197709 Byte Magazine Vol 02 09 Music and Computers

SEPTEMBER 1977 VOLUME 2, Number 9 $2.00 in USA EUIE the small systems journal PES —— =a IMSAI 8080 aa a | TESS SHSET? Circle 200 on inquiry card. SWTPC announces first dual) minifloppy kit under $1,000 } Now SWTPC offers complete best-buy computer system with $995 dual minifloppy, $500 video terminal/ monitor, $395 4K computer. STP oe eri $995 MF-68 Dual Minifloppy You need dual drives to get full benefits from a minifloppy. So we waited to offer a floppy until we could give you a dependa- ble dual system at the right price. The MF-68 is a complete top-quality minifloppy for your SWTPC Computer. The kit has controller, chassis, cover, power supply, cables, assembly instructions, two highly reliable Shugart drives, and a diskette with the Floppy Disk Operating System (FDOS) and disk BASIC. (A floppy is no better than its operating system, and the MF-68 has one of the best available.) An optional $850 MF-6X kit expands the system to four drives. Enclosed I _—— $1,990 for the full system shown above (MF-68 Minifloppy, CT-64 Terminal with CT-VM Monitor). _——_— $995 for the Dual Minifloppy $325 for the CT-64 Terminal ——— $175 for the CT-VM Monitor _——— $395 for the 4K 6800 Computer $500 Terminal/Monitor The CT-64 terminal kit offers these premium features: 64-character lines, upper/lower case letters, switchable con- trol character printing, word highlighting, full cursor control, 110-1200 Baud serial interface, and many others. Separately the CT-64 is $325, the 12 MHz CT-VM monitor $175. $250 lor the PR-40 Line Printer $79.50 lor AC-30 Cassette Interface Additional 4K memory boards at $100 __— Additional 8K memory boards at $250 smecoom CS $395 4K 6800 Computer The SWTPC 6800 comes complete with 4K memory, serial interface, power supply, chassis, famous Motorola MIKBUG® mini-operating system in read-only memory (ROM), and the most complete documentation with any computer kit. Our growing software library includes 4K and 8K BASIC (cassettes $4.95 and $9.95; paper tape $10.00 and $20.00). Extra memory, $100/4K or $250/8K. Other SWTPC peripherals include $250 PR-40 Alphanumeric Line Printer (40 characters/line, 5 x 7 dot matrix, 75 line/minute speed, compatible with our 6800 computer and MITS/IMSAI); $79.50 AC-30 Cassette Interface System (writes/reads Kansas City standard tapes, controls two recorders, usable with other computers); and other peripherals now and to come. fe - |! Southwest Technical Or BAC # Exp. Date. Products Corp. OrMc # Exp. Date. 219 W. Rhapsody, San Antonio, Texas 78216 Name. Address. London: Southwest Technical Products Co., Lid. City. State Zip. Tokyo: Southwest Technical Products Corp. /Japan eae oat ou) unt Ue n power is t ‘mount style en tell nputer nanc -onvenienc motherboard cultry to in construc d dust case. computer tion and si won't believe (+: ample pow as floppy disk driv Ty owe cr Ne J | ling you wanted: ina style and price uter Syst only $ with 21 ¢ automatic prc tion. powerful but stems wot ontrols of Noti vitches v Z-2 9, ; Computer Aystem_ , 00 bus which is supported by of manufactur aturally, all such as our 7-ch /Da our well-known BYTESA\ with its A programmer, our color graphics interface, into the S-100 bus. , LO You'll be impressed with exceller computer V PRICE s low price right technical at factory. away your der directly from the SYSTEM KIT ngth 21-cal socke one care In the Queue BUTE septemser 1977 Volume 2 Number 9 PusLisuers Foreground Wignia Pose 12 SCORTOS: IMPLEMENTATION OF A MUSIC LANGUAGE EDITOR IN CHIEF r Cat einer Software, Musio—Taylor Se aaices 30 CONTROL THE WORLD! (OR AT LEAST A FEW ANALOG POINTS) Judith Havey Peripheral interfaces—Ciarcia cee uE ATION EANAGER 62 TECHNIQUES FOR COMPUTER PERFORMANCES OF MUSIC ASSISTANT PUBLISHER Computer Music—Chambertin Debra aouettasl 84 TUNE IN WITH SOME CHIPS Christopher P Morgan Applications—Sierad cO.0r EDITOR 126 AN APL INTERPRETER FOR MICROCOMPUTERS, Part 2 PRODUCTION EDITORS Interpreter Design—Wimble Background 26 A NEW DRESS FOR KIM Design—Atkins 44 EXPANDING THE TINY ASSEMBLER Software Design—Emmerichs 54 ONE-SIDED VIEW OF WIRE WRAP SOCKETS Hardware—Rampil 102 THE NOVAL 760 System Description—Hauck-Nash 112 NOTES ON INTERFACING PLAYER PIANOS Music Peripherals—Helmers 122 NOTES ON ANATOMY: THE PIANO’S REPRODUCTIVE SYSTEM Software History—Morgan 190 WALSH FUNCTIONS: A DIGITAL FOURIER SERIES Interface Technotogy—Jacoby Nucleus 4 in this BYTE 6 Reflections on Entry into Our Third Year 8 Letters 2 Alphanumeric Music 50 Review: Heuristics SpeechLab 59 Technical Forum: Personal Computer Network Adding New Transcendentals to ited BASICs On Finite State Machines and Their Uses Comments on Floating Point Representation 97 Ask BYTE 110, 210, 216 What's New? 166, 200 BYTE's Bits 172 BYTE’s Bugs 186 Clubs, Newsletters 202 Book Reviews 222 Classified Ads 224. BOMB 224 Reader Service BYTE 1s published monthly by BYTE Publications Inc, 70 Main St, Peterborough NH 03458, Address all mail except sub: phone (603) 924.7217. Address all editorial correspondence to the edit 1e above address. 1ars will be returned if accompanied by sufficient first class postage. Not responsible for lost manu- scripts or photos. Opinions expressed by the authors are not necessarily those of BYTE. Address all subscriptions. change of address, Form 3579, and (ulfillment complaints to BYTE Subscriptions, PO Box 361, Arhagton MA 02174; phone (617) 646-4329. Second class postage paid at Peterborough NH 03458 and at additional mailing offices-USPS Publication No. 102410, Subscriptions are $12 for one year, $22 for two years, and $32 for three years in the USA and its possessions. Add ‘$8.50 per year for subscriptions to Canada and Mexico. $25 for a one year subscription by surface mail worldwide. Air deli very to selected areas st additional rates aveilable upan request. $25 for a one veor subscription by air delivery to Europe, ot DM 60,— for a ane year subscription through our European distributor in Darmstadt, West Germany. Single copy price is ‘$2.00 in the USA and its possessions, $2.40 in Canada and Mexico, and $3.50 in Europe or OM 8,~ through our European dis tiburor in Darmstadt, West German Foreign subcriprions and sales should be remitted in United Stares funds. Printed in United opyright ©1977 by BYTE Publications Inc. All rights reserved. Karen Gregory Nancy Salmon ADVERTISING Debra Boudriesu, Director Noreen Bardsley Virginia Peschke EDITORIAL ASSISTANT Ingrid Nyland PRODUCTION ASSISTANT Cheryl Hurd NEW PRODUCTS EDITOR Elizabeth Ataaugh DEALER SALES Ginnie F Boudrieau CLUBS, PAPERBYTES: Peter Travisano TRAFFIC MANAGER Edmond ¢ Kelly Ir ART Wai Chiu Li Ellen Shamonsky SPECIAL PRODUCTS: Floyd W Realing Medellin Stenhens David Wormak EXECUTIVE SECRETARY Patricia Clark RECEPTIONIST Jacquetine tarashaw DRAFTING. Douglas Gles Stephen Keuse Lynn Mato Bill Morelte Dorothy Shamonshy TYPOGRAPHY. Custom Marketing Resources Inc Goodway Graphics PHOTOGRAPHY Ed Crabieee EDITORIAL CONSULTANT Daniet Fylstra ASSOCIATES Walter Banks Steve Ctareia David F ylstra Portia byaaeson FOREIGN DISTRIBUTOR Pan Atlantic Computer Systems Gmbti Frankturter Sir 78. D6} Darmstadr West Germany (0.61 51} 29 29 23 ADVERTISING SALES REPRESENTATIVES National: Parker & Short T Lakeside Ottice Park Wakefield MA 01880 (617) 246-2293 Southern California: Buckley /Boris Associates Inc 912 South Barrington, Suite 202 Los Angeles CA 90049, (213) 826-4621 Northern Californi Jules E Thampson Inc Hearst Building Suite 1111 San Francisco CA 94103 (415) 362-8547 In This BUTE Experimenting with music on your computer can be very rewarding. If you're looking for a streamlined way to input musical material into your system, look no further. Hal Taylor shows you how in SCORTOS: Imple- mentation of a Music Language. Who knows, with SCORTOS you could have your synthesized concerto for alpenhorn and orchestra up, running and debugged by next week. A naked microcomputer board is unprotected from a harsh environ- ment. In his article this month, R Travis Atkins turns couturier as he fashions external garb in the form of A New Dress for KIM. Steve Ciarcia returns this month with a combjnation of tutorial ideas and practical details so characteristic of his style. Read Steve’s Control the World! (Or at Least a Few Analog Paints) to review digital to analog con- version, and learn how BASIC can be used to compute and represent wave- forms through a converter using a scope as a display. 2 Flutes ot fe TS ort at TRS P02 K2- T3/4 O3 Fé G4 AB. F16 / O4 CB. OB BIG O2 F4 BA / DS. a eee POS K2- T9/4 09 F2.A/ FA F2A/ F24/ FLA/ P24 / A Tiny Assembler need not have tiny features, as Jack Emmerichs ex- plains in his article on Expanding the Tiny Assembler. Jack adds structured programming features and incremen- tal improvements to the Tiny Assem- bler design he described in April and May issues of BYTE this year. By reorganizing the symbol table to add the “‘begin” pseudo operation, “Tiny” takes on a number of “big” features while preserving practical operation as Version 3.1 in under 4 K bytes of memory. Looking for a very simple way to build a wire wrap board? Ira Rampil has an idea in A One-Sided View of Wire Wrap Sockets. Are you interested in making music with your computer? Hal Chamberlin’s A Sampling of Techniques for Com- puter Performance of Music is one of the best ways to get acquainted with this fascinating field. The article will give you complete directions for creating 4 part harmony on your microprocessor for a very modest investment. Get out those 4 voice fugues that have been languishing in your music drawer and bring them to life! Did you ever want your computer to sing you a lullaby? Well, as Ted Sierad points out, it’s not too hard to do so if you Tune In With Some Chips, using the circuit and software he de- scribes, The roster of '‘complete” computer systems for the amateur computing person expanded considerably with the introduction of the Noval 760. Turn to an account by designers Lane T Hauck and James D Nash, System Description: the Noval 760, for details of the philosophy and overall design behind this product. page 12 A double feature written by Carl Helmers and Chris Morgan of BYTE covers key details of an interesting musically oriented peripheral which can be added to the personal com- puter: acoustic pianos with pneumatic player actions. Notes on Anatomy: The Piano's Reproductive System gives global morphology of a Duo-Art upright reproducing piano. Notes on Interfacing Pneumatic Player Pianos covers some details of how to engineer a computer interface for the pneu- matic control lines using valve ele- ments manufactured for the pipe organ industry, With this issue, readers will note the continued progression of information on APL, and several articles intro- ducing the theme of music represen- tation and performance with com- puters. Readers can look forward to further information on these themes in future issues. APL is one of the most interesting high level languages around these days. If you want to continue learning what goes on in an APL interpreter, read part 2 of Mike Wimble’s An APL Inter- preter for Microcomputers. Here Mike covers the expression evaluation sec- tions of the interpreter. Many people are familiar with use of orthogonal basis functions such as sines and cosines to compute arbitrary waveforms. But how many readers have heard of Walsh Functions: A Digital Fourier Series which forms arbitrary repetitive waveforms as weighted sums of digital waveforms? Read Benjamin F Jacoby’s tutorial to find out a bit about these functions and their generation. Announcing the West Coast's largest Personal Computing Show. April 28, 29, and 30, 1978 at California's brand new Long Beach Convention Center. This is a selling show with 180 booths (each draped, carpeted and with 500 watts of electricity). Three full days of conference sessions. There will be home brew exhibits, exhibitors lounge, inquiry badge system, computerized registration, a newsroom, and a full blown advertising and promotional campaign to bring you thousands of qualified buyers. 