4878 Simple VCR Repairs that YOU Can Do! II; Popular Electröriics Build The Sonic Defender An effective, non -lethal deterrent to those who wish you harm. It protects you and your property with a blast of high- intensity sou nd Build The "Slot- Machine" Bank See your pocket change pile up with this fascinating electronic bank Weather -Alert Decoder It keeps a "weather eye" peeled for National Weather Service emergency alerts All About Meters Learn how analog and digital meters work, and how to design circuits to measure voltage, current, and resistance The Birth of the claimed that he got the idea for the from a gas flame; Fleming l GERNSBACK thought that story was just hot air! _s i ._L_- r=:i 5 _LiRÌ'lMq9t;i-{0 'EE?2 a 3 NEW ,ROBERT C'AHM $2 95 U.S. FactCards F;i*'At-:i'

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www.americanradiohistory.comAmericanRadioHistory.Com MAY 1991, VOLUME 8, NO. 5

G. Popular Electronics THE MAGAZINE FOR THE ELECTRONICS ACTIVIST!

CONSTRUCTION ARTICLES THE SONIC DEFENDER Phil Salas 25 Protect yourself and your property with a blast of high -intensity sound BUILD THE "SLOT MACHINE" ELECTRONIC BANK Marc Spiwak and John Yacono 35 Watch your pocket change add up with this fun -to- build, fun -to -use electronic bank WEATHER ALERT DECODER Keith Rawlinson 62 You'll never miss another severe-storm warning with this weather -alert detection device

FEATURE ARTICLES ALL ABOUT METERS Stephen J. Bigelow 28 With a little know -how, you can design and build your own metering circuits THE BIRTH OF THE VACUUM TUBE James P Ryback 40 A look at the device that made world -wide radio communications practical, and at the men who battled to control it SIMPLE VCR REPAIRS THAT YOU CAN DO Sam Allen 57 This guide to basic VCR repairs can save you a bundle.

PRODUCT REVIEWS GIZMO 45 Including: Sharp Vision XV-100 Projection -TV System, Fosgate Surround Sound Processor, and more HANDS -ON REPORT 65 Laser PC4 Portable Computer PRODUCT TEST REPORT Len Feldman 67 Toshiba M -441 VCR

COLUMNS THINK TANK John Yacono 20 Multiplexing with counters ANTIQUE RADIO Marc Ellis 69 Operating the Cunningham Special COMPUTER BITS Jeff Holtzman 72 Hypertext: hype or text? CIRCUIT CIRCUS Charles D. Rakes 74 Test instruments for your bench HAM RADIO Joseph J. Carr 78 An audio -noise blanker DX LISTENING Don Jensen 80 Reader mail SCANNER SCENE Marc Saxon 82 A high -tech turbo scanner DEPARTMENTS EDITORIAL Carl Laron 2 LETTERS 3 ELECTRONICS LIBRARY 4 NEW PRODUCTS 12 ADVERTISER'S INDEX 92

Popular Electronics (ISSN 1042 -170X) Published monthly by Gernsback Publications, Inc., 500 -B 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 onty, International Postal Money Order, or check drawn on a U.S. bank. U.S. single copy price $2.95. 4) 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 Gemsback Publications. Printed in U.S.A.

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As a service to readers, Popular Electronics oublishes 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 EHE. CET Editor -in -Chief und Publisher EDITORIAL DEPARTMENT Carl Laron Editor Robert A. Young Associate Editor John J. Yacono Associate Editor Byron G. Wels, K2AVB Associate Editor Teri Scaduto Assistant Editor A SERIOUS PROBLEM, Kathy Terenzi Editorial Assistant AND A "SOUND" SOLUTION Marc Spiwak Ask most people about what they think are the most serious Editorial Associate Fred Blechman problems facing society today, and crime is sure to be near Joseph J. Carr, K4IPV the top. That's not surprising, considering that many of us Marc Ellis Len Feldman have, or know someone who has been a victim of some type Jeffrey K. Holtzman of criminal activity. Don Jensen Charles D. Rakes Marc Saxon Crime knows no social, economic, or geographic boundaries. Contributing Editors It can strike the richest and the poorest among us. It is PRODUCTION DEPARTMENT common in cities, but far from unknown in rural areas. Crime Ruby M. Yee Production Director can strike anyone at any time. Karen S. Brown Production Manager Marcella Amoroso This month, Popular Electronics presents the Sonic Production Assistant Defender, a device that can help keep you from joining the Janice Box ever-growing legion of crime victims. A purely defensive Editorial Production weapon, it uses blasts of painful, high- intensity sound to deter ART DEPARTMENT Andre Duzant those with wrong -doing on their mind. Further, the sound is so Art Director loud that it is sure to attract the attention of others who may be Injae Lee in the vicinity. illustrator Russell C. Truelson Illustrator The unit is compact enough to fit into a purse or jacket pocket. Jacqueline R Cheeseboro It also features a wrist strap that makes the unit easier to Circulation Director carry, and harder to wrest away from its owner. Michele Tordillo P-E Bookstore We wish that there was no need for projects like the Sonic BUSINESS AND EDITORIAL OFFICES Defender. Unfortunately, crime is a very real part of modern Gernsback Publications, Inc. life. We hope, however, that the Sonic Defender can help keep 500 -B Bi- County Blvd. Farmingdale, NY 11735 it from becoming a part of your life.

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

2

www.americanradiohistory.comAmericanRadioHistory.Com CHEMICAL CAUTION

I want to warn other readers that LETTERS one of the chemicals listed in Table 1 of the article "Build a Lava Lamp" (Popular Elec- tronics, March 1991) is quite dangerous. Nitrobenzene is deadly through inhalation, skin handy gadget to have. The lot of use out of it for many bad cable. Once it was re- contact, or ingestion, and the point you've made is a valid years. Many thanks to Steven placed, everything worked like a article does not make that evi- one: A carriage return is Stronczek for a great design, charm. dent. character 13, not 12. Luckily, the and to Popular Electronics for Your suggestion undoubtedly we that it S.D. mistake was made in discussing publishing it. I hope you have works. But don't think Powell River, BC, Canada DOS's idiosyncrasies and some similar articles in store, should be up to the user to find to You are correct. However, the shouldn't affect the operation of featuring handy devices, for a graceful way compensate chemicals listed in that Table the unit or the software. Still and people with home electronics for a program's shortcomings. It were only candidates for further all, f like to be accurate. Thanks shops. I'll be looking for them. is, however, often necessary- for your correction. Chris F. O'Brian investigation by the author and W.P.H. As far as recommending a none, other than benzyl alcohol, Richland, WA was either pursued or used in Triac is concerned, it really de- VAN DE GRAAFF the project. Based on the infor- pends on the current SMART LABEL INACCURACIES mation we have received from requirements of the AC device PRINTER rec- you and other readers since in question. Further, I can't "The Wimshurst Machine" publication, we strongly cau- ommend a particular flip -flop De- I use the Seiko Smart Label (Popular Electronics, that the use of because any flip -flop configured tion and urge Printer that was featured in cember 1990) contains some be avoided. to toggle will do. -John J. nitrobenzene - Gizmo (Popular Electronics, inaccuracies in its description of Editor Yacono January 1991) as an integral the operation of the Van de part of the word -processing as- Graaff generator. 3 x 3 ALARM SUPERB SUPER- pects of my medical practice. The Van de Graaff generator ALTERATION SIMPLE FREQUENCY A solution to the occasional does not produce static elec- COUNTER (and infrequent) error status tricity by friction. It works with the reviewer en- induction, just as the Wimshurst I was glad to see my article problems that machine does. Unlike the figure "3 x 3 Alarm" in the February I am writing concerning my countered is to run the Label in the the combs of the issue of Popular Electronics. I Super -Simple Frequency Coun- TSR program and a session of article, in Van de Graaff do not touch the have noticed one small error in ter, which I built from the your favorite word processor the parts placement diagram on instructions in the January 1991 a DeskView window. If the pro- belt. They are a few millimeters page 99. The outline of the issue of Popular Electronics, gram crashes, you can simply away. Friction does generate a in the SCR is reversed 180 °. The flat using the set of parts offered by close the window and be on small positive charge side of the outline should be SHF Components. your way. lower pulley and, by induction, toward S1. The lead markings When assembly was corn - That scheme also allows you produces a negative charge in a the lower comb. Because the are correct, so the readers pleted, I plugged in the to do your word processing as shouldn't have too much trouble and turned it on-and imme- separate window or session. teeth of the comb are pointed, a with it. diately got a "0" on the meter, The two programs can be "con- corona discharge sprays elec- moving belt. At Richard Hampton indicating that it was working. I nected" either through trons onto the then connected it to my fre- DeskView's cut -and-paste facili- the top, the electrons jump to quency generator and my AC- ty or via an intermediate file. the teeth of the upper comb and LUCKY 13 powered frequency counter, Keyboard macros can be used are deposited on the dome. which was showing about 8500 to automate and speed up the Electrons repel each other and Because end up on the outer surface of I loved "The Port Master Home - Hz. The Super -Simple Frequen- label creation process. Automation System" (Popular cy Counter almost immediately of DeskView's multitasking the dome, leaving the inner sur- Electronics, February 1991), displayed the exact same value nature, the label printer usually face neutral -i.e., a Faraday my cage. The limit to the charge on but I noticed an error that a as my AC- powered frequency prints simultaneously with the dome is governed by corona novice PC user might not counter. I checked its response HP DeskJet, decreasing the "latch" onto. On page 61, it said over the whole range of my time one might have to wait to leakage. the to send an ASCII number 12 for frequency counter, and it was collate the envelope, label, and The source of electrons is itself. That is why the a carriage return. It should read right -on at all frequencies. I letter. Earth when the an ASCII number 13. didn't even have to tweak the Adding the Seiko printer to generator works best Here's a question for you: Do calibration pot! my word -processing system has base is connected to a water pipe. A positive charge can be you have any device types rec- Since I wanted to use the decreased the office's man- ommended for either the Triacs Super -Simple Frequency coun- power needs by about 30 sprayed onto the belt if a of charges is (for AC control) or the D flip - ter as a portable device, I minutes per day, paying back positive supply flop? mounted it in a Radio Shack the cost of the printer in well attached to the lower comb Thanks for another great/sim- #270 -627 Experimenter Box, under three months. through a battery or a power which is a nice handy size and supply. ple project. C.C.H., M.D. encloses all the components I hope this will help dispel J.C. Hood River, OR without crowding. It also costs some of the myths that have Vancouver, BC, Canada only S1.95 and has a nice alu- We, too, were generally im- surrounded the explanation of We're glad you liked the minum front panel. pressed with Seiko's Smart the Van de Graaff generator. we G.R.M. Port Master so much. Even I am really delighted with the Label Printer. The problems Meriden, CT though it easy to build, its a device, and am sure I will get a encountered were caused by a

www.americanradiohistory.comAmericanRadioHistory.Com ELECTRONICS LIBRARY

Even those of you who enjoy rebuild radios, and includes in- reading his Ham Radio column formation on power -supply IVÜcrodevices in Popular Electronics might circuits, capacitors and other be unaware that Joe Carr's ex- components, RF and IF ampli- pertise extends to antique fiers, and amplitude -modulation radios as well. In this book, he detectors. In addition, the spe- Old Time puts to use his years of experi- cific types of test equipment ence in radio repair to teach used for radio repair are dis- old- time -radio enthusiasts how cussed. The book includes a Radios! to restore and repair their finds. complete radio troubleshooting He provides a glimpse at the course, a / Restoration early history of radio receivers color -code chart to help readers from the first 19th -century ex- identify parts, and vacuum -tube and Repair periments to superheterodyne pinout diagrams that are often sets, before going into more missing from schematics. by Joseph J. Carr detail about vacuum -tube radi- Old Time Radios! Restoration Power Up! is free upon re- os. To give readers of all levels and Repair costs $16.95 and is quest from JDR Microdevices, of experience a firm background published by TAB Books Inc., 2233 Branham Lane, San Jose, upon which to base their repair Blue Ridge Summit, PA CA 95124; Tel: 480-559 -1200 or work, a full chapter is devoted to 17294-0850; Tel. 800 - 538 -5000; Fax: explaining vacuum -tube tech- 1- 800-233 -1128. 408 -559 -0250. nology. In addition to tube CIRCLE 98 ON FREE CIRCLE 80 ON FREE INFORMATION CARD technology, the author explains INFORMATION CARD transistor theory and practice POWER UP! AN INTRODUCTION TO from JDR Microdevices AMATEUR CRI Time COMMUNICATIONS Filled with products to help SATELLITES computer enthusiasts maximize by Alan Pickard 'Cs: the speed and efficiency of their REST RATION and REPAIR equipment, this 100 -page cata- Despite the large number of log features color -coded communications satellites cur- sections to help customers rently orbiting the earth, and the quickly locate products. New large role they play in our infor- products highlighted in the cata- mation -based society, most log include JDR's Front Panel - people-even those who have a combination bus extender and and use satellite television sys- instruction execution detector tems -have no understanding designed for hardware and soft- of satellite technology. This ware debugging -and the book explains the complex Breadboard -On -A -Card Series technology behind amateur - with Decode for faster and easi- communications satellites, in- er prototyping. Other new items cluding operating frequency, life include an accelerator card with expectancy, and orbital paths. It a high -speed 28 -MHz 68030 also shows how they can be CPU, a 486 motherboard, tracked and their signals re- Amiga products, and an ex- ceived with relatively panded software line that inexpensive equipment that features many software prod- most hobbyists can afford. That ucts for Windows. The catalog equipment can be hooked up to also includes technical informa- home computers, such as IBM - tion for computer enthusiasts, PC compatibles, for the decod- that can be used on many of the such as "Derick's High Tech ing of received signals. Several highly collectible "old- time" radi- Corner " -a column that pro- currently available systems are os manufactured in the 1950's vides PC- technology described, and software is dis- and 1960's. The book provides information and purchasing cussed. The results of decoding detailed instructions and sche- tips -and numerous "Tech Tips' signals that contain information matics needed to repair and that are scattered throughout. such as telemetry data and

4

www.americanradiohistory.comAmericanRadioHistory.Com weather pictures are demon- Box f9100, Washington, DC chrome -plated steel. The illus- variety of surfaces, and gives strated. Although individuals 20036. trated 8 -page bulletin provides their resistance to various can't launch their own satellites, CIRCLE 81 ON FREE detailed information on types of chemicals and proper installa- INFORMATION CARD they can achieve fun and re- adhesives, general guidelines tion procedures. warding results from received for surface preparation, and Selection and Use of Panduit /Ap- signals, either in the form of SELECTION AND USE short listings of applications and Adhesive Mounts (Technical telemetry data or picture infor- OF PANDUIT markets. A table includes com- plication Data Sheet TADS - mation. ADHESIVE MOUNTS plete listings of the company's WA-14B) is free upon request An introduction to Amateur from Panduit Electrical Corp. mounts and provides dimen- from Panduit Electrical Corp., Communications Satellites is sions, service temperature Product Manager, Wiring Ac- available for $7.95 (including This technical /application data ranges, adhesive type, max- cessories, 17301 Ridgeland shipping and handling) from sheet aids in the selection and imum static loads, and which Avenue, Tinley Park, IL Electronics Technology Today use of Panduit's adhesive cable ties (if any) are used with 60477 -0981; Tel: Inc., P.O. Box 240, Massapequa mounts for and cable. the mounts. An application 1 -800- 777 -3300, ext. 7346. Park, NY 11762 -0240. Those mounts are available in chart helps users select the CIRCLE 82 ON FREE CIRCLE 97 ON FREE nylon, PVC, aluminum, and right type of adhesive for a INFORMATION CARD INFORMATION CARD

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4 1CCMHz, 4kw x , Ch v 14w s 4cn. VC -6145 4,695.00 Warranty Electronics Group 1001ASS(25MS.s on channel: 5 :mullaneouslvl. 2ke 2_h S 3Y Model 40MSis, 100MHr, 4kw e ICh., 2kw e 2ch, VC-6045 S 3,049.00 Gone are the days when cars 20MS/s, 50M1-1Z, 2kw it 2cn. VC -6025 S 2,295.00 This sans provides many new functions such as CRT ' Readout, Cursor measurements (5- 1085/1065/665). Autdranging and were simply equipped with AM 20M&s, SOMHZ, 21sw a 2cn. VC -6024 s 2,049.00 Frequency Ctr (54085), Sweeptime Trigger _ock using a 6 -inch CRT. You don't feel the 20MS/s, 20MHz, 2kw r 2cn. VC 6023 S 1,749.00 radios. Today's vehicles are like- WmpaCmeSS In Term801118rformance and operation. RsOS from Hkachi feature such functions as roll mode, averaging, ova memory, emcothing, 'Inlerpalatbn.pretrigg re9. ly to have AM/FM stereo cursor musuremanm, plotter intedaw, and RS -23W interface. WM the comfort of analog and the power of dMer. V -660 60MHz Dual Trace $1,195 V-212 Hitachi Portable Scopes V-665 66OMHz Dual Tracew/Cursor $1,345 receivers with built -in cassette e' $1,425 DC to 50MHz, 2- Channel, DC offset V-1060 100MHz Dual Trace s el $435 $1,695 o Q 4' 4, II, pc ,o function, Alternate magnifier function V -1065 100MHz Dual Trace wiCursor decks -and an increasing t% 20M, oar channel V-525 CRT Readout, Cursor Meas. $1,025 V -1085 100MHz Quad Trace w/Cursor $2,045 number of vehicles also have V.523 Delayed Sweep $pas V -1100A 100MHz Quad Trace w/CursOr $2,295 5-1150 150MH2 Quad Trace W/QufSOr í2,775 CD players, extra speakers, -`Yá22 IOMHi Dual Trace 5796 V522 east Mode E895 high -tech security systems, cel- 20MHz Elenco Oscilloscope FREE DMM Elenco 35MHz Dual Trace to 50MHz $495 with purchase of Good lular mobile phones, and CB - $375 MO -1252 FE ANY SCOPE - - - High hmibanee6.CRT 48 brochure r F;v¡; ` MO -1251 radios. This -page Duel Trace too Sensitivity Component Tester SCOPE PROBES WV Acceleration Voltage poses and clearly answers the .6'CRT tom Rw Time P- 165MHZ. la. lOx S19.95 X -Y Operation 2 Aso that auto -electronic e X -Y Operation questions TV Sync P-2 100MFtZ, lx. lox S23.95 Delayed Triggering Sweep Includes 2P-1 Probes consumers are most likely to 2 p -I Probes All scopes include probes, schematics, operators manual, and 3 year (2 yrs for Elenco scopes) world wide warranty on parts & labor. Many accessories available 10r all ask. It explains what makes a Hitachi scopes. Call or write for complete specaications on these and many other fine oscilloscopes. good car stereo system, how to WE NOW Tm. OAS 1/2 10 Function Digital Capacitance Meter Digital LCR Meter

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www.americanradiohistory.comAmericanRadioHistory.Com COMMUNICATIONS AOR Scanners. Great Performance. Great Service. Great Value. Free Freight 25-Day Money -Back Guarantee Toll -Free Service and Support No Credit Card Surcharge One Year Warranty AR950 $239

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6 CIRCLE 16 ON FREE INFORMATION CARD

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400 Channels. 100KHz to 2036MHz. Standard Features: Extremely compact size. Continuous coverage Attenuation Programmable by Channel. Manual tuning knob. Tuning increments down to 50Hz. AM, FM, wide band FM, LSB, USB, CW modes. Backlighted LCD display. 2016 Channels. 1 MHz to 1500 MHz 4 Scan and Search Banks, Lockout in Search. 4 Priority Channels. Standard Features RS232 control through DB25 connector. Continuous coverage Delay, Hold Features. AM, FM, wide band FM, & BFO for SSB, CW. 15 band pass filters, GaAsFET RF amp. 64 Scan Banks. Sleep and Alarm Features. 16 Search Banks. AC adaptor /charger. DC power cord. RS232 port built in. Telescopic Antenna. Antenna, Mntng Brckt. Includes AC /DC pwr crd. Options: Year Limited Warranty. One Earphone. EP200 $2.00 Options: External Speaker. Mobile Mount. MS190 $19.50 Earphone. EP200 $2.00 Extended Warranty. 2/3 yrs. $65/75 External Speaker. Mobile M ount. MS190 $19.50 Mobile Mounting Bracket. MM1 $14.90 Extended Warranty. 2/3 y rs. $65/75 RS232 Control Package SCS3 $295.00 Mobile Mounting Bracket. MM1 $14.90 (software & cable) offers spectrum display RS232 Control Package SCS2 $295.00 and database. & spectrum display (software cable) offers Specifications: and database. Coverage: 100KHz - 2036MHz Specifications: Sensitivity: .35uV NFM, 1.0uV WFM, Coverage: 1 MHz - 1500MHz 1.0AM /SSB /CW Sensitivity: .35uV NFM, 1.0uV WFM, Speed: 20 ch /sec. scan. 20ch /sec. search 1.0AM /SSB /CW IF: 736.23, (352.23) (198.63) 45.0275, 455KHz Speed: 38 ch /sec. scan. 38 ch /sec. search Increments: 50Hz and greater IF: 750.00, 45.0275, 5.5MHz 455KHz Selectivity: 2.4Khz / -6db (SSB) 12KHz / -6db Increments: 5,12,5,25 KHz (NFM /AM) Audio: 1.2 Watts at 4 ohms Audio: 1.2 Watts at 4 ohms Power: Input 13.8 V. DC 300mA Power: Input 13.8 V. DC 500mA Antenna: BNC Antenna: BNC Display: LCD, backlighted. Display: LCD Dimensions: 2 1/4H x 5 5/8W x 6 1/2D Wt. l lb. Dimensions: 31 /7H x 5 2/5W x 7 7/8D Wt. 21b l0oz. To Order Call i 800 445 7717

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CIRCLE 16 ON FREE INFORMATION CARD 7

www.americanradiohistory.comAmericanRadioHistory.Com mometers, data -acquisition and power radiators. The book also recording instruments, and dig- offers helpful examples of both ital controllers. Some of the solid -state and vacuum -tube RF products featured include full power amplifiers and presents specifications while others can full coverage of RF combiner be supplemented with more de- systems. tailed literature. The catalog is The individual elements of RF indexed by general product type transmission systems are de- on the contents page and by scribed, and their interrelation is model numbers on the numer- explained. Complex theory and ical index page to help readers math are included only when easily locate particular products. essential for understanding the The Catalog of Products is basic concepts. Special empha- free upon request from Beck- sis is placed on television and man Industrial Corporation, radio hardware, because those 3883 Ruffin Road, San Diego, applications provide examples CA 92123 -1898; Tel: that can be extended to other 619 -495-3200. uses. CIRCLE 83 ON FREE Radio Frequency Transmis- INFORMATION CARD sion Systems: Design and Operation costs $49.50 in hard- RADIO FREQUENCY cover and is published by TRANSMISSION McGraw-Hill Book Company, 11 SYSTEMS: Design and West 19th Street, New York, NY Operation 10011; Tel. 1- 800-2- MCGRAW. CIRCLE 96 ON FREE by Jerry C. Whitaker INFORMATION CARD

Radio -frequency (RF) transmis- sion systems are increasingly WORDPERFECT PC being used in a wide range of TUTOR applications. by Marianne B. Fox, Lawrence Written for technicians and C. Metzelaar, and Susan Hafer engineers who work with the design, installation, operation, The combined book/diskette CIRCLE 6 ON FREE INFORMATION CARD or maintenance of RF transmis- self- instruction package pro- vides an on- screen guide to learning WordPerfect 5.1. The USING MACDRAW and how to measure visual ele- user simply inserts the tutorial by Marvin Bryan ments to scale. Special tips disk, types a command, and show how to work with multiple they are ready to begin the One of the most popular pro- design layers, colors, shadows, interactive learning process. grams available for the and typefaces. The book also The lesson files on the disk Macintosh computer, MacDraw offers detailed information on contain examples and exercises is an object -based drawing pro- MacDraw's commercial applica- that are clearly explained in the gram that can be used to create tions. text. The package is designed a wide variety of projects, in- Using MacDraw costs $24.95 to quickly teach readers all the cluding professional artwork and is published by Que, 11711 essential WordPerfect pro- and illustrations, invitations and North College Avenue, Suite cedures, including how to announcements, brochures, 140, Carmel, IN 46032; Tel: format, create, and edit a docu- newsletters, floor plans and 1- 317 -573 -2500. ment. The tutorial shows users other architectural renderings, CIRCLE 94 ON FREE INFORMATION CARD how to operate their computers charts, graphs, training materi- with confidence, load and start als, and presentations. This WordPerfect on their PC's, for- book is designed to help read- CATALOG OF mat page layouts, and design ers ranging from absolute PRODUCTS documents. Advanced word - beginners to professional artists from Beckman Industrial sion equipment, this book processing skills are also fea- and experienced MacDraw Corporation provides a complete hands-on tured. Beginners are advised to users to get the most out of the guide that ranges from in -depth start with the first lesson and program. It offers information on Beckman's complete line of test discussions of individual com- progress through the tutorials in MacDraw's basics and tools instrumentation and industrial ponents to expert advice on order; more experienced Word- along with advanced concepts products is featured in this 40- keeping systems running Perfect Users can simply pick on designing, editing, and pro- page brochure. Included are smoothly. It provides detailed and choose those areas in duction. The book is filled with digital multimeters, component discussions of the latest de- which they need to brush up sample screens and practical testers, oscilloscopes, function velopments in power devices, their skills. examples that the reader can generators, universal and fre- including solid -state power de- WordPerfect PC Tutor book/ try out on a Macintosh comput- quency counters, vices, the Klystrode, the MSDC diskette package costs $39.95 er for a hands -on learning communication testers, digital , and the TWT. The use and is published by Que Corpo- experience. The book provides temperature meters and probes, of high -power coaxial transmis- ration, 11711 N. College Ave., step -by -step instructions on digital calibrators /indicators, sig- sion lines and waveguides is Suite 140, Carmel, IN 46032. how to handle how nal with perspective, conditioners, digital panel examined, along the de- CIRCLE 94 ON FREE to create pictures and captions, indicators, precision bench ther- sign and operation of high- INFORMATION CARD

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Weighing in at only 6.7 pounds CONTROL and CAPS LOCK keys TRI -PORT ADAPTER (with battery), the Tandy 2810 and their functions so that the CARD HD laptop is a full- function AT- keyboard layout resembles a compatible unit. The notebook - standard typewriter. Designed to eliminate PC- style computer features a 16- The Tandy 2810 HD note- adapter obsolescence as MHz 80C286 microprocessor, book -style computer is available changes are made to local - VGA graphics, an internal at Radio Shack Computer Cen- area- network configurations, 80286 20MB hard -disk drive with a 23- ters, Radio Shack Stores, and Telebytes Model 516 Tri -Port ms access speed, a 1.44MB dealers nationwide at a sug- Adapter is a 16 -bit Ethernet PC Notebook 31/2-inch floppy drive, a battery gested retail price of $2499. For adapter card that is compatible life of up to 31 hours, and an more information, contact Radio with either thick coax, thin coax, Computer AC adapter /charger. With 1MB Shack, Division of Tandy Corpo- or unshielded twisted pair and of standard memory, expanda- ration, 700 One Tandy Center, maintains complete compliance ble to 5MB, the 2810 HD can Fort Worth, TX 76102. for IEEE 803.2 10 Base 2, 10 run advanced business and CIRCLE 102 ON FREE Base 5, and 10 Base T. By INFORMATION CARD other software applications, and using the Tri -Port Adapter, the an optional Intel 287 XLT LAN manager does not need to coprocessor can be added for SOLDERING -IRON math -intensive applications. For STAND immediate, out -of- the -box com- IIIIIIIIIII1IIIIIIIIIIIIIIIII 1111 1111E1111111 puting, MS -DOS 4.01, Tandy's Featuring a metal base for add- ..161:. DeskMate 3.5 personal produc- ed stability, the Antex ST-5 from tivity software, and a TEMM M.M. Newman Corporation is a heavy -duty soldering -iron stand. Using a coil- spring holder and bezel for holding the iron, the ST -5 prevents heat sinking and helps protect the user from stock different adapter cards to burns. It comes with a choice of meet the needs of a growing two different bezels that leave network, and changing adapter the soldering tip unsupported to cards is no longer required. eliminate contact with the spring Contained on a half card, the holder. The stand also has a Tri -Port Adapter has three dif- phenolic tray, and a half -inch- ferent types of connectors. An thick wiping sponge with a cen- RJ -45 is used for 10 Base T ter hole for collecting dross. The networks using unshielded ST -5 is compatible with all pop- twisted pairs, while a BNC is ular soldering irons and used for thin coax. Thick coax conforms to DOD -STD -2000 -1B can be accommodated using a 4.11.3.3 requirements. transceiver attached to the stan- dard DIX (DB -15) connector. The desired connector port is activated by jumper placement on the model 516, which per- forms at 10 MB per second memory manager are factory - regardless of the wiring media installed on the hard drive. selected. Its use is compatible The 2810 HD, with built -in with the Novell NE -2000 adapt- ports for an external 101 -key er, and it features 16 -bit enhanced keyboard, and exter- architecture for use with PC/ nal VGA monitor, and other AT /386 -type computers. The peripherals, is designed to dou- 516 also features complete soft- ble as a desktop system. For ware compatibility with Novell portable use, the 1.7 x 12.2 x 10- Netware Advanced, ELS, The Antex ST-5 soldering -iron SFT, inch laptop has a full -size, fluo- and 286/386 NETBIOS. stand has a list price of $11.95. rescent backlit, black -on -white The Tri -Port Adapter includes For additional information, con- LCD screen with 640 x 480 VGA a boot ROM tact M.M. Newman Corporation, socket and optional graphics resolution and 16 or 32 ROM to allow its use in a 24 Tioga Way, P.O. Box 615, gray scales for improved con- diskless workstation. A DIP Marblehead, MA 01945; Tel: trast. Its 84 -key keyboard has switch is used to set the base 617 -631 -7100; Fax: true 101 -key emulation and Tan - addresses for the boot ROM 617 -631 -8887. dy's Key- Switch feature, which CIRCLE 103 ON FREE and the workstation. allows the user to switch the INFORMATION CARD The model 516 Tri -Port Adapt-

12

www.americanradiohistory.comAmericanRadioHistory.Com er costs $395 in single curacy, AC voltage response to SATELLITE ANTENNA ets provide strength and quantities, with quantity dis- 40 kHz, and a 0.5 -inch bright maintain dish accuracy. The counts available. For additional LCD readout. The instrument For areas where antenna size is model 6375 is packaged with a information, contact Telebyte measures current to 20 amps, restricted, Channel Master is quad leg -feed support and Technology Inc., LAN Sales De- volltage to 1200 VDC or 1000 offering a 71/2-foot quad mesh cover, which accepts standard partment, 270 East Pulaski VAC, and resistance to 20 satellite antenna. The Mirage C -band and Ku -band feed as- Road, Greenlawn, NY 11740; megohms. It also includes a VII Model 6375 is a four -piece semblies. The one -inch- Tel: 800 -835 -3298 or -test function. For precise antenna made with expanded diameter feed -leg support al- 516 -432 -3232; Fax: readings, the 2831A features and rolled Ku -mesh aluminum. lows cable to be routed through 516 -385 -8184 or 516 -385-7060. resolution to 0.1 mV, 0.1 amp, it for a neater appearance. CIRCLE 104 ON FREE and 0.1 ohm. An audible con- The standard -steel mount INFORMATION CARD tinuity -check feature sounds a comes out of the box ready for tone for resistances under 10 installation on a 31/2-inch O.D. BENCHTOP DIGITAL ohms. All functions are overload ground pole. Four high -grade MULTIMETER protected, with high- energy fus- locking bolts eliminate slippage ing on current ranges. in high winds. Specially formu- Especially well- suited for use The benchtop instrument lated paint protects the antenna where a large, easy -to -read dis- comes with test leads, spare and mount finish from scratches play is needed, B&K Precision's fuses, and a user's manual. For and corrosion, and the hard- Model 2831A digital multimeter user convenience, it features a ware is cadmium -dichromate can be used for education; engi- combination tilt handle /bail. Op- plated. neering-lab work; or for testing, tional accessories include a The Mirage VII Model 6375 analyzing, or repairing elec- test -probe assembly, a demod- satellite antenna -complete tronic equipment. The 31/2-digit ulator probe, a high -voltage with a feed cover, hardware, and The four antenna petals are DMM has 0.1% DC- voltage ac- probe, and temperature probes. detailed installation instruc- preassembled at the factory, for The model 2831A digital mul- tions -has a suggested retail easy installation. Mesh panel timeter has a suggested list price of $309. For further infor- inserts are preformed to the price of $295. For further infor- mation, contact Channel Master, parabolic curve and then at- mation, contact B &K- Precision, Division of Avnet, Inc., P.O. Box tached to 20 aluminum support 6470 West Cortland Street, Chi- 1416, Industrial Park Drive, ribs using self- tapping screws. cago, IL 60635; Tel: Smithfield, NC 27577; Tel: A 22 -gauge intermediate-cir - 312 -889 -1448. 919 -934 -9711. cular support ring and the CIRCLE 105 ON FREE CIRCLE 106 ON FREE INFORMATION CARD specially designed cradle brack- INFORMATION CARD

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www.americanradiohistory.comAmericanRadioHistory.Com THINK TANK

By John J. Yacono A new month is here probably familiar with inte- off). You should use tran- and with it a batch of grated- circuit counters of sistors or relays under the creative ideas from you one sort or other. The vast control of the 4017 to sup- readers. You've been most majority of them count in ply power to your display. Multiplexing generous with your corre- either binary or binary -co- But there are three other spondence this time out, ded decimal. What that pins on the chip that make With Counters thank you. As always, the means is their outputs rep- it much more useful and people submitting to this resent a number in binary applicable to more interest- month's column will receive or binary -coded decimal; ing circuits: First, there's a a copy of Think Tank ll. If each time such a chip re- clock -enable pin (denoted you've already received ceives a pulse, it increments Eft in Fig. 1). If that pin is held that fun and useful book, the value available frorn high, the counter ignores we'll find something else to the outputs. That more or the clock pulses and refuses send you. less restricts their use to sim- to advance. There's also a I would also like to hear ple counting -not exactly a reset pin (the one labeled from those of you that have vista of toe -curling applica- RsT) and, as its name implies, some ideas about what you tions. if it is pulsed high, it puts the would like to see in this On the other hand, the counter back to zero.

column. As you know, I like 4017 counts by ten. It has The last pin of interest is a tinkering with circuits myself, ten outputs assigned values carry output (coy,), which is so if you have a question 0 through 9. When first high while the chip is regarding a circuit that turned on, the 0 output (de- counting from 0 to 4, and you've come across, or per- noted oo) is high and the stays low as the count pro- haps you need general other nine outputs are low. ceeds from 5 to 9. That information on a topic just When a clock pulse is re- output is useful for cascad- ask it. I'm here to both help ceived (via the CLK pin), the ing 4017 chips (and little budding "circuiteers" Q0 and output goes low and the else as far as I can see). If present their circuits. Q, output goes high. On the you connect that output to next pulse, Q, goes low the clock input of another 116 115 114 113 112 111 110 In again and Q2 goes high. 4017, the first 4017 will count RST voo CLK ER COUT 0g 04 as Each time a pulse is re- in "ones" (0 through 9), and ceived, a high will appear the additional chip will 4017 at the next highest output. count in tens (10, 20, 30, 05 01 n2 06 07 03 It's as though the high gets etc.). Each chip you add on

11 13 14 15 16 12 17 18 pushed from one output to in that way will give the Fig. 1. The lowly looking 4017 decade counter can do much more the next with each clock circuit the ability to count to than you may think. It can divide by 1 -10, count, and even run a pulse. the next power of ten. multiplexed display. When the high is at Q9 But enough of counting, (the last or highest output), what else can one do? To THE HUMBLE 4017 the next pulse causes the help me answer that, take With that in mind, I'd like high to jump back to Q0 a look at the circuit in Fig. 2. to discuss a very inexpen- and the process starts That circuit will count from 0 sive chip and show you a again. to 4 and stop. To start the number of interesting uses The most obvious use for cycle again you have to it for (including one that's such a chip, besides just depress S1. If you connect not in the data books). It's counting from 0 to 9, is as a the clock -enable pin to a the 4017 decade counter light- chaser controller. If different output, the circuit (shown in Fig. 1). At first LED's or lamps were turned will count until it sets that glance, the application on (or off) in sequence by a output high and then halt. notes won't lead you to 4017, it would give a mar- That kind of circuit is believe that it's a powerful quee appearance to the useful for turning on some contender for breadboard lights. However, the chip it- number of devices one at a space. But after a short self cannot supply enough time. For example, let's say introduction, we'll see what current to power LED's or there's a long hall in your it can do when you take light bulbs (although it can home or perhaps an office the notes a step further. sink enough current if you building that leads to an Most of you readers are want nine LED's on and one exit door and you don't 20

