indicators, light modulators, warning devices, light dimmers and more tor power devices. More than 1000 power handling devices are included. They are RADIO RADIO HOOKUPS Reprint of 1924 booklet presents radio tabulated in alpha-numeric sequency by technical specs. Includes power diodes, LI -100 $3.00. regenerative, neutrodyne, reflex & more. Thyristors, Triacs, Power Transistors and FET's. circuits of the era including

BP234- TRANSISTOR SELECTOR GUIDE $10.00. Companion volume to BP42- SIMPLE LED CIRCUITS $5.50. A large selection of simple applications BP235. Book covers more than 1400 JEDEC. JIS, and brand -specific devices. Also for this simple electronic component. contains listing by case type, and electronic parameters. Includes Dadington Helps the reader transistors, high -voltage devices, high- current devices. high power devices. BP127-HOW TO DESIGN ELECTRONIC PROJECTS $5.75. to put projects together from standard circuit blocks with a minimum of trial and El BP99-MINI-MATRIX BOARD PROJECTS $5.50. Here are 20 useful circuits error. that can be built on a mini -matrix board that is just 24 holes by ten copper -foil strips. BP122 -AUDIO AMPLIFIER CONSTRUCTION $5.75. Construction details for preamps and power amplifiers up through a 100-watt DC- coupled FED amplifier. BP117- PRACTICAL ELECTRONIC BUILDING BLOCKS-Book 1 $5.75. Oscillators, Timers, Noise Generators, Rectifiers, Comparators, Triggers and more. I 1 BP92-CRYSTAL SET CONSTRUCTION $5.50. Everything you need to know about building crystal radio receivers. BP184 -INTRO TO 68000 ASSEMBLY LANGUAGE $6.95. The 68000 is a great new breed of microprocessor. Programming in assembly language increases BP45- PROJECTS IN OPTOELECTRONICS $5.50. Includes infra -red detec- the running speed of your programs. Here's what you need to know. tors, transmitters, modulated light transmission and photographic applications. BP185- ELECTRONIC SYN- BP179- ELECTRONIC CIRCUITS THESIZER CONSTRUCTION $5.95. FOR THE COMPUTER CONTROL OF CHECK OFF Use this book to learn how to build a ROBOTS $7.50. Data and circuits for reasonably low cost, yet worthwhile interfacing the computer to the robot's monophonic synthesizer and learn a lot motors and sensors. THE BOOKS YOU WANT about electronic music synthesis in the i process.

SHIPPING CHARGES IN ELECTRONIC TECHNOLOGY TODAY INC. USA AND CANADA SORRY No orders accepted Number of books ordered I I P.O. Park, 11762 Box 240, Massapequa NY -0240 outside of USA & Canada $0.01 to $5.00 $1.50 $5.01 to $10.00 $2.50 Total price of merehandise $ Name $10.01 to 20.00 $3.50 Sales Tax (New York State Residents only) $ to 30.00 . $4.50 Address $20.01 Shipping (see chart) $ $30.01 to 40.00 $5.50 City State Zip All payments must $40.01 to 50.00 $6.50 Total Enclosed S be in U.S. funds P -991 $50.01 and above $8.00 J

www.americanradiohistory.comAmericanRadioHistory.Com SEPTEMBER 1991, VOLUME 8, NO. 9

Popular ctroiiicS THE MAGAZINE FOR THE ELECTRONICS ACTIVIST! CONSTRUCTION ARTICLES BUILD A SIMPLE LASER POWER SUPPLY Gregory Gray 32 Learn about laser operation with this easy -to- build, low power, laser-tube power-supply circuit THE ELECTRONIC DRAGONFLY Marc Spiwak 55 Make your next project a most unusual one BUILD THE SOCKET SENTINEL Marc Spiwak and John Yacono 63 Control the power to all the components in your A/V or other system using one component's own on /off switch! FEATURE ARTICLES MAKE YOUR OWN MAC .. Elliot Kantor 26 You can build an easily expandable Macintosh with some built -in frills for less than what a new no- frills unit would cost WHAT DO ELECTRICAL ENGINEERS DO? Harry L. Trietley 35 Read this article and find out; maybe you'll also learn if an engineering career is for you INSIDE THE SONY MINI DISC Brian C. Fenton 39 Will Sony's new Mini Disc revolutionize the portable audio industry, or will it simply muddy the waters for years to come? ALL ABOUT RECEIVER SENSITIVITY Joseph J. Carr 61 Learn about the different ways that receiver sensitivity is measured and specified, and what each rating really means PRODUCT REVIEWS GIZMO 43 Including: Sony Portable Shortwave Receiving System, Design Acoustics Video Speakers, and much more HANDS -ON REPORT 66 OWI WAO ll Mobile Robot Kit PRODUCT TEST REPORT Len Feldman 68 Pulsar TVP 2000 "Prodigy" Projection TV Receiver COLUMNS THINK TANK John Yacono 18 Controlling power COMPUTER BITS Jeff Holtzman 70 The 386 revolution continues ANTIQUE RADIO Marc Ellis 72 The theremin: A first look inside CIRCUIT CIRCUS Charles D. Rakes 74 Detector circuits, and more FUN SOFTWARE Fred Blechman 80 Flying with the best SCANNER SCENE Marc Saxon 82 Preparing for stormy weather DX LISTENING .. Don Jensen 84 Shortwave radio: It no laughing matter HAM RADIO Joseph J. Carr 86 A random walk through the technical mailbag DEPARTMENTS EDITORIAL Carl Laron 2 LETTERS 4 ELECTRONICS LIBRARY 6 NEW PRODUCTS 14 FACTCARDS 41 FREE INFORMATION CARD 60 ADVERTISER'S INDEX 98

Popular Electronics (ISSN 1042 -170X) Published monthly by Gemsback Publications, Inc., 500-13 Bi -County Boulevard, Farmingdale, NY 11735. Second -Class postage paid at Farmingdale, NY and at additional mailing offices. One -year, twelve issues, subscription rate U.S. and possessions $21.95, Canada $28.84 (includes G.S.T. Canadian Goods and Services Tax Registration No. R125166280), all other countries $29.45. Subscription orders payable in U.S. funds only, International Postal Money Order, or check drawn on a U.S. bank. U.S. single copy pace $2.95. (0 1991 by Gernsback Publications, Inc. All rights reserved. Hands-on Electronics and Gizmo trademarks are registered in U.S. and Canada by Gernsback Publications, Inc. Popular Electronics trademark is registered in U.S. and Canada by Electronics Technology Today, Inc. and is licensed to Gernsback Publications, Inc. Printed in U.S.A.

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A stamped sell- addressed envelope must accompany all submitted manuscripts and/or artwork or photographs if their return ís desired should they be rejected. We disclaim any responsibility for the loss or damage of manuscripts and/or artwork or photographs while in our possession or otherwise.

As a service to readers, Popular Electronics publishes available plans or information relating to newsworthy products, techniques, and scientific and technological developments. Because of possible variances in the quality and condition of materials and workmanship used by readers, Popular Electronics disclaims any responsibility for the safe and proper functioning of reader -built projects based upon or from plans or information published in this magazine.

www.americanradiohistory.comAmericanRadioHistory.Com Popular Electronics EDITORIAL Larry Steckler EHF: CET Editor -In -Chief and Publisher EDITORIAL DEPARTMENT THE DIGITAL GUESSING GAME Carl Laron The lines are being drawn for a battle that seems sure to Editor Robert A. Young reshape the home -recording marketplace. We don't know who Associate Editor will win, but it's a good bet that at least some consumers will John J. Yacono be among the losers. Associate Editor Byron G. Wels, K2AVB Associate Editor To bring you up to date: For years, the Philips- developed Teri Scadute compact cassette has been the dominant medium for home Assistant Editor Kathy Terenzi recording and for portable audio. While that medium is not Editorial Assistant without significant flaws (a high noise level, for one), its Marc Spiwak convenience has made it an overwhelming success, at least Editorial Associate Fred Blechman among non -audiophiles. Joseph J. Carr, K4IPV Marc Ellis Len Feldman Its success was so complete that compact cassettes even Jeffrey K. Holtzman withstood the introduction of the CD. Using digital techniques, Don Jensen Charles D. Rakes that non -recordable medium offered audio quality that could Marc Saxon not be matched by tape or vinyl. CD's soon replaced records Contributing Editors on the shelves of most stores, but they did not replace PRODUCTION DEPARTMENT compact cassettes. For many consumers, the compact Ruby M. Yee Production Director cassette's convenience, especially for portable use, was more Karen S. Brown important than the CD's superior sound quality. Production Manager Marcella Amoroso Production Assistant Perceiving a need that may or may not exist, the electronics Janice Box industry began to look for a new product -one that would Editorial Production combine CD -like sound with compact- cassette -like ART DEPARTMENT convenience and recordability. The first entry was digital audio Andre Duzant Art Director tape (DAT), an audiophile -quality product with a price tag to Injae Lee match. Then, this past winter, Philips introduced the more Illustrator modestly priced digital compact cassette (DCC). Now, Sony Russell C. Truelson Illustrator has announced a third recordable digital medium, the Mini

Jacqueline P. Cheeseboro Disc (MD). For a full report on the MD, turn to page 39. Circulation Director Michele Torrillo The stage is now set for a three -sided format war beginning P-E Bookstore sometime next year when DCC and MD hardware arrives on BUSINESS AND EDITORIAL OFFICES stores' shelves. All three formats have their advantages, and Gernsback Publications, Inc. drawbacks, so only time will tell which will survive; although if 500 -B Bi- County Blvd. Farmingdale, NY 11735 consumer confusion (not to mention the fear of getting stuck 1- 516-293 -3000 with obsolete and non -supported hardware) is high enough, Fax: 1-516-293-3115 President: Larry Steckler it's possible that ultimately none may make it. Customer Service /Order Entry 1- 800-435 -0715 The consumer-electronics graveyard is filled with products that In IL 1 -800- 892-0753 though highly touted at first, failed due to consumer apathy, 7:30 AM - 8:30 PM EST consumer confusion, inadequate marketing, or just poor Advertising Sales offices listed on page 98 performance. Whether DAT, DCC, and /or MD will join the Cover photography by Elliot Kanter quadriphonic amplifier, the 8 -track tape deck, the CED /VHD Composition by videodisc player, and the Beta VCR in the backs of unlucky Mates Graphics consumer's closets is still anyone's guess.

ABThe Audit Bureau of Circulation

The publisher has no knowledge of any proprietary rights Carl Laron which will be violated by the making or using of any items disclosed in this issue. Editor

2 www.americanradiohistory.comAmericanRadioHistory.Com .is

We Have QUALITY PARTS We Have DISCOUNT PRICES We SHIP FAST kJ:5:D Highest Quality Metal TOUCH DIMMER INFRARED SECURITY LIGHT (AS -IS) C -60 Cassettes (Erased) The "brain" Electriko # SIL -101 - Experiment with infrared sensors with these outdoor security lights. Contain lots of interesting Premium quality metal part of the components, and IR detector, photoresistor, relay, tape In C -60 cassettes "LITE transformer. IC's. voltage regulator, capacitors, trimpats (30 min. per side). One 0730 TOUCH" and other goodies. Returned to the distrbutor for variety of the finest "brand -name" touch dimmer, !.:1"-T7147-1! of reasons, we've found that most of them work to some tapes on market, in _ when connected to any lamp, will turn it on the extent. We don't want to test them and would prefer to durable, clear plastic transport mechanisms. and off and change the brightness level when sell them "as-is" at a greatly reduced price. Mounts to any Recorded and bulk erased, the record- protect any metal part is touched. We don't have the standard electrical junction box. Infrared sensor detects tabs have been removed and therefore, need to wiring harness that originally connected this movement up to 65 feet and turns on lights. Sensor can be be taped over to re- record. Audiophiles will ap- to the lamp, but we can provide a simple adjusted for sensitivity and duration of lighting. The position preciate the wide dynamic range of this tape. If hook -up diagram and instruction sheet. The of the sockets and the infrared sensor can be easily adjusted. your cassette deck has a "metal" setting you will solid-state circuitry is contained in a thermo- Will handle two 150 watt PAR 38 lamps. Suitable for wet locations. hear the difference. A real bargain) plastic box 1.91" X 111" X 0.835 ". Bulbs not included.CAT# IL -101 $7.50 each CAT# C -60M $1.25 each 10 for $10.00 CAT* DMR -1 $3.50 each SWITCHES PHOTOFLASH HALL EFFECT SENSOR P.C. RELAYS KITS Dip P.C. CAPACITOR The following Pushbutton Microswnch #SS41 L.E.D. FLASHER KIT ITT Schadow Digfast relays all have Rubicon CE Tiny, solid state switch Series SE p.c. pins for Two L.E.D.'s flash in , i _ 0- 210 Mfd reacts Instantly to S.P.D.T. momentary 330 Volt both input and bater a9volt photoflash proximity of magnetic field. pushbutton. Mounts in output as well battery attached. capacitor. Operates at extremely high speeds. up to 14 pin DIP configuration. l as quick -connect terminals This kit includes a 0.79 dia 100 khz. Case size: 0.12" X 0.17" X 0.06" Designed for low current switching appli- on the output. 1.5" X 1.05 p.c. board, all the parts X 1.1" high. These thick. 4.5 Vdc to 24 Vdc supply voltage. are new X 1.08 ". UL 8 CSA listed. and instructions to make a simple flash- cations. Grey keycap is 0.68" X 067". 10 ma. sink type digital output. Operating capacitors that have been er circuit. A quick and easy project for CAT it PB -28 $1.00 each gauss - 15 to 40. P.C. leads. prepped with 1.4" black and 12 Vde, SPDT anyone with basic soldering skills. 10 for $9.50 100 for $85.00 CAT# HESW -2 75c each 10 for $6.50 red wire leads soldered to the Potter 8 Brumfield # CATS LEDKIT kit Pushbutton Switch 100 for $60.00 1000 for $500.00 $1.75 per terminals. CATS PPC -210 T91R5D22.t2 -02 SMK Manufacturing LE.D. CHASER KIT $1.25 each 10 for $11.00 12 Vdc, 155 ohm coil. 0.47" square black pushbutton. 100 for $100.00 Normally open contacts rat- Build this variable SPST normally open. 4 p.c. pins 3 1/2" DISKETTES Large quantities available. ed 20 anps.Normatly closed speed led chaser. for mounting. Ideal for low current íLE6;li>i:x Call for pricing. contacts rated 10 amps. 10 leds flash switching applications. CATS P8 -29 Quality, double-sided -040, 3 1/2' diskettes. These CATS RLY -31 $2.50 each sequentially at - 5 for $1.00. 100 for $15.00 RECHARGEABLE diskettes were recorded, 10 for $22.50 whatever speed Rotary BCD Switch but never used. Flip the you set them for. EECO # 2310 -02G (11NÍ BATTERIES write -protect tab to off 12 Vdc, SPST N. O. Easy to build kit Includes pc board. BCD 10 position position and use for your Potter d Brumfield # parts and instructions. Ideal for special rotary switch. DIP configuration fits In own data storage T91R5D22-12.01 lighting effects, costumes, etc. Oper- standard 8 pin I.C. socket. Right angle 6 Volt I Amp/Hour at a fraction of the cost of new diskettes. 12 Vdc, 155 ohm coil, ates on 3 to 9 volts. PC board is 5" X style. Screwdriver actuation. 0.42" cube. Japan Storage Battery Co. CAT# DTS-1 $1.00 each 10 for $9.00 S.P.S.T. normally open con- 2.25". A great one hour project. CATS RDIP -2 $1.75 each Portalac tacts rated 30 amps. CATS AEC $6.50 each 10 for $16.00. 100 for $145.00 # PE6V1 AUDIO SLIDE POT CATS RLY-32 $2.00 each STEPPING MOTOR 6 Volt 1 Ah 10 for $18.00 Miniature Toggles rechargeable CONTROLLER KIT Rated: Dual 1K audio. 3 amps @ 120 Vac sealed lead -acid 3 1/2" long. 2 1/2" slide Learn about S.P.D. T. (ON -ON) P.C. mount (gell cell). 2" X 1.635" X 2" ht. L.E.D.'s CAT# ASP -1 KD stepping CAT# MTS -4PC $1.00 each Batteries are prepped with 5" Reduced to 505 each motors while 10 $9.00- Standard JUMBO for 100 for $80.00 black and red leads terminat- 100 for $40.00 T 1 building this ed with 2 pin connector. Diffused -3/4 size (5 mm) S.P.D.T. (ON -ON) solder lugs simple circuit. CATS GC -61 $4.75 each CAT# MTS-4 $1.35 each Includes circuit board, stepping motor 10 for $42.50 I.E.C. POWER CORD 10 for $12.50 - 160 for $110.00 RED C ED -1 and all parts except 12 Vdc power D.P.D.T. (ON -ON) solder tugs Nickel -Cad 10 for $t.50. 100 for $13.00 supply. CATS SMKIT $18.00 each CAT# MTS-8 $7.75 ea. 10 for $15.00 GREEN CATS LED -2 METRONOME KIT 10 D.P.D. T. (ON -ON) P.C. mount for $2.00. 100 for $17.00 CAT# MTS -APC $2.00 ea. 10 for $17.50 YELLOW CAT# LED-3 10 for $2.00 100 for $17.00 AAA SIZE $1.50 each TELEPHONE KEYPAD 6 foot BLACK, SPH -386 jack to 3 prong FLASHING LED 1.2 volts 180 mAh molded A.C. plug. Fits most computers, W/ built in flashing circuit 12 CAT# NCB -AAA button telephone - - computer terminals and test equipment. E 5 volt operation. T 1-3/4 This simple device can be set to click keypad. Ivory finish. C C; AA SIZE $2.00 each CATS LCAC-C6 $3.00 each G.F (5mm) from 20 to 1,000 beats per minute. 2.83"x2.2"s0.58 "thick. 1.25 volts 500 mAh fa E E EE Easy to build, includes circuit board, all Matrix encoded. CATS NCB -AA RED $1.00 each Ideal for telephone or E Ç FLASH ASSEMBLY components and instructions. Oper- AA SIZE $2.20 each CATS LED-4 10 for $9.50 security keypad. --- ates on a 9 volt battery (not included). WITH SOLDER TABS New compact flash GREEN $1.00 each METRO CAT # KPT -1 $1.00 each 10 for $9.00 CATS $3.75 each CAT* CB -SAA assemby from a CAT* LED -4G 10 for $9.50 U.S. manufacturer C SIZE $4.25 each of YELLOW $1.00 each PHOTO RESISTOR OPTO -SENSOR cameras. Operates 1.2 volts 1200 mAh CAT# LED -4V 10 for $9.50 TRW /Optron A OPB5447.2 1,000 ohms bright light. CATS NCB -C on 3 Vdc and measures IR /sensor in 16K ohms dark. emitter pair 2 1/2" x 1 1/4". Ideal for use as a strobe. LED HOLDER Rectangular package with D SIZE $4.50 each warning light or attention getter. Includes 0.182" dia. X .08"high. 0.18" long leads. 28" color coded leads. 1.2 volts 1200 mAh hook -up diagram. CATS FSH -1 $3.75 each Two piece holder. a a CATS PRE -7 2 for $1.00 CATS OSR-4 2 for $1.00 CATS NCB -D 10 for $35.00 100 for $325.00 CAT# HLED 10 for 65c 100 for $45.00 1000 for $400.00 ORDER TOLL FREE 1- 800 -826 -5432 FAX (818) 781 -2653 INFORMATION (818) 904 -0524 DISCOVER Call Or Write For Our Minimum Order$10.00 All Orders Can Be Charged To Visa, Mastercard Or Discovercard Checks and Money Orders Accepted By Mail California, Add V/SA Free 64 Page Catalog Sales Tax Shipping And Handling $3.50 for the 48 Continental United States - Outside the U.S.A. send $2.00 All Others Including Alaska, Hawaii, P.R. And Canada Must Pay Full Shipping postage for a catalog. Quantities Limited No C.O.D. Prices Subject to change without notice. MAIL ORDERS TO: ALL ELECTRONICS CORP P.O. BOX 567 VAN NUYS, CA 91408

CIRCLE 10 ON FREE INFORMATION CARD www.americanradiohistory.comAmericanRadioHistory.Com JUMPING SHIP?

Since 1966, except for a brief LETTERS period several years ago when you tried to emulate a computer

magazine, I have been a faithful subscriber to Popular Elec-

tronics because I enjoyed the electronic articles and projects, That depends on the project. the wording of the problem rules is a staggering task. There and columns such as Think We have no control over parts leads me to believe that are even legal and insurance Tank, Circuit Circus, etc. suppliers. Sometimes parts and whoever wrote the article implications: A fire or electrocu- However, I have a bone to boards are available for years; doesn't understand how to wire tion after performing your own pick with you. If I want to read other times, just a few months. a service entrance box. home wiring could result in a about computer language and Your best bet is to do your The author stated, "A figure shift of liability from the home- game software, such as fea- research before you buy any- illustrating how the hookup is owner's insurance carrier to the tured in your Computer Bits and thing, starting with the supplier done shows the hot wires con- homeowner. Is the risk worth it? Fun Software columns, I will buy of the board and any spe- nected to breakers that are on Hire a professional electrician and read computer magazines! cialized parts.- Editor top of one another -that is, on to evaluate and install equip- I do not want to read computer the same side of the incoming ment like this. The service articles in my electronics maga- A HANDY PROJECT line- rather than across from entrance is no hobbyist or zines, unless they are electronic one another." With rare excep- weekend -mechanic proving projects such as "A Telephone - Each month, Popular Elec- tion, all modern main panels are ground. It is hazardous to your Operated Switch for your Com- tronics comes up with several set up with a staggered main health. puter." interesting projects, including bus, which mechanically puts L.E.Y. Have you opened the door to those in Think Tank and Circuit two full -size adjacent breakers Cincinnati, OH become just another computer Circus. About the best and on opposite sides of the line. magazine, as you did a few You're right. The installation in- handiest project I have seen in The exception that should be years ago? Is your memory so structions were, indeed, correct. a long time was Charles Rakes' pointed out is the possibility of short that you do not realize that We couldn't see the internal "Sure-Luck Ohms" in the April someone mistaking a Pig- a second transition to a comput- structure of our service panel, 1991 issue. It's a great work- gyback breaker, or two slim er magazine will end as it did and made incorrect assump- bench addition. I was going to breakers found in some G.E. with your first transition, when tions based on what we could hard -wire the project, but I was and similar boxes, as "adjacent most of your subscribers des- see. We still installed the Elec- glad that I sent for the PC board breakers." While they are cer- erted you? tro Guard correctly, however, (quite a few wires). I've worn out tainly beside each other, they If you insist on being comput- because we measured for 240 two or three Radio Shack re- are on the same side of the line. er- oriented, I will join the throng volts between two convenient sistor color code decoders. I can only hope that the Electro that will say "Aloha Oe" to Pop- breakers on opposite sides of (Even with the decoder, it some- Guard manual is correct in its ular Electronics for the the box before we proceeded times requires a calculator.) pictorial diagram, because that second, and probably final, with the installation. You are With the Sure -Luck Ohms Box is what most people will tend to time. also correct in saying that a you just twist three knobs to use. A.L.M. professional electrician wouldn't match the colors on the resistor, Personally, if I were to use Honolulu, Hl make our mistake, and we like press a button, and, presto, you such a device, I would use the your suggestion about installing Have no fear, the transistion you have the value of the resistor red /black indicated wires on a the Electro Guard across a 240 - speak about was done under a shown in lights. If you know the 240 -volt breaker so that when volt breaker. However; the Elec- previous ownership, and is a value you want, but don't know the device trips or is turned off, tro Guard is sold as a move that we have no plans of the colors, just turn the knobs both sides of the Electro Guard consumer-installable device (al- duplicating. We will continue to until the correct value lights up, would be disconnected. The beit with suggestions that a cover computer software as it is and you automatically have the possibility to back-feed one 120 - professional may be needed). A a topic that many electronics colors required. volt circuit with the other side of hobbyist who is knowledgeable hobbyists find interesting, but The box is sitting by my the line under some conditions about safety precautions, and is we don't anticipate expanding DMM, and I know I will get could exist internally in the de- careful to follow them, should that coverage beyond what you much use from it. vice. be able to install the Electro currently see.- Editor B.M. Finally, I would like to point Guard without any problems. - Gold Bar; WA out what I consider a major Chris E. O'Brian PARTS AVAILABILITY? philosophical question regarding electronics hobbyists ELECTRO GUARD I've reading repairing working their MORE ON SIGNALS been Popular Elec- INSTALLATION or on tronics for a few years now, own home wiring. As the old FROM SPACE

and I really like the projects that Thank you for a fine magazine, saying goes, "A little knowledge

appear in its pages. But I won- in general. However, I must is a dangerous thing." I am not The hope of finding exceptions

der about the longevity of point out an error in the May calling your readers dumb. I am to known physical laws springs

availability of parts and circuit 1991 Gizmo section that I feel sure many of them could whip eternal. Remember the efforts boards for those projects. should never have been made my socks off in the knowledge to read paranormal implications

Sometimes I look back at proj- by someone qualified to write in department. However, it is very into Kirlian photographs? Now, ects in older issues thinking Popular Electronics. hard even for most people in my the talk of signals from space

that, if I could still get the parts A product called Electro business (professional electri- through a previously unknown

and boards, I would like to build Guard was reviewed, and an cians) to keep up with this medium seems to fall into the them. alleged error in their installation equipment and how it should be same category.

R.W.B. procedure was pointed out. I connected. Just learning the The author of the April article, Richmond, CA have not seen their manual, but N.E.C. requirements and local Are We Receiving Biological

www.americanradiohistory.comAmericanRadioHistory.Com Signals from Outer Space ?," modulation, can only be charac- HAVES AND NEEDS Bay area can help me find old suffers from no doubts. He terized as noise, inasmuch as it but working test gear it would I have an Eico model 322 signal claims outright that experiments is irregular but conveys no infor- be most appreciated. generator, serial number 10448, have "... confirmed the exis- mation. Would highly intelligent Edward J Matthews that was used only a few times. tence of biological signals as a bei-1gs use noise as a carrier? 402 Broadway #42 I'm looking for a service manual new, non -electromagnetic real- Above all, regardless of the San Francisco, CA 94133 for the instrument, and would ity." scanning method used, how is appreciate any help in finding Here, the term "biological sig- a picture derived without benefit one. Thank you. nals" is used in a sense quite of separately distinguishable I am trying to locate a Reticon Darrell Crimmins different from its usual use in timing or clock signals? That analog delay chip-either 6025 NW Westside Road existent extensive literature, violates information theory; you SAD -512 or SAD -1024- neither McMinnville, OR 97128 wherein it has nothing at all to can't get more out of a signal of which is still in production. do with signals from space. But thafl you put in. I have a visually impaired friend The SAD -1024 was sold at one that is a minor point. The real Finally, the fact that image who is looking for instructions time by Radio Shack as part question is does the author enhancement brings out images on how to invert the video on a #276 -1761. If anyone knows present enough proof to confirm is scarcely convincing. There black- and -white video camera. where I can purchase either or what it is that he means to say. are patterns in any kind of disor- The solution would need to be a both of these devices, please Unfortunately, his exposition der. Think of the "man in the switch, so that he could go contact me. Thank you. is rather muddy. How do the moon" the "great stone face," between normal and inverted Richard Marshall experimenters know that the the canals on Mars, etc. (Statis- and get the most readable im- P.O. Box 3256 sensors are not responding to ticians brand any purportedly age. White type on a black Easton, PA 18043 electrical or micro -climatic influ- random series of numbers as background is easier to see. ences? And what in the world is actually non -random if runs do The switch would be handy meant by "pictures" expanding not occur.) when the type is already re- Do you have a question, comment, as they travel through space? It takes a true believer to versed to white on black. complaint, or compliment about Does that mean that only a conclude, in the face of all this, Mark McMahan something you've read in Popular small detail of the whole picture that a vague likeness of an arm P.O. Box 1163 Electronics? Then why not write to: can be decoded because of the in an image suggests that the Jamestown, NC 27282-1163 small area of the detectors human form is the standard of Letters used? Furthermore, if the signal the universe. Popular Electronics Magazine 500 -B Bi- County Blvd. is distinguished only by "dis- Cr is the whole article an I am a partially disabled veteran Farmingdale, NY 11735 crete intensity modulations," Apr I Fool's put -on? and I'm trying to set up my own then the carrier, which con- W.C. test bench. If any of my fellow We're waiting to hear from you! tinues between periods of Beverly Hills, CA readers in the San Francisco

12" Subwoofer Box 12" Pioneer Subwoofer 800 Hz Horn 18" Eminence Woofer Professional driver for use in auditorium and studio sound systems. Giant 100 oz. magnet. 250 watts RMS, 350 ¡D PIONEER' watts max power The perfect high volume cabinet 12" super duty, dual voice coil Piezo midrange/tweeter driver unit. handling capability. subwoofer. 30 oz. magnet, 2" voice for dual voice coil subwoofers. Response: 800 -20 KHz. Power handling fs= 30 Hz, OMS= coil. 100 watts RMS, 145 watts max Box comes with pre -cut woofer capability: 20-30 volts (approximately 50 3.17, QES= .373. power handling capability. 6 and port holes. Cabinet volume: ohm watts RMS). Sensitivity: 93 dB, 2.83V/1 M. OTS= .33, impedance (4 and 8 ohm compatible). 2 cu. ft. with dual ports. Charcoal 4" round. Motorola #KSN1066. VAS= 10.5 cu ft. Sensitivity: 89 dB 1W/1M. Response: carpet. Dimensions: 13" (H) x 13" SPL= 95 dB 1W/1M. 25 -700 Hz. QTS= .31, VAS= 10.3 cu ft. (D) x 30" (W). Net weight: 29 lbs. 270 $2395 Net weight: 29 lbs. Net weight: 6 lbs. Pioneer #A3OGU30-55D. #PK- -085 $2530 EMINENCE (1-3) (4-up) 0= 6° #PK- 290 -200 $9980 $9340 #PK- 260 -495 Each #PK -290 -145 $39 $3680 (1-3) (4 -up) (1 -3) (4 -up) Subwoofer Crossover Network 12" Pyle Woofer 5 -1/2" Cone Midrange NEW Super duty, 200 watt RMS REVISED power handling capability. Original Sanyo high CATALOG end system midrange. Designed specially for dual Large 5" paper cone voice coil subwoofer with gold look dust cap. systems. 12 dB per Heavy 12 oz. magnet. octave roll -off at 1" ferro fluid cooled 150 Hz into 8 ohms. voice coil. 50 watts Crossover also features RMS, 75 watts max. a set of outputs 12 ". 70 oz. magnet woofer. 2 -1/2" voice for use with your existing speaker system. Network is coil 105 watts RMS, 155 watts max Sanyo part #S12H10. Net weight: 1-1/2 lbs. SA YO totally passive, requiring no power source of its own. power handling capability. $395 #PK- 292 -050 $6290$5980 #PK- 281 -100 #PK- 260 -220 $2860 $2495 (1 -9) (10 -up) (1 -5) (6 -up) (1 -5) (6 -up)

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Maybe we're not keeping him inductances affect the circuits. tracked. Numbered steps and Secrets Of RF busy enough with his Ham Ra- In addition, resistance isn't the concise explanations make it dio column and all the feature same in RF circuits as in DC easy to work through the book Circuit Design articles he writes for Popular and low- frequency AC circuits. without much page- turning, re- Electronics. Joe Carr some- Finally, RF- measuring instru- reading, and flipping through by Joseph J. Carr how manages to find the time to ments are both more expensive indexes. write books that are as practical and more complex. In each chapter, new com- and clear as his magazine Carr uses non -technical lan- mands and procedures are pieces. In this book, he pre- guage to explain what RF is, described briefly, and then num- sents experiments and real-life how it works, how it differs from bered steps guide readers applications that make radio - other electromagnetic frequen- through the required keystrokes frequency circuit theory crystal - cies, how to build some of your or mouse actions. Illustrations clear. own instruments. His book Many electronics enthusiasts covers everything from anten- consider that part of the elec- nas to transistors, including how WINDOWS'3 tromagnetic spectrum known as to repair variable capacitors, OuickStcrrt cope with electromagnetic interference, and align RF circuits. It also explains how to build a digital frequency- counter module, design and wind inductor coils, and design and build RF- amplifier and preselector circuits and simple wire antennas. OWMb '>... .. In addition, the book teaches the basics of receiver operation, the proper use and repair of components in RF circuits, and the principles of radio -signal show how the screen should propagation from low frequen- appear, and some procedures cies to microwaves. are followed by tips or cautions Secrets of RF Circuit Design about using that feature of the costs $19.95 and is published program. The book begins with Inc., by TAB Books Blue Ridge an overview of Windows and Summit, PA 17294 -0850; Tel. directions on how to use Win- 1- 800 -233 -1128. dows menus and dialog boxes, CIRCLE 98 ON FREE and then explains how other INFORMATION CARD Windows programs -including Windows Write and Windows Paintbrush -work. It explains CIRCUIT WINDOWS 3 how to use the Program Man- QUICKSTART: ager to keep related programs The Step -by -Step and documents together so DESIGN Approach they can be easily located; how by Ron Person and Karen Rose to use the File manager to copy and erase files, create directo- Surveys and controlled studies ries, and format diskettes; and have shown that Windows pro- how to use the Clipboard to grams make personal copy and paste work. The book the radio -frequency band to be computers more accessible to describes how to control the somewhat mysterious, for a users of all levels of experience, printer, use the personal -pro- number of reasons. First, RF and this book aims to make ductivity programs that come formulas and circuits don't Windows 3 more accessible to free with Windows, and how to seem to work the same on the same audience. The step - create macros to automate pro- paper as they do on the bench by -step instructions include only cedures. It also shows how to because at such high frequen- the most important issues, so run multiple non -Windows pro- cies stray capacitances and that readers don't get side- grams, and how to copy and

www.americanradiohistory.comAmericanRadioHistory.Com Why take chances in today's job market? Graduate as a fully trained electronics professional. To get ahead and stay ahead in today's be sure it will be reviewed, graded and needed to work with state-of- the -art economy, you need the electronics returned with the appropriate instruc- equipment of today and tomorrow. training CIE has been providing its tional help, you get it fast and in writing New Courses! ' 150,000 -plus successful graduates from the faculty technical specialist best CIE now offers two new career courses: with for nearly 60 years. qualified to answer your question in Automotive Electronics and Computer terms you can understand. Meet the Electronics Specialists. Operation and Programming. When you pick an electronics school, Pick the pace that's right for you. CIE offers you an Associate Degree. you're getting ready to invest time and CIE understands people need to learn at One of the best credentials you can have money. And your whole future depends their own pace. There's no pressure to in electronics or any other career field on the education you receive in return. keep up...no slow learners hold you back. - is a college degree. That's why That's why it makes - CIE so much sense If you're a beginner, you start with the offers an Associate in Applied Science to go with number one... with the basics. If you already know some electro- in Electronics Engineering Technology. specialists... with CIE! nics, you move ahead to your own level. And all CIE career courses earn credit There's no such "Same Day" toward your degrees. thing as a bargain grading cycle. Which CIE training fits you? education. When we Beginner? Intermediate? Advanced? If you talk to some receive your CIE home study courses are designed of our graduates, lesson, we for ambitious people at all entry levels. and we recom- grade it and People who have: No previous mend you do, mail it back the electronics knowledge, but do have chances are same day. You an interest in it; Some basic knowledge you'd find a lot find out quickly or experience in electronics; In -depth of them shopped how well you're working experience or prior training in around for their doing! electronics. training. Not for State -of- the -art At CIE you start where you fit and the lowest priced, laboratory feel comfortable where start, then go but for the best you equipment. on from there to your Diploma, Associate training available. Some courses Degree and career! They pretty much feature the CIE knew what was Today is the day. Send now. Microprocessor available when they picked CIE as Fill in and return the postage-paid card Training Laboratory. An integral part of number one. attached. If some ambitious person has computers, microprocessor technology already removed it, cut out and mail the Because we're specialists we have to is used in many phases of business, coupon below. You'll get a FREE CIE stay ahead. including service and manufacturing school catalog, plus complete informa- At CIE we have a position of leadership industries. The MTL gives you the tion on independent home study. Mail to maintain. Here are just a few of the opportunity to program it and interface it in the coupon below or, if you prefer, ways we hang onto it... with LED displays, memory devices and switches. You'll gain all the experience call toll -free 1- 800 -321 -2155 (in Ohio, Programmed Learning. 1- 800 -523 -9109). That's exactly what happens with CIE's Auto -Programmed Lessons®. Each lesson uses famous "programmed r AH1 6 learning" methods to teach you import- YES! I want to get started. Send me my CIE school catalog including details ant electronics principles. You explore about the Associate Degree program. (For your convenience, CIE will have a them, master them completely, before representative contact you there is no obligation.) you start to apply them. You thoroughly - understand each step before you go on Print Name to the next. You learn at your own pace. And, beyond theory, some courses Address Apt. come fully equipped with electronics equipment to actually let you perform City State Zip hundreds of hands -on experiments. Age Area Code /Phone No ) Experienced specialists work closely with you. Check box for G.I. Bulletin on Educational Benefits O Veteran 0 Active Duty Even though you study at home, CIE's faculty and staff stand ready to assist via CLEVELAND INSTITUTE OF %. A school of thousands. CIE's toll free number. And, each time ELECTRONICS, INC. A class of one. you return a completed exam you can 1'76 East 17th Street Cleveland. Ohio 44114 (216) 781-9400 e Since 1934.