1 wouldn't miss it | for anything. Send me the show kit: Name:. Title: Company:. Address: State: Zip Code: Phone:. Call: (714) 973-0880 Or mail this coupon: PERCOMP 78, ] 1833 E. 17 St., Suite 108, Santa Ana, CA 92701. Sign early, corner booths are limited. [sz ws | ES SS eee Fr Circle 281 on inquiry card. Ecitoria BYTE’s 0,02 Centennial Reflections on Entry into Our Third Year Articles Policy AVIL is continually seeking quality manuscripts written by individuals whe are woplying personal systems, or who have Arwwtedae which will prove usetul to our readers. Manuscripts should have double \naced typewritten texts with wide margins. Aumbering sequences should be muintuined weparatel tor figures, tables, photos and Histings, Higures und tables shoubd be pro vided on sepurate sheets of paper, Photos of techical subjects should be taken with unitore lighting, sharp tocus and should be supplied iv the form of clear glassy black und white of colar prints (if you do not have access to quality: photography, items to be photographed can be shipped 10 us Ih auuny cases). Computer listings should be supplied using the darkest ribbons possible un aew fot recycled) blank white com: puter Farms or bond paper, Where porsibte, /Mf tike guthors 10 supply a short mt about their buckyround und Articles which are accepted ure typically ucknowledged with 0 binder «heck 4 10 8 weeks utter receipt, Honorarums tor urtictes ure based upon the technical quality. und suitabitine for BYTE'S readership ond ace typically $25 10 $50 per typeset mayarine page. We recommend that authors record thei aume and address intormation redun- dantly on materials submitted, and thot w rerumn envelope with postage be supplied mv the event the articte és not accepted. By Carl Helmers The September 1977 BYTE marks the end of the second year of our publication’s existence in the public eye, although actual work on the magazine began at the end of May 1975. Since that time, the phenomenon of personal computing has expanded con- siderably as more people become aware of it through mass media publications, radio and television shows, trade fairs such as the First West Coast Computer Faire and the National Computer Conference. Good sense says a peak must be reached in any new and ex- panding marketplace, but to date we have seen no signs of the traditional ‘‘shakeout” (intense competition such as that which occurred recently in the calculator and watch marketplaces). For whatever reasons, a few firms have fallen by the wayside, but the general trend still remains one of expan- sion and exploration, to the ultimate benefit of the user of personal computing products who is presented with new options and lower prices for older options. The “appliance” computer, a complete system presented in an assembled and tested package is on the threshold of its ultimate dominance in the general purpose personal computer field: from the high end, moving down in price, we find products like the Apple-Il and the Commodore PET 2001 machines; from the low end, moving up in function at the same price, we find the increasing versatility and capability of pro- grammable calculators such as the newly announced Texas Instruments SR-59 with its optional ROM software modules and expanded printing and magnetic card peri- pheral capabilities. And for the discrimi- Continued on page 95. 6 Rated |G) Great Locations Now Open: 22634 Foothill Blvd. Hayward, CA 94542 (415) 538-8080 6840 La Cienega Blvd. Inglewood, CA 90302 (213) 776-8080 24001 Via Fabricante Mission Viejo, CA 92675 (714) 770-0131 4233 Convoy Street San Diego, CA 92111 (714) 560-9912 104 W. First Street Tustin, CA 92680 (714) 544-0542 50 East Rand Road Arlington Heights, IL 60004 (312) 255-6488 9511 No. Milwaukee Ave, Niles, IL 60648 (312) 967-1714 813-B Lyndon Lane Louisville. KY 40222 (502) 425-8308 16065 Frederick Road Rockville, MD 20855 (301) 948-7676 2 De Hart Street Morristown, NJ 07960 (201) 539-4077 1612 Niagara Falls Blvd. Buffalo, NY 14150 (716) 836-6511 225 Elmira Road. Ithaca, NY 14850 (607) 277-4888 6439 Westheimer Road Houston, TX 77057 (713) 977-0909 Opening Soon: Huntsville, AL San Francisco, CA San Jose, CA Thousand Oaks, CA Detroit, Mi Nashua, NH Austin, TX Franchise Opportunities Available—Contact: E. E. Faber, President ComputerLand Corp. 1922 Republic Ave. San Leandro, CA 94577 (415) 895-9363 Circle 202 on inquiry card. The Best Game in Town. Welcome to ComputerLond. An incredible adventure into the world of personal computers. A one-of-a-kind shopping experience. Each ComputerLand store presents everything you ever wanted to know about computers. And then some. Take our Game Room, for starters. You'll find excitement for the whole family in our endless variety of challenging computer games. You can battle the Ktingons In an out-of-this-world game of StarTrek. Create an elec- tronic work of art with a computer controlled TV, Test your skill In a game of computerized hangman. You can even plot your biorhythm. But we're more than just fun and games. Each ComputerLand store offers a knowledgeable and person- able staff of professionals to serve you. Plus the greatest avail- able selection of micro components. Whether it’s a data processing system for your business or a computer controlled sprinkler system for your home, you'll find whatever you need at ComputerLand. Read on, Genuine Service. We want to supply you with the one system that’s right. Rather than a com- plete system that isn’t. Or a limited system that is. That's why, at Com- puterLand, you deal with real professionals who are also real people. People who speak your language ... In addition to BASIC, COBOL or FORTRAN. People, in short, who can offer both the novice and the old hand the same expert guidance in selecting the optimum system he or she needs. Yet, assisting in the purchase is only the beginning of ComputerLand’s service. If the kit you bought requires a little more do-it-yourself than you yourself can do, we provide assembly assistance, {f that complex program proves to be just that, we provide programming assistance. And if your system breaks down, our In-store service department will get you back up and running. Right now! Great Selection. Your first stop at ComputerLand may well be your last stop, ComputerLand offers the finest quality and a <4 ‘Jargest selec- ton of all the major brand names. Like Apple Computer, Cromemco, DEC, Diablo, Hazeitine, ICOM, IMSAI, Lear Siegler. National Semiconductor, North Star, Texas Instruments, Vector Graphics and more. Plus a comptete inventory of tools, books and accessories, What's more, at ComputerLand, we deal in product. Not promises. Our Inventory is on our own shelves, Rather than the manufacturer’s. So you can take defivery on tomorrow's com- ponents today. Which means, simply put, that at ComputerLand, you get exactly what you want, Exactly when you want it. Be Our Guest. Begin with the grand tour of our exhibit areas, ‘“Test- drive” any of our Individual systems. Then tell us your needs. We'll sit down and talk about the system that’s right for you. It’s as easy as that at ComputerLand. The great computer store. RATED G. Call orwrite forthe address of the ComputerLand store nearest you. Franchise opportunities available. Computerland 4922 Republic Avenue, San Leandro, CA 94577 (415) 895-9363 Letters REGARDING INTERFACING THE IBM SELECTRIC KEYBOARD PRINTER My congratulations to Mr Fylstra on a job well done in his June article in BYTE. | spent half a year, back in 1970, ‘on designing the interface for the 735 Selectric to the Microdata 800 Mini- computer, and in the process went through many of the discoveries revealed in the article. As the man who serviced our IBM 10 printers {an ex-IBMer) said to me, that machine is a triumph of development over engineering! One fruit of my work was a 2048 bit ROM which we custom programmed to do the ASCH to “bail code” conver- sion and back, without recourse to a software lookup table. It is still available as the MMS230KP from National Semi- conductor. But note that it handles only the “correspondence” version of the Selectric: our machine needed full upper and lower case graphics. Dan’s comments on using the ‘a’ and “'b" contacts for figuring ready /busy of the printer are quite valid. One thing we learned was that allowing the clutch to stop between characters does lead to shortened tife between adjustments. Back in 1970 we used a TTL voting cir- cuit to read the contacts, because they bounced so much, and accurate timing is essential for “wide open” running. ‘One last point: The contacts are open reed, and must be “wetted” by using a current several times higher than the 5 mA shown, else they get dirty very quickly. Good luck to all ye who pass this way again! Richard Percival National Semiconductor GmbH Industriestrasse 10 808 Furstenfeldbruck GERMANY 1S BUS COMPATIBILITY NEEDED? | have recently noticed that many people ascribe a certain importance to a product if iis “Altair (S-100) compat- ible." This should not be unusual; many people own Altair bus based systems and wish to buy only what is useful to them. But | am angered by people who auto- matically downgrade a product that is not $-100, even if they do not own a system themselves. They seem to think that compatibility and board inter- changeability rank high on the list of priorities for a "good" computer system. This is typical of most of the hobby market. I feet that the next few years will bring a change in that viewpoint. As computers become more and more common, processor power and built-in features will take precedence over bus compatibility. This is especially true in the consumer market. Who, in the early days of radio, would buy a separate tuner, amplifier and speaker assemblies if they could buy a complete, assembled unit? Consumers would never consider buying and inserting full size printed circuit boards into a system; they will rarely care whether they have a separate video board of a video section or a single board computer if it works. This is not to say that the Altair (5-100) design will vanish, The large number of systems and boards available makes it a great system for someone who knows what he or she is doing. For ail others, a system that is self-enclosed and requires no expansion for basic 10 de- vices (tape recorder, TV set) will be more popular. If we are to go anywhere with home computers, as designers we must under- stand what consumers expect them to do; we must not force them to adapt to our insufficiencies; we must learn to provide a useful and well-integrated product, € David Espinosa 21191 Gardens Dr Cupertino CA 95014 The first automobiles were not truly consumer oriented, either, but as the public became educated in the uses of the product and as manufacturers learned more about the product and its design, the personal transporter became today's ubiquitous mechanism. In the continuing evolution of the personal computer, a similar user orientation is in the works and presently unfolding as innovative technological entrepreneurs gain experience and refine the product concepts. 