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U1 CADMIUM "C" BATTERY 4017 Yuaaa1800C OZ Special purchase of new. rechargeable GO nickel-cad batteries. 12 volts. 1800 mAH. I, PRICE REDUCED ON 10 OR MORE. CATS HDNCB.0 ii \ 10 pieces for $42.50 ($4.25 each) 100 pieces for $375.00 ($3.75 each) POWER SUPPLIES Fig. 3. By connec ing pin 15 to the appropriate output, you can make a 4017 divide a series of clock pulses by a value from 1 to 12 Vdc 5 AMP 10. ACDC Electronics I 12N5 or equiv. Input: 100-240 Vac (wired for 115 Vac) - Output: 12 Vdc @ 5 apps. in Fig. 3. That circuit want to leave more than shown Open frame style. a® one light on at a time. You repeats a sequence over T X 4 3N4' X 3' high. Regulated. CATS PS -125 $37.50 each a ' ® -4. use the circuit in Fig. 2 and over. The output you can 24 Vdc 2.4 AMP to sequence the hall lights connect to the reset pin Power -One Inc. al-IC-24-2.4 Input: 115/230 Vac (wired amps. Open frame on and off one at a time. To determines the number of for 115 Vac). Output: 24 Vdc @ 2.4 style. 5.67 X 4.8T X 2.50' CSA listed. do that, you'll need a slow steps in the sequence. The CATS PS -2424 $30.00 each clock circuit to sequence circuit shown has 4 steps. SWITCHES steps last for the 4017's outputs at the The first three DIP P.C. PUSHBUTTON desired rate. You'll also the length of one clock ITT Sdtadow Digitaat Series SE Aar momentary pushbutton. cycle. The last step only S.P.D.T. need some optoisolator/ Mounts in 14 pin DIP configuration. 011ie.... couplers to control the Icsts until the chip resets Designed for low current switching applications. Grey keycap is 0.68' X 0.6T. lights. itself. That is a great circuit CAT S PB -28 $1.00 each 10 for $9.50 100 for $85.00 If you control the light at for performing digital fre- ROTARY BCD SWITCH the exit with output 04, the quency division. EECO I 2310 -02G - BCD 10 position next light down the hall with Let's say you need to rotary switch. DIP configuration fits in standard 8 pin I.C. socket. Right angle Q3, and so on, and place S1 measure the clock frequen- style. Screwdriver actuation. 0.47 cube. CATS RDIP -2 for at the far end of the hall cy of a really fast computer $1.75 each 10 for $16.00 100 $145.00 (away from the exit), some- c rcuit, but you've only got TOLL FREE ORDER LINES >: one heading for the exit just an old oscilloscope with too 1 -8.26 -5432 800 w«t,ata.rrrcCou ror'oNOÖVer has to press S1. The light narrow a bandwidth. Send CM4ROt; OROgHSto nearest him will come on, the computer pulses to the TERMS: Mininwn order$10.00.Shpping and handling the 48 continental U.S.A. 63.50 per order. AN others 4017 and connect the for then the next light, and so including AK, HI, PR or Canada must pay full shipping. on until the light nearest the scope to co and the AN orders deóvered in CALIFORNIA must include state sales tax (6 74 6 1? %, 7 %) .Quantities Limited exit is lit, and then the se- positive supply. Set the NO C.O.D. Prices subject to change without notice. to AC coup- quence will stop leaving scope's input Call or Write For Our the reset the light at the exit on. Every ling. Now connect FREE 60 Page Catalog time a light comes on, the input to o,. That divides the (Outside The U.S.A. Send $2.00 Postage) one prior to it goes out. computer pulse frequency ALL ELECTRONICS CORP. Another useful circuit is in half and the AC- coupling P.O. Box 567 Van Nuys, CA 91408 21 CIRCLE 5 ON FREE INFORMATION CARD

www.americanradiohistory.comAmericanRadioHistory.Com circuit in the scope should C C2 C3 C4 C5 be able to integrate the - _ ... wave form into something R1 more visible (although it may not be a square . N { N F wave). ó ó ó If that doesn't work try . R2 connecting the reset pin to one of the other outputs (it's . best to try them in order). If O O © O the duration of the nega- \:. \:. á\. . R3 tive pulse produced by the 4017 is too brief that's easy to fix: you need to tie more © a of the 4017's outputs to the . \\.

scope. Just make sure the . < R4 subscripts of the outputs connected to the scope are all less than half `-/ O Q O of the , \:. ,ti ti subscript of the output you R5 connect to the reset pin. To determine the frequency, n n n -, just multiply the frequency of the wave on your scope \:* \>, \;. \;A by 1 plus the subscript of Fig. 4. This is a multiplexed display of LED's. A particular LED can be lit by connecting its row the output connected to and column terminals to a power supply. the reset pin. And now for a real neat multiplexing don't worry: it's -n-nn- application: sequencing up just a big word for a simple CLOCK PULSES to 100 "multiplexed" devices concept. Multiplexing is a with only two chips. If you way of wiring a number of 14 CLK haven't heard the term devices together, but allows

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www.americanradiohistory.comAmericanRadioHistory.Com Earn Your B.S. Degree F1 D3 D2 01 in 1/2A 1N4740A 1N4739A 1N4738A 10V 9.1 V 8.2V ELECTRONICS 04 R1 TO CAR 1N4001 68052 or BATTERY R4 R3 1/2 15052 2205? 2"7052 SI COMPUTERS N.O. r LED4 E LED3 E LEO2 LEDI

Fig. 6. This simple car- battery voltage checker can be built small enough to be installed in your car's dashboard. them to work indepen- connected to inverters. dently. It reduces the When a divider output goes number of and corn - high, the inverter con- ponents you need in a nected to it grounds the circuit, as you'll see. Take a corresponding row output. look at the multiplexed LED's For example, if eo goes high, in Fig. 4. If we connect one the output of U5 -a goes low at Home of the column terminals grounding R.I. By Studying (marked C105) to a volt- If you connect that circuit Grantham College of Engineering, age supply, and one of the to the display circuit in Fig. now in our 41st year, is highly ex- row terminals (marked 4 and supply it with clock perienced in "distance education" - R1R5) to ground, then the pulses, it will turn on one teaching by correspondence- through LED in that row and column LED at a time. First the LED printed materials, computer materials, will light. connected to Ci and R1 is fax, and phone. In that way, we can turn active. U1 No commuting to class. Study at on any one LED from a then activates C205 in your own pace, while continuing on group of 25 by just using 10 turn, while U2 leaves R4 ac- your present job. Learn from easy -to- wires (5 row wires and 5 tive. Then U2 receives a understand but complete and thorough column wires). You could clock pulse from U1 so R2 lesson materials, with additional help use that technique to con- becomes active and U1 from our instructors. trol 100 LED's (or other gets reset, so the LED in Our Computer B.S. Degree Pro- 1, 2 is now lit. devices) by using only 20 column row gram includes courses in the BASIC, circuit U1 will wires, etc. For the sake of Integrated PASCAL, and C languages - as well light each LED in that row, brevity, the multiplex-control Assembly Language, MS DOS, CADD, then the next row, and so circuit (see Fig. 5) is shown and more. all the LED's have set up to control only 25 on until Our Electronics B.S. Degree Pro- been lit and the process devices. The two decade gram includes courses in Solid -State starts over again. You can dividers in the circuit are Circuit Analysis and Design, Control both set up for divide -by- use more of the outputs on Systems, Robotics, Analog/ Digital Com- the the two decade counters to five operation using munications, and more. technique as the cir- control up to 100 LED's pro- same An important part of being pre- cuit in Fig. 3. However, U2 vided that you connect the pared to move up is holding the right gets its clock pulses from reset pin to the proper out- college degree, and the absolutely neces- the 6/5 output of U1, so U1 put. sary part is knowing your field. sequences 04 through 04 And now for the mail! Grantham can help you both ways and then U2 gets its clock - to learn more and to earn your degree pulse. BATTERY-VOLTAGE Note that the outputs of INDICATOR in the process. Write or phone for our free U1 are used to control sev- My circuit is a car - battery free, 1- 800 -955 -2527, or eral bilateral switches. The voltage indicator (see Fig. catalog. Toll below. switches act just like relays, 6) that allows you to quickly see mailing address although they have a little check the relative health of internal resistance. When a battery. The LED readout Accredited by the Accrediting Commission of the an output goes high, its simplifies testing and the National Home Study Council bilateral switch closes, con- circuit lets you monitor the necting one of the column battery even under crank- outputs to the power supply. ing conditions. GRANTHAM For example, if sa goes high, When placed across a Engineering battery's terminals and the College of U3 -a closes, connecting C4 Grantham College Road to V +. normally open momentary The outputs of U2 are (Continued on page 86) Slidell, LA 70460 23

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www.americanradiohistory.comAmericanRadioHistory.Com Popular Lets face it, how often do we read it dill cult to pull away from you. And about attacks on joggers or peo- even if your attacker does manage to ple walking at night; or attacks on wrest it from your hand, the locking ac- Ele ctronics° tion of its on /off switch causes it to con - women in parking lots, even during MAY 1991 broad daylight? Such occurrences are -inue sounding. In additdan, the Sonic all too common. The Sonic Defender Defender easily fits within a vest pocket in finding the frequencies and warble can help you to ward off possible dan- or purse for easy carrying it non- threat- rates That cause the most discomfort. ger and in emergency situations, it can ening situations be a great attention -getting aid. Keep in mind, howeve that con- How it works. Figure 1 shows a sche- Defender. The Sonic Defender is a compact tinued exposure to the lousiness end matic diagram of the Sonic personal protection device that can of the Detender can cause perma- The circuit consists of two oscillator cir- a 74HC00 quad NAND help ward off any attacker, whether ar nent hearing loss. I he Sonic Defender cuits built around U1 -b, imal or human. The Defender is de- generates a sound intensity of about gate IC. Gates U1 -a and along signed to generate a very high intensity 130 dB, which is loud enough to hurt the with resistor R1, and capacitors C1 and sound to cause maximum discomfort ears of anyone that in pointed at. The C2 comprise a low- frequency, or war- to anyone that it directed towards. It is units actual operating frequency is ble rate, generator (oscillator), which small enough to comfortably fit in the c-en -ered around 3 kHz With a very high operates at a frequency of about 10 Hz. is used to smallest hand, and its wrist strap makes warble rate. Significart tirr was spent The warble rate generator

The Sonic Defender Protect yourself and your property with a blast of high-intensity sound

BY PHIL SALAS

www.americanradiohistory.comAmericanRadioHistory.Com Z -0 o lT1 S1 R6 D2 PARTS LIST FOR THE V D3 510i2 1N4003 D1 8S2 3 1K SONIC DEFENDER 1N751 1N4003 II - 14 SEMICONDUCTORS C5 OZ1 U1-74HC00, quad 2- input, NAND gate, 3.3 EFB-RP34B21 integrated circuit FA+ QI- TIP120 NPN 14 1/4 74HC00 1/4 74HC00 R2 4 DI, D2- 1N4003 I -amp, 200 -PI V, 4.7K 3 1 silicon rectifier diode 2 5 I tlt -b . l0 6 yy` D3- 1N751, 5.1 -volt, 400 -mW, Zener C2 R1 Cl y diode l 3.3 3.3 T 27K RESISTORS +I( C3 _ 01^ 01 (All fixed resistors are 1/4-watt, 5% units, TIP120 R7 unless otherwise noted.) 1012 R1- 27,000 -ohm C4 d, R4* Z R2,R3 -4700 -ohm .01 - 8.2K R3 12 9 4.7K R4-8200 -ohm (see text) 11 8 13 10.- R5, R6-510-ohm R5 R7 -10 -ohm, 1/2-watt *SEE TEXT 1/4 74HC00 1/4 74HC00 51012 1M ADDITIONAL PARTS AND MATERIALS CI, C2, 3.3 -11F, 16 -WVDC radial - Fig. I. The Sonic Defender consists of two oscillator circuits built around a 74HC00 quad C5- lead electrolytic capacitor NAND gate IC. One oscillator, built around Ul -a and Ul -b, comprises a low frequency, or C3, C41 0.01 -11F, 16 -WVDC, warble rate, generator,, the other oscillator, formed from gates Ul -c and UI -d, is used as a tone generator. monolithic capacitor S1 -Low- profile, locking pushbutton switch (Digi -Key 501 -PB) modulate the output frequency quencies independent of battery volt- T1 -8 -ohm to 1000 -ohm, audio (around 3 kHz) of the tone generator, age. Diode D2 was included in the which consists of gates U1 -c and U1 -d, circuit to prevent damage to the IC if BZ1- EFB- RP34B21 (Matsushita) resistor R4, and capacitor C4. the power supply is inadvertently con- transducer The warble sound is produced when nected with reversed polarity. Printed-circuit board materials, Orbit diode D1 is biased on and off through sprinkler head or equivalent, 1/4-inch nylon protector foot, heavy black resistor R2 at the rate of the low -fre- Construction. The author's prototype shoestring, 9 -volt alkaline battery, 9- quency generator. When D1 is biased of the Sonic Defender was built into a volt battery connector, wire, solder, on and off, capacitor C3 is alternately sprinkler head. The one used here is hardware, etc. connected to and disconnected from made by Orbit and sells for around $1 at ground through diode D1 at the warble local hardware stores. The sprinkler The following is available from Niche Technologies, Inc., P.O. Box 851264, rate, resulting in additional capaci- head is perfect in that it has just the right Richardson, Texas 75085 -1264: A tance being switched into and out of amount of room for the circuit and 9- complete kit of parts (including the high-frequency generator. When- volt battery, and it has an easily re- sprinkler head and printed -circuit ever C3 is connected to ground, the movable head so that battery replace- board) for the Sonic Defender for $19, frequency of the high -frequency gen- ment is easy. The pipe hole in the rear of plus $2 shipping and handling; erator is lowered, thereby giving the the sprinkler head is perfect for attach- printed -circuit board only for $3 output of the tone oscillator a warble ing the wrist strap assembly. postage paid; the EFB- RP34B21 effect. To prepare the sprinkler head, first re- Matsushita transducer $5 each postage An effort was made to keep imped- move and discard the internal parts paid. A fully wired and tested unit is ances low so that the generated fre- keeping just the body and screw on available for $29 plus $2 shipping and handling. Please send check or money quencies would be very stable. That's top. Drill a 5/16 -inch hole exactly 9/,00hs of order. Texas residents, please add why 3.3 -µF electrolytic capacitors were an inch below the wide opening end. 81/4% state sales tax. used for C1 and C2, instead of a single That's where the switch will mount. Take smaller value and a corresponding the transducer and clip off its mounting higher resistance for R1. feet. Drill a hole in the sprinkler head The output of U1 -d switches a current - cap to clear the "G" lead of the trans- amplifying transistor, Q1, on and off, ducer. Mount the transducer to the producing a pulsating DC voltage sprinkler -head cap using a hot glue through the primary of T1. The pulsating gun. voltage through T1's primary induces a The wrist -strap assembly is made higher voltage in its secondary, which is from a nylon 5/8 -inch protector foot applied to transducer BZ1. Resistor R7 available from your hardware store. Drill limits the average current through the a 1/8 -inch hole in the middle of the pro- transformer to less than 200 milliamps. tector foot and thread a piece of Resistor R6 and D3 pro- heavy -duty black shoe string through it. Fig. 2. The Sonic Defender was assembled vide regulation for the dual -oscillator Adjust for the desired loop length and on a tiny printed -circuit hoard, the circuit, and keeps the oscillator fre- tie a knot in the string, and cut off the template for which is shown here. 26

www.americanradiohistory.comAmericanRadioHistory.Com WARNING!! This article deals with D3 and involves the construction of a -C1-+ C5 I+ device that may be hazardous to + 9V R6 health and life. Do not attempt to implement or use the information R1 R4 contained herein to construct said device unless you are experienced U1 and skilled with respect to the same. D Neither the publisher nor the author S1 R2 R5 make any representation as for the completeness or the accuracy of the 01 information contained herein and any liability for damages or D1 disclaim I injuries, whether caused by or R3 arising from the lack of completeness, inaccuracies of the -C2- + -C3- -C4- information, misinterpretations of I R7 directions, misapplication of the Il an information or otherwise. .0000 BZ1 T-11/000 1K

Fig. 3. Assemble the printed- circuit board, using this parts- placement diagram as a Trial and Error. The final step in the guide. Note that because of the small size of the board, it will be necessary to mount assembling the Sonic Defender is to de- several axial -lead components vertically. termine the best possible resistor value for R4. Start by first turning the printed - excess. Now, apply some hot glue to the 8.2k, however, resistor values of 7.5k and circuit assembly over so that the bot- end of the protector foot, and press it 9.1k should also be tried in order to op- tom (trace side) of the board is visible. into the pipe hole at the rear of the timize the sound intensity. (The correct Connect a 9 -volt battery to the battery sprinkler head. value will be determined in the next connector. The original circuit was built on a 1.6- section.) Note the proper orientation of Point the transducer away from you D1, D3), turn the switch. Alternately press by 1 -inch piece of perfboard, and later the semiconductors (U1, Q1, D2, and on reconstructed on a printed- circuit and the electrolytic capacitors C1, C2, a 7.5k, an 8.2k, and an 9.1k resistor board (which is recommendec for and C5. Transistor Q1 should have the across the pads for R4. Turn off the unit, ease of wiring); a template for the leads bent at 90- degrees prior to disconnect the battery, and perma- printed- circuit board is shown in Fig. 2. mounting on the printed- circuit board. nently install the value that gives the Assemble the printed- circuit board, After all components except R4 have highest sound intensity. using the parts -placement diagram been installed, attach 6 -inch extension Once R4 is selected and installed, shown in Fig. 3 as a guide. DO NOT use wires to the 1000 -ohm winding of T1. slide the completed printed- circuit as- an IC socket for U1. Since T1 sits atop U1, Attach a 9 -volt battery connector to sembly into the body of the sprinkler the height of the socket will raise the the circuit board at the points and with head until the switch pops through the transformer high enough so that the the orientation indicated (the black hole. Secure the assembly with the completed assembly will not fit it the wire to - and the red one to +). Finally, switch nut. Reconnect the battery and sprinkler -head body. Use your hot -glue cut off the "F" lead on transducer BZ1. slide it into the body. Use an alkaline gun to attach the transformer to the IC. Then solder the extended transformer battery since the Sonic Defender typ- The transformer should be as close to leads to the "G" and "M" leads on the ically draws about 120 milliamps of cur- the rear of the printed- circuit board as transducer, and put a glob of hot glue rent. The alkaline unit should provide possible to maximize the space avail- on each transducer connection. about a half hour of continuous use. Do able for the battery. not use a Ni -Cd battery; they self dis- Switch S1, a low- profile unit, mounts charge at 1 -2% per day. Now carefully directly to the printed- circuit assembly, screw on the cap. Once that is done, with its solder tabs simply soldered to you're finished! the printed -circuit traces. A large al- ligator clip was used to hold the switch Conclusion. The Sonic Defender is an on the board while it was being sol- easy -to -build device that can provide dered in place. After soldering the an extra measure of protection when switch tabs to the board, apply some you are threatened. With its convenient hot glue to give the switch more me- wrist strap, you can even wear it to bed! chanical stability. The switch is used to It will provide you with a non -violent mount the completed printed-circuit means of warding off trouble, so you assembly to the inside wall of the sprin- won't be reduced to the level of your attacker just to defend yourself. The next kler head. Here is the Sonic Defender's printed- time someone tries to bother you, a When adding components tc the circuit board prior to the mounting of TI. cD co printed- circuit board, do not perma- Once TI is mounted, the integrated circuit blast from the Sonic Defender will send nently attach R4. Resistor R4 is nominally will no longer be visible. him packing. 27

www.americanradiohistory.comAmericanRadioHistory.Com BY STEPHEN J. BIGELOW ALL A B OUT

Of all the tools and equipment on a hobbyist's workbench, per- haps the most useful and ver- satile is the multimeter. They are relatively inexpensive and simple to use, and yet they can provide essential readings of voltage, current, and resis- tance- measurements imperative to building even the most sophisticated circuits. Because of their necessity, meters are readily available in a staggering variety of shapes, sizes, and features from an array of foreign and domestic (U.S.) manufacturers. This article will explain the important concepts behind the operation of both analog and digital meters. It will also present the major design considera- tions for each family of meter (volt, amp, and ohm), so you can build them to suit your own particular needs.

Analog -Meter Concepts. Until the last decade, the vast majority of all available test instruments contained analog meter movements to display readings. The overall design of this ana- log movement has changed very little since 1881 when a French physicist by the name of Jacques Arsene d'Arsonval developed the mechanism. In his hon- or, the devices are collectively known as d'Arsonval movements. The d'Arsonval movement is truly a marvel of engineering in its simplicity and great versatility. They are ideally suited for use in ammeters, voltmeters, ohmmeters, and bridge circuits. Analog movements based on d'Arsonval's de- sign have been employed extensively in more exotic test instruments such as decibel, power, and frequency meters (just to name a few).

d'Arsonval Operation. The function- ing of the d'Arsonval movement is re- markably straightforward. In its simplest form, a coil of fine wire is wrapped about a cylindrical iron core to form an electromagnet (Fig. 1). The elec- tromagnet is then mounted on very - low- friction bearings between the poles of a permanent magnet. A ten- sion spring, stops, and a pointing nee- 28

www.americanradiohistory.comAmericanRadioHistory.Com With a little knowledge you can build your own meter circuits. We provide you with what you need to know to design ammeters, voltmeters, and ohmmeters.

If want to build a die are added to complete the unit. specifications, it will deflect to its full through RsHUNT. you 0-1 amp (full scale), but When a current is applied to the scale at 1 mA and will add 43 ohms to meter to read on hand that carries meter, some portion of it is made to flow the series circuit. As long as the circuit you have a meter 1 mA (full scale), then 'SHUNT will be: through the electromagnet. The cur- carries 1 mA or less, the meter will read only rent flow generates a field in the elec- properly without the need for support 1- .001= 0.999 amps tromagnet that opposes the field of the components. If current should rise Using this value, we find the value of permanent magnet. The conflicting above 1 mA, the needle will be forced to be: fields create a torque that causes the (or "pegged ") against the clockwise RsHUNT electromagnet to rotate on its bearings stop. Severe or repeated surges can 43 x .001/0.999 = .043 ohms and tense the spring. Since the torque easily wrench the electromagnet off its If a .043 -ohm shunt resistor is used, the and the current are proportional, the delicate bearings, damage the inter- movement will reach full scale when 1 greater the current, the greater the nal springs, or burn out the coil. Be sure amp flows through the meter. It is al- torque on the movement, and the to use caution when applying current ways a good idea to keep the overall more the needle deflects. As the cur- to meter movements. It is often a good resistance of the assembly as low as rent drops, the tensed spring will tend to idea to place a fast -acting fuse in line possible to minimize the loading effects move the needle back to its rest posi- with the meter leads to protect it from of the meter on the circuit under test. tion. Thus the position of needle can be excessive current. Another consideration is the power used to indicate the amount of current Notice that d'Arsonval movements dissipated by the shunt resistor, which flowing in the meter. are polarized-current can only be ap- can be expressed as: The rest or zero position on d'Arsonval plied to the meter in one direction to by ensure clockwise rotation. A reversal of movements can usually be adjusted Pshunt - 'SHUNT2RSHUNT turning a small set screw located on the current will "peg" the needle against its For our previous example, the .043 -ohm front of their enclosure. Typically, meters counterclockwise stop possibly shunt resistor will dissipate: are "zeroed" with all current discon- damaging the movement as men- nected. Never use a zero -calibration tioned before. 0.9992 X .043 = .043 W screw as an offset or trim adjustment. But what if you want to measure more So a'/8 -watt resistor would do just fine. d'Arsonval movements are very deli- current than the movement alone can Now this is a very small value, but sup- handle? Easy, simply add a "shunt re- cate devices and can be damaged by pose our meter was to measure up to careless calibration. sistor" (RsHUNT) across the movement as 100 amps. Then ISHUNT would almost be are rated in shown in Fig. 3. The input current d'Arsonval movements ('INPUT) 100 amps: terms of their full -scale current require- that is applied to the meter circuit will 100 -.001= 99.99 amps ment (IFs) and their internal resistance split into meter current and shunt -re- cur- (R,NT). For example, a typical meter sistor current (IsHuNT) Just how much RsHUNT would be: specifications rent will flow through the resistor will movement might have 43 x .001/99.99 = .00043 ohms of 1 mA and 43 ohms. Those param- depend upon its value and the value of eters will become very important when the meter resistance (R,M). Power would then be: The shunt resistor serves two very im- we discuss analog meter design. Let's (100)2 x .00043 = 4.3 watts! take a close look at the operation and portant functions: it channels some cur- design of the most common analog rent away from the movement to That would require at least a 5 -watt meter applications- measuring cur- extend its useful range, and it reduces resistor, which would be much larger rent, voltage, and resistance. the overall resistance of the unit. Re- and run much hotter than our previous ducing the resistance minimizes the 1/8-wait resistor. Always consider the DC Ammeter Design. Ammeters load the meter places on the circuit. power dissipation. measure the amount of current flowing You can use the following formula to A multi -range ammeter can be cre- through them. So in order for a meter to calculate the proper value for just ated by simply making several appro- measure the current flowing through a about any shunt resistor: priate shunt resistors available to the You cal- branch in a circuit it must be inserted in meter via a rotary switch. can that branch. RsHUNT = RINTIFS / (RINPU1JFS) culate the value of a shunt resistor for as we did in the single - The simplest ammeter is the meter The amount of current flowing in the each range just in mind that you movement itself as shown in Fig. 2 (Ra shunt itself can be determined with the range example. Keep have to stick to powers of 10 and Rb are just two components in the following relationship: do not circuit). Manufacturers already pro- when you choose maximum currents. duce a variety of meters designed and 'SHUNT = 'INPUT 'Fs Feel free to pick any current range(s) that suits your particular needs. calibrated to function over a broad The first step is to determine the (70' CO If build a multi- range. As you can see from the meter's amount of current that must flow you do decide to 29

www.americanradiohistory.comAmericanRadioHistory.Com This is done by re- arranging its circuit PERMANENT Let's say we want to use our 1 -mA, 43- CLOCKWISE MAGNET configuration. Since our meter is now ohm meter movement in a voltmeter STOP POINTER measuring voltage, we must consider design that will measure up to 20 volts. what voltage will cause a full scale de- We know: flection. For the meter used in our pre- V 20 volts vious examples, according to ohm's VS = IFS Law it would take: X RINT = .043 volt IFS = .001 amp .001 x 43 = .043 volt Using equation 1, we can determine to cause full deflection. That means the value of RLIMIT: that if we were to use the movement (20 - .043)/.001 =19957 ohms COUTER- alone, an input of 43 mV would deflect CLOCKWISE / ELECTROMAGNET the meter fully. That value is commonly A 20,000 -ohm resistor will work satisfac- STOP í' referred to as the meter's "voltage sen- torily. Give it a try. BEARINGS INPUT sitivity" or VS. One word of caution: To CURRENT achieve the Unfortunately, a voltmeter that only best performance from the meter at Fig. I. This is a simple d'Arsonval reads up to 43 mV is not very useful in lower voltage ranges, keep the limiting movement. The deflection of the needle is most practical situations, but it is possi- resistor as close as possible to the cal- proportional to the input current (i). ble to extend the range of the meter by culated value. That is because the meter circuit will be more sensitive M1 down at lower ranges since the voltage MOVEMENT ONLY r -- across the meter will be closer to the IFS=1mARI=43f2 voltage dropped across the limiting re- Ra I I Rb sistor. If RLIMIT has poor tolerance, the ... reading will be less accurate. Higher I ranges are less sensitive since the

O TO 1 mA meter's voltage versus the applied volt- RANGE age is so much smaller, so you can af- ford to Fig. 2. A simple meter movement must he be more lenient with the limiting inserted in a series to a circuit to measure resistor's tolerance. current fow Unlike the shunt resistors in our am- meter circuits, limiting resistors are al- range ammeter be sure that the switch most always low-power ('/e or 1/4 -watt) you use is make -before -break, or that at devices. That is the general rule since least one meter lead is disconnected, only a small amount of current will ever any time you change ranges. That will prevent any surges of current through M1 the movement in the brief instant that IFS =1 mA RINT =4352 the switch may be moving between positions. This Don't worry if the values of resistance is the front view of a typical d'Arsonval-type meter movement. Note you calculate seem exotic; precision re- the zero -adjust .screw. sistors down to 0.1 ohm are available. Also remember that resistors can be adding a current -limiting resistor in se- combined in series and parallel net- ries with the movement. This limiting re- 'INPUT 'SHUNT works to obtain even lower values. sistor serves two very important Fig. 3. An expanded-range ammeter is The 1 -mA, 43 -ohm meter movement purposes. First, it dissipates enough en- really a .simple ammeter movement in used in our previous examples is just ergy to let the meter read within its parallel with a "shunt" resistor. one of the many units that are currently rated range. Second, it adds resistance on the market. Commercial DC -am- to the meter network, minimizing the flow through them. For our voltmeter meter movements are available in loading of the circuit under test. example, the power dissipated by the ranges from 0-25 µA all the way up to Effectively, the limiting resistor is limiting resistor would be: 0-15 amps. Their resistance can be as chosen so that the current flowing x high as 3700 ohms, or as low as .003 .0012 19957 = .01996 watt through the movement is equal to IFS ohm (depending on the scale). when the maximum desired input volt- That's well within the range of a 1/8 -watt age is applied. Remember that d'Ar- resistor. DC Voltmeters. Voltmeters measure sonval movements are polarized; be Multi -range voltmeters are equally the potential difference between any sure to apply voltage with the proper easy to put together. Work out the ap- two points in a network. For a voltmeter polarity. propriate resistor values by using equa- to function properly, it must be placed You can use the following formula to tion 1 for each scale that will be in parallel with the load creating the calculate the value of the limiting re- needed. Use a simple rotary switch to voltage drop. sistor: select the desired resistor, and thus the It is easy to use a standard d'Arsonval scale. For 1 -, 5 -, and 10 -volt ranges the movement in voltmeter applications. RLIMIT - ("MAx - IFS X RNT) /IFS (eq 1) limits can be calculated as follows: 30

www.americanradiohistory.comAmericanRadioHistory.Com knowing the full -scale current of the However, unlike a voltmeter or am- movement and the maximum voltage meter, resistance must be measured power off. That is be- Rzso rating of the particular scale: with the circuit cause ohmmeters supply their own cur- 10K VINT

I 9V RINPUT = VMAX /lFS rent for ease of use; any additional M1 IFS=1 mA For our example voltmeter, its input voltage from the circuit under test may RINT=4352 resistance would be: cause enough extra current to damage the meter. Even if damage 20/.001= 20,000 ohms RSCAIE UNKNOVJN does not occur, any reading would be 3.92K RESISTANCE Just remember that the input resistance worthless since the meter is calibrated for a particular scale is the same re- to work from its internal voltage only. Fig. 4. A meter's internal voltage source gardless of the actual amount of volt- We can use d'Arsonval movements to is used to drive an ohmmeter circuit. age applied. build our own ohmmeter as shown in Fig. 4. That type of ohmmeter is known as a "series ohmmeter" because of the series circuit it forms with the resistor. The design is also referred to as a "mid- range," or "general- purpose" ohm- RUMT meter. Although it is capable of measuring from 0 ohm to infinity, the BRIDGE M1 non -linear response of the meter only RECTIFIER allows accurate readings up to about 1/3 of the meter's scale (depending Fig. 5. A simple diode bridge can turn a DC voltmeter into an AC voltmeter. However, the upon the chosen scale). Accurate voltage drop across the diodes must be taken into account when determining the value of measurements below 1 ohm would re- the limiting resistor. quire the use of additional circuitry to

R1= (1- .043)/.001= 957 ohms, POWER R2 = (5 -.043)/.001= 4957 ohms, SOURCE R3 = (10 -.043)/.001= 9957 ohms

There is no limit to the number of ranges o- that you could add. METER INPUT CIRCUIT ND CONVERTER CLOCK LEADS V.I.R. I-4 Ohms /Volt Ratings. Many voltmeters o carry an ohms -per -volt rating. That rat- ing can be used to determine both the DISPLAY meter's internal resistance and the cur- MULTIPLEXER AND DRIVER rent sensitivity (IFS). For a voltmeter with a given ohms/ volt rating, the IFS can be determined simply by taking the reciprocal of the LED OR LCD DIGITAL DISPLAY rating:

= 1 /(ohms -volt rating) IFS -per Fig. 6. This is a block diagram of a basic digital meter. The inlua circuit is programmed which are not shown here. If you use a voltmeter marked at by the switches 20,000 ohms/volt, the full -scale current on compensate for errors caused by such of the movement would be: As you know from our discussion ammeters, there are a number of types factors as lead length and contact re- 1/20,000 = 50 pA and ranges of meter movements avail- sistance. Measurements over 10 higher excita- Conversely, if you wish to determine a able to suit a wide variety of applica- megohms would require meaningful voltmeter's ohms -per -volt rating, just re- tions. It is important to note also that tion voltages to generate arrange the formula to take the re- there are many movements on the current in a circuit. and For our ohmmeter of Fig. 4, the ciprocal of IFS: market already configured marked as voltmeters. They can be choice of zero resistor (RzE ,-) is almost ohms -per -volt rating = 1 /IFs handy if you can not find the resistor arbitrary. It can be as large or small as it limit you like. Its purpose is to compensate For our 1 mA meter, its rating would values to suit your needs, but will be: you to a single scale. for any variations in voltage or compo- nent values within the meter. A larger 1/.001=1000 ohms/volt Ohmmeters. Ohmmeters measure value of RzERO will give you a larger Try to keep the ohms -per -volt rating as the resistance across two points in a range of compensation, but will tend to high as possible to reduce loading on circuit. In order todo that, an ohmmeter drift more due to temperature and hu- the circuit under test. must be placed across the compo- midity. A smaller value will offer a small- The internal resistance for each volt- nent(s) to be measured just like a volt- er range of compensation, but it will be meter scale can be easily calculated meter. more sensitive. For our purposes, a

www.americanradiohistory.comAmericanRadioHistory.Com d'Arsonval movement to measure the Meter Glossary proper magnitude of the signal. AC sig- nals present special problems since the Accuracy percentage of which -A error polarity of the signal varies over time. If states how closely a meter reads the actual an AC signal were placed value of an input signal. The smaller the on a con- percentage is, the more accurate the ventional d'Arsonval movement, the meter. Many commercial meters can mea- needle would try to follow the changes sure to 0.5% accuracy. in magnitude. For signals more than 15 d'Arsonval Movement -an elec- Hz or 20 Hz, the needle would just tend tromechanical indicator using an elec- to quiver without tromagnet that is free to rotate within the producing any useful magnetic field of a permanent magnet. The reading. For AC signals to be measured coil will rotate in direct proportion to the accurately, they must first be converted amount of current flowing through it. to a corresponding DC level. High ohms resistance scale -A using a A simple bridge rectifier slightly higher voltage that will allow semi- circuit can conductor junctions to be forward- biased be used for AC to DC conversion for our when placed across the meter leads. voltmeter circuits. The full -wave bridge Low ohms --A resistance scale using a rectifier shown in Fig. 5 will allow current low battery voltage that will not forward - to flow through the meter in one direc- bias semiconductor junctions. tion only. However, Multimeter -A versatile meter capable of since the voltage will measuring several ranges of voltage, still pulsate over time, the meter will indi- Here is an overall view of a typical analog either current, or resistance. Also known as a cate the average (or RMS) value. For VOM. It can perform the three basic a "Multitester" or "VOM (volt- ohm-milliam- sinewave with a maximum voltage of measurements. meter)." VP, that is: Ohms/volt-A voltmeter rating that indi- cates 10,000 -ohm rheostat will be used. the effective impedance (or current 0.707 X VPEAK sensitivity) of the voltmeter scale. The rat- The meter scale is set with a fixed - ing is typically used to describe analog and the value for the limiting resistor value scale resistor, RSCALE' The meter meters. must be found from: will be calibrated based solely on the Rectifier-type AC meter --A conventional values of RscALE, DC meter movement modified to read the /IFS RzERo, and the internal RLIMIT - ` PEAK IFS X RINT 1.2) RMS value of voltage through - - baffery VINT. The value of can be a bridge or RsCALE full -wave diode rectifier. Already assembled AC- voltmeter calculated with the following formula: Resolution-The smallest amount of movements that can measure up to change that a meter is capable of detect- RSCALE VINT 300 volts are commercially available. - /IFS - RINT - RZERO /2 ing. The rating is most often applied to dig- Unfortunately, the solution is not so For the ohmmeter circuit shown, the ital meters. RMS (Root Mean Square) -The simple for AC ammeters. Introducing value of R would be: effective SCALE value of an AC signal. It is commonly calcu- the voltage drops produced by the rec- 9/.001 43 10000/2 = 9000 43 lated as 70.7% of the peak value of the AC tifier diodes can have very adverse signal (assuming a pure sine wave). 5000 = 3957 ohms effects on the circuit under test. Luckily, Shunt-A low -value resistor used in am- commercial A 3920 -ohm, 1% 1/4-watt resistor can be meter circuits to extend the range of the AC- ammeter movements used since the zero -adjust resistor can meter movement in use. The shunt is used are available off -the -shelf that can in parallel with easily be adjusted to compensate for the meter movement. measure up to 300 amps. Commercial the inaccuracy of the scale- resistance VOM's (volt- ohm -milliammeters) are readily value. As a general rule, though, try to available from many different vendors. Prices for analog meters can keep your scale resistor close to the cal- terclockwise to indicate zero resis- range anywhere from $20 to $200. culated value. Remember that the tance. If the needle swings too far greater the difference between your clockwise, or not far enough, simply ad- calculated scale resistance and your just Raw) until the needle rests on the actual scale resistance, the more you fully clockwise marking. That will now must adjust the zero -adjust resistor to represent zero ohms. Separate your test compensate for that error. That means leads and the needle should fall to the you will automatically lose a portion of fully counterclockwise marking. That your adjustment range just to compen- represents infinite resistance (or an sate for a poorly selected resistor. open circuit). Your ohmmeter is now An ohmmeter must be recalibrated calibrated for your chosen scale. each time the scale is changed, or When you place an unknown resis- after periods of disuse. In order to cali- tance between the test leads, it will brate our ohmmeter, first set the zero complete the meter circuit and cause adjustment to the approximate center the meter to deflect. The amount of the of its range, then short the test leads deflection will depend on the value of together. That establishes a current flow the unknown resistance. through the meter -test circuit itself, which will cause the meter to deflect. If AC Modifications. The meters we R7E,0 is in the center of its range and have discussed this far have been strict- This DMM can measure frequency, Hfe, is very RSCALE close to its calculated val- ly DC instruments-current must move and capacitance as well as resistance, ue, the meter should deflect fully coun- steadily in one direction in order for the amperage, and voltage. 32

www.americanradiohistory.comAmericanRadioHistory.Com Newark Electronics, Chicago, IL) as a 0 to ± 2 -volt voltmeter (see Fig. 8). Since ± the DPhil itself has a range of 0 to *2 volts DC, signals falling in that range can be connected directly to the meter UNKNOWN TO INPUT without the aid of any voltage- dividing CIRCJIT VOLTAGE components. The meter can be oper- ated conveniently from a single 9 -volt battery. In this particular model, a low - battery indicator informs you when the C battery power drops below 7.2 volts. The BL100102 is referred to as a 3-1/2 - allow for a digital -meter circuit to detect voltage Fig. 7. These various input circuits can digit meter. That means that the display and resistance (C). (A), current (B), consists of 3 full seven -segment digit displays and an indicator for a leading "1" called a "half" digit. Therefore, the Digital -Meter Concepts. Unlike the DECIMAL POINTS meter can display numbers anywhere analog meters we have discussed, dig- 0 o q from a -1999 to + 1999. If you use a 4- ital meters make extensive use of VLSI 1/2-digii meter, then there will be 4 com- 12 (Very Large Scale Integration) devices 11 131! seven- segment numbers plus a Da 02 D1 plete the functions required to 10 1, so on. to accomplish ROH leading and drive a multi- segment display. Although The schematic of our digital volt- modern semiconductor technology I I meter in Fig. 8 is very straightforward. B1 L II that perform has made single IC chips 9V Power is applied to the V+ and V- many digital -meter functions possible, I11.II terminals (pins 1 and 2). The signal to be BL100102 9 all DMM's (digital multimeters) contain MODUTEC RFH measured is connected to the IN HI and COM RFL the sections shown in Fig. 6. IN LOW pins. Notice that there are also a 7 6 The input- circuit section is informed +0 IN HIGH 15I few other simple connections to be by the switches and controls on the unit 0 TO ±2VDC INPUT made. The IN LOW pin must be con- input that will be ap- as about the type of -o IN LOW nected to the coon (common) pin plied to it (i.e. voltage, current, or resis- well as the RFL (reference low) pins of the Fig. 8. A pre -packaged digital panel tance). Figure 7 demonstrates just a few module. That establishes the common meter can be employed directly as a the possible input circuits. our meter of digital voltmeter. reference point between After some conditioning, the signal passes from there to the the A/D con- verter via a buffer. The buffer circuit pro- 1- vides some measure of isolation and D1 further signal conditioning. o i R1 0-2V 1.999 The AID converter is the very heart of 10MEG i S1-b S1 -a V+ for IN HIGH D2 a DMM. It is responsible converting 19.99 9V UNKNOWN R2 0 -20V the analog signal delivered from the VOLTAGE 1MEG MODUTEC /199.9 outside world into an equivalent cigital /0 -200V METER D3 word that will be interpreted by the dis- R3 MODULE the ND 100K play driver. The operations of o IN LOW converter are regulated by a ocal digital voltmeter. clock signal that can be up to several Fig. 9. A simple voltage divider can greatly extend the range of your kilohertz. Another local clock signal Note the switch selects the proper decimal point for a reading. controls the operation of the display. source of and any circuit under test. Also note The display- driver section consists of ered, DMM's require some that the ROH pin is connected to the RFH code -converting circuitry and a dis- power to operate. Hand -held DMM's bat- pin. That simply allows a 1:1 scale so the play multiplexer. The code -converting use a battery (often a typical 9 -volt meter will interpret and scale the signal circuit accepts raw digital information tery). More sophisticated benchtop properly. No other pins need to be con- generated by the ND converter, and DMM's usually have a built -in power nected. generates the corresponding BCD supply. If you want to extend the range of the (binary -coded decimal) numbers that Many of the voltmeter, you can add a voltage-divid- will appear in the display. The multiplex- Digital Meter Design. needed to build a digital er network such as the one in Fig. 9. With er is synchronized to the code convert- vital elements in the form the selector in the 0-2 -volt range, a 0 to er so that the appropriate display meter are already available panel meters. These 2 -volt signal would be connected element is activated when the BCD of commercial versatile assemblies are directly to the input. In the 0-20-volt code is generated. Multiplexing the dis- compact and easy to use. range, the 10- megohm resistor forms a play in this way is usually done at a very inexpensive and example, 9:1 voltage divider with the 1- megohm high rate so the display appears In our first voltmeter- design and 100,000 -ohm resistors. If 20 volts "flicker- free." we will use the Modutec Series BL100 through were applied to the network, almost 18 Lastly, there's the power source. Unlike digital panel meter (available volts would be dropped across the 10- the analog meters that we have cov- various nationwide distributors such as 33

www.americanradiohistory.comAmericanRadioHistory.Com 0 - 2VOLT +- + OUTPUT 01 IN HIGH I: R1 0 20mA - 9K DIGITAL INPUT i PANEL METER J I: R2 1K IN LOW

Fig. 10. An operational amplifier can be added to convert current into voltage for the digital panel meter. The shunt resistor determines the range.