www.americanradiohistory.comAmericanRadioHistory.Com paste data and graphics from provides technicians and hob- A practical appendix includes one program to another. byists with a working knowledge exercises, operation manuals, Windows 3 QuickStart: The of the equipment that produces sources of information, a com- Step -by -Step Approach costs the signals, so that they will be plete glossary, operation $19.95 and is published by Que able to fully define signal guidelines for recording with Corporation, 11711 North Col- characteristics. It presents a de- Nagra, and an historical per- lege Avenue, Suite 140, Carmel, tailed study of signal analysis as spective on sound technology. IN 46032; Tel: 1- 317 -573 -2500. it applies to the operation and The Mechanics of Sound Re- CIRCLE 89 ON FREE signal-generating capacities of cording costs $40.00 and is INFORMATION CARD today's advanced electronic de- published by Prentice Hall, En- vices. The test -equipment glewood Cliffs, NJ 07632; Tel: section describes spectrum 201 -767 -5937. 65 WAYS TO SAVE TIME analyzers, digital- storage os- CIRCLE 99 ON FREE INFORMATION CARD AND MONEY cilloscopes, logic analyzers, DESIGNING AND high -end multimeters, and fre- TESTING TODAY'S quency counters. Various comparators, digital multi - ELECTRONICS transmission media are ex- meters, power supplies, video THE MIDI MANUAL from Global Specialties plored, including fiber -optics test instruments, signal and by David Miles Huber analysis, AM- and FM- stereo function generators, component Ten new products are featured modulation and demodulation, testers, probes, and accesso- The musical instrument digital in this 36 -page catalog of elec- vectors, and a broad spectrum ries. The catalog provides interface -MIDI -has had quite tronic testing and prototyping study of television antennas. complete specifications in con- an impact on electronic musical equipment. Those include a The book takes a detailed look venient comparison charts and instruments, as is evident in the ten -instrument -in -one handheld at satellite earth terminals, in- in detailed listings. Key features techniques and production multimeter, three logic- analyzer cluding the latest developments are summarized, along with se- styles of modern music, live test kits, and a digitally syn- in C and Ku bands; low -noise lected product specifications. stage production, video, and thesized function generator. The block -down converters; and a For each major product catego- film. Thanks to MIDI, computers catalog also contains complete 1.2 -meter reflector for use with ry, the catalog provides a are now musical tools. As the Ku -band video, voice, and data glossary of terms. A full line of MIDI 1.0 specification enters its (;.f; 7 i, is second decade, this book intro- tïluc traffic. The book covers mono- accessories also described. i 11;;:h /.1¢ 81iuuLti' phonic and stereophonic Test Instruments BK-91 is free duces readers to the latest LVS1011111(2 audio-C-QUAM AM- stereo upon request from B&K- Preci- industry and advances, and / 11 77r'NtÌ/7(? L' 1 - transmission and reception, sion, Maxtec International thoroughly covers the basics of L7_-tietllcs Bessel functions and tables, Corp., 6470 West Cortland MIDI technology. Written as an ,harmonic distortion, and stereo Street, Chicago, IL 60635; Tel: all- around guide to this popular separation -all illustrated with 312 -889 -1448. technical -art form, the book spectrum -analyzed waveforms. CIRCLE 87 ON FREE gives a close -up look at the INFORMATION CARD Also covered are multiple and industries top products. Illustra- satellite- master antenna sys- tions and step -by -step lessons tems, and the latest show readers how to set up an developments in analog color - efficient MIDI system. The book television systems. It examines THE MECHANICS OF explains MIDI components, today's automotive electronics, SOUND RECORDING functions, and fundamentals; including conventional dis- by Tony Zaza explores MIDI's full range of descriptions and specifications tributors, fuel injections, turbos, production techniques; looks at Devoted to the creative use of for complete lines of bread- and superchargers. the science of synchronization the for narrative boards and prototyping cards, Electronic Signals and Sys- sound track and the art of sequencing; and meters, frequency counters, tems: Television, Stereo, purposes, this book covers the describes how to combine MIDI entire technical process of film function generators, power sup- Satellite TV, and Automotive and sync -pulse timing. and video location plies, oscilloscopes, logic test costs $19.95 and is published and studio The MIDI manual costs work. It to readers instruments, and enclosures. by TAB Books Inc., Blue Ridge aims prepare $24.95 and is published by to solve recording problems by 65 Ways to Save Time and Summit, PA 17294 -0850; Tel. Sams, 11711 North College Ave- applying the proper use of the Money Designing and Testing 1- 800-233 -1128. nue, Suite 140, Carmel, IN recorder and the intel- Today's Electronics is free upon CIRCLE 98 ON FREE basic 46032; Tel: 800 -628 -7360. INFORMATION CARD ligent placement professional request from Global Spe- of CIRCLE 86 ON FREE microphones. The book illus- INFORMATION CARD cialities, 70 Fulton Terrace, New trates how sound is linked to the Haven, CT 06512; Tel: INSTRUMENTS process and storytelling func- 800 -572 -1028. TEST CIRCLE 88 ON FREE BK -91 tions of a production. State -of- SATELLITE TV AND INFORMATION CARD from B &K-Precision the -art equipment and facilities SMATV: for sound generation and ma- Books, Videos & Instruments for such applica- nipulation are described, along Software ELECTRONIC SIGNALS tions as engineering, with the complexities of audio from Baylin Publications AND SYSTEMS maintenance and repair, field post -production with an empha- by Stan Prentiss service, education, production sis on the mix. The book is This catalog offers an assort- line testing, research and de- organized in a series of chap- ment of books dealing with A true understanding of elec- velopment, and quality -control ters that stand alone as satellite television and satellite tronic signals requires more programs are featured in this "modular units." Each chapter master -antenna TV (SMATV), than simply illustrating wave- 68 -page catalog. 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Because battery performance settings on the Power Base, clip py -disk and hard -drive directly affects the performance on the Power Top, and drop in a configurations. Both include of a wide range of portable battery. A green light indicates high -resolution VGA graphics, a electronic gear -including lap- that battery is ready-up to five voice- message option, a two - tops, camcorders, and cellular times faster than conventional button mouse, two joystick con- phones -it is important for con- trickle chargers. Power Tops are nectors, microphone and sumers to keep their currently available for the Sony stereo -headphone jacks, and a rechargeable batteries in top Handycam camcorder and sev- real -time clock with battery condition. The Surecharge eral popular cellular phones backup. Because all internal Ni -Cd Charger Power System's patented cir- (the Motorola PT-500 and 8000 components are designed to cuitry ensures that Ni -Cd Series, the Mitsubishi 3000/Dia- Conditioner batteries deliver 100% of their mondTel 99X, the OKI 700/750, rated energy every time they and the NEC P300). More tops are used. It also corrects and will be available by the end of eliminates battery capacity the year, including one for the Toshiba line of laptop computers. The Power System, which includes the universal base and one interchangeable top, has a suggested retail price of less than $150. Additional tops will function without the need for a retail for under $40. For further fan, the system runs cooler and information, contact Surecharge quieter than most other comput- Industries Inc., 278 East 1st ers. The hard -drive version Avenue, Vancouver, BC, Cana- comes with 1MB RAM and a da V5T 1A6; Tel: 609 -876 -6710 40MB hard drive. It is factory or 800-661-4405. loaded with the DeskMate and CIRCLE 101 ON FREE DeskMate Home Organizer INFORMATION CARD software, MS-DOS operating system, and a comprehensive demo program with voice, mu- HOME COMPUTER sic, and photographs. The floppy -disk and hard - The second generation of drive versions of the 1000 RLX Tandy's popular home computer home computer cost $799.95 is represented by the 1000 RLX, and $1199.95, respectively. which combines the home -man- Monochrome and color agement tools of the original monitors are additional. The 1000 RL plus the power of an system is available at participat- office PC. The 1000 RLX offers ing Radio Shack Computer the extra power of a 10 -MHz Centers and Stores nationwide. 80286 processor and a 3.5 -inch For more information, contact 1.44MB floppy -disk drive, and a Tandy Corporation, 700 One problems. According to Sure - second 3.5 -inch drive bay will Tandy Center, Fort Worth, TX charge, battery life will be accept either a floppy -disk drive 76102. extended to 2000 cycles, the or a 20MB or 40MB hard -drive CIRCLE 102 ON FREE equivalent of more than five option. The system also has INFORMATION CARD years of daily use. one PC- compatible expansion The Power System consists slot. The system still comes of a "universal" base and inter- with Tandy's DeskMate and DUAL -DRIVER changeable tops. The base DeskMate Home Organizer's 24 POWERED SUBWOOFER houses the Discovery Battery- easy-to -use home management Conditioning System tech- applications, but also handles The key to M &Ks MX-70 com- nology, which can be set to the bigger jobs normally left in pact subwoofer's high accommodate a range of Ni -Cd the office. Built -in tutorials, pull - performance is its push -pull battery voltages and capacities. down menus, and pop -up dialog dual- driver configuration, which By switching tops, one base boxes, along with the point -and- virtually eliminates even -order can condition and rapid- charge click convenience of a mouse, harmonic distortion through a the batteries used in a variety of make it quick and easy to per- novel cancellation technique. portable electronic equipment. form tasks. Although it measures only 18 x You simply adjust the switch The 1000 RLX comes in flop- 101/2 x 131/4 inches, the sub-

www.americanradiohistory.comAmericanRadioHistory.Com woofer contains two high - with a single adjustment. Con- meters, each accurate to within performance subwoofer drivers servatively rated, the 1651 will 2.5 %. The compact instrument and an internal 125 -watt rms deliver maximum power output weighs 101/2 pounds. power amplifier. One driver is in continuous operation without The Model 1651 triple- output mounted conventionally on the overheating. Four methods of DC power supply has a sug- cabinet's front baffle. The sec- protection-reverse polarity, gested price of $395. For ond driver, however, is located overload, short- circuit, and cur- further information, contact inverted on the cabinet's bot- rent- limiting protection -guard B &K- Precision, Maxtec Interna- tom. The front of its cone faces tion. Series operation doubles the power supply from damage tional Corp., 6470 West the inside of the cabinet, with output to a maximum of 48 by accidental abuse. Current Cortland Street, Chicago, IL the back side of the cone, mag- volts, while parallel delivers up limiting is infinitely variable from 60635; Tel: 312- 889 -1448; Fax: net, and frame exposed. Each to 1 -amp output. In either con- 0 to 500 mA with automatic 312-794 -9740. cone is always in the exact figuration, autotracking provides recovery. For convenience, the CIRCLE 104 ON FREE opposite position in its travel voltage control of both supplies 1651 has separate volt and amp INFORMATION CARD relative to the other. The push - pull technique increases the

Major Manufacturer Service and Repair subwoofer's efficiency in comparison to a single 8- inch -driver subwoofer, equivalent to dou- Documentation bling the amplifier's power. Those features, combined with the MX -70's large magnet and voice coil, make the subwoofer SAMS, the leading source for service and repair capable of low distortion and dynamic, detailed musical out- documentation and manufacturers' schematics, offers you put even at very high output comprehensive coverage of a wide range of products. levels at low frequencies. De- signed for either horizontal or vertical installation, the MS -70 cabinet features rounded side TVs (PHOTOFAGR ) Tape Recorders edges and a separate grille for each speaker. VCRs Transistor Radios The MX -70 powered sub - Computers Modular Hi -Fi woofer has a suggested retail price of $795. For more infor- Citizen Band Radios Videodisc Players mation, contact Miller & Kreisel (M &K) Sound Corporation, Scanners Disc Drives 10391 Jefferson Blvd., Culver City, CA 90232; Tel: Automobile Radios Monitors 213 -204 -2854; Fax: 213 -202 -8782. CIRCLE 103 ON FREE INFORMATION CARD Overnight Delivery Available

TRIPLE- OUTPUT TRACKING DC POWER See your local Electronics Distributor SUPPLY or call SAMS at 1- 800 -428 -7267 and ask Designed to power a mix of for Operator RE-1. analog and digital circuitry, B &K-Precision's model 1651 is essentially three power supplies HOWARD W SAMS & COMPANY in one -two variable 24 -volt, 0.5 -A supplies, plus a fixed 5- 2647 Waterfront Parkway East Drive, Suite 300 volt, 4 -amp supply. To supply Indianapolis, Indiana 46214 -2012 greater voltage or current needs, the 24 -volt supplies are switch -selectable for series, parallel, or independent opera- CIRCLE 5 ON FREE INFORMATION CARD 15 www.americanradiohistory.comAmericanRadioHistory.Com generate gate and trigger func- whether the listener is sitting or Protel Easytrax 2' tions, has an overall frequency - standing) and are integrated by counter range of 0.1 Hz to 10 a 24 -dB /octave crossover net- Outstanding value in Printed Circuit Board /CAD MHz, and includes a built -in work. Performance parameters for your Macintosh and PC oscilloscope that can produce include a frequency response of burst waves from 1 ms to 10 s. It 55 Hz -20 kHz ( - 3 dB and Protel Easytrax 2 is a new. low -cost design package for PC and -in linear/ 10 dB at 45 and 34 Hz, Macintosh users that includes everything required to produce also features a built - professional quality Printed Circuit Board artwork. logarithmic sweep function, a respectively), and typical listen- built -in amplitude -modulation ing -room sensitivity of 86 dB at Our easy -to -learn menu -driven design system breaks the 'expert circuit with suppressed- carrier one meter with 2.83 -volt input. harrier' - you'll he designing in minutes, not hours. Our To encourage bi- wiring, the comprehensive tutorials guide you through the program's extensive loudspeaker includes dual "five - features that take the tedium out of hoard layout. way," gold -plated binding post Comprehensive library of Through -hole devices sets. The Stratus Mini's tongue - - Gerber photoplotting and N/C drill tapes and- groove cabinet features On- the -tly library components creation sides, front, and back that are Intelligent Pad to Pad autorouting jointed by heavy-gauge aluminum extrusions to enhance Switchable Metric /Imperial grid rigidity. The optional matching Auto -panning mode, a VCG function for exter- stands place the speakers at PostScript nal control of output frequency, optimal listening height. Powerful user -definable Macros and a GCV function that will The Stratus Mini speaker sys- Independent print /plot program generate voltage in proportion tem has a suggested retail price to frequency. Variable waveform of $800 /pair; the PSB Mini Multi -layer hoards of up to 32 X 32 inches. symmetries can also be gener- Stands cost approximately At Protel, we offer free technical support, 24 BBS. -day -hour and 30 ated. The sweep function $200 /pair. For additional infor- money hack guarantee. Prices start at generator measures mation, contact PSB 102/5 x 33/4 x 111/4 inches and International Inc., 633 Granite Free Evaluation Package $450 weighs nine pounds. Court, Pickering, Ontario, Cana- Toll Free: 800 -544 -4186 The Model B -810 sweep func- da L1W 3K1. tion generator costs $895. For CIRCLE 107 ON FREE INFORMATION CARD Prote! Technology, Inc. further information, contact Pro - 50 Airport Parkway, San Jose, CA 95110 tek, P.O. Box 59, Norwood, NJ 07648; Tel: 201 -767 -7242; Fax: Tel: 408437 -7771 Fax: 4084374913 TELEPHONE FILTERS 201 -767 -7343. CIRCLE 11 ON FREE INFORMATION CARD CIRCLE 106 ON FREE INFORMATION CARD Designed to meet FCC and European requirements, LAPTOP PHONE LINK tems. The compact (21/2 ounce, Coilcrafts EMI Filters quickly 33/4 x 13/5 x 11/8-inch) stand -alone COMPACT SPEAKER and easily eliminate elec- Now any telephone, including unit requires no software or ex- SYSTEM tromagnetic interference (EMI) those connected to a PBX or ternal power, making it from telephone lines. The in -line digital system, can be used for especially convenient for busi- Designed for either free- stand- filter modules provide better communication through a ness travel. ing use or to be augmented by than 30 -dB attenuation of EMI modem or fax. Solecteks Lap- The Laptop Phone Link has a a subwoofer, PSB Speakers' over the 5 -kHz to 10 -MHz range top Phone Link connects any suggested retail price of Stratus Mini is a compact, high - (20 -dB attenuation from 100 fax or modem -equipped desk- $119.95. A second model, de- performance two -way system. kHz to 110 MHz). Isolation is top, laptop, or notebook signed for use with modems or Its 3/4 -inch aluminum dome computer directly to any office faxes that require line voltage, tweeter and long -throw 61/2-inch or hotel phone system without comes with an AC adapter and mid /bass driver are arranged in requiring a dedicated telephone features automatic voice /data an unusual "woofer-over" array line. It attaches to the standard switching; it has a suggested (the tweeter is placed below the RJ11 connector on the phone retail price of $149.95. For more mid /bass unit to ensure that handset, and works on both information, contact Solectek response remains unchanged analog and digital phone sys- Corporation, 6370 Nancy Ridge Drive, Suite 109, San Diego, CA 92121; Tel: 800 -437 -1518 or 619 -450 -1220. CIRCLE 105 ON FREE INFORMATION CARD 1000 volts between windings, and DC resistance per winding is 65 megohms. The EMI filters SWEEP FUNCTION are available in 2- or 4 -line GENERATOR versions for RJ -11, RJ -14, and RJ -45 cables. One end plugs Incorporating features generally into the line or handset, while a found in more expensive equip- jack at the other end receives ment, Proteks Model B -810 the cable. sweep function generator offers The four-line RJ -14 filters cost a frequency scan of 0.1 Hz to 10 less than $12 each in 500 quan- MHz in nine ranges. It can tities. For further information,

16 www.americanradiohistory.comAmericanRadioHistory.Com contact Coilcraft, 1102 Silver tact ACE Communications, Earn Your B.S. Degree Lake Road, Cary, IL 60013; Tel: Monitor Division, 10707 East 708 -639 -6400. 106th Street, Indianapolis, IN in CIRCLE 109 ON FREE 46256; Tel: 317 -842 -7115; Fax: ELECTRONICS INFORMATION CARD 317 -849 -8794. CIRCLE 110 ON FREE or INFORMATION CARD WIDE -BAND ANTENNA COMPUTERS

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www.americanradiohistory.comAmericanRadioHistory.Com THINK TANK

By John J. Yacono Well, another month is boy riding a rocking horse flows through the gate of upon us and with it a and next to that, there's a the Triac, turning it on. The batch of new circuits. As wagon and a tricycle. Triac then allows current to always, all the circuit After 3 years, the cars pass from the AC source to Controlling creators whose work ap- keep coming from all over your light display. pears in this month's and line up outside to A couple of technical tips Power column will receive a Think watch and film the display. are in order at this point. Tank ll book. Send your sub- It does get somewhat em- First, be sure that you power missions to Think Tank, barrassing, what with all the the 4017's from a 10 -volt Popular Electronics, 500 -B traffic and jokes about the source to ensure that the Bi- County Blvd., Farm- drain on the electricity, but optoisolators will activate ingdale, NY 11735. kids of all ages like what good and hard. Second, My topic for this month, they see. be sure not to confuse the

optoisolators, was prom- Up to now I have been two main terminals on the pted by a comment made using 555 timers with relays Triac (the terminals that go by John Caywood (Think and Triacs to sequentially to the AC source and the Tank, August 1991) who ex- supply power to the lights. lamps) with one another: pressed an interest in The circuit is so large that it The main terminal drawn power -control devices, and takes up two circuit boards near the gate should al- by a request made in our that contain a total of elev- ways go to the power first letter for this month. en 555's with their support source, the other terminal After we deal with op- components, relays, etc. should go to the load. Third, toisolators, I'll answer a I've wanted to replace the select Triacs that can han- couple of other letters. relays with solid -state com- dle the current required for ponents and reduce the your displays (use heat sinks A CHRISTMAS DISPLAY overall number of compo- if necessary). Last, when- Every year, I set up a nents. Well, your ever working with AC -power large animated Christmas - "Multiplexing with Counters" circuits observe extreme light display in my front circuits (Think Tank, May (make that obsessive) cau-

yard. How big? Well one of 1991) are just what I need, I tion. Never work on such the displays is shaped like a think. My question is what circuits while they are under 6 by 7 -foot present com- would be the best way to power and use heavy - control AC with the 4017 gauge Romex wire for all

R2 U1 counters? power connections. Use MOC3010 R1 FROM 680 SZ 6 2200 -Bill J. Stern, Sistersville, wire nuts wherever possible 4017 o vos o OUTPUT TO STRING WV in the AC circuit. solder OF LIGHTS TR1' It's really pretty simple to melts when passing high control the lights in your current. TO AC 2 4 1 } POWER display. What you need to The optoisolator circuit 'SEE TEXT do is connect an op- presented in Fig. 1 will not toisolator Fig. 1. A Triac- output optoisolator used with a Triac will allow a at each output of work well with highly induc- 4017 decade divider to control an AC load, such as a string of each 4017. Then connect tive loads. That's because lights. the optoisolator to a Triac an inductive load will not that will actually control permit the current and volt- plete with a large bow on each light circuit. age flowing through the top. The lights are se- To see exactly how that Triac to fall to zero at the quenced so that the bow should be done, take a same time. That prevents goes out and the next set of look at Fig. 1. Since the 4017 the Triac from turning off lights, shaped like an open is a CMOS chip, any one of once the LED turns off. For lid, comes on. When the lid its outputs can supply those of you that would like turns on, a 4 -foot rabbit enough current to light an to use such optoisolators to complete with a drum and LED in an optoisolator. The power inductive loads, try trumpet appears. As the optoisolator contains a the circuit in Fig. 2. The extra rabbit waves and beats the light- activated Triac driver, capacitor and resistor help drum, musical notes ap- so when the LED turns on, to overcome the effects of pear around the the Triac driver conducts a the inductive load, allowing instruments. There is also a little current. That current the Triac to turn off.

www.americanradiohistory.comAmericanRadioHistory.Com FROM U1 4017 R1 F3 INDUCTIVE MOC3010 OUTPUT 22052 2.4K LOAD 6 O VA 000 `--o R2 1 Safety, 680 St C1 TRI' TO AC 4 POWER Security,

'SEETEXT

Fig. 2. For controlling an inductive load, the basic circu t in Convenience, Fig. I needs to be augmented with an additional resistor and capacitor. Without the extra components, the Triac may not turn off. entertainment and Energy There are many other DARLINGTON types of optoisolators (in OUTPUT fact, too numerous to cover Management all of them here); each with its own special properties and uses. For example, some optoisolators are Home Automation equipped with transistor outputs (or drivers), as from Heath, Fig. 4. A Darlington- output in Fig. 3. They are shown op oisolator has a harder the catalog useful when you want one ac ion. It runs fully on even DC circuit to control an- if the LED only glows dimly. that has it all... other. You may be wondering why one wouldn't just conduct at its maximum Enter the world of use a transistor. Well, there capability even if the LED Home Automation. Remote are times when the control only glows dimly. That's lighting and appliance controls. circuit must have separate useful for applications that Security alarms and lighting. voltage -supply and ground require high sensitivity and/ Automated thermostats. lines from the circuit that it's or fast action. Video monitoring systems. controlling. A transistor -driv- Another common op- Whole -house security systems. er optoisolator allows the tcisolator sports an SCR They're all yours in the Heath LED and the transistor drive output (See Fig. 5). That SCR Home Automation Catalog. To to reside in completely sep- acts like any other SCR, but receive your FREE copy, arate circuits. it's a light- activated SCR (or LASCR). It turns on when the call today toll -free. LED packaged with it glows. TRANSISTOR OUTPUT As you probably know, SCR's act like diodes that can be 1-800-44-HF.ATH turned on. When turned on, (1-8004443284) they allow current to flow in ti only one direction. Once turned on, they latch -they will continue to allow cur- H(IVF_ rent to flow until the current f U1 ,A ICI' Fig. 3. Transistor- output ti. r,v: i drops to a low value. That optoisolators are useful to a1 makes these optoisolators ®I_. n 011tl allow one DC circuit to L!a: control another. That allows you to separate the grounds SCR OUTPUT of the two circuits.

Closely akin to the transistor- output optoisolator is the Darlington- output optoisolator (see Fig. 4). They are also useful when you Fig. 5. Optoisolators with want to isolate one DC cir- SCR outputs latch on. Once cuit from another, but they activated, the only way to Heath Company provide "snappier" action. turn them off is to prevent Marketing Dept. 107 -090 To put that way, another the current from flowing through Benton Harbor, MI 49022 output will snap on and the SCR. CL-807R1

CIRCLE 17 ON FREE INFORMATION CARD 19

www.americanradiohistory.comAmericanRadioHistory.Com contact east very nice for alarm circuits. and hobbyists to try to emu- Same Day Shipment Once triggered they latch late their example. In that To OMA, Call (508) 6621000 on to sound an alarm, and respect, that means that if they isolate any sensitive you introduce an imped- detection circuits from the ance in one side of the line, electrically noisy annun- a corresponding imped- ciator. ance should be added to the other side. Along similar AC INPUT lines, the tip and ring lines should be opened by contacts in both lines simultaneously except at the terminal equipment. *"-h. ( DR VER Since the FCC has per- mitted private individuals to connect all sorts of equip- FREE CATALOG Fig. 6. AC -input optoisolator ment to telephone lines, TEST INSTRUMENTS & devices contain two HARD -TO -FIND TOOLS oppositely oriented LED's. there has been a gradual the degradation of the total Packed with over 10,000 quality products for testing, One of LED's will light repairing, and assembling electronic equipment. A full no matter which direction the network by poorly designed selection of test instruments, power protection equip- current Bows. equipment. A good exam- ment, precision hand tools, tool kits, soldering supple is to listen to the plies, and much more. Products are shown in full color with detailed descriptions and pricing. All products Some optoisolators have transmission of some porta- come with a 100% satisfaction guarantee. SAME - the ability to accept an AC ble telephones. The cross- DAY shipment program. control signal. Take a look talk and noise introduced In a hurry to receive your catalog? at Fig. 6 to see how that is by them affects all of the Call (800) 225 -5370 done. There are two LED's users of the network. In Massachusetts call (508) 682 -2000 placed back -to -back at the Both the 500 -ohm re- Contact East, Inc., Dept. R470 input. One LED will be for- sistors in each leg of Mr. 335 Willow St., No. Andover, MA 01845 ward biased and glow Grabosky's circuit can be when current flows in one replaced by a small induc- CIRCLE 7 ON FREE INFORMATION CARD direction, and the other LED tor, about 500 -mH, in series will glow when the current with a 100 -ohm resistor. That reverses. This variety of op- should improve the sound toisolator is useful when you quality of the circuit. Be an FCC don't know the polarity of -Ted LeBaron, Ft. Myers, the control signal, or when FL LICENSED you want an AC signal I applaud your defense ELECTRONIC TECHNICIAN! (such as audio -controlled of the telephone company current) to activate a de- standards, I agree that any vice. device connected to the phone line should obey A "BALANCED" every FCC and telephone - Earn up to PRESENTATION. company rule, and anyone $30 an hour and more! This is in regard to Mr. connecting devices to the Grabosky's contribution telephone lines should vl,ßrr t Learn at home in spare time. (Think Tank, June 1991) and make every effort to study No previous experience needed! your reply thereto, Mr. Gra- and adhere to the stan- No costly school. No commuting to class. bosky's use of a 500 -ohm dards. However, Mr. The Original Home -Study course prepares you for the "FCC Commercial Radio- resistor in each line feeding Grabosky's circuit didn't telephone License." This valuable license is power to his telephone (see connect to the phone line, your professional "ticket" to thousands of Fig. 7) is correct. Telephone and cannot be prone to exciting jobs in Communications, Radio - TV, Microwave, Maritime, Radar, Avionics companies go to great ex- crosstalk (it contained only and more...even start your own business! pense to keep the tip and one voice channel). Be that You don't need a college degree to qualify, ring leads of the talking as it may, thank you for but you do need an FCC License. paths balanced through all pointing out a very impor- No Need to Quit Your Job or Go To School This proven course is easy, fast and low of their equipment, includ- tant issue. I hope everyone cost! GUARANTEED PASS You get your ing the cables leading up appreciates your point. FCC License or money refunded. Send for FREE facts now. MAIL COUPON TODAY! to the customers' premises. That is done to prevent CLEARING UP SOME commanD PRODUCTIOnS crosstalk and noise from NOISE. FCC LICENSE TRAINING, Dept. 100 P.O. Box 2824, San Francisco, CA 94126 degrading the entire net- The April 1991 Think Tank Please rush FREE details immediately! work. In that context, it featured a white -noise gen- NAME behooves all experimenters erator circuit from Bob ADDRESS CITY STATE ZIP

www.americanradiohistory.comAmericanRadioHistory.Com McVay. While I am sure that it is a perfectly fine circuit, I The World's Most Popular Probe would like to address your comments concerning the use of the device for audio equalization. White noise - which contains equal energy per hertz -is not used to equalize audio. What is needed is pink noise, which contains equal energy per octave. White noise can be converted to pink noise by passing it through a pinking filter, which attenuates the white noise by 3 dB per octave to achieve the desired equal energy per Mode SP100 Free probe guide shows economical octave. replacements for Tektronix. H -P. 100 MHz Switchable lx-10x .... An easy method for set- $45 Philips and all others ting an equalizer with a More SP100 Probes Have Been Sold Worldwide Than pink -noise generator in- Any Other Probe Ever Made volves using a hand -held Universal Economical sound -level meter (such as For Tektronix, Hewlett Packard, Substantial savings compared to the one from Radio Shack). Philips, Leader, B &K, Kikusui, OEM probes You start by lowering all the Hitachi, Beckman and other 10 day return policy equalizer's faders all the oscilloscopes Guaranteed performance and quality way down. Feed the pink noise through the audio sys- TE . _! Tpi 9178 Brown Deer Road, San Diego, CA 92121 tem to the speakers and Toll Free 1- 800 -368 -5719 raise the middle fader to its PROBES. INC. middle (zero) position. Ad- just the volume of the audio CIRCLE 18 ON FREE INFORMATION CARD system so that the sound meter reads 0 dB. That sets filter. First send the white - fused, so you're quite right. three -volt battery pack, a reference point to mea- noise generator's output (I guess I was the only one which is more practical sure the other octaves into one channel of a making noise that month!) than using household elec- against, so don't alter the graphic equalizer. Then set Thanks for the lips for using tricity. volume level for the rest of the lowest fader to its max- both white and pink noise. Transistors Q1 and Q2 are the procedure. Lower the imum- output position. Now configured (as a center fader back down. adjust all successive faders NOTHING BOX Darlington) to amplify the

Now take the lowest so that each one is 3 dB I built this circuit (see Fig. signal coming in from the fader and raise it up until lower than the one preced- 8) so that I could watch my speaker terminals. The sig- the sound meter reads 0 ing it. Do the same with the music as well as hear it. Ifs nal from the Darlington dB. Write down its position other channel and you're nothing more than a toy amplifier is fed through re- on a piece of paper and done. and has no practical value sistor ladder, with the resistor lower the fader back down. -Steven Weiss, Sunrise FL that I can find. It uses very junctions feeding the base Perform this procedure with You got me! It is obvious ordinary parts, and for a terminals of ten NPN tran- all the remaining faders, That I got my noises con- power supply I used a sistors. Once turned on, the writing down the position of transistors will light the LED's. each that produced a As the signal from the reading 0 dB. When speaker increases, the LED's of R1 finished, set each fader to D1 5008 light in sequence. I used a the position you recorded T1 1N4001 5 WATT bargraph unit for the LED's. and you're done. Re- FL1 18V At very loud musical pas- member, due to the sages, all the circuit's LED's interaction between the light up. sections of the equalizer, As I said, there isn't a the quality of your results GREEN practical value for this unit, will depend on the quality but the aesthetics more of your equalizer. than make up for it. However, Mr. McVay's cir- Fig. 7. The telephone intercom has two resistors in it to balance -David L!tke, St cuit can be used to set an the circuit. This seems unnecessary, but it is a technique used by Catherines, Ontario, equalizer without a pinking phone companies to reduce cross -talk. Canada

www.americanradiohistory.comAmericanRadioHistory.Com AM TO SPEAKER o 1M This circuit (which is shown R4 TERMINALS R5 D1 1K 1K in Fig. 10) is really quite 2N2222 simple and it is also easy to assemble. +3V 05 06 07 You won't have to etch 2N2222 2N2222 2N2222 2N2222 2N2222 PC boards, or even use +3V rg, perfboard. Simple, point -to-

LEDI LED2 LED3 EO4 LED5 point wiring is sufficient. I O soldered my wiring directly D2 to the transistor leads. Here's 2N2222 R6 = R7 R8 R9 R10 how the water detector 1K - 1K 1K 1K 1K Mw 1M MH 1M M4 works: When the sensors are dry, transistor Q1 does not D9 D10 D11 receive power, so N2222 2N2222N2222 N2222 and the ./ buzzer (BZ1) is not activated. When water bridges the +3V sensors, power is applied to /fir rr the base of transistor Q1 O/r LEDO LED7 D8 LED9 OLED10 allowing current to flow to BZ1, turning it on. The sensors are nothing more than Fig. 8. This circuit is typical of what can be accomplished using a resistor network and several pieces of foil tape with transistors. The is essentially a -based circuit transistor light organ. wires soldered to them. You could even use nails or just

plain wire. For best results, I Dave, I'm certain that MC34017 -3 offers a 500 Hz problems for some other found that the sensors people visiting you are im- tone with a Cl value of readers. should be placed about 1/8- pressed by what you've 2000 pE -Lloyd F. Thomas, Ox- inch apart. done, so, you see, there is a The important features nard, CA Incidently, this is my first

practical use for your circuit are that you can com- You know Lloyd, a lot of effort at circuit design! I after all. pletely replace the our readers have had to learned electronics by telephone bell circuit using put up with that sort of watching electronic shows

RINGER APPLICATION a minimum number of Thing, and now thanks to and reading magazines. I The ringer on my phone components, Each IC ver- your contribution they won't enjoy the hobby and hope

was so low that I could sion offers on -chip diode have to anymore! Good to be able to major in

hardly hear it. I checked going. electronics when I get to with GTE and learned that college. the maximum "Ringer WATER DETECTOR -Tony Rossi, Lititz, PA Equivalency Number" (REN) They say that necessity is Readers, Tony is 15 years

was five. I added the REN's the mother of invention. This old, and I think you'll agree of all my phones and found circuit was designed to that his first effort is worthy that was the seat of my monitor our basement for of encouragement. Hope problem. floods. Occasionally our you enjoy your Think Tank

I could have replaced all washing machine or sink book, Tony! the ringer bells with elec- would overflow and if ev- Well that wraps up things tronic ringers to solve the for another month. Don't

problem, or I could have forget, your contributions used a single bell in a cen- Fig. 9. The remote ringer is are an important part of tral area where it could be built around a single this column, so keep those heard. The best place was integrated circuit, the BZ1 circuits and comments MC34017, which comes in D1 the hallway where the front 1N914 coming! three flavors with and back door chimes differing tone frequency outputs. were located.

I adapted a circuit (see Fig. 9) from a Motorola bridge and transient pro- book, using one of three tection, direct drive for the available IC's, each requir- piezoelectric transducers, Fig. 10. The Water Detector is an extremely simple circuit ing a different capacitor for and base frequency op- that is triggered by bridging the level of tone required. tions; the input impedance the gap between its sensor The MC34017 -1 provides a signature meets Bell and EIA plates. 1.0 kHz tone when Cl is requirements, and it rejects 1000 pE The MC34017 -2 rotary -dial transients. That erybody was upstairs, the "I never fired a shot. . . provides 2.0 kHz with a Cl solved my problem and I water could damage many the robot decoy just went erild.'' value of 500 pE The hope that it will solve similar of our valuable possessions. 22 www.americanradiohistory.comAmericanRadioHistory.Com No other training in school, on the job, anywhere -shows you how to troubleshoot and service computers like NRI

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DIGITAL LOGIC r. PROBE . Simplifies analyz- ing digital circuit - -' operation.

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www.americanradiohistory.comAmericanRadioHistory.Com Popular Ele ctninìcS S=?TEMBER 1491

BY Make Your ELLiOT KANTER

There's nothing really magical about assembling your own IBM PC compatible computer, in Own MAC tact, nearly everyone has or will be doing it. Some experts feel that most You can build an easily expandable Macintosh with some electronics companies are now ac- tively and aggressively producing IBM built -in frills for less than what a new no frills unit would clones oven the off-shore companies cost. that used to make CB radios. But that's something you probably already know. cate the Apple computer system, they rights -you will be using riginal Apple Besides, the topic of this article is how to have found themselves facing perhaps parts, not illegal duplicates. build your own Macintosh a, so perhaps the industry's most aggressive and suc- That may sound expensive, but its we should ponder the question: "Why cessful legal department. If you've fol- really not because good used Macin- aren't there any Macintosh clones as lowed the newspapers over the years, tosh motherboards can be purchased weil the marketplace is litteed with the very cheaply. Unlike IBM clones, Macin- The answer tc that question is one of "bones" of firms who tried to duplicate tosh computers don't have a bunch of legality rather than technology. Apple or replicate Apple products but got le- expansion slots. So when a user wants to Computers in their infinite wisdom de- gally burned. upgrade a Macintosh, say by adding a signed and patented a rather unique You might now wonder, how Cher can hard disk, the motherboard must be re- product line -the Apple Computer, a magazine as reputable as Popular placed. The old motherboards are usu- and more recently the Macintosh. Electronics even consider running an ally consigned to the local landfil , or While there have been several compa- article on building your own Macintosh. retained by a dealer as a source of nies who have tried to "clone" or dupli- The answer is quite simple: No step or spare parts. (If yoG are concerned in this will the and want to 'Maontosh is a registered trademark of Apple procedure contained article about environment Corporation. violate any of Apple Computer's legal save some landfill space, building your

www.americanradiohistory.comAmericanRadioHistory.Com own Macintosh is the way to goj So TABLE 1- ITEMIZED COST distributors for used motherboards have sprung up, and you could buy Item Approximate your own legal Apple Macintosh moth- Cost erboard at low cost, For example. we bought ours for $45 from one of the Motherboard 128K $ 45.00 sources we mention elsewhere in this 128K ROM set $120.00 Memory Upgrade /SCSI Adapter $249.00 article. Mouse $ 69.00 However, a motherboard does not a 256K Memory Modules (minimum of 4 needed) $ 25.00 /ea Macintosh make. Sure you could go out Monitor $149.00 and by the original Macintosh case, SCSI 40MB Hard Drive $400.00 ATS Convertible Kit $375.00 power supply, CRT, etc., but what you'd Keyboard (Basic Mac) $ 99.00 have would be a somewhat crippled computer limited by whatever the Total: $1606.00 motherboard's original configuration might have been. If it was an early Note 1: Available from ATS (see box entitled "Accessory Sources" elsewhere in this article). model, you'd have about 128K RAM Note: You'll also need a copy of the Macintosh Operating System from your local Apple dealer. and be forced into using a low capacity space- eating 5.25 -inch floppy that has produced a kit with almost all see a hard drive in your immediate fu- drive- hardly a state -of- the -art system. the features we'd hoped for. The ATS ture, you could instead add a second But what if we told you that you could Convertible Kit, as the package is floppy drive to the system and reduce assemble a high performance, `infi- called, sells for less than $400 and in- the cost by some $200. Likewise, if you nitely" expandable Macintosh with only cludes a small -footprint PC -like case, have a monitor that can easily be con- a few simple hand tools and at a price power supply, cables, video /power verted to reproduce the Apple/Macin- less than the original cost of an un- adapter, 800K 3.5 -inch floppy drive, tosh /ATS video output, you can save adorned Macintosh? What if you could and a well written instruction manual. another $149 -that is providing you do it in less than Iwo hours and in most What remains is for you to do a bit of can safely make the modifications (that cases without the need for a soldering shopping on your own and acquire the topic will not be covered in this article.) iron? Would you be interested? If your "guts;" namely a Macintosh mother- answer is "yes," read on. board and ROM. You'll also need a Ordering Information. Now that memory /SCSI adapter board (which you've got an idea of what it will cost, Enter the Convertible Kit. The idea ATS can also supply), a few hand tools, you need to know where to buy your of building a home -made Macintosh is and a bit of time. supplies, and how to get in touch with an old one. However, up to now build- the sources. The boxed text entitled "Ac- ing a Macintosh was a project only for Shop `Till You Drop. We've already cessory Sources" lists sources as well as the full -blown hacker. You'd have to as- identified some of the key components addresses and, in most cases, toll -free semble components, solder and cut foil of our Macintosh system, and Table 1 telephone numbers. traces, and really get into the circuitry. gives you a run -down of what you need Before you order your motherboard Hopefully, the end result was a usable to acquire, and the actual costs we en- or Convertible Kit, there's something Macintosh. Frankly you had to be a real countered while ordering the supplies. you should know: For some unknown glutton for punishment to shop, modify, You might stop and wonder about the reason. Apple elected to use Iwo dif- solder, shop some more, and then still cost, considering there have been ad- ferent package styles for their CPU IC's. not really have what you wanted. vertisements for Macintosh Plus com- One type of chip, easily identified by its What the less daring of us needed puters for less than $1000 in the media. black -plastic body requires a con- was a "Volkswagen" approach to build- However, the Macintosh advertised nector called a "IGlly clip" in order to ing your own Macintosh. Something does not come with a hard drive, nor is install the memory/SCSI adapter board. along the lines of an IBM clone, so any- it what I tend to refer to as a "platform," The !illy clip can be installed in a few one with a few screwdrivers and a which can be expanded at will and in moments with the use of just a screw- moderate amount of skill could build an almost infinite manner. Likewise, you driver. one, and do so at a cost -effective will be getting a system with a full -sized The other chip has a gray ceramic price. power supply and a conventional PC case and will require the use of a dif- With the easy and legal availabili`y of monitor -a far cry and improvement ferent connector called a "pin header." certain key components -namely the over the minimal display which comes Installing the pin header requires the motherboards and BIOS ROM chips - standard on the Macintosh Plus. use of a small tip, low wattage soldering for a reasonable cost, all we needed However, for the accountants or iron to make 64 connections. So, if at all was for someone to figure out how to bean -counters in our readership, the possible (especially if you doubt your produce a kit platform that would allow total price shown is still less than the soldering skills) request a motherboard the integration of these components original Apple Macintosh computer with a black -plastic 68000 CPU chip. with a decent -sized power supply, and pricing, and still represents a cost - You will also need to let the people at to figure out how we could use a reg- effective savings over the actual or true ATS know which type of CPU you have ular PC- compatible monitor to further cost (apples to apples minus the dis- before ordering a Convertible Kit so limit the expense. play) of a similarly configured Macin- they can ship you a kit with the proper Well, there's a little company called tosh Plus with a 40 -MB hard drive. If you connector. ATS, Inc. (Atlanta Technical Services inc.) are in the mood to be frugal, and don't On a different note, you might be

www.americanradiohistory.comAmericanRadioHistory.Com TERRITORY COVERED BY SCSI /MEMORY MOUNTING ADAPTER 68000 HI MISSING POWER TANG HOLE WHEN IN PLACE CPU ROM KEY PIN CONNECTOR `W2 W7