1BM 360/370 EMULATIONS Concerning Tom Koon’s letter in the May 1977 BYTE about 360/370 emula- tion: this has already been done in at least one instance that | know of. Roger Appel of Interdata recently mentioned that his company took on this project a few years back. Interdata’s Boston area phone is (617) 890-0557, and as to the price, don’t count on it being cheap. | Howell Mitchell Jr Dynamics Research Corp 60 Concord St Wilmington MA 01887 A PUZZLE: DELETING THE DELIMITER { have comments to make regarding Dave Chapman's problems with deli- miting the delimiter (May 1977 BYTE). There is a similar but even more an- noying problem if you're working with an editor program which has a delete character, The question is, how do you change ARIZONA INDIANA Byte Shop Data Group Tempe Indianapolis (602) 894-1129 (317) 849-5280 CALIFORNIA KENTUCKY Qrange Computer Ctr | Cybertronics Costa Mesa Louisville (714) 646-0221 (502) 499-1551 Byte Shop Ceviche MASSACHUSETTS (213) 371-2421 ‘American Used Gytes ‘Shop Boston ew - (415) 969-5464 (617) 261-1100 Computer Mart MINNESOTA Orange Mictoprogramming (714) 633-1222 nevi Byte Shop (613) 896-3610 vasadena NEW HAMPSHIRE (213) 684-3311 ‘Computer Marl Byte Shop Nashua Santa Barbara (603) 883-2386 (605) 966-2538 NEW JERSEY Byte Shop Santa Ciara apne Mert (408) 249-4221 (201) 263-0600 eros NEW YORK (714) 565-8008 cmeieo ‘Sound Byte Shop San Rafael ei2). 468-7067 (415) 457-9311 cone Mart ‘Computer Room Saree (212) 686-7923 (408) 226-8384 NORTH CAROLINA Byte Shop Digital Dynamics Tarzana Charlotte (213) 343-3919 (704) 3741527 Tech-Mart eM PENNSYLVANIA (213) 344-0153 Byte Shop Brymar Byte Shop (215)525-712 Thousand Oaks (805) 497-9595 SOUTH CAROLINA Byte Snop Carolina Computers Columbia (415) 993-6252 (B03) 798-6524 Byte Shop TEXAS Hesirainster Micro Store (714) 894-9131 a COLORADO (214) 231-1096 Prime Radix Microtex Denver Houston. (203)573-5942 (713) 780-7477 FLORIDA Speer Terminal Byte Shop (ergeee- 1638 Miami (305) 264-2983, WISCONSIN The Computer Store pegeon Computer Jacksonvilie (904) 725-8158 (08) 265-5552 ILLINOIS CANADA ty Bitty Machine Computer Mart Evanston Toronto (312) 328-6800 (416) 484-9708 Numbers Racket Computer Place mpaign Toronto (217) 352-5435 (416) 598-0262 ‘Champaign Computer ‘Champaign (217) 359-5883 6741 Variel Ave., Canoga Park, CA 91303 U.S.A. Tel. (213) 348-1391 acrsonot Pentec Computes Corperaten Circle 203 on inquiry card. More Uses People from every walk of life are adding iCOM® Floppy Disks to their microcomputers for such diverse tasks as payroll, inventory control, mailing lists, game playing, record keeping, parts ordering... We've uncovered some innovative applications, too: The sailboat architect who puts equations and algorithms on an iCOM disk to test his nautical theories; the student who has auto- mated a bowling alley; the iCOM dealer who designed an environmental control system for a university. More Speed These users have found iCOM floppies to be much faster and more versatile than cassette or paper tape. With iCOM, programs can beloadedin — seconds; files updated in minutes; hundreds of pesame can e stored on | asingie disk. ed More Models iCOM has Frugal Floppies™, Dual Floppies, Microfloppies™ (using the new 5%" diskette), and other new approaches to floppy disk systems. Each Is hardware and software compatible with Altair™, IMSAI, Poly 88, Sol-20 and other microcomputers using the Altair S-100 bus format. — More Software Then there's ICOM’s famous software: Powerful field-proven FDOS-II with macro-assembler, string- oriented text editor, and file manager. Plus easy-to-use compatible 8K Disk BASIC. Each with super features such as: named variable length files, auto- file create, open and close, multiple merge and delete . . . and more. More Backup We've been building floppies for microcomputers for more than 3 years. Long before the rest. Thousands of systems are operating perfectly in the field. And we're part of Pertec Computer Corporation, one of the largest manufacturers of peripherals, microsystems, data entry products and Hale processing) systems. We'll be around whenever you need us. More Dealers Maybe not in quantity, but in quality. We've chosen our dealer network carefully to assure you of assistance every step of the way. Our prices are right. Our delivery is fast. Our dealers are experienced and \ knowledgeable. \ Must Reading oc a “What a Flop; st Can Do for You" is must reading. Send for yours today or visit your dealer. ——— | ©1977, Pertec Computer Corporation icc’ MICROPERIPHERALS adivision of Pertec Computer Corporation 6741 Variel Ave., Canoga Park, CA 91303 U.S.A. Tel. (213) 348-1391 TWX 910-494-2788 a detete character, when typing the char- acter deletes the previous character? A variation of this exercise is obtained when you suppose that somehow the character for “change” has been set to be the character for ‘“‘delete.”” These are amusing puzzles, and it can be left to the reader to figure out how to get into and out of these situa- tions. EG Johnston Computer Sciences Corporation Silver Spring MD 20910 MORE ON SR-52/SR-51 INTERNALS 1 am interested in interfacing the SR-52 with some other equipment and ooo AN IMPORTANT WARNING ABOUT THE ELEMENT MERCURY AND ITS COMPOUNDS The June 1977 issue of BYTE arrived recently and Mr Pasken’s letter on ob- taining mercury caught my eye, causing me to go back and read Mr Firth’s article ‘on weather prediction in the December 1976 issue, page 62, which | had not read the first time around. | fear that Mr Firth, and perhaps Mr Pasken, are under a misapprehension as to the nature of the hazards of contact with metallic mercury. As an Industrial hygienist, feel impelled to set the record straight and to comment on Mr Pasken’s method of obtaining mercury. A note In Mr Firth’s article states that “mercury can be harmful if you breath the vapors, swallow it or other- wise get it in your body. But there is little danger from . . . putting your hands in it." It Is true that mercury vapors are harmful; however, the rest of the state- ment {| have quoted is, by and large, not true for metallic mercury, which Is what ‘one would use in a barometer. Metallic mercury is readily absorbed through the skin. On the other hand, if swallowed it passes virtually without absorbtion through the gastrointestinal tract and presents very little hazard to the indi- vidual. (One should, of course, try to avoid swallowing it anyway.) Mr Pasken does not address the hazards of mercury, but his method of ‘obtaining It is one which, in view of those hazards, | would not recommend. In breaking open mercury switches and cleaning the mercury by passing it through a hole in a filter paper, one's tendency would be to work with the material rather close to the face. This could result in considerable breathing of mercury vapors. (Remember, most readers will not be doing this in a chemistry lab equipped with adequately performing fume hoods.) In addition, the potential for skin contact is obvious- ly quite great. Mercury, if spilled on a floor, can be quite difficult to clean up. Sweeping will only break it into smaller and smaller drops which will lodge in cracks and in- have gathered a little (very little) infor- mation which might help William D Lewis (letters of June 1977 BYTE) with his SR-52. First, the SR-52 and SR-51 terminal strips appear to be similar. The SR-52 has a TMCOSOINL which they call UT and a TMCOS24NL which appears to be a version of the TMC- 0523NS-S, but it is called U2. The terminal strip connectors in the order shown in the June BYTE are: NC, D12, 02, Ext, IDLE, IRG, D15, DO, 01, KN, KP, KR. The pinouts of the TMC- OSOINL are: 1(DPT), 2(SB), 3(SA), 4(SF), 5(SC), 6(SD), 7(SE), 8(KT), 9(KS), 10(KR), 11(KQ), 12(KP), Continued on page 174 crease the cleaning problem. Vacuuming is a preferred method, But most people don’t keep laboratory aspirators In their homes, and contaminating the family vacuum cleaner with mercury is hardly an ideal solution. There are also commer- cial materials which when sprinkled onto a mercury spill create mercury com- pounds which can be swept up, but | doubt that many people have such things available to them at home. And frankly, should mercury be spilled on a rug, | can’t imagine how it could be cleaned up completely. There are a few other points to con- sider. If mercury is spilled on your floor, it is a greater hazard to your small children and pets than to you. They are down there where the vapors are stronger and are in more intimate con- tact with the floor, and potentially with the spill. Also, mercury is fun to play with. Children, and adults too, like to coat coins with it or watch a droplet roll around the palm of a hand. Such recrea- tion leads to skin contact, which should be avoided, Finally, should you be working with mercury in your home in winter, and your home Is not heated with forced air, the room in which you work will not have much ventilation and the mercury vapor concentration will be higher than otherwise. 1 should mention that the above statements on the hazards of mercury are made with respect to metallic, or elemental, mercury. Mercury compounds can also be hazardous in other modes of exposure. tn summary, metallic mercury is a harzardous material, both by breathing the vapors and by skin contact. If you must work with It, avoid skin contact, and, if you don't have access to a chem- istry laboratory, work with it outside or in a well-ventilated room. Store mercury, and your open dish mercury barometer, where children, pets and other curious people cannot get at it, again, preferably in a well-ventilated room. Peter L Zavon 57-01 Fox Run Plainsboro NJ 08536 OUR DEALERS NORTHEASTERN STATES Computer Workshop, Rockville, MD; Computer Mart, Waitham, MA; Iselin, NJ; Hoboken Computer Works, Hoboken, NJ; Audio Design Electronics, New York, NY; Byte Shop East, Levittown, NY; Computer Comer, White Piains, NY; Computer Enterprises, DeWitt, NY; Fayetteville, NY; Computer Mart of New York, Now ‘York, NY; Computer Shoppe, Middle Island, NY; Ithaca Audio, Ithaca, NY; Byte Shop, Bryn Mawr, PA; Personal ‘Computer Corp., Frazer, PA ‘SOUTHEASTERN STATES Computer Hut, Hialeah, FL; Delta Electronics, Leesburg, FL; Dougles Computer Systems, Jacksonville, FL; Economy Computing Systems, Ortando, FL; Electronic ‘Shop tne., Melbourne, FL; Microcomputer Systems Inc., ‘Tampa, FL; Computer Systems Center, Atlanta, GA; ‘Computer Electronics, Baton Rouge, LA; Byte Shop, Columbia, SC MIDWESTERN STATES American Microprocessors, Prairie View, (L; Bits and Bytes, Posen, IL; lity bitty machine company, Evanston, {L; Lillipute Computer Mart, Skokie, 1L; Numbers Racket, Champaign, IL; Data Domain, Bloomington, IN; Home Computer Center, indianapolis, IN; Micro Bus tnc., Cedar Rapids, 1A; Data Domain, Louisville, KY; ‘Computer Mart, Royal Osk, Mi; Computer Systems, St. Clair Shores, Ml; General Computer, Troy, Ml; Computer Depot, Minneapolis, MN; Computer Room Inc., Eagan, MN; High Technology, Oklahoma City, OK; Milwaukee Computer Store, Milwaukee, WI WESTERN STATES Bhs & Bytes Computer Shop, Phoen!x, AZ; Personal Computer Piece, Mesa, AZ; Affordable Computer Store, Santa Clare, CA; A-VIDD Electronics, Long Beach, CA; Bits n Bytes, Fullerton, CA; Byte Shop, Burbank, CA; Fresno, CA; Lawndale, CA; Long Beach, CA; Palo Alto, GA; Pasadena, CA; Placentia, CA; San Diego, CA; San Jose, CA; Sen Rafael, CA; Santa Clara, CA; Tarzana, CA; ‘Thousand Oaks, CA; Walnut Creek, CA; Westminster, CA; Computer Center, Costa Mesa, CA; Computer Center, San Diego, cA; Computer Components, Van Nuys, CA; Computer Electronics, Santa Barbara, CA; Computer Emporium, Newport Beach, CA; Computer: land, San Leandro, CA; Computer Mart, Orange, CA; Computer Playground, Westminster, CA; Computer Power