Rx UNKNOWN - 9V 0 -200K RESISTANCE VIA DIGITAL - 2V PANEL This specialized analog meter is based on RREr METER a d'Arsonval movement modified to R1 IN HIGH measure 200K watts. 0- 2VOLTS OUTPUT R2 200K1 Digital Ohmmeter. Of course, IN LOW the dig- ital module can not measure resistance Fig. H. An operational amplifier can be used to form a resistance sensor for a digital directly. Like current, resistance must be panel meter. The reference voltage sets the range of the meter reading. converted into an equivalent value of voltage in order to be displayed. The circuit of Fig. 11 can be used to megohm resistor, leaving about 2 volts plifier configured as a non -inverting sense an unknown value of resistance at the input. In the 0- 200 -volt position, a amplifier. The meter leads can be inser- by using an operational amplifier con- voltage divider is formed between the ted into the circuit just like an analog figured as an inverting amplifier. The 10- megohm and 1- megohm resistors, ammeter. Current will flow through the input and output of the op -amp will and the 100,000 -ohm resistor resulting shunt resistor and generate a voltage have opposite polarity. The amplifica- in a ratio of 100:1. about A 200 -volt input drop. The potential is amplified by the tion factor is: will yield about 2 volts at the input to the factor of: module. You can alter the values of the - Rg/R1 divider R1 /R2 + 1 resistors to achieve other volt- With infinite resistance (no connection), age-division ratios. The multiplication factor would then be: the output would be: A ganged selector switch can be 9000/1000 + 1 =10 used to select the appropriate decimal - (cc /R1) x -2 place for and the resulting each scale as shown. The de- output voltage will be which means the reading is a positive sired decimal point supplied to the digital module. can be lit simply by over -range or 199.9 ohms. If R,c is 0 ohms connecting it to V +. In the 0-2V posi- For the circuit of Fig. 10, a 10 -ohm the output would be: tion, the left-most decimal point will be resistor will sense the current in the 0 to (0/R1) x -2 = 0 lit. The middle point will light in the 20 mA range. In that range, RSHUNT will - 0-20V range, and the one on the right develop a potential from 0 to 0.2 volts. The zero for the meter can be adjusted will light in the 0-200V position. At 20 mA, the 0.2 -volt DC signal will be by altering the the reference voltage amplified by 10 to yield 2 volts to the via RREr. This particular Ammeter. Remember that our meter module. In this case, 20 mA will cause a circuit has a useful range from 0 to module can only read DC voltage. In full -scale response. The middle deci- 200,000 ohms before reaching the top order for the meter to read current, the mal point may be used in this range of the DPM's scale. When R, = 200,000 current signal must be converted into a (19.99 mA). As a general rule, try to keep ohms, the output will be: related voltage signal. The circuit addi- the sense resistor as small as possible to - ( - 2) x 200,000/200,000 = 2 volts tion in Fig. 10 uses an operational am- reduce the load on the circuit under test. which produces a display of 199.9k For a 0 to 200 mA range, try a 1 -ohm ohms. Use the right decimal place (D3) sense resistor in place of the 10 -ohm for this scale. resistor. At 200 mA, the potential across To change the scale, change R1 and RSHUNr will be: R2 (they must be equal). For a 0- 20,000- ohm scale, replace R1 and R2 0.2x1 =0.2 volts with 20,000 -ohm resistors and turn on the That will be amplified by 10 to provide 2 middle decimal point (D2). Any un- volts to the digital panel meter. At 200 known resistance greater than 20,000 mA the DPM will be at full scale for a ohms will cause an over -range read- display of 199.9 mA, so you must use the ing. For the very best circuit perfor- Here's a typical digital panel meter with right decimal point, Try some different mance, try to keep the values of R1 and an LED display. It requires front -end scales, but be careful of excessive R2 as close together as possible. circuitry and switches to really be useful. power dissipation in the shunt resistor. (Continued on page 87) 34

www.americanradiohistory.comAmericanRadioHistory.Com An old-fashioned look combined with digital operation will make you want to trash your old pink piggy-this bank keeps track of what you save!

Build the S LOT-MAC HIN1E' BY MARC SPIWAK AND Electronic Bank JOHN YACONO

The that its on all the time, but the current Did you ever stop to think that by would waste a lot of space anyway. IR LED's would quickly merely saving your daily pocket circuit can count up to a thousand dol- draw from the batteries. That's why the push- change, you can gradually ac- lars, so you can build your bank just drain the is to manually activate the cumulate a small nest egg that can be about as large as you please. button used a timer circuit gives you approxi- used to fuel some of your hobby inter- A little bit of high tech is what gives unit; mately ten seconds to insert a coin be- ests? It's true, a buck or so a day adds up the bank its ability to actually "see" shuts off. However, every to well over $300 a year. The only prob- what coin has been inserted. Three in- fore power are coin inserted re- starts the ten -second lem is that finding out how much frared (IR) emitter /detector pairs a delay so you don't have to keep push- change is in a bottle or jar can be a positioned in the coin chute so that ing the button. pain in the neck. You could certainly go dime will block one of them, a nickel out and buy a bank that counts Iwo, and a quarter all three. A circuit, we discuss the change, but for a true hobbyist, that's made up of a handful of components, The Timer. Before bank's circuitry, we should explain a little cheating (and for most of us, it's expen- then decodes the information and about the functioning of the special sive). We now present a project-an ser ids it to the counter /display module. bit LS7210 programmable timer it con- old- fashioned "Slot- Machine" Bank- That is, of course, a simplified explana- Unfortunately, the LS7210 is so ver- that's inexpensive, fun to build, and will tion of how the bank works, but we'll get tains. we won't be able to discuss also encourage you to squirrel away to the details later on. satile that so we'll have to gloss over some money for your next project. It To operate the bank, all you have to all its features, its abilities for the sake of bre- even makes a nice gift for children and do is push a button on the top of the some of adults alike. bank to activate it; a green LED lets you vity. The timer is capable of operating in You just feed nickels, dimes, or quar- know it's on. Then, after inserting a coin modes. You select a mode ters into a slot on the side of the bank, in the slot, a beeper counts off the four different binary val- the bank figures out what coin de- number of cents in the coin as the dis- by placing the appropriate mode- select pins. We will nomination has been inserted, and the play counts up in single increments. The ue on its Iwo for use the one -shot (monostable) mode, total is updated and displayed on the only hitch is that you do have to wait is by tying the mode - front panel. Pennies will register as a the bank to finish counting one coin which chosen select pins (pins 1 and 2) low. dime, so they shouldn't be inserted; be- before inserting another. co The can work with an external or sides, they don't add up to much and The bank could have been made so chip 35

www.americanradiohistory.comAmericanRadioHistory.Com R3 LED1 33052 +6V

+6V +6V B4 83 B2 1.5V 1.5V 1.5V R1 +6V F15 +6V 220K 10K F19 2N2222 D1 ti-0 +6V R4 04 10K 1N4001 S1 1552 F18 2N2222 AN 10K 01 TIL414 14 D2 Kl 1N4001 5V ti- C5 ± V9 CLN 1/4 4070 LED2 4.7 3 I TRIGGER 5 6 SEP8703-1 Cl + 6V CLK 33I 12 +6V Q = C2 F12 U1-a R10 4.7 10K íT. C6 1/2 4013 R6 100K .001 Q 11 ...L. + 02 10K "2" --4A47---74--0- +6V -o 10 14 S2 TIL414 D "4" 81 -- 13 1.5V RESET ® 2 4 1 U3 LED3 RESET V00 Vss L37210 F111 SEP8703-1 U4 -a TIMER 56K 9 DISPLAY +6V 12 '/2 550 DISP1 +6V BUZZER COUNT 8 14 3 R7 10K CLK 1 C3 03 "8" T.001 711414 0 .005 U1-b EXT +6V 1/2 4013 CLK U6 LED4 Q "16" + 6V 11914 SEP8703-1 13 10 161 /r OUT R GND S COUNT Ves 2 1315 10 7I SI MODE GND U5 22052 BOTTOM VIEW 8 .2 7 4040 -§Mr-- GND 1_ R14 04- 06 RESET Q10 R12 1/4.4070 10K EMI [TER EMITTER 11 14 68052 R13 COLLECTOR SEE TEXT BASE 10K BASE COLLECTOR 06 2N2222

Fig. I. This is the circuit for the "Slot- Machine" Bank. The phototransistors on the left determine what coin has been put in the slot and that is converted into pulses for the counter.

internal clock. As you'll see, we will need The length of the timing period is de- before going low again. If we send the a clock that can oscillate between termined by the frequency of the exter- pulses to a binary divider with a 210 ground and + V to provide the proper nal oscillator and the logic levels at a (1024) output, that output will go high 5 logic -level signals needed to operate series pins of (pins 8 -12) called the times. If W is 11, that same divider output other parts of the circuit. The internally "weighting-factor inputs." Those inputs pulses 10 times, and if W is 26, the divid- driven clock does not swing up and accept the binary l's complement of a er yields 25 pulses. Each of those divi- down that far, so we must use an exter- number aptly called the "weighting sions has a remainder, so the divider nal clock. The external -clock mode is factor." That number programs the must be reset to zero after each coin selected by tying pin 4 high. The exter- timer to hold the output high until the value is tallied to be useful for counting nal oscillator can run continuously with- clock has gone through a certain coins -but that's taken care of, as you'll out affecting the timer's output; the number of transitions. The number of soon see. timer will only become active when its clock pulses (P) counted by the timer is trigger input (pin 3) is toggled. given by: The Circuit. The "Slot- Machine" Bank The trigger input can be positive- or uses some common components in an negative -going depending on the P = 1 + 1023W interesting fashion to provide some un- timer mode used. For monostable where W is the weighting factor. In that usual features. One key component, mode, only negative transitions trigger sense, the timer is similar to a program- that is not so common, is the counter/ the timer; positive ones are ignored. mable counter, which is how it's used in display module denoted DISP1 in the When a negative transition is presented the bank circuit. schematic diagram shown in Fig. 1; for- to the trigger input, the output (pin 13) If W is six when the monostable is trig- tunately, it can be purchased from Ra- goes high for one timing period. gered, the timer will count 6139 pulses dio Shack (see Parts List). It comes as a 36

www.americanradiohistory.comAmericanRadioHistory.Com QUARTER COINS ROLL IN THE NICKEL PARTS LIST FOR THIS WAY "SLOT-MACHINE" BANK DIME

SEMICONDUCTORS U1 -4013 dual flip -flop, integrated

circuit , U2 -4070 quad xoa -gate, integrated circuit U3- LS7210 programmable- timer, integrated circuit dual oscillator/timer, integrated U4-556 (SIDE VIEW) circuit U5 12 -stage binary- ripple -4040 COIN counter /divider, integrated circuit 2 & 3 EMITTERS U6-T1914, or similar, transistor-output I I optoisolator /coupler, integrated circuit 4,...... r;;7/ QI- Q3- TIL414 infrared phototransistor Q4-Q6--2N2222 general -purpose NPN silicon transistor ALL DIMENSIONS IN INCHES uu DISPI- TL90063 LCD counter module DETECTORS (Radio Shack 277 -302) (TOP VIEW) /clime DI, D2- IN4001, I -amp, 50 -PIV, Fig. 2. There are three pairs of IR emitters and detectors: pair I forms a trigger rectifier diode detector, pair 2 is for nickels, and pair 3 is for quarters. LEDI -Green light- emitting diode LED2- SEP8703 -1, or similar, LED4- track of the total, it remains on all the Q3 infrared-emitting diode time. That is nothing to worry about, RESISTORS though, as it consumes only 3 ILA. (All resistors are 1/4-watt 5% units.) The rest of the circuit does not re- RI- 220,000 -ohm ceive continuous power. There is a R5 R13, R14- 10,000 -ohm Qt R2, -R9, power -saver circuit built into the unit R3- 330 -ohm that turns the rest of the circuit off if left R4-15 -ohm when connected to R10-100,000-ohm idle. Cells B2 -B4, form a 6 -volt R 11- 56,000 -ohm the counter's battery (B1), re- QUARTER R12 -680 -ohm supply that is used to power the of the circuit. R 15- 220 -ohm mainder NICKEL When S1 is depressed, it momentarily CAPACITORS DIME connects the positive side of B1 to the COIN DIRECTION C1- 33 -11,F, 16 -WVDC, electrolytic That activates C2, C5- 4.7 -p.F, 16 -WVDC, electrolytic negative side of B2. Fig. 3. Shown is the outline for the three C3-0.001 -µF ceramic -disc monostable U4 -b (half of a 556 dual coins detected by the circuit, and their C4-0.005 -11F ceramic -disc oscillator/timer). As you may know, to relationship to the sensors. If your optics C6-0.001 -µF monolithic trigger such a monostable, there must have trouble with cross -talk between Q2 and Q3, you can move Q3 further to the MATERIALS be a negative pulse at the trigger input ADDTIONAL PARTS AND right. BZI- Piezo- electric buzzer element (pin 6). If you just tie that pin to ground, KI- Subminiature, 5 -volt, the monostable can't time -out. Since in log - Perfboard, fiber-optic cable, wire-wrap C2 is initially uncharged, it imitates a collectors, thus, appear to be the sockets, wire-wrap wire, solder, jumper low and is allowed to slowly charge via ic-0 state. If an LED is blocked by a coin wire, wood, etc. R2 to allow the monostable to time out. in the channel, the collector of its corre- Note: Fiber-optic cable is available from The monostable turns on relay Kl, which sponding phototransistor is pulled high Circuit Specialist, Inc., PO Box '2047, connects the cells together until the by the pull -up resistor and generates a Scottsdale, AZ 85271 -3047 (Tel. monostable times out. As you'll see logic 1. 800 -528 -1417); and from Edmund though, the monostable is reset each The coin's size (and thus its value) de- Scientific, Co, 101 E. Gloucester Pike, a coin. LEDI termines which LED's get blocked (see Barrington, NJ 08007 (Tel. time you feed the circuit Fig. 3). All coins block light to Q1, which is 609 -573 -6250 and 609 547 -3488): indicates that the circuit is fully powered and ready. used to provide a trigger signal. The When a coin is inserted into the coin trigger signal is used to indicate that the coin is in the proper position to block preassembled counter with a built in 5- slot of the bank, it rolls down a channel, of the the o =her two LED's as appropriate. If the digit display. The two least- significant or chute (see Fig. 2). On one side LED's coin is a dime, only LED2 is blocked, digits are used to represent cents, so it channel are three infrared causing the collector of Q1 to go high; can display up to $999.99. When it (LED2- LED4), and on the other side of opposite them, neither LED3 nor LED4 is blocked, so the counts, buzzer BZ1 beeps once for each the channel, directly collectors of Q2 and Q3 are low. A nick- cent, and can be reset to $000.00 by are three infrared -detecting pho- respectively). el blocks LED2 and LED3, so Q1 and Q2 depressing S2. The display unit is de- totransistors (Q1 -Q3, light are high and Q3 is low. A quarter blocks coupled by C6 to prevent noise prob- Since the presence of infrared Q1 -Q3 go high. is turns the phototransistors on, they nor- LED2 -LED4, making có lems. Counter /display module D SPI CD pull -up resistors. Their Regardless of the coin's value, the powered by B1 and, since it must keep mally ground their 37

www.americanradiohistory.comAmericanRadioHistory.Com trigger signal provided by Q1 causes TABLE 1- WEIGHT -FACTOR LOGIC the two D -type flip -flops, U1 -a and U1 -b, Detector Weight (w) Pin Input (w) to capture the data from Q2 and Q3. The latched outputs of the flip -flops are COIN 02 03 Decimal Binary 8 9 10 11 12 used to help convert the phototran- 5 1 0 6 0 0 1 1 0 1 1 0 0 1 10 sistor data into the weighting inputs re- 0 0 11 0 1 0 1 1 1 0 1 0 0 25 1 1 26 1 1 1 quired by the timer (U3). 0 0 0 0 1 0 1 As mentioned earlier, the weighting factor needed for each coin will be the value of the coin plus one. The binary 1's complement of the weighting factor SLOT THESE HOLES will have to be supplied to pins 8-12 on the timer chip to program it. Pin 8 is the most -significant bit, while pin 12 is the least- significant bit. As you can see from Table 1, pin 11 of U3 can simply be tied low, as it is zero

regardless of the coin's value. Pin 12 is always equal to the value of Q2. Pin 8 of U3 is the inverse of Q3. Pin 9 is the xoa of the two transistor values, and pin 10 is its inverse. Those logical relationships are maintained by the flips -flops (U1 -a and U1 -b) and the xoa gates (U2 -a and U2- b). Note that U2 -b is set up as an inverter to provide pin 10 of U3 with the inverse of the signal applied to pin 9 of U3. The timer receives its trigger signal COIN -SLOT ADJUST from Q1 via inverting transistor Q4. Note that C5 delays the action of Q4, and Fig. 5. The coin chute is made from two slats of wood with a narrow strip of wood in the thus the timer, so the flip -flops and the middle, all held together with screws. xoa gates have a chance to set their outputs. Once triggered, the timer out- U5 (multi -stage divider) at pin 11. The put goes high and the IC begins to resulting low at pin 11 of U5 enables it, count a number of pulses from U4 -a and it starts to divide the pulses from the (the external clock) based on the external timer. When the timer goes low weighting- factor value. again, the reset input goes high, clear- The timer -output pulse does two ing any remainder and disabling U5. things: First, it causes U2 -d (which is used The divided output is inverted by Q6, as a buffer) to turn Q5. on That transistor which operates optoisolator U6. The discharges the timing capacitor for the optoisolator ties the count pin of DISP1 power- saver's monostable, effectively high for each pulse, causing the resetting it. Second, the timer output is counter to advance once for each inverted and sent to the reset input of cent. Fig. 6. Stack the wood on top of each other and tape them together to ensure WIRE LEADS that your drill holes will match up Construction. Since few components TWISTED AND perfectly. are in SOLDERED used the circuit, it is the easiest

HOLES SENSOR SLIGHT ANGLE IR EMITTER OR DETECTOR

SMALL -DIAMETER HEAT SHRINK

LARGE-DIAMETER INSULATION LIP HEAT SHRINK (SEE TEXT)

FIBER OPTIC CABLE HARDWARE Fig. 4. Prepare the IR detectors and HOLES emitters as shown here. Note the lip faces Fig. 7. Use this pattern as a drill guide for the coin chute. Be extra careful when drilling the component. the sensor holes.

38

www.americanradiohistory.comAmericanRadioHistory.Com Note: Although a 11914 optoisolator/ coupler is specified for U6 both in the Part List and the schematic diagram, almost any optocoupler that has a transistor output can be used. You should supply leads for the IR de- tectors and emitters to be connected later on. You need one pair of leads for each phototransistor and one pair for all three emitters, since they are con- nected in series. Leave a little extra length on the wires for now; it's also a good idea to label each wire. A problem came up in trying to tigure out how to mount the IR detectors and emitters because their diameter is difference be- Fig. 8. Attach a U- shaped mounting bracket to the coin chute as shown. That makes larger than the height installing the chute in the cabinet very easy. tween a nickel and a quarter. Fiber - optic cable solved the problem; its di- ameter is comparable to the height dif- ference. Fiber -optic cable is available from several sources; two of those are given in the Parts List. Prepare the IR detectors and emitters as shown in Fig. 4. Twist and solder a length of wire onto each lead, and cover with heat -shrink tubing. Using a sharp blade, cut a length of fiber -optic cable, leaving as flat a face as possible. Hold a match to one end of the fiber - optic cable for a moment; a lip will form around the insulation. Now, using wider heat -shrink tubing, affix the piece of fi- ber -optic cable to the end of the as- sembly with the insulation lip facing the component as shown. Ws best to build the coin chute now. Don't waste time trying to get the circuit to work with a test fixture, since you'll only have to build the chute anyway and it's very hard to get the detectors to work without the chute. The chute was made from two slate of wood with a narrow strip of wood-a little wider than a quarter -acting as a separator and forming the bottom. All three pieces are held together with screws, and the holes in the bottom strip of wood are slotted to allow for fine ALL WOOD coin- height adjustments (see Fig. 5). You 1/2 INCH PINE EXCEPT FOR can add an adjustment screw to the FRONT PANEL: top of the coin slot to decrease the IS 3/16 INCH PINE IT width of the slot if the sensors seem to ALL DIMENSIONS IN INCHES be somewhat insensitive. Once cut to size, the pieces of wood should be painted black. Stack the on top of each other as Fig. 9. These are the basic measurements of the cabinet. The top section is hinged to wood pieces allow access to the bank's coin compartment and the reset button. shown in Fig. 6, and tape them together to keep them stable as you drill so that perfectly. Use thing to build in the entire bank. Follow- wrap DIP sockets for all of the IC's. The the holes will match up Fig. 7 as a drill guide, and remember to ing Fig. 1, the connections are made connections to the board from the bat- using point -to -point wire -wrap tech- teries, switches, etc., are made with slot the holes in the narrow piece. the niques on a piece of perforated con- insulated stranded wire soldered to the The sensor holes should match 85) struction board. Be sure to use wire- appropriate points on the board. (Continued on page 39

www.americanradiohistory.comAmericanRadioHistory.Com Lee de Forest claimed he got the iaea for his The Birth "audion" from watching a gas flame burn. John Ambrose Fleming thought of the that story was just so much hot air.

Wireless telegraphy held excit- Vacuum ing promise at the beginning of the twentieth century. Peo- ple with imagination could see the po- tential that the remarkable new techno:ogy offered for worldwide com- Tube munication. However, no one could have predicted the impact that the soon- to -be- developed "oscillation BY ,AMES RYBAK R valve" and "audion" wireless- telegra- phy detectors would have on elec- tronics -echnology.

Background. Shortly before 1900, Guglielmo Marconi had formed his

own company to develop wireless - telegraphy technology. He demon- strated that wireless set -ups on ships could exchange messages with nearby stations on other ships or on land. The Marccni Company had also transmitted messages across the Eng- lish Channel. By the end of 1901, Mar- coni extenCed the range of his equipment to span the Atlantic Ocean. It was obvious that telegraph lines with submarire cables and their inher- ent limitations would soon disappear. Ships at sea would no longer be iso- lated. No location on Earth would be too remote tc send and receive mes- sages. Clearly, the opportunity existed for enormous Financial gain once relia- ble equipment was available. To that end tuned electrical circuits were developed to reduce the band- width of the signals produced by the spark transmitters. The resonant circuits were also used in a receiver to select one signal fron among several trans- missions. Simple design principles for resonant antennas were also being explored and applied. However, the sensitivity and reliability of the devices used to detectthe wireless signals were still hin- dering the development of commer- cial wireless- telegraph networks.

Inadequate Detectors. The detector most co-nmorty used at the turn of the i century was the coherer, developed by

4 o

www.americanradiohistory.comAmericanRadioHistory.Com do not occur overnight and usually in- Edouard Branly in 1890. Basically; the the efforts of more than one per- coherer consisted of a hollow non-con- volve ducting tube filled with metallic filings. son. Normally, the coherer acted as an the Way. Thomas Alva open circuit. However, when a voltage Edison Lights contributed substantially to the produced by a spark discharge was Edison the thermionic diode applied, the coherer became con- development of through his work with the incandescent ductive and remained that way until lamp. In 1879, he had produced a the filings were shaken loose by tap- with a carbon filament ping the tube. practical lamp that on DC. The coherer was not a very sensitive operated After lamp had operated for a or reliable detector and the tapping each that a black de- required between each telegraphic while, Edison noticed carbon formed on the inside of dot or dash meant that messages posit of The carbon could not be transmitted very rapidly. the class envelope. seemed to be coming from the nega- Despite its limitations, the coherer was the filament, since that was the best detector of wireless signals tive side of burned out. The available at that time. the side that always the Marconi realized the need for an im- deposits appeared everywhere on except where proved detector if his company was to inside of the envelope of the filament its a world- the positive end attain goal of establishing Fist . I. Lee de Forest's first flame detector the flow of carbon particles, wide wireless -telegraphy network. Al- incorporated only one battery and needed blocked line or "shadow" of the ready, he had modified the initial no filament current. leaving a cear design of the coherer to increase its filament on the glass. particles obviously sensitivity and reliability as much as Since the carbon from the filament, Edison won- possible. Still, the coherer had too many placed across the :.lit, and electrical came fundamental limitations to ever be- connections were made to the ends of dered if they might be electrically there might come a satisfactory detector in com- the foil. The water drop acted as a charged. He hoped that preventing the deposits mercial use, particularly on board a short- circuit in tha absence of a signal be a way of reducing the light ship rolling in a stormy sea. and as an open- circuit when a signal from occurring and the lamp. In 1902, Marconi developed and was present. output of patented Iwo types of magnetic de- Tapping was not required between Edison found that a current could be tectors that overcame the need for each telegraphic dot or dash, but the measured by a galvanometer con- mechanical tapping. They permitted drop of water became electrically de- nected between a wire in- the messages to be sent at a more rapid composed an: unable to serve its side the bulb (but not touching of the rate than did the coherer. One design furction after a mirute or two of use filament) and the positive end However, no current utilized a constantly rotating magnet, du= to the minute electrical currents power supply. the while the other employed a rapidly that flowed thrcugh it. could be measured when gal- moving endless belt of iron wire. Lee de Forest refined the basic de- vanometer was connected between negative pole of the Both magnetic- detector designs in- sign and tried numerous substances as the electrode and volved more mechanical complexity a replacement tar the water drop. He power supply. indicated than was desirable and provided less never succeeded it producing a truly This unidirectional current particles sensitivity than was needed. The "/lar- rel able anti -coherer detector for his that the current producing coni Company, however, did use mag- telegraphic responder, or "sponder" as were negatively charged. Edison as- parti- netic detectors in its network of he called it. sumed the negatively charged The flow of telegraph stations for many years until a However, Reinalld Fessenden de- cles were carbon particles. better detector was available. ve oped a sensiive fluid -based detec- electrons that he was actually measur- not be "discovered" until Which brings us to Lee de Forest. He tor in 1902, whi:h he called his "liquid ing would also had dreams of establishing a com- bcrretter." Beccuse it utilized a fine wire 1897 by J.J. Thomson. the wire cur- mercially successful wireless- telegra- making shallow contact with a liquid Edison soon replaced with a flat phy company of his own. He, too, (acid) surface, -he barretter was not rent- collecting electrode the legs realized the need for a more sensitive suited for shipboard use. Fessenden's metal plate located between to be and reliable detector and spent sev- potent on the Darretter was also an of the filament. The plate proved collec- eral years trying to develop a workable obstacle to its commercial land use. an even more effective current telegraph receiver, or responder, 3oth the Marconi Company and de tor. Edison noted that the current flowing based on what was called the "anti - Forest continue_. the search fora better the tem- coherer- detector" principle. detector. Their gocls were the same to the metal plate varied with of the filament Lee de Forest had gotten his idea for and their searcres led each to virtually perature (brightness) volt- the detector from reading a repert of a identical thermionic devices by follow- and, hence, with the applied DC laboratory experiment that had taken ing what de Forest c aimed were totally age. He proposed using the modified as a voltage -mea- place in Germany. The device initially different apprc aches. The story of the incandescent lamp a patent consisted of a small piece of metal foil development :f the thermionic vac - suring device and obtained 1883. cemented to a glass plate. The foil was uLm tube that follows clearly demon- on the design in 8 a be- (r) lit with a razor, a drop of water was strates how most significant advances Unfortunately, being confirmed 41

www.americanradiohistory.comAmericanRadioHistory.Com liever in the use of DC voltages only, He named his detector the "oscilla- Edison never connected an AC voltage tion valve." It is important to remember to the current -collecting electrode and that, being a diode, Fleming's device never placed any greater significance could only rectify oscillating currents; it on the unidirectional current flow he could never produce them. More com- had observed. Hence, he never real- monly today, we know his detector as ized that his device could have been the thermionic "valve" or 'tube." developed into the first thermionic rec- After this first wireless- detector experi- tifier diode. Nonetheless, Edison's de- ment, the unheated current -collecting vice was later to have a significant electrode in the lamp was replaced by influence on the development of the a hollow metal cylinder surrounding, thermionic rectifier in England by John but not touching, the filament. Fleming Ambrose Fleming. immediately applied for patents on his William Preece, Chief Engineer for oscillation valve in England, the United the British Post Office, came to America States, and Germany. The artwork at the in 1884 to attend the International Elec- beginning of this story is a reproduction trical Exhibition in Philadelphia. While of the drawing of the oscillation valve there, he saw some of Edison's Inven- and detector circuit he included in his tions on display. Before returning home, application for an American patent. Preece visited with Edison and ob- The British and American patents tained several of the incandescent Fig. 2. The second style of flame detector were granted to Fleming on Sep- lamps with the added metal -plate had a local battery circuit which allowed tember 21,1905 and November 7,1905, electrode. it to operate better. respectively. Those dates would be- Preece experimented with the modi- come significant in later priority dis- fied lamps for a while. He was the first to putes. use the term "Edison effect" to describe current. However, at the time, he never the from the fila- suggested this or any other practical A Flame Sparks de Forest. In Sep- ment that resulted in unidirectional cur- use for the device. tember, 1900 de Forest was working in rent flow to the metal plate. Later, Fortunately for the future develop- his room by gas light with his sponder Preece apparently gave the lamps to ment of radio technology, Fleming was one night and noticed something very the Edison Electric -Light Company of hired in 1899 as a scientific adviser by strange. When he operated the key of London. the Marconi Wireless Telegraph Com- the spark transmitter, the gas light pany. He spent the first several years flickered. He immediately called his as- Fleming Enters the Picture. John developing better transmitters and sistant to observe this phenomenon Ambrose Fleming would be knighted power -generating equipment for and together they pondered its signifi- "Sir Ambrose" almost a half- century them. In 1904, Fleming was assigned cance. later by iing George V for a lifetime of the task of developing an improved Their first reaction was to believe that scientific achievement. In 1884, how- detector. A suitably sensitive and rug- the flickering flame represented a new ever, Fleming was a consultant to the ged detector was still sorely needed by type of detector action which might Edison Electric -Light Company of Lon- the Marconi Company. overcome many of the problems that don. Fleming soon decided to try one of plagued the sponder. Fleming had noted the same the modified incandescent lamps as a The two excited experimenters darkening of incandescent lamps and detector, remembering its ability to pro- watched the flame respond to the key- the formation of a filament "shadow" duce unidirectional current flow from ing of the transmitter and took detailed observed by Edison. His initial experi- low- frequency AC. The question in notes for several weeks. However, when ments with the newly obtained modi- Fleming's mind was whether or not the the transmitter was moved to an adja- fied incandescent lamps confirmed rectification effect would work at wire- cent room and the door was closed, the other findings of Edison and Preece less- telegraphy frequencies. the flickering of the flame stopped. It as well. However, Fleming made an ad- An induction -coil based oscillator cir- then became clear that the flame was ditional and important contribution: he cuit was built to produce electromag- responding to the sound waves gener- explicitly reported the unidirectional netic waves. A second resonant circuit ated by the spark transmitter and not to flow of current in an 1896 scientific pa- was located some distance from it and the electromagnetic waves. per. was tuned to the oscillator's frequency. Very disappointed, de Forest He also observed that current flowed The second circuit included one of the stopped the flame experiments. He when the filament was heated by an modified incandescent lamps, to- later maintained, however, that the AC voltage with a frequency between gether with a galvanometer to indi- flickering flame started a train of 80 and 122 cycles per second. With an cate the hoped -for rectified current. thought in his mind that ultimately led to AC filament voltage, it obviously didn't When the oscillating circuit was acti- the development of the triode audion. matter which side of the filament was vated, the needle on the gal- By 1903, de Forest had developed a connected through a galvanometer to vanometer deflected, indicating rec- flame detector that worked. He inser- the current -collecting electrode. tification of the high -frequency wireless ted two platinum wire into Fleming had thus come close to rec- signals. Fleming had found, in that Oc- the flame of a Bunsen burner. He next ognizing the potential use of this modi- tober of 1904, the wireless telegraph connected a battery and a telephone fied lamp as a rectifier of alternating detector he was seeking. receiver in series with the wires. One