MODEM CONNECTOR

PRINTER CONNECTOR

MOUNTING HOLE N EXTERNAL FLOPPY CONNECTOR

MOUSE CONNECTOR

KEYBOARD MOUNTING NOTCH FLOPPY TANG CONNECTOR HOLE FOR KEY DRIVE CONNECTOR

Fig. I. This is a basic Macintosh motherboard. The most useful features shown here are the locations of the ROM chips and the area that will be covered up by the SCSI /memory adapter.

able to save some money if you know commission, keep in mind that the un- Replacing the ROM Chips. Now that someone who has just added an addi- der -rated power supply and CRT in the we have all of our components to- tional 800K drive to their system, and early Macintosh systems were more gether, let's get underway. Our first step won't be using their (supplied) BIOS prone to failure than the motherboards, will be to replace the motherboard's ROM chips. Under no circumstances which is really what you'd be interested 64K ROM chips with 128K units. There should you attempt to copy or know- in anyway. are two socketed chips (see Fig.1), ingly purchase copied /counterfeit Assuming you've placed all your or- clearly identified on the silk screening Apple Macintosh BIOS ROM chips. ders, you will still need a few common as "HO" and "LOW" ROM. They should The author, Popular Electronics, hand tools such as a Phillips -head bear the part numbers 342-0220 and Gernsback Publications, as well as the screwdriver, a small flat-blade screw- 341 -0221, respectively. people at ATS Inc., caution you against driver, a 3/10 -inch nut driver, a 7/32 -inch Wearing your anti -static wrist strap re- potential violations of Apple's rout driver, gas -joint pliers (common move each of the IC's by sliding a flat - copyrights. Regardless of how much household pliers), long -nose pliers, and blade screwdriver between the ROM you might think you'll save, the potential an anti -static grounding wrist strap. If and its socket. Rotate the screwdriver legal hassles you could run into can be you couldn't find a plastic -CPU mother- and gently pry the ROM free. Repeat more cosily. In short, don't do it! board, you'll also need a 15-25-watt this process for the remaining ROM Likewise, you could possibly acquire soldering iron with a small lip, a supply chip. You can discard the two old chips an as -is motherboard at a flea- market of rosin -core solder, and some liquid as you won't be using them in your or swap meet. If you find one out of flux. "new" Macintosh.

www.americanradiohistory.comAmericanRadioHistory.Com Because we have no way of knowing which of the Iwo CPU's (black plastic or gray ceramic) your motherboard has, we will describe both the Killy clip and pin- header installation procedures. Throughout our discussion we will use numbers in the parenthesis to refer to y4hh!,hh!,!rb bb! dddddddbb b b bb bbbbbbbr special points in the figures. For either procedure be sure to wear your anti- static wrist strap and read the instruc- iI991!1!I!I9!1!I!I! I!I!1!I!I!1!I!I!1!I!I!I!I!1!I!I!I!I!I!1llr tions at least once before beginning. 3 4 Let's start with the procedure for the black -plastic CPU using the !illy clip (illustrated in Fig 2), which should be somewhere among the hardware. 5 JIIIIIIIIIIIIII191IIIIIIIIIIIIII Place the clip over the CPU chip with 111111111.1111.1111111111111111111 the flange on one end of the clip cen- tdddddrlaldrbbbblddddddddddeb!dbbyr VHHM3lHHNHHHHHINHFIIHHHHÍ{} liHiSIS1H tered on the body of the CPU chip (1). Do not hook the flange under the CPU Fig. 3. Follow this guide to install the pin chip at this point. Holding the Killy clip header on a Be sure to 8 ceramic CPU. 111111111111IIIIIIIIIIIIIIIIIIII firmly, push the clip towards the other remove the spacers first. end of the CPU (2). The end of the clip r :IN N 'N: N.) resting on the CPU will bend slightly out- driver into the slot on the free end of the ward. While maintaining pressure on Use the screwdriver as a lever to Fig. 2. This drawing shows the step -by- clip. step installation for the Killy clip. You'll the clip, insert the flat -blade screw- gently bend the end wall of the clip need to follow these steps if your away from the chip (3) while sliding the motherboard has a plastic CPU. clip down over the CPU (4). Remove the ACCESSORY SOURCES screwdriver once the flange is resting Locate the new HI ROM chip (part on the body of the CPU chip (5). Now number 342 -0341) and examine itto be CONVERTIBLE KIT AND MONITOR: apply downward pressure to the Killy sure that the pins are all straight and exit ATS (Atlanta Technical Specialists), Inc. clip (6). The clip will first snap into posi- the IC at right angles. If any pin (or Deg) is 3550 Clarkston Ind. Blvd. tion on one side of the CPU chip so it bent, carefully straighten it using your Suite F rests on the circuit board. Push down on Clarkston, GA 30021 long -nose pliers. One end of the ROM the side that has not fallen into position. 1 -404- 292 -6655 has a notch. Insert the ROM in the HI It may take considerable force to seat ROM socket, with the notched end the clip, which will be indicated by an USED MOTHERBOARDS: pointing towards the CPU chip as audible snap as the flanges fit under Pre -Owned Electronics shown in Fig. 1. In a similar manner, lo- the CPU chip. When the clip has been 30 Clematis Ave. LO ROM installed properly, both sides of the Killy cate the new chip (part Waltham, MA 02154 (7). number 342 -0342) and carefully insert 1 -800- 274 -5343 clip should touch the circuit board it into the LO ROM socket. The notch on Examine the clip, the pins should extend Shreve Systems if the LO ROM should also point towards 2421 Malcom St. vertically from the top of the clip, nec- the CPU. Make sure that both ROM Shreveport, LA 71108 essary, straighten any bent pins (8). chips are firmly seated in their sockets. 1 -800- 227 -3971 To install the pin header (see Fig. 3) instead, start by removing the U- Installing the Connectors. Now you 128K ROM/UPGRADES: shaped plastic spacers on the CPU if can unpack your Convertible It (if you Pre -Owned Electronics any are present on the motherboard. haven't already). You will find a low -pro- 30 Clematis Ave. You should be able to push them off file case and an instruction manual. Use Waltham, MA 02154 with your fingers or a small screwdriver. your Phillips screwdriver or a 7/32-inch 1- 800 -274 -5343 Examine the pins of the CPU for corro- nut driver to remove the four cover Peripheral Outlet sion. Clean the pin surfaces by rubbing screws on the sides of the case, and 314 S. Broadway them with a pencil eraser and remove carefully pry the cover up and towards Ada, OK 74820 any residue with a cloth dipped in com- 1 -800- 332 -6581 you. Inside the case you will find the mon rubbing alcohol. You may wish to cables, hardware and battery pack as MacProducts USA apply a light coating of liquid flux to the 8303 Mopac Expressway Suite 218 pins to solder. Bend well as a package of four M alkaline Austin, TX 78759 before beginning batteries. Remove the components 1- 800- 622 -3475 the pins outward on one side of the pin and set them aside. At the same time, header by approximately 10 degrees CMO (1). is take out the 800K floppy drive by re- 101 Reighard Ave. That necessary to fit the header moving the four screws that secure the Williamsport, PA 17701 over the pins of the CPU. Place the pin floppy drive plate and lifting the assem- 1- 800 -233 -8950 header over the CPU (2). Make sure that bly, placing it aside; we will be reinstall- Shreve Systems the pins of the header are aligned with ing the floppy drive later in our (See address under "Used Motherboards ") the pins extending from the CPU chip. procedure. Push the header down as far as it will

www.americanradiohistory.comAmericanRadioHistory.Com SCSI CPU CONNECTOR DIP SWITCH

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LEFT RIGHT SOCKETS SOCKETS

MEMORY MODULES

Fig. 4. This is the memory /SCSI adapter board with two SIMM's at the bottom. Note that each row of SIMM sockets requires tiro SIMM's.

go. There will be a slight gap between Once you've soldered the header in SCSI adapter board (see Fig. 4). Table 2 the body of the pin header and the place, it is impossible to reposition it. shows how to configure the DIP switch body of the CPU. Inspect your work. A good solder joint located on the adapter board to suit You can now begin carefully solder- will be shiny (not grainy) in texture, and the memory and motherboard's "base ing the pin header in place (3). Note will have a filet of solder between the that the ceramic chip can act as a very contacts (4). Examine the pins on the NUTS STAND -OFFS so need to pin header. They efficient heat sink, you may should extend ver- LOCK WASHER use a higher temperature setting (if you tically from the top of the header. If have one) on your soldering iron in necessary, straighten any bent pins (5). order to make good connections. First o solder the four corner pins to hold the Memory Installation. We've now header stationary. Before soldering the completed perhaps the most difficult remaining pins, make certain that the part of our Macintosh assembly, and header is parallel to the motherboard. are ready to configure our memory/

TABLE 2- DIP -SWITCH CONFIGURATION

Motherboard Total Si S2 S3 Type Memory

128K 1MB OFF OFF OFF REAR PANEL 128K 2MB OFF OFF ON WASHER 128K 4MB OFF ON ON 512K 1MB ON OFF OFF Fig. 5. Use these sn s cnting details for the 512K 2MB ON OFF ON Video and SCSI con t ,ctors. ft's a good 512K 2.5MB ON ON OFF idea to mount then[ ) tto the back panel 512K 4MB ON ON ON lie¡ùre installing the motherboard.

www.americanradiohistory.comAmericanRadioHistory.Com memory size." TABLE 3-SIMM CONFIGURATION The information in Table 3 should allow you to properly arrange the memo- SIMM's SIMM's SIMM's Row 1 For Row 2 For Row 3 ry modules (called SIMM's) in the slots Motherboard Memory For suit on the adapter board to the moth- 128K 1MB 256K 256K Empty erboard and the amount of memory 128K 2MB 1MB Empty Empty you desire. Note that each row on the 128K 4MB 1MB 1MB Empty adapter board has Iwo sockets, a left 512K 1MB 256K Empty Empty 2MB 256K 256K 256K one and a right one. Both must be filled 512K 512K 2.5MB 1MB Empty Empty with the specified SIMM to complete a 512K 4MB 1MB 1MB Empty row. The SIMM's should be installed by in- Note: Each row has a left and a right socket and both sockets must be filled with the designated SIMM. serting them at a 75° angle, then rotat- ing them downward until they snap into place, causing both plastic locating tabs to engage. Once the memory is MULTIPLEXER installed, and the DIP switches are con- INPUT ---- figured, you are ready to connect the adapter board to the motherboard, either via the Killy clip or the pin header. If you are curious, look back at Fig. 1 to see the area that will be covered up by the adapter's circuit board. Start by setting the motherboard on a flat surface and then orient the VIDEO sssO adapter board so that its six SIMM sock- KEY ets are positioned over the RAM chips on the motherboard. Sight between the motherboard and the adapter RED WIRE SPEAKER BLK CN6 RED board to ensure that all of the pins are aligned. Apply downward pressure to GREEN LED L WHT CN2 GRN P9 POWER the CPU chip on the adapter board. CONNECTOR YELLOW Once installed, the pins of the Killy clip LED WHT CN3 YEL or pin header should be fully inserted BATTERY BLK CN1 RED into the socket on the underside of the BLACK WIRE SCSI /memory- adapter board. Now carefully set the motherboard /adapter BLACK WIRE board aside so you can proceed with P8 POWER CONNECTOR NUT

PAPER MAC PCB ORANGE WIRE WASHER MACPOWER PC POWER OUTPUT INPUT

Fig. 7. This is a top view, of the power /video -adapter board. Its mainly responsible for PLASTIC performing the Converter Kits magic. WASHER the assembly of the "home" for your idea. We found that the motherboard STAND -OFF Macintosh. left little room for maneuvering the connectors into place, so you should CASE Final Assembly. The manual which install the connectors first. comes with each ATS Convertible IGt is In that vein, open the parts packages well illustrated and very detailed. For and select the SCSI and video -cable i i r that reason, we will merely summarize assembles. Using your 3/46 -inch nutdriver the remaining assembly steps, adding and long -nose pliers, mount the two SCREW illustrations, photographs, and some connectors to the two vertical slots on suggested changes in assembly order the rear panel. The hardware assembly that we found to be of benefit. for this step is shown in Fig. 5. Flop the Fig. 6. Mount the circuit board standoffs Although the manual suggests cables attached to the connectors using this figure as a guide. You should mounting the SCSI and video con- over the rear of the case to move them place the plastic washers between the PC nectors to the rear panel after installing out of the way for the next steps. board and the body of the standoffs. the motherboard, that's not a good (Continued from page 90)

www.americanradiohistory.comAmericanRadioHistory.Com BUILD A SIMPLE LASER POWER SUPPLY

BY GREGORY GRAY manufacturer at somewhat higher schematic diagram of the Laser Power

prices than I wanted to pay. Being a Supply. The circuit consists of a 555 os- Here's a simple, graduate of the "Burned Silicon" tech- cillator /timer (U1), two transistors -a nical institute, I decided to design my 2N2222 general -purpose unit and a inexpensive, and easy -to- own. 2N3055 power transistor, Q1 and Q2, The Laser Power Supply presented in respectively -an ignition coil (L1), and build power- supply circuit this article is the way I got around the a few support components, which are for your low -power laser power -supply dilemma. While it is not required for U1. what you'd call "high tech," it does Configured as an astable multi - tube. serve its purpose quite well. The circuit is vibrator, the 555 oscillates at approxi- capable of driving most tubes with 0.5 mately 500 Hz. The output of U1 at pin 3 Ihad always been fascinated with mW to 7 mW ratings. But before we get is fed to the base of Q1, causing it to lasers, but until recently, the cost of to the project, a few cautionary words alternate off and on in time with U1's laser tubes always seemed to be are in order. output. The collector of Q1 is con- just beyond my modest budget. That's The power supply uses an auto- nected to the base of Q2. As Q2 turns no longer the case; today hobbyists mobile ignition coil to generate a high on and off, a rising and collapsing can buy small helium -neon (He -Ne) voltage, which is required to operate magnetic field is created in the primary gas laser tubes for $35.00. A similar tube the laser tube. If you've ever been zap- winding of L1 (the auto ignition coil). The would have cost hundreds of dollars just ped by a car's live spark plug wire, you rapid switching of Q2 induces a suffi- five years ago. know its not a pleasant feeling. Also, the ciently high voltage in the secondary of Isn't progress wonderful? But as luck beam of light produced by a laser is L1 to drive the laser tube. Note that a would have it, just as soon as you clear very intense, and can cause damage pulsating DC voltage is delivered to the one hurdle, another crops up to take its to the eye if viewed directly. Doctors use laser, which will cause problems if you place. Now the problem no longer lies lasers to weld severed blood vessels in try to send data over the beam. So this

in getting the laser tube; instead the patients whose retinas (back part of project is not suitable for voice- or data - problem is getting a power supply your eye) have detached; therefore, transmission applications. that's capable of driving the tube. Al- never look directly into any laser A 6 -volt ignition coil was used to keep though there are commercial units beam. Viewing a laser head on is akin the operating voltage as low as possi- available, locating an inexpensive laser to looking at the sun through a tele- ble. The circuit was designed to be power supply can be a big problem - scope, which can damage the eye de- powered from a 6 -volt source. Warn- much bigger than I had expected. pending on the level and duration of ing: The source voltage to the Laser Of course, there have been many exposure. So resist the urge to view the Power Supply should never be allowed magazine articles dealing with the sub- beam directly, or reflected off any mir- to exceed 7 volts; any higher voltage ject, but most required special parts rored surface. could damage the laser tube. The and special high -voltage transformers, Laser Power Supply can also be used to

which were only available from the How It Works. Figure 1 shows the operate up to a 2 -mW laser tube from a

www.americanradiohistory.comAmericanRadioHistory.Com source of as little as 5 volts as long as the power supply is capable of deliver- ing at least 500 mA. A 6 -volt lantern battery can also be used to provide power to the circuit. But, the battery must be fresh and it will not last very long in actual operation.

Construction. In developing the Laser Power Supply, the main criteria was that it contain no special parts. So all of the 3 "he INCHES parts used in the circuit, with the exception of the laser tube, are locally avail- Fig. 2. Here is a refined full -size template of the original printed- circuit pattern hat was able; the ignition coil from auto -parts used to produce the authors prototype. distributors, the electronics and com- + 6V ponents from Radio Shack and other electronics suppliers. - +} Although the circuit board for the prototype was hand -drawn directly on a copper -clad slug (unetched circuit - board material), a refined full -size template of the original printed- circuit pattern is shown in Fig. 2. A parts - placement diagram corresponding to that printed- circuit template is shown in Fig. 3. Begin construction by first installing a socket for U1 where called for in the parts- placement diagram, but do not insert the IC yet; that's the last thing to be installed. Following that, install the resistors and capacitors. Note that two resistors R1 and R2, are vertically mounted to the board. When insta ling C2 (the electrolytic unit) be sure that it is properly oriented, as shown. After installing the passive corrpo- Fig. 3. This parts-placement diagram corresponds to the printed -circuit foil pattern nents, install the transistors. When install- shown in Fig. 2. Begin construction by first installing a socket for Ul, but do not insert ing Q1 and Q2, be sure to observe the the IC yet; that's the last thing to be installed. proper orientation of those components. The emitter and collector termi- ter terminals of the unit are slightly off nents, solder bridges, etc. Note that Fig. nals of Q2 are clearly marked on the center. 3 shows the printed- circuit board bottom of the package, and the unit Once you've assembled the printed - mounted to the ignition coil. The coil will comfortably fit the layout in only circuit board, check your work for con- must be modified before being con- one way, because the base and emit- struction errors: misoriented compo- nected to the board. The modification to the ignition coil is a modest one. Sim- + 6V ply remove the screw inside the tower; that's the screw terminal inside the

WARNING!! This article deals with and involves subject matter and the use of materials and substances that may be hazardous to health and life. Do not attempt to implement or use the information contained herein unless H.V. you are experienced and skilled with respect to OUT such subject matter, materials and substances. Neither the publisher nor the author make any representations as for the completeness or the accuracy of the information contained herein and disclaim any liability for damages or injuries, whether caused by or arising from the lack of completeness, inac- curacies of the information, misinterpretations Fig. I. The Laser Power Supply consists of a 555 oscillator /timer (Ut), two transistors -a of the directions, misapplication of the information 2N2222 general- purpose unit and a 2N3055 power transistor, QI and Q2, respectively- or otherwise. an ignition coil L/, and a few support components, which are required for Ill .

www.americanradiohistory.comAmericanRadioHistory.Com LASER

TO POSITIVE SIDE OF COIL (TOWER)

LID

END CAP NIPPLE

75K 3 WATT LASER GOES INSIDE BOX RESISTOR

TO NEGATIVE SIDE OF COIL

TO LASER'S POSITIVE TERMINAL

WIRE EXIT HOLES

LIGHT EXIT

CLIP TO LASER'S NEGATIVE TERMINAL

Fig. 4. Prepare the laser tube for connection to the Laser Power Supply by removing the clips from the ends of the tube, and connecting a 75k, 3 -watt resistor to the clip that goes to the glass end, and the high - voltage wire from the coil's center terminal to the other end of the resistor. The wire from the negative output terminal of the Laser Power Supply connects to the other clip.

tube -like structure at the center of the PARTS LIST FOR THE LASER POWER SUPPLY coil. Remove and discard the spark - plug wire holder. Then take a length of SEMICONDUCTORS LI-6 -volt auto -ignition coil rubber insulated heater -supply cord, U1 -555 oscillator /timer, integrated Printed-circuit materials, % -mW and separate the two leads. Heater circuit standard size He -Ne laser tube, in- 2N2222 general -purpose NPN cord was used to ensure adequate Ql- 75,000 -ohm 3 -watt ballast resistor, silicon transistor sulation from the high voltage that it will Carlon electrical feed -through box, 5- 2N3055 NPN silicon power carry. Strip one end of one lead and Q2- foot rubber heater cord, wire, solder, wrap it around the screw. Then reinstall transistor hardware, etc. the screw with the wire attached. CAPACITORS Note: The following items are available Now install 1.11 in its socket and apply C1- Ml -p,F, ceramic -disc from Meredith Instruments, 6403 N. -p,F, 25 miniature 5 volts DC to the circuit's supply termi- C2-33 -WVDC, 59th Ave., Glendale, AZ 85301; Tel. electrolytic nals. The circuit should emit a high - 602 -934 -9387: Model #09 % -mW pitch whine due to the rapid switching C3 0.22 -11F, polyester standard size He -Ne laser tube, of the power transistor. Move the high - ADDITIONAL PARTS AND MATERIALS $35.00; 75,000 -ohm, 3 -watt ballast voltage wire (the one coming from the Rl, R2- 100,000 -ohm, 1/4-watt, 5% resistor, $1.50. Add $5.00 shipping side resistor and handling. Arizona residents please coil center) close to the negative R3- 330 -ohm''/ -watt, 5% resistor add appropriate sales tax. of the coil. You should get a spark of (Continued on page 90)

www.americanradiohistory.comAmericanRadioHistory.Com What Do Electrical Engineers Do?

PC Allow me to introduce myself. I bleshooting, -board am an electrical engineer - layouts, etc. The rela- have been for twenty five years. tionship between an engi- I've worked in research, new product neer and his or her design, engineering- support services, technician is much like that and various levels of management. I've of a doctor and nurse, or also done some writing, teaching, and architect and carpenter. speaking on the side. Today I'm working The nurse or carpenter as the engineering vice -president for a might perform much of the young and growing instrumentation hands -on work, but the company. doctor or architect is re- for the outcome. Why am I writing this article? Be- sponsible cause, probably like you, I became "hooked" on electronics as a young- Engineers in Industry. Just as a doctor might be a ster. I got my engineering degree a re- because I knew I wanted to work surgeon, a psychiatrist, a teacher, or a gen- in electronics, but I knew searcher, nothing about what an en- eral practitioner, an engineer gineer actually did. Twenty might choose from among You can get five years later, I think I've many specialties. found out! I've enjoyed it, an idea of the variety of engi- and hope this article will neering jobs in industry by follow- help you figure out if you ing a new product from the "raw - would, too. idea" stage to full production (see Fig. 1). Engineers, Technicians, New product ideas, which spur and Hobbyists. There is engineering activity, often begin no single answer to the outside engineering. For example, a question, "What do elec- company's marketing department trical engineers do ?" We might see a competitive opportunity or can, however, contrast an engineer's need. Perhaps a salesmen might come work to that of a technician or, for that up with some ideas, or customers might matter, a hobbyist. Where a hobbyist suggest or request new or modified might be happy to create a single cir- products from him or her. Manufactur- cuit or device that works well on the ing innovations might be requested bench, an engineer must produce de- from the production department to im- signs that can be repeatedly re- prove a design and /or reduce costs. Of produced. Component values gener- course, the engineering department ally cannot be "tweaked" but, instead, might also come up with a hot idea or must be carefully calculated to work BY HARRY L. TRIETLEY see a way to redesign products using despite component tolerances, Tem- new technology. No maffer where a perature extremes, line -voltage new idea starts, though, it usually winds changes, and the like. The calculations What does an up in an engineer's hands for initial and designs must be verified by multi- evaluation. Defense or other contracts ple tests of both prototypes and pro- electrical engineer do? require highly technical proposals be- duction units. Read this article fore a project is even begun. Engineers generally do the bulk of Proposals involving new technology the theoretical- design work and are to find out, and (or at least "new" to the company), or held ultimately responsible for their de- requiring fundamental technical inves- signs. Technicians, on the other hand, maybe learn if a tigation, might move first to a research often translate paper designs into real- career as an engineer depa- tment. Engineers and techni- ity through breadboarding, model cians Involved in research seldom pro- building, programming, testing, trou- is right for you. duce final designs. Their task is to 35

www.americanradiohistory.comAmericanRadioHistory.Com paths into marketing and manufactur- MANAGEMENT ing. In manufacturing it goes to a de-

PI AN, COORDINAI I_. partment with a name like "production PRIORITIZE. BUDGET. engineering," "manufacturing engi- PRODUCT IDEA STAFF. FORECAST, engineering." REVIEW. neering," or "methods MOST OFTEN, COMES The engineers in this group are less apt FROM OUTSIDE OF to be circuit -design experts, but instead ENGINEERING. concentrate on production tools and methods. Production engineers are in tune with

RESEARCH the latest in assembly techniques (electrical and mechanical) and create CONCEPTS. IDEAS, FEASIBILITY, LIKELY tooling, fixtures, test equipment, etc., COSTS, PROBLEMS, that fit the company's equipment and ETC. expertise. They also produce step -by- step procedures, diagrams, etc., that i make it possible for nontechnical pro- DEVELOPMENT duction wdrkers to produce the product. They might also be involved with MAJOR DESIGN CONCEPTS, SALES & CALCULATIONS, BREAD- MARKETING automation, robots, and the like. When BOARDS. TESTS IDENTIFY PRODUCT NEEDS they are finished, production is ready to / / MARKETS, DISTRIBUTION / CHANNELS, ADVERTISING build the product. CAMPAIGNS. Sales, marketing, and technical -writing departments all require engineers if DESIGN J' TECHNICAL the product is technical in nature. Engi- "NUTS & BOLTS" DETAIL, WRITING neers are also needed for applications DRAWINGS, PARTS LISTS, CALIBRATION & TEST assistance, technical marketing cam- FINAL MODELS, INSTRUC- PROCEDURES, CATALOGS, TIONS, ETC. paigns, instruction manuals, and adver- USER INSTRUCTIONS, WRITTEN PRODUCTION tising. METHODS. Most companies have one or more

PRODUCTION engineering support services groups. ENGINEERING ONGOING Those departments assist production PRODUCTION PREPARES DESIGN FOR with technical problems and revise, up- ROUTINE PRODUCTION. BY NONTECHNICAL PEOPLE. SETUPS, TOOLING, grade, or redesign products. They ENGINEERING FIXTURES, METHODS. SUPPORT SERVICES might be involved in submittals to Un- ONGOING TECHNICAL derwriters Laboratories and other ap- ASSISTANCE TO PRO- proval agencies, and with customer DUCTION & SALES. problems. The people who do best in these departments tend to be people - oriented, outgoing types who can jug- Fig. I. A product .flows through many departments on its way from concept to manufacture gle many balls at once. and sale. All of these departments might require engineers and technical people. Finally, of course, engineers can be found in management positions investigate concepts, feasibilities, costs, mended or if the idea does not need throughout most technological com- likely problems, etc. and to come up basic research, the project moves to panies, from project leaders and super- with further proposals and recommen- development and then to design. The visors, to top management. dations. Their work may include liter- development group creates the major ature searches, laboratory investiga- design concepts, details, and design Technical Specialization. By reading tions, breadboarding and testing, but calculations, and builds and tests pro- Popular Electronics you know that their final "product" is usually a report. totypes. The design department cre- there are many technical specialties in For some, this is the "fun" part of engi- ates the final "nuts-and -bolts" design electronics. No one can be expert in all neering since it involves less of the nitty- down to the last electrical, mechanical, of them. My own career has specialized gritty details. Others find it frustrating, and housing detail. The end result is a in measurement instruments and con- because their ideas are turned over to fully tested and documented design, trol systems. You might be more inter- other engineers who, of course, "im- including all necessary board layouts, ested in communications, while some- prove" them! (Ever hear of the "not -in- mechanical designs, parts and assem- one else might live and breathe vented -here" syndrome ?) Incidentally, bly drawings, models, tests, reports, and computers. Audio, power generation, proving an idea to be unworkable is a calibration procedures. The lines be- microwaves, satellites, and defense perfectly successful outcome, and tween development and design de- electronics are other possibilities. Figure might save the company from wasting partments are blurred and, in some 2 illustrates how complex systems can considerable time and money on un- organizations, do not really exist. require engineering expertise running workable, unprofitable, or otherwise You might think this would be the end from computers and satellites to con- unsalable designs. of the project, but it's not. The design trols and power distribution. Even within If further development is recom- generally advances on two parallel these areas there are specialties.

www.americanradiohistory.comAmericanRadioHistory.Com SENSORS

TEMPERATURE PRESSURE, FORCE

T SIGNAL CONDITIONERS VOLTAGE, CURRENT ANALOG

LINEAR

SOFTWARE

AUDIO

TELEPHONE

SATELLITE

POWER GENERATION & DISTRIBUTION

Fig. 2. Electrical engineering runs the gamut from "glamour" areas such as computers and satellites to "bedrock'' areas such as power and controls.

Consider, for instance, computerized Job Opportunities. You might think of electronics, but with less depth. A gen- banking or airline -reservation systems. the opportunities in engineering as a eralist is often a competent designer, Integrated- circuit engineers design the large 3 -D matrix (Fig. 3). Along the ver- but probably needs help for in- depth, necessary computer chips (some of tical axis are the technical specialties- complex state -of- the -art designs. which might be custom) that hardware power, analog, audio, computers, sat- Smaller companies generally cannot engineers use to design circuitry. Sys- ellites, etc. Across the bottom we see afford to hire a number of specialists tems engineers design, coordinate, areas of employment, from research and so hire mainly generalists, perhaps and install the networks and computers and design to production engineering turning to outside consultants when that operate and communicate using and the support areas. There are even specialized expertise is needed. In programs designed by software engi- related fields such as law and bio- larger organizations, a generalist might neers. All these people are "computer" medical research (more on that in a direct, coordinate, or manage several engineers, but not one of them is an minute). specialists on large, complex projects. expert in all areas of computing. The Add to all of this a third dimension: So far we have looked at industry, but project might be planned and man- specialist or generalist. As mentioned engineers serve in other areas as well. aged under the direction of a gener- before, a true specialist is an expert in Many government positions are avail- alist, someone whose knowledge is his or her area of technical con- able, ranging from the military and broad enough to understand what all centration and is highly skilled in one or NASA, to state and local positions. (State the experts are doing but not deep more related fields. Using the medical and local governments, however, are enough to be able to specialize in any analogy again, a surgeon might spe- more apt to hire civil or environmental one area. cialize in heart, brain, or other surgery. engineers than electrical.) Other fields have sub -specialties as Engineering specialists are most apt to Furthermore, other areas include ed- well, "Linear" designs run from mea- be found in research and develop- ucation, patent and technical law, re- surement and controls to audio, RF and ment. search, and consultation. Although you microwaves, while "communications" As you'll recall, a generalist has generally need a Ph.D. (a doctorate) includes circuitry, microwave and satel- broader knowledge, quite often in- degree to become a full college pro- lite antennas, networks, systems, and cluding mechanical, chemical, or fessor, technical and trade schools offer complex communications theory. manufacturing engineering as well as other positions in education as well, (It

www.americanradiohistory.comAmericanRadioHistory.Com should be noted that education generally pays engineers less than industry.) ISi ' GENERAL Lawyers with engineering backgrounds are needed in patent law, technical liti- AffirAPArAPAPAPPAMPABS (lawsuits gation involving technical SPECIALIST claims), and other areas. Engineers with AffirrAgrArAriligrAfirdiral medical training are valuable in cer- SATELLITES tain areas of medical research (ar- tificial limbs, nerve stimulation, brain NETWORKS EEMMMMMMMA/ studies, sports medicine, etc.) and in COMMUNICATIONS medical -product development. Consulting engineers might be self - SOFTWARE 151 employed or might work for contract 11111.11111111 COMPUTERS and consulting firms. They most often MEASUREMENT 11111111fr work with industrial or governmental cli- & CONTROLS ents, but also serve as researchers, ex- 1111111E111111111410 pert witnesses, and the like. A self - RF employed or senior consulting engi- IIIM11111111111504 AUDIO neer should have a professional engi- IM1111111111111=1/Vr neer's license, which requires several ANALOG years experience in addition to passing state licensing exams. POWER

R D D P M S 1 M C E L

Becoming an Electrical Engineer. E E E R A U E A 0 D E First and most obvious, it takes a B.S. S V S 0 R P N N U G E E D K P H A S C A (Bachelor of Science) or B.E. (Bachelor L A L G U E 0 W G U A of Engineering) degree in electrical en- R O N C T R E L T gineering to become an electrical en- C P T I T M T I H M I N E A 0 gineer. Four years of full -time university S T E 0 G V N T N N N T I study is typically required, sometimes C N T 0 longer if the student is lacking pread- S G N mission requirements or wishes to take specialized courses. Part -time takes Fig. 3. The field of electrical engineering might be visualized as a 3- dimensional grid. much longer, but many companies of- The generalist has knowledge of a broad portion of the grid, while the specialist has in- fer tuition reimbursement plans to their depth knowledge of a few areas. employees and recognize scholastic progress at review time. never taught to me during my educa- To progress very far you will need Most companies are firm in their re- tion, that an engineer needs much "people" skills. Whether you ever go quirements-you cannot be an engi- more than a technical education. First into management or not, you almost neer without a degree. Some will and foremost, you need writing skills. certainly will end up supervising sup- promote their best senior technicians to Engineers are famous (or maybe in- port people such as technicians and quasi- engineering positions with titles famous) for their lack of writing ability, drafters. Most projects are team efforts, like "Designer" or "Engineering Associ- sometimes lacking even basic gram- not one -man shows. Engineers must ate." Smaller and less formal compa- mar and spelling. You don't need to be work cooperatively with production, nies can be more flexible in their an Art Buchwald or an Agatha Christie, marketing, and finance departments. promotion policies. but you do have to write proposals, re- Marketing needs to know what the end

I want to stress, from experience, that ports, user instructions, and applica- result of a project will be. The produc- the degree might give you the title, but tions literature. You must be able to tion department needs to know they it alone does not make you an engi- explain what you are doing (and why will be able to build it at a competitive neer. (You can't become a surgeon, or your employer should fund you) in non- cost, and the finance group needs to even learn to drive a car, without technical terms. A person who can't know the end result will be profitable. hands -on experience!) What the de- spell or use proper grammar has a hard The best designs in the world are no gree mostly does is give you the basics time being accepted as a professional. good if they cannot be produced and (lots of theory, math, and the like) and No matter where you end up on the sold at a profit. teaches you to think analytically. grid back in Fig. 3, you will need to do

Speaking personally, I was not a com- more than just design and build circuits. What are the Rewards? First, of

petent engineer when I started my first Projects need goals. An employer will course, income. Engineering is proba-

job even though I had been a hobbyist not hire you to "do your own thing." He bly the best -paying profession avail-

since junior high school. I became an or she will need to know what you are able to a four -year college graduate. engineer by working side -by -side with a doing and if it is worth his while to pay Starting salaries in industry generally first -rate senior engineer and by associ- you to do it. You wouldn't hire an archi- parallel what a highly- experienced se- ation with other engineers and tech- tect who couldn't tell you what he or nior technician earns and rise 50% or nical people in the company. she planned to build, how long it would more over the first several years.

I also want to stress, because it was take, or what the cost would be! (Continued on page 93)

www.americanradiohistory.comAmericanRadioHistory.Com 9paicle SONY'S NEW MINI DISC

Will Sony's new Mini Disc revolutionize the portable audio industry, or will it simply muddy the waters for years to come?