and Light, Studio City, CA; Computer Store of ‘San Francisco, San Francisco, CA; Dunston Enter. Prises, Redding, CA; Executive Office Equipment, Pasadena, CA; Micro Computers, Fountain Valley, CA; Microtystems Engineering, San Francisco, CA; Sunny Sounds, San Gabriel, CA; Sunshine Computer, Carson, CA; Upland Computer Labs, Upland, CA; Ximedia, ‘San Francisco, CA; Byte Shop, Boulder, CO; Engle ‘wood, CO; Mighty Mini Company, Denver, CO; Micro- computer Systems of Hewall, Honolulu, Hi; Small Computer Systems, Honolulu, Hi; Computer Mart of West Texas, Lubbock, TX; Computer Shop, San Antonio, ‘TX; Computer Terminal, E! Paso, TX; Electronic Specialty, Houston, TX; Houston Computer Mart, Houston, KA Electronic Seles, Dallas, TX; Micro Store, Richar ‘son, TX; Vanguard Systems, San Antonio, TX FOREIGN Microtech Computers, Winnepeg, Manitoba, Canada; Haywood Electronic Associates Lid, Northwood, Middlesex, England: instrumatic, Geneva, Switzerland. TOF G2APFIC INC. 790 HAMPSHIRE ROAD ® A + B WESTLAKE VILLAGE, CA 91361 Not Affiliated With Vector General Circle 204 on inquiry card. You Asked For It! You asked for the Intel 8080A CPU You asked for a real-time clock You asked for eight level vectored priority interrupts . You asked for a jump-on-reset and resident monitor You asked for the S-100 bus You asked for an 18 slot fully shielded motherboard . You asked for a rugged, reliable chassis . Then... You asked for the compactness and convenience of installing your mini-floppy disk directly in the front panel. ...... . NOW. We gave you the \Vecto21 We gave you the Vector We gave you the \Veczo2 1 We gave you the VEczo31 We gave you the Veco We gave you the VEcto31 We gave you the Veccor1 . We give you thNECCOR 1+ Hal Taylor Interactive Music Box 11 Arlington VA 22210 Photo 1: The author’s computer music system, which consists of an Altair 8800 computer with 32 K bytes of programmable and read only memory, and an ADM-III video terminal. Also pictured is @ Mini-Moog electronic music synthesizer (top left) and a Farfisa VIP 400 electronic organ (bottom SCORTOS: ~ Implementation of a Music Language Perhaps nowhere can technology better serve the creative end of the music arts than through the computer. The computer has a natural affinity for the application to music since it is capable of carrying out processes which create and perform music. It can be programmed to learn any language the com- poser wishes to use to describe his musical ideas. It can manipulate the symbols of that language to produce transformations of the composer's original ideas. It can enlarge and improve the quality of the composer's crea- tive output by allowing him to work in an interactive mode where he can hear his musical works performed within minutes of their conception. The computer owes this affinity to its unerring accuracy and high bandwidth, qual- ities which its human inventors do not possess. The human mind is slow and noisy and requires years of exercise to achieve the coordination necessary to perform complex 12 musical passages. Although the computer may never be able to match the expressive subtleties of a concert soloist, it is in some cases more suitable for the performance of music than a human being. If a program can be devised to convert musical symbols to the sounds they repre- sent, then the computer can be of value to the composer as a means of developing composition prototypes, that is, preliminary designs of musical works that he could hear performed before he copied the parts and gave them to the orchestra. An editing capability would also be available to him to alter the music until it produced the desired results. When the computer performed the work to his satisfaction, the original score and the instrumental parts could be pub- lished on a computer controlled plotter. With such a system the composer could avoid the drudgery of hand copying parts, and would be encouraged to experiment JADA GIGIGIE Q] [w] fe] Le] fed 4 CE) LEY Fe] Le of] (23) (22) [os] [as] (8) [5] LR] CE] LF) 2S] LA “AAR ARAL Figure 1: A standard alphanumeric keyboard modified for the SCORTOS language. SCORTOS Js a language dedicated solely to the processing of musical information. The keyboard is a stand- ard ASCH unit which has been relabeled with music symbols. The user enters a musical compo- sition by striking the keys which correspond to the symbols in the music score of the compos!- tion (see also photo 2). with new forms that he might otherwise hesitate to give to an orchestra. The computer can also be useful to the composer as an originator of musical ideas since it can simulate the process by which the human mind creates music. A music composition consists of a series of musical events chosen from a minimum of about 200 different possibilities (consider, just 12 tones and 18 types of notes}. Only certain of these combinations are pleasing to the human ear. The composer’s job is to discover those combinations which produce aesthetic results, The manner in which he or she does this is personal, intuitive, and cannot by itself form the basis for a workable algorithm. It is possible, however, to infer some of the underlying rules of music by analyzing it. Whether we are composing with our minds or with a computer, we follow a set of rules that determine which pitches will be chosen, in what order they will be arranged, and how long each will last in time. The set of rules describes the style and structure of the music and can be repre- sented in a computer by a statistical model. A process can be programmed into the computer that uses the model to decide which musical events are suitable for use in the composition. The process is one in which random choices are discarded according to a stochastic model. {According to Webster's, stochastic processes are processes based on the behavior of random variables. Random variables, in turn, are functions which are the result of statistical experiments in which each outcome has a fixed probability. For example, the number of spots showing if two dice are thrown is a random variable . . . CM/ In order to produce a musical event, the program generates a random number ret ee eee ‘7 Seana aaaasae which it associates with a variable such as pitch or time. The number is then subjected to the constraints of the model. The model is constructed by feeding specimens to an analysis program which are representative of the desired compositional style. The speci- mens are analyzed according to pitch, time and chord structure, and a_ probability matrix of n dimensions is generated, where n is the degree of order desired and represents the extent to which the analysis was carried out. As n increases, progressively more order is imposed upon the process, since more information is available to describe the 13 Photo 2: The modified ADM-IIf video terminal. The keytops on the ASCII keyboard have been modi- fied to enable the user to easily encode musical compositions, See figure 7, Introducing Apple II. You've just run out of excuses for not owning a personal computer. Clear the kitchen table. Bring cassette interface, so you can swap in the color TV. Plug in your new with other Apple II users. _ Apple II* and connect any standard You can create dazzling color cassette recorder/player. Now you're _ displays using the unique color a ready for an evening of discovery in Phics commands in Apple BASIC. the new world of personal computers. rite simple programs to display Only Apple II makes it that beautiful kaleidoscopic designs. Or easy. It’sa invent your own games. Games like complete, ready to use computer, not a kit. At $1298, it includes video gra- phics in 15 colors. It includes 8K bytes ROM and 4K bytes RAM—easily expandable to 48K bytes using 16K RAMs (see box). But you don’t even need to know a RAM froma ROM to use and enjoy Apple II. For example, it’s the first personal computer with a fast version of BASIC permanently stored in ROM. That means you can begin writing your own programs the first evening, even if you've had no previous conmputet experience. The familiar typewriter-style keyboard makes it easy to enter your instructions. And your programs can be stored on—and retrieved from— audio cassettes, using the built-in PONG —using the game paddles, supplied. You can even add the dimen- sion of sound through Apple II’s built-in speaker. But Apple II is more than an advanced, infinitely flexible game machine. Use it to teach your children arithmetic, or spellin; for instance. Apple makes learning fun. Apple II can also manage household finances, chart the stock market or index recipes, record collections, even control your home environment. Right now, we're finalizing a peripheral board that will slide into one of the eight available mother- board slots and enable you to compose music elec- tronically. And there will be other peripherals announced soon to allow your Apple II to talk with another Apple II, or to inter- face to a printer or teletype. pple II is designed to grow with you as your skill and experience with computers grows. It is the state of the art in personal computing today, and compatible upgrades and peri- phevals will keep Apple I] in the fore- nt for years to come. Write us today for our detailed brochure and order form. Or call us for the name and address of the Apple I dealer nearest you. (408) -1010. Apple Computer Inc., 20863 Stevens Creek Boulevard, Bldg. B3-C, Cupertino, ifornia 95014. Apple II™ is a completely self-contained computer system with BASIC in ROM, color graphics, ASCII keyboard, light- weight, efficient switching power supply and molded case. It is supplied with BASIC in ROM, up to 48K bytes of RAM, and with cassette tape, video and game I/O interfaces built-in. Also in- cluded are two game paddles and a demonstration cassette. SPECIFICATIONS * Microprocessor: 6502 (1 MHz). * Video Display: Memory mapped, 5 modes —all Software-selectable: + Text—40 characters/line, 24 lines upper case. + Color graphics—40h x 48v, 15 colors - High-resolution graphics—280h x 192v; black, white, violet, green (12K RAM minimum required) + Both graphics modes can be selected to include 4 lines of text at the bottom of the display area. + Completely transparent memory access. All color generation done digitally. * Memory: up to 48K bytes on-board RAM (4K supplied) + Uses either 4K or new 16K dynamic memory chips + Up to 12K ROM (8K supplied) * Software + Fast extended integer BASIC in ROM with color graphics commands Ate nionitor in ROM + 1500 bps cassette interface + 8-slot motherboard + Apple game I/O connector + ASCII keyboard port Apple Il is also available in board-only form for the do-it-yourself hobbyist. Has all of the features of the Apple II system, but does not include case, keyboard, power supply or game paddles. $598. PONG isa trademark of Atari Inc. “Apple II plugs into any standard TV using an inexpensive modulator (not supplied). @oppic computer inc: Circle 208 on inquiry card. COMPUTER 88-RCB HAMMOND. D2 ORGAN 88-RCB MooG 8B-RCB SYNTHESIZER ARP 88-RCB STRING ENSEMBLE 88-RCB ARP OMNI POLYPHONIC SYNTHESIZER 88-RCB Figure 2: A medium scale SCORTOS configuration. The 88-RCB units are relay boards which can be driven by the computer to operate organs, synthe- sizers or other similar instruments. Each board consists of two & bit data registers which can be loaded from the central processing unit. Each of these bits in turn drives a transistor which energizes a relay. One 88-RCB board can contro! 