42

www.americanradiohistory.comAmericanRadioHistory.Com electrode was connected to an anten- He later would argue that substantial na and the other to a grounded water differences existed between the two pipe. This arrangement as it was used, is devices. shown in Fig. 1. Signals from the antenna changed A Control Element is Added. Lee de the conductivity of the flame which, in Forest was convinced that his audion's turn, changed the amount of battery sensitivity as a detector could be in- current flowing. That produced an au- creased even more. Remembering the dible sound in the receiver's headset. improvement the separate local circuit The flame detector actually acted as a had made in his flame detector, he form of relay with the wireless signal added an additional plate external to triggering the flow of current from the the glass envelope as shown in Fig. 4. Fig. 3. Lee de Forest's diode audion battery. Lee de Forest's use of the word The external plate provided what de detector allowed him to eliminate the "relay" rather than "rectifier" would be Forest called "electrostatic control" of flame by using a low -vacuum glass tube. crucial in his later legal battles. the detector. He then built a similar de- With the flame detector, de Forest vice with a coil on the outside of the was able to copy transmissions from a glass which produced "electromag- ship in New York harbor. Two problems netic control." were immediately obvious, however. The next audion de Forest built had The ability of the flame to detect the two separate internal plates. The plates signals was affected by air currents. were located on opposite sides of the Secondly, the Iwo common electrodes filament and the second plate was used for both the antenna current and used as the control element. Lee de the battery Current resulted in a by -pass Forest was amazed with the perfor- path for the signal around the flame, mance of this audion. A patent ap- was resulting in decreased sensitivity. Fig. 4. The audion with external plication on this first triode audion The first problem was easily solved by electrostatic control used a plate that was filed on October 25, 1906. Lee de Forest shielding the flame against air currents. external to the the tube. It was soon was granted the patent on January 15, The second problem was solved by followed by a device with an external coil. 1907. using one set of electrodes for the an- It did not take de Forest long to real- tenna and ground while a second set placed inside the envelope to produce ize that the control element should ex- was used for the local battery circuit. increased ionization. ert an even greater effect if it were That configuration is shown in Fig. 2. Lee de Forest filed for several patents located between the filament and The device's patent request was on this two- electrode "oscillation-re- plate. Obviously, a solid control ele- signed and witnessed on November 4, sponsive device" (as it was called in the ment would block the flow of current. A 1904 and filed on February 3, 1905. The patent applications) during the first half zigzag wire arrangement was used and 1904 signing date was twelve days be- of 1906. More commonly, however, de was eventually developed into the fore Fleming's patent application was Forest referred to the device as his "au- "grid" found in today's tubes. filed. Those dates would become im- dion." The patents were awarded be- The three element "grid audion" portant when de Forest argued that the fore the year's end. proved to be a much better detector. flame detector, and not Fleming's Initially, the Iwo electrodes in de For- The circuit in Fig. 5 is the one de Forest valve, inspired his later "audion." est's audion were both filaments. Soon included with his January 29, 1907 grid - Lee de Forest believed that the gases he eliminated the need for one battery audion patent application. The patent ionized by the flame produced the re- by replacing one of the filaments with was granted on February 18, 1908. lay action. The flame, itself, was only the an unheated plate electrode. Lee de And that's how Lee de Forest's most mechanism for producing the gas Forest now found that the polarity of the famous and important audion was ionization needed. Other means of "B" battery in the circuit (shown in Fig. 3) "born." It, like the earlier , was a heating the gases sufficiently to pro- appreciably affected the operation of low- pressure device. Therefore, calling duce ionization would result in the the detector. it a "vacuum tube" is not correct. same detector action. At this point it started to become It is important to realize, however, that The best way to obtain a stable de- clear that the Edison effect (thermionic the potential usefulness of the three - tector, de Forest reasoned, was to emission) was involved in the operation element (triode) audion was not imme- place the electrodes in a glass enve- of the audion. Prior to that time, de For- diately apparent. Few besides Lee de lope and heat the gases to ionization est had been convinced that the Forest initially were impressed with its with an external bunsen burner or by ionized gases in the tube were respon- operation as a detector. passing an electric current through car- sible for its behavior. The triode audion was expensive and bon or tantalum filaments. Both heating This single -filament detector, which its filament life was relatively short. The techniques were tried. Lee de Forest de Forest also called an "audion," was bulky and expensive batteries it re- quickly realized the advantages of fila- superior to anything he had used pre- quired were another drawback. In con- ment heating. viously. He received a patent on this trast, the comparatively inexpensive The air inside the envelope was device in the later part of 1906. The fact crystal detectors, developed at ap- evacuated only to the point where the that this Iwo- element audion was vir- proximately the same time, did not re- Fleming's quire batteries. The crystal detectors filament would not be oxidized when tually identical to patented co heated. A sodium or potassium salt was valve was of no concern to de Forest. had added advantages in that they co 43

www.americanradiohistory.comAmericanRadioHistory.Com He merely used the incandescent lamp Edison had modified and patented in 1883 for a new purpose -the detection of wireless signals. Edison's prior patent, together with some very broad claims V in Fleming's patent application con- cerning the rectifying capabilities of B the oscillation valve, made Fleming's 3 `IIIIIIIt- legal position questionable. / As the markets for both Fleming's valve and de Forest's audion were ini- tially relatively small, no resolution of the legal questions was pursued. The Lee IIIII+ de Forest Radio Telephone Company A C, E sold wireless equipment that incorpo- rated grid -audion detectors to the U.S. n_- Navy. It also sold the spherically shaped grid audions for commercial use. The Fig. 5. Lee de Forest's grid audion was the first grid- containing low- vacuum tube. Marconi Company used the Fleming Multiple- electrode tubes were soon to follow valve, modified to include a grid similar to that in de Forest's triode audion, in its were more reliable, simpler to operate, considered to be a relay), Fleming's de- own network of wireless stations. and virtually indestructible. vice could do nothing to increase the In his 1906 patent application, de effective energy of the signals. Amplifiers and Oscillators. In 1911, Forest called the original triode audion The explanation de Forest provided de Forest was hired by the Federal Tele- a "device for amplifying feeble electric concerning how his detector func- graph Company. The company's goal currents." The techniques necessary for tioned differently from Fleming's was of recording high -speed telegraph sig- using it as a true amplifier, however, wrong. Both Fleming's and de Forest's nals for later decoding created the would not be developed for almost six devices were rectifiers, virtually identi- need to increase the energy of the re- years. cal in appearance and operation. The ceived signals. Lee de Forest now battery de Forest used in the plate cir- worked to get the triode audion to am- Patent Problems. Other problems ex- cuit of his audion put a positive bias on plify at audio frequencies. isted for de Forest, too. The Marconi the plate, but was not necessary for its Lee de Forest and his co- workers Company of America owned the pat- operation as a rectifier. Lee de Forest's achieved amplification in 1912 by using ent on Fleming's valve and maintained device was not, in any sense of the audio -frequency to cou- that de Forest's two- element (diode) word, a relay. ple the signal to and from the audion. audion infringed on that patent. Fur- While the legal position of the de For- They also found it extremely beneficial ther, Lee de Forest's triode audion con- est diode and triode audions was not to reduce even further the already low cept was based on his diode audion. very clear, that of the also pressure inside the audion envelope. In Consequently, de Forest's right to man- was in question: Strictly speaking, Flem- time, the audion's spherical shape ufacture and sell the triode audions ing did not "invent" the oscillation valve. would become tubular and the gener- was not without dispute. ic name for this and similar devices, Lee de Forest maintained that the very appropriately, would become the idea for his diode audion came from his Books and Articles. 'Vacuum tube." earlier flame audion, not from Fleming's In the course of developing the am- valve. The records show, however, that "Lee de Forest and the Triode Detector :" By plifier, de Forest found that his circuit de Forest knew about the Fleming valve Robert A. Chipman, Scientific American, oscillated, a phenomenon commonly and had some copies of it made for his March 1965, pp. 92-100. encountered by amplifier builders

own experiments late in 1905. In fact, Saga of the Vacuum Tube; By Gerald F.J. even today. The discovery that the tri- one of de Forest's patent applications Tyne, Indianapolis, Howard W. Sams & Co., ode also could be used as an amplifier 1987. (for what he called a "static valve "), or as an oscillator established it as a filed on December 9, 1905, refers to 70 Years of Radio Tubes and Valves; By John truly important electronic device. Fleming's valve by name. That patent W. Stokes, Vestal, N.Y., The Vestal Press Ltd., 1982. application was filed several months Lawsuits and Stalemate. The Mar- before he applied for patents on his The Continuous Wave: Technology and coni Wireless Telegraph Company of American Radio; By own diode audion. Hugh G.J. Aitken, America sued Lee de Forest and the Princeton, N.J., Princeton University Press, A further claim by Forest was de that 1985. Lee de Forest Radiotelephone and the use of a battery in the plate circuit Telegraph Company in 1914 for in- "The First Electron Tube "; By George Shiers, of his diode audion distinguished it from fringement of its Fleming -valve patent. Scientific American, March 1969, pp. Fleming's valve. He also argued that 104 -112. Lee de Forest and his company filed a Fleming's valve was only a device for countersuit for infringement of their tri- "The Life and Work of Lee de Forest"; (in 14 rectifying high- frequency wireless sig- ode- audion patents Parts), Edited by W.B. Arvin, Radio News, Oc- by the Marconi nals. Lee de Forest maintained that, un- tober 1924-November 1925. Company. like his own audion (which he still (Continued on page 85) 44

www.americanradiohistory.comAmericanRadioHistory.Com MAY 1991

R)

VOLUME 4, A CHRONICLE OF CONSUMER ELECTRONICS NUMBER 5

Getting the Big Picture

SHARPVISION XV -100 LCD PRO- JECTION TV SYSTEM. Manufactured by: Sharp Electronics Corporation, Sharp Plaza, Mahwah, NJ 07430 -2135. Price: $3495.95.

What do you do if you're stuck at a ski house in Vermont fora long weekend with six adults, a bunch of kids, and no snow? You could cope by imbibing prodigious amounts of alcohol. But, if you're lucky, someone in each age group will have smuggled their favorite videotapes in along with their ski gear, and one of the ferent levels of complexity. The projector's Back at GIZMO headquarters, our set - grownups will have brought along a proj- zoom lens allows you to quickly adjust the upgot much more elaborate. The SharpVi- ection TV on which to watch them. picture size. (When the projector is placed sion system benefits tremendously from How, you might ask, could you possibly about 61/2 feet from the screen, the picture association with other high -performance fit a projection- television system in a range is 20 to 50 inches diagonally; at 15 audio and video components. In our test Toyota Corolla already jammed full of feet away, the range is from 50 to 100 setup, we used a stereo amplifier, a Dolby skis, boots, warm clothing, and four days' inches.) The XV -100's smaEl size allows surround -sound system, five speakers, a worth of food, and a couple of skiers? you to set it up in a relatively unobtrusive, Hi -Fi stereo VCR, and a laserdisc player Without too much trouble-if you happen permanent position -for instance, on a along with the SharpVision. Once all the to have the SharpVision XV-100 LCD Proj- shelf, in an audio /video cabinet, or on a assorted pieces were connected to each ection TV. It bears little resemblance (ex- pedestal or table -or to store it in a closet other, however, hooking up the SharpVi- cept, perhaps, in the general price range) when it's not being used. When it's time to sion still required only that one cable be- to either those huge rear-projection sets watch TV, the projector simply can be set tween its video input and the VCR's video with 32- to 52 -inch diagonal screens, or on a coffee table and be connected to the out and, of course, plugging in the AC the standard three -tube front projectors video source with a single wire. (Sharp power cord. The XV-100 has two standard that require precise setups. The LCD tech- also offers a ceiling -mount projector.) Sev- video inputs and one S -video input. A nology, which we'll explain later, is the eral screen options exist. The standard sys- monitor -output jack is also provided to start of a whole new ball game. Weighing - tem comes with a portable, adjustable feed the selected signal to another video in at just over 31 pounds, the XV-100 proj- screen mounted on a tripod stand. Retrac- device (but it won't work with the S -video ector and the cable required to connect it to table wall- or ceiling -mount screens, avail- input). your TV or VCR fit in an optional carrying able in spring- roller or motor- driven The manual recommends that the proj- case that's about the size of a standard versions, can be hidden behind valances to ector be placed anywhere from 6.6 to 15.1 cooler. There's no need to bring along the be virtually invisible when not in use. feet from the screen to obtain proper pic- screen; any bare light- colored wall will do Our ski -house hookup was the most ture focus, to align the height of the lamp just fine. basic: We connected the included cable to with the bottom of the screen, and to set We originally thought of the SharpVi- the VCR's video -out jack and one of the the projector directly centered between the sion's portability as a pleasant perk, but Sl^arpVision's video -in jacks and removed sides of the screen. (Height -adjustment not a very important feature. After all, the large painting hanging behind a couch, screws, or legs, located on the bottom of wouldn't most people want a permanent effectively creating a screen from the now- the projector, let you adjust its height with- installation in their living room or media bare wall. The television, which was al- in a 4° range.) In our tests, we moved the room? ready connected to the VCR via its RF projector to about 18 feet away, set it off to We soon realized that the same features input, served as our (not very high- quality, the side a bit, and had it both higher and that make the projector easy to move and certainly not recommended) audio (Continued on page 7) around also make it adaptable to rooms of source. almost any size, and installations of dif- TURN PAGE FOR CONTENTS

G1ZMO Page 1 45

www.americanradiohistory.comAmericanRadioHistory.Com This Where There's a Will, There's a Month Way In WILLMAKER 4.0 WILL-PREPARATION SOFTWARE. Published by: Nob Press, 950 Parker St., Berkeley, CA 94710. G ZM0 Price: $59.95 No one likes to contemplate his own mortality. We all know we've got to go SharpVision XV-100 Projection TV sometime, but admit it, you'd really rather System pg. 1 not think about it at all. As unpleasant as thinking about death Nolo Press WillMaker 4.0 pg. 2 18M might be, not thinking about it can make IBM life even more unpleasant AT &T Digital Answering for those you leave behind. We're sure we're not the System 1337 pg. 3 only ones who have seen a family tom Instant Replay Caption Master apart as grieving heirs bickered over who 610CM VCR pg. 4 got what when the deceased didn't have a CIRCLE 51 ON FREE INFORMATION CARD will. Unfortunately, the loss of a close FosgateAudionics DSL Two family member often triggers all sorts of Surround Sound pg. 5 grange reactions among the survivors. Nolo Press was founded in 1971 to pub- Besides simple grief, such a loss can shift lish self-help law books to show readers Intermatic Electraguard Surge the entire dynamics of a family. On a con- how to handle routine legal tasks without a Protector pg. 6 scious or subconscious level people tend to lawyer. They started producing software reexamine family relationships, and (in partnership with Legisoft, Inc.) in 1985 Berlitz TriLingual Translator pg. 9 slights and grievances from the past can with the introduction of WillMaker, the come to the forefront again, triggering first program Cordless Video Light pg. 9 of its kind on the market. emotional outbursts that probably WiIlMaker 4.0 is the latest release, and is Home Computer pg. 9 wouldn't occur under any other circum- available for the Macintosh and for the stances. Having no will, or a poorly IBM PC (and compatibles), which is the Home Theater Sound System pg. 9 planned one, is like holding a match to that version we examined. potentially explosive situation -and gives Getting WillMaker up and running Digital Noise Absorber pg. 10 your heirs tangible things to fight over. coulld hardly be easier. It comes on a single Doing a bit of planning while you're disk (both 3 -1/2 and 5 -1/4 -inch diskettes Mega Watchman pg. 10 still alive and kicking might not soothe any are provided in the package) and a manual. of the underlying emotional wounds asso- The manual, Vacuum -Tube CD Player pg. 10 although a hefty 300 pages, ciated with death, but it will assure that actually contains very little information Vegas Dream Video Game pg. 10 your estate will be distributed in the man- about using WillMaker. The first 36 pages ner that you feel is fair. And while it might cover the installation and use of the pro- Day -Glo Cassette Keeper pg. 11 be true that "nothing's certain but death gram. The remaining 14 chapters cover the and taxes," proper estate planning can re- basics of wills and some more weighty Electronic Ace 11 Spelling pg. duce the amount of money that goes to subjects such as how to care for your chil- Uncle Sam upon your demise. dren and their property, how LineMinder Phone-Call to choose an Even people who understand the impor- executor, how to plan to pay debts and Screener pg. 11 tance of having a will often don't get expenses, estate planning, and more. around to preparing. They might not want What do you get when you RACE Remote Key pg. 11 cross a law- to pay lawyers' fees, or they might feel that yer with a Godfather? An offer you can't Dracula's Curse Videogame pg. 12 their estates are not valuable enough to understand. Fortunately, that joke doesn't require a will -even without considering apply to the WillMaker Legal Guide to Interchangeable -Lens the lawyer's fees. Your Will. The book is very well written - Camcorder pg. 12 Will- making kits, consisting of legal even though it's written by lawyers-and forms that must be filled out, have been makes for interesting reading. But you Multi -Room Audio System pg. 12 available for years. While they can be used don't have to read it to use WillMaker. to create a legal will for a minimum of When you run the software, you're NEC -Compatible Joystick pg. 12 money, there's more to creating a will than prompted to enter all the information that's just filling out forms. You need some un- required. Help is available for all questions derstanding Gizmo is published by Gernsback Publica- of the laws, and a source that at the touch of a key, and, of course, the tions, Inc., 500 -B Bi- County Blvd., Farm- will give you answers to the questions that manual can be consulted for more detailed ingdale, NY 11735. Senior Writers: Chris F. are sure to arise. information. O'Brian, Teri Scaduto. Contributors to this Fortunately, there is a way for the aver- WillMaker isn't the slickest program issue: Chris Kerwin, Colin Smeeling, Susan age person with no background in the law we've seen. It runs smoother than an ear- B. Lyons. Copyright 1991 by Gernsback to create a legal will. WillMaker from Nolo lier version we remember, but it still has Publications. Gizmo is a registered trade- Press/ Legisoft makes it easy for anyone to some rough spots. For example, it's rea- mark. All rights reserved. write-and update -a will that is valid in sonable to assume that a husband and wife every state except Louisiana. (Continued on page 7)

46 Page 2 /GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com the sY stem, which k connected to a computer - which appear various messages to help Look, Ma, No controlled milling machine. Once the de- user program the system and the number sign was approved by AT &T, it was time to of incoming messages is displayed once Tape! get all the circuitry inside and make sure it the device is functioning. Below the LED, worked correctly. With a few fine -tuning a curved speaker projects. It is mirrored by adjustments, the inside fit the outside, and a twin speaker on the back of the unit. The 1337. DIGITAL ANSWERING SYSTEM the product -the Answering Sysem top panel of the 1337 is devoted to the most Manufactured by: AT&T, 5 Wood Hol- 1337-was ready for mass production on often used function buttons; of those, the NJ 07054 -289'9. low Road, Parsippary, schedule. blue on/off and play buttons stand out from Price: $139.99. Although digital answering machines the gray repeat, stop, forward, memo, and offer truly impressive advantages over delete buttons. The light in the center of In early 1990, when AT&T engineers standard tape machines, and are still the play button flashes when messages and left first unveiled their newly designed digital - rarities on the market, we can't call have been received. On the right controls for circuitry for a tape -less answering ma- AT &T's Answering System 1337 unique sides of the unit are found chine, compare cv.c.utives were quite im- on the basis of its digital technology alone. those functions that you would tend to set pressed. So impressed. in fact, that tl-cy Its digital circuitry sets it apart from con- infrequently (or even just once), such as decided to spare ne c.spense to speed up ventional answering machines; its truly the security codes, the number of rings the design and manrüàcturing processes so unique, streamlined, vertical design sets it before pickup, and your outgoing an- that the device cord hit the market by apart even from the few other digital ma- nouncement. Jacks for the phone line, Christmas. AT &T hired frogdesign, a chines on the market. power line, and phone set are on the bot- doesn't just high -priced design tau y, ith a reputation We like the aesthetically pleasï:ng, tom of the base. The device for meeting difficult elcadhoes. Late -night space- saving profile of the Answering Sys- look different, it looks good, and it takes brainstorming sessions resulted in a design tem 1337 almost as much as the con- up very little no space. that was directly inspired by a portable venience of all- digital circuitry. A 5-1/2 - As much careful thought and effort went workings of the 1337 as the CD- player that one or the designers had inch square, 1 -1/8 -inch piece rises ver- into the inside turned on its side to save desk space. That tically from an asymmetrical, 21/2-inch- outside appearance. Effectively a high- basic vertical concept was brought to real- deep base. The front of the vertical piece speed computer designed to process ity in frogdesign's computer-aided design has a 2 -digit LED message window, in speech with digital sound clarity, the de- vice digitizes outgoing and incoming vo- cal messages and stores them in electronic memory. By eliminating the need for tapes and all those moving parts needed to play them, the all- digital system promises to be longer -lived and more reliable. The dig- itized voices sound as natural as voices recorded on tape -and never get cut off or dragged out as often happens with taped messages. Digital technology offers several other advantages, most of them in the level of convenience. Just as a CD player imme- diately locates the track you select, as op- posed to manually reversing or fast - forwarding a tape in a cassette player to try to find the selection you want, the 1337 gives you immediate access to the begin- ning of each message. It, for example, you've just listened to the three messages you received while you were out, and want to replay the second, there's no need to sit through the first message again. With AT &T's machine, pushing the play button immediately starts the first message -no time -consuming rewinding. If you don't want to hear it again right now, pressing play again instantly brings up the second message, and so on. If you never want to hear message one again, simply press the delete button as soon as it begins, and it is gone for good. That is especially conve- nient when a whole family depends on one answering machine. Each person can erase their own messages after hearing them without disturbing anyone else's messages. The 1337 will also play only new messages (once that you've never lis- tened to before) when you hold down the play button instead of just pressing it. The digital technology lets you stop on a dime. When you hear an incoming mes- (Continued on page 7)

GIZMO /Page 3 47

www.americanradiohistory.comAmericanRadioHistory.Com Capturing Captions

CAPTION MASTER 610CM CLOSED - CAPTION VCR. From: Instant Replay, 2601 South Bayshore Drive, Suite 1050, Coconut Grove, FL 33133. Price: $795.

Let's face it: Television is such an intrin- sic part of our lives that most of us take it for granted that 24 hours a day, 365 days a year, we can turn on the tube and see and hear our favorite programming. Yet even now, when virtually every home in America has at least one televi- sion set. not everyone has the ability to enjoy that medium. Those who are blind can only listen to the soundtrack. And CIRCLE 53 ON FREE INFORMATION CARD hearing- impaired individuals ate limited to the visuals -unless they have access to closed captioning. Similar to subtitles on a foreign film, captions provide a printed Act of 1990. The bill, strongly backed by when a phone or doorbell rings, a baby version of the dialog in a video show. Cap- NCI, makes it mandatory for television cries, a horn honks, etc. -that might in- tions, however, appear as white letters manufacturers to include closed- caption- fluence the plot or the action. Even the upon a rectangular black background, so ing decoder circuitry in all larger- than -13- lyrics to the theme songs were included, they are more legible than most movie inch -screen sets built after July 1, 1993. preceded by little musical notes. The cap- captions. And sound effects are included NCI is hoping to co- produce such a set tions don't follow the script word -for- along with the dialog, so that a hearing - with an as- yet -undisclosed major man- word, but are gracefully edited when impaired viewer can more fully experience ufacturer, and Zenith (which already man- needed so that the meaning and feeling of the show. ufactures teletext TV's) is planning to beat the dialog comes across, yet the picture Closed captioning has been around for the crowd by offering closed -caption sets isn't obscured. According to NCI, the more than a decade. -Thanks primarily to some time this year. captioning process, which involves view- the efforts of the National Captioning In- In the meantime, there is an alternative ing the program, adding trial captions, and stitute (NCI) -a non -profit organization to hooking up _a separate decoder. Instant then repeatedly editing until all the cap- based in Falls Church, VA, that has Replay has introduced the Caption Master tions accurately follow both the dialog and worked since 1979 to make closed caption- 610CM, a VCR that incorporates an NCI the action, costs about $1500 to $2000 per ing a viable communications medium - closed- caption -decoder module. Elim- hour of programming. The final result is a more than 400 hours a week of broadcast inating the decoder "middleman," the show that provides a full, satisfying view- television (cable, network, and syndicated Caption Master connects directly to your ing experience -without sound. shows) have closed captions. Most of that TV. Two switches on the back of the unit The truly amazing shows are those that programming is shown during prime provide several viewing options. The are recorded -and captioned-live and in time -in fact, the entire prime -time line three- position upper switch allows you to real time. Those include sports events, ups of ABC, NBC, and CBS are closed - choose TV, which is standard television news shows, and talk shows. During a captioned. Inroads are being made in with no captioning; CAP, which also football game, for instance, the sports- daytime programming- including sport- shows the captions on any program that casters' banter appears in closed captions ing events, soap operas, talk shows, and contains them; and TXT, which superim- in between plays. (There are no captions news programs -and commercials, and poses a translucent "blackboard" on while the clock is running.) Those guys NCI has done the captioning for more than which text messages appear whenever they talk fast! Of course, not every word is 2200 home video titles. (NCI is responsi- are sent by the TV station. Not much is on captioned, but enough is there to give ble for approximately 80% of all caption- TXT, except on ABC, which provides a viewers a good idea of what they're say- ing done for broadcast television and 95% programming guide to ABC shows that ing. Live captioning is made possible with of all video -cassette movie captioning.) have closed captioning, and some public an on- the -scene, computer-assisted ste- So, why can't you see any of those broadcasting stations, which provide news nographic machine. A highly trained court captions when you're watching television reports. The two -position lower switch al- stenographer, who has also gone through or videos? A special decoder is required at lows you to switch between two channels, an intensive captioning training program, the viewer's end to extract the captioning Cl and C2, of closed captions. To date, "sits in the hot seat." That person from where it is stored (on line 21 of the virtually all captioning appears on Cl. In "strokes phonetically" . at a rate of 250 vertical blanking interval between pic- some midwestem states, farm reports and words per minute. The computer translates tures, like teletext), convert it into charac- other information of local interest appears the phonetic input to words and transmits ters, and insert those characters into the on C2. For general use, the switches can those words over the phone lines to the video signal at the appropriate time. NCI be left set at CAP and Cl. In that config- television station, where they are broad- makes the only closed -captioning decoder uration, any programming-broadcast or cast to our homes as captions. on the market, and sells it for less than prerecorded -that contains captions will All of that is accomplished with only a $200. The decoder has a few drawbacks, display those captions. 3- to 4- second delay -and no proofread- which make it a less -than perfect solution. Quite frankly, we were astounded at the ing. That can make for some interesting The future of closed captioning looks scope and quality of the captioning. Be- bloopers. On a recent Oprah Winfrey show rosy indeed, however, since the recent pas- sides the dialog, the captioning lets the dealing with sexual discrimination in the sage of the Television Decoder Circuitry viewer in on all the background sounds- (Continued on page 8)

48 Page 4 /GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com Hear and Around

FOSGATE.AUDIONICS MODEL DSL TWO SURROUND PROCESSOR. Man- ufactured by: FosgateAudionics, P.O. Box 70, Heber City, UT 84032. Price: $1299. CIRCLE 54 ON FREE INFORMATION CARD As the home theater becomes more pop- ular, more small- screen TV owners -and these days, a small screen is anything un- logic- steering system that is claimed to be Setting the levels of the front and sur- der 25 inches -are being exposed to the IO to 100 times faster than any other logic round speakers can be tricky without some idea that watching TV can be more than steering -type surround processor. It not sort of reference, and it's rare that two sitting across the room looking at a little only accurately recovers the Dolby Sur- people agree when the setting is correct. box. For example, it's difficult to get round channels encoded on many video- The DSL Two makes the setting easy - through an evening of watching TV with- tapes, it is also claimed to be able to and eliminates the arguments -by provid- out seeing Tommy Smothers brag about accurately recover the directional and spa- ing a pink -noise source. A push of the how he owns the "theater." tial information from conventional stereo Noise Sequencer button sends a pink noise Most people assume that the first st=ep to sources. (That seems like a bit of an exag- signal to each speaker for about two sec- turning their den or media room irto a geration to us. After all, most stereo re- onds to allow for equal adjustment. home theater is to invest in the largest - cordings these days are mixed to the point An Autobalance control can be used to screened TV they can afford. We disagree! where directions and spaciousness are automatically adjust the left and right in- We've found that good sound can do more completely artificial. We do admit, how- put levels to achieve the maximum separa- to make you part of the action than a large ever, that it sure sounds like it's doing what tion between the front and surround screen. Even a 25 -inch TV can come alive they claim!) channels, although a manually adjusted when it's accompanied by a quality sur- Setting up the DSL TWo can be rela- Input Balance control can be used instead. round-sound system. tively easy -but it doesn't have to be. A Buss EQ control provides up to 18 dB of If you've never experienced surround With ten different audio outputs (Left, boost at 40 Hz to the left front, right front, ound, you might think we're exaggerat- Right, and Center Front Channels; Left, and subwoofer channels. Another rotary g. Back a few years ago, we thought that Right, and Mono Subwoofer outputs; Left control, Panorama, lets you adjust the ster- it was all just hype, too. After all, we had and Right Side channels; and Left and eo sage width. The sound can be made to seen several movies recorded in Dolby Right rear channels) your speaker setup seem to come from beyond the front speak- tereo and were less than impressed. can get quite complex -and expensive. ers, or from a narrow area between them. We're still generally unimpressed with the For most of us, however, ten speakers We think that a better name for the DSL quality of the sound in most theaters we aren't necessary. The minimum setup re- Two might have been the DSL Eight be- visit. But the first time we tried surround in quires two front speakers and two sur- cause of the eight different surround our homes, we were very impressed. And round speakers. A built -in amplifier can modes offered. We weren't able to deter- the first time we tried the FosgateSAu- be used to power the surround- channel mine a "best" mode because our prefer- onics model DSL Two, we were even speakers (or it can be used to amplify any ence depended on the source material. ore impressed! two outputs, as chosen with two small Three "Popular" modes are designed pri- The feature we like best about the DSL patch cords on the rear panel of the pro- marily for listing to music, and offer wo is its flexibility. Eight different sur- cessor). slightly different listening perspectives. round modes are provided to best match The other outputs will require separate Two "Classical" modes put you either the audio or video program source. One of amplifiers, and they can be added at any clos to the performers or in the middle of the modes is Dolby Pro Logic, the ultimate time in building -block fashion. We would a concert hall. A Dolby Pro Logic mode in Dolby Surround processing. Unlike recommend adding a subwoofer amplifier is, of course, ideal for movies, and a standard Dolby Surround, which is more and speaker, and front -center amplifier Movie Surround mode promises to-and or less a passive decoding system. Pro and speaker as the logical way to upgrade sometimes does -do an even better job on Logic decoders contain active circuitry - from a 4- speaker system. For very long Dolby- encoded material. Finally, a Mono- known as steering logic-to sense the di- moms, side channels can be added to phonic mode creates synthesized stereo rection of soundtrack dominance and in- eliminate the discontinuity between the surround from a mono audio source. Com- crease the gain in the appropriate channel front and rear portion of the sound field. paring the different modes, and choosing or combination of channels so that the They are truly "fill" speakers, and should the one most appropriate for the source sound comes from the direction that it be part of the final upgrade. you're listening to, is easy because the should come from. Although, by defini- Speaker placement is critical for good supplied remote control can be used to tion, only one sound can be dominant at a surround -sound reproduction. For proper switch from one mode to the next. time, rarely does a movie soundtrack con- reproduction, the sound from the surround We were somewhat surprised that we sist of only one sound. A Pro Logic de- speakers should reach your ears between liked using the DSL Two. We expected to coder, therefore, must be able to time - 16 and 40 milliseconds after the sound enjoy using it with our video system. We division multiplex. That is, it must be able from the front speakers. In small rooms, didn't expect to enjoy using it when listen- correctly steer one source, then give it's difficult to get the surround speakers ing to music. We generally abhor listening attention to the next source, and then the far enough away for That to happen. The to anything that is "mono reprocessed for next, without its switching actions being DSL Two makes speaker placement much stereo" and find that most "enhancers" udible to the listener. easier thanks to the incorporation of Dolby and soundfield processors create effects The DSL Two derives its name from Time Link, which delays the surround that quickly become tiring and that can at what the manufacturer calls Digital Servo channel sound by user- selectable times of best be described as sounding artificial. ogic, FosgateAudionics' proprietary 16. 22, 28, and 32 milliseconds. (Continued on page 8)

GIZMO Page 5 49

www.americanradiohistory.comAmericanRadioHistory.Com can be caused by a number of things, in- The first step is to understand how to Power Happy cluding lightning strikes on power lines, work around potentially dangerous volt- large appliances being turned on and off, ages. On most circuit -breaker boxes there and power-company load switching. Far is a master circuit- breaker. You should ELECTRA -GUARD CIRCUIT BREAKER from being rare, it's estimated that you're start by turning that breaker off. That dis- PANEL PROTECTOR. Manufactured by: hit with more than 5 surges each day! ables the rest of the box (not to mention Intermatic, Intermatic Plaza, Spring Fortunately, most of those surges are rela- your house). Now you can remove the front Grove, IL 60081. Price: $79.95. tively small and don't cause any damage. panel with relative safety. But as most everyone has experienced, Whenever we do any work at our service As much as we like digital electronics. power surges can kill your electronic panel, we stand on a sheet of plywood (to we'll admit that we don't like everything equipment. insulate ourselves from ground) and al- about it. Digital clocks are more difficult Fortunately, there are ways to protect ways keep one hand in our pocket (to elim- to set than their analog counterparts, al- your electronic devices. Here at GIZMO, inate the possibility of creating a current though we guess that their accuracy makes our computers are. of course, plugged into path). For the relatively simple job of in- up for that. Stereo systems with digital surge protectors, as is our main audio/ stalling a circuit breaker, that might seem memory are nice, until the power goes out video system. But we have gizmos all over extreme, but it isn't -it's far too easy to and your memory goes out with it. Those the place! We'd need outlet protectors in make a mistake. (We should know; we problems, however, are more design prob- every room if we wanted to be sure that all make lots of them.) lems than inherent problems. We've seen of our electronics -including our digital When you're ready to begin the installa- some digital clocks that were designed to clocks, answering machines, telephones, tion, you must turn off the main circuit be -and actually are -very easy to set. and microwave oven-were protected. To breaker and remove the trim panel from the We've also seen stereos with battery back- be honest, we live dangerously-or we did panel box. Then you have to remove a up or with some other means of making until now. No. we didn't get a surge pro- knockout through which the protector's the memory non -volatile. There is one tector for each outlet in the house. We got a four wires and mounting stud will pass. problem, however, from which all line - surge protector for all the outlets in the The mounting stud is tightened to the pan- powered digital -electronic devices suffer: house; that is, we got the Electra Guard el with a nut, and the wires are routed to susceptibility to damage from power-line 240RC "Whole- Home" protector. their respective connections. The green surges. The 240RC mounts at the circuit- break- wire goes to the ground bus bar (or to the Power -line surges are momentary in- er panel box and must be connected across neutral bus if your box doesn't have a creases in power-line current. They occur the AC power lines. If yo;i've ever in- separate ground bus), the white wire is too quickly to trip circuit breakers, and in stalled a circuit breaker, you can probably connected to the neutral bus bar, and the the past, they could be ignored. These handle the installation of the 240RC. If two black wires are connected to two sepa- days, however, it's difficult to ignore power you haven't, it might be a good idea to rate circuit breakers. surges because they can cause havoc with have a professional electrician install the Picking the two circuit breakers correct- electronic devices, either destroying them protector, even though the installation is ly is important for full protection. The two outright or reducing their life span. Surges easy -about a 5- to 10- minute job. wires must be connected so that they are across the full 240 -volt AC line entering the house. (Don't forget: Even though res- CIRCLE 55 ON FREE INFORMATION CARD idential service is commonly thought of as 120-volt service, the incoming line voltage is 240 volts. The three -wire service in- cludes a neutral wire, and two lines at 120 volts with respect to the neutral, and at 240 volts with respect to each other.) The manual (a folded sheet of 8' x 11 inch paper) that comes with the surge pro- tector does a reasonable job of explaining how the hookup is done, with one major exception: A figure illustrating how the hookup is done shows the hot wires con- nected to breakers that are on top of one another -that is, on the same side of the incoming line- rather than across from one another. If you install the protector following the step -by-step instructions, WHOLE HOME you'll do it correctly. If you look at the figure, protect only one of the 120 - POWER PANEL you'll volt lines in your house. PROTECTOR When the installation is complete, the trim panel is replaced and the main power breaker is thrown on. If all is well, two LED's on the front of the protector will glow to let you know that everything is working, and the 240RC is ready to absorb any surges that come down the line. Now that those LED's are glowing, we can sleep a little easier at night knowing that all of our devices are protected from power surges. Our computer, however, is still plugged into its own surge protector. Why take chances?