BY BRIAN C. FENTON

ust when you thought it was safe to What's more, in January of this year, What is the Mini Disc? Sony's Mini ildecide on your next audio record- yet another new format was an- Disc is a brand new audio format that is er, the waters look dangerous nounced. That format, called Digital specifically designed for portable ap- again, thanks to Sony's announcement Compact Cassette (DCC), combines plications-personal stereos, boom of their new recordable audio format, the familiarity and recordability of to- boxes, and, perhaps, even car audio. the Mini Disc (MD). What does it mean day's popular audio cassette with the The disc, about 21/2 inches in diameter, for you, your current audio gear, and sound quality of a compact disc. We looks and acts-like a cross between your future purchase plans? According thought that DCC had a fairly strong a compact disc and a micro floppy to the president of Sony Corporation of shot at success, since it was backed by computer disk. Like a compact disc, the America, "We are replacing nothing." Philips, Tandy, and a number of record Mini Disc is an optical medium -it is But let's see where the Mini Disc fits in. companies. More important, perhaps, read by a laser and can store up to 74 Today, consumers are spendirg their was that DCC recording decks would minutes of digital audio. Like a floppy music dollars on pre - recordec com- be capable of playing back all of your disk, the Mini Disc can be recorded on pact cassettes and CD's. Sales of digital existing cassettes. We had envisioned again and again. The Mini Disc differs audio tape (DAT) recorders are moving DCC co- existing with DAT; DAT would be from standard computer disks in that it slowly because of their expense, the aimed at the serious audiophiles, DCC uses magneto- optical technology for non -availability of software, and the sold to everyone else, and the venera- recording. general uneasiness and consumer ble compact cassette would be rele- One of the main benefits touted by confusion caused by the recording in- gated to answering- machine duty. Sony is "shock- proof" memory. In other dustry's attack on the hardware. Now, however, all bets are off. words, unlike portable CD players now

www.americanradiohistory.comAmericanRadioHistory.Com BEFORE ATRAC ENCODER Since the threshold of hearing varies with frequency, the components of the (dB) SOUND PRESSURE LEVEL sound are analyzed by the ATRAC en- 120 coder and are eliminated depending MASKING AUDIBLE on their frequency and level. A similar EFFECT analysis determines whether they will be masked by other sounds, and thus 60 T,9, can be eliminated from the recording. h/F99/2C Masking is a psychoacoustic effect that NOT we've all experienced. If a loud sound AUDIBLE and a soft sound of similar frequencies o I are produced, you won't hear the softer 0.02 0.2 5 20 (kHz) FREQUENCY sound. Theoretically, if the soft sound is removed, you won't notice the difference. As the level of the recorded AFTER ATRAC ENCODER material becomes louder, more components be removed without audi- (dB) SOUND PRESSURE LEVEL can ble effect. f 120 AUDIBLE Read /Write Magneto -Optical Disc. Although the Mini Disc is like a CD in that it is read by a laser, writing to (or record- 60 ing on) the disc requires both a laser and a magnetic head. The laser heats the disc's magnetic layer to a tempera-

o ture of around 400 °F. At that tempera- 0.02 0.2 5 20 (kHz) ture, the magnetic layer loses its FREQUENCY coercive force -in other words, it becomes very easy to magnetize. Before Fig. 1. ATRAC digital audio compression uses the psychoacoustic principles of the the disc cools, the signal on the mag- masking effect and the threshold of hearing to gain an almost 5-to-I advantage in storage netic head polarizes the magnetic when compared to a CD. layer. The polarization of the magnetic POLYCARBONATE of data that may be as long as three layer affects the polarization of the RESIN seconds, is created. If the laser mis- laser light reflected from the surface. tracks, it simply stops filling the buffer Unlike other read /write optical -disc while it finds its way back to the proper technologies, the Mini Disc overwrite location. The listener, unaware of the method is a single -step process that re- tracking troubles, is treated to flawless quires a single laser. To reduce the sound. power consumption to levels that are In order to get 74 minutes of audio compatible with portability, Sony de- (the same capacity as a CD) onto a veloped a terbium-ferrite -cobalt mag- disc that is only 2' inches in diameter netic layer (see Fig. 2) that allows the ('/a the area of a CD) something, ob- Mini Disc to use less intense magnetic viously, had to be left out. That some- fields than other magneto -optical TERBIUM FERRITE thing is digital data. Normally, a discs. COBALT MAGNETIC reduction in the amount of data on the MATERIAL PROTECTIVE disc could be expected to reduce the What's in the Future? Predicting the ALUMINUM LAYER audio quality. However, because of a future of consumer electronics is, in- REFLECTIVE LAYER data -compression scheme called deed, a difficult task. Even Sony has an ATRAC (Adaptive Transform Acoustic uneven track record. Their Beta VCR for- Fig. 2. Cross section of the MD magneto - optical disc. The terbium-ferrite-cobalt Coding), Sony claims to be able to mat, for example, lost out to the better - magnetic layer allows the MD to use less achieve CD -audio quality -or quality marketed VHS. The Sony- backed intense magnetic fields than other that is so close to a CD that only 2% of Elcaset tape- cartridge format was not magneto- optical discs. the population will be able to tell the exactly a smashing success. Their 8mm difference. See. Fig. 1. camcorder format is making gains ATRAC is nearly five times more effi- continuously, although it was greeted on the market, the Mini Disc player cient in encoding data than the con- with skepticism when it was first intro- won't mistrack even while undergoing ventional non -compressed 16 -bit linear duced in the U.S. shock and vibration. Actually, the laser encoding used on CD's. The main sav- Sony, of course, also co- developed pickup will mistrack, but the results of ings comes from ignoring the sounds (with Philips) compact -disc digital au- that mistracking will not be audible. that won't be heard anyway because dio. The strides that the CD has made in Shock -proof memory works because they're below the threshold of hearing the less than 10 years since its introduc- data is read off the disc faster than it is or because they'll be masked by other tion have been nothing short of re- required by the decoder. Thus, a buffer sounds. (Continued on page 98)

www.americanradiohistory.comAmericanRadioHistory.Com SEPTEMBER 1991

VOLUME 4, NUMBER 9

A CHRONICLE OF CONSUMER ELECTRONICS

A SW(el)L Receiver

SONY ICF -SW1S PORTABLE SHORT- WAVE RECEIVING SYSTEM. Manufac- tured by: Sony Corporation of America, Sony Drive, Park Ridge, NJ 07656. Price: $ 349.95

For the makers of world -band radio receivers, the past year has brought a mix of good news and bad news. The good news is that interest in shortwave radio surged dramatically. The bad news is that it took a major conflict, namely the Persian Gulf war, to get people to rediscover the medium. It's still unclear how many people will continue to tune in now that the war is over-even network TV news lost almost ten million viewers following the end of the war. Those people who had ignored shortwave radio for the last 20 years or so were probably astounded by the sophisticated receivers of today. Instead of hunting around on the old, notoriously inaccurate tuning dials for stations of interest, phase - locked -loop circuitry permits instant, pre- cise tuning and digital frequency readout. And today, a high- quality receiver needn't fill up the better part of a small desk_. In fact, the Sony ICF-SWI doesn't even fill CIRCLE 50 ON FREE INFORMATION CARD up a shirt pocket. The ICF -SWI receiver is the heart o' the ICF -SWIS shortwave receiver system, which is specifically designed for portable you'd expect from a desktop general - better bet (and permit FM -stereo listening operation. (The SWIS is available only as coverage receiver. It begins at 150 kHz, as well). The rest of the front panel is taken a complete system in the U.S., although in which is below the standard AM- broad- up by twenty pushbuttons and a tuning some other countries, the receiver is avail- cast band (and which is usually called display. Although the buttons are neces- able separately.) The complete system longwave), and extends up to about 30 sarily small, they're not difficult to oper- consists of a receiver, an AC -power adapt- MHz, the top end of most general - ate. Ten numeric buttons let you enter er, stereo earphones, an active antenna, coverage receivers. Also included is an frequencies directly, or call up one of the and an antenna controller, a rugged carry- FM band ranging from 76 to 108 MHz. ten station memories. AM and FM keys let ing case, and a couple of other handy ac- (While the FM band in the U.S. begins at you select the mode of operation or serve cessories. 88 MHz, in some other parts of the world, as "execute" buttons when a frequency is The receiver itself is the smallest wcrld- notably Japan, it begins lower.) entered. Manual up /down tuning buttons band receiver we've ever seen, measuring A small front -panel speaker provides are included -they also work in conjunc- about 43/4 x 2% inches, and is less than an adequate audio for those who aren't too tion with the band/alarm set and time set inch thick. Being smaller than most per- fussy, but the supplied earphones are a (Continued on page 7) sonal- portables, it easily fits in a shirt pocket. Its tuning range, however, is what TURN PAGE FOR CONTENTS

GIZMO Page 1 43

www.americanradiohistory.comAmericanRadioHistory.Com This Month In GIZMO.

Sony ICF -SW1S Portable

Shortwave Receiving System . pg. 1

Design Acoustics PS -55C Point Source Video Speakers pg. 2

Konami LaserScope Voice -Command Optical- Targeting Headset pg. 3

Franklin Electronic Publisher's The Holy Bible: King James Version KJ -21 pg. 4

Saitek 861 Electronic Championship Backgammon pg. 5

Nady Systems WH -90 Wireless Stereo Headphones pg. 6

Diskette File pg. 9

High -Quality Cassette Tape pg. 9

Extended -Memory Remote.... pg. 10

Personal Computers pg. 10

Repeat Learning System pg. 10

Ear Lenzes pg. 11 Of course, it's not network TV that has Did You Hear fueled the desire for better audio. Nor can Subwoofer System pg. 11 it be the cable -TV movie channels, con- What Was On sidering the poor quality signals delivered Wall -Mount LCD Monitors pg. 11 by most cable systems. Rather it's the hi -fi TV? VCR and laserdiäc players, coupled with Wrestling Video Game pg. 11 consumers' ever - ncreasing expectations, DESIGN ACOUSTICS PS -55C POINT that has made TV-set manufacturers pay Automotive Subwoofers pg. 12 SOURCE VIDEO SPEAKERS. Manufac- close attention to the amplifiers and speak- tured Dy: Audio- Technica U.S., Inc., ers that they install in their new sets. 1221 Comm?rce Drive, Stow, OH If you're like most people, you bought Metal Detector pg. 12 44224. Price per speaker: $119.95. your current TV before audio was considered as important as it is today-or you Multi -Room Controller pg. 12 We sometimes joke that if it weren't for couldn't afford the top -of-the -line set that our surround -sound audio system, we'd did offer good audio. If you're unwilling Projection TV pg. 12 never ,.watch network TV. Actually, it's not to plunk down the big bucks required to that much of a joke good audio is an get one of the latest sets witn hi -ti audio essential accompaniment to video. built in, don't despair. You Ain improve Gizmo is published by Gernsback Publica- the quality of your current setup. If your tions, Inc., 500 -B Bi- County Blvd., Farm- Today's video-equipment sales suggest outputs, im- ingdale, NY 11735. Senior Writers: Chris F. that we're not alone in our views; stereo TV offers external- speaker O'Brian, Teri Scaduto. Contributors to this is- TV's and Hi-Fi VCR's are making contin- proving your audio might be as simple as sue: Michael Scaduto, Injae Lee. Copyright uous gains. Ifs a far cry from the earlier adding a new pair of speakers, like the 1991 by Gernsback Publications Inc. Gizmo is days of TV, when a set's audio section was Design Acoustics PS -55CV. The speakers a registered trademark. All rights reserved. an afterthOught, if it was given any thought have a frequency response of 65- 20,000 at all. (Continued on page 7)

44 Page 2 `GIZMO www.americanradiohistory.comAmericanRadioHistory.Com Shooting Off at the Mouth

LASERSCOPE VOICE COMMAND OP- TICAL TARGETING HEADEST. Man- ufactured by: Konami Inc., 900 Deer- field Parkway, Buffalo Grove, IL 60089. Price: $39.95.

Somehow, despite our love of gizmos, we managed to pass through the Nintendo Era unscathed. We don't own any video games, and our playing has been limited to Penn Station arcade games as we waited for delayed Long Island Railroad trains, and the hands -on exhibits at trade shows like CES. There is a very practical reason behind our reluctance to get involved with videogames. We know all too well just how addictive such games can be. We did own an Atari 2600, back in the pre- Ninten- do days, on which we played "Pac Man" and "Joust" until our fingers were blis- tered from the joystick and our eyes were blurred from exhaustion. "Grown -up life" -busy work schedules, lawns to mow, family obligations, and the like - doesn't permit such indulgences. Accordingly, we had mixed feelings when we received a Konami LaserScope voice -command optical -targeting headset for review. The LaserScope consists of a pair of stereo headphones that features an "eyescope" which lets you line up targets simply by looking at them through the CIRCLE 52 ON FREE INFORMATION CARL cross -hairs. The eyescope sticks out from the front of the headset and hangs down in front of the your right eye. Jutting out from ether adjustments Lrc optional ones -you become acr, stomred to the optical- target- just below the left ear piece is a wrap- can turn off the television's sound so that ing. action, :ne ight-speak-and-shoot at around microphone that rotates up and no one else in the room is subjected to tien is accurate. Using the down and swivels in and out so that you video -game generLted musi2 and sound LaserScope for shooting frees both hands can position it right in front of your mouth. effects. and you can switch me headset to for asing the control pad (although we You simply aim through the cross -hairs at ' turbo fire" to rapid tire five shots with realty didn't find that necessary) The con - a target, and trigger shots by saying each vocal command. troller is still used to move back and forth "Fire!" or "Shoot!" into the microphone. We thought it a bit strange teat Konami or ap and down ihc semen, and we quickly The result is the same as if you had pulled could boast. "Parents will kwr it because tot. rid ourselves efturlessly coordinating the trigger on the Nintendo Zapper gun. game play noise is eliminated' as «ar hands, e}es, and voice. We would have The targets on the screen flash, and if though repeated houts of "Fire!" or preferred, however, an eyepiece that could you've aimed directly at the target, an op- "Shoot!" couldn't be considered "game used over either eye. If your left :ye is tical sensor in the eyescope detects that play noise." But a hit of experimentation y.) r dominant eye, you'll find the flashing, and the game registers a hit. (a necessity due to 'he thrcatr- of co -work- LaserScope takes a while to get used to. Needless to say, our misgivings about ers in the office) shower_ that the Ad NES Lan-es designed for use with having a Nintendo in our offices were over- LaserScope responds to quieter cues. In the Yapper t_un are compatible with the shadowed by our curiosity. So we trekked fact, even a quick 'puff" of a_r triggers the LaserScope. More than a dozen :Zapper off to our local video store, rented a Nin- shooting- without triggering the tempers games are t='ailable, only a few were in tendo set and a bunch of games, hooked it of anyone else in the room. And, for those st

GIZMO-Page 3 4 5

www.americanradiohistory.comAmericanRadioHistory.Com tion, entertainment, and even spiritual small and closely spaced for regular typ- Search, and Ye salvation It was simply a matter of time ing. The LCD, unfortunately, was very dif- before someone would try to transfer the ficult to read. Although the contrast is easy Shall Find age -old wisdom of the Bible into a modern to adjust (using the up- and down -arrow format. keys to make it darker and lighter), we had The time is now, and the someone who a hard time finding a setting that was clear- THE HOLY BIBLE: KING JAMES VER- took on that formidable task is Franklin ly legible in the ambient light of our of-

SION (MODEL 10-21 1. Manufactured by Electronic Publishers, a company well fices. The 5 x 7 -dot- matrix display just Franklin Electronic Publishers, Inc., 122 known fcr its electronic reference materi- doesn't cut it anymore. Burrs Road, Mt. Holly, NJ 08060. Price: als. And putting both the Old and New That is, however, the only technical S299.95 Testaments in a handheld device that mea- drawback we found. The program is de- sums only about 51/2 X 5' }: 4 inches and signed for simplicity, and the design works There was a time in our country's not - weighs just 13 ounces it is an impressive as intended. To use the KJ -21, you must too- distant past when it wasn't uncommon achievement. An even mere impressive make one of two types of requests by typ- ior a household to possess only a handful feat, however, is to make easily accessi- ing in information. To begin reading of books, or even just one. One volume ble-even for people who are unfamiliar ( "open" the book) from a specific place in could invariably be found in those tiny with the Bible -all of the wrieings con- the Bible, you can type in a book, chapter, libraries: The Holy Bible. In poor rural tained in all 66 books of the King James and verse (for instance, JOHN 3 16). To households or frontier homesteads. chil- Version. "search" for matches for a phrase or word, dren were often taught to read and write The highligh. of the KJ -21 is its com- you simply type in the words. For in- using the Bible as a primer, and moral and prehensive search capabilities Looking stance, when you key MEEK INHERIT EAR- religious lessons, of course, were based on up words and phrases. and even perform- TH, and hit enter, the words "PSLM" and the same source. Family histories- births, ing advanced search functions, is incredi- "MATT" appear highlighted on the dis- deaths, weddings, baptisms -were re- bly simple. A thesaurus and a phonetic play, indicating that those words appear in corded in the family Bible, and important spelling corrector provide help with un- that order and close to each other in the documents could be found carefully familiar words. Franklin has provided yet Book of Psalms and the Book of Matthew. tucked into its pages. another tool-one that is all- too -often Hitting the enter key again will take you to While it hasn't lost its spiritual place, in lacking in electronic gear -a clear, the first instance of their occurrence this day of inexpensive paperback books, concise, legible, and helpful Tnstruction (Psalms 37: I I -" But the meek shall inher- daily newspapers, books -by-mail clubs, manual. it the Earth; "). To continue reading from and a plethora of magazines, the Bible is The 10-21's front panel contains an that point in the text, you simply use the no longer one of just a few literary works LCD readout that measures appiroximately down arrow for page down. To find the on most bookshelves. And the Bible cer- 4 x 2 inches. The display contains four next instance where those words appear, tainly isn't the only literary work that's lines for text, ,a list of abbreviations for the N (for next) key is used. The pages on been displaced in many homes by elec- each book in the Old and New Testaments, the picture of the book flip as the KJ -2I tronic media, from television and radios to and an ilustration of an open book. Below searches, and in about one second the next personal computers. As a society, we've the LCD is a.QWERTY- style keypad and instance appears on the screen (Matthew become accustomed to switching on elec- assorted function and arrow keys. As on 5:5- "Blessed are the meek; for they shall tronic equipment when we want informa- most hand -held gear, the keys are too inherit the Earth. ") If you'd rather return to Psalms, a touch of the P key brings you back to the previous example. (The pages on the little book flip backwards; backward searches take slightly longer.) That's all you need to know for basic operation of the KJ -21. And, even at that simple level, you have quite a bit of leeway. Unlike most computers, which require that you type in requests in very specific fashions, the KJ -2l is not at all picky. For example, if you want to read from First Corinthians, you have the options of typ-

ing your request as I COR, COR I, ICOR, FIRST COR, COR FIRST, FIRST COR, COR- FIRST, I COR, COR 1, ICOR, CORI, IST COR, COR IST, 1sltOR, orCORIST. If you wanted to read from the second chapter, third verse of that hook, you could type in FIRST COR- INTHIANS CHAPTER 2 VERSE 3 or simply ICO2 3. Similarly, if you were to type in MEAK INHERIT ERTH, the LCD would display "Trying to correct, please wait" and then would bring up four options preceded by flashing numbers: PRESSI. TO USE "MEAT" 2. TO USE "MEEK" 3. TO USE "MAKE" 4. TO DELETE, THEN RETYPE. In the same manner, options are provided for "inhirit" and "erth." In the unlikely event that you were confused by those on- CIRCLE i3 ON FREE INFORMATION CARD screen instructions, a press of the help key (Continued on page 8)

46 Page 4 GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com A Game for All Times

ELECTRONIC CHAMPIONSHIP BACK- GAMMON MODEL 681. Manufactured by Saitek Industries Ltd., 2291 West 205th Street, Suite 101, Torrance, CA 90501; Price: $164.95.

Backgammon certainly has staying power. Its combination of strategy, skill, luck, and gambling has appealed to people around the world for several centuries. Al- though its exact origins are unknown, its likely ancestors date back some 5,000 years to ancient Mesopotamia, as evi- denced by similar games unearthed there by archaeologists. It seems that the Egyp- tians were enjoying a version of the game a few thousand years later, since similar boards dating from 1500 B.C. were found in the tomb of King Tut. A thousand years after that, a backgammon -like game was alive and well in Greek civilization: Plato mentions the popularity of the game, and Homer wrote about it in the Odyssey. ry-has remained popular in the Middle lights up. When it's the computer's turn to The Romans weren't a culture to miss East for thousands of years. and had its ups move (you must press the "Roll Dice" out on a good thing. Called tabulae, or and downs elsewhere. In the U.S., a burst bttton for it), it indicates its move by light- tables, their version of backgammon was of renewed interest in backgammon began ing up LED's in the same manner (you so popular among the upper classes that it with the invention in the 1920's of "dou- must also move its pieces). Unfortunately, was called the sport of emperors. And it is bling," a twist in which the player whose the LED's protrude above the board. We said that Marc Antony and Cleopatra turn it is can insist on doubling the stakes. would have preferred to have the LED's played the game, Caligula cheated at it, His opponent has the ootion Df agreeing to recessed, since they make it difficult to Nero played for stakes as high as (the the increased stakes, or surrendering the slide the playing pieces across the board. equivalent of) $15,000 a point, and that- game at the original stakes. Doubling both Other than that, the checker-like pieces true to the excesses of the Roman Em- added to the excitement (w'th the higher are easy to grasp and pick up, and, since pire -some Romans played a sort of "strip risk) and gave players a quick "out" when they are hacked by magnets, they hold backgammon." a game whose outcome was decided early - their places even when the board is turned While it's likely that the Roman legions on was dragging on. upside down. (Sudden movements, how-

brought tablulae with them as they con- Backgammon remains popular today, ever, can dislodge them.) At 14 x 10V2 x 1 quered most of Europe and Britain -in although it doesn't get the attention of inches, Electronic Champion Backgam- fact, the English version was called "ta- Nintendo -style electronic entertainment. mon fits inside a briefcase, and weighing bles"-it was the return of the Crusaders That's not to say that backgammon and jest under two pounds (batteries not in- in the twelfth century that most effectively electronics are incompatible: Saitek's cludec -and they're not), it is portable spread the game to medieval Europe. Ref- Electronic Champion Backgammon is a enough to carry on board a plane to help erences to "tables" appear in works by fine example of their merger. Incorporat- alleviate boredom on a long trip. Should Shakespeare and Chaucer, and James the ing what Saitek calls "the world's stron- you hear the "Please return your seatbacks First of Scotland is said to have played it gest dedicated backgammon computer" a to an upright position and stow your tray the night before he was murdered. In 16K program), the game is quite versatile. table as the flight attendants prepare for France, where it was called "tric -trac" (for It offers 10 levels of p ay, from novice :o landing," announcement in the middle of a the sound the tiles made against the wood- tournament, and three types of strategy good game, there's no need to despair. If en playing board), specially designed, or- (standard, conservative, and aggressive). you turn the unit off, Electronic Champion nate game tables were popular among the In addition, you can choose between stan- Backgammon will pick up the gams exact- aristocrats in the court of Louis XVI and dard backgammon, and four "common" ly where you left off when you turn it back Marie Antoinette. When the Spaniards, variations: Jacquet, Trictrac, Moultezim, Ott again. (A truly portable version, model who called the game laquet, invaded Mex- and Plakato. (We had never played -or 682, has all the same play options and skill ico in the sixteenth century, they found that heard of-those variations, but we under- levels, but trades off the individual playing the Aztecs played a game so similar that stand they are quite popular in other coun- pieces and comfortable feel for reduced anthropologists cite the fact as evidence tries.) You can play against the computer or size and weight. We prefer to have the that the native tribes of the Western hemi- against another person. and can opt to use ability to move our own pieces.) sphere had migrated there from Asia. The either electronic or regular Bice. A row of 17 buttons running down the earliest recorded use of the name "back- The black -and -silvery-taupe board is right -hand side of the board are are used to gammon" was in 1645, and that was the pressure -sensitive, and automatically regi- start each new game, roll the electronic name used in the next century by Thomas sters each move. To -Hove. you simply dice, select game levels and options, and Jefferson when he recorded his losses at press down on the bar from which you activate some special features that we'll the game in his expense log. want to move, and then press down on the explain later. As you push the buttons, an The game -as we know it and in various bar to which you want to move. Each time LCD readout recessed into the board indi- versions that have evolved through histo- you press on a bar, a red LED at its Up (Continued on page 8)

GIZMO 'Page 5 4 7

www.americanradiohistory.comAmericanRadioHistory.Com supplied with the set. A second cable, with a miniature phone plug on one end and phono plugs on the other, is provided so that you can hook the transmitter up to your portable stereo. While it may seem silly to use wireless headphones with a personal portable stereo, it really isn't. The FM receivers always work better when they're stationary, and portable CD players are notoriously poor performers when they're on the move. The WH -90 transmitter can be powered by a 9 -volt battery for use in portable applications. The headphones are reasonably large, around- the -ear types that mimic the shape of the transmitter-right down to the gold spheres protruding from the side. Unfor- tunately, instead of lending a high -tech look, they tend to make the wearer look a little silly. On the right side, it seems that Nady's original intention was to use the protruding sphere as a channel -selection knob. (Our headphones were still silkscreened with three channel positions, although we assume that later models will not be.) The headphones are powered by two "AAA" batteries that mount in one earpiece. The other earpiece contains the electronics, including the power switch, stereo /mono selector, two reception -indicating LED's (both are on if you're listening in stereo), and a volume control. The CIRCLE 55 ON FREE INFORMATION CARD receiving antenna, a thin, 2 -foot wire, hangs down from that earpiece. The headphones are well balanced, and the get very much work done that way, so we cushioning makes them quite comfort- Private usually end up popping in a casette, in- able, but they're a little heavy for our stead of listening to something new. tastes, and can get fatiguing after about an Broadcasts Well, if there's something that we can hour. And since most of the weight is con- complain about, you can be sure that centrated over, and slightly away from, the WH -90 WIRELESS STEREO HEAD- someone will come up with something to ears, the headphones can pick up a healthy PHONES. Manufactured by: Nady Sys- shut us up. And that's just what Nady Sys- amount of angular momentum if you turn tems, Inc., 6701 Bay Street, Emeryville, tems, Inc. has done with their WH -90 your head quickly -enough that they'll re- CA 94608. Price: $124.95 Wireless Stereo Headphones. Even if quire some re- adjustment every once in a you've never heard of Nady Systems, while. We've all become addicted to portable you've probably already heard some of The transmitter works on the 49 -MHz audio, and we've become so accustomed their products in action. Their wireless au- band with an output power of about 30 to the idea of having news and music wher- dio- transmission equipment for micro - milliwatts. Although that's anything but ever we are that we're often disappointed phones and electric guitars are used by high power, it does provide a healthy when portable equipment doesn't live up such artists as Tina Turner and the Rolling range, which we measured to be about 100 to our expectations. Stones. feet for uninterrupted reception. Personal portable stereo receivers are an The WH -90 consists, naturally enough, Interestingly, Nady doesn't make any essential piece of equipment, and we never of two man devices: a stereo transmitter claims for the range of the headset. Our leave home without one. Unfortunately, that attaches to your home -stereo system favorite application-using the WH -90 to while they all work great in the city, out in (or TV, or anything else with fine -level bring our home audio system outdoors -is the wilds of suburbia where we are, we've audio outputs) and a stereo headçhone re- not what Nady suggests at all. The compa- yet to find one that works as well as we ceiver. The transmitter is a circle with a ny recommends the headphones mainly want it to. We wouldn't really have any diameter of about 43/s inches, although it for around- the -house use. Private listening problem if we listened to the powerhouse has a flat s de that protrudes a bit from the to your TV or stereo so as not to disturb pop music stations. But we're fans of Na- circle. That flat side holds the rear panel, others is the main purpose, and the WH -90 tional Public Radio, obscure college sta- which contains left- and right -channel in- is being marketed against other home tions, and other underpowered non- puts; the 15 -inch telescopic antenna; and wireless headphones that use infrared light commercial outlets. While we're outside an input for an optional ($9.95) AC adapt- to transmit the audio (and are thus limited taking care of our lawn and garden chores, er. A gold- colored half sphere protrudes to line-of-sight use, usually in the same we have a hard time listening to the ra- from the top face of the transmitter to give room). For less private listening, you may dio-every time we hear something inter- it a bit of a high -tech look. An LED in the want to invest another $69.95 for a second esting, we have to stop cutting, or center of the sphere serves as a power-on set of headphone receivers so that some- whatever else we're doing, so that our re- indicator. one else can listen along with you. ception stays clear. Of course, we don't A standard phono -to -phono cable is If you're looking for high -fidelity repro-

48 Page 6 /GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com duction, you may be disappointed by the a second set of speakers to use solely for Korea, Spanish National Radio, and the WH -90 wireless headphones. They are video, especially if you're happy with the like. Many are audible even with the re- subject to interference from a number of performance of your current speakers. If ceiver in its low- sensitivity local mode. devices, (including the computer on which you have a Dolby surround decoder with a When we tried to tune in some of the this is being written). We also had to ex- center -channel output, a single speaker harder-to -get stations, the receiver pre- periment with proper placement of the mounted in the center of the soundstage sented a couple of its few shortcomings. transmitter before we obtained reasonably might do the trick. Using the center chan- First is its relatively coarse tuning incre- quiet results because even your audio nel, which on most soundtracks contains ment of 5 kHz on the shortwave bands. sources can be interference sources as primarily dialogue, makes it easier to hear Off-channel stations (of which there are well. For example, when the transmitter what is being said more clearly during relatively few) cannot be tuned in exactly. was placed too near the power transformer loud passages. More important, it can even with direct frequency entry. (On the of our stereo amplifier, we heard, as you eliminate the "hole in the middle" of AM broadcast band, the tuning increment might expect, a good amount of hum. If widely spaced speakers and create a more is 10 kHz, but can be changed to 9 kHz - you use the headphones for private TV realistic soundfield for on -screen voices the channel spacing that most of the rest of listening, you might get some interference and action. The PS -55CV is a perfect the world uses for AM broadcasts.) The from the TV itself. (You might be better speaker for that application. receiver also suffers from poor image re- off, as Nady suggests, using your VCR as If you haven't integrated your audio and jection; we encountered several spurious the audio source-an especially good sug- video systems, you may be putting up with "images" of stations, especially strong lo- gestion if your TV doesn't offer an audio the typically poor stereo speakers that cal ones. output.) CD players, notorious producers come with most low- and mid -level (and As any shortwave enthusiast knows, of "hash," can be a problem depending on even some high -end) TV's. Adding a even the best receiver can only be as good the transmitter's placement. And even the "real" pair of speakers like the PS -55 will as its antenna permits. Unfortunately, by transmitter's power adapter can contribute help you realize that you really did make their very nature, portable receivers usu- a small amount of hum depending on the the right decision when you shelled out the ally are equipped with antennas that are placement of the power cord. extra money for MIS capability. Of marginal, at best. The SWIS, however, The WH -90 does, however, provide a course. the PS -55CV make pretty good includes a good compromise -a portable convenient way to enjoy some of your sta- surround- channel speakers, too. active antenna. tionary audio sources while you move It's been ten years since Dolby Labora- The active antenna is a 45 -l/2 -inch tele- around. If you're willing to put up with tories developed the Dolby Surround scoping element on a 3 -1/4 x 3 -3/4 x less -than- audiophile -quality sound for the home surround -sound system, one of the I -1 /4 -inch base (which holds the 4 "AA" sake of convenience, then add Nady's driving forces behind consumers' interest batteries that power the antenna). Thanks WI1 -90 to your must -have list. in better video sound. It's been about to a l2 -foot connecting cord (which is seven years since the FCC authorized ster- stored in the base on a very convenient, eo- television transmission. If you have yet self-contained take -up spool), you can DID YOU HEAR WHAT WAS ON TV to upgrade the sound of your video sys- mount the antenna near your hotel window (Continued poree frort , tem, we can't think of any reasons for you while you sit in the comfort of your listen- to wait any longer. And the PS -55CV vid- ing position. A small, rubber suction cup Hz, and a power-handling capability of 70 eo speakers are a good way to start. supplied with the system can hold the an- watts. The cabinet, finished in black -ash tenna in any desired position. vinyl, measures a compact 7 x 101/4 x O The antenna connects to the receiver A inches, and houses a 51/4-inch woofer and SW(eI)L RECEIVER through the antenna controller. The con- ;/r -inch ferrofluid -cooled dome tweeter. r mrtinued from page ¡) troller plugs into the receiver via the re- The most common way to upgrade a ceiver's tape -record jack, which is video system's audio is by integrating an buttons. A scan start; stop button allows normally used for direct output to a tape existing stereo audio system into the video you to search for new stations (tuning recorder. (The controller brings the record setup, and using the stereo system's ampli- stops automatically when a strong- enough output straight through to a jack on the fier and speakers. Although that's a good signal is found), and a key -protect button, opposite side.) The record jack is used first step, it doesn't work as well as you once hit, locks out any accidental key only as a kind of friction -fit device as far as might expect. The biggest problem is presses. Of course there's an on /off the antenna is concerned. The actual an- that -unless you have a huge projection switch, but there's also a sleep switch to tenna connection is via a small pin that screen -your stereo system's speakers are automatically shut down the receiver after makes contact with the tip of the telescopic probably in the wrong place! The proper an hour. antenna. A small switch on the face of the speaker location for music listening is not The receiver is powered by either two controller turns the power on and off. Un- the same as for video entertainment, "AA" batteries or the AC -power adapter. fortunately, the receiver's on /off switch where you don't want the same wide There are two power switches on the unit. has no effect on the antenna controller - soundstage. Video speakers should be in- One is a slide switch on top of the receiver. nor, of course, does the sleep function. stalled relatively close to the sides of your Sliding it to on puts the receiver in its Also, unfortunately, the power for the ac- screen, so that on- screen sounds don't standby mode; its not really on until you tive antenna must be supplied by its bat- sound as if they're coming from the other touch the front panel on/off key, While that teries; we would have preferred if the AC side of the room. may sound like an annoyance, it's actually adapter could also be used for that. Unfortunately, you can't install ordi- a most welcome feature, especially for If you've never given shortwave listen- nary speakers too close to your video travelers. You don't have to worry about ing a chance, you really should. But the screen because of the permanent magnets the receiver being turned on by another SWIS should not be your first receiver - in the speakers. If the magnetic field is object pressing a button while it's packed there are better and less expensive (al- strong enough, it can distort the picture or away in your luggage, and ending up at though much larger) models on the market the color of your TV screen. Like other your destination with dead batteries. that the SW IS is not meant to replace. We, speakers meant expressly for video ap- When used by itself, the ICF -SW1 is a of course, have long been fans of NAorld- plications, the PS -55CV are magnetically competent receiver. On the shortwave band radio, and we'll continue to listen "shielded" (actually, "compensated" is bands, it has no trouble picking up such both in times of peace and of war. The only the better word). well -known powerhouses as the BBC, difference is that now. we can also listen We're not going to suggest that you buy Voice of America, Radio Moscow, Radio when we travel.

GIZMO Page 7 4 9

www.americanradiohistory.comAmericanRadioHistory.Com out" again to return to more general heavily involved in Bible study and who AT THE MOUTH SHOOTING OFF screens, respectively. Those two keys are teaches a Bible class to 8- year -olds. Her (Continued from page 3) used for several operations. One is exiting reaction to the electronic Bible was that the the help function, as described above. An- search capabilities were impressive-but difficult to forget that you're wearing them other is to use the pronunciation function. for general study and casual reading, she as you get caught up in the game action. When unfamiliar words (most frequently, prefers the Bible in book form. Her stu- Once we discovered that soft sounds proper names) appear in the text, they are dents, on the other hand, thought the worked as well as shouted commands, we often followed by a superscript P. That KJ -21 was "really cool" and a terrific way could play for hours on end without voice indicates that pronunciation help is avail- to study the Bible. We'd expect it to find fatigue. Our ears did take a beating -the able; by pressing the enter key you will see easier acceptance among kids, who are headset definitely is meant to fit smaller both the phonetic (using accepted diction- already so accustomed to using all sorts of heads-and an hour or so of continuous ary symbols) and the "newspaper- style" electronic equipment and are eager to use play resulted in stiff necks. While we never (to help you "sound out" a word) pronun- new forms of communication. got to the point where we mistook our sofa ciations of that word. (For instance, the We hate to sound like the older genera- for the cockpit of an army helicopter, we newspaper-style pronunciation of "Juda- tion, but we, too, like the feel of a hefty did enjoy the relative ease and accuracy ea" is "joo- DEE -uh." A list of phonetic tome, enjoy flipping pages, jotting notes with which the LaserScope works. symbols is provided in the manual.) A in the margins, and reading the printed As a bonus, the headset can also func- superscript "N" following a word indi- word. Those simple pleasures can't be rep- tion as spare headphones for your personal cates that the word's archaic meaning dif- licated in a handheld device with an LCD stereo, radio, or Game Boy (although you fers from the modern one; pressing enter in readout. And, of course, we'd have a hard wouldn't catch us wearing it in public). A that case will call up a definition of the time trying to store our family's birth cer- slide switch on the side of the headset is word as it appears in context. tificates or marriage licenses between the used to change between NES and stereo The advanced operations, for the most electronic "pages" of the KJ -21. While the modes, the mouthpiece swivels out of the part, center around the KJ -2l's ability to KJ -21 makes an excellent reference tool, way, and the eyepiece snaps off when it recognize words and concepts that corre- we can't imagine it replacing the written isn't needed. The LaserScope wouldn't be spond to each other in some way. For in- Word-although the kids might disagree. our first choice for music listening. The stance, when the word "water" is typed audio quality is certainly adequate for lis- followed by a single question mark, the tening to Nintendo sound tracks, and the word's entire "family" is brought into the kids probably won't have any complaints search. That includes singular and plural A GAME FOR ALL TIMES listening to their rock and roll. But these forms of the noun "water," all tenses of the (Continued from page 5) are not headphones for serious listening. verb "to water," some synonyms ("sea "), Our only other complaint (and bear in and even compound words like " water- cates the corresponding data. For in- mind that this is coming from non -parents) pot." You can type a question mark after stance, when you press the roll -dice key, stems from the fact that for best results we one, several, or all of the words in a the display will show your roll in the form tended to keep the microphone practically search, or you can go to the menu and of two dice; as you make each move, the touching our mouths as we played. When a select the " ?" option. Either method will corresponding die is removed from the dis- multi- player game is in progress, the con- cause a list of related words to scroll by play. The LCD also indicates whose turn it trols are passed from player to player in and then the number of family members is is by displaying a small black or white turn-not what we'd consider to be a very displayed. Using another menu option, playing piece, and what the stakes are by hygienic arrangement. (Although kids do "Approval," allows you to select which of displaying a tiny number in the upper-left tend to share their sodas, food, etc., any- those related words you want to include in corner. way.) the search, and even to view related When selecting game level and options, That's a small price to pay, in any case, phrases from the Thesaurus. repeatedly pressing the reject button for a device that offers a lot of fun and a The "word family" recognition ability, causes the unit to scroll through each op- quiet game room -for a small price. At made possible by Franklin's algorithms, is tion, and the LCD indicates each option in less than $40, the LaserScope will be a what makes the KJ -21 something more turn (GO for normal backgammon, GIG4 welcome addition to many Nintendo sys- than a book. It offers an array of new for the variations, HO for standard play, HI tems. We have to run now -we have only a possibilities by instantly answering ques- for conservative, H2 for aggressive, and few hours before the rental is up on our tions that couldn't easily be satisfied be- LOL9 for beginner to expert playing lev- Nintendo, and we're dying to get in a few fore. The search functions display els). When your choice appears on the more games! centuries old words in such a way that display, you lock it in by pressing the dou- interrelationships and structures can clear- ble /accept button (which is also used when ly be seen. you want to double the stakes). While that We here at Gizmo don't have the exten- sounds easy enough, it's not intuitive, and SEARCH AND YE SHALL FIND sive background required to understand or the instructions in the manual are anything (Continued from page 4) evaluate the literary structure or the inter- but helpful. relationships between Books of the Bible. The special features-in particular, the calls up further instructions: "Press one of As writers, however, we found the KJ-21 to statistics function -are educational tools. the blinking numbers to make your selec- be a handy tool for finding quotable When you press the statistics button once, tion, or press EXIT to return to the Re- phrases on a variety of subjects. Our un- the display shows which player is ahead, quest Line." Another press of the help familiarity with the Bible, however, led to and the pipcount by which he, she, or it is button lets you know that you are looking a few instances where we got "lost." For winning. The pipcount refers to the total at a help screen and to use the exit key to instance, we wanted to read the Sermon on number of points that a player must move return to the main screen. the Mount, but didn't know what book it his men before they are all off the board. The manual explains -for those who was in. "Sermon on the Mount" is not When in the statistics mode, repeatedly are totally unfamiliar with electronic refer- recognizable, and neither is "Beati- pressing the verify key will first show the ence sources -the basic functions of the tudes." Luckily, we knew that part of the score of the game, and then will cause the KJ-21 as can be accessed using the enter Beatitudes is "Blessed are the poor," and computer to scan the board and show the and exit keys, which "zoom in" to call up were able to search for that phrase. chances of each single game piece more detailed information and "zoom We loaned the KJ -21 to a friend who is ("blot ") being hit ( "pinned "). If you then

50 Page 8 /GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com push the roll -dice button, the LCD will less than a minute to verify the whole than we did, but we won enough games so indicate precisely which dice rolls will pin board. that we felt fairly evenly matched. When, that blot; if you keep pressing verify, every Other than the LED's that stick out of in the midst of an extended losing streak, possible roll will be shown. Using the sta- the board, our only complaint about the we began to wonder if the computer was tistics key teaches you about how the odds design of the board is that you must lock "cheatirg" by giving itself all the lucky can work for or against you, and can help closely to find the bear off key -which rolls, we were able to use the manual dice you find a move that gives the computer must be used on almost every move at the option (rolling the included set of dice and the least opportunity to pin one of your end of each game -among all the other then inputting the roll using the six dice men. buttons. We'd prefer to see it set either keys on the side of the board) to keep the Similarly, if you've rolled the dice but slightly apart from the other keys or at the game honest (and to let us cheat if we you're not sure what move to make, hitting top of the column of keys, or made larger wanted!). the play button causes the computer to or in a different color, so that it could be Saitek is not the first to use feats of switch sides and play that move for you. distinguished at a glance. engineering to enhance the game of back- That way, you can learn what the recom- In one of those unfortunate ironies to gammon. The ancient Egyptians, to guard mended move is for a certain situation. If which we should be accustomed by now, against cheaters, invented a mechanical you'd rather not take the computer's ad- the ease, convenience, and good design of dice box that shook and rolled out the dice. vice, you can press play a second time, and Electronic Champion Backgammon is in- Nor is Saitek the first to come up with an the move is displayed by the LED's, but is versely proportional to the quality of its easily transportable game board. The Ro- not executed. user's manual. For example, we found that man emperor Claudius had a tabulae table The verify key, which is used to make trying to select the various game options mounted on his chariot so that he could sure that all the playing pieces are phys- according to the manual's instructions is play while on the road (although it's highly ically located in the positions that the com- particularly tricky, and, further, the direc- unlikely that he had magnetic game puter thinks they should be, comes in tions for using the statistics function er- pieces!), and, 150 years ago, riverboat handy when you return to an interrupted roneously says to use the accept key to gamblers on the Mississippi used a porta- game (particularly if the board was put in access detailed statistics. ble backgammon set. its case and carried around before resum- Once we managed to figure it all out on And that brings us to the one important ing play). At each press of the verify but- our own, however, the game went smooth- thing that is missing from Electronic ton, the LED at the end of an occupied bar ly, and we had a great time with it. The Champion Backgammon: The pay -off. lights, and a number on the LCD readout differences between the "aggression" When you're playing against a computer, lets you know how many men should be on modes are subtle, but they do change the you're not going to win or lose any real that bar. As you continue to press verify, feel of the game enough to make it seem as money, and that takes some of the edge off the computer works its way around the though you're playing against different op- the game. Oh well, at least we'll be more board, stopping at each bar that has (or ponents. experienced players the next time we do should have) playing pieces on it. It takes The computer tended to win more often play for money.