16 keys, or 11/4 octaves of a musical keyboard. The system can ad- dress (and therefore control) up to 256 keys. desired composition and less is left up to chance, Zeroth order stochastic control is no control at all, Random choices are used to build the composition without testing them against the model producing unlistenable music in most cases. In first order control, the transitions between pitches and rhythms are governed by the probability distribution of those transitions as they occurred in all the analyzed samples. Music produced in this manner still sounds amorphous, but will have fewer pitches that sound alien. It is not until we impose higher order contro] that a melody as we know it will take shape with its symmetrical phrases and regular intervals. In second order control, the selection of an event depends upon the 16 event that preceded it; in third order control the previous two notes, and so on. For example, if the previous note chosen was a B-flat and the random number gener- ator has just produced a C, the program refers to that location in the probability matrix which gives the probability of a C following a B-flat. If there is no probability of this happening, the C is rejected. If the probability is 1.00 then aC always follows a B-flat in this style of music, and the program will reject all random numbers that are not Cs. Of course the source of the information within the model need not be music speci- mens, as in this example, but may originate from mathematical functions, poetry or any one of a hundred other sources. It is this capability which makes the computer so intriguing as a composer’s tool. The Score to Sound System The Score to Sound System (SCORTOS) was developed to provide the composer with an inexpensive means of conducting com- puter implemented music research and composition prototype development. The system has the capability to perform conven- tional music scores by allowing music symbols to be entered through a terminal keyboard by an operator. Music of computer generated specifications can be performed through user program calls to a set of subroutines that interface the user program to the SCORTOS system software. Music is produced by the computer driv- ing relays that are wired in parallel to the keyboard switches of electronic music instruments — organs, synthesizers, etc. This allows a simple and inexpensive interface between the composer’s studio instruments and the computer. The limitation of this approach is in its inability to provide the computer with access to the timbre controls of the synthesizer, an encumbrance which may be tolerable to experimenters primarily interested in the musical variables of tonality and syntax. Also, there is a rich assortment of preset timbres available in commercial keyboard instruments, among them, the Orchestron which generates actual orchestral and choral sounds from a prerecorded opti- cal disk. The system consists of an Altair 8800 computer with 32K bytes of memory, an ADM-III video terminal, a mass storage device (either cassette or floppy disk), one or more International Data Systems 88-RCB relay control boards and any electronic key- board instruments the user wishes to con- nect to the 88-RCBs. The ADM-III has a standard ASCII key- Verbatim You want to record your message verbatim—word for whole s Si is quality. word—whether it's bits, bytes or “Dear Folks” trans- lated into word processor language. Our objective in manufacturing recording media for the electronics industry —digital tape cassettes, floppy disks, mag cards, computer cartridges—is to give you the finest, the best, the most dependable, the most cost-effective. That means rugged, long-lived, abrasion-resistant recording media with superior magnetic qualities. If we made tires, they'd be steel- belted radials. We delivered our first digital grade certified tape cassettes back in the beginning, 1969. We made the first commercial 3740-com- patible floppy disks that didn’t bear IBM's name. And the first Flippy® reversible flexible disks with anyone's name on them. The first mini data cassette is ours. And we've got the newest minia- ture flexible disk, the MD 525. Circle 206 on inquiry-eard, Now, Verbatim media. It's a new formulation of ferric oxides, an advanced macromolecular binder system to adhere it to the tough polyester film, and a proc- , es control system that demands over 200 separate quality checks before the material is cut, packaged, and certified to be 100% error-free. ‘The final quality check? “Make it pretty!” Our production people tell us that magnetic recording media is one of the rare instances in manufacturing where aesthetic appearance translates directly into final product quality. It has to look beautiful to work beautifully. ‘We have the formulas, the machines, the technology to make high quality recording media. But it takes the best people in the indus- try to deliver Verbatim disks, cards, cartridges and cassettes. You'll find them at your favorite retail computer store. Information Terminals Corp. I. Sunnyvale, California Photo 3: A close-up view of the component side of the 88-RCB 16 channel relay interface board which can drive a musical keyboard with — signals from the computer. board whose keytops have been relabeled with music symbols (see figure 1 and photo 2). The composer enters the composition into the computer by striking the key corresponding to each musical symbol as it appears in the score. This creates a music text file. The source text is passed to a language processor which maps each musical event represented in the source text into a physical 10 address plus a timing value, and writes this to a binary output file. The result is a list of records each of which defines which key of which instrument will be turned on and for how long. The binary output of the language processor is read by a driver program which uses the 1O addresses and timing values in each record to deter- mine what data is to be loaded into the data registers of the 88-RCBs, and at what time it is to be loaded. The keyboard instrument responds by playing the piece just as if someone were playing on its keyboard. In fact, the system can be thought of as an organist with 16 very flexible fingers, be- cause it is capable of performing 16 separate parts simultaneously, Keyboard Instrument to Computer Interface The 88-RCB is the interface between the computer and the electronic keyboard instruments. It was designed expressly for the SCORTOS system project, but is also useful for other low current switching appli- cations. The board has two 8 bit data registers which are “write only” accessible to the central processing unit (CPU) through 18 two output ports which are individually strappable to any address in the 8080 10 channel. The data register latches the con- tents of the CPU’s A register when an OUT instruction has been executed to that regis- ter’s output port address. The outputs of each bit of the data registers drive a transis- tor which in turn drives a board mounted DIP relay. The complement outputs of the data register latches are used to drive light emit- ting diodes (LEDs) which can be mounted on the board or on a front panel to monitor the status of each relay. The relays are wired in parallel to the keyboard switches of the electronic music instruments which elec- trically isolate the peripherals from the computer and ensure plug-to-plug compati- bility among most keyboard instruments. Each 88-RCB controls 16 keys, or 11/4 octaves of keyboard. To ensure an adequate tonal range, two 88-RCBs may be configured ‘on any instrument (see figure 2). The maximum number of keys the sys- tem can address is 256. In arriving at a figure of maximum connectivity, it was necessary to balance programming considerations against what was thought to be an adequate number of system-controllable sound pro- ducing peripherals. 256 keys are equal to about 20 octaves of keyboard (three full piano keyboards) which may be distributed among ten sound-producing peripherals, giv- ing each instrument a 2 octave range. This maximum configuration seems adequate to provide for the largest studio application. Pee trseririits 3 It’s like adding a room to your brain! The System 8813 from PolyMorphic Systems is a complete, powerful problem solver in a single walnut cabinet. This machine allows you to perform complex financial, engineer- ing, and scientific models in the comfort of your office or den. The high speed video display presents your results in text, tables and graphics. The detachable typewriter-like keyboard permits relaxed program entry and operation. Convenient mini-discs store programs and data for compact filing, secure storage, and fast access. Our disc BASIC programming !an- guage is simple enough for the computer newcomer, yet powerful enough to amaze the most advanced users. The whole family can immediately use and enjoy pre- programmed applications and educational packages. Let the System 8813 become your trusted business, profession, and personal tool. The PolyMorphic Disc System is acompletely assembled and tested unit with brushed aluminum front panel, walnut cover, detachable keyboard, video monitor, 16K RAM. Includes system software and fully extended BASIC on disc. Delivery 60 days ARO. Upgrade packages for POLY 88 owners will also be available. Prices and specifications subject to change without notice. Pyyerents (805) 967-0468 460 Ward Drive, Santa Barbara, CA 93111 SCORTOS SCORTOS Music Symbol! Description Code Music Symbol Description Code ° whole note x1 t quarter rest 4 d half note x2 , eighth rest 8 J quarter note x4 7 sixteenth rest 16 d eighth note xs 7 thirty-second rest 32 4 sixteenth note X16 I left hand repeat t 5) thirty-second note x32 1 right hand repeat 1 ~- whole rest 1 = bar / - half rest 2 TD triplets 3(XnXnXn) Music Symbol Description SCORTOS Code c Pitch representations c Dd D Table 1: The alphanumeric é music coding convention 5 used by the SCORTOS F F system. The X symbol G G preceding each numeric SCORTOS code symbo/ A A indicates that the numeric B B symbol must be preceded by a pitch representation a sharp + before it can be recognized 4 natural N as a note. For example, C2 would be a half note . fist - with pitch C. J J) slur A . dot A simple method of representing key- board address was chosen to minimize the execution time of the DRIVER program. One byte is used to represent the keyboard address (pitch), and one byte contains the length of time the event will last (rhythm). Since a music piece consists of so many events, the size of the data record is critical. It affects the total performance of the system by limiting the length of any per- formance to the number of event records that will fit in available memory. For this reason, it is not practical to increase the size of the event data record to accommodate a connectivity greater than 256. The Alphanumeric Representation of Music The conventional music score format is not the most perfect method for entering music into computers. The music symbols Must be somehow transformed into a code the computer understands. In the conven- tional method, the operator enters data from a music score into an alphanumeric key- board. This method has two disadvantages: it often requires multiple alphanumeric symbols to define one musical event (one character for pitch, one character for rhythm, one character for dynamics). The second disadvantage is that the choice of alphanumeric symbols must relate in some way to the quality of the musical symbols they represent, which in the past has meant that the symbols were scattered about the keyboard with no regard to their qualitative value. As a result, the data entry process was a hunt and peck procedure which may have been too discouraging for all but the most enthusiastic. The human to computer interface should provide maximum ease in data entry and data editing. There are four ways to accom- plish this: © Choose a set of alphanumeric symbols to represent the set of musical symbols that will enable music passages to be j— tr Oboe ~ = = Aes FF POl K2- T3/4 (2.)03 "The dotted half rest is to be repeated three times" 4) Ts 2 Flutes f—- 7 2 j—# t ZZ ro t —= 7 f P02 K2- T3/4 03 F4 G4 A8. F16 / 04 C8. CB B16 O2 F4 B4/ D8. E16 F4. GE/ FEDCOSBO2C/ P03 K2- 13/4 03 F2,A\/ F4 F2\/ F24/ F2.A/ F2 4/ A = = —— Violin 5 C3 # z ¥ CS P04 K2- 13/4 2. /2./4 4 F&/A/ F2. / E = — yy: Cello [ES ,—t { ° yo ee POS K2- 13/4 2. 