50 Page 6 /GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com THE BIG PICTURE cover that even a four -year-old who had WHERE THERE'S A WILL grown bored with countless viewings of (Continued from page I) (Continued from page 2) The Little Mermaid on a small -screen set found it mesmerizing once again when lower than the recommended height. None played on a projection -TV system. (Tivo- will want to use WillMaker to make their of those factors noticeably reduced picture year -olds tended to be more interested in wills. With WillMaker, it's certainly pos- quality -you do have some leeway in ar- the bright blue light generated by the proj- sible to do that, but it should be easier. ranging the SharpVision system. ector; all the VCR -generation kids, who Instead of assigning a file name to the will Once the projector and screen are in are rarely exposed to movie projectors, got when you start it, the program stores all place, using the SharpVision system a kick out of making shadow puppets on wills under the same name, WILL - couldn't be easier. The main power on/off the wall/screen.) Once the younger kids, DATA.WMK. Of course you can always re- switch is located at the rear of the proj- the mermaids, and the Ninja Turtles got name the data file to create new wills, but ector. The focus ring and zoom ring, lo- put to bed (no one told them that they we'd like it handled more elegantly. One cated at the front of the projector, are could have hooked up their Nintendo to the new feature that we do like, however, is conveniently placed for making the two projection system), the rest of us got the that you can create a text version of the will most -common adjustments. The lamp/ chance to bone up on our skiing skills with for importation to your favorite word pro- power button is located on top of the proj- a couple of how -to videos. Even those cessor for formatting and printing. (You ector, as are lights that indicate power, who'd never made it past the bunny slope can also print directly from WillMaker.) lamp status, and video source. Hidden in- got to experience expert slopes, runs full We had our resultant will reviewed by a side a door on top are less- frequently -used of moguls, and "hot -dog" skiing. And, lawyer who agreed that it met all the re- controls: pairs of buttons for adjusting despite the poor sound, "Jaws" was just as quirements of our state. We're not anxious contrast, brightness, color, sharpness, and frightening shown on a wall in Vermont as to die, but at least we feel that we'd be tint; a reset button that resets to the factory- it was when we first saw it in a theater. leaving things in slightly better order now set picture; the video-source selection but- Steven Spielberg films and projection -TV that our wishes are explicitly stated. In a ton; and the blue screen on /off switch, systems seem to be made for each other. sense, that's too bad-we always enjoyed a which lets you choose whether or not you As always, we have a few complaints. good family fight. want to look at a bright -blue screen when Because the XV-100 has no audio circuitry no video signals are input. The manual or tuner, your hookup must include an offers good directions on how to use each audio source. Chances are, you'll also of those controls to obtain a clear picture. want to add some upscale audio and video And the picture certainly is clear. Sharp components to take full advantage of the LOOK MA, NO TAPE used three Twin -TFT (thin film transistor) system. Granted, the projector itself must (Continued from page 3) active -matrix LCD panels, which deliver a be connected only to a VCR and an AC total of 268,515 pixels and about 300 lines power outlet, but a really good setup re- sage that says "Call me back at ...," you of horizontal resolution, in the XV -100. A quires a lot of wire juggling. The instruc- can hit the stop button while you get a pen specially developed 150-watt metal -halide tion manual falls short when it comes to and paper, hit play again, and the message bulb reaches color temperatures of 90001( explaining setup options. Two diagrams will begin at precisely the spot you and projects clear, bright images. Instead are provided, with absolutely no explana- stopped, "... 555 -5555." (Move quickly, of depending on three separate ray tory text to back them up or even headings though. Should you have a hard time locat- tubes to project three beams of colored like: "Use this setup if you intend to use ing a pen, after 30 seconds the system will light through three lenses (which is how such- and -such A/V equipment with your beep four times and reset itself, and you'll most other projection systems work, and SharpVision." To inexperienced consum- have to hear the message from the begin- which requires frequent realignment of the ers, the diagrams are virtually no help. ning.) beams), the metal -halide bulb's light is Here at GIZMO, where we spend hours Even those relentlessly non -technical separated into its pure red, green, and blue every week connecting and disconnecting consumers who still feel threatened by components by two dichroic mirrors. A electronic equipment, we were able to get phrases like "digital technology" have second set of mirrors recombines the im- our test setup assembled without con- nothing to fear from the 1337. It is quite age's component colors into a single beam sulting the instruction manual. Perhaps simple to hook up, program, and use. As of light, right at the source. The result is an Sharp assumes that if you're laying out soon as the unit is plugged in, it begins to image that is permanently aligned. Three $3500 on a TV system, you either are format its digital memory, with no help LCD panels within the projector take that financially able to spring for installation as from the user. Recording an outgoing an- beam of light and project the image onto well, or are a videophile who can wire up nouncement requires simply holding the screen. Each of the three panels holds components blindfolded. down the "annc" as you speak the mes- 89,505 separate picture elements, or pix- While the thought of carrying around a sage in a normal voice and releasing the els. projection- television system wasn't one of button when you've finished -and the Under ideal conditions-the screen and the factors that originally attracted us to other functions are similarly straightfor- projector properly positioned, watching a the SharpVision system, we've come to ward. The manual includes detailed, illus- laserdisc in a darkened room, with viewers see the practicality of being able occasion- trated directions that are easy to follow. A seated at a distance of about 1' times the ally to bring a projector -one that is sim- quick reference card that can be kept near screen size -the effect is breathtaking. ple to set up and requires no re- the device comes in handy, as does a wal- Once you add surround -sound, an adven- alignment-to the office for a major busi- let -sized card that explains all remote ture movie like Indiana Jones and the Tem- ness presentation. And, while we don't functions at a glance. ple of Doom can elicit gasps and screams normally travel with children or spend The Answering System 1337 provides from home viewers. , much time in front of a TV screen when on the standard array of features-remote op- Under worst -case conditions- watch- vacation, with the SharpVision our snow- eration, a security code, and a personal ing well -worn videotapes in that less weekend was a lot of fun. We realize, memo that family members can use to snow(less) -bound cabin in Vermont, dur- now, that it can enhance family -style vaca- leave messages for each other. A few non- ing the day with no shades on the win- tions. And now that we have the SharpVi- essential niceties are also provided. One is dows, with viewers sitting too close and sion XV -100 fully hooked up to stereo call intercept, which stops the outgoing off to the side of the screen, and with surround -sound, our Super Bowl party message as soon as any extension is lifted, terrible audio -we were delighted to dis- promises to be the best in town! so that you don't have to shout "Wait a GIZMO /Page 7 51

www.americanradiohistory.comAmericanRadioHistory.Com minute. I'm really here!" as the message that doesn't help you when you're out of on- screen programming. It's been quite plays. (If you manage to pick up an exten- town. However, the system still answers some time since we've seen a VCR that is sion at the precise moment the machine the phone, but after ten rings. It won't play as difficult to program- especially in this picks up, as we somehow managed to do the outgoing message or record any new price range. And placing the tiny pro- once, that feature doesn't work.) You can incoming calls; instead, it beeps twice and gramming buttons with even smaller la- let frequent callers know that they can by- waits for further instructions. If no com- bels inside a shadowed, hard -to- access pass the outgoing message by pressing the mand is given, the system beeps once front -panel compartment could make pro- asterisk on their touch -tone phone as soon again and then hangs up. The reason that gramming an impossibility for elderly as it begins playing. And you can set the the system picks up at all when its memory consumers who might have poor eyesight machine to only deliver an outgoing mes- is full is to allow you to use remote com- as well as difficulty in hearing. The bare- sage without taking any messages. Vir- mands to replay, and delete some or all of bones remote control that is supplied with tually every feature can be operated your messages. With a full array of remote the unit operates only the basic tape -play- remotely from any touch -tone phone, in- functions, you can just call in as often as it ing functions. real -time recording. chan- cluding changing the outgoing announce- takes to keep some clear memory on the nel selection, VCR /TV selection, and ment and the security code. machine. power on/off. Are there any drawbacks to digital an- After using a digital answering machine We've become accustomed to VCR's swering systems? The only potential trou- for a few weeks, it seems that those AT &T with certain "perks." We wouldn't expect ble spot we discovered is that the 1337 has executives had astutely recognized that MTS stereo on a unit aimed at the hearing only seven minutes total recording time (in digital technology could be the wave of the impaired, but we would like to see four up to 50 calls) and each message is limited future in the answering- machine market. heads on a $795 unit whose instructions to one minute. AT &T assures us that seven Although it is one of the first machines to include warnings that the captions on minutes is more time than any other digital incorporate digital technology, the An- poor-quality tapes are harder to read. In- answering machine on the market pro- swering System 1337 has none of the stant Replay does offer a four-head Cap- vides. and that their research has shown quirks and kinks that are common in newly tion Master (model 611) -for an additional that the average message length is about 40 introduced consumer goods. It is as func- $200. On the plus side, the Caption Mas- seconds. tional as it is attractive, and provides a fine ter does offer tracking- and picture- adjust- Ever skeptical, we here at GIZMO introduction to digital answering ma- ment knobs, to alleviate the most -common thought the one -minute -per -message time chines. causes of distortions in captions: video limit seemed pretty stingy and the seven noise during playback and pictures that minutes total seemed very brief. Yet we aren't sharp. realized it was difficult to speak to an an- The Caption Master might not offer swering machine -even now that we've CAPTURING CAPTIONS much in the way of features -but it does completely overcome the aversion we felt (Continued from page 4) offer one important feature that no other for answering machines When they first VCR has -closed captioning. And until became popular -for a whole minute. We workplace, Oprah said of a guest, "He closed- caption television sets hit the mar- timed some typical messages. "Hi, this is can't help but stare at a good tush." The ket, the Caption Master is the easiest way Chris O'Brian from Gizmo calling to con- captioned version read: "He can't help but for consumers to access closed -caption firm our appointment for Wednesday at 10 stair - stare at a good touch." In addi- programming. AM. If there's any problem, you can get tion, the computer sometimes has trouble back to me at XXX -XXX -XXXX. Other- translating heavily accented speech, and wise, I'll see you then." (15 seconds) "Hi, might not recognize obscure foreign cities mom, it's me. Nothing special-I'll talk the first time they are encountered. But, HEAR AND AROUND to you later. Bye!" (5 seconds) Even a real overall, the live captioning provides an (Continued from page 5) chatty one -"Hi, Sue, it's Teri. It's 2:00 incredibly fast and accurate interpretation on Sunday, and I guess I missed you again! for those who can't hear. It's interesting to note that we have en- I was just calling to say what a good time Not all closed- caption viewers are deaf, tered an age where sound shaping is just as we had at your house last night. Dinner however. Captioning also provides a valu- important -perhaps more important - was great! Remind me to get your recipe able learning tool for those who are trying than accurate reproduction. Just a very few for barbequed salmon. Oh, yeah, I also to master the English language, and for years ago, any audiophile worth his mon- wanted to let you know that we're thinking children who are just beginning to read. In ster cable would have turned his nose up at of seeing Godfather III next Friday, proba- homes where one individual is a bit hard of the tricks we play with sound, claiming bly the 9:00 show so we can grab a bite to hearing, we're sure that other family mem- that they add only "cosmetic- realism" to eat first. Are you interested in joining us? bers would prefer the relatively unob- audio. For dinner, too, if you feel like it, nothing trusive captions to keeping the volume The DSL Two, however, sounds natural. fancy. Let me know any time before Fri- turned all the way up. (We're thinking spe- Granted, not all of its modes sound natural day, OK? Call me anyway, I really do want cifically about a retired older couple we for all music, but we were always able to that recipe! Thanks again for dinner! know who are difficult to visit because one find one that perfectly suited what we Bye. " -took only 34 seconds. Granted, of them watches TV constantly at full vol- wanted to listen to, whether it was classi- here in New York we tend to speak quickly, ume-making holding a conversation im- cal, rock-n -roll, jazz. or new age. We even but one minute certainly seems sufficient possible.) thought that the Mono Enhance mode did for anyone's needs. Of course, if you The Caption Master brings the world of an excellent job on some old jazz record- co really do have a lot to say, you can always closed- caption video to your home with ings, putting us in the middle of the Onyx E call back and use the next allotted minute very little effort required on the part of the club on 52nd Street listening to the great ¢ to finish up! consumer- besides laying out $795 ($595 Charlie Parker. v We never received the allotted seven for hearing -impaired individuals oreduca- We were also impressed with the DSL minutes worth of messages. either. Had tional institutions) for a very standard Two's performance with our video system, we been away for several days on business VCR. Despite the innovative addition of a as was everyone that we invited to hear it. gor vacation, no doubt we would have used closed- caption decoder, the Caption Mas- Now a few more people really appreciate the 1337's entire memory. When the mem- ter is a throwback to the early days of user- that the TV experience can be more than o ory is full, the message indicator light unfriendly videocassette recorders. The just sitting across the room looking at a flashes rapidly to let you know. Of course, most obvious, and distressing, omission is little box. 52 Page 8 /GIZMO

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

Home Theater Sound System It doesn't matter how large your TV screen is-if it doesn't sound natural, you won't get that movie -house ambience. Ohm Acoustic's (241 Taaffe Place, Brooklyn, NY 11205) Ohm Theater video sound system, which includes two small satellite speakers and a center channel module containing a subwoofer as well as the center-channel speaker, not only provides big sound to support the big picture, but also physically supports the TV set. The center channel module doubles as a TV stand and can be used either vertically, for smaller sets, or horizontally, for large -screen TV's or video monitors. With an optional extension base and panel, it can hold up to 35 -inch monitors. The Ohm Theater can be used with AN systems of any level of sophi tication. For simple, two -channel systems (a stereo VCR or videodisc player and a stereo amplifier), the Ohm Theater's built - in center-channel matrix derives the center-channel audio from the right and left stereo channels. Multiple- amplifier surround -sound systems are accommodated with inputs for a discrete center-channel processor and jacks for additional satellite speakers. The satellite speakers can be mounted on a bookshelf, hung on a wall, or mounted on optional speaker stands. Price: $950. CIRCLE 56 ON FREE INFORMATION CARD

Video Lite Should you find yourself and your mini -camcorder in some less- than -well- lighted places, acordless video light can brighten your pictures. The 20-watt Cell Pack+ Microlite V-0890 from Ambico (50 Maple Street, Norwood, NJ Ohm Acoustics' Home Theater Sound System 07648 -0427) is powered by six included "AA" NiCd batteries that recharge inside the cell pack with the provided recharger. The batteries can also be used to power many 6 -volt, 8mm camcorders for more than 30 minutes, providing a portable back -up power supply. Price: $69.95. CIRCLE 57 ON FREE INFORMATION CARD

Tri- Lingual Translator Should your business or social engagements, or your vacation excursions, take you into international waters, plain -old English might not be sufficient. The Berlitz TriLingual English- Spanish- French translator from SelecTronics (Two Tobey Village Office Park, Pittsford, NY 14534) gives you some help in a couple more languages. Only slightly larger than a credit card, the unit instantly trans- lates 37,500 words and 900 phrases between English, Spanish, and French. The translator is customized with each language's distinct words, characters, and marks. Any other features? Yes, si, oui: It also has a full- function calculator with currency -exchange function. Price: $80. CIRCLE 58 ON FREE INFORMATION CARD Ambico Cordless Video Light

Family Computer Joining the rapidly expanding " home -compu ter - for-the- whole -family" market is Atari Computer's (1196 Borregas Avenue, Sunnyvale, CA 94088)1040STE. It is designed to provide serious home users and small- business professionals with the powerful tools needed for a variety of applications, and a graphics interface provides icons that make it easy for beginners to use the system. The 68000 -based

1040STE, an enhanced version of Atari's 1040ST, has 1 MB of on -board RAM, operates at 8 MHz, and is compatible with thousands of existing ST software packages. The latest TOS operating system resides in the computer's ROM. The 1040STE features an extended color palette, hardware scrolling, and digital stereo sottnd. A 31/2-inch 720K floppy-disk drive is standard, and users have the option of adding a second floppy and a hard drive. The system includes a MIDI port, standard stereo output jacks, and enhanced game-controller ports in addition to standard I/O ports for a parallel printer, modem, mouse, and hard -disk drive. Price: Under $700. CIRCLE 59 ON FREE INFORMATION CARD Atari Home Computer

GIZMO Page9 53

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

Traveling Television Can't bear to miss your soaps while you're at the supermarket? Does your family reunion fall on the same day as game seven of the World Series? Sony Corporation of America (9 West 57th Street, New York, NY 10019) lets you get on with your life without missing any televised action with the FD -555 Mega Watchman personal television. It combines a 41/2-inch (measured diagonally) black- and -white TV screen with an AM /FM stereo receiver and a full- function cassette player in a portable unit. The 13' x 81/4 x 71/4-inch set also provides what Sony calls "surround- sound- enhanced audio" and a one -hour sleep timer. Price: $199.99. CIRCLE 60 ON FREE INFORMATION CARD

Sony Mega Watchman

Digital Noise Absorber One of the unfortunate "side effects" of state -of-the -art digital audio equipment is electromagnetic interference (EMI) caused by digital circuits. TDK Electronics Corporation's NF-0098 digital noise absorber clamps onto signal cables and power cords up to 9 mm in diameter to easily and effectively eliminate sound - muddying interference. The company says that its exclusive high- density "absorbs ultra -high- frequency energy, thereby eliminating the high -range distortion associated with EMI." Price: $10. CIRCLE 61 ON FREE INFORMATION CARD

TDK Digital Noise Absorber

Vacuum -Tube CD Player Something old, something new ... Carver (20121 48th Ave. West, Lynnwood, WA 98036) has "borrowed" old- fashioned vacuum -tube technology for its new CD player (which doesn't happen to be blue). Aimed at "the many audiophiles who prefer the classic sound character of analog vacuum tubes over the exacting precision of modem digital technology," the SD /A -490t linear single -bit CD player uses two high -quality 6DJ8 vacuum tubes. Despite those "antique" com- ponents, the player provides the modern conveniences we've come to expect-24- track programming, remote control, time -edit taping feature, index program- ming, etc. To improve the sound of discs originally recorded in analog and converted to digital, the player also features "Soft EQ," which restores the tonal Carver Vacuum -Tube CD Player and out -of-phase spatial character of the music. Price: $699.95. CIRCLE 62 ON FREE INFORMATION CARD

Gambling Game Move over, kids-Ha/America (7873 S.W. Cirrus Drive #25 -F, Beaverton, OR 97005) has a game for your folks to play on your Nintendo system. Vegas Dream contains roulette, keno, blackjack, and slot- machine games. Players start with a $700 grubstake and have the opportunity- albeit. as slim a chance as in real life - to hit a $10 million jackpot. Besides the actual games, Vegas Dream has assorted "lifelike" casino characters including down -on- their-luck gamblers looking for a loan. We assume there are some more desirable characters as well, because if the players meet "the guy or girl of their dreams" the game offers a Vegas -style wedding. Price: $53.95. Hal America's Vegas Dream CIRCLE 63 ON FREE INFORMATION CARD

54 Page10 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

How D'Ya Spell Suxess? How do you look up a word in a dictionary if you have absolutely no idea how it's spelled? That's not a problem with Franklin Electronic Publishers, Inc.'s (122 Burrs Road, Mt. Holly, NJ 08060) Spelling Ace phonetic spelling corrector. It accepts words typed into its QWERTY -style keypad the way they sound (for example, "ustonushing ") and will display the correct spelling -"astonishing." The portable spelling corrector measures 4 x 2- inches, weighs less than 2 ounces. and comes with a lithium battery and a carrying pouch. The Spelling Ace contains the correct spellings for more than 80,000 words, a built -in list of 1700 commonly confused words, a pattern -matching feature, and several built -in word games. We wonder how it would deal with the "dese," "dose," and "dais" of our native Brooklyn dialect. Price: $39.95. CIRCLE 64 ON FREE INFORMATION CARD Franklin Electronic Publishers Spelling Ace

Roadster Remote Although its primary purpose is to provide remote starting and clin ¡at ization ul your car in the cold of winter or heat of summer, Remote Automation & Control Electronics (RACE) Inc .'s (The Carborundum Center, 345 Third Street, Suite 455, Niagara Falls, NY 14303) Remote Key does everything but drive your car for you. The remote control system will operate the car's rear defogger, power door and trunk locks, horn, and lights. It also acts as a paging alarm system that can be remotely armed, disarmed, and monitored. The two -way radio system allows all control functions to be monitored from as far as 2000 feet away. (That could come in handy if you hang out with the sort of unsavory characters who know how to plant car bombs.) For safety's sake, the device will turn off the car if the emission sensor detects dangerous levels of carbon monoxide from a car idling in an enclosed space, if the engine attains excessive RPM'S, if the hood is opened, or if someone without the ignition key tries to drive the car away. Price: Not Available. CIRCLE 65 ON FREE INFORMATION CARD

RACE Remote Key

Phone -Call Blocker Are you sick of getting phone calls at all hours from people trying to sell you aluminum siding or termite control, or give you the "free" prizes you've won in some contest you never entered? LM Communications Corp. (997 Senate Drive, Centerville, OH 45459) has a solution in the form of the LineMinder, a talking call- screening device that limits access to your phone to those callers to whom you've given the security code. When in its "on" mode, the LineMinder answers every incoming phone call before the phone rings with the message: "Hello, this is LineMinder. Please enter your security code." If the caller enters the proper LineMinder Prone -Call Screener code, the device responds, "Accepted, now ringing." If no code, or the wrong code, is entered, the LineMinder says, "Security violation!" and hangs up- before the phone rings to annoy you. We can think of some other things we'd prefer to say to unsolicited callers .... Price: Not Available. CIRCLE 66 ON FREE INFORMATION CARD

Day -Glo Cassette Storage Fashion -conscious music buffs can now carry their cassettes around in cases that complement their clothing. The Cassette Keeper from Memtek (P.O. Box 901021, Fort Worth, TX 76101) is a sturdy plastic box with a handle for easy carrying that cornes in a choice of "eye- popping" pink. yellow, purple, or green. The neon -bright case can hold as many as 15 audio cassettes. Price: $3.95. CIRCLE 67 ON FREE INFORMATION CARD Memtek Day -Glo Cassette Keeper

GIZMO Page 11 55

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

Multi -Room Audio System The top model in Pioneer Electronics (USA)'s (2265 East 220th Street, Long Beach, CA 90801 -1720) Syscom line is the X9600SBK, which has an "in- line" vertical, twin -woofer speaker design. A multi -play CD player and synchronized cassette deck provide full- function, hands -off continuous taping, extended play- back, and listening options. The multi -play cassette deck offers CD -deck synchro and auto -reverse record and play for six cassette tapes, and automatically rewinds six cassettes in consecutive order. The multi -room feature, when used with an optional infrared adapter, allows an extra set of speakers and system remote control to be added so that all components can be operated from anywhere in the house. The X9600SBK includes an AM /FM tuner, a turntable, and a Dolby Surround -processing amplifier that delivers a continuous average power output of 30 watts per channel. Price: $2,000. CIRCLE 68 ON FREE INFORMATION CARD

Pioneer Multi -Room Audio System Videogame Vampires Any Nintendo player who made it through the first two games in the trilogy with their blood supply intact might want to take a shot at Castlevania 111 Dracula's Curse from Konami Inc. (900 Deerfield Parkway, Buffalo Grove, IL 60089). In this "prequel" to Castlevania 1 and II, the player takes on the persona of "Trevor- Simon's forefather, the origin of the Belmont Warlord Chromosomes," to battle Count Dracula. To travel through 17 possible levels of "Paths of Fate," including haunted ships and cursed castles, the player gets three lives, an assortment of weapons to use, and the ability to "metamorphosize" into any of three spirits. What, no garlic or silver bullets? Price: $49.95. CIRCLE 69 ON FREE INFORMATION CARD

Konami's Dracula's Curse Videogame

Interchangeable-Lens Camcorder Aimed at advanced amateurs, semi -professional videographers, and even the pros, Canon U.S.A., Inc.'s (One Canon Plaza, Lake Success, NY 11042) Canovi- sion 8 LI hi -band 8mm camcorder is the first consumer camcorder to provide interchangeable lens capability. The LI comes with a 15 x zoom lens, and can be used with an optional Canon 8.7- 69.6mm f/1.4 -1.8 8 x zoom lens or with the EOS Adapter VL. That adapter allows you to use any of the lenses designed for use with Canon's EOS series of 35mm SLR cameras. The VL mount system -jointly developed by Canon, Hitachi, Matsushita, and Sony- allows any lenses from those companies that bear the special ``VL" logo (which stands for "video lens ") Canon L1 Interchangeable -Lens Camcorder to be quickly released and attached to the camcorder while retaining full focus, iris, and zoom control with each lens. The LI also offers a variety of creative options for producing special digital effects during recording and playback; automatic controls for focusing, exposure, white balance, and shutter speed; and hi -fi stereo sound. Keep tuned to GIZMO for a closer look at the LI in an upcoming issue. Price: $2,999 for the LI and $350 for the EOS Adapter VL. CIRCLE 70 ON FREE INFORMATION CARD

"Star" Joystick Happ Controls Inc.'s (106 Garlisch Drive, Elk Grove, IL 60007) model 901357 "Star" Joystick is specially designed for use with NEC PC- ENGINE. The joystick has a large chrome -steel handle, a translucent blue base, and two large microswitch fire buttons. Other features include auto fire, slow motion, run/ pause, an extra -long cord, and six arcade- quality microswitches for extra re- liability. Price: $19.95. Happ NEC -Compatible Joystick CIRCLE 71 ON FREE INFORMATION CARD

56 Page 12 GIZMO

www.americanradiohistory.comAmericanRadioHistory.Com Simple VCR Repairs

BY SAM ALLEN

Depending on the malfunction, you might be able to fix your own VCR and avoid an expensive repair bill, or even having to buy a new one. CanDo!

As soon as someone finds out Sizing -Up the Job. Before you commit problem began. That can give you a that you are interested in elec- to work on a unit, there are a few things clue as to what to look for. For example, tronics, they will usually ask you you should find out: First, make sure the if the problem began after the VCR was to fix something. For instance, they machine is out of warranty since you dropped, then you can suspect a might want you to repair a malfunction- will void the warranty if you open the broken circuit board. That is a problem ing VCR. If you are just getting started in case. This is very important when re- that you should be able to find and fix electronics, you probably feel that VCR pairing a friend's machine; sometimes without too much trouble with some tips repair is way over your head. While you people forget they have a warranty, so I'll provide later. might be right to some extent, you'd be make sure it has expired. If a VCR won't load after the kids were surprised how many VCR's are totally Another thing to consider when work- using it, it may have a foreign object disabled by minor problems that even ing on someone else's VCR is the jamming the mechanism; another a beginner could fix. Surprisingly, a VCR owner's attitude. If they are wary and problem you can fix. I worked on one that just won't work at all is usually easier think you may cause more damage to VCR that wouldn't rewind after some- to repair than one that just has poor the machine, don't work on it or you are one had kicked the button with his foot. picture quality. likely to lose a friend if the unit turns out Knowing this, I could center my atten- is, In this article, I will present the repair to be unfixable. If their attitude "Oh tion on the button itself and the prob- techniques you'll need to know to cure well, Ws no good now; you can't hurt it," lem was easy to find and repair. On the some of the most common VCR prob- then go ahead. I like to work on stuff other hand, a problem that appears lems. As you'll come across them more that has already been into a commer- out of the blue with no apparent cause often, the solutions I'll provide are for cial shop for an estimate. If the owner may be harder to troubleshoot. Make front -loading VHS units. However, some decided that the cost of repair is too your decision accordingly. of the problems I'll discuss are common high to make it worthwhile, then they to all types of machines, so the gener- won't get upset if I can't fix it, but they Some Basics. Before gefting into re- alities of the techniques described may are pleasantly surprised if I can. pair procedures, I want to give you a be useful for repairing different ma- Finally, get a good idea of what the few ground rules. The first tip may seem CD chines. problem is; think about (or ask) how the obvious, but before you disassemble a 57

www.americanradiohistory.comAmericanRadioHistory.Com unit, check all of the controls to see that IDLER WHEEL COTTON SWAB

they are set properly. I have had several IDLER UNDER REEL IDLER WITH NON -SLIP people give me VCR's to repair that SPRING TABLE GUIDE SOLVENT only needed to be set up properly. For example, if the unit won't record off the air, the problem may be that the tuning controls aren't set to a station or a switch may be in the "aux" position in- stead of the "tuner" position. Some models may be completely in- operative if a switch is set to the timer position. There are lots of other pos- sibilities, and the more complex the controls, the more likely that one of the controls has been overlooked; so be sure to check out the control settings thoroughly. The next rule on the list: be sure the power cord is not plugged in before working on a VCR. When you do need to make a powered -up test with the Fig. I. A lot of problems can be traced to slipping idler wheels. If your VCR has a guide cover off, be sure to observe every safe- like the one shown here between the reel hubs, it uses an idler wheel. The idler wheel (indicated by the dashed outline) is below the reel table. To avoid a lot of disassembly, ty precaution. I assume you have some apply non -slip solvent to the rubber part of the idler by inserting a cotton swab through electronics background, so you should the hole in the guide. know better than to touch any connec- tions in the primary circuit during such phases of repair. Use a cotton swab moistened with once you have the machine opened There are some rules that apply spe- the cleaner. Don't drip the cleaner onto up, but a slipping belt is hard to detect. cifically to VCR repair. For example, circuit boards or motors. Wipe all sur- If none of the belts are broken try clean- when part of a mechanism seems to faces dry with another swab. After the ing them with a non -slip solvent (for ex- be jammed, the first impulse is to spray clean up, you should relubricate the ample, Radio Shack #44- 1013), then some lubricant on it -don't do it to a gears with teflon grease (Radio Shack test the reel operation again. Inciden- VCR. Spray lubricants cause more harm cat. #64- 2326, for example). Don't use tally, don't overlook the belt that drives than good. More problems are due to a lot; just swab on a very thin film. After the counter; many machines use the slipping than the need for lubrication. the mechanism is working, insert a counter as a sensor in the system -con- Also, while you are working inside a head -cleaning cassette and follow the trol circuit to verify reel movement. VCR, keep your fingers away from the cassette manufacturer's directions for An idler wheel (see Fig. 1) transmits head(s), rollers, and guides in the tape cleaning the head. It provides insur- mechanical power by friction. A rubber transport. Oil from your hands will ance in case any foreign substance "tire" around the edge of the wheel damage the head and cause slipping (cleaning fluid, finger oil, etc.) has got- rubs against the motor shaft and an- in the tape transport system. ten on the head or tape- transport other driven part. If the rubber be- Last, don't randomly adjust things in- components. comes hard, glazed, or slippery, then side the VCR to try and correct a prob- there won't be enough friction for the lem; you will usually end up creating Slipping Transport Components. idler to grip the other parts and turn further problems. Oftentimes the source of trouble is in them. the tape- transport mechanism. Sus- Quite a few VCR's use an idler wheel Foreign Objects in the Mechanism. pect such trouble if the VCR loads a to drive the tape reels. You can tell if In a house with small children, the most tape, begins to play it, and then shuts your machine uses one by looking be- common VCR malfunction is a unit that down; a VCR has sensors and a system - tween the "drive hubs" used to turn the won't load. That problem is usually due control circuit that will turn off the power tape reels. If there is a plastic guide that to a toy or other object that has been if the reels aren't moving. If the system looks like the one shown in Fig. 1, then

pushed into the tape door. I have found control circuit didn't shut down the VCR your machine uses an idler wheel. crayons, pennies, toy cars, buttons, and when a drive component was slipping, To fix the problem, swab the rubber candy inside VCR's. the tape would go slack and get on the wheel with non -slip solvent. To eliminate the problem, remove wrapped around the head, causing Wipe it dry, swab it again, then wipe it the case and look for the foreign ob- major damage. dry. If your VCR is the type shown in Fig. jects inside the VCR. Usually all you If you suspect a slipping belt or idler, 1, you can avoid a major disassembly need to do is remove the objects and remove the case, then insert a tape by applying the non -slip solvent to the the VCR will function. and start the machine. Watch the tape idler by pushing a cotton swab moist- In the case of candy, crayons or the movement. If one of the reels doesn't ened with solvent through the guide like, you may need to do some clean move or is slow and jerky, you need to slot. Turn the tape -drive hub by hand as up. For candy, you need a water -based look for a slipping or broken belt or "idl- you press the swab against the rubber solvent; window cleaner works well. Al- er wheel." on the idler wheel. cohol works for crayons. A broken belt is usually easy to spot Sometimes the spring that pulls on

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www.americanradiohistory.comAmericanRadioHistory.Com the idler has lost some tension. Remove been broken or misalligned. You can inserted upside down or backwards it the spring and cut off a few turns, then usually get it working by bending it back will jam. Even inserting the cassette at a make a new loop on the end with nee- into alignment or gluing the parts back slight angle can cause it to jam. The dle -nose pliers. Re- attach the spring together. If a part is missing, you can solution to any of these problems is to and try out the machine. make a replacement from a scrap of open the VCR case and examine the plastic. It doesn't have to be too ele- stuck cassette. Try to wiggle it around Physical Damage. A VCR that has gant as long as it will depress the switch. and find the place where it is binding. been dropped or abused may have a Sometimes the pushbuttons and the Find the small motor that runs the load- broken circuit board, broken controls, front panel are molded as a single unit. ing mechanism. Gently turn the gear or bent metal parts. The display /control Small strips of plastic act as hinges and on the motor by hand to try to back out board directly behind the front panel is springs. If these strips break, then the the cassette. If the problem is the cas- the most vulnerable. Remove the front button may slip out of alignment or sim- sette itself, then once you get it out, the panel and examine the board, par- ply fall out. You can use silicone glue VCR should function normally. ticularly at the corners. If it is broken, you (such as Radio Shack #64 -2306) to re- Sometimes there is a problem with can sometimes salvage it by soldering attach the button. The silicone remains the cassette basket that will cause a jumper wires across all of the brcken rubbery after it sets, so it will allow tape to jam. For example, inside the traces and replacing any broken com- enough movement in the button to ac- basket there are some springy metal ponents. tivate the switch on the circuit board. fingers that grip the cassette; if they If one or more of the front-panel con- have lost tension, the cassette can slip trols won't work but their functions can Loading Problems. Front -loading backwards as the basket moves. That be performed via the remote, then the VCR's use motor -driven cassette bas- can cause the rear of the cassette to problems may simply be a damaged kets to load cassettes onto their reel get wedged in the loading slot as the front -panel control. The pushbuttons on table (see Fig. 2). An inoperative cas- basket moves down. The solution is to the front are mechanically linked to the sette basket will completely disable a gently bend the fingers to increase the actual switches mounted on the con- VCR. One common problem is that a tension. Too much tension on the fin- trol /display circuit boards. Remove the cassette gets jammed in the basket. If gers or some other cause of friction be- front panel and try operating the VCR the cassette can't be ejected, the sys- tween the cassette and the basket can by pressing the switch located on the tem- control circuit will shut down the lead to the same problem, so be care- circuit board. If it operates normally, VCR. ful when making the adjustment. look at the rear of the front panel to find There are several causes for jam- Some VCR's have a switch that senses out what's wrong. Usually a plastic rod ming. Sometimes the cassette case is forward movement of the basket as a that connects the pushbutton to the warped or damaged in a way that jams signal to start the loading motor. There circuit -board mounted switch has it in the basket. If the cassette has been are a variety of types, but most are leaf switches mounted on the cassette bas- CASSETTE ket. The contacts are supposed to close BASKET P GUIDES when a tape is fully inserted. If that switch is activated before the cassette is all the way in, the tape will get wedged in the slot, so check that switch if the problem persists. Also, check the loading switch if you can slide a cassette into the slot, but the motor that pulls the tape in won't turn on. Some have a small plastic finger attached to the end that presses against the cassette. That finger is prone to break off. Manually close the switch. If the loading mechanism starts, then you probably just need to glue a small piece of plastic onto the end or reposition the switch so it is activated by the cassette. If manually closing the contacts won't activate the motor, try bypassing the switch with a jumper. If that acti- vates the motor, then the switch con- tacts are dirty. Clean the switch with contact cleaner. Don't spray directly on the switch because over -spray will get LOADING GEARS on other components and could cause instead spray a little cleaner Fig. 2. When you insert a cassette, a switch activates a motor that drives the cassette damage; basket. The basket pulls the cassette in and then lowers it onto the reel table. If the on a piece of paper, then rub the pa- loading gears become out of time (slip a tooth), then the mechanism will jam as it lowers per between the contacts of the switch. the basket. If the switch seems to be okay, then

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www.americanradiohistory.comAmericanRadioHistory.Com check out the motor. Some of these motors will run on 9 volts, so (with the power cord unplugged) attach clip leads between the motor terminals and a 9 -volt battery. You may need to reverse the polarity to get the motor to run. If it won't run with the battery, try a 12 -volt supply. If it still won't run, you need to replace the motor. Sometimes you can get the motor working by spraying contact cleaner into the area of the brushes and manually rotating the shaft. If the motor starts to turn then stalls, there is probably something jamming the loading mechanism. Look for a for- eign object, a loose screw, or a bent part. The motor drives a large gear that is connected by a shaft to a similar gear on the other side of the basket. If one of the gears slips a tooth, one side of the basket will jam as the changes basket HORIZONTAL - NC from inward to downward motion. POSITION HEAD The procedure for correcting this ADJUSTMENT problem is called "timing the cassette Fig. 3. This is the A/C (audio /control) head. There are four adjustments: horizontal basket." First mark the present location position, vertical position, tilt, and azimuth. The adjustments affect sound quality and of the gears by making a dot with a felt sync. They also have an effect on picture tracking. tip pen on the Iwo gears at the point where they mesh. Next remove the clip and you can move on to check the to locate a bad component is to start at that attaches the gear to the shaft on secondary circuits. If you get an open - the transformer end of the circuit and the side opposite the motor. Remove circuit reading, make another check take a voltage reading. If there is no the gear and reinstall it offset one tooth with the probes on the terminals where voltage at this point, then the problem from the original position. Try loading a the cord attaches to the board. If you is probably in the transformer. If there is cassette and see what happens; if the get continuity here, then the cord or voltage present, then follow the circuit problem is worse you've moved the plug is bad. and take voltage readings at each gear the wrong way, so try again by If you still get an open circuit reading, component. When you lose the volt- moving the gear in the other direction. look for a blown fuse. There are usually age, you have found the defective If the problem is better but still binds, several fuses at different locations on component or a possible short. move the gear another tooth in the the board. Check them with the ohm- same direction. meter since you can't always tell by Bad Sound or Slight Tracking Prob- looking. If the fuses are blown, replace lems. VCR sound is recorded with a Power -Supply Problems. Most of the them and try out the VCR. If they blow separate audio recording head similar circuit boards in a VCR are too complex again, then there is a short or a compo- to the recording head in a cassette to troubleshoot unless you have a lot of nent is drawing too much current; find recorder. That head also records a con- experience, but the power -supply the problem before you try any more trol pulse on the tape that is used to board is fairly easy for anyone with fuses. If the unit functions normally, it's keep the video head tracking correctly. some basic electronics knowledge. safe to assume that some transient Because of its dual purpose, the head is When the VCR is totally dead, the blew the fuse and the VCR will be all called the audio /control head or A/C power supply is an obvious starting right now. head. If it becomes misaligned, it can point. The power supply can also be If the fuses are intact, check for con- cause distorted sound or sound that is responsible for a number of other prob- tinuity through the primary transformer out of sync with the lip movements on lems. If the supply isn't delivering the winding. If the primary checks out all the screen. Because the A/C head also correct voltages to all of its outputs, right, then power up the VCR and use a controls the picture tracking, adjusting it some systems may not function correct- voltmeter to measure the various out- can be tricky. There are usually several ly while others function normally; so if puts. Some boards will be marked with adjustment screws for horizontal posi- there is a mysterious problem that you voltages. If there are no voltage mark- tion, tilt, azimuth, and vertical position can't explain, check each output of the ings on the board, you need a sche- (see Fig. 3). power supply. matic to do a complete job; but as a If the sound is in sync but it's muffled or

With a dead supply, I like to start by basic test you can check each output distorted, try adjusting the tilt and using an ohmmeter to check for con- and assume it is okay if you get a read- azimuth. Note the original position and tinuity from one blade on the power ing above 5 volts. If one of the outputs is count each half turn as you make the plug to the other. If you have continuity, dead, look for burned resistors or other adjustments. Try the tilt first. Adjust about then the primary circuit is probably fine components in the circuit. A good way one and a half turns one way; if there is

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www.americanradiohistory.comAmericanRadioHistory.Com pear and disappear. Position the head USE so that the sound is in sync and there SCREWDRIVER TO ADJUST are no tracking lines in the picture. Tracking problems that can't be fixed using the tracking control on the front P GUIDE panel can usually be eliminated by ad- justing the NC head. Set the front -pan- el tracking control to the center position, and adjust the vertical and SET then the horizontal position of the head SCREW as you would for audio problems.