For more information on any product in this section, circle the appropriate number on the Free Information Card. ELECTRONICS WISH LIST

Top -of- the -Line Tape Back in 1968, TDK Electronics Corporation (12 Harbor Park Drive, Port Washington, NY 11050) introduced the "SD," a high -fidelity cassette that cost about three times more than any other tape on the market. While it never became a mass- market hit, it found a niche with deep- pocketed audiophiles. TDK is out to recapture that same market with its MA -XG audio cassette. Claimed to be both "the first metal tape to achieve the seemingly contradictory goals of low bias noise and high output" and "the world's first dual -layer (Type IV) audio cassette," the MA-XG combines two separately tuned layers of ultrafine Finavinx magnetic particles to create an audio cassette with - 59 -dB bias noise and +75 dB at 315 Hz output. The tape is housed in the "Reference Standard IH (RS- III)" mecha- nism, which uses a five -piece design with dual -layer face plates made of non -rigid TDK High -Quality Cassette Tape plastic (for resonance reduction) and fiberglass- reinforced plastic (for strength). The housing is also designed to ensure maximum vibration attenuation and the highest degree of azimuth accuracy. Price: 60- minute: $15; 90- minute: $18. CIRCLE 56 ON FREE INFORMATION CARD Roll-top Disk File We're always on the lookout for places to store all the little gizmos that go along with the high -tech life. Rolvkit, Inc. (303 E. Wacker Drive, Suite 412, Chicago, IL 60610) offers an attractive way to store as many as 80 31/2-inch diskettes. Their Rolydata disk file has a sleek, roll -top design with anti -skid feet and a built -in carry handle. It comes with eight section dividers and divider labels to help organize the disks. Rolydata features a patented, dust -proof roll -top enclosure to protect the disks, and comes with a metal key -lock. Pretty soon we'll need a larger office in which to store all our storage gizmos. Price: $29.95. CIRCLE 57 ON FREE INFORMATION CARD Roll -Top Disk File

GIZMO /Page9 51

www.americanradiohistory.comAmericanRadioHistory.Com For more information on any product in this section, circle the appropriate number on ELECTRONICS WISHL IST the Free Information Card.

Language Course, Language Course Traditionalists in the field of education ha%c long favored ti i i i by rote. Even those of us who were taught the new math" can remember learning the "times tables through endless repetitions of "Three times one is three, three times two is t. three times three is nine... " Sony Corporation of America (Sony Drive, Park Ridge, NJ 07656) is applying the same basic concept to teach foreign languages. Consisting of a course work package and a portable audio-playback unit that can be used for self-paced study or to reinforce classroom instruction. the Repeat Learning System is a new method of language learning that emphasizes memo- rization of short, conversational sentences through repeated listening. What sets Sony's system apart from cassette -based systems. is that the spoken dialog is recorded on cards with a thin magnetic strip similar to the one found on credit cards. When the cards are run through the Repeater. it will automatically replay the phrase up to 100 times. with no nne rewinding between repetitions. Set on manual mode. it replays once at the touch of a button. The first program developed for the system. "Natural Japanese... is offered in two levels. The basic course covers greetings. requests. and phrases used in shopping and banking: the intermediate course builds on those basic skills to teach conversation appropriate in different business situations. Each level consists of ISO Repcatcards: a textbook Sony Repeat Learning System that provides grammatical explanation, usage guidelines. Japanese characters. and information on Japanese culture and social interaction: and an audio cassette tape of a series of extended practice dialogues. Other programs include tour levels of American English and a Chinese course for Japanese -speaking people, as well as French. Spanish, German. and Italian for English- speaking people. Price: $179.95 -.5219.95 for the Repeater Playback Unit and 5149.95 -$ 189.95 for each language course. CIRCLE 58 ON FREE INFORMATION CAFD

Extended- Memory Universal Remote If Mother Goose's tales sere to be updated for the nineties_ we might hear something along the lines of "There was a young yuppie who lice,' in a condo. He had so many remote controls he didn't know what to do." (Okay, so we're not poets!) .lasso Products Company otters a happy ending, of sorts, in the form of their Model HE 8257 extended -memory remote control. It is preprogrammed to work with up to eight electronic devices: the old remotes are not necessary since it uses preset codes. The device is designed to tit comfòrtably in either the right or the left hand, and promises to take only seconds to set up. Price: $89.95. CIRCLE 59 ON FREE INFORMATION CARD Jasco Extended -Memory Remote

Into the Computer Age Smith Corona (65 Locust Avenue. New Canaan, CT 06840). long a leader in the electronic typewriter and word -processor field, has introduced "the logical progression," a line of seven personal computers developed jointly with The Acer Group. The "plug -in- and -go" systems, designed to be easy to use and expandable, are aimed at first -time users in home, school, small- business. and home - office environments. The IBM -PC compatibles contain built -in application software and an opening menu that guides users through the computer's functions. Other convenience features include a spell checker, thesaurus, personal diction- ary. and address merge. The PC's are equipped with "the latest version of MS- DOS," and include a DOS shell that has been enhanced to provide users with quick access to frequently used DOS commands. as well as GW- BASIC. Self- Diagnostics, and QuickLearn tutorials. The Smith Corona Acer line includes six 80286 -based systems, including three ROM cartridge models and three hard -disk drive models, and one 80386 model with hard drive. Each is available with eithera VGA monochrome or VGA color I4 -inch monitor, along with two serial ports, one parallel port, a 101 -key keyboard, 31/2 and/or 51 -inch floppy driers. and two expansion slots. Shown here is the lowest -priced model. PC 100. Price: $999.99. Smith Corona Personal Computers CIRCLE 60 ON FREE INFORMATION CARD

52 Page 10 GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com For more information on any product in this section, circle the appropriate number on the Free Information Card. ELECTRONICS WISH LIST

Infinitesimal Micro No, ware not talking about this season's skirt lengths. Infinite Se.uerns, hie. (9409 Owcnsmouth Avenue. Chatsworth. CA 91311) is resurrecting the name of their respected Infinitesimal series from a decade ago and has given their passive three -way subwoofer satellite system the name tnlinitryi,nu/;41icro. The compact set is designed to "physically hide yet sonically shine." The 4.8 x 4.8 x 7.6 -inch Micro satellite has a frequency response of 150 Hi to 20 kHz at ±3 dB. When used with the 20 x 7.25 x 11.38 -inch subwoofer, hass response extends down to 50 Hz. The subwoofer features an 8 -inch dual voice -coil woofer that radiates into a vented enclosure, a format that requires less cone motion to reproduce low frequencies for reduced distortion, and improved sound efficiency. Price: 5519.95 (sold seprately: satellite speakers. S295,95rpair: subwoofer $269.95). CIRCLE 61 ON FREE INFORMATION CARD

Picture Perfect For the past few decades, we've been hearing the wall -mounted TV monitors "will he reality.. in ten more years." It took quite a hit longer. but Sharp Corpora lion (22 -22, Nagaike -cho, Abeno -ku, Osaka 545. Japan: Sharp Electronics Cor- poration, Sharp Plaza, Mahwah. NJ 07430 -2135) has just introduced a line of Infinity Subwoofer Syste+-n eight wall -mount color TV monitors -in Japan. The 91 : -H Series, which each feature an 8.6 -inch. high-contrast, full -color LCI) panel. are being marketed as the "Liquid Crystal Museum." Developed to create an impression of "equipment as art," they are intended to enhance a room in the same way Lis pieces of art. Each model incorporates the same LCD, but different styles of frames" complement various interior design styles. A compact tuner can he integrated into the "Crys- tal" and "Art' models. allowing the entire system to hr wall- mounted. "l'he LCD monitors deliver a contrast ratio of more than 60:1 and high image resolution is achieved by a 156 x 960-pixel image and a double -speed scanning system. Per- haps it will become reality here in the states in "a few more wars." Price: Not available. CIRCLE 62 ON FREE INFORMATION CARD

Headset Amplifiers rking the "natural" approach to sound amplification, National Market Waken', Inc. (P.O. Box 21RS, I nice. CA 90294) came up with Ear Lenzes, a sound -detail amplifying headset that requires no electricity. Resembling headphones. hut with black -plastic halt-shells that fit behind the wearer's ears instead of speakers placed over the ears. Far Lenzes "can make everything from home - stereo systems and TV sets to live music performances sound better to the Sharp Wall -Mount LCD Monitors wearer,' according to the inventor. The open- fronted shells reflect. focus. and amplify' sound details from any source of sound in front of the wearer. In tests performed by National Market Makers (using a dummy head with microphones in place of ears), they delivered up to eight decibels more sound details to the wearer's ears, and block 555% of the sounds from the user's sides and rear. The company compares the product's aural benefits to the effect that binoculars have on sight. and states that while a similar effect can be achieved "simply by cupping one's hands behind one's ears ...with the Ear Lenzes headset, your arms won't get tired." (We tried them, and were overwhelmed he how loud the laughter sounded from anyone who saw us wearing them.) Price: 512.95 (plus $2.00 postage). CIRCLE 63 ON FREE INFORMATION CARD

Game Boy Wrestling Fans of hig -time wrestling can safely experience thrills, spills, pins, and holds

with Hal Amer, t a's (7873 S.W. Cirrus Drive, # 25 -E Beaverton, OR 97005) Hal Wrestling video ganrc for the handheld Game Boy. Players can program the game for one -on -one or tour -man team wrestling. Players can pit themselves against the computer or against another player via a video link. or select a four -man team and squad. The field of "athletes" pit the group against a computer-selected four -man 4191/ W. ffff ® includes wrestlers like King Sampson, The Big Crusher, and The Death Monster. Price: $28.95. Hal CIRCLE 64 ON FREE INFORMATION CARD Wresting Video Garne

GIZMO Page 11 53

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61 -Inch Projection TV If you've been putting off buying a home- theater system because it will take up too much floor space, you might want to look into Philips Consumer Electronics Company's (One Philips Drive, P.O. Box 14810, Knoxville, TN 37914 -1810) 6/MP60 WallVision projection television system that can operate as a stand -alone set or can beinstalled directly in the wall as part of an integrated entertainment system. The system features only one accessory kit, which includes a color- enhancement filter, side speaker grilles that fit over the wall- speaker cabinets, a decorative speaker grille for the speaker located below the screen, and an air dam that controls the internal air flow through the system. The 61MP60 has center- screen output jack panels, LCD learn remote control, color picture-in- picture, 50- watt Dolby Pro -Logic Surround Sound system, parental control, and channel guide. Also included is a comprehensive installation guide and a 15- minute videotape that explains wall construction, audio- and video -component hookups, wiring during installation, proper ventilation, and installation of the door on the optional cabinet. Price: $3,799. (The accessory kit and in -wall cabinet are sold separately.) CIRCLE 65 ON FREE INFORMATION CARD Compact Metal Detector Philips Projection TV Traveling treasure hunters will appreciate Fisher Research Laboratory's (Dept. P-E, 200 West Wilimott Road, Los Banos, CA 93635) 1266-XB metal detector, which disassembles to fit into a small carrying case. Virtually identical to the popular model 1266 -X, the 1266 -XB differs in that it has a three -piece break -down handle and comes with a hard carrying case. The 15 .< 21 x 6 -inch case is small enough to act as carry-on luggage on most airlines. Features include twin VLF- slow- motion trash -reject modes; silent, no threshold operation; patented double - derivative, quartz -crystal locked electronics; near perfect balance; cushioned arm rest and grip; and an 8 -inch, open -center, lightweight "Spider" coil. Price: $650. CIRCLE 66 ON FREE INFORMATION CARD Car Subwoofers For those who want their car-stereo components to look and sound good-and still have enough money left to fill the tank -International Jensen Inc. (25 International Tri-State International Office Center, Suite 400, Lincolnshire, IL 60069) offers the JW1500 15 -inch subwoofer. It features a frequency response of 20 Hz to 2.1 kHz, with sensitivity of 94 dB. It has a continuous power-handling capability of 150 watts rms. Updated cosmetics include wet -look cones and dust caps featuring the company's logo with red, white, and blue accents. Price: $99.95. CIRCLE 67 ON FREE INFORMATION CARD Fisher Metal Detector "Chameleon" Multi -Room Controller The chameleon -like Beolink 7000 infrared system controller from Bang & Olufsen of America, Inc.'s (1150 Feehanville Drive, Mt. Prospect, IL 60056) automatically configures its controls and displays to match the audio or video source being used at the moment. Using touch panels instead of buttons, the device commands virtually all functions of Bang & Olufsen audio /video systems. Its motorized operating panel automatically tilts up for easier access, and only those controls that are needed appear on the panel. The Beolink 7000 never presents extraneous controls that might cause confusion, which makes it easy for a consumer to operate even the most sophisticated whole -house audio /video systems. A built -in microcontroller memorizes the unique configuration of the owner's components and systems throughout the house. Then, it presents only the sources and control options possible with that particular system. Special command sequences can be programmed, and special functions are available (timer programming is possible even in components that don't integrate that feature). The Beolink 7000 provides full two -way interactive operation with the Beosystem 2500 music system, Beosystems 4500 and 6500, the Beocenter 9500 music system, and the Video System 5500; can control room lighting with optional accessory units; and will be able to control future Bang & Olufsen products yet to be designed. Price: $1000. Bang & Olufsen Multi -Room Controller CIRCLE 68 ON FREE INFORMATION CARD

54 Page 12'GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com The Electronic flJly

(Ike your t,e_rt prox,:t a trbs unto°ì

Here's a riddle for you: What "wings" attcehed. he wings are matie we can begin to discuss how the circuit makes an excellent inexpen- of a material callec giezoe'ectric film- - wor

www.americanradiohistory.comAmericanRadioHistory.Com BEND ORIGINAL LENGTH

LAYER #1

LAYER #2

LAYER #2 SHORTER T CRYSTALINE'. DIPOLE T DIPOLES ALIGNMENT LAYER #1 HIGH LONGER VOLTAGE

Fig. I. A dipole has a natural opposite polarity on either end (A). A voltage potential causes the dipoles to align, and the material to change in shape (B). When a potential is placed across two layers of piezoelectric film, the film will bend (C).

The manufacturing procedure of one layer to expand while the other T1's primary) is applied back to the base piezoelectric film is such that dipoles contracts. That, in turn, causes the film of Q1 via R1 and S1, turning it off. That are produced in the material's crys- to bend. When the voltage polarity re- stops the current in both the primary talline structure. A dipole is a molecule verses, the film bends in the opposite and secondary, allowing the base of that has a natural opposite polarity on direction. Now that we know how the Q1 to go low again. As long as S1 re- either end (see Fig. 1A). The film is then wings are made to flap, lets see how the mains closed, the cycle will repeat itself. metallized on either side so that a volt- circuit creates an AC signal that causes Diode D2 and capacitor C1 rectify age potential can be placed across them to do so. and filter the low- voltage AC from T1's the film. As shown in Fig. 1B, the applica- center tap to provide + 5 volts DC to tion of voltage a causes the dipoles to A Look At The Circuit. The schematic power a 4011 quad 2 -input NAND gate, align, and the material to change in for the Electronic Dragonfly is shown in U1. Diode D1 and capacitor C2 rectify shape (as it gets thinner, it gets longer Fig. 2. An AC signal of approximately 10 and filter the high -voltage AC from pin and wider). kHz is created by battery B1, transistor 3 of T1 to produce about260 -volts DC to The dragonfly wings are made of two Q1, transformer T1, resistor R1, and push- operate the piezoelectric wings. Al- layers of the piezoelectric film with op- button S1 in the following manner. though 260 volts is nothing to snicker at, posite dipole orientations (see Fig. 1C). When S1 is pressed, Q1 turns on, draw- the current is low enough so that there's Because the poles of the outer metal- ing current from the primary side of T1. A no real danger; resistors R3 and R4 limit lized surfaces are now the same, a volt- rising pulse from pin 4 of T1's secondary current in the event that T1 accidentally age placed across the surfaces causes (which is of higher voltage than that at gets shorted. --o o-----yVb- S1 R1 91f2 01 D1 R4 MPSA56 1N5397 1MEG

C2 I, R3 1 T1)3 D2 1 MEG 11030 °-4 ---i-- PIEZOELECTRIC +5V B1 2 15 +5V 15VT FILM WINGS

11 )1 = Cl 1/44011 .1

R5 Q3 100K MPSA42 MPSA42

1 OOK

Fig. 2. The schematic for the Electronic Dragonfly. When SI is pressed, the wings flap up and down.

www.americanradiohistory.comAmericanRadioHistory.Com quirements, the only alternative to using the transformer that comes with the kit (unless you can find one that t- provides the same outputs), is to wind one yourself, and that's going to be very difficult; plus, the wire will be expensive and hard to find. Two other advantages to purchasing the kit are thatyou'll get a pre- etched and drilled printed- circuit board and a colorfully laminated dragonfly body, as well as the piezoelectric - film wings. For you die -hard do- it- yourselfers (who simply must "roll their own "), the transformer must be wound on a silicon -steel core; the windings are as fol- lows:

From pin 1 to pin 2, wind 6 turns of 24- gauge enameled wire. From pin 3 to pin 5, wind 12 turns of 4 INCHES 33 -gauge enameled wire. Fig. 3. You can make your own printed -circuit board from this foil pattern. From pin 3 to pin 4, wind 1300 turns of 44 -gauge enameled wire. No, 1300 turns is not a misprint, and for those of you brave enough to take on the task of winding the transformer, *PIEZOELECTRIC good luck! WINGS Whichever way you decide to go, it is recommended that the circuit be assembled on a printed- circuit board; printed- circuit construction makes assembling the project a lot easier and R2- makes for a much neater finished ap- s1 pearance. For those of you who want to do everything from scratch, a full -size template for the printed- circuit pattern 'DRAGONFLY R1 SUPPORT is shown in Fig. 3. Solder the parts to the -C3- WIRE printed- circuit board as shown in the parts-placement diagram in Fig. 4. In- stall them in the order that they're shown in the Parts List so that you can check off each part as it's installed. 'SEE TEXT Be sure to observe the proper polar- Fig. 4. Solder the parts to the printed -circuit board as shown here. Note where the ity of all the transistors and U1. Because support wire solders to the hoard. U1 is a CMOS device, we recommend that a socket (which is included in the A low- frequency oscillator circuit of piezoelectric film wings low, which kit) be provided for that component. If about 10 Hz is formed from U1 -a, U1 -b, causes the dragonfly wings to flap up you are not assembling the project C3, and R6-R8. The frequency of the and down. from a kit and can't locate the tran- oscillator-which is the rate at which sistors and diodes shown in the sche- the wings will flap -is adjustable via po- Construction. For mainly Iwo reasons, matic diagram, alternative units are tentiometer R7. The output of the os- it's best if you purchase the kit for the listed in the Parts List. Proper soldering, is cillator is fed to the input of U1 -d, which dragonfly. For one, the piezoelectric as always, is a must. After the board it sol- is configured as an inverting buffer. The film will be pretty expensive in the finished, carefully inspect for any output of U1 -d is used to drive both the quantities that are available. And two, der shorts, opens, cold -soldered leads, base of Q2 via R2 and the input to J1 -c, the transformer used in the circuit is a and heavy -flux buildups. which, like U1 -d, is set up as an inverting very specific part. It must take the 1.5- The battery holder is mounted to the buffer. The inverted output of U1 -c is volt input applied to its primary (at pins board using some double -sided tape. used to drive the base of Q3, causing its 1 and 2) and generate about 5 volts at Observing the proper polarity, the drive signal to be 180 degrees out of pin 4, and about 260 volts at pin 3 (aller leads from the battery holder are sol- phase with that applied to Q2. Because being filtered and rectified, of course). dered to the plus and minus pads the base inputs of transistors Q2 and Q3 Also, pin 4 supplies the feedback pulse (points A and B in the kit) on the printed - are 180 degrees out of phase, they al- that shuts off the transformer, thus caus- circuit board. The dragonfly body that ternately pull opposite sides of the ing the oscillation. Because of those re- comes with the kit is a colorfully lami- 57

www.americanradiohistory.comAmericanRadioHistory.Com PARTS LIST FOR THE ELECTRONIC DRAGONFLY

SEMICONDUCTORS Ul -CD4011 quad 2 -input NAND gate, LEAD SOLDERED integrated circuit TO COPPER -FOIL TAPE QI- MPSA56, 2N5401, SK3466/159, TCG/NTEI59, ECG159, or equivalent PNP silicon transistor Q2, Q3- MPSA42, ECG287, SK3433/287, TCG /NTE287, or equivalent NPN silicon transistor DI- 1N5397 (or similar) 3 -amp, 600- Ply silicon rectifier diode D2 -1K60, SK3090, 1N34A, 1N60, or similar germanium diode RESISTORS B (All fixed resistors are 1/4-watt. 5e; Fig. 5. If you're not building the project from a kit, an actual -size template for the units.) dragonfly body is shown in A. Shown in B is an actual -size template for the wings. R1 -91 -ohm Remember to use double -laver piezoelectric film. R2, R5, R6, R8- 100,000 -ohm R3, R4- 1- megohm R7- I- megohm, PC- mounted miniature potentiometer CAPACITORS

DRAGONFLY CI- 0.I -1.LR ceramic -disc BODY C2- .0l -µF, ceramic -disc C3- .068 -µF, Mylar ADDITIONAL PARTS AND MATERIALS TI- printed- circuit -mount step-up transformer with center tap text) PIEZOELECTRIC (see FILM WINGS DOUBLE-SIDED SI- printed -circuit -mount pushbutton TAPE switch B1 -1.5 -volt AA battery Printed- circuit materials, double -sided piezoelectric film, 14 -pin IC socket, bus wire, hook -up wire, battery holder, double -sided tape, rubber feet, solder, hardware, etc. Note: The Heathkit Dragonfly (kit SK -118) is available for $21.95 from Heathkit, Heath Company, Benton Harbor, MI 49022 (800) 253 -0570. COPPER -FOIL TAPE The kit includes everything in the Parts List except the AA battery. BUS Piezoelectric film is available from WIRE Atochem North America, 3 Parkway, Philadelphia, PA 19102. Contact them directly for pricing and other information.

DOUBLE -SIDED FOAM TAPE for the wings is shown in Fig. 5B. If you can't find double -layer film, try folding over a single -layer piece holding the Iwo sides together with some adhesive. Fig. 6. The wings are held onto the body (as shown here) with double -sided tape, and the Then cut out the wings from that. dragonfly is held onto the support wire with a piece of double -sided adhesive - backed Pain Making rubber. electrical contact to the film is a bit tricky. If you are making the wings nated piece of cardboard. It really Also if you're not building the project yourself, you obviously can't solder a spruces up the appearance of the from a kit, you're going to have to fash- lead to the film -the solder will melt finished project. If you're not building ion the wings yourself. You'll need some right through the film. To make elec- the project from a kit, you're going to double -layer piezoelectric film cut into trical contact, you'll have to use some have to improvise where the body is the shape of dragonfly wings. We've copper -foil tape. The tape, which is concerned -an actual -size template provided a source for the film in the used to repair PC -board traces, has a for the body is shown in Fig. 5A. Parts List, and an actual -size template (Continued on page 93) 58

www.americanradiohistory.comAmericanRadioHistory.Com All about Receiver

Sensitivity 411.121102. Learn about the different ways receiver sensitivity is measured and specified, and what each specification really means.

BY JOSEPH J. CARR

George was both a professional active stations (with the mute function ohm resistance system, P is on the communications technician off, if one is present). order of 10 -13 watts, so the noise from and a ham -radio /shortwave Noise can come from several dif- this source is not a large number. How- enthusiast. He had a brand new gener- ferent sources. There is incoming noise ever, it also cannot be overcome no al- coverage shortwave receiver that that is picked up by the receiver anten- matter how "ideal" the receiver is. was top -of- the -line for the day (I won't na (for example, noise generated by Figure 1 shows the detection prob- say what model -it'd date me!). galactic and solar activity), and noise lem graphically. Given a noise signal George claimed that it was the "... most contributed by the fact that the ampli- with an average amplitude N, there are sensitive radio made ..." and that it fiers and other active devices in the three conditions for signal detection would ".. pick up a breath of hot air ..." receiver are not perfect (these are shown. First, the signal at A is undetecta- way down in the mud. specified by the noise figure of the re- ble because it is below the noise floor While such enthusiastic endorse- ceiver). (i.e., it is buried in the noise). Second, ments are somewhat useful (especially There is also a certain elementary or signal B is barely detectable because it when made by an experienced per- basic noise contribution that will be is at the threshold of noise (i.e., it has an son), they also evade the question of present no matter what other noise is amplitude that is at or near the aver- just what "sensitive" means. In this arti- present. If the antenna input is termi- age noise amplitude). Finally, we have cle we'll provide a useful answer to that nated in a resistance that is equal to the a signal at C that is easily detectable. It's elusive question. First, though, lets look input impedance so that no external amplitude is clearly above the noise at the chief factor that limits receiver noise enters the system, and the "ideal" threshold, so the radio receiver will sensitivity. internal circuits are so perfect that they have no trouble detecting the signal contribute no additional noise signals, and producing a useable output. Noise. A radio receiver is a device that there will still be a level of noise present must examine the radio portion of the in the output. Why? Because of thermal What's Sensitivity? A radio receiver's electromagnetic spectrum to find and agitation of electrons in the resistance sensitivity is a measure of its ability to detect the desired signal. It must also of the input circuitry. In most cases, the pick up extremely small signals. More reject undesired signals, man -made input impedance of a receiver is either specifically, the sensitivity is defined as noise, and natural noise. 50, 75, or 300 ohms, and R would have the amount of signal required to The bottom -line limit to signal detect - a value equal to one of these values (as achieve a certain condition at the out- ability is noise, which consists of ran- appropriate). The elementary noise is: put. So, can we define acceptable sen- domly occurring signals of varying sitivity as the ability to pick up and P = 4KTBR power (or voltage) levels. For that 'ea- output very weak signals? No, not quite. son noise is handled statistically in radio Where Pn is the noise power (in watts) First we need to know how weak is very math. It is necessary to talk about noise at the receiver input, K is Boltzmann's weak, and how clean the output should in a root- mean -squared (rms) manner constant (1.38 x 10 -23 Joules /°K), T is the be. Both are highly dependent on the because of its randomness. To the lis- temperature in degrees Kelvin, B is the nature of the input signal (AM, FM, SSB, tener, noisé sounds like a "hissing" tone. bandwidth in hertz (Hz), and R is the etc.) and the type of output desired A good example of noise can be heard resistance in ohms. To find the noise (voice, Hi -Fi music, dots and dashes, by tuning any receiver (N FM, AM, VHF voltage, take the square root of that etc.). etc.) to a frequency that is between equation. For a 1 -MHz bandwidth, 50- Put another way, a sensitivity specifi-

www.americanradiohistory.comAmericanRadioHistory.Com cation is based on an operational defi- DETECTABLE width is too high for the received signal, nition, rather than fundamental phys- BARELY DETECTABLE then the noise present goes up, and ical principles. So sensitivity measure- sensitivity (in terms of SNR) goes down. ments are highly contextual. They UNDETECTABLE Figures 3A and 3B show two different depend on the the type of modulation scenario's in which two receivers have and the desired output quality. the same bandwidth, but vastly dif-

The nature of the signal (or type of N ferentsensitivities. Keep in mind that the modulation) will help determine the noise term is proportional to the area theoretical limits of a receiver's sen- C B A under the passband curve. Figure 3A sitivity (or "how high is up "). The desired Fig. I. Here are three signals with some has a relatively decent shaped band - output will determine what is accept- noise. Signal A is undetectable, signal B pass characteristic, with bandwidth BW able sensitivity. For a television receiver, is marginally detectable, and signal C is But, because the receiver with the minimal sensitivity should produce a easily detectable. bandwidth curve shown in Fig. 3B has a snow -free picture. For an AM or FM very poor filter that causes peaks in the broadcast receiver, good sensitivity RECEIVER passband, (definitely not desirable), it should produce a clear version of the ' PASSBAND can actually produce a lower noise fig- voice or music signal that modulated ure. Here, we have "apparent sen- the transmitter. For a radiotelephone - sitivity' at a cost of significant distortion

communicatións receiver, the tonal SIGNAL of the spectrum of the received signal; quality or fidelity is less important than it SPECTRUM not good! is for a broadcast receiver because To prevent any "creative" specifica- only a minimally acceptable clarity of tion writing that might result from taking communications is required. advantage of such situations, several Since the definition of what is "sen- different ways of determining sensitivity have sitive" depends on the type of receiver Fig. 2. An ideal match between signal become standards (or near stan- in question, how sensitivity is measured bandwidth and receiver bandwidth results dards). Each "standard" depends on depends on the receiver in question. in maximum sensitivity with little or no the signal type, the desired signal quali- There are many different methods used distortion. ty, and usually takes into account any to measure sensitivity, each suitable for additional important specifications a different form of communication, If tually not straight SNR, but rather are (like bandwidth and input impedance). the wrong method is used for a certain signal -plus -noise to noise measure- For example, in performing a SINAD receiver; it can produce misleading re- ments. A more mathematical represen- sensitivity test, one must take into ac- sults. tation would be: count the signal level, noisè level, and the output distortion. Figure 4 shows a (S + N) /N Sensitivity in Context. The sensitivity typical test set -up. The FM signal gener- should be measured with respect to but that ratio should be converted to ator must be modulated by a 1000 -Hz other important parameters such as decibels. A more sophisticated method tone to a level of 60% of the peak de- bandwidth or input impedance to used, especially in FM receivers, over- viation acceptable to the receiver have any relevant meaning. As you comes some of the limitations of that (peak deviation is typically 5 kHz on might have guessed, which param- measurement. These measurements communications receivers and 75 kHz eters are important and their actual are called SINAD measurements, which on broadcast receivers). The audio sig- values depends on the context: once stands for "signal plus noise and distor- nal source must have a very low inher- again, the signal type and the desired tion" and are the principal means for ent total harmonic distortion (THD) level. output. specifying some receiver sensitivities. The audio output of the receiver is set to Let's take an example to show the SINAD -or (S + N + D) /(N + D) converted 50% of its rated maximum power level. importance of different parameters to decibels- measurements are gen- The output voltage level is measured when measuring the sensitivity of a erally more meaningful than simple sig- under Iwo conditions In the SINAD test. communications receiver. It might have nal- plus -noise to noise measurements. First, the level is measured with switch S1 the sensitivity specified for a given sig- in the A position. This signal represents nal -to -noise ratio (or SNR). The SNR can Ways of Specifying Sensitivity. the signal, noise, and distortion cornnpo- be computed by actually dividing the Obviously, noise is clearly a factor in the nents. Next, the switch is set to B, so that power of an output signal by the power sensitivity specification of a receiver a 1000 Hz notch filter is in the signal of the noise present in it, or, more com- when measured in this fashion. How- path. This filter takes out the modulation monly, by computing it in decibels (dB) ever, the amount of noise present at the signal (S), leaving only the harmonic like this: input is directly proportional to the distortion and noise components. The bandwidth of the selective filter of the SINAD sensitivity is the number of micro- SNR = 10LOG((S + N) /N) receiver. Therefore, the bandwidth of volts that will yield an S + N + D/N + D fig- or, expressed in voltage units: the receiver must also be considered. ure of 12 dB. Typical values for 12 dB Ideally, the receiver- selectivity controls, SINAD sensitivity are stated as 0.1 µV to SNR = 20LOG((S + N) /N) which usually adjust the IF amplifier fil- 0.2 µV Typical receiver sensitivity specifica- ter, are set to the instantaneous band- Another way of specifying sensitivity is tions call for various levels of SNR (6 dB, width required to correctly receive and the "dBm method." It indicates the input 10 dB, 12 dB, or even 20 dB). demodulate the desired input signal; power required to achieve the desired Simple measures of sensitivity are ac- no more, no less (see Fig. 2). tithe band- (Continued on page 92)

www.americanradiohistory.comAmericanRadioHistory.Com BUILD THE r SOCKET SENTINEL

You don't have to put up with unsightly powerstrips

BY JOHN YACONO AND MARC SPIWAK to control multiple devices with one switch. Our device senses current flowing into one

Most people would agree that device and automatically turns on up to three others! it's a good idea to have some kind of protection on any AC outlet used to power a computer. That is plugged in, the master outlet is always Triacs. The Sentinel uses a Triac to kind of thinking probably came about hot and ready to go. An AC- powered switch power on and off, so a few words not just because computers are more device plugged into the master outlet about Triac operation are in order. (If sensitive to line fluctuations than most will function normally. A neon indicator you are already familiar with quadrant -1 appliances, but because they were next to that socket is always on to both and -III firing of Triacs, you might want to more expensive in the past as well. And identify the master outlet, and to tell you skip down to the next section.) while many computers are still quite ex- that the surge protectors are in good Triacs are multi -layered three- termi- pensive, it's very likely that most corn - condition. If the device connected to nal semiconductor devices. Their three puter owners have a video system that's the master outlet is off (i.e. draws no terminals are commonly denoted G, worth a lot more than their computer. current), the three slave outlets remain MT1, and MT2 (which stand for gate, Also, the damage done to a TV or VCR unpowered. It's only when the master main -terminal 1, and main -terminal 2, by a line surge will probably be much device is turned on that the three slave respectively), as shown in Fig. 1. Each more costly than to a PC -after all, a outlets become hot, and a second terminal has a different function. PC's power supply can be replaced for neon indicator (at the opposite corner To help you understand how they op- under $100. So, it stands to reason that of the Sentinel) turns on. That's to let you erate, take a look at Fig. 2, which is a just about any expensive electrical ap- know that the slave outlets are alive, "characteristic curve" of a Triac. Let's pliance should be protected from Fine and anything plugged into them will consider quadrant I -the upper right- surges. receive power. of the graph first. That's where the cur- As you're probably aware, you can The prototype unit has been de- rent and voltage are both positive. The buy surge -protected outlet strips for a signed to withstand only moderate cur- voltage (V) is applied between the Iwo reasonable price these days. They'll not rent levels. Our unit has been built to main terminals, and the current (I) is the only provide the protection you need, provide the master outlet with up to 1 current that flows between those termi- but they'll also give you the con- amp of current, and can provide the nals. venience of being able to turn on many slave outlets with a combined output of As you can see, if you apply voltage different things from one switch. How- 6 amps. However, those limits are not across the main terminals, they will not ever, the major problem with them is written in stone; later we'll describe conduct significant amounts of current that the master switch must be accessi- ways to increase the unit's current ca- until the voltage reaches a certain val- ble in order to turn everything on. And, pacity. Furthermore, you can add more ue called the breakdown voltage. At with several things plugged into it, it can slave and master sockets, if you wish, as that point the Triac's resistance sud- be an unsightly rat's nest of line cords. long as you don't violate the current denly drops, allowing current to flow But imagine plugging a numbe- of ratings of the components that you use freely. After breakdown, the voltage items into a surge -protected outlet pox in your unit. across the main terminals can drop to a that could be hidden from view and There are many possible uses for the low value without the Triac turning off. As being able to turn on all of them by unit. One obvious use is to have your you can see, that behavior forms a merely turning one item on using its entire computer turn on when you turn "knee- bend" in the characteristic own on /off switch. That's what the on your monitor. Or your stereo or video curve. SocketSentinel discribed in this article is system can be turned on in a similar If a voltage is applied between the designed to do. manner. It would also be neat to have gate and main -terminal 1, current flows The unit has one "master" outlet and some of your test equipment turn on through the gate. The flow of gate cur- three "slave" outlets. When the Sentinel when you turn on a shop lamp. rent causes a decrease in the value of

www.americanradiohistory.com1.411.1 AmericanRadioHistory.Com Go current, the current will flow through the PARTS LIST FOR THE diode network. Current will flow through SOCKET SENTINEL one rot o MT2 string of three diodes during positive alterations of the AC line, and SEMICONDUCTORS Fig. I. Triacs are multi -layered three - through the other set of three during TRI-6 -amp, 400 -Ply Triac (ECG56I6 terminal semiconductor Each negative alternations. devices. or equivalent; see text) terminal has a different_function. As you probably know, there is a volt- DI D6- 1N4004 1 -amp, 400 -PIV, silicon rectifier diode (see text) age drop across any diode when it's breakdown voltage needed to turn on MOV I, MOV2- V130LA120A high - forward biased. For the rectifying di- the Triac. In other words, the knee -bend power, metal -oxide varistor odes specified, that drop is around 0.8 less You volt. So when the three diodes on the becomes sharp. can increase ADDITIONAL PARTS AND MATERIALS left are forward biased, each drops 0.8 the gate current to the point where the RI- 10,000 -ohm, 1/4-watt, 5% resistor volt, giving total 2.4 knee -bend is hardly noticeable. At that FI -7 -amp fast -acting Pico II fuse a of volts across the point, it only takes a small voltage NEI, NE2- Neon power indicators with entire string of three (3 x 0.8). When the across the main terminals to turn the built -in resistors (Radio Shack string of diodes on the right is forward Triac on and the Triac can be consid- 272 -712 or equivalent) biased, it also drops a total of 2.4 volts, ered similar to a low -value resistor. That PLI- Three- conductor AC -line cord but with the opposite polarity. with plug is called "quadrant -I operation." That voltage looks very much like an Dual- outlet wall socket The same knee -bend behavior can SOI, S02- AC squarewave if viewed on an os- Heavy gauge wire, heat sink, heat-sink be seen when the polarity of the volt- cilloscope. That squarewave is sent to grease, perfboard, junction box, the gate of the Triac (TRI) and used as a age across the Triac is reversed. In that wood, screws, solder, etc. situation, applying voltage to the gate trigger signal. To summarize, if current still reduces the breakdown voltage, flows to the master socket, the diode but the gate voltage must be more opens the circuit to NEI, which then network supplies TRI with a voltage -lim- negative than main -terminal 1. As you goes out to let you know that the MOV's ited gate signal of the proper polarity. may have guessed, this is called quad- may be "unhealthy." As long as NEI is The Triac then turns on and supplies rant Ill operation. on, the MOV's should be okay, and the power to the slave sockets. Indicator To handle alternating current, the devices plugged into the Sentinel are NE2 then comes on to indicate that gate voltage must be positive with re- protected. power is available at the slave sockets. spect to MT1 when MT2 is more positive The protection circuit is designed There are brief intervals when the than MT1, and negative with respect to that way because the only way to tell if voltage across the diodes is above MT1 when MT2 is more negative than an MOV is good is to expose it to high - 2.4 volts, but below + 2.4 volts. During MT1. That is almost always accom- voltage and measure its impedance. those times, both sets of diodes don't plished by connecting some electrical But it's a good bet that a surge of over conduct. That would cause the Triac to component between MT2 and the seven amps will damage one. shut off briefly because there would be gate. That has the effect of pulling the The rest of the circuit is responsible for no gate current. Resistor R1 allows some gate voltage toward MT2, and thus monitoring current through socket S01- current to flow during those intervals so away from MT1, thereby providing the a (the master socket), and turning on that TRI can deliver uninterrupted necessary potential between the gate sockets S01 -b, S02 -a, and S02 -b (the power. and MT1. slave sockets). The sockets are labeled By the way, it is the Triac itself that limits As you'll see, our unit does just the SOI and S02, -a and -b, because they the combined output current of the opposite. A potential of the right volt- are common two- outlet type wall sock- slave outlets to 6 amps, because that's age and polarity is applied between ets. the rating of the unit used in the pro- MT1 and the gate without the as- Ignoring R1 for the moment, if a de- totype. Of course, if you use a beefier sistance of MT2. That is accomplished vice plugged into S01 -a starts to draw Triac, your slaves will be that much more though an unusual diode network. powerful. Triacs of 10, 15, 25, and 40 QUADRANTII QUADRANTI amps are available as common re- BREAK The Circuit. To do its job, the Sentinel placement parts. OFF DOWN uses some basic components in an un- STATE +1 ON -STATE To increase the current-handling ca- usual fashion (see Fig. 3). The unit is pro- pacity of the master socket or to add tected from surges by the two metal - BREAK more master sockets, use hardier di- DOWN MOV's (MOV1 odes. The current rating the oxide varistors or and VOLTAGE of diodes is should least max- MOV2). An MOV basically a compo- -V +V be at equal to the nent that appears as an open circuit imum current required by the master BREAK until the voltage across it exceeds a DOWN socket (or the total of all the sockets in a certain value. It then appears as a short VOLTAGE unit with multiple master sockets). Note circuit so that any voltage spikes large BREAK OFF -STATE that you don't have to replace R1 with a enough to cause it to short can be DOWN higher -wattage resistor because it will ± harmlessly shunted to ground. QUADRANT III QUADRANT IV never see more than 2.4 volts.