2 /4 8 O2 Ev16 FA/ F2, / Figure 3: A fragment of an orchestral score annotated in SCORTOS code (see listing 1). best recognized in alphanumeric form. System Software © Elimi ies ii F Alaina all stedundanetes; «im the The SCORTOS System Software consists © Position the alphanumeric symbols on of 2 soe i piouams auton tn a be the keyboard logically in the order of sior finer ee thes Meee their musical value and group them by s y . type. ® entry and manipulation of the sym- © Generate bar markings and bar num- bolic music text. bers automatically during data entry. © conversion of the text to binary data. ; ‘ z soe Table 1 shows the alphanumeric symbols sone st) OF evens alates by user used to represent conventional music nota- « D arson of me bina data to tion in the Score to Sound System. Note riuéle, Y that each alphanumeric symbol alludes to . the quality of the music symbol it repre- The interaction of these programs with each sents. A musical event can be defined by one other is shown in figure 4. or two symbols, depending upon whether The monitor allows the user to control the event is a rest or a note. A numeric the system’s major functions. It recognizes symbol which is not preceded by a letter three command verbs with one or more character is recognized as a rest. Notes arguments per verb. Each verb calls a system always occur as a pair of symbols, that is, a module, and its arguments specify the data letter character followed by a numeric file which is to be operated upon by that symbol. Figure 3 illustrates a portion of an module. Table 3 is a list of command verbs actual orchestral score along with its corre- recognized by the monitor. sponding SCORTOS code. The editor allows the user to enter music Since the characters generated by the text through the terminal keyboard and SCORTOS keyboard hardware do not corre- provides a means by which it may be easily spond to those desired to represent the manipulated. music symbols, the data entry software As text is entered through the keyboard, echoes back the desired character with the the editor’s data entry processor keeps a terminal in full duplex mode. running count of the bar number and auto- Continued on page 206 ral equals three computers. Todo real work with any computer. big or small. it takes a complete system. That's one of the nice things about the Sol-20. 1 was built from the ground-up as the heart of three fixed price computer systems with all the peripheral gear anc software included to get you up and on the air Sol System 1 costs just $1649 in kit form or $2129 fully burned in and tested. Here's what you get: a Sol-20 with the SOLOS personality module for stand alone computer power. an 8192 word memory, a 12" TV video monitor a cassette recorder with BASIC software tape and all necessary cables. Sol System TH has the same equipment plus a larger The functional beauty of Sol Computer Systems is More than skin deep. A look inside reveals a simple elegance af design and sturdy construction, al computer systems, they have more " power per dollar than anything ever offered. They provide performance com- parable with mini-computer systems priced thousands of dollars more. The Small Computer Catalog for the rest of the real computer system story. Visit your local computer store for acopy of our fully illustrated 22 page cata- log. Or you may write or call us if more convenient. Please address Processor Technology. Box B. 6200 Hollis Street. Emeryville, CA 94608. (415) 652-8080. [W)eatnciesy See Sol here... 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IN 46250 FIER cane, a Byte Shop Computer Store (213) 843-3633 . Columbus, OH 43227 ue The Byte Shop Bellevue, WA By's tog computer sore Zee Noun Mains. TBSN ema ag (614) ZB! co taeal Citrus Heights, CA 5810 {tig} gagessa °° Indianapolis, IN 46268 SOmPuter Mart of Daylon The Retail Computer Store (916) 961-2983 Byte Shop (317) 251-3139 Dayton, Of 45409 MONE. 72nd 9 rattle, Wi 18 Computer Center 44300 Beach Blvd. nenrucny (513) 296-1248 (206) S2e-e101| {ots Harbor Blvd. Westminster, CAs26a3 KENTUCKY i x e Dal i (ria) 646-0821 CIN SEBS S02sHunsingertane OREGON, wisconsin Data Consultants, Inc. COLORADO Foulevile, Ky s0a20 3480 SW Cedar fils Blvd, Madison Computer Store 2350 W. Shaw, Suite 114 (502) 456-5242 Besvorlon OF 37066” 1910 Monroe St. Fresno, CA 93711 Byte Shop (503) 644.2686 Madison, WI 3711 (209) 431-6461 Boe co eae MICHIGAN The Real 0. (608) 255-5552 Bits 'N Bytes (303) 449-6233 The Computer Store Commerce The Milwaukee 679 S. 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Center St. of San Francisco (201) Kingsport, TN 37664 1093 Mission Street 1 545'8081 San Francisco, CA 94103 t( (415) 431-0640 Circle 207 on inquiry card. [WESESes, Alphanumeric Music by Melanie Jubb, 188 S 14th St, San Jose CA 95112 Melanie Jubb’s oil painting celebrates the idea of computers and music, emphasizing this issues’s artistic themes.™ 26 Photo 1: The author's new dress for KIM is shown in this shot taken with the briefcase opened. The un- used area of the power supply cover is used to ad- vantage as a place to mount prototyping boards for use in 10 contexts with KIM. R Travis Atkins 6? Greenend Av Middletown RI 02840 At first | was reluctant to take KIM out in public because she was so small and home- ly compared to other systems her age. No ‘one actually ever laughed at her in my pre- sence, but I could sense the pity that they had for me. | wondered, would my KIM forever be overshadowed by those bristling brutish Altairs and IMSAls at every social gathering? | knew KIM’s strengths and her weaknesses, and | wondered if there was anything that | could do to help her find acceptance in the world. Then, one evening, while talking to a friend whose IMSAI was drawing considerable attention, as usual, it occurred to me that it wasn’t his central processing unit’s IQ that set it apart from my humble KIM. No, it was the way that it was dressed that did so much toward creat- ‘SWING OPEN DOOR Figure 1: The assembly which was inserted into the briefcase has two sections at different levels as shown in this view. The section at the left covers a built- in power supply for the system. The lower section on the right faces two edge connectors (B) for the KIM-1 card. A single pop rivet hinge (A) allows a door to the power supply section to open. This allows the power supply card to slide out on the appropriate card guides (C). The power cord and other externals plug into the top of the chassis (E), which has enough area to accommodate prototyping cards as seen in photo 1. The height of the power supply section (D) is chosen based on the size of the briefcase. A New Dress for KIM (A Brief Case History) ing the image of great sophistication and power. | resolved that very evening to give my KIM the same advantages that her peers had; after all, who wants to be accused of neglect- ing loved ones? If she was to be oco'd and aaah’d over, then she’d have to be dressed up before | took her out again. Although | must say honestly that | doub- ted that her 8.5 by 11 by 5/16ths dimen- sions would ever win her a spot on the centerfold of BYTE. | suspect that there are many other KIM owners around who have also wondered how to dress up their bare-bones KIM board to take them out to club meetings and such, so here’s the way that | did it. | hope it gives you some good ideas for your own KIM-1, First of all, | had two major constraints to deal with: namely, my budget and my own skill, or rather lack of skill in the field of beautifully sculptured fiberglass and metal enclosures and the like. So | knew that | would have to settle for a simple and cheap approach to this thing. One thing that the KIM had going for it was its small size, because that meant that it could be placed inside a reasonably sized package. But, what was a reasonably sized package? And, where could | get one cheap? A shoe box?. . .no, that’s too big. Hey, how about that old briefcase in the back of my closet?. . .not a bad idea! Much to my surprise and pleasure | discovered that those sneaky designers at MOS Technology must have been anticipa- ting my train of thought, because when opened that old briefcase and dropped the KIM in, it was a perfect fit! Great, now I knew what my enclosure was going to be, so the next question was how to support it inside the briefcase. Again, two con- straints: first of all, protection for the printed circuit board itself, and secondly, reasonable looks. The briefcase’s exterior would provide some rough handling protection for the KIM, but it would also need some solid support from the bottom; therefore, since the bottom of my briefcase was not flat, | would have to construct a flat platform for the KIM. As for the basic appearance, | really wasn’t too crazy about an open frame power supply, nor would that be an awfully safe setup. So, | decided that the power supply would have to be placed inside a special enclosure, away from stray fingers. The chassis design, shown in figure 1, was the result of considerable study. Some of the more notable yet less ob- vious features of this design are: ® A swing open door to provide ac- cess to the power supply compart- ment (pop rivet hinge). @ The 44 pin edge connectors (one of which is provided with the KIM-1) penetrate the chassis wall to give solid support and to protect the loose wires. ®@ PC board edge guides to hold the power supply and other auxiliary components on a removable card. ®@ An overall height selected to suit the briefcase depth (mine filled the lower half). @ Placement of the power cord, swit- ches, and other auxiliary parts on the top surface of the power supply compartment to facilitate easy re- moval of the entire assembly for bench work or to change to a new briefcase. @ A large surface to place connectors, etc. @ A Plexiglas cover sheet to further protect the KIM-1 board and filter the LED displays may also be added. @ Use of the upper half of the brief- case to carry documentation, etc. The KIM-1 board is recessed in this de- sign, but it is not hard to get to the key- board for programming it, although this was one thing that | thought might give me trouble at first. Being recessed does give the KIM an added amount of protection, and | have found that the recess over the board is a great place to carry my KIM-1 owner’s of the pins of the A connector, and selected pins of the E connector of my KIM board. 1 use this to patch into a smail prototype board which | also placed on that surface, and | must say this has proven to be a most useful setup. Of course, you will probably want to provide jacks for your audio cassette unit, and maybe one for a Teletype if you’re fortunate enough to have access to one. At any rate, my little KIM is no longer the club wallflower, and as | look into her future | see a handsome genuine calfskin briefcase waiting. U2in, gi? em.) Win. —e, (3em) (3.8cm.) +— lin. (2.5¢m.) ¥ +— 1.510 (3.8¢m.) 