Severe Tracking Problems. If there are scratchy white lines in the picture that you can't clear up with the tracking control, and adjusting the NC head Fig. 4. The P guide adjustment affects picture tracking. Loosen the set screw with an doesn't help, then the problem may be Allen wrench before making the adjustment with a screwdriver. with the P guides. The P guides are motor -driven pins that pull the tape out of the cassette and wrap it around the head (look back at Fig. 2 to help locate USE ALLEN SET them). They control the position of the WRENCH TO ADJUST PGUIDE SCREW tape on the head. If they are out of k alignment, tracking lines will appear. There are Iwo P guides; the one clos- est to the supply reel is called the en- trance P guide and the one closest to the take -up reel is called the exit P guide. If the tracking lines are in the lower portion of the picture, then the exit P guide needs adjusting; if they are in the upper portion, the entrance P guide needs adjustment. There are Iwo types of P guides: one that can be adjusted with a screw driv- er (see Fig. 4) and one that requires an allen -head wrench (shown in Fig. 5). Be- fore adjusting either type, you must first loosen an allen -head set screw. Note the pcsition of the guide you want to adjust, loosen its set screw, then insert a tape and play it. Turn the adjustment on the top of the P guide a little and watch for an improvement in the picture. After you have adjusted the P guides, Fig. 5. This typeof P guide needs an Allen wrench for both the set screw and the remove the tape and unplug the ma- adjustment. Be sure to lock the adjustment with the set screw when you are done. chine, then lock the adjustment with the set screw. If you weren't able to cor- no improvement, adjust it back to the lem-do the words begin before the rect the problem by adjusting a P original position then one and a half person opens his mouth? Or does he guide, reset it to its original position. turns the other way. If there is still no open his mouth before the sound improvement, return to the original set- starts? If the sound comes first, then the A VCR that Damages Tapes. Tape ting and try adjusting the azimuth using head needs to move in the same direc- follows a complicated path inside the the same procedure. Watch the picture tion as tape travel. If the sound occurs VCR. When you press play or record, the as you make the adjustments. If white late, you must move the head in the Iwo P guides pull the tape out of the lines begin to appear on the screen, opposing direction. cassette and wrap it around the video adjust the head until the lines disap- The horizontal position is adjusted by head. The tape is held in position by pear making sure that the sound is still turning the large adjusting nut shown in other guides and pulled across the okay. Fig. 3 (the screwdriver is pointing to the heads at a uniform speed by a capstan When the sound is out of sync with the horizontal adjustment nut). On some and pinch roller. Problems anywhere lip movements on the screen, the hori- models, you may need to loosen the along the tape path can lead to tape zontal position of the A/C head needs mounting screws and move the head damage. adjusting. First study a tape as it ploys to slightly. Observe the picture as you The most obvious symptom of prob- analyze the exact nature of the prob- move the head; tracking lines will ap- (Continued on page 88)

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www.americanradiohistory.comAmericanRadioHistory.Com Weather Alert D ecoder

NOAA Weather Radio each time any incoming is a function of the voice happened to hit the National Oceanic operating frequency if it and Atmospheric Admin- weren't for the delay. istration (NOM). The NOM Once U2 is triggered, its service provides the latest pin 3 output goes high and weather information di- stays high for a time deter- rectly from the National mined by R6, R12, and C8 Weather Service offices. (or about three to four min- According to NOAH, about utes depending on com- 90% of the U.S. population ponent tolerances for the is within the broadcasting values shown). range of dt least one of the The output of U1 divides nearly 380 stations oper- along two paths: In one ated in the United States; path, the signal is used to there are even stations op- sound a buzzer, BZ1; in the erating across much of Catch all the latest weather bulletins transmitted other path, the signal is fed southern Canada. by the NOAA with this easy -to -build circuit to the gate of SCR1 through NOM Weather Radio D1 (which helps isolate the consists of a network of FM that alerts you to impending NOAA broadcasts. SCR's gate from the buzzer) stations broadcasting on and R13 (which limits the one of seven frequencies: BY KEITH RAWLINSON SCR's gate current to a safe 162.40 MHz, 162.425 MHz, 162.45 MHz, level). Capacitor C9 is placed across 162.475 MHz, 162.50 MHz, 162.525 MHz, the rest of the circuit, feel free to make the output of U2 to bypass any transition and 162.55 MHz. During severe weather, substitutions to accommodate your re- spikes, which might upset circuit opera- National Weather Service forecasters ceiver. tion, to ground. can interrupt regular programming The incoming signal is capacitively The entire system can be manually and insert a special 1050 -Hz tone (that coupled to the base of Q1 (configured reset at any time by pressing S2. Al- lasts for several seconds), which acti- as a buffer amplifier), which is biased though a single SPDT switch is shown, it vates specially designed receivers prior for a gain of around 2 by R1, R2, and R8. could be replaced by two separate to an emergency announcement. It is The buffer also prevents strong audio pushbutton switches (one normally - that "alert tone" that activates the signals from damaging U1 by limiting open and one normally -closed) if you Weather Alert Decoder described in such signals to the 6 -volt supply level. find the single pushbutton unit difficult this article. The output of the buffer is capacitively to locate. The circuit can be powered Once triggered, the decoder sounds coupled through C2 to pin 3 of U1 (a by any reasonably well filtered 6 -volt a warning for several minutes, alerting 567 tone decoder). The operating fre- DC power supply. Capacitor C3 is in- you to listen to the upcoming message, quency of U1 (1050 Hz in our case) is set cluded in the circuit to provide addi-

and lights an "alert received" LED that by R9, R10, and C4 , and is adjustable tional filtering of the supply voltage at stays lit until it's reset. The decoder can via R9. the circuit-board level. Be advised that be used with any scanner or other re- When the frequency of the signal ap- the 567 is rated for a maximum supply ceiver capable of receiving NOM plied to pin 3 matches the preset oper- voltage of 9 volts DC. Whatever supply weather broadcasts to alert you to a ating frequency of U1, pin 8 goes low. you use, be sure not to exceed that weather emergency. That low is coupled through R3 to pin 2 value. of U2 (a 555 oscillator /timer), triggering Switch S1 provides a means of testing U1 TP1 is Circuit Description. Figure 1 shows a it into operation. At the same time, the the circuit from the output of on. schematic diagram of the Weather low output of U1 at pin 8 causes C7 to a test point to be used later in tuning up Alert Decoder. The circuit -built around discharge through R3, providing a de- the system. two IC's, a couple of additional semi- lay of about 2 seconds. Since the "Alert conductors, and a handful of support Tone' falls within the range of the Construction. Aside from keeping components -connects to your scan- human voice, the system would trigger leads as short as possible, there is ner via a plug selected to mate with the nothing critical about the construction scanner's earphone jack. A resistor (R7), of the Weather Alert Decoder, a connected across the input to the cir- Any correspondence for NOAA Weather printed- circuit board is, however, rec- Radio can be addressed to: National ommended. Figure 2 shows a template cuit, provides a DC load for the scanner. Weather Service (Attn. W /OM11), National The value assigned to that unit (1k) Oceanic and Atmospheric Administration, of the PC -board pattern used by the worked well with the author's equip- Silver Spring, MD 20910 author in the construction of his pro- ment, but since its value is not critical to totype.

62

www.americanradiohistory.comAmericanRadioHistory.Com + 6V 'M R2 C2 R1 4.7K R6 .47 R4 R5 _AA 470K o 10MEG LEDI 470K 33K 3 -AAAr---411 PL1 470 D1 Cl O1 TO TP1 8 1N4002 SCANNER .47 R14 R9 R3 7 270i2 K 3 100K -4 8 U2 VV, 555 R12 R13 R8 C7 1K BZ1 + 470i2 R7 ' R10 U1 2.2K__ R11 10 6 SCR1 7' 1K ' 6.8K 567 22K 2N1595 6 C9 ,M _ C8 - - S2 .1 C4 2 ,22 RESET .1 C5 - C6 h 51 1 2.2 TEST d\

Fig. I. The Weather Alert Decoder is built around two IC's, a couple of additional semiconductors, and a handful of support components. The heart of the circuit is the UI (567 tone decoder), which locks onto any signal within its preset capture range. PARTS LIST FOR THE WEATHER ALERT DECODER

A parts- placement diagram for the Some of the pads and traces in the SEMICONDUCTORS printed- circuit board is shown in Fig. 3. layout are close together, so be careful U1 -567 tone decoder, integrated circuit Note that, in the interest of space, R5, not to bridge them with solder during U2 -555 oscillator/timer, integrated R7, and R11 -R14, as well as D1, are ver- assembly. The circuit can be housed in circuit tically mounted. Also note that C3, C5, any suitable enclosure. Q1- 2N3904 general -purpose, NPN and C6 each have extra mounting silicon transistor SCRI- 2N1595 silicon -controlled holes in the PC board. That's to allow the Setup and Use. Once the circuit has rectifier, or equivalent, see text use of either axial- or radial -lead ca- been assembled and inspected for DI- IN4002 I -amp, 100-PIV, general- pacitors (whichever you happen to construction errors -solder bridges, purpose, rectifier diode have). TP1 can be any piece of wire cold solder joints, and improperly LEDI -Jumbo LED soldered into place and protruding a placed components -it's time to tune it RESISTORS quarter inch or so above the board. up and put it to use. The easiest way to (All fixed resistors are'/. -watt, 5% SCRI can be any SCR a tune is with low the circuit to connect a frequen- units.) enough holding current and sensitive cy counter or oscilloscope to pin 6 of Rl, R4 470,000 -ohm enough gate to operate at the low cur- the U1 and adjust R9 for a frequency of R2-4700-ohm rent levels used in the circuit. 1050 Hz. R3- 100,000 -ohm R5- 33,000 -ohm R6- 10- megohm R7, R12-1000 -ohm R8 -2200 -ohm R9 -5000 -ohm, 10 -turn trimmer potentiometer RIO 6800 -ohm RI I-22,000-ohm R13 -470 -ohm R14 -270 -ohm CAPACITORS CI, C2-- 0.47 -pF, ceramic -disc C3- 470 p.F, 25 -WVDC, electrolytic C4, C9- 0.1 -11F, ceramic disc C5-1 p F, 50-WVDC, tantalum C6- 2.2 -µF, 25 -WVDC, electrolytic C7- 10 -p.F, 35 -WVDC, electrolytic C8- 22 -µF, 15 -WVDC, tantalum ADDITIONAL PARTS AND MATERIALS SI- Normally open, momentary- contact, pushbutton switch S2 -SPDT non -locking pushbutton switch BZI-6 -volt DC buzzer 4tí4 INCHES Printed -circuit board materials, phone plug. enclosure, IC sockets, 6 -volt DC Fig. 2. While there is nothing critical about the construction of the Weather Alert power supply, wire, solder, hardware, Decoder, it is recommended that the circuit be assembled on printed- circuit board. Here etc. is a template of the PC -board pattern used by the author.

63

www.americanradiohistory.comAmericanRadioHistory.Com Z -°S1°1 c's _

+ , Ç R11 R8 f17 IC5 I I + C4 PL1 BZ1 Cl C2 C9 U1 1112 FÌ5 ± CS- PL -R1- TO 0144 SPEAKER R2 R10 SCANNER R4 R6 R13 63 R9 R3 Fig. 4. The buzzer can be replaced by a reed relay provided that your receiver's +6V R14 SCR1 output jack can drive a speaker directly, thereby allowing you to listen to the LEDI warning message.

TO OUTPUT OF DECODER Fig. 3. Use this parts -placement diagram as a guide when assembling the Weather Alert Decoder's printed- circuit board. Note that R5, R7, and RII -R14, as well as DI, are 1N4001 have extra mounting holes to allow the 470 vertically mounted, and that C3, C5, and C6 each TO use of either axial- or radial -lead capacitors. SCANNER °---)

10K If a scope or frequency counter is not write to NOM at the address given available, a signal generator can also elsewhere in this article you can find be used with only slightly more difficulty. out when the tests are broadcast. Con- 1012 First, solder a 470 -ohm resistor to the nect an LED to TP1 as described above rir cathode of an extra LED. Then solder a and wait for the test signal. During the wire to the LED's and connect test, quickly plug the unit into your re- TO DECODER supply. Then, R9 until the LED at TP1 the other end to the plus ceiver and rotate OUTPUT connect the remaining lead of the 470 lights. If you fail to get it before the test SPEAKER ohm resistor to TP1. Setthe signal gener- ends, you'll have to wait for the next test Fig. 5. If your receiver's output can't ator to 1050 Hz at about 0.1 volt and time and continue from where you left drive a speaker directly, this circuit will connect it to the input of the circuit. off. enable you to feed the receiver's output to Finally, with R9 fully counterclockwise, Once set up, the circuit will monitor a speaker. rotate R9 slowly clockwise until the LED the NOAA broadcast until the alert tone at TP1 just lights; then, rotate R9 another is sent out, and sounds the buzzer for Troubleshooting. If the LED indicator 3/4 turn. several minutes before resetting; the comes on, but goes out without being If you're really a glutton for punish- LED stays on until reset to inform you that reset, try placing a 470 -ohm resistor ment, the circuit can be set up without an alert went out. Holding the TEST from the SCR anode to the LED anode. If any extra equipment. NOAA weather button down for about two seconds will the LED doesn't come on when the radio often broadcasts a test signal at set the system off manually, so you can buzzer sounds, make sure that D1 is certain times during the week; if you check it. properly installed, then try reducing R13 to 270 ohms. If the buzzer doesn't time out after five or six minutes, try replacing C8 with the highest quality tantalum capacitor you can find. Bear in mind that any noisy signal with a lot of hiss may trigger the decoder constantly.

Modifications. If your receiver output jack can drive a speaker, you can re- place the buzzer with a reed relay as shown in Fig. 4. Instead of a buzzer, the speaker will be activated so that you can listen to the warning message. If the output jack can't drive a speaker, try replacing the buzzer with the circuit in Fig. 5 to add the additional boost 01 U2 R9 needed to drive the speaker. With a little imagination, this circuit Here is the fully assembled printed -circuit hoard prior to being mounted in its enclosure. Note that five resistors (R5, R7, RII, RI3, and RI4) and diode DI are vertically mounted could be put to other uses. Just experi- to the board. ment and have fun.

64

www.americanradiohistory.comAmericanRadioHistory.Com THE LASER PC4 PORTABLE COMPUTER CIRCLE 119 ON FREE INFORMATION CARD

If you need a high -powered number cruncher or database that can follow you wherever you go then check out this model.

It seems as if the majority of people processor with spelling checker; Lotus - make access simple. Little things, like today, in our techno -raptured so- compatible spreadsheet; expense ac- having a raised dash on the top of the F ciety, believe that "more is better." count; calculator; BASIC programming and J keys, and slightly wider major In the computer world this has led to language; telephone directory/dialer; function keys, make it easy to touch - enormous complexity where simplicity appointment book; personal file; alarm type with the PC4 keyboard. should prevail. The Laser PC4 offers a clock and various utilities (including file refreshing reversal to this trend. For only transfer). More on each of these later. Some Controversy. Two things make $250 you can now have a small, light, Three cables are provided. One 6- the PC4 controversial in today's market- portable computer that boasts a full - foot cable is for direct connection to a place. The first is compatibility. The PC4 size keyboard and many conventional Centronics -parallel printer port; an- is not in itself compatible with any other functions. other 6 -foot cable is for file transfer to a computer. However, using the included The PC4 is not intended to be your computer serial port; a third short cable cables and software, it can transfer files only computer, but an off-site accesso- is provided as an adapter between S- to and from other machines. Even

ry to your desktop computer. It provides pin and 25 -pin serial ports common on though I tested the IBM PC version, I had for simple file transfers and printouts. IBM PC computers and compatibles. no trouble at all transferring word - Instead of being limited to use only with An AC power adapter is included, but processing files to a TRS -80 Model Ill or the IBM PC, versions are also available you can make the PC4 portable for model IV! for the Apple II series and the Macin- about 40 hours of operation with four The PC4's 15 -pin output connector tosh. Actually, the PC4 itself is the same "AA" cells. Those same batteries keep acts as either a serial or Centronics - for all versions, but different accessories your program files and data in memory parallel port, depending on your com- are included to offer compatibility with for up to six months, depending on use. mands. As a serial port, it seems to con- the target desktop or laptop. This report A very nice soft padded-vinyl zippered form to RS -232C standards. Using the is of the IBM PC version. carrying case is also included. Actually, serial cable supplied with the PC4, I up- you don't need to buy anything but the loaded to my TRS -80 using a standard Small, But Complete. Smaller and four "M" batteries-and those are only terminal program, saved the resulting lighter than most laptops, and certainly needed for portable use. file on disk, and used the file in my reg- a lot less expensive, the PC4 measures The full -travel typewriter -style key- ular TRS -80 wordprocessor program for 7.6 inches by 10 inches, and is only 1.6 board is a pleasure to use. It has 57 keys, cleanup and final formatting. That has inches thick. It weighs less than 2 with special keys colored gray and reg- freed me from having to work where my pounds. Unlike many laptops, where it is ular keys black. It has a solid feel, and is desktop computers happen to be- necessary to buy additional cables, a very quiet, yet offers an optional usually the hottest or coldest locations! carrying case, a power adapter, and "beep" for each keystroke for those The other controversy has to do with software, the Laser PC4 comes with ev- who like the audible feedback. Many of displays. It seems to most users that any erything you need. the keys have dual or triple functions, display with less than 80 characters on Its built -in 2 megabytes of ROM has but the CAPS LOCK and NUM LOCK keys, to- a line, or 25 lines, is crippled. Perhaps the following programs: powerful word- gether with color -coded legends, because of my satisfactory experience 65

www.americanradiohistory.comAmericanRadioHistory.Com with smaller computer displays (as little load it back into the PC4 or use it (if storing a result in one of the memories. as two lines with only 20 characters saved without formatting) as a generic For printouts, use the spreadsheet. each I'm less biased than many. text file. In order to load a file into the But what about programming in

The PC4 offers a bright, sharp LCD PC4 from a computer, however, it must BASIC? I found at least 50 reserved readout of 4 lines with 40 characters on first have been created and saved words used by this version of BASIC. All a line. I did not find this very limiting at using the PC4. the most common words and typical all. If you are suffering with the 80 x 25 With over 80,000 words in memory, strings functions are supported. Multi- syndrome, however, you'll need to ac- the spellchecker can be accessed by ple- character variables can be used, tually use the PC4 display before you itself, or from within the Word Processor. and various trigonometric and log- believe how adequate it is. Incidentally, You type in the word the way you think arithmic functions are included. Sur- the PC4 display is perfectly clear even it's spelled and the correct spelling (usu- prisingly, I could not find any support for in direct sunlight, unlike some LCD lap- ally with several alternatives, if you've even simple arrays. Most of the key- top computer displays I've seen. entered an incorrect spelling) is dis- words are directly accessible with ark

played. For example, I typed in "spel- key combinations, saving a lot of typ- Documentation. In addition to all the ing" and got spelling, spewing, ing, and full- screen editing is allowed. cables, the power adapter, and the spellings, spilling, speaking, spearing, You can LPRINT and LLISTto a printer, but carrying case, the PC4 comes with specking, speeding, spending, splint, I was unable to save a PC4 BASIC pro- some excellent documentation. For spooling, spring, spying and swelling as gram to another computer. Ten dif- transferring files, an appropriate file - possible choices! ferent BASIC programs can be saved in transfer program is provided. With the The spreadsheet is by far the most memory at the same time. IBM version, for example, you get a spe- elaborate program built into the PC4. The telephone directory/auto dialer cial version of "PC Tools Desktop Man- By its very nature and size (256 columns, is a mini -database for names, ad- ager Version 5.5," a program that by 8192 rows for a total of over 2 million dresses, phone numbers, and a one - normally sells for about $100. It comes cells!), this Lotus -like and Lotus -corn- line note. You can add, search, change, complete with a 312 -page manual patible electronic worksheet will take delete, or list entries, and send output to and two 360K, 5.25 -inch floppy disks to some time to learn to use unless you're a printer in any of Iwo page formats or use with any IBM PC or compatible. The already "spreadsheet literate." The dis- two mailing -label formats. You can also telecommunications module of PC play only shows three cells across and tone dial using a built -in speaker. Tools has been revised to add special Iwo high at any one time, so this is By using the built -in appointment file- transfer capability for the PC4. where the limited display is at its great- book, you can list your appointments You also receive four othei' pieces of est disadvantage. A "Range" corn - and print them out in any of two printer excellent documentation with the PC4. mand lets you navigate quickly around formats. You can also set an alarm for The "File Transfer Guide" covers the up- the spreadsheet, and macros are sup- each appointment. loading and downloading of PC4 files ported to eliminate repetitive keying. The personal file is like a collection of with your PC, using the special PC Tools You can copy and move cells and re- five -line cards for storing personal infor- transfer program. The "Ten Minute Tour" trieve, erase, or sort files. Support is pro- mation, such as credit -card numbers, takes you on a brief trip through each of vided for many financial, statistical, and insurance -policy numbers, recipes, or the PC4's built -in programs, while the date functions. You can send all or part other notes. Password protection is pro- "User's Manual" is handy for reference of a spreadsheet to a printer, or upload vided. The information in this file can be to details. Help screens are available it directly to a Lotus -compatible pro- sent to the printer in two different page within the PC4 for each program, and gram on your computer for further ma- formats. the single -sheet two -sided "Quick Ref- nipulation. With the proper procedure, Using the alarm /date clock, up to six- erence Guide" shows all the important you can download spreadsheet files teen alarms can be set as friendly re- commands for all the programs. from your computer to the PC4. minders of important events. The The expense- account program al- alarms can be daily or weekly, and in- Programs. It would take a book (after lows you to record personal and busi- clude the Appointment Book alarms. all, the User's Manual is 278 pages) to ness- related expenses. With seven built - Last, there are software utilities. These explain all the features of the PC4's in categories like "Lodging" and "Trans- programs allow you to set serial transmit built -in programs, but here are the portation," and subcategories, you can and receive parameters, configure the main points of each: easily sort your expense records for unit for different printers and ports, look The word processor has most of the quick reference. You can add, review, at a memory map, erase files, or look at features you've probably come to ex- change, and delete entries, catego- help files. pect, except block -copy or moves. Text ries, or subcategories, and print a daily The built -in 32K RAM can be up- is automatically word -wrapped on en- or weekly report for any or all catego- graded by popping out the 32K RAM try. You can search and replace text, ries. chip and replacing it with an optional spell -check individual words or the en- With ten memories and seven scien- 128K RAM chip ($40.) There is also an tire document, and provide detailed tific functions, the calculator permits expansion slot for optional cartridges. page formatting with 22 "dot com- you to perform a wide range of busi- The Roget's II Electronic Thesaurus car- mands." You can even specify headers ness and household calculations. You tridge with 500,000 synonyms ($45) is and footers. Files can be dumped di- even have the option of converting be- presently available, with medical and rectly to a printer without transfer to a tween decimal and hexadecimal num- legal dictionary cartridges promised. computer, or you can transfer the text bers. However, I was surprised that none I found the PC4 extremely friendly file, with or without formatting, to your of the calculations can be sent to a and forgiving, and capable of doing a computer. You then save it on disk and printer or saved in any way, except for (Continued on page 85)

www.americanradiohistory.comAmericanRadioHistory.Com PRODUCT TEST REPORTS

By Len Feldman The Toshiba M -441 video unit for timer recording. All behind a drop -down recorder is a VHS -for- of the on- screen functions hinged panel that runs the mat model that are controlled by means of full width of the unit. With incorporates many features a supplied remote -control. this panel in its closed posi- found only in more expen- This VCR uses a quick - tion, only the power switch, sive units. Its frequency - access system that enables an eject button, the cas- Toshiba synthesized tuner section you to switch operating sette slot, and the display automatically selects any of modes rapidly. For example, area are visible. Dropping M -441 Video the up to 181 VHF UHF or a conventional VCR needs down the hinged panel re- cable -TV channels receiv- between 8 and 10 seconds veals the usual tape Cassette able in your viewing area. to switch modes from play transport and record con- Extensive timer -record pro- to rewind. With the quick - trols, a speed selector Recorder gramming 8 events over a access system, the same button (the unit records at period of 1 full year -is pro- operation can be accom- either the SP or EP speeds, vided, as are such special plished in from 2 to 3 but can also play back effects features as frame - seconds. This function can tapes recorded at the LP by -frame viewing, still -frame be used for both playing speed), a 1VNCR selector viewing, and picture search and recording. In fact, this switch, channel -up and - at either 5 -times normal VCR starts recording almost down buttons, and video and audio input jacks used for recording from an exter- CIRCLE 120 ON FREE INFORMATION CARD nal source such as a camcorder, a TV monitor/ receiver, or another VCR. When connection is made to this front-panel video - input jack, the line input rather than internal tuner is automatically selected as the program source to be recorded. The Toshiba M-441 VHS VCR. Virtually all of the special - effects mentioned earlier as viewing speed or at 7 -times immediately after the rec- well as all timer program- normal speed in the SP ord button is pressed. ming is accomplished using tape -speed mode, or 21- When a cassette is load- the infrared remote control times normal viewing ed into the tape slot, power rather than front-panel but- speed in the EP tape -speed is turned on automatically, tons. Direct channel access mode. One -touch instant and if the tape's safety tab is also possible only via the recording within a period of has been removed (as in remote. 24 hours is also easily pro- the case of a prerecorded The front-panel display grammed. tape), playback begins. At area provides channel - On- screen menus are the end of such a tape's number indications, current used for setting correct play, it is automatically re- tape speed, clock time, dock time, initial setup of wound and ejected, and and remaining tape-time antenna and automatic the power is turned off. indications in addition to a channel selection, auto re- Pressing the eject button, wide variety of status dis- peat -play of a tape, index even when power is off, will plays. The rear panel of the marking and searching, eject a tape. M -441 is equipped with the and edit dubbing. Other usual coaxial RF -input and - menus guide the user, step CONTROLS output tacks, audio- and by step, through the pro- Most of the M -441's oper- video -output jacks, and a cedure used to set up the ating controls are hidden channel -3/ -4 switch. 67

www.americanradiohistory.comAmericanRadioHistory.Com TEST RESULTS pensive VHS VCR is its on- As in previous video - TEST RESULTS -TOSHIBA M -441 VCR screen menu system. A product test reports, all lab- Specification PE Measured study conducted by a Video frequency response oratory performance noted research At 2.0 MHz -3 65 dB organiza- measurements were made At 3.0 MHz -17.8 dB tion revealed that an by the Advanced Product (See text regarding response in Edit mode) astounding 80% of the Evaluation Laboratory Video signal -to -noise ratios people who own VCR's Chroma AM 42.0 dB (APEL), under the direction have never even used the Chroma PM 38.5 dB of Frank Barr. The results of Luminance, 100 IRE reference 42.3 dB unit's timer -recording ca- these lab tests, along with Luminance, 50 IRE reference 42.7 dB pability. An almost as great the sample actually tested, Luminance, 10 IRE 41.1 dB percentage of VCR owners were then sent to our lab 0 -dB audio reference level 0.5 volts have never bothered to set level 1.31% where further THD at 0 -dB audio reference the subjective THD at -10 -dB reference level 0.33% correct time on the testing and hands -on eval- Audio frequency response 230 Hz to 13.5 kHz VCR's clock display. Toshiba uations were done. As has Additional Data has simplified those tasks been APEL's practice in the Power requirements 21.0 watts considerably with their on- 13.0 lbs past, all measurements Weight screen menu system. Fast-forward time (T-120 tape) 3 min. 21 sec. were made at the faster SP Fast - rewind time (T-120 tape) 3 min. 17 sec. In our hands -on evalua- tape- speed, since that Dimensions (H x W x D, inches) 3% x 1415/,8 x 131/2 tion of picture and sound speed yields the best per- Suggested price: $389.95 quality, we found that color formance. If you use this reproduction when playing machine at its slower EP back a recording made on speed (for a maximum of 8 perhaps just slightly below ratio for the audio track this machine was quite hours of recording time average for this basic type measured 46.2 dB, which is good and background using a T-160 tape), you can of video recorder. The sig- again about average for noise levels were accept- expect both video and au- nal -to -noise ratio for the monophonic linear edge able, if not superior. The dio performance to be luminance, or brightness track audio recording on a quick -access feature de- somewhat poorer than the portion of the video signal standard VHS VCR. While scribed earlier really does results obtained in APEL's measured between 41.1 the low- frequency response cut down the time required tests. and 42,7 dB, depending was poor (down 3 dB at to get into the record The video -frequency re- upon the reference lumi- 230 Hz), treble response mode or, for that matter, to sponse at 2.0 MHz was off nance level used when was much better than aver- activate any of the other by some 3.65 dB, which is making the measurement. age, extending to 13.5 kHz tape -transport functions. about average for a basic The audio recording and for the -3 -dB cut-off point. Still -frame viewing was ac- VHS recorder of this type. At playback performance of All of the video and audio complished with a 3.0 MHz, the response had the VCR was also mea- measurements made by minimum of noise streaks. dropped to -17.8 dB. sured. The output for a 0 -dB APEL are summarized in the The owner's manual is When in the edit mode, reference level was 0.5 volts table that appears well written, though it does however, frequency re- at a total harmonic distor- elsewhere in this report. apply to four models by sponse improved tion level of 1.31%. At -10- Toshiba; though the dif- somewhat, so that at 2.0 dB levels, distortion de- HANDS -ON TESTS ferences between those MHz it was down by only creased to 0.33 %. A- By far the best thing are minor, you will need to 0.75 dB, and at 3.0 MHz it weighted signal -to -noise about this relatively inex- be sure that you are refer- was down by only 1.75 dB. ring to instructions for the That mode is used when aftAT. A as correct model to avoid ..... t.n VA - copying tapes from one ...=J.__...... -- 131% confusion. An antenna ca- machine to the next and ble is provided with the unit, --SY the added response en- SO but if you want to make sures that there will be less direct audio or video con- 66 37.5% degradation of picture 1?11111111 nections to other video quality on the copy than equipment, you will have to might otherwise be the purchase your own case. shielded audio /video con- APEL measures color sig- necting cables. If your TV- nal -to -noise ratios in two antenna transmission line is ways: with respect to AM 1'1 I00at 1'' of the 300-ohm type, you (amplitude modulation) will also have to purchase a noise and for PM (phase 75 /300 -ohm transformer. modulation) noise. In the For more information on case of this recorder, AM the M -441 VCR, At 2.0 MHz, the video frequency response lras off by some 3.65 contact chroma noise measured an dB, which is about average for a basic VHS recorder of this type. Toshiba (82 Totowa Rd., average 42 dB, while PM At 3.0 MHz, the response had dropped to - 17.8 dB. The Wayne, NJ 07470) directly, noise measured 38.5 dB. frequency response of the VCR improved somewhat when the unit or circle No. 120 on the That is about average, or was in its edit mode. Free Information Card.

www.americanradiohistory.comAmericanRadioHistory.Com ANTIQUE RADIO

By Marc Ellis In the February, 1991 issue, suggested methods for Like everyone who en- we presented the sche- modifying and calibrating tered but didn't win, Dave matic diagram for a tube voltage and current meters gets a warm thank -you and

tester I call "The Cun- for use in the instrument. an honorable mention for ningham Special." The Though February's sche- his submission. And we'll be name came from the fact matic was thoroughly back with more on the Operating The that the tester was adapted tested breadboard -style Theremin story next month! from a (1920's vintage) de- and proven to be reliable, I Cunningham sign by the engineers of the hadn't yet built a complete, TUBE -TESTER E.T. Cunningham tube com- finished prototype of the CONSTRUCTION Special pany. Previous issues of the unit. This month, we'll con- Most key constructional column (September, Oc- clude the tube -tester series details on The Cunningham tober, and December, 1990; by giving you a look at the Special have been covered January, 1991) had de- now -completed instrument in earlier issues (especially veloped the theoretical and talking about how to December, January, and basis for the tester, worked operate it. February). However, here out modern methods for are a few points relating to supplying and regulating fil- ONE MORE the prototype shown on ament and plate voltage to HONORABLE MENTION! these pages. the tube under test, and But before we get into The Cunningham Special The Cunningham Special, is built almost completely of there's a bit of unfinished standard parts, but the business from last month's cabinet is one exception. Ifs column. Last month, you'll a neat sloping -front ham -

recall, I honored the en- mertone -gray job (Bud

trants to our recent C- 1587 -H.G.) that I picked Theremin contest. In that up at a hamfest flea mar- contest, readers were en- ket. You'd have to be lucky couraged to send in to come across another technical and historical in- one like it, but it doesn't formation on the RCA matter. Exercise your inge- Theremin a vintage elec- nuity and use whatever tronic musical instrument type of enclosure suits your from the late 1920's. fancy; the layout is not at all Eight of the over 40 en- critical. trants received a reprint With the particular cab-

copy of the interesting inet I used, it seemed 1920's -era Gernsback pub- natural to put the tube - lication, 100 Radio Hookups, socket array on the top but everyone's contribution cover and the control and was acknowledged in de- metering circuitry on the tail. Everyone's, that is, but front panel. The power-sup- David Ballinger's-which ply components were was accidentally omitted. installed within the cabinet Dave (who hails from Mr- with plenty of room to ginia Beach, VA) sent along spare. To give you a better a dub from the Clara Rock - feeling for the layout, I've more CD The Art of the marked all visible compo- Theremin (see last month's nents with their column for a discussion of designations from the Feb- that fascinating recording, ruary, 1991 schematic. which is still available in Of course, the tube sock- record stores) and also ets themselves aren't passed along some child- standard components ei- The Cunningham Special makes a neat package in its vintage hood memories of a ther. The whole point of this sloping cabinet. Old -style round meters heighten the Thereminist who performed tester is that it has been front cá antique effect. at his grammar school. designed to accommodate CD

69

www.americanradiohistory.comAmericanRadioHistory.Com make sure it's in the LO ment), you should also S01-a position. Now place switch open FIL RESISTOR switch S8, 510 in the LINE position, which inserts resistor R6 into make sure that the CURRENT the filament circuit. That SO2 RANGE switch S6 is set for the drops the voltage an addi- lower current range (which tional tenth of a volt or so, is the normal testing posi- though its effect will not be tion), and rotate the LINE seen until the tube is ADJUST control (DIM1) until the plugged into the socket.

S05 needle of meter M1 rests on If I seem to be splitting the reference mark you es- hairs by worrying about a S4 FILAMENT tablished earlier (see the tenth of a volt, it's because VOLTAGE February issue). the types 11 and 12 are M2 ADJUST If the tube is a type 80 or quite costly, difficult to ob- 81, test procedures will be tain, and easy to damage! S7 covered later. For all other For all other types of tubes, tube types handled by this resistor R6 is not needed, S9 tester, you should now set and switch S8 should be the filament voltage to the kept closed. NE1 value shown in Table 1. To If you can't obtain a high do that, set the VOLTAGE -RANGE enough filament voltage for switch, S9, to the lowest the tube to be checked, S1 range that will handle the move switch S2 to the HI required voltage. Then ro- position and try again. But tate the FILAMENT VOLTAGE ADJUST to avoid unnecessary load S2 DIM1 S8 control (the potentiometer on the The tester's front -panel and top -cover layout. Part designations in the voltage -regulator cir- circuit, leave S2 on Lo refer to the schematic diagram in the February, 199/ column. cuit discussed in whenever possible. December) until the correct With the voltage set cor- tubes with archaic and ob- They're not at all difficult to value is indicated on meter rectly, you may now insert solete bases. To acquire the find at surplus dealers and M2. the tube to be tested into needed units (particularly electronic flea markets, but The minimum voltage you the proper socket (see Ta- the ones in the back row), you certainly won't be able will be able to obtain with ble 1 and the schematic in you'll have to do a bit of to walk into a Radio Shack that control is approximate- the February column). If the scrounging at electronic and pick one up! ly 1.2 volts. So if the tube is a tube has a top grid con- flea markets. I found mine The only other unusual type 11 or 12 (1.1 -volt fila- nection (types 22, 24, or at an Antique Wireless Asso- (by modern standards) part ciation meet. worth mentioning is grid MOUNTING HOLE FOR FIL VOLTAGE ADJUST The socket on the ex- cap GC1. I salvaged mine M1 S4 POTENTIOMETER M2 treme right in the back row from a junker radio. If you takes short -pin, bayonet - can't find one to can- mount tubes such as the nibalize, use an alligator UV- 201 -A. Just to the left of it clip for the time being. You is a similar socket in the can substitute the real thing "bantam" size; that one is after you succeed in for tubes such as the scrounging one!