Neon indicator NEI is used to show ON -STATE You may be wondering why we didn't just use a resistor in place of the diodes. that the MOV's are okay, as you'll see in Fig. 2. This is the characteristic curve of a moment. If the MOV's ever have to u Triac without gate current. It is a plot of Well, the voltage drop across a resistor divert a surge with a current of more the voltage across the main terminals would vary with the current to S01 -a. than seven amps, fuse F1 will blow. That versus the current through them. Since too much gate voltage would

www.americanradiohistory.comAmericanRadioHistory.Com a

blow the Triac, you would have to adjust the value of the resistor to suit the device plugged into S01 -a, which would D1 D4 be qujte cumbersome. Also, if the de- F1 7A 1N4004 1144004 vice draws different amounts of current R1 D2 at different times, adjustment of the unit 10K ] D5 1N4004 ` 1N4004 would become impractical. 03 D6 1144004 - 1144004 NE2 Construction. There's not much to say G MT1 272-712 concerning the construction of the cir- TRI r cuit itself. Basically all of the parts, with ECG5616 I I 6A the exception of the neon lamps, are = MOV2 400PIV L J mounted on a piece of perfboard with V130LA120A MT2 the low -power interconnections made r- -1 S01-a I S01-b S02-a S02-b with bits of bus wire. That's with the ex- I I ception of certain component leads I I that were simply twisted together and I NEI soldered -the string of diodes, for ex- L_ _ J 272-712 ample. The connections to and from the board, as well as any other connections that carry heavy current loads Fig. 3. This circuit for the Socket Sentinel looks odd, but it works very well. The diodes voltage- limited gate signal. were made with 12 -gauge stranded provide the Triac gate with a wire. The connections to the Triac leads were first wrapped tightly around the leads and then soldered. We also provided the Triac with a heat sink, as it is common practice with such devices. The unit described here doesn't handle extreme current loads, so soldering is adequate. But keep in mind that solder will melt at relatively low tempera- tures, so the mechanical connections between leads must be strong to begin with. If you wish to power larger devices from the slave outlets, you must not only use a larger Triac, but the wiring should also be beefed up accordingly. As a matter of fact, the connections to the leads of a larger Triac might have to be twisted and secured with a wire nut. Whatever you do though, be extremely careful to avoid shorts and potential future shorts by keeping live connections well spaced. Keep in mind that you can build your This internal view of the Sentinel should give you some idea of what gauge wire goes own Socket Sentinel with as many slave where. Be sure to give the components plenty of room to prevent shorts. outlets as you like, as long as the parts you use can handle the total load. Do with a. pair of pliers (modern duplex nailed directly to a wood beam, greatly make sure that the line cord, as well as sockets have tabs that are designed to simplified the assembly of the cabinet. the outlet that you plug the entire unit be broken). The tabs for the nails were cut off, and into, can handle the total current. The neon lamps, which were pur- two holes were drilled in the bottom to You don't have to go crazy with the chased from Radio Shack (see Parts secure the circuit board with two nylon wiring for the surge -protection circuitry. List), come complete with internal cur- screws. If you use metal screws, beware It will never have to handle continuous rent- limiting resistors, panel- mounting of potential shorts. The socket assem- high- current loads, and a surge of red lenses, and pre -wired leads. Appro- blies are simply mounted directly in the seven amps will blow the fuse anyway. priately sized holes were drilled in the preformed holes in the plastic box, and The same goes for the neon lamps, as plastic outlet plate that covers the top the outlet panel is attached by screws they do not draw much current. of the unit to accommodate the lamps. to the sockets-just as it is in your wall. As mentioned before, the sockets are Remember to mount the neon bulbs As a nice finishing touch, a box was of the duplex (double, outlet) type. So, before making the electrical connec- made from white particle board to en- in order to have the master and one of tions to the rest of the circuit as the close the plastic box. That step is un- the slaves on the same assembly, the leads must go through the mounting necessary, as you can simply paint the tab that connects the two sockets hot holes. box or leave it unfinished-it can, after terminals together must be broken off A plastic outlet box, designed to be all, be hidden from view.

www.americanradiohistory.comAmericanRadioHistory.Com OWI, INC. WAO II MOBILE- ROBOT KIT CIRCLE 119 ON FREE INFORMATION CARD

Build the WAO II programmable robot for hours of mechanized fun.

Designing a project from scratch it's probably best that the soldering has and must supply a maximum current of is certainly one of best ways to already been done. The kits will make 600 mA for about 20 minutes of contin- educate yourself in the field of excellent gifts for children, although uous use. The 9 -volt battery powers the electronics. However, sometimes you some of them may be too complex for microcomputer circuitry, which requires might feel like building something just some 10- year -olds -you have to use a maximum of 5 mA yielding up to Iwo for the fun of it or to keep yourself your judgment as to whether the child weeks of continuous use; when the mi- busy-and that's where kits come in. A you have in mind will be able to assem- crocomputer is in the "sleep" mode good kit comes with everything you'll ble the kit. A schematic diagram of the (more on that later), it consumes only a need to build a project from beginning circuit is included with the kit. low 3 ji,A. to end, without having to run to the electronics store every ten minutes to WAO II's Main Features. In this The Robot Assembly. With the ex- pick up that one "last" part. hands -on report, we will review one of ception of the batteries, a ballpoint- The problem with many kits is that the the most complex kits, the WAO II Intel- pen refill, and the tools you'll need, the finished product often has a very un- ligent Robot (model MV -961) with an kit comes with everything; even a little finished look about it. You usually have MN1551KHA 4 -bit microcomputer. The tube of grease for the gears. For assem- to spend extra money for things not in- microcomputer's fundamental pro- bly you'll need long -nosed pliers, a cluded in the kit such as a project case gramming (including some built -in small hammer, and a small Phillips - to house the unit in. And, quite often, demonstration routines) is permanently head screwdriver. The front page of the there's more work involved in preparing installed in an on -board 1K x 8 ROM. assembly manual includes descriptions the case than in building the project in The WAO II can be further programmed and diagrams of all parts included in the first place. On top of that, the ap- to move as you like, and respond to the kit. The parts are neatly packaged pearance of the finished case offen inputs from Iwo obstruction sensors. The in numbered bags. That's very helpful leaves much to be desired despite all programming steps you add are stored because when an instruction calls for a of your hard work. in an on -board 96 x 4 bit RAM. particular part, it states which bag the That's where the beauty of the MOVIT Also, the WAO II can even be used as part should be in. robots from OWI kits really shines a timer; you set it for a number of min- The kit can be built in a few leisurely through. When finished, they actually utes between land 9, and it will remain hours, quicker if you're in a hurry, and look good enough to be used as a at rest until the time is up, at which time it slower if you're not. Building the kit is prop in a science -fiction movie (keep will start to rotate. much like building a radio -controlled that in mind if you enjoy making ama- A pen attachment allows the unit to car, although on a much smaller scale. teur sci -fi videos). The kits are available draw as it moves, as well as write a All of the parts are of high quality, and in different configurations, complex- random number from 1 to 6 in its "dice" they all line up perfectly. ities, and price ranges. mode. You can program the robot The first (and fifth) assembly step in- All of the robots come with as- through a keypad on the back of the volves pressing or lightly tapping some sembled and tested PC boards, which robot or by using an optional interface plastic gears onto metal shafts. Al- is good if you would rather start out with card for an Apple computer (more on though an adult shouldn't have any a known -good circuit, and bad if sol- programming later). trouble doing this, it may be difficult for dering is something you really enjoy The robot is powered from three "AA" children, at least without an adult's su- doing. However, because all of the kits batteries and one 9 -volt battery. The pervision. are recommended for ages 10 and up, three "AA" cells power the drive motors, The unit has two drive motors, and

www.americanradiohistory.comAmericanRadioHistory.Com Therefore Iwo simple gearboxes That must be assembled but, by carefully following the assembly diagrams, you shouldn't have any trouble with that. After assembling the gearboxes and checking them for smooth operation, the gears should be lubricated with the included grease. The two completed transmissions attach to the robot frame using small Phillips -head screws, as do all mechanical connections-there is no glue involved in the assembly of the WAO II. Because the unit is able to draw and write numbers, you must supply a ball- The WAO II can be programmed to check the condition of the left and /or right sensors point -pen refill. Before installation, it (with feelers shown here on the right), to determine if (and where) an object is in its path. must be cut down to about two inches. On the back of the unit (on the left here) is the control panel. That can be messy, especially if it's a full refill. The cut -down refill fits inside an The first time you try the dice demo, command button (forward, stop, turn included penholder that mounts on the do it without a pen attached, just to see right, turn left, rotate right, etc.), and en- underside of the robot. the robot go through its paces. If you tering a duration number from 1 to 9. The next step is to mount the PC want to see the robot write a number, (The robot moves forward or backward board and control panel to the robot then you'll have to attach the pen and when both motors are running in the chassis, and complete all of the wig ing. place the robot on a large sheet of same direction, and rotates when they Wiring is made easier with the pre- paper or some other flat surface that run in opposite directions.) A complete pared leads That come with the kit and you don't mind it writing on. series of motions and durations con- some very unique binding posts that At this time, it's best if you carefully stitute a program. are already soldered to the board. The read the instructions on programming For /next loops can also be included, binding posts stand vertically on the the robot. Before trying to enter your as can instructions to beep, light the board with a plastic body around them own programs, try loading and running LED, and check the condition of the left and a hole down the center. To use some of the included demonstration and /or right sensors. A run /sleep button them, all you have to do is pull the plas- programs to get a feel for the keypad serves Iwo functions: it will cause the tic body straight up, about 1/8-inch, in- and the robot's behavior. Programming robot to execute any program that has sert the tinned wire ends, and push the is done through the keypad on the been entered, or put the robot in the plastic body back down. The posts back of the robot or using an optional "sleep" mode if no program is installed make for a quick, easy, and reliable interface card for Apple computers. at the rime. The sleep mode is basically connection that is easy to undo should (The optional interface, designed for the "off" mode, as the circuit draws only you make a mistake. use with Apple II, Ile, and II Plus comput- 3 RA when sleeping. You may be confused by the fact that ers, allows you to enter commands to The WAO II is not only fun to put to- the kit includes two 9 -volt battery clips. the WAO II from the computer, edit pro- gether and play with, but it's also an Ifs nothing to worry about, one of them grams, store programs, and download excellent way for beginners to learn attaches to the 9 -volt battery, and the programs to the robot.) how programming works. But don't be other clips onto the 4.5 -volt battery The microcomputer is activated scared by the word "programming," as pack (a holder for three M cells). when you press the reset button; that it is very easy to pick up after only a Space is provided to house the bat- clears the RAM and readies the micro- short time of use. Before long, you'll be teries on the underside of the chassis. computer to accept input from the key- programming the robot to run through Once the wiring is complete, all that's pad. Programming involves pressing a obstacle courses, avoid obstacles left to do is install the body shell and when encountered, and whatever else clear -plastic dome that covers the cir- you can think of. Even people who un- cuit board, and attach the feeler sen- derstand the programming right away sors to the left and right sensor switches. will still find the WAO II very entertaining. At this point, the robot is complete and And the WAO II is not only an excellent ready to run (provided That you put the step into the world of computers, but it batteries in). will also help exercise anyone's mechanical skills. Testing and Use. The first thing you'll The WAO II is available from OWI In- want to do is to make sure that the corporated, 1160 Mahalo Place, motors will at least turn on, so the easi- Compton, CA 90220 for $109.95. The est thing to do is to run the "roulette" or Apple- interface card is $54.95. You can 1- 213 -638 -4732, or fax them "dice" demonstrations..First try the rou- These are the brains of the WAO II call OWI at lette; press reset, then run /sleep, and intelligent robot. It contains an at 1 -213- 638 -8347. For more informa- then roulette. The robot should rotate a MNI55IKHA 4 -bit microcomputer, with tion on the WAO Il robot, contact OWI x 119 on the Free Infor- random number of times and stop - on -board 1 K x 8 -bit ROM and 96 4 -bit directly, or circle but who knows where? RAM. mation Card. 67

www.americanradiohistory.comAmericanRadioHistory.Com PRODUCT TEST REPORTS

By Len Feldman A front- projection set, require a separate TV tuner page, and video page. the "Prodigy" TVP 2000 or other video input as a Most menu pages can be from Pulsar Video Systems program source, the Pulsar enlarged on- screen by (7676 Clairmont Mesa Blvd., TVP 2000 not only contains pressing a text -size button San Diego, CA 92111) pro- a TV tuner capable of re- on the remote control. vides a level of ceiving broadcast as well Pressing that button a sec- Pulsar TVP performance sure to please as cable channels, but it ond time brings the menu even the most demanding incorporates an MTS (ster- back to its normal size. The 2000 home -theater enthusiast. To eo /SAP) decoder as well. owner's manual describes the point, the large 72 -inch The audio outputs on the in detail what can be done "Prodigy" (diagonally measured), rear of the Pulsar TVP 2000 from each menu page. bright picture produced by cannot be controlled by Within the features -menu Projection TV this superb do -it -all TV the volume control, which page, for example, you can monitor /receiver can in- only affects the unit's inter- set a sleep timer. That page Receiver volve viewers in program nal speakers. However, also allows you to place a fare in a way that just can't since those speakers are label (such as the network be done even with 40- or mounted on the bottom of name or cable channel 50 -inch rear -projection sets. the cabinet, for better ster- name) along with the Furthermore, the unit takes eo effect an external stereo channel number that ap- up surprisingly little floor amplifier and speakers pears in the channel /time space when used with a should be used. display. Custom labels can properly mounted, sepa- Auxiliary components be given to four channels, rate screen with high gain, that supply baseband au- but there is also a long list dio and video can be of available labels that connected directly to the have been preset by Pulsar. Pulsar NP 2000. A digital "Parental control" or lockout comb filter is incorporated of specific channels can be so that truer color pictures done using the remote and better resolution can control while accessing the be obtained even from features-menu page. You broadcast or cable TV can store your favorite TV or sources. Operation of the CATV channels so that set is greatly simplified by when you scan channels on- screen display of main later, only those channels and sub menus. Digital you've stored will be scan- freeze frame of pictures is ned. possible, as is picture- in -pic- The audio -menu page CIRCLE 120 ON FREE INFORMATION CARD ture when more than one allows adjustment of such program source is avail- audio -related operating The Pulsar TVP 2000 "Prodigy" projection TV monitor/receiver. able. parameters as bass, treble, A channel and time dis- and balance controls, and such as the 6 -foot diago- play comes on screen selection of stereo mode. nally measured curved when the set is turned on or There's even an audio -only screen provided by Pulsar when a channel is setting that allows you to for our tests. That's es- changed. Using the menu play an auxiliary audio pecially true when the button on the remote con- component such as a ster- receiver itself is combined trol, it is even possible to eo receiver, CD player, etc. with an optional floor stand activate a full demonstra- without having the TV pic- that can double as a cof- tion of all the on- screen ture on the screen. All major fee table; the receiver can menus and what they do. adjustments can be made also be ceiling mounted. The main menu is made up from the remote control While most front -proj- of 4 menu pages: the setup with on- screen displays and ection systems we've seen page, features page, audio bar charts showing you the

www.americanradiohistory.comAmericanRadioHistory.Com TEST RESULTS -PULSAR TVP 2000 PROJECTION MONITOR /RECEIVER

SPECIFICATION PE MEASURED

Video Section Maximum usable luminance 140 Foot-Lamberts Resolution, horizontal 600 lines Convergence (center/corners) Good /good Video frequency response 7.5 MHz Interlace 50/50 Transient response Very good Black -level retention 100% Color quality Very good Overscan Excellent

Audio Section Audio output, 0 =dB reference level 0.28 V, 0.15% THD. Total harmonic distortion, 1 kHz (a -10 dB 0.09% Signal -to -noise ratio, A- weighted 66.1 dB Horizontal resolution for the TVP 2000 tested out at a superb Frequency response 20 Hz to 16 kHz 500 lines.

TV Stereo Section Signal -to -noise ratio Stereo (L /R) 58:6/58.5 dB SAP 65.5 dB Mono 58.1 dB Harmonic distortion (a 1 kHz, -20 dB (UR) 0.24/0.26% Frequency response (at - 20 -dB modulation level) Stereo (left) 41 Hz to 12.3 kHz Stereo (right) 41 Hz to 12.8 kHz SAP 250 Hz to 4 kHz Mono 38 Hz to 3.5 kHz Stereo separation (100%/- 20 -dB re 100%) Left 19.5/18.4 dB Right 18.8/19.2 dB

Additional Data Picture size 72 inches (diag.) Power requirements 185 watts Dimensions (H x W x D, inches) 93/4 x 251/2 x 241/8 Weight 55 lbs. Suggested retail price: $4295.00 When the equivalent of a fringe -area signal was input to the set'. antenna terminals, the resulting picture retained accurate color range of the adjustments as put), adjust buttons for reproduction and showed hardly any snow or noise. you go. selecting the menu displays, a menu button for mately 7 feet from the set a superb 600 lines, while CONTROLS displaying the menu or for and viewing distance was video frequency- response The front jack panel on initiating the automatic set at approximately 12 feet extended to 7.5 MHz. Inter- the Pulsar TVP 2000 lets you demonstration of all the from the screen. As is true of lace was a perfect 50/50, connect a variety of audio/ menu features, volume up any projection TV set, it was so that even at the mini- video components to the and down buttons, channel first necessary to adjust the mum recommended set. Typical components up and down buttons, and convergence of the three viewing distance we were that can be used include an on /off switch. All of those picture tubes. In this case, not troubled or distracted VCR's, camcorders, home controls are also found on red and blue tubes are by scan lines being obvious videogames, videodisc the supplied remote con- adjusted to register prop- in the image that was dis- players, stereo receivers, ex- trol, as are number buttons erly along with the fixed played. ternal speakers, etc. for direct channel access, green projection tube. This Transient response was Necessary input jacks for various buttons associated task was easily accom- very good too, with no any of these devices (in- with the picture -in- picture plished in a matter of just a bothersome white -line bor- cluding an S -video input) and flashback features, and few seconds. ders or overshoot showing are all available on the a mute control. APEL reported a max- up at transition points be- front jack -panel. Also found imum usable luminance of tween major dark and light here is a toggle switch that's TEST RESULTS 140 foot -lamberts for this borders of a scene. Another used for switching between APEL tested this projection projection TV set. That's thing that was particularly internal speakers and exter- TV set using a separate more than enough to af- noteworthy was the perfect nal audio or speakers. screen supplied by Pulsar. ford comfortable viewing in 100% black -level retention Back -panel controls in- The 6 -foot screen, mounted a normally illuminated of the set. With such an clude a video selector (S- at a slight downward angle, room. expanded picture size and video or regular video in- was positioned approxi- Horizontal resolution was (Continued on page 94)

www.americanradiohistory.comAmericanRadioHistory.Com COMPUTER BITS

By Jeff Holtzman Last time I talked about generation 16 -MHz 386, HAUPPAUGE how the old distinctions and have worked on Of the group, this 25 -MHz

between PC, XT, and AT 386SX -based laptops. Now I 386 motherboard is the have now given way to wanted to get a feel for only board that accepts DIP distinctions among 386 - higher performance levels. IC's on the motherboard, a

class machines. What used So I tested 25 -MHz 386 maximum of 4MB. (Some of The 386 to be the PC category is boards from Hauppauge the others accept SIMM's now determined by 386 Computer Works, JDR Mi- on the motherboard.) You Revolution (and 386SX) systems run - crodevices, and Mylex can also add another 4MB ning at 16 or 20 MHz, the XT Corporation; a 33 -MHz 386 via a special memory card. Continues by 25 -MHz 386 systems, and board from Jameco Elec- Without the memory card, the AT by 33 -MHz 386 sys- tronics; and a 25 -MHz 486 you gain an additional 8 -bit tems. Due to Intel's lost board from Pioneer Corn - slot. This was the only un-

monopoly on the 386, gra- puting. All five are built well cached board I tested, dations of the 486 will and speedy. consequently it was slightly quickly start overtaking the Upgrading my old 16 -MHz slower than the others.

board to the first board (the Nonetheless, I was im- 25 -MHz Hauppauge) was in pressed with its overall some ways the best experi- quality and with Haup- ence, not only for the pauge's step -by -step speed increase, but also installation.

because I had been experi- encing random system JAMECO crashes under Windows. At 33 MHz, this 386 was Even with identical pe- the second fastest board

ripherals installed, none of that I tested. The board itself

the motherboards I tested accepts no memory; all exhibited any of those memory is mounted on a

problems. Overall, I found separate expansion card running Windows with the that reduces the total Pioneer board and eight number of slots to seven. megabytes of RAM most Depending on whether you enjoyable. use 256K or 1MB SIMM's, the This 25 -MHz 486 motherboard from Pioneer Computing can The in- will run with 1, 2, 4, 8, accommodate up to 32MB of SIMM memory in curious test hardware board combinations (256K. IMB, and 4MB) without using u slot. cluded several types of or 16MB. Interleaving func-

video adapters, SCSI hard - tions only at 2, 8, or 16MB. I 386. Already, you can buy disk interface, LANtastic net- found 8MB quite comfort- basic 486 systems for about work- interface card, and able for running multiple $ 2000. miscellaneous I/O cards (se- applications simultaneously This new world of PC rial, parallel, modem). My under Windows. The price power enjoys greater com- primary working environ- of the board includes the patibility across the range ment was Windows 3.0 required memory card. of performance than did running Word for Windows Other than speed, this the old PC/XT /AT division. All 1,1, MS Project 1.0, Excel 3.0, board is virtually identical to systems based on the Corel Draw 1.21B, CrossTalk the JDR board. In addition 386SX, 386DX, and 486 offer for Windows 1,1, and nu- to "generic" documenta-

identical memory and task merous small utilities. I tion, the board came with a management abilities. For experienced no hardware specially written installation example, Windows will run or software anomalies or guide. A 25 -MHz version is in 386 enhanced mode incompatibilities. also available. identically on a 16 -MHz Now for a quick run- 386SX laptop and on a 33- down on each board, in JDR MHz 486 monster. Of course alphabetical order by man- See my comments on the the 486 will run somewhat ufacturer. Each board's Jameco board. Faster over- faster. features are summarized in all than the Hauppauge,

I had been running a first- Table 1. but slower than the Mylex

www.americanradiohistory.comAmericanRadioHistory.Com you can fill memory to 1, 2, TABLE 1- FEATURE SUMMARY 4, 5, 8, 16, or 32 megabytes. Feature Hauppauge Jameco JDR Mylex Pioneer Physically, the SIMM socket latches are flimsy and Model No. ATCL25 -04 JE3533 MCT- C386 -25 MWS386 -25 Vantage 486/25 prone to break. The 486 CPU contains its own built -in CPU Type 386 386 386 386 486 8K cache; you can supple- BIOS Award AMI AMI Phoenix AMI ment that with 0, 128K, or BIOS shadow Yes Yes Yes No Yes 256K of external cache RAM. The AMI BIOS is more Speed 25 MHZ 33 MHZ 25 MHz 25 MHz 25 MHz versatile than some, allow- Max. on- 4 MB 16 MB *" 16 MB* 8 MB" 32 MB ing you to shadow the main board RAM or video BIOS, or both, or Type of RAM DIP SIMM DIP or SIMM SIM SIMM neither. Its documentation is Wait States 01 0/1 0-3 excellent. A 33 -MHz version

Memory Speed 70 ns 60 or 70 ns 80 ns 80 ns 80 ns is also available.

Memory Interleave Interleave Interleave Interleave Interleave Architecture CONCLUSION My favorite board is the Size Mini -AT Mini -AT Mini -AT AT Mini -AT Pioneer. Its overall speed Math 387 387 or Weitek 387 or Weitek 387 or Weitek Built in 486, was simply outrageous, and Coprocessor 3167 3167 Weitek 4167 3167 its versatile memory- expan- Cache OK 32K 32K 64K 0-256K sion scheme helps ensure it System Logic C & T C & T C & T C & T Opti that will grow with you. The Jameco and JDR Expansion Slots 6 16 -bit, 1 8 -bit, 4 16 -bit, 3 8 -bit, 4 16 -bit, 3 8 -bit, 6 16 -bit, 1 8 -bit, 8 16 -bit boards are off -shore clones, 1 memory 1 memory 1 memory 1 memory and in several months of Warranty 1 year 1 year 1 year 1 year 2 years testing performed flawlessly. On expansion board (not included) They are easy to get hold Optional Expansion board allows additional 8 MB (Continued on page 88) On expansion board (included) that we'll review next. The out of harm's way. (Some memory card is an extra - boards have SIMM sockets LEN cost option. The board in- opposite the expansion cluded only the "generic" connectors and can inter- documentation. A 33 -MHz fere with expansion boards.) ti version is available. In various combinations of VCR 256K, 1MB, and 4MB SIMM's, REPAIR TECHNIQUES MYLEX This board contains a 64K VENDORS cache, twice as much as the JDR board, hence it was slightly faster. It holds 1, Jameco Electronics 1355 Shoreway Road 2, 4, or 8MB right on the Belmont, CA 94002 motherboard, and has 415- 592 -8097 provision for a separate Microdevices to JDR card expand all the way 2233 Branham Lane to 16MB. Documentation is San Jose, CA 95124 skimpy, is 800- 538 but overall quality -5000 Now, in a complete multimedia package excellent. 408 -559 -1200 consisting of a200-page training manual and Hauppauge Computer Works, Inc. a 1 -hour 22- minute video training tape, you can learn secrets of Advanced VCR Repair. PIONEER 91 Cabot Court (Also includes Color Bar Test Tape.) Hauppauge, NY 11788 -3706 This 25 MHz 486 speed Includes many examples of VCR make/model 516- 434 -1600 demon is roughly twice as specific troubleshooting tips ...Learn how to most "tough" VCR malfunc- fast as the 33 -MHz Jameco, My lex Corporation quickly isolate 47650 Westinghouse Drive tions, whether electrical or mechanical. and it has lots of other nice Fremont, CA 94539 Complete coverage of Theory of Operation features. First, you can 800- 446 -9539 - Read manual, view 1 -hour 22- minute mount as much as 32MB of 415 -683 -4600 videoI FREE INFORMATION PACKAGE! SIMM memory directly on Pioneer Computer Inc. the board without using a 49066 Milmont Drive CaII 1/800 -537 -0589 slot. In addition, the SIMM's Fremont, CA 94538 Viejo Publications, Inc. 415- 623 -0808 5329 Fountain Ave., Dept. PEA are located behind the Los Angeles, CA 90029 keyboard connector, well CIRCLE 16 ON FREE INFORMATION CARD 71

www.americanradiohistory.comAmericanRadioHistory.Com ANTIQUE RADIO

By Marc Ellis he May, June, and July COSMETIC INSPECTION instrument. The Model 106 issues of this column Tony's theremin and its consists of a hefty dynamic featured a bibliography of accompanying speaker speaker housed in a deco- theremin articles, a history have been reposing in my rative floor cabinet that has

of the theremin in this coun- basement since I acquired elaborate turned legs and try and a discussion of the them over a year ago. tapestry grille cloths. The

The instrument's operating theo- Since I wanted to take 106 speaker isn't as rare a ry. Last month, we some "before" pictures be- piece as the theremin, Theremin: A temporarily interrupted our fore dismantling the units since it was widely sold as theremin story for a long - for inspection, my first of- an optional accessory for First Look overdue look into the mail- ficial act was to dust off RCA 1929 -era radios such bag. But now we're back to both pieces and bring as the Model 60.

Inside our exploration of that fas- them upstairs where I would In good condition, the cinating granddaddy of all have room to do the pho- 106 is quite a handsome electronic musical instru- tography. unit. But the one that came

ments. I don't usually invade the with the theremin has defi- In this issue, we're going upstairs with my projects, so nitely seen better days. The

to begin work on an actual I prudently accomplished finish is badly scuffed and theremin -the one, in fact, that task while my wife was scratched, the power and that was responsible for all on an errand. She was a audio cords are frayed and pretty good sport when she patched, the grille cloth for came home to find the the rear panel (luckily, not furniture shoved aside to tapestry) is hanging in make room for an odd - shreds, and the bottom of looking pair of artifacts. She one leg is missing-proba- even agreed to pose with bly knocked off in a fall. the instruments to give the Fortunately, the tapestry picture a little scale. Need- front and side pieces are less to say, though, the reasonably intact, if a little normal furniture arrange- faded. ment was restored very Though a bit more of a quickly after completion of restoration challenge than

the photography! the theremin cabinet, I Considering that the have no doubt that the theremin had been used Model 106 could be made during the last several years quite presentable. A good of its active life at a high dry cleaning might work school, and obviously wonders with the tapestry hadn't exactly been treated pieces, and a clever wood- with tender loving care by worker might be able to the student stagehands turn a replacement for the The theremin and its model 106 speaker pose for a "before" who moved it around, the missing leg on a small picture in our living room. cabinet is in surprisingly lathe. The rest is simple good shape. Although wood refinishing. of the earlier articles on there are a couple of nas- that fascinating device. The ty- looking gouges and INSIDE THE CABINETS instrument came into my some loosened leg joints, Removing the speaker

possession courtesy of it's basically quite sound cabinet's back panel, I was reader Tony du Bourg of and should be fairly easy to pleasantly surprised by

Summit, NJ. Tony wanted to restore to decent ap- what I saw. The speaker encourage the develop- pearance. itself looked quite good

ment of a series of Antique The speaker system that and, as I later confirmed by Radio columns devoted to came with the theremin is removing the speaker from the theremin, and that is an RCA Model 106, which is the enclosure, the cone exactly what he has ac- the type recommended by seemed to be in perfect complished! RCA for best results with the shape.

www.americanradiohistory.comAmericanRadioHistory.Com ,r.

ply. The model 106, rectifiers of later years and however, is a free- standing the silicon rectifiers that are speaker designed to be a in use today.) radio accessory. So the 106 Placing a DC voltmeter has its own built -in field sup - across the field coil to ply. monitor the performance of

The field supply circuit is the rectifier, I plugged in the made up of Iwo copper - Model 106's AC power cord oxide rectifier elements, and gingerly flipped on the

each the equivalent of two power switch. I was ready to diode rectifiers, mounted cut the power at the on opposite sides of the slightest sign of smoke or speaker frame. The four abnormally low field volt- The theremin chassis (left) and its power supply as removed from rectifiers are wired in a age. However, the meter the cabinet for testing. bridge circuit that converts immediately registered 69 volts DC, and there was no Access to the theremin smoke or burning smell that cabinet is gained by swing- I could detect. ing open a pair of doors at Though the reading was the back. The space inside well over 10% lower than is divided by a slide -out the 80 volts called for in the wooden shelf holding the RCA specifications, the theremin chassis and coils. speaker wasn't humming The heavy power supply, too badly and it looked like which is the same basic the rectifier wasn't going to model used in RCA AC- fail. I decided to leave the operated broadcast re- power on for a while to see ceivers of the period, is if things would improve. My mounted under the shelf on patience was rewarded - the cabinet floor. just before I shut the speak- Physically, all of the there - er off about an hour later, min and power -supply the voltage had risen to 79 components appeared to and the hum had dropped be intact and in good con - to a very low level. dition-except for one It'll be interesting to see trouble spot. A small coil how the rectifiers perform The test lamp, in holder, is clipped to the terminals of the pickup wound over the bottom of the next time I turn on the one of the iwo large reso- loop for volume -control tube filament voltage. speaker, but indications are nance coils mounted at the that the unit is still going to back of the theremin shelf POWERING UP THE be capable of making it on was in disarray. Its turns SPEAKER the old copper -oxide were loose and jumbled - Up to this point, I hadn't stacks. If not, of course, I'll and closer inspection re- applied power to any of always have the option of vealed that they had been the theremin components. switching to modern semi- wound over several layers Powering up long- disused conductor rectifiers. of what looked like modern electronic equipment is a By the way, if you have an electrical tape. chancy business and, ac- RCA 106 (or similar) speaker Consultation of RCA's ser- cording to Tony, this whose rectifier stacks do vice notes for the theremin theremin hadn't been used need replacing, I'd recom- revealed that this coil is the since the 1950's. But I'd mend the short article Hum The model 106 speaker was pickup loop for the filament taken the visual inspection in Your Radiola 41 or Similar removed from its cabinet to supply of the type -20 vol- as far as I could, and it was check its cone. Note the two RCA? in the February, 1991 ume- control tube. (For "smoke test" time. I decided cylindrical copper -oxide Old Timer's Bulletin (the of- more information on the to begin with the loud- rectifier stacks. ficial journal of the Antique volume -control circuit, speaker. Wireless Association). In a please refer to the July, 1991 Like all dynamic speak- few well -chosen para- issue, which discusses the ers, the model 106 requires the 117 -volt AC line voltage graphs, author Bob operating principles of the a source of DC voltage to into the 80 volts of direct Haworth explains how to theremin in some detail.) energize its field magnet. current needed to power change over to modern Apparently the coil had be- Most dynamic speakers that the field. (The copper oxide rectifiers while maintaining come loose at some time in we come across are built rectifier is a primitive semi- the original appearance of the past, which made it the into specific radios and re- conductor power rectifier the speaker as closely as subject of that not-too -con- ceive their field voltage that is functionally equiv- possible. vincing fix. from that radio's power sup- alent to the selenium (Continued on page 94)

www.americanradiohistory.comAmericanRadioHistory.Com CIRCUIT CIRCUS

By Charles D. Rakes his time around, we'd Il like to share with you a PARTS LIST FOR THE number of unrelated cir- PRESSURE DETECTOR cuits that can be fun to SEMICONDUCTORS build and may prove useful UI- LM1458 dual op -amp, integrated circuit in project. some upcoming QI- 2N3904 general- purpose NPN silicon transistor Detector In any case, drag out the DI. D2 -1N914 general- purpose small -signal silicon diode junkbox, heat up the iron, and get ready for some RESISTORS Circuits, And All resistors are 1/4-watt, 5'4 units.) circuit fun. RI. R2- 10,000 -ohm More R3, R4- 100,000 -ohm PRESSURE DETECTOR R5- 220,000 -ohm Our first entry, see Fig. 1, R6 4700 -ohm uses a piezo transducer as CAPACITORS a sensor in a circuit that 01-0.1 -µft ceramic -disc in air responds to changes C2. C3- 0.47 -µF ceramic -disc pressure. A piezo transducer ClS 0.27 -11F, ceramic -disc is mounted in one end of a CS- 10 -p,F, I6 -WVDC, electrolytic plastic tube facing out to- C6 47 -11F, I6 -WVDC, electrolytic ward the open end. By C7- 470 -11F I6 -WVDC, electrolytic blowing into the tube ADDITIONAL PARTS AND MATERIALS opening, the pressure in- BZI- Piezoelectric buzzer (without internal oscillator) creases, causing the piezo BZ2-Piezoelectric buzzer (with internal oscillator) Pertboard materials, enclosure, plastic tube, IC socket, 9 -volt +9v power source, wire. solder, hardware. etc.

lc7 C2 C3 470 .47 .47 1 1 dual op-amp, UI -a, is con- VCO is R4 R5 figured as a low- frequency, The circuit in Fig. 2 a 100K 220K which is simple, voltage -controlled W. high -gain amplifier, used to boost the trans- oscillator that can be con- C6 8 47 ducer's output. nected to the output of the OZI" U1 -a I( - in Fig. 1. A single 1'2 A second high -gain, low circuit 4 LM1450 frequency amplifier, formed 4093BE quad 2 -input NAND around U1 -b, increases the Schmitt trigger is con- W LM1458 1N914 Cl R3 output of U1 -a to several nected in a simple RC .1 100K volts, with the exact output audio -oscillator circuit. An R1 R2 R6 4.7K C4 10K1 10K depending on the air -pres- MPF102 FET operates like a .27 sure variations at the voltage -variable resistor, +9v - Q1 transducer. Diodes D1 and shifting the oscillator's fre- 2N3904 BZ2 "SEE TEXT D2, and capacitors C4 and quency as its gate voltage C5, convert the amplifier's is varied. Without a DC in- +9v output to a DC pulse that's put, the oscillator's Fig. I. In this circuit, a piezo transducer (BZ /) is used as an air - used to turn Q1 on, thereby feedback path is open, due pressure sensor. The circuit responds to changes in air pressure causing piezo buzzer BZ2 to to the near -infinite resis- by sounding a buzzer (BZ2). sound for each change in tance between the FET's air pressure. drain and source, so no element to bend slightly, The pulsed DC output, at output tone is produced. producing a small output the cathode of D2, can As the FET's gate voltage signal. also be used to drive a rises, the drain -to- source re- A 0.1 -µF capacitor, Cl, is voltage -controlled os- sistance decreases connected across the piezo cillator. Such a circuit could sufficiently to start the os- element to help filter out be made into an electronic cillator. The oscillator starts high- frequency sounds and whistle to produce a vary- out with a very low frequen- allows only very low fre- ing output tone in relation cy tone that increases in quency, air -pressure signals to the air pressure applied pitch as the input voltage to pass. Half an LM1458 to the transducer. rises. The third gate drives a

www.americanradiohistory.comAmericanRadioHistory.Com piezo buzzer, which proof L1 and D1, a germanium duces a low -level tone diode. The diode converts output. the sampled RF to a DC The oscillator's frequency signal that's fed to the range can be changed by negative input of U1 -a. A increasing the value of C1 50 -µA meter is used to indi- for a lower- frequency cate the approximate range or by decreasing the strength of the RF signal. value for a higher- frequen- The circuit is powered from cy range. To connect the a standard 9 -volt transistor pressure- sensor circuit to battery. the VCO, just remove 621, R6, and BZ2 from the circuit CURRENT SENSOR Fig. 3. This circuit uses half of an LM /458 dual op -amp to form in Fig. 1, and connect a The circuit in Fig. 4, built a sensitive wide-range RF detector that's capable uncovering RF wire from the junction of D2 around a single 2N3904 signals in the milliwatt region. and C4 to R3 in Fig. 2. Also general- purpose silicon connect the two ground transistor configured as an PARTS LIST FOR THE circuits together. RF oscillator, can be used RF DETECTOR as a DC current sensor. In- RF DETECTOR ductor L1 is -which RESISTORS Our next circuit, see Fig. 3, in connected the oscillator's (All fixed resistors are 1/4-watt, 5% units.) uses half of an LM1458 dual tank circuit-is a hand - RI, R2 -1000 -ohm op -amp in a sensitive, wide wound coil consisting of 36 R3-2200 -ohm frequency range, RF- detec- turns of #26 enamel -cov- R4-I -megohm tor circuit. The circuit can ered copper wire wound ADDITIONAL PARTS AND MATERIALS detect milliwatt levels of RF - evenly spaced on a donut UI- LM1458 dual op -amp, integrated circuit energy from below the shaped Amidon (Amidon DI -IN34 germanium diode standard broadcast band Associates, Inc., PO Box 965, CI, C2-- 0.I -p,F, ceramic -disc capacitor to frequencies beyond the Torrance, CA 90508; Tel. C3- 680 -pF ceramic -disc capacitor FM broadcast band. 818- 760 -4429) FT50 -43 fer- L1 -2 -mH choke A small pull -up antenna rite core. The sense wire SI -SPST switch (ANTI) collects the RF signal (designated L2) is simply a BI -9 -volt transistor -radio battery and sends it to a broad- length of number 16 insu- MI-50 -mA meter ANTI -Small telescoping antenna band RF detector made up lated copper wire looped Perfboard materials, enclosure. IC socket, wire, solder, hardware. etc. 1

through the center of L1's increase by about 1 kHz; core. When power is ap- and when the current is plied to the circuit, it begins increased to 100 mA, the to oscillate at a fixed fre- frequency will increase by quency of about 180 kHz. about 2.5 kHz. With 1 amp The application of DC of current, the frequency D power causes current to will increase to about 238 al flow through L2, changing kHz. A potentiometer can MPF102 IN _ the core's permeability, be substituted for R3, allow- Fig. 2. Here a 4093BE quad 2 -input NANO Schmitt trigger 's which, in turn, causes the ing the current though the configured as a simple voltage- controlled audio oscillator. The oscillator's frequency to sense loop to be varied, MPFIO2 FET (QI) operates like a voltage- variable resistor. shift. Resistor R3, a 20 -ohm, and by extension, the oper- shifting the oscillator's frequency as its gale voltage is varied. 25 -watt unit, limits current in ating frequency of the the sensing circuit, thereby oscillator. protecting the power sup- PARTS LIST FOR THE VCO ply and keeping L2 from CURRENT SENSOR acting like a shorted turn in MODIFICATION 4093BE quad 2 NANO U1- -input Schmitt nigger, integrated the oscillator's tank circuit. A By using the coil /potenti- circuit frequency counter can be ometer combination shown Ql- MPFI02 N- channel FET connected as shown to in Fig. 5, the current sensing RI. R2 -100K 1/4-watt, 5% resistor monitor the oscillator's fre- circuit can be made to R3- I-megohm, %J -watt, 5c/ resisto- shift. CI- .02 -1.4F ceramic -disc capacitor quency respond linearly to relatively C2-47 -µF. 16 -WVDC, electrolytic capacitor The circuit will respond to low levels of current, rang- BZI- Piezoelectric buzzer (without internal oscillator) currents from as.low as a ing from 1 to 50 mA, at a Perfboard materials, enclosure. IC socket, 9 -volt power source, few milliamps to over 1 rate of about 100- Hz -per- wire. solder, hardware, etc. amp. With a current flow of milliamp. The 33 -mH choke 50 mA, the frequency will (L3) completely removes

www.americanradiohistory.comAmericanRadioHistory.Com PROBES S1 N.O.