'e— Bin. (20.3¢m) 8.5 in, (21.6cm.) Vin, (1.3em) (.3.em.) 15in. (3.8em.) SURFACE OVER THE POWER SUPPLY Un. (2.5¢m.) 35/800 23/400 35/810 ig 2em) rem) 9 2am) ° f 5/1610 1610 (Bem) (2em) SURFACE UNDER KIM-1 manual. That spares me from having to ex- plain what in the world | have in my brief- case every time | open it in public. The auxiliary area on top of the power supply compartment is the place where you can customize your chassis to suit your own particular needs. On my chassis | put a surp- lus 50 pin connector which is wired to most Figure 2: The mechanical design of the chassis box is shown in this illus- tration. The depths of the two sections are dimensioned to fit the author’s briefcase. This can be fabricated out of a piece of aluminum stock 1/6 of an inch thick and measuring 20.5 by 15.5 inches (or, in integral metric dimensions, 2 mm thick measuring 52 by 39 cm). The drawings show dimen- sions for the actual KIM-1 connector holes with metric dimensions in paren- theses. The housing was cut, milled (the pin edge connector holes) and con- structed at a local machine shop for under $15. 27 p : damon) & Interlace boards—shown MPU-A, 88K d , line printer and serial 1/0's, POS-80 Sysiem—sampie component configurations. Microcomputers: Just Ask If you wonder who leads the way in technology, look into IMSAI’s list of industry firsts—IMSAI 8048. first complete control computer on a board: IMSAI 65K. RAM Board. first to offer four times the memory capacity previously available on one board: IMSAI printers. first with high- speed direct memory access. If you wonder why IMSAI products have gained the reputation for the standard of excellence in microcomputer systems. check with any one of the more than 10.000 IMSAI owners. If you wonder who offers the broadest line of hardware, software, and peri herals. visit any one of the more than 275 IMSAI dealers around the world. If you wonder how microcomputing can fit Your specific needs. ask IMSAI. Because when il comes to microcomputers. we have the answers. AnIMSAI Product to Answer Every Microcomputing Need: Let's start with our product line. In all, IMSAI offers more than 120 high quality. completely integrated systems. components, peripherals and sofiware. Here's just a sampling: Single Board Central Processors: + MPU-A (8080 based)—Industry standard. + MPU-B (8085 based)—50% faster 8080. + 8048-—-Programmable control computer. Interfaces: + Video 1/O—24x80 CRT. Edit & data entry. * Serial 1/0—2 port [/O. all std. protocols. + Purallet 1/O—4 & 6 port TTL level 1/0, + Multiple 1/O—2 cassette, 2 parallel. I serial & I control 1/0, + DMA-For floppies & line printers. Peripherals: + Printers—40/80/ 132 col. 30 cps-300 Ipm. + Video displays—Large assortment. + Tape Drive—9 track. 800 bpi. 25 ips. + Floppy Disks—Single/double density. Memory Expansion Boards: + 4K RAM—Programmable memory rotect. + 16/32/65K RAM- 16K paging option for virtual memory addressing. * Intelligent Memory Mngr.—Handles up ta | megabyte. Self-Contained Systems: + VDP-80—Computer/terminal/mass storage uni. Assembled & tested. + PCS-80—Integrated component system. Software: + DOS—Enhanced CP/M. + BASIC—Interactive or compiler with scientific and/or commercial features. + FORTRAN IV—Level 2 ANSI compiler. + Self-contained Systems: SCS | & 2/TCOS—Assembler/line editor/debugger. 4 & 8K BASIC—Optional cassette support. Compare IMSAI. You'll realize that ours is the most complete product line available. Whatever your needs. you can get them from one source. IMSAI. A wide selection of components is only the pepening.. IMSAI offers much more. Just ask, Answers For Businessmen: Announcing IMSAI's VDP-80. This totally self-contained unit includes a mega- byte of disk memory via hoppy disk, 321 computer memory (expandable to 256K). 12" CRT and 62 pad main keyboard with 10 pad numeric keyboard. Several printer options available. Ifyou want speed and accuracy in high volume work such as word processing. or business data collection and analysis. the VDP-80 is your cost effective answer. Answers For The Personal User & Educators: Introducing IMSAI's new PCS-80 System. the fully integrated microcomputer component system. configurable to your exact needs. The basic system consists of our Intelligent Keyboard and the PCS-80 which houses an 8085 based CPU. 16K of RAM. intelligent ROM monitor. serial 1/O port. 24x80 CRT. with an extra 7 slots in the chassis for expansion. System component options include single or dual mini and standard floppy disks, The choice is yours. configure the system as you like. IMSAT has answers for the educator, too, Take the basic PCS-80. add 8K of PROM. 4K of RAM and our self-contained 8K BASIC software. and you have a complete operating system your entire department can use to teach anything from elementary programming to advanced computer Science. Require a bit less sophistication? Use our Intelligent Breadboard system for learning, designing and building micro- computer assemblies. Rather do it from scratch? Start with our single board MPU-B central processor, the heart of the PCS-80 Svstem. It has a IK ROM monitor, 256 bytes of RAM and serial and parallel 1/0. Since the MPU-B is 8085 based. you can run all programs previously developed for the 8080. 50% faster, Without requiring faster memory. IMSAI. Answers For Industry: IMSAI products provide the expandability and flexibility manu- facturers demand for microcomputing applications. We offer rack mountable components for the standard 19” RETMA racks, powerful MPU boards. I/O and memory boards for easy system expansion and configuration. and a broad line of peripherals and subsystems fully integrated and ready to go to work, IMSAI has what you need to make tomorrow's design today’s reality. Answers For Current IMSAI Users: There are over 10,000 of you. And. we haven't forgotten. You might say that we thought of you before you even thought of us. That's why every new product is designed to accommodate expansion. rather than outdate equipment. For example, our new PCS-80 retro- fit kit comes complete with MPU-B, replacement front panel photomask and additional hardware bracketing. So you can enjoy a single cabinet PCS-80 computer. with your choice of integrated component configurations. The Answer For Everyone: Dial (415) 483-2093. Ext. ACT. That’s IMSAI's action hotline. Designed to answer the thousands of questions we didn’t have a chance to answer in the space of this ad. Call us. We'll assist you in putting together a system, direct you to your nearest SAI dealer. and send you our new catalog with all the details. In short, if you have any questions at all regarding microcomputers. put us to the test, Just ask IMSAI. IMISAT The Standard of Excellence in Microcomputer Systems. IMSAI Manufacturing Corporation 14860 Wicks Bivd., Dept. B-9 San Leandro, CA 94577 (415) 483-2093 TWX 910-366-7287 Feaures and specifications subject wo change without notice. Circle 205 on inquiry card. Control the World! Photo 7: The author's prototype for the 4 chan- nel self-refreshing digital to analog converter shown in figure 9, Also contained on the board is a proto- type 4 channel analog to digital converter circuit. Steve Ciarcia POB 582 Glastonbury CT 06033 (Or at Least a Few Analog Points) “Kachunk! OK, get the reading quick! Ka-chunk! Pop! Pop! Bang!! The darn thing crapped out again! We'll never get one of these detectors to pass a life test." The burly mechanic puffed his fat cigar and with a disgusted sigh continued, “The dime store engineers who design these kludges should be the ones who have to test them! That’s if you could ever get them out of that puzzle factory upstairs!" That was my cue. | was indeed an engi- neer descended from the puzzle factory and my mission was to discover why we were 30 having so much trouble life test qualifying one of the pressure detectors we intended for future manufacture. Hearing the pre- ceding commentary as | approached the testing fab, | decided that an authoritative professional type would not be very popular at the moment, so | went into my innocent nonmanagerial mode and entered the lab, This lab was not unlike any other small production qualification and testing lab. It had the usual machinery and instrumenta- tion and many artifacts of former test pro- grams lying about. The most prominent as IS YOUR DOLLAR BUYING AS MUCH POWER & FLEXIBILITY AS TDL’S XITAN SYSTEMS PROVIDE? the best CPU board I've pul togethe wed right off without trouble shooting. at parts OUR CUSTOMERS SAY IR ee THINGS LIKE THIS ———* ae product’ AMM, ABOUT TDL PRODUCTS: Bella Vista, Ach. “... high quality components, goud engineering & complete dovumentation ... up and running without any problems.” |. DW Santa Magia, Cali. Kl ston, Mays. wtacellent.” ee “Very impressed) with superb quality.” - s — — When we combined aur highly praised ZPU board and our System Monitor Board, we defined the standard for the industry; we integrated more power and flexibility in two slots of our motherboard than mast other systems Can muster using five oF more boards, When we put this setup into our rugged aluminum case we Created the first XITAN system, the alpha 1. alpha 1 By adding a CRT terminal andior teleprinter you will have a complete computer system. Pp KIT: $769 ASSEMBLED & TESTED: $1039 By adding a 716 memory module and our PACKAGE A software to the alpha 1 we created a J second XITAN system, the alpha 2. Thus, a complete and extremely powerful micro-computer system emerges well worthy of you who are operating af the must sophisticated levels. The XITAN alpha 2 provides you with IBK of RAM, 2K of ROM, 2 serial /O ports, # parallel VO port, our 1200 baud audio casyette interface as well as our extraordinarily powerful software package which includes BK Basic, the Text Output Processor, the Zapple Text Editor and the alpha 2 Relocating Macro-Assembler. Add your own VO device and GO, ..with the most pewerful and flexible micto-computer package ever offered. KIT: $1369 ASSEMBLED & TESTED: $1749 IF YOU ARE A BEGINNER, YOU WON'T EASILY OUTGROW THE XITAN SYSTEM. if YOU ARE AN ADVANCED USER, YOU WILL DISCOVER XITAN IS EXACTLY WHAT YOU NEED. Crete 209 on inquiry ecard. tWrite for descriptive brochure on the XITAN alpha series TECHNICAL and system software. When you ask at your dealer, say “7Y-TAN.” DESIGN LABS JM PARK BLOG M1101 STATE ROAD ON, NEW JERSEY 08540 (609) 821-321 SS ORDERING INFORMATION: Send check, 0 order o BankAmericard, Master Charge Current number and expiration date. Shipping is usually made via UPS or UPS Bive Label. Specify other arrangements if you wish. Prepaid arders are shipped postpaid, I artifact was the leader of the instrumenta- tion group, Ned. Ned's large frame amply filled the white lab coat though it was barely discernable in the dense cloud of cigar smoke. The combined scent of hydraulic oil, burned resistors, and cigar smoke con- vinced me that today was not going to be my day. “Hi, Ned. What's the problem with the new detector?", | asked. “It’s about time one of you guys came down and asked. This has got to be the most fragile pressure detector | have ever tested. 