UV-199. I never was able to Now let's talk about how find a special socket for the to operate this tester. type WD -11 (the one with S7 one fat pin and three skinny PRELIMINARY S3 ones rather than the usual ADJUSTMENTS S6 Iwo fat, two skinny config- Do not insert the tube to S9 uration). However, the be tested until you've made dummy socket at back row preliminary adjustments as NE2 NE1 left serves as a holder for follows. (To make these in- an adapter I happened to structions more meaningful, have that allows the WD -11 refer to the schematic di- Si to be tested in the UV-201 -A agrams in the December socket. and February issues as you Even the much- more -re- read.) cent, "standard" 4- and 5- First apply power to the prong sockets, as used in instrument by turning on S10 S8 DIM1 S2 the front row, can be a bit switch S1. Pilot lamp NE1 of a problem to obtain. should light. Check S2 to The back of front panel prior to beginning the wiring.

www.americanradiohistory.comAmericanRadioHistory.Com The plate- current reading 24A), be sure to attach grid TABLE 1- SPECIFICATIONS cap GC1. for the type 80 is taken in Watching meter M2, you'll Tube Fil S7 Not ST the same manner as for the Type Socket Volts Pressed (mA) Pressed (mA) see the filament voltage type 81. However, the type drop a bit under the load OOA SO1 Series 5.0 1.5 3.5 80 has two plates, so two 4.5 -5.0 of the tube then increase 01A SO1 Series 5.0 1.7 separate plate- current 10 SO1 Series 7.5 2.0 6.0 as the voltage -reg- readings must be taken. again 11 SO1 Series 1.1 1.0 -1.5 2.0 -2.5 The 2ND PLATE switch, S5, se- ulator circuit re- establishes 12 SO1 Series 1.1 1.0 -1.5 2.0 -2.5 the the correct value. Under no 12A SO1 Series 5.0 2.0 6.5 -7.0 lects one or the other of circumstances is the tube 20 SO1 Series 3.3 2.5 -3.0 5.5 -6.0 two plates. The reading for 2.0 4.0 -6.0 to be inserted before the 22 S03 3.3 each plate should be close 24 SO4 2.5 1.0 2.6 to the value given in Table 1 voltage is adjusted! The 24A SO4 2.5 1.0 2.6 under "S7 not pressed." voltage remains quite sta- 26 SO1 Series 1.5 1.5 4.0 ble after it's set, but small 27 SO2 2.5 1.5 -2.0 3.0 -5.5 movements of the voltage 40 SO1 Series 5.0 .7 1.7 ADVANTAGES AND 45 SO1 Series 2.5 3.0 11.0 control can cause large LIMITATIONS 50 SO1 Series 7.5 3.0 10.5 In concluding the series swings in voltage, and you 71A SO1 Series 5.0 3.5 -4.0 12.0 -13.0 can burn out a filament 80 S05 5.0 100 - on The Cunningham Spe- 100 before you know it. 81 SO1 Series 7.5 - cial, I'd like to stress what 99 SO1 Series 3.3 1.5 3.0 this instrument will and I burned out a tube in just that manner (and a type 12 won't do. It hasn't been at that!) while testing the designed to check hun- breadboard version of this the values you observe may Make the SHORTS test just as if dreds of different kinds of instrument. To say that I'm not be exactly like the val- you were checking an am- tubes. For that, your best still kicking myself is putting ues in the table, but you plifier tube, then move S10 bet would be to acquire a it mildly! should be somewhere in to the TEST position and read commercial tube tester. the same ballpark. To set M1. That is the only plate - And it won't give you a CHECKING AMPLIFIER more accurate standards, current reading you can definite "good" or "bad" TUBES you might like to test several obtain, since the tube has reading on the condition of testers (in- If the tube to be checked good tubes of each type, no grid and hence there a tube. But few have is an amplifier tube (any averaging the results and can be no grid -shift read- cluding those that do "good /bad" scales) provide type on Table 1 except the recording them for future ing. Compare it with the 80 or 81 -which are rec- reference. reading given in Table 1 definitive information about tifiers), proceed as follows. To check for the pres- under "S7 not pressed the condition of a tube. First, move function switch ence of gas in the tube, (mA)." The GAS and LEAKAGE What the unit will do is provide a reliable check on S10 to the SHORTS position press the GAS button (S4). tests have no meaning for and watch NE2. There should be no change standard rectifier tubes. about eighteen early tube If it lights (ignore any mo- in the plate current ob- The type 80 is tested in a types, comprising most of mentary flickering), the served on M1. If there is, gas similar manner to the type those available through 1932. The tube is probably shorted, is present to some degree. 81, with a couple of minor about earliest and you should avoid ad- If the tube has a cathode exceptions. First, the FILAMENT - types in that group usually vancing switch S10 to the (types 24, 24A, or 27), now VOLTAGE ADJUST control is not can't be handled by com- checkers, which TEST position. Otherwise a press the LEAKAGE button (S3). used with that tube since mercial large current surge could The M1 meter reading the filament draws too lack the required test data pass through meter M2, should immediately drop to much current for it to be and /or special sockets. possibly burning it out. zero; if it doesn't, there is a supplied from the adjusta- Though you don't get a If there is no short, move leakage path- possibly a ble voltage -regulator specific "good /bad" answer is the instrument, it will 510 to TEST and read the dead short-between circuit. The filament con- from tube's plate current on heater and cathode. nected to the DC power give you a very good in- meter Ml. You should ob- supply, ahead of the reg- dication of the general tain a value near that CHECKING RECTIFIER ulator circuit, through a condition of a tube -and is very useful in compar- shown in Table 1 under "S7 TUBES dropping resistor that re- also Not Pressed (mA)." Now If the tube being check- duces the supply voltage to ing a group of similar tubes the best ones. press the GRID -SHIFT button ed is a type 81 rectifier, the correct amount. The to identify (switch S7) and note the proceed with the prelimin- reading on meter M2 has Finally, I wouldn't recom- reading. It should have in- ary adjustments exactly as no meaning in this case. mend The Cunningham creased to a value near described earlier. However, The type 80 receives the Special as a project for an that shown in Table 1 under since rectifier tubes draw correct filament voltage inexperienced builder. "S7 Pressed (mA)." The dif- much more current than only if switch S2 is set to the If you feel that The Cun- ference in readings is an the amplifier tubes handled Lo position. When S2 is set to ningham Special has a indication of the amplifying by this instrument, set the HI, the type 80's filament is place on your workbench, ability of the tube. CURRENT -RANGE switch (S6) for automatically discon- go to it! And I hope you find Due to individual dif- ifs higher range after set- nected to prevent burnout this instrument as much fun ferences in construction, ting the LINE ADJUST control. due to overvoltage. to put together as I did!

71

www.americanradiohistory.comAmericanRadioHistory.Com COMPUTER BITS

By Jeff Holtzman his is a three -part story. What is hypertext? Where provision whereby any item

Part I occurred in the did it come from? What's it may be caused at will to 1940's. Part II occurred in good for? This time and select immediately and au- the 1960's. Part Ill is happen- next time we'll take a stab tomatically another." ing right now (unfolding at answering those ques- By today's standards, the right before our very eyes). tions. Memex has all the grace Hypertext: The basis of this story is a and subtlety of a Buck new technology variously PART I Rogers film. However, Bush's Hype or text? called hypertext, hyper- In 1945, Vannevar Bush associative indexing has media, and multimedia. (an electrical engineer seeded a revolution whose Cynics say that hypertext is credited with inventing the full significance no one can just another fad, soon to be first analog computer, and yet foresee. replaced by another. A who also happened to be For the next twenty years more sober assessment is President Roosevelt's sci- or so, development of dig- that Ws a solution in search ence adviser) published an ital computers and solid - of a problem. article in a popular maga- state devices proceeded zine, the Atlantic Monthly. briskly, while Bush's ideas lay The article was entitled "As fallow. We May Think."' The title indicates Bush's subject: PART II cognition, how we think. In In the early 1960's, com- Bush's words, "The human puter pioneer Ted Nelson mind...works by association. took the idea of associative With one item in its grasp, it indexing and generalized it snaps instantly to the next from an essentially individu- that is suggested by the al method of presentation association of thoughts, in to a cross -cultural network accordance with some in- of scientific and literary tricate web of trails carried works, interconnected, by the cells of the cross -referenced, and an- brain...the speed of action, notated by anyone who the intricacy of trails, the cared to comment. Nelson ToolBook is the premier hypertext- development environment for detail of mental pictures, is also included a filtering the PC. It contains powerful tools for creating attractive awe -inspiring beyond all mechanism to help screen drawings, simple databases, and provides a means of linking its else in nature." useless comments, and a screens together in a natural, intuitive manner. In the article, Bush la- method of respecting ments issues familiar then copyrights, so that original Visionaries think that hy- and all the more so now: authors would be paid roy- pertext is going to specialization of knowledge alties when their works were revolutionize everything and professional function, accessed. from computer operating and exponentially growing Nelson dubbed his systems to application pro- mounds of information in scheme hypertext, and de- grams to games and which the "truly significant fined it simply as "non- linear entertainment to educa- attainments become lost in reading and writing." tional software to electronic the mass of the inconse- Nelson's ideas have been mail and corporate com- quential." highly influential, but it took munications generally. Pick Bush's solution was a de- drastic advances in the any large computer com- vice he called the amount of computer power pany (IBM, Apple, Tandy, " Memex," a desk with a available to the average Fujitsu, HI? Microsoft), and it's huge library of microfilm person, along with the de- a sure bet that extensive sheets, and mechanisms to ployment of "user- friendly" research on hypertext is go- manipulate them, view devices and techniques ing on therein. them, navigate among (mice, bit -mapped graph- them, and annotate them. ics displays, non -batch All quotes from the article as The crucial idea is that of operating systems) before reprinted in CD ROM: The New "associative indexing, the hypertext was quite ready Papyrus, Microsoft Press, 1986. basic idea of which is a for prime time.

72

www.americanradiohistory.comAmericanRadioHistory.Com Another twenty years Academically, Hyper- have helped create a rat's 2490 Black Rock Turnpike, lapsed; for the most part, Card's success served as a nest of information will also Suite 337, Fairfield, CT hypertext remained in the catalyst for increased fund- help us untangle the mess. 06430; Tel. 203 -368- 0632). realm of esoteric academic ing and activity. Looking for a business For further reading, consult research. In the meantime, Commercially, it spurred opportunity or a new (or the October 1988 and Feb- the computer was getting a good old American com- first) career? Here's another ruary 1990 issues of Byte lot smarter -and a lot petitiveness ( "Anything you quote from Bush's article: magazine. For additional cheaper. And computer can do, I can do better"). "There [will be) a new pro- references, contact me c/o and cognitive scientists Since HyperCard's release, fession of trail blazers, those Popular Electronics (500 -B were learning much about several companies have re- who find delight in the task Bi- County Blvd. Farm- the charms necessary to leased similar programs of establishing useful trails ingdale, NY 11735). tame that savage beast. with greater capabilities; through the enormous mass A couple of years ago, a other companies have re- of the common record." cranky professor of mine PART 111 leased similar products for Want to play with hyper- stated categorically that hy- In 1987, Apple Computer the PC environment. Mac text? One of the older pertext was more hype released a program for the hobbyists got into the act magazines dedicated to than text. That statement Macintosh called Hyper- by building their own Hy- personal- computer pro- may have been true then, Card. With a single stroke, perCard programs and gramming, Doctor Dobbs, but today there are more Apple unintentionally un- sharing them on electronic - dedicated its June, 1990 is- and more instances of truly leashed one of the most bulletin -board systems (BBS). sue to hypertext, and also wonderful hypertext prod- powerful forces in nature: Commercial developers published an electronic (hy- ucts. Hypertext is definitely human creativity. And, in an have built and are now pertext) version of that issue. here to stay! extremely unusual market- selling HyperCard stacks on I'll post it on the Gernsback Next time, I'll talk about ing move for Apple, the diverse subjects. BBS (516- 293 -2283, some commercial products company simply gave the 300/1200, 8N1); look for file that use hypertext, and program away with every SO WHAT? DDJ6- 902IP Even the ZIP file about "ToolBook," a hyper- Mac sold thereafter. Hypertext is catchy. If you contains more than 800K, text development environ- What is HyperCard? Bill don't believe that, find a so you may want to order a ment for the PC that pro- Atkinson, one of its creators, friend with a Mac (or go to disk directly from the com- vides a superset of the often describes HyperCard a local computer store) pany that built the functions provided by Hy- as a "software erector set." and get a demo of Hyper- hypertext version (Ntergaid, perCard. By way of analogy, imagine Card. If you've got Windows that cars were built out of 3.0, install the demo pro- standard components with gram DayBook and spend M I G t W standard interfaces. Using some time thinking about standard components, you not so much what it does, Pocket Reference could build your own car by but how it does it. choosing an engine here, a Hypertext is catchy. Why? 480 pages of tables, maps, transmission there, a body Because it works the way formulas, and conversions somewhere else, and inte- the mind works associa- and it fits in your shirt pocket rior styling in yet another tively. Because it uses all ( 3.2" x 5.4" x 0.6")! place. Bolt the whole thing media: text, sound, still together, and you'll have a graphics, motion video. Be- racial serviceable vehicle that ac- cause it gets you involved. = of complishes the goal of any Because it is fun. $9.95* automobile (getting you Our age is often charac- where you want to go), terized as the age of so in information. After a * Plus $2.00 shipping & handling. does a highly individu- couple Colorado residents add 566 tax. alized style, and does so more stages in its evolution, without great design effort Hypertext is going to be the Small sample of contents tool that brings the expo- Air Tool CFM vs PSI Radio Alphabet or expense. Battery Charging TEN Radio Codes That's what HyperCard nentially exploding mass of Tire Manufacturer Codes Telephone Area Codes Lumber Sizes & Grades Lost Credit Card Phones did for the computer en- information under control. Concrete & Mortar Sound Intensities Element Tables Wind Chill Factors vironment. And it just so Its almost paradoxical that Computer ASCII Codes Frequency Spectrum IBM? PC Error Codes Geology Mineral Tables happened that in doing so, the very machines that IBM!, interrupts-10 Map Glues and Solvents 80286 Hard Disk Types Bolt Torque Tables HyperCard embodied sev- Printer Control Codes Wood Screw /Nail Sizes Electric Wire Size vs Load Math Formulas & Tables eral (but by no means all) NEMA Motor Frames Plane /Solid Geometry Wire & Sheet Guages Copper /Steel/PVC Pipe of the most important ideas VENDOR INFORMATION Resistor /Capacitor Colors Rope Cable and Chain Pilot Lamp Specs Tap -Die -Drill Sizes associated with hypertext. Fuse & Battery Specs Sand Paper & Abrasives Electrode & Solder 1.0 RF Coll Winding Data Weld That, in turn, led to a ToolBook ($395) Wire Size vs Turns/Inch 3200 Conversion Factors Asymetrix Corp. groundswell of interest in Money Back Guarantee - If not completely satisfied, return 110 110th Avenue book postage prepaid, in mint condition for a 100% refund! hypertext academically, Bellevue, WA 98004 commercially, and even at Tel. 206- 637 -1600. Sequoia Publishing Inc. the hobbyist level. Dept 920, P.O. Box 620820 Littleton, CO 80162 73 CIRCLE 15 ON FREE INFORMATION CARD

www.americanradiohistory.comAmericanRadioHistory.Com CIRCUIT CIRCUS

By Charles D. Rakes This time around, the Cir- quency, pulse -generator charging capacitors, cus deals with a circuit. The circuit has a C1 -C4 (as selected via S1, number of unrelated cir- frequency range of 2 Hz to the range switch) and the cuits that can be used as over 50 kHz, and produces values of resistors R1 and R2. simple test instruments or narrow, 7 -volt, positive -go- The circuit's switching time is be incorporated into a fu- ing pulses. The pulses fairly rapid due to the re- Test ture project. In any case, produced by the circuit generative action of the get ready for some building have widths of about 7 mi- emitter -coupled transistors, Instruments fun. The first circuit that we'll croseconds at the circuit's Q1 and Q2. That quick explore is a variable -fre- maximum frequency and switching action produces and More! quency pulse generator. 10 milliseconds at its lowest a fast rising output pulse. frequency. With S1 in position 1, the PULSE GENERATOR The circuit's operating fre- circuit oscillates in the Figure 1 is a schematic quency is determined by range of 2 to 50 Hz; in diagram of a variable -fre- the value of one of the position 2, the range is 15 to 500 Hz; in position 3,120 Hz to 5 kHz; and in position 4, 1.5 to 55 kHz. Potentiometer R8, a 5k or 10k unit (which can be omitted from the circuit if not needed) is included in the circuit to provide an adjustable pulsewidth. The pulse will increase in width as the resistance of R8 is increased. The generator circuit isn't complicated, nor is there anything critical about the circuit, so it can be as- on Fig. 1. The variable frequency pulse generator produces narrow 7 -volt positive -going pulses and sembled perfboard and has a frequency range of 2 Hz to over 50 kHz. housed in a small plastic cabinet. The circuit can be powered from a 9 -volt tran- sistor battery. Such a circuit PARTS LIST FOR THE can be a valuable aid in PULSE GENERATOR servicing or experimenting on an existing or future proj- RESISTORS ect. (All fixed resistors are 1/4-watt, 5 % hint'. ) Rl, R7-I0,000-ohm R2- 500,000 -ohm potentiometer PROXIMITY DETECTOR R3R5-470-ohm Our next circuit, a prox- R6 -1000 -ohm imity detector (see Fig. 2), is R8 -5000 -ohm or 10.000-ohm potentiometer (see text) designed for those who en- CAPACITORS joy modifying an existing CI- 0.001 -µF ceramic -disc circuit to produce a prac- C2 0.01 -p F, ceramic -disc tical and working project. C3- 0.1 -p.F, ceramic -disc The detector consists of a 100 -WVDC, electrolytic 567 tone decoder (U1), a C5, C6 0.27 -p,F, ceramic disc couple of transistors, and a ADDITIONAL PARTS AND MATERIALS few support components. QI, Q2- 2N3906 general- purpose PNP silicon transistor The circuit's operation is Q3- 2N3904 general- purpose NPN silicon transistor simple. The 567 is config- Perfboard materials, enclosure, 9 -volt transistor-radio battery and ured as a decoder; R2 and battery connector, wire, solder, hardware, etc. C4 set its receive frequency to about 100 kHz.

74

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www.americanradiohistory.comAmericanRadioHistory.Com +9v 3. The detector can help in C3)I R1 locating those damp spots .1 1K in your in time to 1' )1 PICK -UP carpet C4 R2 R4 C8 SENSORS properly clean and dry 680pF 10K 10K LEDI 39pF SEE TEXT R5 them before they do per- R7 4.7 K iMEG manent damage. R6 The moisture is 220K detector 1M little more than a single U1 567 06 C7 2N3904 NPN transistor (in a 02 680pF 680pF 2N3904 common -emitter config- 1 2 Cl C2 I_ l uration) that's used to turn .1T 1 on a piezo sounder, BZ1. The 2N3904 R3 one probe is connected to 10K C5 the base of Q1 through a 1k 680pF resistor (R2) and the other R8 w` 1 is 1K probe tied to the +V terminal of a 9 -volt tran- Fig. 2. The proximity detector consists of a 567 tone decoder, a couple of transistors, and a few sistor radio battery through support components. current -limiting resistor R1 (another 1k unit). A desensi- so to avoid problems keep tizing resistor, R3, is PARTS LIST FOR THE all component leads as connected to the circuit via PROXIMITY DETECTOR short as possible, and avoid switch S1. criss- crossing wires. The de- Since there's zero current SEMICONDUCTORS tector circuit can be used drain when the circuit isn't UI -567 tone decoder, integrated circuit to detect metal objects, in use, an on /off switch isn't Ql, Q2- 2N3904 general -purpose, NPN silicon transistor such as nails and electrical needed and the 9 -volt tran- LEDI -LED (any color) wiring in walls, objects trav- sistor battery should last its RESISTORS eling on an assembly line, shelf life. The detector's (All fixed resistors are' -watt, 5% units.) and any object capable of maximum sensitivity is R I- 1000 -ohm coupling a signal from one about 2.5 megohms with S1 R2R4- 10,000 -ohm pick -up to the other. For in its normal position and R5-4700 -ohm instance, the sensors can about 100k when S1 is acti- R6- 220,000 -ohm be attached to non -metal vated. Those Iwo ranges will 1- megohm R7- tubing to monitor the flow help in mapping wet spots. R8- 1000 -ohm potentiometer of conductive fluids. There is nothing critical CAPACITORS The sensors can be about the circuit; it can be ClC3 0.1 -RF, ceramic -disc made from almost any built on a small piece of C4 C7- 680 -pE, ceramic -disc metal such as aluminum, perfboard, with point -to- 39 -pF, ceramic -disc C8- aluminum foil, brass, cop- point wiring used to inter- ADDITIONAL PARTS AND MATERIALS per, etc., and can be as connect the components. Perfboard materials, enclosure, pick -up material (see text), IC small as two short pieces of Two heavy -duty sewing -ma- socket, 9 -volt transistor-radio battery and connector, wire, hook -up wire or as large as chine needles can be used solder, hardware, etc. needed. To achieve the as probes. The circuit can best performance, bread- then be housed in a length board the circuit and of 1 -inch plastic pipe to An LED, connected to U1's a matching transformer, of- experiment with various size give it a manufactured pin 8 output, lights when an fering the sensor a high - of sensors, the spacing be- look. If the circuit is to be in -band signal is detected. input impedance and a tween each sensor, the housed in a plastic pipe, The pin 5 output of U1 (a low- output impedance, operating frequency, and the needles should be long 100 -kHz square -wave signal) which matches the input different values for C8 and enough to extend at least is fed through C8 to R4 and impedance of Q1, whose R4. 11- inches past the end of one of the pick -up sensors. gain is set by potentiometer the pipe. That RC combination R8. The amplified output of MOISTURE DETECTOR Switch S1 can be causes the square -wave Q1 is fed to U1 at pin 3. Our next entry is a simple mounted to the pipe output to differentiate, shift- When the input signal is circuit that can be used as above the circuit. It's a ing the phase of the signal about 100 -millivolts or a "puppy puddle" detector. good idea to insulate the at the pick -up sensor, and greater, U1 detects the sig- Now don't laugh; I know of battery to prevent its metal allowing U1 to detect its nal and lights LEDI. a carpet cleaning compa- case from shorting out the own output signal. The detector circuit is ny that paid over $80 each circuit components. That's The other pick-up sensor slightly more critical in the for a number of commer- easily done by stuffing a is connected to the input of construction scheme used cial moisture detectors that piece of foam rubber, or an emitter- follower ampli- than most of the circuits didn't perform any better similar non -conductive ma- fier, Q2, which operates like presented in Circuit Circus, than the one shown in Fig. terial, into the pipe to

www.americanradiohistory.comAmericanRadioHistory.Com R1 other units can be used for 100 ! SEE TEXT setting the transistor's base bias. There are several precau- tions you should be aware

B1 of and follow in using that +9v I simple testing procedure. QI the 2N3504 i Keep the leads from separated 16 -INCH TEST LEADS WITH CLIPS as much as possible to re- duce coupling and Fig. 4. The variable oscillations, and don't allow resistance box can be levels through the assembled from junkbox current components, and will be of potentiometers to exceed their ratings. In addition, Fig. 3. The moisture detector is nothing more than a transistor greater service than its (in a common -emitter configuration) that is used as a simple simple appearance suggests. avoid destroying the tran- switch.

PARTS LIST FOR THE PARTS LIST FOR THE VARIABLE RESISTANCE BOX MOISTURE DETECTOR RESISTORS Ql- 2N3904 general -purpose NPN silicon transistor R1-100-ohm linear potentiometer RI, R2 -1000 -ohm, /4 -watt, 5% resistor R2 -1000 -ohm linear potentiometer R3- 10,000 -ohm, 1/4-watt, 5% resistor R3-I0,000-ohm linear potentiometer BI -9 -volt transistor-radio battery R4- 100,000 -ohm linear potentiometer SI- Normally -open push -button switch R5- l- megohm linear potentiometer BZl -Piezo buzzer Cabinet, leads, alligator clips, etc. Perfboard materials, Perfboard materials, enclosure, probe, battery connector, wire. enclosure, AC molded power plug with line cord, battery(s), solder, hardware, etc. battery holder and connector, wire, solder, hardware, etc.

maintain separation be- box (see Fig. 4) -certainly tween the battery, switch, falls into that category. Note 2A T1 PLI and perfboard- mounted that to conserve space only 1.75A 0 . 001 SEE TEXT components. The piezo one potentiometer is sounder can be attached shown, but keep in mind 1 to the end of the pipe that the substitution box can opposite the probes. have as many potentiome- is a very useful to have To check the circuit's op- ters as desired; say, five with Fig. 5. A variable AC power supply tool on your workbench when you're servicing malfunctioning eration, bridge a 2.2- values of 100 ohms, 1k, 10k, electronic equipment, or you are preparing to put back into megohm resistor across the 100k, and 1 megohm. service equipment that has been idle for a long time. probes; doing so should Mount the potentiome- cause BZ1 to sound. With ters in a plastic cabinet with the 2.2- megohm resistor still a scaled escutcheon for PARTS LIST FOR THE in place, press S1 and the each. Bring out three dif- VARIABLE AC SUPPLY sound should cease. Re- ferent color test leads with move the 2.2- megohm alligator clips for each po- T1 -1.75 -amp variable transformer resistor and replace it with tentiometer. That gives you Fl -2 -amp fuse a 100k resistor and BZ1 a variable substitution box SOI-AC socket should sound at full volume. that can take the place of PLI-AC plug Now press S1 and the vol- an expensive resistance de- SI -SPST switch ume should drop to a cade box. Of course the Cabinet, wire, solder, hardware, etc. much lower level. If so your potentiometer's adjustment probe is ready for action. won't be as accurate as a decade box, but it will allow needed value. I've found sistor by making sure that VARIABLE RESISTANCE you to make a smooth resis- the variable resistance box the potentiometer is at its BOX tance change that's not of this type to be useful in maximum resistance setting Often it seems like the possible with a decade setting up and checking when power is applied to simplest form of tester turns box. single -transistor amplifiers; the unit under test. out to be one of the most If your experiments re- one potentiometer can be valuable and frequently quire accurate resistances, connected to the collector VARIABLE AC SUPPLY used gadgets on the work- a digital ohmmeter can be as a load resistor, another Our last entry is another bench. Our next circuit -a used to set the selected as the emitter resistor, and simple circuit-a variable u-r3 variable resistor- substitution potentiometer to the either one or Iwo of the (Continued on page 86) co 77

www.americanradiohistory.comAmericanRadioHistory.Com HAM RADIO

By Joseph J. Carr, K4IPV What do you hear This project is a passive of Vg is 0.2to0.3 volt in when you tune be- noise limiter that is inserted germanium (Ge) diodes, tween strong stations on the between the audio output and 0.6 to 0.7 volt in silicon receiver? Hiss! Garbage! of the receiver and the ear- (Si) units. Noise! One of the uncom- phones or loudspeaker When Iwo diodes are fortable aspects of (although it works best with connected back-to -back An audio - operating on the ham headphones). The project (see Fig. 1B), there is a bands is the large amount serves Iwo purposes: one is "dead- band" between noise blanker of pure trash that assaults to reduce the noise be- -V and +V with one's ears. Anything that tween stations, and the "ohmic" behavior at poten- can reduce the level of the second is to clip large sig- tials greater than those trash enhances your oper- nals and thereby add a values. That is, when Iwo ating pleasure, and little distortion to the CW germanium diodes are reduces the stress on your note. connected back -to-back, ears and head. That's right, distortion, and no current flows when the There are a number of no, I'm not crazy (at least signal voltage applied to things that can be done to not on this subject), for the diode pair is between make the received signal a some operators report that - 0.2 volt and + 0.2 volt. a mildly distorted CW beat There are two basic forms note is more comfortable of passive noise limiters: the to copy. The effect is es- series type, which is shown DI pecially noted when a in Fig. 2A and the shunt stronger, desired station version shown in Fig. 2B. In centered in the receiver the series (or "threshold ") passband is distorted, and form of noise limiter, the Vg slightly weaker interfering signals must exceed the stations are not. Other op- threshold set by Vg before it REVERSE FORWARD BIAS REGION BIAS REGION erators disagree with that is passed along the signal theory, so the project below line. In the shunt noise lim- makes the distortion feature iter, on the other hand, optional. large signals are clipped off above Vg. Most passive BASIS FOR OPERATION noise limiters use some form D2 The passive noise limiter is of series current -limiting re- -VG based on the operation of sistor to protect the driving -V- + V +vg the simple PN junction di- circuit from a short circuit ode. Figure 1A shows the when the shunt diodes con- characteristic curve of such duct. a diode. When the diode is operated in the reverse - THE PROJECT CIRCUIT bias region, no current flows Figure 3 shows the sche- Fig. I. Shown in A is the (except a very tiny, reverse matic diagram for a current (1) vs voltage (V) But the noise curve for a PN diode; B is leakage current). passive -limiter circuit the curve for a pair of back - current doesn't start flowing that contains both a series to -back diodes. immediately when the re- threshold noise limiter and verse -bias negative voltage a shunt noise limiter. The lot clearer. One could fitter passes through zero to be- circuit is composed of two the signal, or use a high - come positive. Until a germanium diodes (D1 and priced noise blanker (which certain critical junction po- D2) and two germanium doesn't always work). The tential Ng) is reached, the PNP transistors connected in project that we'll present diode does not pass cur- the "super- diode" config- this month is a simple little rent. At voltages above Vg, uration (i.e., bipolar device that can be built in the diode operates in the transistors, either NPN or PNP one evening with ease, and "ohmic region" much like with their respective collec- can make a lot of dif- any other conductor; that is, tor and base terminals ference, especially for CW current increases with in- shorted together). Such a operators. creasing voltage. The value noise limiter can enhance

78

www.americanradiohistory.comAmericanRadioHistory.Com AUDIO diodes in a blister pack at a Select a resistor that will band. Next, open S1. The INPUT very low cost per diode. match your receiver's speci- weaker signals -i.e., those Switch S2 must be closed to fication. Alternatively, pick a that do not reach the 0.2- turn on the shunt noise- 5 -watt resistor for R1 and be to 0.3 -volt threshold -and limiter circuit (D1 and D2). done with it. the background hiss should Note that there's a dif- The noise limiter can be either go away or be re- ference in the operation of built into a small metal or duced a respectable switches S1 and S2; switch plastic box. The input and amount. S1 is open when you want output jacks should be se- Try the noise limiter in and AUDIO the series noise limiter in the lected to match the out of the signal path on a INPUT circuit, while S2 is closed earphones and receiver number of different signal when the shunt noise limiter that you own. In my own combinations in order to is to be in the circuit. The case, the receiver's ear- become familiar with the shunt noise limiter requires phone jack is a 1/4 -inch way the circuit works. You a series current -limiting re- phone jack. The noise lim- will find that you'll want to sistor in order to protect the iter can then be connected take the series noise limiter audio output stage of the to the receiver by a short out of the circuit when

B receiver. jumper cable with mating copying weak signals. When the diodes are for- male plugs on either end. Next, let's try the shunt Fig. 2. There are two basic In my case, a one -foot noise limiter. Close switch S1 forms of passive noise ward biased, a large and then close S2. You'll limiters: the series type (A) current can flow, which can shielded cable with a male and the shunt type (B). be detrimental to both the PL -55 on each end did the find that on strong signals receiver audio -amplifier trick. (play with the audio -gain stage and the diodes control of the receiver), the the signal -to -noise ratio at themselves. A resistor of USING THE NOISE CW beat note distorts the earphones as much as about 3.3 to 8 ohms (nomi- LIMITER somewhat; just how much 40 dB (according to theo- nally 5 ohms) can be used Plug the earphones into depends on the signal ry), but 20 to 30 dB is more as a current limiter. The J2, and connect a jumper level. If you find the signal likely (still not a shabby bit power rating of the resistor cable between J1 and the when the circuit is in the of performance improve- must be sufficient to handle receiver's earphone jack. latter mode easier and ment). the entire audio output of Close S1 (the our position in more comfortable, then The series noise limiter is the receiver. Most ham -ra- Fig. 3) and open S1 (also you've improved matters. formed by "super- diodes" dio receivers produce from the our position). Turn on the Otherwise, turn off the shunt constructed from a pair of about 250 milliwatts (mW) receiver and tune across limiter and don't use it un- medium gain germanium to 5 watts of audio power. the CW portion of a busy less some spark plug or PNP transistors. The tran- motor noise is received. In sistors to use include the some cases, the shunt noise 2N404, 2N1305, and so limiter will clip off the high - forth, if you can find them. voltage noise spikes from Modern equivalents from Rr sparking electrical sources 5n radio -TV repair replace- J1 J2 (such as passing cars) when ment lines include the AUDIO TO copying weak signals. So it INPUT EARPHONES ECG -100, ECG -102, NTE -100, is possible to use the shunt and NTE -102. The idea is to noise limiter when the series get a medium beta -gain noise limiter is out of the PNP germanium (not silicon) circuit. transistor. A switch in paral- Additional information on lel with the back -to -back noise limiters, and the more super- diodes bypasses the complex noise -blanker cir- threshold noise limiter when Fig. 3. This passive noise -limiter circuit contains both series cuits, can be found in it's not wanted in the circuit. ( "threshold ") and shunt noise- limiter configurations. various editions of The ARRL In other words, with S1 Radio Amateur's Handbook. closed, Q1 and Q2 are My new book on ham radio switched out of the circuit. PARTS LIST FOR THE antennas, Practical Anten- The shunt noise -limiter NOISE LIMITER na Handbook (TAB catalog portion of the circuit con- number 3270) includes a sists of a pair standard QI, Q2- 2N404, 2N1305, ECG -100, ECG -102, NTE -100, large number of antenna germanium diodes, D1 and NTE -102, or similar germanium PNP transistor construction projects and D2, such as the 1N34, 1N60, DI, D2 -1N34, 1N60, ECG -(09, NTE -109, or similar hints, as well as some BASIC germanium diode ECG -109, and NTE -109. Such programs for antenna de- R1 -5 -ohm, Y4 -watt resistor units are available from sign. The book is available SI, S2 SPST toggle switch mail -order suppliers, as well from TAB Books, Inc., Blue .11,12-See text Ridge PA as from Radio Shack in bulk Perfboard materials, enclosure, wire, solder, hardware, etc. Summit, form; i.e., a bunch of odd 17294-0850; 1-800-233-1128.

www.americanradiohistory.comAmericanRadioHistory.Com DX LISTENING

ne of the most gratify- quote, in part: "Well, Nor- national on the same By Don Jensen ing things about doing way is a small country, frequency as WWCR in this column is hearing from inhabited by people who Nashville, TN ?" you. Regular readers know were already fed up with Yes, Leo, and it's because

that each month I include a war, political ambition, and the onetime shipboard pi- Reader Mail letters section, called Mickey Spillane novels rate station that stirred up "Feedback," which is de- when the Vikings closed such a fuss a few years ago voted to your comments shop back in 1200 AD. So has gone legit. RNI has and questions about short- what can we teach the been airing its program- wave listening. Since the world? Not much, to be ming over WWCR facilities mailbox has been really quite honest. Teach Ameri- for three hours weekly. It's stuffed lately, let's start right cans how to do business? actually the Nashville trans- out this month with your The Germans how to keep mitter you're hearing.

feedback, so that I can get the trains on time? The Swiss At this writing, Radio New- to as many of your letters as how to make watches? The york International programs space allows. Swedes how to make cars? are heard on Monday The Japanese to be effi- mornings, Universal Coordi- cient?" nated Time (meaning

"No we couldn't and I Sunday night in the U.S. and suspect our listeners Canada), from 0100 to wouldn't want us to. What 0400 on 7,520 kHz. we will try to do is to keep A question about an un- you informed on what's identified standard -time/ happening this far north." frequency station comes

I guess that means that from Mary Alice Barstow, Al- the broadcasting world's lit- buquerque, NM. "I tuned in tler guys ought to do what to time station WWV on they do best, within the lim- 5,000 kHz the other night its of their resources and and heard what seemed to broadcasting facilities. And be another time signal un-

that's what RNI is derneath. I know that doing...once a week. WWVH in Hawaii uses the

Next we hear from Leo same frequency, since I can Evans, who writes from hear that one in the early Andy Farley may be only 2, but hel already seems attracted to radio listening. Andy's dad, Joe, is also an avid DX'er with Vieux Fort on the island of mornings, mixing with, and nearly 190 countries logged. He is an electrical engineer and St. Lucia in the West Indies. sometimes stronger than president of the Chicago Area DX Club. "I've been a shortwave lis- WWV.,, tener for the past 10 years," "But this station's time an-

LETTERS says Leo, "and I appreciate nouncements seemed to "A few months ago," the great column in Popu- be in Spanish, not English. writes Jeff Johnson from lar Electronics." Leo, who Who is it ?" Mary Alice qu- Reno, NV "you mentioned now uses a Sony ICF- 7600D, eries. that Radio Norway Interna- which he calls his "ultimate There are quite a few tional has English receiver," ranks DX listening time stations around the programming only on Sun- and body surfing as his fa- world, which operate on days. I'm of Scandinavian vorite activities. the standard frequency of heritage and would like to He says he's "picked up 5,000 kHz. Several stations - see Norway better repre- stations from across the in Argentina, Japan, and sented on shortwave. Do globe," but for regular you know why RNI has such SWL'ing, he likes Trans World 'Credits: W. Karcheski, MA; Joe an abbreviated English Radio in the nearby Howell, CA; Adrienne Barhydt, schedule ?" Netherlands Antilles, par- OR; Sheryl Paszkiewicz, WI; Sverre Fredheim, the sta- ticularly the "Bonaire Fred Kohlbrenner, PA; Dale tion's foreign broadcasting Wavelengths" program hos- Park, HI; Ronald Purdue, MN; Tim Noonan, WI; North Ameri- chief, that ques- ted by Rosewell. "I answered Chuck can SW Association, 45 tion on the air awhile back. wonder," Leo asks, "if you've Wildflower Road, Levittown, PA