DC I POWER SUPPLY

LEDI

V B1 + +9V LED2 ".(0/ 177 w. W LED3 R3 2052 16 ilP% `SEE TEXT I 25 WATT W LED4 Fig. 4. Here a single transistor, configured as an RF oscillator, is 15 j^ used to detect changes in current flow. LED5 01 U1 2N3904 5 LM3914 14 / 1W LED6

PARTS LIST FOR THE 13 /irk R2 /NV LED7 CURRENT SENSOR 1K

R5 12%/1 RESISTORS Cl 1.5K WP LEDB (All resistors are 1/4-watt, 5% units, unless otherwise noted.) .1 RI -1000 -ohm 11 A(Aph R2- 220,000 -ohm LED9 R3-20 -ohm, 25 -watt, see text 9 10I, R3 A LED10 CAPACITORS 1K Cl, C2- .003 -11..F, ceramic -disc C3- .01 -p.F, ceramic -disc C4 0.1 -11F, ceramic -disc R4 50K ADDITIONAL PARTS AND MATERIALS Q1- 2N3904 general -purpose NPN silicon transistor Fig. 6. The moisture detector is built around a 2N3904 general - LI -See text purpose NPN transistor (configured as an emitter Mower), an L2-See text LM3914 dot /bar display driver, and a few support components. Perfboard materials, enclosure, DC supply, frequency counter, Amidon FT50 -43 ferrite toroidal core (see text), wire, solder, hardware, etc. PARTS LIST FOR THE MOISTURE MONITOR

TO OSCILLATOR SEMICONDUCTORS LM3914 R1 L3 IN FIG.4 Ul- dot/bar-display driver, integrated circuit 1K 33mH Q1- 2N3904 general- purpose NPN silicon transistor 2 WATT LEDI LEDI() -Jumbo light- emitting diode (any color) +9V SNA. A RESISTORS (All fixed resistors are 1/4-watt, 5% units.) RI- 10,000-ohm "SEETEXT R2, R3 -1000 -ohm 1 R4- 50,000 -ohm, potentiometer R5-1 500 -ohm in 4 Fig. 5. The current sensing circuit Fig. can be modified ADDITIONAL PARTS AND MATERIALS (through the coil /potentiometer combination shown here) to CI 0.1 -11F, ceramic -disc capacitor respond linearly to relatively small current changes; the BI -9-volt transistor-radio battery frequency of oscillation will shift at a rate of about 100 Hz per SI- Normally -open pushbutton switch milliamp. Perfboard materials, enclosure, 18 -pin IC socket, probe material (see text), 9 -volt battery connector, wire, solder, hardware, etc.

PARTS LIST FOR THE CURRENT-SENSOR MODIFICATIONS the shorted turn effect of changes. Adding turns to L2 the current sensor. The five will increase sensitivity and RI -1000 -ohm, 2 -watt potentiometer turns used in Fig. 5 for L2 reducing the number of LI -turns #26 copper wire, see text -S increases the circuit's sen- turns will reduce the sen- L2 -36 -turns #26 copper wire, see text sitivity. The number turns sitivity. L3 -33 -mH choke (Mouser, part 43LH333) of Perfboard materials, enclosure, 9 -volt power source, wire, solder, on L2 may be varied to The oscillator's frequency hardware, etc. increase or decrease the range may also be circuit's sensitivity to current (Continued on page 88)

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By Fred Blechman ife is full of coinci- from Electronic Arts. I liked are nearby you can fly right dences, but some are the original version, the Ad- through them. really weird. Although it was vanced Flight Trainer, but it When you destroy a

published six years ago, I was produced several years plane, bit -mapped graphic only started reading Gener- ago and would not be up explosions are very realistic. al Chuck Yeager's book to today's standards of I even saw the pilot bail out Flying With Yeager a few days ago. My high -resolution graphics, of a plane I hit just before it wife spotted the paper- smoothly animated screens, exploded. And you can The Best back version at a used and VGA color. That was bail -out, too. When you do, book store and got it for me followed a couple of years you watch the ground because of my revival of ago with the Advanced come up as you descend. interest in flying in the last Flight Trainer 2.0. Although A bail -out at 20,000 feet few years. The coincidence this was an improvement can bring you down

is that just yesterday I re- over the original in some through some clouds.

ceived an advanced respects, overall I liked the Seventeen types of review copy of Chuck original version better. planes and fifty pre-de- Yeager's Air Combat from Now along comes Chuck fined missions reflect the this Electronic Arts. I dropped Yeager's Air Combat, and fact that program other assignments to get this is a real winner! Al- covers three wars -World II, this to you right away. though the version I War Korea, and Vietnam. Among the most popular received was pre- publica- Not only that, you can games for decades (cen- tion, and in place of the create your own missions,

turies?) are Checkers, manual I only received a flying any of 6 aircraft

Backgammon, Gin Rummy, few typed sheets, I fell in against up to 15 "enemies" and Cribbage. What better love with this program. I'm in 17 different types of now at the end on my third planes, and the enemies

day of "flying" and I keep can be amateur, mediocre, discovering new missions good, or excellent pilots! Is and new effects. that enough choices for

I suppose what makes you? this one of the very best The flight control is so flight simulators I've tested is good that this is the first

the realism. The flight -con- simulator I've found where I trol response, the smooth could actually fly formation

animation, and the many on nearby planes. I got a options are all right up real kick out of flying there with the best. In fact, around and among forma- you can even "blackout" in tions of bombers in my own high -G maneuvers (the created scenarios. Match- screen goes gray or black, ing speed, heading, and the number altitude is a real challenge. Take flight with Chuck Yeager's Air Combat, a flight- simulator/ depending on air -combat game that offers unsurpassed realism. of G's and how long they One of the many outside - are sustained), a neat the- cockpit views allows

name for a package with effect I haven't seen before. you to fly behind your own computerized versions of Although it may seem like aircraft, matching each those games than The a small thing, the delinea- maneuver as the real hori- Games People Play? Fea- tion between the green zon responds just as it does turing high -resolution ground and the light blue in actual flight. graphics and lots of op- sky is particularly effective. I flew Chuck Yeager's Air tions, we'll take a look at this Instead of just changing Combat with a 12 -MHz group of programs a little from one color to the other, 80286 machine using a later on. the actual horizon is white hard drive, VGA graphics, (like clouds in the distance) and an Adlib sound board. CHUCK YEAGER'S AIR fading to cyan and then The screen updates are so COMBAT light blue. This makes the rapid that the action ap- This is the third Chuck horizon unmistakable. Inci- pears almost movie -like. Yeager's flight simulator dentally, when those clouds Although the graphics are

80 www.americanradiohistory.comAmericanRadioHistory.Com not the highest resolution (Electronic Arts, 1820 Backgammon and put it in its demo mode and I've seen (probably to pro- Gateway Drive, San Mateo, Checkers use a pull -down watched. I've never played vide fast action), they are C4 94404, Tel. 800 -245- menu interface with di- Cribbage and didn't want colorful and detailed. B -17's, 4525. Requires IBM PC or alogue boxes, similar to a to take the time to learn. B -29's, and B -52's look like compatible, 640K RAM, DOS Windows approach. They You can play Two -Handed, they should when you get 21 or higher, hard drive or offer context sensitive help, Four -Handed, or Five -Card close enough, as do all the high -density floppy drive, easily moved pieces, and Cribbage with seven other aircraft. EGA or VGA graphics. AdLib multiple levels of play. Gin unique computer oppo- This is strictly an air-corn- and Sound Blaster sound IGng and Cribbage IGng use nents. It sure looked (and bat simulator. While there boards supported. PC/AT or the F1 key to pop -up a sounded) good as cards are many buildings, roads, above recommended. Sug- Main Menu, with some were dealt and pegs rivers, and bridges in the gested retail price is choices leading to sub - moved along the board.

scenery, your missions in- $59.95) menus. I preferred the pull - I'm sure the 82 -page Crib- volve air combat. You can, CIRCLE 130 ON FREE down menus and dialogue bage IGng Users Manual INFORMATION CARD however, practice takeoffs boxes. would answer any questions

and landings with six dif- I played Backgammon I'd have.

ferent planes: North THE GAMES PEOPLE first, since I used to love Perhaps most significant American P -51D Mustang or PLAY playing a variant of that is that, although an excel- F -86E Sabre, Focke -Wulf The Software Toolworks, game, called Acey Deucey. lent manual is provided for

FW- 190A -8, Mikoyan- publishers of the award - This and two other variants each game, I successfully Gurevich MiG -15 or winning Chessmaster of the traditional Backgam- played all but Cribbage M!G -21ME and the McDon- 2000/2100 and Mavis mon (Dutch and Plakoto) without even looking at the

nell Douglas F4 -E Phantom Bacon Teaches Typing, can be played. manuals! I have to say I was Il. Quite an assortment! have put four popular Also, in addition to the very impressed with all A pull -down menu system games-Gin Rummy, Crib- traditional board design, these games. They looked uses 6 headings with a total bage, Checkers, and four other "far out" board great and they played

of 49 choices, giving you an Backgammon -into a sin- designs are available. great. I could easily spend idea of the flexibility of Air gle package that costs Many other features are in- many hours investigating Combat. A VCR mode lets what you might expect to cluded, like hints, switching the variations of each. you record and play back pay for only one. sides with the computer, (The Software Toolworks, missions for further study. Installation allows you to taking back a move, and 60 Leveroni Court, Novato, Various sounds (engine, put each game onto one more. CA 94949, TeL 800 -231- background, stalls, etc.) can or more floppy disks (a total Each of the game pieces 3088. Requires IBM PC, JCL be enabled or disabled. of five 360K diskettes for all has a 3- dimensional ap- AT, PS/2 or Tandy PC com- The sound with my AdLib programs, taking a half- pearance, and is patibles, except Tandy board was great. You can hour or more.) Or, you can "dragged" quickly and 2000; DOS 2.0 or later; 512K use a joystick, mouse, or put them all on a hard easily with a mouse. Using RAM; CGA, EGA, or VGA keyboard for flight control. I drive in less than ten min- any printer, you can print color graphics. Mouse op- much preferred a joystick, utes if you have about out the board and piece tional. Suggested retail and found CH Product's 1.4MB of free space. locations anytime. price is $39.95.) CIRCLE 131 ON FREE FlightStick the most natural I ran all these games on I played Checkers next- INFORMATION CARD of the three joysticks I tried. a 12 -MHz AT with a hard and lost every time! You All kinds of views, with drive, color VGA, and a can have the computer as zoom, are offered, and you mouse, and had no installa- an opponent, or two hu- NEW FUN SOFTWARE can test planes by starting tion or operational mans can play, or you can Here are some recently on the runway, on final problems. I also tried have the computer play announced programs you landing approach, at Checkers and Backgam- against itself in a kind of can order from your regular 10,000 feet, or at 40,000 mon on a 4.7 -MHz XT with demo mode. Two- or three - software supplier. Versions feet. The best option I found CGA and no mouse. The dimensional graphics are and suggested retail prices, was "Invincible;" until then I color was sad compared to available, and a printout of where announced, are was getting shot down in a VGA, the keyboard use was piece locations on the shown in parentheses. matter of minutes every clumsy at best, and it took board is available anytime. Electronic Arts Affiliates: time! Backgammon forever to Gin King lets you play Strategic Simulations has re- Although the pre-release load. My suggestion is that Standard Gin or Oklahoma leased the IBM version of version I tested didn't have you use The Games People Gin against any of seven Death Knights of Krynn, the all the final features (such Play on a machine with computer "people," each sequel to the popular Ad- as a digitized version of EGA or VGA, a hard drive, with his or her own unique vanced Dungeons and Yeager's voice instead of and a mouse. Non -intrusive playing style. Also, any of Dragons (IBM, Amiga: screen messages), I was sound is used in all the the computer people can $49.95; C64/128: $39.95) mighty impressed with the games, and can be turned be your personal tutor. Play and Eye of the Beholder, program as it is. Now all I off. The regular speaker is is very fast, the cards look the first in The Legend Se- have to do is try to keep used, and special sound very real, and there is even ries of Advanced Dungeons away from it so I can get boards are not supported a demo mode. and Dragons fantasy role - some other work done. or needed. As for Cribbage IGng, I just (Continued on page 94)

www.americanradiohistory.comAmericanRadioHistory.Com SCANNER SCENE

By Marc Saxon We are fast approach- them to receive the NOM Another good entry is the ing that time of year frequencies. Oddly, al- Weather Max, which com- when we have come to though the frequencies can bines the 162 -MHz NOAA expect the unwanted -vio- be picked up on all VHF receiving capability with a lent hurricanes, for instance. scanners, none seem to be tunable FM- broadcast re- Preparing for And don't forget that the made with a switch that ceiver. This set also has the 1989 earthquake in the San enables the operator to built -in NOM alerting Stormy Francisco Bay area turned jump right to the local alarm. Weather Max oper- up in early October. Those channel. The best way of ates from house current, Weather events should remind you establishing that capability from a vehicle's cigarette that a VHF radio is a handy is to program your local lighter, or from internal bat- thing to have for your fam- NOM channel into memo- teries. The telescoping ily's safety. ry Channel 1 on your antenna offers a 50 -mile NOAA (National Oceanic scanner (which is most likely receiving range, and there's and Atmospheric Admin- to be where the Priority a jack for connecting an istration) VHF broadcasts feature functions). Then, external antenna for ex- can be heard in virtually all lock out Channel 1 so that tended base range, or a populated areas of the your scanner won't hang up mobile antenna. there during its regular More information on scanning process. When Weather Max (Model you want to hear the NOM 74 -105) is available from transmission, simply touch Midland International the Priority button on the Corp., Consumer Commu- scanner, and the NOAA nications Division, 1690 N. broadcast will immediately Topping, Kansas City, MO kick into action on your set. 64120. The Radio Shack When you want to resume units are all on display at rN./ normal scanning, touch the the chain's 7,000 retail out- Priority button again to turn lets, or may be ordered by off that function. mail through their catalog. Or, you might consider And, for those who are 14110111110111111000000000000, getting a special VHF re- curious, Canadian weather ceiver intended for picking broadcasts take place on up only NOM transmissions. 161.65 and 161.775 MHz. Radio Shack has six dif- Midland's WeatherMax 74 -104 VHF weather monitor offers a ferent models for desktop ANYBODY KNOW AM /FM reception and a couple of bonuses: siren to signal any and handheld use. The THIS SET? severe- weather alerts. prices range down to as We received a letter and United States. Depending little as $17.95. The deluxe photo from Jack DeAl- upon the area in which you ($39.95) unit will respond to meida, 18017 Horst Ave., live, your local broadcast a special coded signal sent Artesia, CA 90701. Jack re- might be on 162.40, out by an NOM station, ports that he has an "old" 162.475, or 162.55 MHz, Dur- sounding a siren -type scanner that serves him ing times of approaching alarm in the receiver (even well, but is capable of re- severe weather (thunder if the set is turned off) to ceiving only the 148-174- storms, hurricanes, tor- alert you to impending MHz and 450 -470 -MHz nadoes, etc.), or at other danger. All of these sets bands. The set wasn't de- times when there is a dan- operate from, or have signed for receiving the ger to the general public, backup, flashlight batteries UHF -T band (470 -512 MHz), you're likely to hear about it so they'll continue to oper- and he would like to modify first via NOAA VHF radio. ate during power blackouts or adjust the set to function Some CB transceivers in order to continue to in that band in addition to have a switch that will allow bring you updated bulletins. its existing capabilities. The

www.americanradiohistory.comAmericanRadioHistory.Com photo Jack sent shows the ATTENTION! set with its Iwo banks of plug -in crystals exposed. He tells us the set is a Mac- ELECTRO1ÌI(L Donald Instruments Model CE -100. We have never heard of T this set, but would guess EARN YOUR \ that it's from about 1970. If any reader can help Jack, B.S.E.E. please contact him directly Do you know any at the above address. modifications for this old DEGREE MacDonald Instrument's THROUGH HOME STUDY REFERENCES scanner? Our New and Highly Effective Advanced-Place- A while back, Uniden issu- ment Program for experienced Electronic Tech- ed a two -book (East/West) Legally, morally, and nicians grants credit for previous Schooling and eth- Professional Experience, and can greatly re- series of Betty Bearcat po- ically, a receiver can cover duce the time required to complete Program and lice /fire frequency any and all frequencies. reach graduation. No residence schooling required for qualified Electronic Technicians. directories. They were There is no law against im- Through this Special Program you can pull all of nothing much. Meanwhile, porting, selling, or owning the loose ends of your electronics background together and earn your B.S.E.E. Degree. Up- letters we received here such a receiver. Indeed, grade your status and pay to the Engineering also indicated disappoint- some scanners are sold Level. Advance Rapidly! Many finish in 12 months or less. Students and graduates in all 50 ment with the Police Call without any gaps in their States and throughout the World. Established series. Then, in 1989, Uniden 800 -MHz frequency Over 40 Years! Write for free Descriptive Lit- erature. began issuing a different coverage. However, there is series of Betty Bearcat pub- also nothing to stop a scan - lic- safety directories, ner owner from restoring COOK'S INSTITUTE OF ELECTRONICS ENGINEERING dividing the U.S. into seven any blocked out frequen- regions represented in dif- cies, a relatively simple task 4251 CYPRESS DRIVE CiEE JACKSON, MISSISSIPPI 39212 ferent books. That series that can be performed by now includes even a Cana- the average hobbyist. Or, a CIRCLE 8 ON FREE INFORMATION CARD dian directory, plus a 651 - converter can be obtained page National Police Fre- to provide 800 -MHz quency Directory. coverage. AMAZING It appears to us that Uni- The frequencies that are SCIENTIFIC & ELECTRONIC den's series quickly became blocked out are those allo- PRODUCTS very popular within the cated for cellular-phone hobby. We notice that use. Manufacturers who sell LASERS AND SCIENTIFIC DEVICES many local Radio VRL2K 3mw Vis Red Laser Diode System Kit $159.50 Shack scanners with blocked -out LLIS1K Laser Beam "Bounce" Listener Kit $199.50 stores no longer have bands do so as a matter of LHC2K Visible Simulated 3 Color Laser kit $44.50 LC7 40 Watt Burning Cutting Laser Plans $20.00 Police Call in stock, and the their own choice. The best RUB4 HI Powered Pulsed Drilling Laser Plans $20.00 Radio Shack simply guess we 101140 1 to 2mw HeNe Vis Red Laser Gun Assembled $199.00 catalog can take to ex- LLS1 Laser Lite Show -3 Methods Plans $20.00 notes that they are "Avail- plain this is that they also SD5K See In the Dark Kit $299.50 EML1K Electromagnetic Coil Gun Kit $69.50 able on special order." sell cellular phones and MCP1 Hi Velocity Coil Gun Plans $15.00 It looks as LEVI Levitating Device Plans $10.00 though the perhaps fear complaints EH1 Electronic Hypnotism Techniques Plans $10.00 Uniden books have from those customers about HIGH VOLTAGE AND PLASMA DISPLAY DEVICES eclipsed everything else in providing equipment that HVM7K 75,000 Volt DC Variable Output Lab Source Kit $149.50 10G3K ton Ray Gun Kit, project energy without wires $69.50 the area of general police/ can so easily be used to 9169K 129/115 VAC Hi Out Neg Ion Generator Kit $34.50 EMA1K Telekinetic Enhancer/Electric Man Assembled $99.50 fire scanner data. You might (illegally) eavesdrop on cel- LG5K Lightning Display Globe Kit $54.50 want to check out the Uni- lular calls. BTC1 K Worlds Smallest Tesla Coll Kit $49.50 BTC3K 250KV Table Top Tesla Coll Kit $249.50 den series. They are sold by BTC5 1.5 Million Volts Tesla Coil Plana $20.00 JL3 Jacobs Ladder -3 Models Plans $15.00 many leading dealers. Their MARSHAL PLAN GRA1 Anti Gravity Generator Plans $10.00 PFS20 Plasma Fire Saber Assembled list price is $14.95 each. The U.S. Marshal trans- $69.50 DPL20 Dancing Plasma to Music and Sounds Assembled $79.50 ports federal prisoners, SECURITY AND PROTECTION DEVICES LOCKED OUT! protects federal witnesses, ITM10 100,000 Volt Intimidator up to 20' Assembled $129.50 IP070 Invisible Pain Field Blast Wave Gen Assembled $74.50 "Why did the factory lock captures federal fugitives, PSP4K Phasor Sonic Blast Wave Pistol Kit $59.50 out LIST10 Infinity Xmtr, Listen in Via Phone Assembled $199.50 some 800 -MHz frequen- and provides a myriad of TAT30 Automatic Tel Recording Device Assembled $24.50 cies in my Realistic other fascinating services. VWPM7K 3 Mi. FM Auto Tel Transmitter Kit $49.50 FMV1K 3 Mi. FM Voice Transmitter Kit $39.50 PRO -2006? I thought that Some of the agency's bet- HOD1K Homing/Tracking Beeper Transmitter Kit $49.50 receivers could cover all ter nationwide frequencies EASY ORDERING PROCEDURE TOIL FREE 1 -900- 221 -17D5 or 24 HRS ON 1-603 -673 -4730 or FAX IT TO 1 -603- 672 -5406 frequencies." That not -un- include: 162.7125, 162.7875, VISA. MC. CHECK. MO IN US FUNDS. INCLUDE 10"/, SHIPPING. ORDERS $100.00 a UP ONLY A00 $10.00. CATALOG $1.00 OR FREE WITH ORDER. common question arrived 163.20, 163.8125, 164.60, in a letter from Clint Yates of 165.0625, and 165.7125 INFORMATION UNLIMITED Pine Bluff, AR. MHz. P.O. BOX 716, DEPT. PE, AMHERST, NH 03031

83 www.americanradiohistory.comAmericanRadioHistory.Com DX LISTENING

By Don Jensen der here is a lot of news has some thoughts on the While a number are taken and music on SW, reasons: "Since much off the air, usually with the and that's fine, but what humor is topical in nature, imposition of substantial

about comedy? Though I and uses domestic politics fines and confiscation of tune around to different sta- and politicians for fodder, transmitting equipment,

tions, I haven't found much humor doesn't often travel others have continued for Shortwave comedy. Any thoughts ?" well via shortwave." years. That's the complaint from An exception, Richard They are, indeed, illegal

Radio: It's No one of our readers, Sam suggests, is the CBC's satir- and I do not endorse their Terry of Port Angeles, WA. ical show, "Double activities. But, ignoring the Laughing That's all too true, Sam; Exposure." 'While that pro- presence of these scores of there isn't very much to gram is intended primarily sporadic voices is akin to Matter! laugh at on shortwave. And, for a Canadian audience," sticking your head in the historically, there have only he says, "it is often a treat shortwave "sand." They are been a couple of suc- for U.S. SWL's, as well, with there, at least once in a cessful comedy programs some understanding of Ca- while, and, along with pop on shortwave over the nadian politics. Double music, humor is a staple Exposure," he writes, "is re- fare. Some of the pirate layed on shortwave by comedy is crude, soph- RADIO CBC's Northern Quebec omoric, and genuinely Service at 1637 to 1700 UTC, awful stuff. But, much of it is KOREA Saturdays, on 9,625 kHz." fresh and clever parody. At this writing, a fiscal This is the sort of program- crisis has left uncertain the ing that I'd like to "see" broadcasting future of the more of on shortwave ra- CBC's Radio Canada Inter- dio!

national. While I cannot Some listeners hate the believe that Canada will idea of pirate broadcasters. totally abandon its interna- Others love them, despite

tional shortwave voice, I or perhaps because of their don't know if this favorite quirky nature. If you fall in station of many SWL's will the latter category, one of continue with its present the best guides to the pi- level of programming. If, rate -radio netherworld is however, only limited the 1991 edition of George schedule changes result, Zellers The Pirate Radio Di- you may still find Double rectory (Tiare Publications, Exposure aired interna- PO Box 493, Lake Geneva, Korean cultural tradition is tionally on RCI, Mondays at WI 53147; $8.95 plus $2 reflected in this ancient 0037 UTC on 5,960 and bronze, illustrating one of shipping and handling). the program schedules sent 9,755 kHz. to SW listeners by Radio Although the subject is MORE LETTERS

Korea in Seoul. controversial, I should also I am delighted to report note that the spate of un- that the volume of mail years. One of my favorites licensed "pirate" stations is from you readers grows was the now departed and probably the major source each month. This is, after all, much lamented "Royal Ca- of humor programs on your column and the short- nadian Air Farce," a shortwave today. Because wave -radio subjects domestic Canadian Broad- these stations are un- casting Corp. show that authorized, unregulated, *Credits: W. Karcheski, MA; was rebroadcasted SW in on and violation of the law, Rufus Jordan, PA; Bob Zilmer, in years past. they operate only NM; Sheryl Paszkiewicz; Ed Richard Cuff, whose ex- periodically and irregularly, Cichorek, NJ; Brian Alexandr, cellent "Easy Listening" mostly in the 7,355 -7,550 PA; Harold Frodge, MI; David Copp, IL; John Carson, OK; column appears monthly in kHz range, to avoid being North American SW Associa- The Journal of the North tracked down by the tion, 45 Wildflower Road, American SW Association, broadcasting authorities. Levittown, PA 19057.

www.americanradiohistory.comAmericanRadioHistory.Com .

DIGITAL VIDEO STABILIZER ELIMINATES ALL VIDEO COPY covered in DX Listening will raid caused only seven PROTECTIONS reflect your interests when slight injuries." you write in. What questions Another bit of information do you have about on wartime monitoring of SWL'ing? Your comments on shortwave comes from Jer- While watching rental the international- broad- ry Bartok, Chapel Hill, NC. : movies, you will notice an- WARNING casting scene today? What He notes that he tried to noying periodic color darkening, color shift, un- SCO are you hearing on short- follow Iraq's Radio wanted lines, flashing or Electronics and You Jagged edges. This is wave? can reach me Baghdad, but found them caused by the copy protec- RXII dealers do letters to in English tion jamming signals em- by addressing your only on a few bedded In the video tape, not encourage DX Listening, Popular Elec- occasions after the air war such as Macrovision copy people to use protection. Digital Video tronics, 500 -B Bi- County started in mid -January. "It Stabilizer: RXII completely the Digital eliminates all copy protec- Blvd., Farmingdale, NY was possible, however, to tions and Jamming signals Video Stabilizer and brings you crystal clear to duplicate 11735. Oh, and by the way, hear a number of different pictures. photos of you and your Arabic- language Iraqi FEATURES: rental movies Easy to use and a snap or copyrighted listening setup are also transmissions," Jerry says, to Install State-of-the-art in- video tapes. more than welcome! "including the General Ser- tegrated circuit technol- RXII is in- The Gulf War earlier this vice, the Voice of The 1 0096 automatic - no tended to stabi- need for any year focused a surprising Masses and the so- called troublesome adjust- lize and restore ments amount of attention on Mother of Battles Radio, on Compatible to all types crystal clear shortwave. Newspapers frequencies ranging from of VCRs and TVs picture quality The best and most excit- from the New York Times to 3,980 and 8,350 kHz to ing Video Stabilizer in for private the market hometown weeklies fea- 15,600 and 17,940 kHz." Ught weight (8 ounces) home use only. and Compact (1x3.5x5') tured stories of shortwave Although the bombing Beautiful deluxe gift box ( Dealers Welcome ) listening and listeners. Sales reportedly Uses a standard 9 Volt knocked out battery which will last 1- of SW receivers boomed, Baghdad's international 2 years. with many radio dealers broadcasting facilities, the ToOrder: $59.95 ea + $4 for FAST UPS SHIPPING sold least out, at tem- Iraqis remained on the air, 1- 800 -445 -9285 or 516 -568 -9850 porarily. And, indeed, there seemingly using Kuwaiti Visa, M/C, COO M -F: 9.8 (battery not Included) was much fascinating listen- transmitters. Jerry says he SCO ELECTRONICS INC. Dept r,PE9 581 W. Merrick Rd. Valley Stream NY 11580 ing for SWL's who tuned in heard Baghdad's interview Unconditional 30 days Money Back Guarantee on breaking news from the of captured US airmen -"a CIRCLE 13 ON FREE INFORMATION CARD Mideast. real scoop " -on 11,990 kHz --1 One of our readers, J. before it was broadcast on TV Keith Dunbar of Jamestown, CNN or the television net- CABLE KY, passes along some of his works. DESCRAMBLER experiences: "At 0125 UTC Thanks, Keith and Jerry, You Can Save Money on Jan. 18, I received a for passing along those re- on Cable Rental Fees broadcast from KOL Israel ports; they're good on 7,465 kHz. The normal examples of what short- foreign service broadcast wave can deliver in times of was discontinued for 35 important world events! My minutes, after it was an- own vivid memories of tun- nounced that an Iraqi ing in the Gulf War include MEP SCUD missile had hit Tel Aviv. a pair of listening vignettes, 1 Unit 5+ Jerrold SB w/Tri-Bi $99 $70 Instead, there was an an- both from Israel's radio: The Super Tri-Bi (TBM) $109....$75 Us Cable will Jerrold 450 combo $189..$139 Beat Anyone's nouncement that Israeli eerie wailing of the air -raid Scientific Adanta. $109....$75 Price SA 8536. $u0. . -$195 citizens could remove their sirens signaling a missile at- Pioneer $109....$79 Advertised In Oak KN12(w/VS) $109...$65 this Magazine! gas masks, but should stay tack, early in the hostilities, Hamlin MLD 1200. $89 $59 in KOL Israel's hourly Tocom $169....$129 their sealed rooms. and the Stargate converter $89 $69 "At 0200 UTC the broad- playing and replaying of PanasonicTZPC145 $99 $79 cast continued with a Kate Smith's "God Bless 30 Days Money Back Guarantee Free 16 page Catalog telephone number for Civil America" when the Visa, M /C, COD or send money order to: Defense departments in Is- ceasefire was announced. US Cable TV Inc. Dept. KPE9 rael, and a warning to keep Next a letter from Dr. 4100 N.Powerline Rd., Bldg F -4 gas masks ready and to Sabastian J. Kenight, Pompano Beach, FL 33073 stay tuned for further up- Rochester, MI, who refers to dates and warnings. KOL the station chart that came 1- 800 -772 -6244 Israel reported that another with the shortwave -radio kit For Our Record I, the undersigned do hereby declare under penalty of per- SCUD missile was knocked he bought and built. "I have jury that all products purchased, now and in the future, will only be used on Cable 'IV systems with proper authorization down over Dhahran, Saudi not been able to listen to from local officials or cable company officials in accordance with laws. the USS all applicable federal and state FEDERAL AND Arabia, near a U.S. military Hope hospital ship VARIOUS STATE LAWS PROVIDE FOR SUBSTANTIAL base. Later it was an- or the World Health Organi- CRIMINAL AND CIVIL PENALTIES FOR UNAUTHORIZED USE. nounced that the Tel Aviv (Continued on page 89) Date: Signed: No Florida Sales! 85 CIRCLE 14 ON FREE INFORMATION CARD www.americanradiohistory.comAmericanRadioHistory.Com HAM RADIO

By Joseph J. Carr, K4IPV A t least once a year, I weekend cabin in the operating frequency at like to cover some mountains of western Vir- center band in megahertz. technical questions from ginia, on the west slope of The radial can be con- personal contacts and the the Shenandoah Valley. nected to one of the mail bag, so this month's The ham routinely used grounded mounting bolts column will be a "potpourri the 'corn HF mobile trans- with an alligator clip, but A Random of ham -radio exotica and ceiver from his vehicle that's not really such a miscellania" (or some such). indoors on these little week- good practice. Alligator Walk Through Although a lot of readers enders. The Kawasaki light - clips do not make good RF ask questions related to the plant generator he uses has connections. A better solu- The Technical ham -radio hobby, many of a 12 -volt DC output suffi- tion is to mount a those queries are not gen- cient to power the rig, even grounding type five -way Mailbag eral enough to be while supplying 115 -volt, 60- binding post to the mobile discussed in this column. Hz AC for the lights in the antenna mount through a However, the ones that are cabin. He didn't want to new hole drilled for that selected are intended to leave an antenna erected purpose. Underneath the reflect a cross section of the at the site-it would get car's body panel, make more popular questions stolen as did some light sure that the paint and un- asked of me. appliances and a gener- dercoating are well ator -and he didn't want to cleaned, and the metal is íj waste time each weekend bright. Run a short, heavy erecting a temporary an- piece of braid from a piece tenna. His solution was to of coax to the coax trans- WHIP use the mobile antenna on mission -line shield, and its ANTENNA the car with a long piece of own grounding point. 52 -ohm coax "extension To operate, take the radi- cord" from indoors to a al out of the trunk, double female "barrel" straighten it out, and con- connector under the dash. nect it to the binding post. The problem is simple: HF Run the radial either a short MOBILE BINDING mobile antennas are terri- distance above the ground, POST MOUNT bly inefficient compared to or laying on the ground, dipoles and full -size ver- and secure its far end to a ticals. What could he do to convenient tree or fence improve the situation? post. The best operation As it happens, we were occurs when two to six such standing next to the display radials (running from the of an antenna dealer (the same binding post) are CAR BODY only products on display) used, but substantial im- X/4 RADIAL who stocked a "quarter- provement may be had

wavelength radial kit" for with only one. I used that Fig. I. Adding quarter -wave- vertical antennas. It con- method when I lived in length radials extend mobile - tained a set of pre rented property, and could antenna range and efficiency. -cut wires, several ceramic end not erect a permanent an- insulators, and about 50- tenna at the house.