5,000 PSt pressure [__, VALVE A REGULATOR $000 psig t 1 ~ | _ PRESSURE DETECTOR tad N UNDER TEST VALVE B 10,000 PSIG 1b ATMOSPHERIC PRESSURE VALVE'C 0 PSIG mi 19,000 — PSIS PUMP N RESERVOIR ACTION OF on VALVE & or =U UI LL ACTION OF on VALVE B OFF im M1 PL ACTION OF ON VALVE oFF im SI ~ RESULTANT 10K PRESSURE AT PRESSURE 5k DETECTOR (Psi) ° 2secs—-{| }+—s secs——+| Figure 1: Configuration of a conventional impulse pressure calibration test setup. Note that the pressure detector under test receives what amounts to a square wave input. This type of violent pressure change can shorten the life of the detector and give a false indication of its long term life expectancy. PSIG, or "gauge pressure,” is explained in the text. 32 So far, we have wiped out four engineering prototypes and, haven’t gotten to 20,000 pressure cycles, let alone the 50,000 life test,” he bellowed, My eyes rolled slightly as he mentioned the failed units. These pressure detectors were not in the least bit fragile; they were ruggedized units with a prospective sale price of $4700 each. The four engineering proto- types were handmade and far more costly. Before it became too apparent that | was coming to a slow burn, | asked the obvious question. “Ned, are you following the en- gineering test specification?” "You guys are really something! I've been in this business for 30 years. | was testing...” “OK, OK, Ned! Just tell me what your test procedure is. Pretend I'm a novice and tell me by the numbers.”’ | was sure that he felt that was the way he had to work with any engineer, so | humored him and just listened. “AIL right. The pressure detector is rated at 7500 PSIG and we are life testing it,” he said with a cigar chomping smile. ‘The pressure is cycled between 0 pounds per square inch gauge (PSIG) and 10,000 PSIG every ten seconds and remains at 5,000 PSIG between cycles. /PS/G, or gauge pressure, is a differential pressure measurement using the ambient pressure as a reference, Usually, standard sea level pressure (14.7 pounds per Square inch) is used as the reference... .CM] At the conclusion of each cycle, the detector reading is compared to an out-of-tolerance spec. Oven temp and other contro! param- eters are constantly monitored. Every 10,000 cycles, a calibration run is taken and compared to the accuracy specification quoted. We just haven't been able to get one of the bloody things to hang together long enough to finish the test. The pressure diaphragm keeps breaking.” So far, what he was relaying was exactly the procedure | had outlined. Nothing sounded wrong, so the next obvious question was a description of the test apparatus. “| decided to automate the testing pro- cedure,” he gleamed like a kid describing a new toy. ‘I made a sequencing circuit with relays to cycle the pressure automatically. All the operator does is record the data and run the calibrations. Here, let me draw you a diagram.” It was unbelievable! True, Ned was fol- lowing the spec, but what a way to do it! Pressure transducers are expected to with- stand a certain amount of overpressuring, which was the reason for the test. But over- pressure in combination with a 10,000 PSIG The most cost effective products for your microcomputer. THE EXTENSYS Pe RM64 MEMORY "Tike BOARD provides * eee the most cost o effective system memory found in the industry. The RM64 provides this because of our low cost per byte when compared to our competition plus the increased reliability of a single board over multiple boards containing less memory. The board is S-100 bus compatible making it usable in over a dozen different microcomputer systems including ALTAIR and IMSAI. The RM64 is available in three configurations: 32K, 48K or 64K bytes of memory all on ONE board. The board is completely assembled, checked out and burned in for at least 50 hours prior to shipment. This complete testing procedure allows Extensys to provide a one year warranty on parts, labor and materials {assuming no misuse of the board occurs). On board hardware is provided for: + Individual memory bank address selection in 8K byte increments; a t Complete dynamic refresh logic without loss of processing efficiency while programs are running; + Board select logic which allows more than one 64K byte board per system; + §-100 bus compatibility including on-board voltage regulator; » Memory overlap which allows memory sharing the same address Space to coexist in the same system; _—_ pr Frere an f be ual Write pro- —— tection in , 16K blocks; and 7: Res + Fully socketed for 64K, fi), allowing 32K and 48K versions J to be upgraded at a later date. Delivery of the RM64 is 15 to 30 DAYS upon receipt of order. Prices for the RM64 include shipping and handling prepaid in the continental United States. EXTENSYS Corporation is also announcing several other new highly cost effective products. These include a total floppy disk system based around File 1/O board and a multiprocessor operating system, The other product, which interfaces with the RM64 memory board to create a megabyte or more of memory and adds full DMA capability to the File |/O board, is a Board Select/DMA board. Both of these products are S-100 compatible. Circle 210 on inquiry card. Contact your local computer store ats or order directly from EXTENSYS foooc ooo Please place my order forthe foflowing: ary IESCRIFTION AMOUNT —— —_RMB4.IZK byte bows @ S = _AMEL-4BK byte board @ $1195 on, T= AMGL-64K byte board © $1405 on 3 | 592 Weddell Drive I —— Sunnyvale, California 94086 1 ___. (408) 734-1525 i] l 1 I I TOTAL —— Din nt ss coin Ua os 1 1 : 1 - Phease check method of payment: i} tnconed name | press 1 ‘ITY, STATE, ze SIGNATURE: I PHONEINELUDE AREACODE) 1! impulse was like a jackhammer. The engi- neering group upstairs would be amazed that the test made it though 20,000 cycles. | wiped my brow, leaned against the concrete wall and asked with a pathetic whimper, “I suppose the failed detectors make good boat anchors.”” “What?", he asked, not having heard what | had said. “Ned, while | think your intention is fine, your method may be a little too rough on the unit. Why don't we change the square wave pressure being applied to the detector to a sinusoidal waveform.” This was the method | had assumed he was going to use initially. “| can’t have a guy sitting there cranking @ pressure controfler knob ten hours a day. It's going to take two weeks to run this test as it is. That's why | automated it!” He seemed to get mad as | challenged his inventiveness. “You don’t have to compromise any- thing. Get a DC proportional control valve from the stock room and modulate the pressure sinusoidially. In fact, you can use the minicomputer which you ordinarily use for mathematical calculations over there PRESSURE VIN FROM D/A fOLT: DETECTOR Controues [727° *SvOLTS UNDER Test SarseuRe REGULATOR 10,000 PSIG. O TO 10,000 PSIG T | I | 4 10,000 0 PSIG Psie PUMP RESERVOIR LJ COMPUTER APPLIED RESULTANT PRESSURE (PSIG) «—\ i - 5K 1 ay Figure 2: The same pressure detector as in figure 7 being tested here with a computer controlled system which applies the test pressure sinusoidally. This approach gives @ much better indication of the unit's true life ex- pectancy, and incidentally shows one practical application of digital to analog conversion. in the corner to drive it directly, collect the data, and run the calibration automatically.” “You guys upstairs must be suffering from thin air. | know about computers; ones and zeros and all that stuff. We’re talking about a DC voltage controlled valve. That isn't consistent with computer binary voltage levels. You would have exactly the same on and off situation as my relay con- troller,” he stated. It was going to be an uphill fight, but 1 knew | was going Lo have to introduce Ned to the world of analog to digital and digital to analog conversion. | first mapped out the fife test circuit and diagrammed the wave- forms. Ned was no neophyte. He felt that he knew a lot about computers and in fact was quite familiar with the uses of BASIC and FORTRAN on the lab minicomputer, But Ned had never considered that this num- ber crunching machine has the same logical abilitics to control analog devices if properly interfaced. General Considerations While this may have been a lengthy intro- duction lo computer analog interfacing, it often takes a real life situation to make one realize the added potential of the computer when itis combined with analog capabilities. Since natural parameters such as dis- placement, temperature, volume and mag- netic field strength are analog, and most practical methods of data acquisition, man- ipulation and visual presentation are digital, conversion between analog and digital qualitics is a fundamental operation in computing and control systems. The basic building blocks are the digital to analog converter (DAC), and the analog to digital converter (ADC). Because these converters are essentially interface devices, the basic conversion circuitry must be adapted to properly mate the application to the computer, Such variables include the possible necessity for buffers, registers, clock circuitry and refer- ence voltages, all of which are external sup- ports for the actual conversion device. The exact design requirements can be lengthy and are handled separately by necessity. Digital to analog conversion is the first topic to be discussed, Digital to Analog Conversion The digital to analog converter can be thought ol as a digitally controlled program: mable potentiometer which produces an analog output. This output value (Vg) is the product of a digital signal (D) and an Why you should buy a digital multimeter from the leader in digital multimeters. Ifyou’re shopping for your first multi- meter, or moving up to digital from analog, there are a few things you should know. First, look at more than price. You'll find, for instance, that the new Fluke 8020A DMM offers features you won’t find on other DMMs at any price. And it’s only $169* Second, quality pays. Fluke is recog- nized as the leading maker of multi- meters (among other things) with a 30-year heritage of quality, excellence and value that pays off for you in the 8020A. Third, don’t under-buy. You may think that a precision 3%4-digit digital multi- meter is too much instrument for you right now. 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Or, we'll tell you the location of the closest Fluke office or distributor for a per- sonal hands-on feel for the best DMM value going. *U.S. price only Fluke 8020A DMM for Home Electronics Experts: $169 FLUKE Girele 211 on inquiry card. RE wingay 11 BINARY ‘re b—» v our CVREF | -VREF | -VREF | -VREF wours=(—"F aR aR ae) RF Figure 3: A 4 bit weighted resistor digital to analog converter. A 4 bit word is used to control four single-pole single-throw switches. Each of these switches és in series with a resistor. The resistor values are related as powers of 2, as shown. The other sides of the switches are connected together at the sum- ming point of an operational amplifier, Currents with magnitudes inversely proportional to the resistors are generated when the switches are closed. They are summed by the op amp and converted to a corresponding voltage. V REF tle MSP a swi analog reference (V,o¢) and is related by the following equation: Vo = (D) (Vree) To a large extent, no digital to analog or analog to digital converter can be of much practical use to anyone without spccifying the type of code utilized to represent digital magnitude. Converters work with cither unipolar or bipolar digital codes. Unipolar includes straight binary and binary coded decimal (BCD). Even floating point converters have been used on occasion: witness the auto ranging digital voltmeter. Offset binary, ‘one’s and two’s complement and Gray code are usually reserved for bipolar operation. Since the obvious sphere of this article is home computer applications, straight and 2R vour Figure 4: A 4 bit “R —2R" ladder network digital to analog converter. This iype of digital to analog con verter makes use of a resistor ladder network constructed with resistors of values R and 2R. The topology of this network is such that current flowing into any branch of a 3 branch node will divide itself equally through the two remaining branches. Because of this,