I liked his answer, so let me heard Radio Newyork Inter- 19057

80

www.americanradiohistory.comAmericanRadioHistory.Com South Africa, for example - free mail -order catalogue ARGENTINA- 15,000 kHz. FRANCE -17,620 kHz. can be heard in North of the BBC (British Broad- Standard time and frequen- Radio France Internationals America, under optimum casting Corporation) World cy station LOL occasionally English "Letterbox" program conditions, despite WWV or Service Shop (Bush House, can be heard here, WWV's airs here at around 1630 WWVH "interference." Strand, London WC2 4PH, usual spot on the dial. UTC, with programming But it is likely that you England). Lots of good gift Spanish announcements switching to French before heard YVTO, operated by ideas there, including BBC - and Morse -code CW ID's 1700 UTC. Venuzuela's Cagical Naval logo coffee mugs, short- are broadcast every five HUNGARY -9,800 kHz. Observatory. The Spanish wave- related books, audio minutes. The rest of the News and commentary in identification that you and video cassettes of fa- time, of course, there are English from Radio heard probably was, "Ob- vorite BBC programs, time ticks and tones. Budapest is noted at 0030 servatorio Naval Cagical, language lesson tapes, BOLIVIA -6,155 kHz. This UTC. Caracas, Venezuela," an- great posters, and much, landlocked Latin nation is IRAQ- 11,830 kHz. Radio nounced each minute, much more. not the easiest to hear. One Bagdads English transmis- amid the second pulses. of the best chances to hear sions are noted on this MOST POPULAR? Bolivia, though, is Radio frequency at around 0230 AFRICAN POPS "Just curious," writes Bob Fides, owned by the Roman UTC and also at 2000 UTC kHz. "Ever since I read your Lesniak, Des Moines, IA "but Catholic Church in La Paz, on 13,660 article in the new SWL which shortwave station is which broadcasts in Span- LIBYA -15,415 kHz. Arabic book, Passport To World the most popular? "Now ish on this frequency at programming has been re- Band Radio about the pro- that depends on just exactly around 0130 UTC. ported from Libya's Radio gramming on Afrique what you mean, Bob. The FINLAND-9,670 kHz. Jamahiriya on this channel Numero Un and the Voice British Broadcasting Corp. Radio Finland, like Norway's about 2250 UTC. ofAmericds program, Mu- claims to have the largest shortwave broadcaster NEPAL --5,005 kHz. Radio sic Time in Africa, I've been audience in the shortwave mentioned earlier, has a Nepal is heard on the west a regular listener. That mu- world, some 120 -million lis- Scandinavian focus to its coast of North America at sic is baaaaaaaad, if you teners. Of that number, an news broadcasts. Look for around 1330 UTC with pro- get my meaning!" says Da- estimated 25 million are En- the English language gramming in Nepali, mien Taylor of Raleigh, NC. glish- speaking. "Northern Report" at 0430 including a children's cho- "Any more tips on great If you mean which inter- UTC. This one also operates rus singing. A parallel West African sounds ?" national station's programs on 11,755 kHz. frequency is 7,165 kHz. Alex Batman, SW pro- are most popular with SW- gramming expert for the hobby listeners like you and North American Shortwave me, I'm not sure. But, I'd like Association, one of the best to hear from the rest of you Phonvu Videophone in a Chip STILL FRAME TV PICTURE TELEPHONE shortwave listener clubs out there. The question is: around, suggests the daily Which is your favorite inter- SendsTRANCEIVER Slow Scan TV pictures KIT over "Morning Strike" program national SW broadcaster The phone line In Twelve Seconds on the Voice of Nigeria, and why? Captures any TV Camera, Camcorder 7,2555 kHz, at 0500 UTC. Your responses, in 100 VCR. NI TSC Video output and holds "Some of the best in African words or less, please, will the display and sends on command popular music, including in- appear in a future column. Auto Mode allows hands free send formation about the groups A copy of the 1991 Passport and receive. misplays on any TV and the performers, and a To World Band Radio, which IC Chip Replaces 150 SSI Dips York lot of good songs," Batman the New Times has _, 50 Levels om. ,---- ..... - -;: , writes. called the "TV guide for =V :177 1',7,: of Grey Scale , ,..4,, ,.. IWU9T "I don't know much about world -band radio," will go Serveses as: Phony° I 079 shortwave radio except my to the best entry. TV FAX AMEBA PHONE\ Po.Ew boyfriend is a nut about it," 200 X 242.5 tlk Camera- RECEIVE writes a young lady from DOWN THE DIAL High Res. 0 0 - fREE2E 9iOE . Florida who, for reasons that Your listening reports are BEFORE S.M. 50,000 1 r will become obvious, will also wanted. What are you Pixels 9.0 .19.9.0.1.71919 9900 Phonvu - - - remain nameless. "His birth- hearing on the shortwave - Videophone Chip 48P DIP day is coming up in a broadcast bands? Address and Schematic $59.95 couple of months and I your letters to Don Jensen, Tel]Tel. MonaMon -- A /D, DRAM, & CHIP SET S 35.00 want to get him something DX Listening, Popular Elec- Line PC Board (BARE) $18.95 unusual and short- tronics, 500 -B Bi- County both DISCRETE COMONENTS $28.75 Blvd., NY Modulator wave related. Any ideas ?" Farmingdale, Cabinet (MOLDED) $12.75 "PS. I want it to be a 11735. A reminder: Coordi- Use 1 Power Pack S 8.75 nated Universal Time (UTC) KIT PRICE: $ 164.15 secret so don't use my VCR TV . name. He reads your col- is equivalent to EDT +4 Mod ASSEMBLED .5.d" $ 235.00 month." hours, CDT +5 hours, umn every vlsA/M PHONE & FAX Order (213) 827 -1852 Dear Madame X: My sug- MDT +6 hours, or PDT +7 Electronics Box 11148 gestion is to write for the hours. P M C Marina Del Rey, CA 90292 CIRCLE 17 ON FREE INFORMATION CARD 81

www.americanradiohistory.comAmericanRadioHistory.Com SCANNER SCENE

By Marc Saxon hose who dance in the an optional 31/2- or 51/4 -inch ming at busy broadcast streets on the rare oc- computer disk. The scan- stations. casions that a new high - ning rate is at nearly 100 For years, scanner tech scanner is introduced channels per second. Sen- monitors have enjoyed tun- should get out their top hats sitivity is less than 1 µV at 12 ing in the communications and tails, and dust off those dB SINAD. Some of the other on these frequencies in High -Tech dancing shoes! The Uniden features include oversized, order to hear the drama MR -8100 Turbo Scanner has illuminated controls and an behind the headlines, as Turbo quietly arrived. It isn't being alphanumeric LCD readout well as the bits and pieces sold under their Bearcat or that shows programming that never made it on to Scanner Regency labels, but that prompts. the 11 o'clock news. isn't to say you won't be The MR -8100 may be field The problem has been interested in this unit. programmed, or can be that scanner hobbyists Uniden advises us that programmed (via RS -232 haven't been the only ones the MR -8100 Turbo Scanner input) from a PC. Each pro- tuned in. Some radio and grammed channel is identi- 1V stations monitor the fied with the name of the channels used by compet- service. There are many ing local broadcasters in more features and the only order to keep posted on usual scanner function their rivals' activities. It isn't that's absent is a search/ unknown for one station's scan mode. If you can be reporters or camera crew happy without that feature, to show up somewhere the MR -8100 appears to based solely upon informa- have a lot of potential. tion monitored over the Not every Uniden scan- channel used by another ner dealer seems to carry station's assignment desk. the MR -8100, but we have And getting traffic reports seen the unit being offered from another station's traffic by several dealers. One helicopter is a lot less costly price we noted was in the than sending up your own. $500 ballpark. You can ob- You get the picture. Those who like all the bells and whistles on their scanners should tain more information on Some broadcasters, feel- check out the high -tech Uniden MR -8100 Turbo Scanner. the Uniden MR -8100 by ing scooped on their own contacting the Uniden stories, eventually began was "developed exclusively America Corporation, 4700 using analog voice for public safety organiza- Amon Carter Blvd., Fort scramblers. That generally tions," and describes the set Worth, TX 76155. involves some form of au- as being "a high perfor- dio- frequency inversion, mance scanning radio WHO STOLE THE SCOOP masking, or band -splitting, receiver built to endure ex- Radio and 1V broad- and offers only limited pri- treme environments casters make heavy use of vacy inasmuch as it can be encountered in mobile and certain Iwo-way bands des- descrambled with simple emergency environments." ignated for use by so- called devices. Broadcasters still Its frequency coverage is 29 Remote Pickup Broadcast complained to the FCC to 54 MHz, 118 to 174 MHz, stations. Those stations are that other local stations 406 to 512 MHz, and 806 to frequently used by traffic were sealing their traffic re- 956 MHz. There are 100 helicopters, and by the me- ports and fast -breaking memory channels, with es- dia for dispatching news news scoops. tablished banks of ten crews to fast -breaking Now the FCC is going to channels each. The cellular events and for other func- allow those stations to install bands are locked out, but tions required to keep digital scramblers. Under may be restored by using newsroom operations hum- existing technology, it's vir-

www.americanradiohistory.comAmericanRadioHistory.Com tually impossible for such Americas Super Amplifier. transmissions to be under- Dave is at Elgin AFB, so AMAZING stood by unauthorized we'd suggest starting out SCIENTIFIC & ELECTRONIC parties. Of course, such with trying to pick up signals PRODUCTS equipment is very expen- on busy Elgin frequencies in LASERS AND SCIENTIFIC DEVICES sive, so it will probably find this band, such as 342.5, VRL2K 3mw Vis Red System Kit $159.50 use only at the largest and 372 2, 273.5, 348.4, 355.8, LLIS1K Laser Beam "Bounce" Listener Kit $199.50 LHC2K Visible Simulated 3 Color Laser Kit $44.50 most well -heeled stations 318.05, 328.025, 381.3, LC7 40 Watt Burning Cutting Laser Pleas $20.00 RUB4 Hi Powered Pulsed Drilling Laser Plans $20.00 around the nation. For the 390 9, 290.9, 398.2, 315.9, LGU40 1 to 2mw HeNe Vis Red Laser Gun Assembled $199.00 most part, the operations 322.6, 358.3, and 251.1 MHz. LLS1 Laser Lite Show -3 Methods Plans $20.00 SD5K See in the Dark Kit $299.50 on those frequencies will There are dozens of others EML1K Electromagnetic Coil Gun Kit 569.50 MCP1 Hi Velocity Coil Gun Plans $15.00 continue to be conducted in use, but if your scanner is LEV1 Levitating Device Plans $10.00 "in the clear," and therefore put into AM mode and EH1 Electronic Hypnotism Techniques Plans $10.00 HIGH VOLTAGE AND PLASMA DISPLAY DEVICES still will be easily monitored. can't pick up activity on HVM7K 75,000 Volt DC Variable Output Lab Source Kit $149.50 The frequency ranges most of those frequencies, 1053K Ion Ray Gun Kit, project energy without wires $69.50 0109K 129/115 VAC Hi Out Neg Ion Generator Kit $34.50 used by Remote Pickup then the problem might in- EMA1K Telekinetic Enhancer/Electric Man Assembled $99.50 LG5K Lightning Display Globe Kit $54.50 Broadcast stations are: volve more than just the BTC1K Worlds Smallest Tesla Coil Kit $49.50 25.87 to 26.47 MHz, 152.87 indoor antenna system. But BTC3K 250KV Table Top Tesla Coil Kit $249.50 BTC5 1.5 Million Volts Tesla Coil Plans $20.00 to 153.35 MHz, 160.89 to don't forget to use AM JL3 Jacobs Ladder -3 Models Plans $15.00 GRA1 Anti Gravity Generator Plans 510.00 161.76 MHz, 450.01 to mode in this band. PFS20 Plasma Fire Saber Assembled 869.50 450.925 MHz, and 455.01 to DP120 Dancing Plasma to Music and Sounds Assembled $79.50 455.925 MHz. Some fre- FREE FREQUENCIES! SECURITY AND PROTECTION DEVICES ITM10 100,000 Volt Intimidator up to 20' Assembled $129.50 quencies below 162 MHz We always get a lot of IPG70 Invisible Pain Field Blast Wave Gen Assembled $74.50 PSP4K Phasor Sonic Blast Wave Pistol Kit $59.50 are also shared with other requests from readers for us LIST10 Infinity Xmir, Listen in Via Phone Assembled $199.50 radio services. to suggest or recommend TAT30 Automatic Tel Recording Device Assembled $24.50 VWPM7K 3 Mi. FM Auto Tel Transmitter Kit $49.50 hot scanner frequencies. FMV1K 3 Mi. FM Voice Transmitter Kit $39.50 HGD1K Homing/Tracking Beeper Transmitter Kit $49.50 FROM OUR READERS From time to time we are EASY ORDERING PROCEDURE TOLL FREE 1 -800- 221 -1705 Dave Weir, N9HQZ, is sta- lucky enough to latch onto or 24 HRS ON 1.803 -673 -4730 or FAX IT TO 1603- 672 -5406 VISA, MC. CHECK, MO IN US FUNDS. INCLUDE 10°/, SHIPPING. ORDERS tioned at an Air Force Base a limited supply of the $100.00 8 UP ONLY ADD $10.00. CATALOG 51.00 OR FREE WITH ORDER. in Florida. He wrote to tell us "Scanner Log," which is a that he enjoys monitoring useful directory of almost INFORMATION UNLIMITED P.O. BOX 716, DEPT. PE, AMHERST. NH 03031 all of the base's VHF traffic, 200 busy nationwide scan- and can easily pick up the ner frequencies -federal, F -16 traffic in the 118- to -137- aeronautical, maritime, mili- MHz VHF aeronautical tary, public safety, etc. It band. His problem is that also has almost 200 HF Be an FCC F -16's also use the 225- "ute" frequencies. We now to- 400 -MHz UHF aero- hove another supply on LICENSED nautical band, and the hcnd and will be happy to ELECTRONIC TECHNICIAN! F -15's are exclusively in the fill requests for them as long UHF aeronautical band, but as our supply lasts. They are Dave can't seem to get any free, but to get one you reception at all in the 225 - must furnish us with a Earn up to to- 400 -MHz band. stamped (U.S.), self -ad- iff $30 an hour For starters, Dave can't dressed, long envelope for and more! o use an outside antenna. us to send it to you. These Jt1t° Second, Dave doesn't know directories are nice. Get Learn at home in spare time. No previous experience needed! what mode is used: AM, 'em while we have 'em No NFM, or WFM. Reception in available. They always go costly school. No commuting to class. The Original Home -Study course prepares this band is always of inter- fast. you for the "FCC Commercial Radio- est, but never ceases to Our address for "Scanner telephone License." This valuable license is your to of baffle scanner owners. Logs" and for questions and professional "ticket" thousands exciting jobs in Communications, Radio - Military aeronautical other mail is: Scanner TV, Microwave, Maritime, Radar, Avionics communications between Scene, Popular Elec- and more...even start your own business! You don't need a college degree to qualify, 225 and 400 MHz are al- tronics, 500 -B Bi- County but you do need an FCC License. ways in AM mode. For local Bivd., Farmingdale, NY No Need to Quit Your Job or Go To School reception, any standard 11735. As always, your corn - This proven course is easy, fast and low scanner used for ments and suggestions, or cost! GUARANTEED PASS You get your antenna FCC License or money refunded. Send for public -safety UHF frequen- questions on scanner re- FREE facts now. MAIL COUPON TODAY! cies should suffice, but an lated topics are welcome. indoor antenna would Send your correspondence comman0 PRODUCTIOnS FCC LICENSE TRAINING, Dept. 100 probably be given a lot of to the above address, and P.O. Box 2824, San Francisco, CA 94126 help with the addition of a don't forget to join us here Please rush FREE details immediately! preamplifier such as GRE again next month. NAME (D ADDRESS ZIP CITY STATE 83

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www.americanradiohistory.comAmericanRadioHistory.Com SLOT MACHINE VACUUM TUBES ATTENTION! (Continued from page 39) (Continued from page 44) diameter of the fiber-optic cable for a The Marconi Company admitted its snug fit, and the other holes should fit guilt and was prohibited from further ELECTRO!A the hardware you're using. infringement. On September 20, 1916, a Attach a U- shaped mounting brack- U.S. District Court ruled that de Forest et to the coin slot as shown in Fig. 8. Fit and his company similarly had violated T Cr-,82 the emitter assemblies on one side of the Fleming patent. In short, neither the E ARN YOUR \ r ) the coin slot and the detectors on the Lee de Forest Company nor the Mar- other. Now simply twist and solder them coni Company could manufacture tri- B.S.E.E. to the leads coming from the circuit ode audions without infringing on the board. Follow the polarity indications other's patent. DEGREE supplied with the exact parts you use in This legal impasse was not resolved THROUGH HOME STUDY your circuit. until after World War I. During the war, Our New and Highly Effective Advanced- Place- ment Program for experienced Electronic Tech- Make sure that the circuit is counting however, Forest was granted legal de nicians grants credit for previous Schooling and change properly before installing it in- immunity to manufacture grid audions Professonal Experience, and can greatly re- duce the time required to complete Program and side a cabinet. Since this article is really for the United States Government. reach graduation. No residence schooling re- about the electronics, we will not go quired for qualified Electronic Technicians. into the details on how the cabinet was Legacy of the Audion. Once the tri- Through this Special Program you can pull all of the loose ends of your electronics background assembled, but the basic measure- ode audion's capabilities for amplifying together and earn your B.S.E.E. Degree. up- ments are shown in Fig. 9. The elec- and oscillating were discovered, the grade your status and pay to the Engineering Level. Advance Rapidly! Many finish in 12 tronic circuitry and the slot assembly development of regenerative and su- months or less. Students and graduates in all 50 mounts inside the top of the unit. The perheterodyne receivers quickly fol- States and throughout the World. Established Over 40 Years! Write for free Descriptive Lit- top and bottom half of the bank are lowed. Commercial radio broadcast- erature. attached with hinges to allow empty- ing began shortly thereafter. In just a ing of the change compartment and few years, the triode vacuum tube was COOK'S INSTITUTE access to the reset button. The top half joined by its more sophisticated OF ELECTRONICS ENGINEERING of the bank has a fairly large cutout in its and relatives to make possi- CIE 4251 CYPRESS DRIVE base to allow the coins fall through into ble even more sophisticated electronic E JACKSON, MISSISSIPPI 39212 the bottom compartment. circuits. CIRCLE 13 ON FREE INFORMATION CARD

This publication is LEARN v ÇR LASER COMPUTER available in microform CLEANING /MAINTENANCE /REPAIR (Continued from page 66) EARN UIP TO $1000 A WEEK, WORKING from University PART TIME FROM YOUR OWN HOME! lot more things than I need or want. I Microfilms make use of the wordprocessor be- / Secrets I Revealed! cause of the convenience in writing International. when and where I feel in the mood, as NO Special to Tools or opposed being captive at a desktop Equipment location. The documentation is clear, Needed. the programs are largely intuitive, and file transfer is fast and easy. A privately produced quarterly news- letter devoted to the PC4 is available from Michael Posner, LUGNuts (Laser THE MONEY MAKING OPPORTUNITY User Group Nuts), 4200 Community OF THE 1990'S IF you are able to work with common small hand Drive #1514, West Palm Beach, FL tools, and are familiar with basic electronics (i.e. able

$10 to use voltmeter, understand DC . 33409, for a year. You can request a Please send information about these titles: electronics)... free sample copy. IF you possess average mechanical ability, and have a VCR on which to practice and learn. ...then we can The Laser PC4 is available directly teach YOU VCR maintenance and repair! from Laser Computer, Inc. (800 North FACT: up to 90% of ALL VCR malfunctions are due to Name simple MECHANICAL or ELECTRO- MECHANICAL Church St., Lake Zurich, IL 60047 -1596), breakdowns! for $249.95 plus shipping. The order Company/Institution FACT: over 77 million VCRs in use today nationwide! Average VCR needs service or repair every 12 to 18 phone number is 800- LASER43, or you months! can call Laser at 708 -540 -8911 for your Address Viejo's 400 PAGE TRAINING MANUAL (over 500 pho- tos and illustrations) and AWARD -WINNING VIDEO local dealer. If you get a PC4 and need City TRAINING TAPE reveals the SECRETS of VCR mainte- technical support, call Laser at State Zip nance and repair -"real world" information that is NOT available elsewhere! 800 -551 -5742 or 708 -540 -5022. For Phone( Also includes all the info you'll need regarding the more information contact the man- Call toll -free 800- 521 -3044. In Michigan. BUSINESS -SIDE of running a successful service op- Alaska and Hawaii call collect 313- 761 -4700. Or eration! ufacturer or circle No. 119 on the Free mail inquiry to: University Microfilms International, FREE INFORMATION Information Card. 300 North Zeeb Road. Arm Arbor, MI 48106. CALL TOLL-FREE 1-800-537-0589 Or write to: Viejo Publications Inc. 5329 Fountain Ave. Los Angeles, CA 90029 Dept. PE 85 CIRCLE 20 ON FREE INFORMATION CARD

www.americanradiohistory.comAmericanRadioHistory.Com THINK TANK oscillator/timer. Since my if I'm not mistaken, there (Continued from page 23) telephone- answering ma- was a request for such a Cl ? o chine is "beeperless," I circuit that appeared in our 1000/30V missed a few calls because letters column. Circuits like 12 VOLT CONTROL switch (S1) is pressed, cur- I forgot to check its blinking this one are useful for the INPUT .. rent flows through each LED. I worked out this circuit blind, as they turn light from K1 branch of the circuit. Any (see Fig. 7) to buzz on cue indicators into sound. 12V voltage over two volts will from the LED. I liked your use of the Fig. 8. This simple circuit is light LEDI. The next LED Photoresistor R1 is LM317 adjustable voltage technically called a delay -off (LED2) will light if the volt- mounted directly over the regulator. Everyone should relay timer. The relay age is 9 volts or greater, answering machine's LED take note of how it is used remains active as long as the charging current through CI LED3 will come on if the and surrounded by a tube in the power supply. If the is high enough to engage the voltage is over 10.5 volts, made of thick black paper transformer is chosen wisely, coil. and LED4 will come on if to keep out room light. Re- a variable power supply the voltage is greater than sistors R3 and R4 divide the built with That chip would 12.25 volts. Note that D4 supply voltage to keep pin be capable of providing This is one I wish I had prevents the branch ifs in 2 of the 555 just above the from 1.3 to over 30- volts. Thought of. If anyone needs from being blown out by switch -over point. That as- to figure out the time con- incorrect polarity. sumes that R1 is getting a A TIME -DELAY CIRCUIT stant of the circuit, it is a

Depending on the LED's steady amount of light from When I was building an little less than the capaci-

that you use, you might the machine's LED. With the alarm, I had to design tor's value times the

need to place a 5k potenti- LED on, RI's resistance is low. some kind of exit delay. So I resistance of the coil. If you ometer in series with the If the LED goes out, RI's came up with this simple don't know the coil's resis- circuit to fine -tune it. resistance will rise, causing circuit (Fig. 8) to do the job. tance, you can either -Mike Giamportone, a drop in voltage across R2. Only two parts are required: measure it with an ohm- Yale, Ml The drop will be fed to R5 a relay and a capacitor. meter or divide its specified Nice circuit. Those of you through C2, activating the When voltage is applied coil voltage by its coil cur- Mat might want to expand 555 monostable. to the capacitor, it charges. rent. the circuit can do so easily. The monostable activates While ifs charging, the relay Well, ifs time to close out Just use more branches the buzzer for about 0.2 remains latched. When the another month. As always, and select Zener diodes second. Each time the LED charging current falls below you should send your contri- rated at about 2-volts less flashes, the buzzer sounds. the level needed to hold butions to Think Tank, Than the voltage the Note that capacitor C1 was the relay down, the relay Popular Electronics, 500 -B branch must measure. added to the circuit to help unlatches. The higher the Bi- County Blvd., Farm- it avoid false activation the value of the capacitor, ingdale, NY 11735. ANSWERING -MACHINE from power- supply tran- the longer the relay will BEEPER sients. remain latched. Here is another applica- -Jim Drake, Albuquer- -Ricky Furtado, Toronto, CIRCUIT CIRCUS tion for the much -used 555 que, NM Canada (Continued from page 77)

Cero +9V AC supply- that's handy to 81 have on the workbench. All ¡ 05 R1 100K you need is a variable 117 - ¡ R3 7f AC transformer, 200K volt a C2 U1 power cord, fuse, switch, 4 NE555 and an output receptacle. )I R6 1K Wire the components to- gether as shown in Fig. 5.

C4 A variable AC -power ; R2 ¡ R4 - C3 i-..01 27K "100K ORZ1 source is a valuable tool to RS273-065 have when checking elec- T 7 tronics gear that's been idle for years or when smoke - -, testing a new project. lit 4-9V usually a good idea to SOURCE slowly bring up the AC line voltage to such equipment R8 i 12012 before attempting to use it. Try the surplus stores, flea markets, and hamfests first - - J when trying to locate a 12VDC WALL PLUG variable transformer-a Fig. 7. This simple circuit can turn light into sound. The 555 IC is shown connected as a good used unit is cheaper monostable timer that turns on a buzzer when light strikes RI. than a new one. 86

www.americanradiohistory.comAmericanRadioHistory.Com METER FUNDAMENTALS (Continued from page 34) Electronics. áóóKSroAE The great disadvantage of this circuit Popular is the need for a negative reference voltage. But it is very important it will 221 Popular Electronics (1991 back issues) $4.00 107 Radio -Electronics (1987 back issues) .$5.25 ensure that the operational amplifier Write in issues desired Write in issues desired 220 Popular will produce a positive output across its Electronics (1990 back issues) $4.50 106 Radio -Electronics (1986 back issues) . $5.50 Write in issues desired Write in issues desired range. A simple solution is to add a sec- 119 Popular Electronics (1989 back issues) $4.75 ond 9 -volt battery in the reverse direc- Write in issues desired REPRINTS REPRINTS tion to provide the required negative 118 Hands -On Electronics (1988 back issues) voltage. $5.00 169 Think Tank (133 Circuits) $3.50 Write in issues desired Finally, there are a myriad of digital 169A Think Tank Vol. 2 $3.00 117 Hands-On Electronics 168 Fact Cards ( #34 -66) 54.00 panel meters on the market. Feel free (1987 back issues) $5.25 to experiment with various types of Write in issues desired 168C Fact Cards ( #67 -99) $3.50 meters. Be sure to carefully consider 116 Hands-On Electronics 168D Fact Cards ( #100 -132) $3.50 (1986 back issues) $5.50 167 Designing With IC's S4.00 their input ranges and alter your op- Write in issues desired 166 Collected Works of Mohammed Ullyses Fips amp circuits accordingly. Many com- EH91 Experimenters Handbook (1991) $4.50 (62 pages, April Fools Collection) $5.00 mercial DMM's are on the market. In EH90 Experimenters Handbook (1990) $5.00 165 How to Repair CD Disc Players ... $5.00 many instances, their prices are com- EH88 Experimenters Handbook (1988 -89) $5.50 164 Modern Electrics (April 1908) $3.00 parable with analog meters. EH87 Experimenters Handbook (1987) $6.00 163 Receiving HH91 Popular Electronics Hobbyist Handbook Satellite TV $5.00 (1991) 162 Build Your Own Satellite TV Receiver Conclusion. Voltmeters, ammeters $5.00 $5.00 HH90 Popular Electronics Hobbyist Handbook 161 Descrambling (Feb. 1984) $3.00 and ohmmeters are by no means the (1990) $5.50 160 New Ideas - 42 Circuits $3.50 only types of meters available. A di- HH89 Popular Electronics Hobbyist Handbook 159 Low Frequency Receiving Techniques verse array of other meters make use of (1989) $6.00 Building and using VLF Antennas the analog and digital techniques that 126 Radio -Electronics Annual 1986 $6.00 $5.00 158 Electro Importing Co. Catalog 211 Radio -Electronics (1991 back issues) . $4.00 we have discussed here. For example, Write in issues desired (Circa 1918) $5.95 wattmeters commonly measure power 210 Radio -Electronics (1990 back issues) . $4.50 157 All About Kits $2.00 Write in issues desired to a component by measuring voltage 156 How To Make PC Boards $2.00 109 Radio -Electronics (1989 back issues) . $4.75 as well as current. Frequency meters 155 IBM Typewriter To Computer $2.00 Write in issues desired indicate the rate of a signal's repetition. 154 How To Repair VCR's $3.50 108 Radio -Electronics (1988 back issues) . $5.00 Meters can be found that specialize in Write in issues desired 150 Pay TV Decoder (1981) $3.00 measuring physical parameters such as temperature, pressure, capaci- tance, inductance, and transistor gain. 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 There are many more. ones you want. Complete the order form below, include indicate is unavailable you can order it directly from us. your payment, check or money order (DO NOT SEND We charge 500 per page. Indicate the issue (month & In spite of this diversity however, CASH), and mail to Popular Electronics, Reprint De- year), pages and article desired. Include payment in \OM's and DMM's continue to be the partment, P.O. Box 4079, Farmingdale, NY 11735. full, plus shipping and handling charge. Make checks Please allow 4 -6 weeks for delivery. payable to Gernsback Publications, fundamental electronic test instru- Inc. ments. Versatile, inexpensive, and easy to use, they can be found on just about any hobbyist's workbench. ARTICLE The material covered here repre- sents the basic technology and ap- PAGES MONTH plications used to measure voltage, YEAR current, and resistance in both analog and digital forms. Go ahead and build TOTAL PAGES @50C each TOTAL PRICE some of the circuits here. You may be surprised at just how easy (and useful) they can be. MAIL TO: Popular Electronics Reprint Bookstore, P.O. Box 4079, Farmingdale NY 11735 All payments must be in U.S. funds

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www.americanradiohistory.comAmericanRadioHistory.Com VCR REPAIRS WATCH FIS ISSUE (Continued from page 61) lems in the tape path is a loop of tan- gled tape sticking out of the cassette ON SALE APRIL 4 when its ejected. If that only happens on rare occasions, it may be caused by a problem in the cassette itself. But if it occurs on a regular basis, then suspect Radio a slipping belt or idler. After the tape stops, the P guides retract and the tape is rewound a little to pull the loose loop back into the cassette. If the drive belt E/ectronics.- - SERVICE TECHNOLOGY - VIDEO - STEREO COMPUTERS or idler to the reel hubs is slipping, then the tape may not fully rewind into the BUILD THIS cassette before the eject sequence starts. You can correct this problem as DRAM TESTER described earlier. If the VCR "eats" a tape when it mal- functions, you can sometimes still sal- vage the tape, at least for one more play so you can dub a copy. There is a small latch release button on the left side of the cassette near the doo' hinge. Press in on the latch release and lift up the door. Now put your finger into one of the reel holes on the bottom of the cassette and turn the reel to rewind the tape into the cassette. Try to smooth out any wrinkles or creases as you go. Some tape damage isn't obvious un- less you open the door on the cassette. Plus: * Hardware Hacker A crinkled or scalloped edge on the * Audio Update top or bottom edge of the tape can be * Video News oil * And lots More! caused by a misaligned guide or an seal on the capstan that has moved out of position. First look at the capstan. If there is a small plastic disc on the shaft, that may be the problem. The plastic disc is an oil seal. It should be positioned OUR MAY ISSUE FEATURES: directly on top of the bearing. If it rides up the capstan, it will rub against the tape and crinkle the edge. To solve this problem, push the oil seal back down BUILD A DRAM TESTER to its original position. Verify that your dynamic RAM chips are functioning properly and at the rated speed. If the capstan is fine, play a tape with the VCR case open and observe what BUILD THE PHONE -COM happens. The edges of the tape may Use your telephones as a home intercom system. be rubbing against something, or one PULSE -MATE of the guides may be out of alignment. BUILD THE Adjust the guilty part. A handheld pulse generator is a handy troubleshooting tool. Scratches that run along the length MICROCELL: of the tape are usually caused by a Is the "poor man's cellular network" the telephone network of tomorrow? foreign particle on some part of the tape transport. Using a cleaning tape may solve the problem. If not, visually inspect all of the guides and rollers. Use PLUS: Hardware Hacker Audio Update a cotton- tipped swab moistened with Video News Computer Connections rubbing alcohol to remove any dirt or accumulations you find. Don't use alco- Drawing Board And Lots More! hol or cotton swabs on the video head. Use only head cleaner and special head-cleaning swabs for that.

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PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS. JERROLD TOCOM HAMLIN (No refunds or credits for typesetting errors can be made unless you clearly print or type your ' copy.) Rates indicated are for standard style classified ads only. See below for additional OAK *ZENITH charges for special ads. Minimum: 15 words. SCIENTIFIC ATLANTA

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PRINTED circuit boards etched & drilled. Free deliv- 21 ($32.55) 22 ($34.10) 23 ($35.65) 24 ($37.20) 25 ($38.75) ery. K & F ELECTRONICS, INC., 33041 Groesbeck, Fraser, MI 48026. (313) 294 -8720. HUGE 88 page communications catalog of short- 26 ($40.30) 27 ($41.85) 28 ($43.40) 29 ($44.95) 30 ($46.50) wave, amateur and scanner equipment. Antennas, books and accessories too. Send $1.00 to: UNI- VERSAL RADIO, 1280 Aida Drive, Dept. PE, Rey - noldsburg, OH 43068. 31 ($48.05) 32 ($49.60) 33 ($51.15) 34 ($52.70) 35 ($54.25)

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Every month Monitoring Times brings ADVERTISING SALES OFFICE everything you need to make the most Gernsback Publications, Inc. 500 -B Bi- County Blvd. of your general coverage transceiver: Farmingdale, NY 11735 the latest information on international 1 -(516) 293-3000 President: Larry Steckler Make the broadcasting schedules, frequency Assistant to the President Christina Estrada most your listings, international DX reports, For Advertising ONLY of propagation charts, and tips on how to 516-293-3000 Employers Fax 1 -516- 293 -3115 general hear the rare stations. Monitoring Larry Steckler Willing workers available Times keeps you up date on publisher also to now at as little as % Arline Fishman coverage government, military, police and fire your usual cost. advertising director This is your chance Denise Haven monitor- transceiver networks, as well as tips on to get help you've advertising assistant ing everything from air -to- ground and needed, but thought you Kelly McQuade couldn't afford. credit manager with ship -to -shore signals to radioteletype, No business too large Customer Service/Order Form your facsimile and space communications. or too small. Call 1.800- 435 -0715 Monitoring private industry council 1- 800 -892 -0753 ORDER YOUR SUBSCRIP- or write National 7:30 AM - 8:30 PM EST Times! TION TODAY before another issue Alliance of Business, P.O. Box 7207, SALES OFFICES goes by. In the U.S., 1 year, $18; Washington, D.C. 20044 EAST/SOUTHEAST foreign and Canada, 1 year, $26. For Stanley Levitan, Eastern Sales Manager 259-23 57th Avenue a sample issue, send $2 (foreign, send Little Neck, NY 11362 5 IRCs). For MCNISA orders ($15 APusaad,s`Id 1- 718. 428 -6037, 1 -516 -293 -3000 ms Paauon . } Fax 1- 718- 225 -8594 minimum), call 1- 704 -837 -9200. MI D W EST/Texas/Arka nsas/Ok)a. Ralph Bergen, Midwest Sales Manager 540 Frontage Road-Suite 204 Northfield, IL 60093 MONITORING TIMES 1-708- 446.1444 Your authoritative source, Fax 1- 708 -446 -8451 PACIFIC /Mountain every month. COAST States Marvin Green, Pacific Sales Manager 5430 Van Nuys Blvd. Suite 316 P.O. Box 98 Van Nuys, CA 91401 Brasstown, N.C. 28902 1- 818 -986 -2001 Fax 1 -818- 986 -2009

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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 úQUNÌER- radio -frequency transmitters, and other how to defend against experienced SttRVEIiIANCE bugs, plus when to use disinformation to information thieves -been placed ìECHNtQi1ES 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 any hi -tech industry, or a novice B11(ì61N6 how to look for a bug, where to look for a you seeking entry into an honorable. CÑACKIÑ6 bug, and what to do when find it? avESap41N6'. Bugs of a very small size are easy to rewarding field of work in i1STÉÑIÑG - and they in a countersurveillance, you must 111 build can be placed quickly 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. HAVE YOUR continued to search just in case there were Wake up! If you are not the victim, VISA or MC CARD more bugs. then you are surrounded by countless vic- AVAILABLE The professional is not without his tims who need your help if you know how tools. Special equipment has been de- to discover telephone taps, locate bugs, or what was to he an embassy and private signed so that the professional can sweep "sweep" a room clean. residence into the most sophisticated re- a room so that he can detect voice -acti- There is a thriving professional service cording studio the world had ever vated (VOX) and remote -activated bugs. steeped in high -tech techniques that you known. The building had to be torn Some of this equipment can be operated can become a part of! But first, you must down in order to remove all the bugs. by novices, others require a trained coun- know and understand Countersurveilance tersurveillance professional. Technology. Your very first insight into Stolen Information The professionals viewed on your tele- this highly rewarding field is made possi- The open taps from where the informa- vision screen reveal information on the ble by a video VHS presentation that you tion pours our may be from FAX's, com- latest technological advances like laser- cannot view on broadcast television, sat- puter communications, telephone calls, beam snoopers that are installed hun- ellite, or cable. It presents an informative and everyday business meetings and dreds of feet away from the room they program prepared by professionals in the lunchtime encounters. Businessmen need snoop on. The professionals disclose that field who know their industry, its tech- counselling on how to eliminate this in- computers yield information too easily. niques, kinks and loopholes. Men who formation drain. Basic telephone use cou- This advertisement was not written by can tell you more in 45 minutes in a pled with the user's understanding that a countersurveillance professional, but by straightforward, exclusive talk than was someone may be listening or recording a beginner whose only experience came ever attempted before. vital data and information greatly reduces from viewing the video tape in the pri- the opportunity for others to purloin vacy of his home. After you review the Foiling Information Thieves meaningful information. video carefully and understand its con- Discover the targets professional tents, you have taken the first important snoopers seek out! The prey are stock RADIO -ELECTRONICS VIDEO OFFER PE step in either acquiring professional help brokers, arbitrage firms, manufacturers, 500 -B Bi-County Blvd. with your surveillance problems, or you high -tech companies, any competitive Farmingdale, NY 117 ì5 may very well consider a career as a coun- industry, or even small businnesses in the Please rush my copy of the countersurveillance Techniques tersurveillance professional. same community. The valuable informa- Video VHS Cassette for $49.95 plus $4.01) for postage and handling. tion they filch may be marketing strat- The Dollars You Save egies, customer lists, product formulas, No. of Cassettes ordered To obtain the information contained in Amount of payment $ manufacturing techniques, even adver- the video VHS cassette, you would attend tising plans. 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XLR Connectors (1) Precision Ther- (1) Prewired Tem- (2) Set of 100 Ce- (1) Inline Socket. mistor. Resistance perature Module. ramic Disc Capaci- -011 .. 2.99 changes in propor- tors. A variety of #274 Just add one "AA" (2) Three -Pin Plug. tion to temperature. popular styles and battery for use as a -010 2.99 Has measurement values at a bargain #274 .... thermometer. You Panel range from - 50 to price. Ratings up to (3) Socket. can also connect #274 -013 +110° C. 1000 WVDC. Stock ....3.69 simple circuits to #271 -110 . 1.99 (4) Adapter Trans- indi- e Connects (2) Surface -Mount control external #272 -801, Set 1.98 former. and devices mike to Resistors. Big 200 - cators (1) XLR -type temperatures you equipment with 1A" piece assortment! at Popular values, set. (Data included.) phone jack input. (3) of rated 1s watt, 5 %. Has 1/z" liquid crys- Assortment #274 -016 .. 11.99 (1) Ca- #271 -313, Set 4.99 tal display and 20 Electrolytic (5) Adapter Trans- Miniature (3) Ohm's Law selectable Fahren- pacitors. former. Connects and submini types in mike with 'M" plug Guide. Fast an- heit or Centigrade modes. Module is (3)¡ a variety of values to XLR jack input. swers to Ohm's law t easily panel - with ratings to 50 #274 -017 ...11.99 and parallel resist- ance problems. mounted. WVDC. (4) (5) #277 -123 ...19.95 #272 -802, Set of 20/1.99 (3), - #271 -1211 .... 495

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