EXTENDING MOBILE/ feet of nylon rope. I picked One note, however: Be PORTABLE OPERATION up the kit, and told him use absolutely sure that no vis- At a hamfest last summer this. itors, small children, or (1990), a reader recognized Refer to Fig. 1. The quarter - yourself can accidentally my callsign, and asked me wavelength radial is made trip on the wire. Also keep in about a little problem that from #14 or #12 wire, the mind that the end of the he was trying to solve. Inter- length of which is given by: radial wire is a voltage estingly enough, the node, and can cause a L = 492/f solution was right in front of nasty shock and RF burn. If him (as you'll see in a mo- where L is the length of the you are using high power ment). He owned a small radials in feet and f is the (or even sometimes 100

86 www.americanradiohistory.comAmericanRadioHistory.Com watts), an arc can cause a repeater could tell when he +'d fire. So be very careful with was overmodulating his 2- the installation of the tem- meter FM rig. An unmodu- Vi porary radial. lated FM transmitter outputs This question seems to only one frequency, the come up periodically. That's carrier (fc. When it is modu-

one of the reasons why I lated, the carrier frequency wrote about this solution in swings above (positive de- my book Practical Antenna viation) and below POSITIVE DEVIATION Handook (TAB Books, Inc., (negative deviation) the Blue Ridge Summit, PA, carrier The frequency. dis- i 17294-0850; to order, call tance from the carrier to f +f í tut 800 -233 -1128) Cat. No. the maximum and mini- 1 3270, $21.95. mum frequencies is a function of the 1.1 NEGATIVE audio -signal DEVIATION THE "OTHER" COAXIAL amplitude, while the CONNECTOR number of times per sec- A reader sent me a color ond it swings back and snapshot of an "odd- ball" forth is a function of the coaxial connector that he audio -modulating frequen- found on a piece of anten- cies. na test equipment that he Most ham systems are recently bought. He asked optimized around a nar- -V

that I identify it. Simple: It's a row -band FM standard, ± 6 Fig. 2. FM discriminator characteristic curve. BNC connector. Ifs used on kHz deviation, for example. a wide variety of instru- In other words, a maximum ulator IC isn't so politics, and social issues on ments, and has all but signal will cause the carrier accommodating), then you ham radio ?" replaced the PL -259/ frequency to deviate fc + 6 might want to try another First, it's not illegal to dis- SO -239 combination "UHF" kHz, and fc - 6 kHz. The approach. Heath sells a cuss those topics. The connectors used on most repeater would produce a battery- operated, FM de- Communications Act of receivers and transmitters. 1000-Hz beep when the deviation meter in kit form 1934, under which hams One advantage of the BNC viation exceeds + 6 kHz, or (Model IM -4180) that will do operate, did not repeal the connector is that it exhibits a 400 -Hz beep if it exceeds the job nicely. It is basically First Amendment of the U.S. a constant (or so) nearly - 6 kHz. Some repeaters a metered, tunable re- Constitution. As far as I impedance, despite the also tell you when your car- ceiver operating in the VHF/ know, only obscenity (which fact that it represents a dis- rier frequency is above or UHF bands. Press the TUNE is different from profanity, if continuity in the below the set "netted" val- button, and then peak the the crowd sometimes transmission line. ue. meter with the tuning knob, heard on 75- and 20- The BNC connector is How, you ask'? The means while transmitting on the rig meters SSB is any measure) "bayonet" style, rather than for producing that informa- under test. Press one of the is illegal. screw threaded. In other tion is essentially the same deviation -range buttons (2 -, However, hams have tra- words, to attach a BNC for each case. Both systems 7.5 -, 20 -, and 75 -kHz full - ditionally refrained connector, it is pressed onto measure the output voltage scale are the selections; the voluntarily from discussing its mate, and then given a from the FM demodulator latter being for FM- broad- those potentially explosive half -turn in the clockwise (discriminator) in the FM re- cast transmitters), while still issues in recognition that we direction. Removal requires ceiver. Figure 2 shows the transmitting, and the devia- are a widely varied plurality exactly the opposite rota- characteristic curve for an tion will show on the meter. on the ham bands. All re- tion. That form of adapter FM discriminator. Suppose The IM -4180 can be used as ligions, all political can be used to trou- fu and k are the upper and a receiver (a speaker out- persuasions, all races, all bleshoot circuits with a lower deviation limits for the put jack is provided), and it nationalities and ethnic signal from a BNC - system. Those limits produce can also be monitored on groups, and all manner of equipped instrument. Get output voltages of V1 and an oscilloscope for a more social opinions are found used to BNC's, they have V2, respectively. A voltage dynamic look at the rig's on our frequencies. For the almost totally replaced the comparator, or similar cir- performance. sake of order, common de- UHF connector, except on cuit issues a digital output cency, and good manners, the backs of transmitters. bit every time one of the NOTE TO A READER we don't discuss issues that Even some receivers use pre -set limits is exceeded. One reader wrote to ask are so vitally contentious. them for the coaxial anten- Of course, if you want to an operating question, but You can start such a con- na connection. measure the deviation failed to provide a return versation, if you really want yourself, and don't want to address. His or her question to, but expect to receive MEASURING FM -RIG butcher a good VHF FM, was so important, however, disapproval from other DEVIATION ham -band receiver to tap that it merits a mention. The hams who are exercising Another reader wanted the discriminator voltage reader asked "Why is it il- their own First Amendment to know how come his local (or find that the FM- demod- legal to talk about religion, rights.

www.americanradiohistory.comAmericanRadioHistory.Com causes Q1 to turn on -the r CIRCUIT CIRCUS degree to which Q1 turns SPECIAL FROM ETT (Continued from page 76) is Ll PCP101- PRACTICAL on determined by the DIGITAL ELECTRONICS amount of moisture de- HANDBOOK ... $9.95. In- changed by decreasing or tected in the soil. That troduces digital circuits, logic gates, bistables and increasing the number of causes a voltage to be de- timers, as well as micro- turns in L1. For higher fre- veloped at the emitter of processors, memory and quency operation, reduce Q1. That voltage is fed to input/output devices. Spe- 1 cial section on digital test the number of turns. For the input of U1 (the bar/dot gear projects. lower frequency display driver). The ten LED's, PCP102- INTRODUC- operation, ING DIGITAL AUDIO ... increase the number of connected in the bar con- $9.95 Shows what is in- turns. figuration, light up to volved in the digital part of audio signals, particularly The values of C1 and C2, indicate the soil's approxi- in the newest devices such in Fig. 4, also may be varied mate moisture content. as CD, DAT and sampling. to shift the oscillator's fre- The best material for the Bridges the gap of understanding for the technician quency. To lower the probes is stainless steel, but and enthusiast. oscillator's frequency, in- almost any metal will do as PCP103- PRACTICAL crease the value of C1 and long as it is kept clean. A MIDI HANDBOOK ... $9.95. Covers all MIDI C2, and for a higher fre- simple way to calibrate the based equipment you can quency operation circuit is to short the probes use -keyboards, drum decrease their values. together and adjust R4 until machines, sequencers, effects units, mixers, A carbon microphone all of the LED's light. That, of drum pads and guitars. can be used in place of R1 course, indicates too much Also a section on comput- in Fig. 5, turning the os- moisture. Now take your er music that covers software and more. cillator into a low -power FM moisture meter to an expert PCP104 -ELEC- TRONICS BUILD & transmitter. The carbon mi- gardener and check out a LEARN, Second Edition crophone's internal number of plants to get an You start by ... $9.95. as- resistance varies in step idea how many LED's sembling a circuit demon- strator that is then used to with the audio, causing the should light when the soil build and investigate a va- current flow through L1 to has the proper moisture riety of useful circuits in- in manner. The cluding oscillators, multi - vary a like content. vibrators, bistables and varying current through L1 logic circuits frequency modulates the PCP105 -MAKE Flits mane? it HOME lIECOB011t6 MONEY FROM HOME RE- oscillator. CORDING ... $10.00. Now COMPUTER BITS that you've spent all that MOISTURE MONITOR (Continued from page 71) money on all that recording gear, wouldn't it be Our last entry for this nice to get some of it month is ideally suited to of, and are supported di- back? Well here's the book the horticulturist in your rectly by the respective that can show you how. PCP106- SYNTHE- family. If the majority of the companies. SIZERS FOR MUSICIANS plants that you have end The Mylex and Haup- ... $10.00. All current up like specimens from the pauge boards are popular forms of synthesis explained; LA, ad- petrified forest, or like drow- produced domestically and ditive, phase distortion, ning rats in a flash flood, it's are of the highest quality. FM and sampling. Get the They normally sold sounds you want from probably due to improper are your synth. Written es- watering. Too much or too through dealers, although pecially for musicians. little moisture can end the Hauppauge indicated a

MAIL TO Electronic Technology Today, Inc. life of even the most hardy willingness to sell directly to P.O. Box 240 plant. end users. Pioneer sells only Massapequa Park, NY 11762 -0240 The moisture monitor through dealers. SHIPPING CHARGES IN USA AND CANADA shown in Fig. 6 will help In general, since I began

$0.01 to $5.00 ... $1.50 $30.01 to 40.00 .. $5.50 keep the plant life around the process of evaluating $5.01 to $10.00 .. $2.50 $40.01 to 50.00 .. $6.50 you green and healthy. The these boards, prices of

$10.01 to 20.00 .. $3.50 $50.01 and above . $8.00 circuit is built around a boards at all performance $20.01 to 30.00.. $4.50 SORRY, No orders accepted outside of USA and 2N3904 general -purpose levels have nosedived, and Canada NPN transistor (configured the trend will continue. It Total price of merchandise $ as an emitter follower), an seems that no matter when Shipping (see chart) $ LM3914 dot /bar display driv- you buy, you can make a Subtotal $ Sales Tax (NYS only) $ er, and a few support better deal six months later. Total Enclosed $ components. The probes However, that's the nature this business. Name and the emitter follower of Spend a Address (Q1) sample the current little bit more now and your City State Zip flow through the soil. Cur- investment will last a little bit rent flow through the soil longer.

www.americanradiohistory.comAmericanRadioHistory.Com America at around 1200 DX LISTENING UTC. (Continued from page 85) DOMINICAN REPUBLIC - Enter A World Of Excitement with a Subscription to 4,930 kHz. Radio Barahona zation, or the medical is an old station that re- network from Europe or sci- turned to shortwave after a Popular Electronics entific transmissions. The long, long, absence. It has

,..,.. chart says they should be been heard with all- Spanish Get the latest electronic technology Peeled tpl, A, Ggnlitimm Fran Paver UM hallema around 10-20 meters. Also, programming during the and Information monthly! Popular Electronics Now you can suhsenbe to the magazine that plugs yxm into what happened to the Phi- 0030 -0100 UTC time slot. the exciting world of electrum.. With every issue of Popular Electronics you'll find a wide variety of electmnics project lippines and Scotland ?" JORDAN -9,560 kHz. vou an build and enjoy. IMpular Electr.mcs hangs nm inóomatie new product and literature listings. feature articles in test equipment and Sadly, doctor, such charts Radio Jordan, with English tools- it designed to keep you tuned in to the latest development in electronics. S/../.P... boon to build f,ainatng are virtually worthless! At news and musical requests, electronics. just Minot the subscription Sinn below to sub- scribe to Popular Plectron. ICs a paver-house of fin for best, they are outdated. At is heard with good signals the electronics enthusiast. worst, they are just plain during the 1500 to 1600 UTC EXCITING MONTHLY FEATURES LIKE: J CONSTRUCTION -Budding po e, t. 'rum ono, vt. to wrong! And when they are hour. elmtronw roulette FEATURES -Educational training.., digital electronics. ihm c I.aw Arion,,,. Communwatons, Antique Radin right, they often leave but LEBANON-6,279 kHz. Simplified Thou, J HANDSON-REPORTS-L..r test.omment, on mince essential information about IGng of Hope is an Ameri- unusual consumer priduro J SPECIAL COLUMNS-Think Talk. C ncwtCncus. Coo; the nature and mode of can -owned and operated puter Ries De I.otening Antique Radio Amateur. Sa,o, transmission, leaving the in- religious broadcaster oper- PLUS: ALL OUR GREAT DEPARTMENTS! FOR FASTER SERVICE CALL TODAY correct impression that ating from southern - .L,,., tOora,u. ion,, t. ,,Ih..egut 1- 800 -435 -0715 simile.,cope ploc Suh. enhe tu bona, Electmiucn Iday'.li,t R1 out me subscription order Lum below. (7,30AM-830PM) limited or occasional ama- Lebanon, near the Israeli EAStERNS1ANDARUnME teur or utility -type border. The station has r i communications are reg- been noted with English - Popular Electronics SUBSCRIPTION ORDER FORM li,i Box 3u1. Mt. Moms IL. 611154 APEJI ularly heard voice language religious pro- YESI I want to substnhe Co Nina., Electronics for PLEASE PRINT BELOW:

Full roar I I . Issue.. for only $IN 95, Mid 's a savings broadcasts. gramming and ,f E16.45i aï the msestand price- J Payment Enclosed J Mime Litr Additionally, vague fre- identifications at around l'lo' charge my. J Visa J M,stercant

quency references (such as 2130 to 2200 UTC sign off. 1

10 to 20 meters) are of no MONGOLIA- 12,015 kHz. Esp. Dat., real help, since they span a Radio Ulan Bator operates huge range of frequencies, on this frequency in English nearly 15,000 kHz! That's during the early morning - about as helpful as direct- hours, until 0940 UTC, when ing a motorist running out the station's programming of gas by "pinpointing" the language to changes Chi- Every month Monitoring Times brings location of a service station nese. everything you need to make the most as "somewhere in the state NORTHERN MARIANAS- of your general coverage transceiver: of Montana!" 15,405 kHz. KHBI is a Pacific - the latest information on international Next month, I will suggest area shortwave voice, op- Make the broadcasting schedules, frequency the some more up -to -date and erated by Christian listings, international DX reports, accurate sources for station Science Monitor, broad- most of your propagation charts, and tips on how to frequency and schedule in- casting from Saipan. The general hear the rare stations. Monitoring formation. station's English program- Times also keeps you up to date on ming heard at can be coverage government, military, police and fire DOWN THE around 2200 UTC, with DIAL networks, as well as tips on monitor- Your listening reports are some interference from the transceiver ing everything from air -to-ground and wanted. Why not pass Voice America Ger- of and with ship -to -shore signals to radioteletype, along your SW tips, what many's Deutsche Welle. facsimile and space communications. you are hearing and when, SOUTH KOREA Monitoring -5,975 ORDER YOUR SUBSCRIPTION to help fellow DX'ing enthu- kHz. Radio Korea is noted limes! TODAY before another issue goes siasts to tuning these on this frequency, and also by. In the U.S., 1 year, $19.50; stations. Remember that broadcasting in parallel on foreign and Canada, 1 year, $26. Coordinated Universal Time 9,870 kHz, in English at 1600 For a sample issue, send $2 (for- (UTC) is equivalent to EST + UTC. eign, send 5 IRCs). For MCNISA CST MST U.S.A-7,416 kHz. Action 5 hours, + 6 hours, orders ($15 minimum), call + 7 hours or PST + 8 hours. Radio is the identifier used 1- 704 -837 -9200. AUSTRALIA -4,920 kHz. by one of the many un- VLM4 in Brisbane is one of licensed U.S. "pirate" MONITORING TIMES the Australian Broadcasting stations sometimes found Your authoritative source, Commission's home service on frequencies in this 41- every month. shortwavers, directed to meter band. It has been Australians living in the rural reported at about 2230 P.O. Box 98 "outback." Still it often puts UTC with popular music and Brasstown, N.C. 28902 a decent signal into North comedy.

www.americanradiohistory.comAmericanRadioHistory.Com nectors, and the backup batteries to MAKE A MAC LASER POWER SUPPLY complete the job. (Continued from page 31) (Continued from page 34) Start Your Engines. Assuming you've When installing the motherboard, we had no problem getting any parts and about V8 inch. If you do not get a spark, found that the "tangs' (identified back have followed the excellent manual to check pin 3 of U1 for the presence of a in Fig. 1) could get in the way. You might complete all the steps, it's time for the 500-Hz signal with an approximate 50% consider using your gas -joint pliers to initial powerup. The manual assumes duty cycle. If that checks out, check the bend the Iwo tangs slightly to eliminate you will be using the ATS monitor and two transistors for proper orientation that problem. gives you a few simple steps for adjust- and output. The instruction manual tells you to ing the image (horizontal and vertical). If you get the proper response, re- mount three standoffs to the mother- These steps call for the use of an insu- move power from the circuit and dis- board. A word of caution, while it might lated screwdriver, but our experience connect the lead from the center seem more logical to mount the stand- has indicated that the same small flat - terminal of the coil. offs first to the case, and then mount the blade screwdriver we used earlier can motherboard on them, you are advised easily accomplish the task. If you have Preparing the Laser Tube. Most laser not to try it. Stick to the instructions in this another monitor, naturally the set -up tubes come with clips attached to the respect. will be different. However, we strongly ends (see Fig. 4). Remove the clips , but The instructions call for 'veto paper recommend that you acquire the ATS do not discard them; they will be used washers" to mount each standoff to the monitor or an exact equivalent. to deliver power from the Laser Power motherboard. This was not exactly All of the necessary instructions to Supply to the laser tube. If your tube accurate. First, there are only three such configure and set -up your Macintosh doesn't have clips, do not attempt to washers supplied (you would need a clone are augmented with some addi- solder wires to the tube ends. The ends total of six) and they are really made of tional information that might be of use contain mirrors that allow the tube to fiber. However, there are three other should you have problems with your lase. Their alignment will be distorted if washers supplied. They are black in fixed- or hard -disk drive format, or in heat is applied directly or too close to color and seem like plastic. Figure 6 case of other problems. them. If the tube doesn't have clips, the shows the assembly for mounting the We promised to show you how to high -voltage wires will have to be standoff hardware. We placed the build your own Macintosh, and have wrapped around the ends. Also, laser plastic -type washers on the foil or bot- succeeded not only in demonstrating tubes might have adjustment screws at tom side of the circuit board, and used how to build a "street- legal" Mac, but their ends that are used to align the the paper washers on the top or corn - one that even Apple hasn't considered. mirrors, which are factory set by the ponent side of the motherboard. All What we mean is an expandable Mac- tube's manufacturer. Do not attempt to other steps and procedures remained intosh platform, with power for all of the re -align the mirrors. the same. possible accessories and adapters Now is the time to consider the en- The next phase of the installation presently or soon to be available for the closure. The author's unit was enclosed concerns the on -board SCSI 3.5 -inch Macintosh computer family. in a Carlon electrical feed -through box, disk drive. In our system, we decided to As we were going to press, we see Fig. 4, which is normally used for make use of an external drive, and learned of yet another ATS Convertible plastic conduit. It was necessary to were able to skip these steps. However, Kit, this one based on the now-avail- fashion collars to secure the tube in po- the instructions are clear, and accom- able Mac SE motherboard that will en- sition. For that task, the author used two modate virtually any Macintosh -com- able you to have more performance, pieces of plastic conduit tubing, which patible 3.5 -inch SCSI drive. more features, and at a lower cost, de- were cut to about 1 inch. The 1 -inch The balance of the assembly process spite the increased cost of acquiring a is purely mechanical with the manual Mac SE motherboard. You may want to clearly directing you to install and posi- look into one for yourself. tion the cables, etc. The key to a suc- We'd like to acknowledge the as- cessful Macintosh clone lies with the sistance of ATS's president John Yaeger connections of the various (clearly for his help and permission to re- identified) cables to the ATS power sup- produce line art from the Convertible's ply and video adapter. Manual. The single -board video adapter is the "magic" we alluded to earlier in this article. Customer engineered and built by ATS, this single board (see Fig. 7) is the difference between a project that "anyone" with a few common hand tools can complete and a project which should be attempted by only the Here is the Laser Power Supply board most experienced and prolific mounted to the auto ignition coi!. Note "hacker." The instructions that are in- ELH that the board is held in place by screws cluded with the kit clearly describe how aKa on the coil's positive and negative power- to connect the remaining cables be- "Connect parts A, B, and C in slots D, E, input terminals. Those screws also make tween this board, the power supply, the and F. respectively with tool G...What in electrical connection_ from the board to the the H are they talking about ?" floppy drive, the SCSI and video con- coil. 90

www.americanradiohistory.comAmericanRadioHistory.Com lengths of tubing were cemented in-

side the lead -in holes in the feed - through box. Tiny holes, just large enough for pieces of heavy -gauge bus wire to pass through, were drilled at the Popular Electronics áóóK's:oRE conduit /feed-through box joint at both ends of the enclosure. A pair of small 221 Popular Electronics (1991 back issues) $4.00 107 Radio-Electronics (1987 back issues) . $5.25 holes were also drilled in one wall of the Write in issues desired Write in issues desired

enclosure for the leads that connect 220 Popular Electronics (1990 back issues) $4.50 106 Radio-Electronics (1986 back issues) . $5.50 the tube to the power supply. Write in issues desired Write in issues desired Once the holes have been drilled, 119 Popular Electronics (1989 back issues) $4.75 Write in issues desired insert REPRINTS REPRINTS the laser tube (with clips re- 118 Hands -On Electronics (1988 back issues) moved) into the enclosure. Solder short $5.00 169 Think Tank (133 Circuits) .. 53.50 Write in issues desired lengths (about 2 to 3 inches long) of bus 169A Think Tank Vol. 2 53.00 117 Hands -On Electronics wire to the clips. Then insert the free 168 Fact Cards ( #34 -66) 54.00 (1987 back issues) $5.25 ends of the wires through the holes at Write in issues desired 168C Fact Cards ( #67 -99) $3.50 the conduit /feed- through box joints. 116 Hands -On Electronics 168D Fact Cards ( #100 -132) .. 53.50 (1986 issues) Solder one lead of a 75k, 3 -watt ballast back $5.50 167 Designing With IC's $4.00 Write in issues desired resistor to the wire that's connected to 166 Collected Works of Mohammed Ullyses Fips EH91 Experimenters Handbook (1991) .... $4.50 the clip that goes to the glass (62 pages, April Fools Collection) $5.00 end of the EH90 Experimenters Handbook (1990) ... $5.00 165 How to Repair CD Disc Players $5.00 tube, and connect one of the heater - EH88 Experimenters Handbook (1988 -89) S5.50 164 Modern Electrics (April 1908) $3.00 cord leads to the other end of the re- EH87 Experimenters Handbook (1987) $6.00 163 Receiving Satellite TV $5.00 sistor. That lead goes to the hot side of HH91 Popular Electronics Hobbyist Handbook' the coil. Solder the other heater -cord (1991) $5.00 162 Build Your Own Satellite TV Receiver $5.00 lead to the other bus wire. That lead will HH90 Popular Electronics Hobbyist Handbook 161 Descrambling (Feb. 1984) $4.00 (1990) $5.50 serve as the wire. 160 New Ideas - 42 Circuits ground HH89 Popular Electronics Hobbyist Handbook CI 159 Low Frequency Receiving Techniques S3.50 Connect the heater -cord leads to (1989) $6.00 Building the Laser Power Supply, with the lead 126 Radio-Electronics Annual 1986 $6.00 and using VLF Antennas $5.00 connected to the 75k resistor going to 211 Radio -Electronics (1991 back issues) $4.00 158 Electro Importing Co. Catalog (Circa 1918) $5.95 the coil's center output terminal (refer to Write in issues desired 210 Radio-Electronics (1990 back issues) $4.50 157 All About Kits $2.00 Fig. 3). Solder the other heater -cord Writé in issues desired 156 How To Make PC Boards lead $2.00 to the appropriate point on the 109 Radio-Electronics (1989 back issues) . $4.75 155 IBM Typewriter To Computer $2.00 printed- circuit board. Now reattach the Write in issues desired 154 How To Repair VCR's $3.50 clips to their respective laser -tube ends. 108 Radio -Electronics (1988 back issues) . $5.00 Write in issues desired 150 Pap TV Decoder (1981) 53.00 Once done, again check your work. If all checks out, you are now ready for the "smoke test." But first make sure that To order any of the items indicated above, check off the If you need a copy of an article that is in an issue we the laser is pointing away from you and/ ones you want. Complete the order form below, include indicate is unavailable you can order it directly from us. your payment, or any reflective surface. check or money order (DO NOT SEND We charge 500 per page. Indicate the issue (month & CASH), and mail to Popular Electronics, Reprint De- year), pages and article desired. Include payment in To be on the safe side, apply only 5 partment, P.O. Box 4079, Farmingdale, NY 11735. full, plus shipping and handling charge. Make checks volts to the circuit. If all has gone well, Please allow 4 -6 weeks for delivery. payable to Gernsback Publications, Inc. you should see a tiny red dot on the wall. If not, check the oscillator circuit; it is the only part of the circuit that is crit- ARTICLE ical. If an oscilloscope is available, check for the presence of 500 -Hz, 50% duty -cycle (or thereabouts) signal. If PAGES MONTH YEAR that checks out, determine whether the transistors are switching. TOTAL PAGES (6)50C each TOTAL PRICE High voltage, but not much current, is required to operate a laser. To test for the presence of a high -voltage output MAIL TO: Popular Electronics from the ignition coil, hold a neon lamp Reprint Bookstore, P.O. Box 4079, Farmingdale NY 11735 All payments must be in U.S. funds near (or connect one end to) the cen- SHIPPING CHARGES IN USA & CANADA ter terminal of the coil. The lamp will $0.01 to $5.00 $1.50 $30.01 to 40.00 . $5.50 SORRY - We only ship to USA & $5.01 to $10.00 $2.50 to . glow in $40.01 50.00 $6.50 Canada the presence of the fields gen- $10.01 to 20.00 $3.50 $50.01 and above 58.00 erated by the coil. Also check the cur- $20.01 to 30.00 $4.50 rent drawn by connecting an ammeter Total price of merchandise 5 between the 75k ballast resistor and the Sales Tax (New York State Residents only) $ Shipping Charge (see chart) $ laser tube. If no current is being drawn, back track until you find the point Name Total Enclosed $ where the signal is lost. If current is de- Address tected, make sure it's within your tube's City State lip PE991 parameters.

www.americanradiohistory.comAmericanRadioHistory.Com RECEIVER SENSITIVITY LOW-THD (Continued from page 62) AUDIO GENERATOR RMS VOLTMETEF SNR in decibels relative to 1 -mW dissi-

pated in a 50 -ohm resistive load. In AF FM- HIGH -Q other words, 1 mW dissipated in a 50- OUT Ba,jte SIGNAL FM RECEIVER 1000Hz 0 ohm load represents a signal level of GENERATOR NOTCH FILTER A Cf S1 dBm. Typical sensitivities specified in dBm range from - 60 dBm to -120 dBm or so. The dBm level of any given Fig. 4. This is a block diagram of a SINAD sensitivity test set -up. The test is performed in signal with power Psig is found from: two parts: first with a filter in the signal path and then without a filter. dBm = 10LOG(Ps;g/.001)

1 is re- If you want to know the amount of load (0 dBmv). The -mV level consid- times specified for the signal level power that a given dBm level repre- ered to be the point at which the pic- quired to cause 20 dB of output -level sents: ture is snow-free. "quieting." This method is preferred by Sometimes sensitivity is specified in some technicians who lack an FM -sig- Ps;g = .001 x 10dBmi10 microvolts (µV). This method simply nal generator because it can be per- If you need to know how much signal states the number of microvolts, im- formed with just a CW- signal (i.e, voltage is represented by a specified pressed across the input impedance of unmodulated) generator. The "quiet- dBm level, then use: the receiver (usually 50 ohms), required ?ng" occurs when an unmodulated sig- to achieve the required signal -to -noise nal is applied to the input of an FM Vs;g 7.07N/Ps;g = ratio. receiver. Tune the receiver off -channel, Another unit, the dBmv, is used in AM sensitivity is usually specified to and measure the rms value of the out- some 1V- antenna and cable -1V sys- achieve a standardized SNR (10 dB is put noise ("hiss") voltage. Next, tune a tems, and refers to a measurement in common) using a given percentage of signal generator to the same frequen- which all signals are relative to a refer- sinusoidal amplitude modulation (30% cy, and increase the output level until ence level of 1 mV across a 75-ohm is typical), of a given audio frequency the noise output voltage drops 20 dB. (400 and 1,000 Hz are common), with The input signal level that produces this the receiver bandwidth set (if it is ad- result is called the "20 -dB quieting sen- justable) to a certain point. For plain AM sitivity," and values on the order of 0.15 receivers, the bandwidth can be just µV to 0.25 µV are typical. enough to pass the highest significant A pulse receiver, such as used in BW AM sidebands. However, for broadcast radar and certain other applications, and communications receivers a may be specified for a certain "tan- bandwidth of 6 kHz is common and 8 or gential" sensitivity level. This sensitivity is 10 kHz for broadcast models. Sen- the pulse amplitude that exactly dou- sitivities of 1µV are common on AM bles the noise -signal amplitude. Thus, receivers. the pulse level is equal to the rms level The sensitivity of a receiver set for SSB of the noise in the system. or CW operation is generally considerably higher than the same receiver set Conclusion. Receiver sensitivity varies A to the AM mode of operation. One rea- from one model to another, even when son for that is that a SSB /CW signal is the Iwo receivers are nearly the same, directly converted to audio and does for several reasons. One reason is that ndt pass through an envelope detector modulation and bandwidth make a as does an AM signal. Second, the difference. Hence the difference be- bandwidth of the signal is considerably tween AM sensitivity, SSB sensitivity, CW less. The latter factor means that the sensitivity, and FM sensitivity on exactly is less, you BW receiver bandwidth so the noise the same receiver. Once appreci- term (which is a function of bandwidth, ate the differences, receiver specifica- among other things) in SNR is also less. tion sheets will not be a mystery. Also, Typical values for a 10 dB SNR are 0.02 to you will be able to spot creative "spec" 0.1 µV. writing on the part of some manufac- An FM receiver must be tested with turers. an FM- signal generator set to some val- For example, a receiver that is used ue of frequency deviation that approxi- mostly for AM- shortwave listening might mates the bandwidth of the typical be promoted using its CW sensitivity.

B signals received. For example, a scan- Why? The narrower CW bandwidth ner or other FM or PM communications makes the receiver look better. If you Fig. 3. The pass -band of a good receiver receiver may require a signal that devi- are aware of such things you'll know has flat response across the tuned with bandwidth (A). The pass -band of a "dog" ates on the order of 2.1 -kHz rms, or 3 -kHz how to avoid comparing apples receiver (B) might yeild a better signal-to - peak, at an audio rate of 1000 Hz. oranges when considering the merits of noise ratio. FM- receiver sensitivity is also some- a receiver.

www.americanradiohistory.comAmericanRadioHistory.Com ELECTRONIC DRAGONFLY WHAT DO ELEC. ENGINEERS DO? FCC LICENSE (Continued from page 58) from 38) (Continued page PREPARATION General Radiotelephone conductive adhesive backing. First sol- There is a flip side, though -pay scal- der a thin -gauge lead to a piece of es tend to rise rapidly at first and then Radiotelegraph copper -foil tape, let it cool, and then plateau after about ten years, unless Amateur Radio Licenses stick it to the piezoelectric -film wings. you go into management. Also, there is We offer the most up-to -date study materials available. Our formats include: tests, audio Do the same on the opposite side of the "engineering half -life." It has been programs, and video programs. the wings in the same position. said that half of what an engineer As shown in Fig. 6, the wings are held learns becomes obsolete in five years. to the body of the dragonfly with dou- I'm not sure I agree with the 5 -year part, ble -sided (cellophane) tape, and the but it is a constant effort to keep up -to-

leads to the wings are soldered to the date. As I look around the industry, I find appropriate pads (points C and D in that the majority of active design engi- the kit) on the printed- circuit board (in neers are under forty. This does not the kit, the red wing -lead goes to point mean that the rest of us have lost our D -for you do- it-yourselfers, that's the jobs, but we have moved into manage- lower pad). The dragonfly is supported ment, sales, or other areas. over the board by a stiff piece of bus Will Rogers once said, "If you want to wire, which is soldered to the pad that's be successful, know what you are indicated in Fig. 4. Be sure to bend doing, love what you are doing, and about 1/4 inch of the lower end of the believe in what you are doing." That is wire at a 90- degree angle before sol- especially true in engineering. If some- dering in place to increase the strength one you know is planning to go into of the joint. About 3/4 inch of the upper engineering just for the money, tell end of the wire is also bent at a 90- them to forget it. They'll probably fail. WPT PUBLICATIONS degree angle, as is about Ys inch of the The successful people I've known have 979 Young Street, Suite E very tip of the wire, to provide a resting been those who are in electronics be- Woodburn, OR 97071 place for the dragonfly, which is held on cause they love it. They're simply prac- with double -sided adhesive -backed ticing their hobby! (503) 981 -5159 foam rubber (see Fig. 6). Four rubber CIRCLE 19 ON FREE INFORMATION CARD adhesive -backed feet are then placed in the corners on the foil side of the board, and some protective insulation is placed over the high -voltage traces to complete the project. Now simply pop a battery into the holder, press S1, and watch the wings flap. You can adjust the rate at which the wings flap by varying R7. The dragonfly should come to life right away. If you have any problems, go back and check your work for proper parts placement, poor solder joints, etc. Your Ticket To Once you have the project working, the Electronic Dragonfly is ready to Honoring hover over your desk mantle or and a friend or entertain your friends. Perhaps the best SUCCESS Over 28,000 technicians have gained admit- thing to do is help a young loved one has hobbyist tance worldwide as certified professionals. build the project, or build it yourself and never been easier. Let your ticket start opening doors for you. give it to a youngster. ISCET offers Journeyman certification in Consumer Electronics, Industrial, Medical, 1- 800 - 242 -8721 Communications, Radar, Computer and Video. For more information, contact the International Society of Certified Electro- nics Technicians, 2708 West Berry Street. Fort Worth, TX 76109; 1817) 921 -9101. The American Heart Name Association Memorial Program. Address An Investment in Life. City State Zip American Heart Send material about ISCET and Association becoming certified. Send one "Study Guide for the Associate Level CET Test." En- This space provided as a public service. Lclosed is$10 (inc. postage).

www.americanradiohistory.comAmericanRadioHistory.Com material commonly listened I also pulled the type -20 ANTIQUE RADIO PROJECTION TV to on broadcast TV volume -control tube, since (Continued from page 73) (Continued from page 71) Aside from the unusual its filament power source mounting arrangement of (that jumbled -up pickup using such a high -gain re- the speakers referred to POWERING UP THE coil) was in question, reflective screen, pictures earlier, there is little that we THEREMIN placing it with a small

tend to look somewhat could take issue with con- Next, I decided to try ap- penlight bulb that had volt- washed out when black cerning the design and plying power to the age and current ratings level retention is less than performance of this excel- theremin unit, now re- similar to those of the tube perfect. There was no such lent large screen front - moved from its cabinet. filament. That bulb was clip- problem with this set. projection TV system. If you Since the power supply was ped directly across the coil's Color quality was very are about to set up a home easy to isolate from the output leads and would good and there was not audio /video theater, or theremin chassis, requiring give an indication of the the slightest amount of even if you already own only disconnection of a 9- presence of filament overscan. With this system, one and feel that you are wire power cable from its power. you will see the entire pic- ready for a bigger, brighter terminal strip, the first tests The voltages at all check- ture, right out to its extreme picture than you currently were conducted on the points agreed closely with edges. have, you should check out supply alone. RCA's published values for a Pulsar didn't skimp in the the Pulsar TVP 2000. In light Had the power supply power supply under load. design of their TV -tuner sec- of its features and perfor- contained electrolytic filter However, there wasn't a tion either. There was hardly mance that this set offers, capacitors, which can be glimmer of light in the pen- any video noise (or snow) we feel that even at destroyed by sudden ap- light bulb filament. I knew visible, and colors remained $4295.00, it's priced within plication of power after that the 420 -kHz volume - accurate when APEL input reason, too. long periods of disuse, I control oscillator was oper- the equivalent of a fringe For more information on would have used a variable ating (a necessary area signal (of 100 micro- the Pulsar TVP 2000 "Pro- transformer to bring up the condition for power to be volt/meter intensity) to the digy" projection TV monitor/ line voltage slowly. However, available at the pickup coil) antenna input. receiver, contact the man- electrolytics weren't com- because I could hear its The audio output jacks ufacturer directly, or circle mon in the era (late 1920's) second harmonic at about delivered 0.28 volts of au- no. 120 on the Free Infor- when this unit was built- 840 kHz on a transistor dio with only 0.15% mation Card. and the power supply radio. distortion, and distortion didn't contain any. decreased to an insignifi- Accordingly, I just crossed UNTIL NEXT TIME It's quite obvious that the cant .09% at lower voltage - FUN SOFTWARE my fingers and flipped the coil is going to need some output levels. Frequency re- (Continued from page 83) switch -having connected sponse of the audio section a DC voltmeter so that I work before the theremin was excellent, extending playing games with 3 -D could monitor power -sup- can be made to operate from 20 Hz to 16 kHz. Tone graphics and enhanced ply output. The meter properly, and I hope to be controls provided the usual sound (IBM, Amiga: $49.95). almost immediately regis- able to solve that problem range of 10 dB or so of bass MicroProse packs in the tered an appropriate value, in time for the next column. and treble boost or cut at action with Gunship 2000, and there was no sign or See you then, but in the 100 Hz and 10,000 Hz, re- the first multicopter simula- smell of smoke. Continuing meantime don't forget spectively. As for the MTS - tion. Topographical 3 -D to make voltage tests as about our contest! Tell us decoder section, it pro- graphics, seven types of outlined in the RCA service how you catalog and dis-

vided adequate stereo helicopters and hundreds notes, I found all values play your radios, how other separation of between 18.8 of missions in the Persian within specifications for the members of your family re- and 19.5 dB (depending on Gulf and Central Europe unloaded power supply. late to them, and what which channel was being are featured (IBM). Another Now it was time for a tactics (if any) were needed measured) at maximum au- new MicroProse release is round of voltage checks to gain the support of other dio- modulation levels, and Legend Entertainment's with the theremin chassis members of your family. the separation remained Timequest, a time -travel ac- connected. In preparation Photos are welcome! All

virtually the same at lower tion adventure spanning for that, I hooked up the entries must be received modulation levels. three thousand years, from power cable to its terminal before the Labor Day holi- As for the SAP (secondary Stonehenge to Hitler (IBM: strip on the power supply day, and the eight judged audio program) mode of $ 59.95). and shorted out the speak- most interesting will receive the MTS decoder, it pro- Sierra (recently merged er connection. The latter reprint copies of 100 Radio vided only minimal with Borlund) has an- move applied voltage to Hookups, the same 1924 frequency response extend- nounced Space Quest IV- the plate of the power - Gernsback publication sent ing from about 250 Hz to 4 Roger Wilco and the Time output tube under close to to the winners of our there - kHz. Monophonic frequency Rippers, a topsy-turvy se- operating conditions, but min contest. Write c/o response from the MTS de- quel through time and avoided the distraction of Antique Radio, Popular coder circuitry extended to space. It comes on six high - having the speaker emit- Electronics, 500 -B Bi -Coun- around 3.55 kHz, or enough density diskettes (IBM: ting various unearthly ty Blvd., Farmingdale, NY for most dialogue program $59.95). sounds during testing. 11735.

94 www.americanradiohistory.comAmericanRadioHistory.Com ELECTRONICS MARKET PLACE

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the same. Mini Disc will support SCMS, SONY'S MINI DISC the Serial Copy Management System (Continued from page 40) that allows copies of CD's to be made, but not copies of copies. And even markable- especially since such a more important, the same equipment strong base of incompatible equip- that is used to manufacture CD's can ment stood fighting against obsoles- also be used to make MD's. (Even cence. Sony's Walkman, introduced in though the Mini Disc is not compatible 1979, dramatically changed the way with compact discs, a Mini Disc player we listen to music. At the time of its intro- can read both magneto -optical discs duction, however, it seemed nothing and manufactured read-only optical more than a neat gimmick. discs.) Audio quality is another important Although Sony says they are not try- The Mini Disc is only 2.5 inches (2.7 not necessarily the ing to replace anything with Mini Disc, including the caddy). Yet it holds as much consideration, but there are other items with which it will music-74 minutes -as does a standard most important-don't forget that the have to compete for consumer dollars. CD. aurally inferior audio cassette far out- There's the personal cassette stereo, of sells the CD, mainly because of its con- course, which should remain a viable required than in MD players. venience. At its announcement, Sony format for some time. There's also the The shock resistance, small size, and demonstrated a working MD pro- DCC player slated for introduction in high quality that are promised by Mini totype, but it was hard to get a feel for 1992 -at or before the time when the Disc should also be available from its performance; only a 20 second or so Mini Disc is due. DCC. Fast random access -the ability demonstration was given in a crowded The portable CD player could also to get to any track on a disc in less than hotel ballroom, and no NB comparison put up a reasonable fight. The main a second -won't, although DCC prom- was made with other formats. complaint now is that they are not ises much faster (and more accurate) Regardless of what we say here, how- shock resistant. But there's no tech- access than standard cassettes, and ever, Mini Disc seems destined to come nological reason that a data buffer CD -like programmability. and compete. Sony will test the waters couldn't give standard CD players Will record companies support Mini with the Mini Disc in late 1992. However, "shock -proof" performance -although Disc? At least one will, since Sony owns based on what we've seen thus far, considerably more memory would be CBS Records. We expect others to do we're not ready to dive in just yet.

www.americanradiohistory.comAmericanRadioHistory.Com Never before has so much The professional discussions seen on professional information on the art the TV screen in your home reveals how of detecting and eliminating to detect and disable wiretaps, midget electronic snooping devices -and CUUNtE radio -frequency transmitters, and other how to defend against experienced bugs, plus when to use disinformation to information thieves -been placed stci4oIs°"" confuse the unwanted listener, and the in one VHS video. If you are a technique of voice scrambling telephone Fortune 500 CEO, an executive in communications. In fact, do you know 8116611,16 how to look for a bug, where to look for a any hi -tech industry, or a novice COMPUTER seeking entry into an honorable, fi bug, and what to do when you find it? tpVE5VO41t1 Bugs of a very small size are easy to rewarding field of work in ll$TÉNH6 r countersurveillance, you must 1 build and they can be placed quickly in a view this video presentation again matter of seconds, in any object or room. and again. Today you may have used a telephone handset that was bugged. It probably contained three bugs. One was a phony Wake up! You may be the victim of bug to fool you into believing you found a stolen words -precious ideas that would bug and secured the telephone. The sec- have made you very wealthy! Yes, profes- ond bug placates the investigator when sionals, even rank amateurs, may be lis- he finds the real thing! And the third bug tening to your most private con- is found only by the professional, who versations. 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