Historical Document · 1975
Electronics Today International, July 1975
The British magazine Electronics Today International for July 1975, with coverage of Sinclair's calculators.
Historical Document · 1975
The British magazine Electronics Today International for July 1975, with coverage of Sinclair's calculators.
JULY 1975 REA AAA Sak ANS as — V——_—_——e - — Sinclair Scientific kit Britain's most original calculator now inkit form The Sinclair Scientific is an amazing calculator It offers logs, trig, and true scientific notation over a 200- decade range — features normally 8. 66 2 g9- oO l found on calculators costing around £50 or ° more. Yet even ready-built, it costs a mere £21.55 (including VAT) Andasakit it costs under £15! Forget slide rules and four-figure tables On the Scientific, ycu can handle directly all three trig functions, their inverses, logio, antilogio, giving quick acces to x¥ (including square and other roots), plus, of course, the four arithmetic functions and any calculation based on them In fact, virtually all complex scientific or mathematical calculations can be handled with ease. . Irad 57.2958" SIMNCiaiT- rio 230259 ¢ . 2:71828 Scientific 3.14159 Sois the Scientific difficult to assemble ? No. Powerful though itis, the Sinclair Scientific is a model of tidy engineering 1 All parts are supplied — all youneed provide is a soldering iron and pair of cutters. Complete step-by-step instructions are provided, and our Service Department will back you throughout if you've any queries or problems Of course, we'll happily supply the Scientific or the {Cambridge already built, if you prefer —they’re still exceptional value. Use the order form Features of the Scientific @ 12 functions ona simple keyboard @ Scientific notation @ 200-decade range @ Reverse Polish logic @ 25-hour battery life @ Genuinely pocketable Sinclair Cambridge kit Atits new low price, the Sinclan Cambridge kit remains unbeatable value The Cambridge is now Britain’s most popular pocket calculator. And it’s not surprising. Check the features — then ask yourself what other calculator offers such a powerful package at such areasonable price Features of the Cambridge @ Only 43" X 2” x 32". Weight 33 oz. @ Fully-floating decimal point. @ Algebraic logic. @ Constant on all four functions (+—X-+). @ Constant and algebraic logic combine to act as limited memory. @ Clear, bright 8-digit display. @ Operates for weeks ond AAA \ batteries. Take advantage of this money-back I~ T7Siciaiv Radionies Led, FREEPOST, St Ives, Huntingdon, Cambs., PE17 4B 7 no-risk offer today . | The Sinclair Cambridge and Scientific kits Please send me *lenclose a cheque for... 0. made are fully guaranteed. Return either kit | | ]Scientific kit— £14.95 ine. VAT out to Sinclair Radionics Ltd, crossed. | within 10 days, and we'll refund your | (Scientific built — £21.55 inc. VAT *Please debit my *Access/Barclaycard I money without question. All parts are _ |Cambridge kit — £9.55 inc. VAT account number: tested and checked before despatch — and l lCambridge built - £13.99 inc. VAT | we guarantee any correctly-assembled *Delete - ited ~ | calculator fora year. This guarantee also | GOES TSM | applies to calculators supplied in built form Simply fillinthe mentees Signed Name | below and post it — today ! Address | piaizzsc print. FREEPOST — no stamp required ETI/ 7/75 Sinclair Radionics Ltd, a a London Road, Stlves, Huntingdon, Cambs., PE17 4JH. Tel: St Ives (0480) 64646 [| | oo — || Rey. ne : 699483 England. VAT Reg, nu: 213 81/088. Ryets Pan woe ar a A — Blectronics today international JULY 1975 Vol. 4. No. 7. Special Feature BUMPER TECH—TIPS . Eight pages of this very popular feature Main Features VAT ANDCOMPONENTS . So a 9 © eee How the new rates affect the hobby THE HOME WORKSHOP. . . . . . - re |) Space, light, tools and components — getting it all together THEARTOFSOLDERING. .......... . 13 How to make sound solder joints — essential to successful building TELETEXT TAKEOFF! .. . . . . 2... ee 18 Things are beginning to move on this major British TV development HIGH VOLTAGE FOR LOWCOST . 2-6 3 8 SN 31 Theory and practice of voltage mulitipliers HOW AMBISONICS WORKS... foe eee 85 ETI disect the inventor's patents USING THE LM377N . . . . 2. oe - . 49 A chip containing two 2W audio amplifiers UNDERSTANDING COLOURTV......... . 58 Line and field synchronisation ELECTRONIC'SIT’SEASY . . . . . 2... . . . . 60 How regulated power supplies work Projects LINE AMPLIFIER . . . 1 2 - 2 es 24 Boost microphone outputs with this low noise amplitier STAGEMIXER..... .- oo 2 0 . es 26 16-line amplifier sub-mixes to eight channels — plus monitor ETI 3600SYNTHESISER. . . . 1... 2 2 ee 84 Building the voltage controlled filter News & Information NEWS DIGEST INPUT GATE 5 om 2 HM © off woo PREVIEW OF AUGUST'S ETI . ee AF PROJECT BOOK NO. 2 ELECTRONICS TOMORROW ET! PULSAR DIGITAL ALARM CLOCK OFFER. A magnificent product for only £13.95! Cover: Have you ever seen a tidy electronics workshop? A bit of ETI's lab is shown here: see Project Building Guide on page 10. Teletext receivers wilt soon be available to the public — page 18 (photo courtesy of Texas Instruments), EDITORIAL & ADVERTISEMENT OFFICE 36, Ebury Street, London SW1W OLW. Tel. 01-730 8282. HALVOR W. MOORSHEAD Editor ROBERT C. EVANS Advertisement Manager STEVE BRAIDWOOD, G3WKE Assistant Editor JEAN BELL Production HELEN COHEN Administration VALERIE FULLER Subscriptions & Back Numbers International Editions COLLYN RIVERS Editorial Director Australia BRIAN CHAPMAN Technical Editor BARRY WILKINSON Engineering Manager France DENIS JACOB Editor-in-chief CHRISTIAN DARTEVELLE Editor Published by: Modern Magazines (Holdings) Ltd 36, Ebury Street, London SW1W OLW. Electronics Today International is published on the second Friday in the month prior to the cover date. Distributed by: Argus Distribution Ltd. Printed by: Q.B. Newspapers Limited, Colchester. International Associates: Australia: Modern Magazines (Holdings) Ltd, Ryrle House, 15 Boundary Street, Rushcutters Bay 2011, Sydney, Australia. France: Electroniques Pour Vous International, 17 Rue de Buci, Paris, France. USA: ACP, Room 401, 1501 Broadway, New York, USA. European News Bureau: H. Dvoretsky, Manager, 107 Fleet Street, London EC4. READER QUERIES: These can only be answered If they relate to recent articles published in the magazine. Rarely can we supply information In addition to that published. Written queries must be accompanied by a stamped, self-addressed envelope, and telephone queries must be brief, not before 4.00 pm and can only be answered subject to the availability of technical staff. BACK NUMBERS: Back numbers of many issues are available for 30p each plus 10p postage. SUBSCRIPTIONS: Great Britain, £4.25 per year, Overseas, £4.75 per year. (Air Mall £7.50). COPYRIGHT: All material Is subject to World- wide Copyright protection. All reasonable care is taken in the preparation of the magazine to ensure accuracy but ETI cannot be held responsible for it legally. Where errors do occur, a correction will be printed as soon as possible afterwards In the, magazine. EX-COMPUTER STABILISED POWER MODULES complete with circuit 8p each 22p p & p. LOW COST CAPACITORS 01 uF 400V 3p each 3p each 500 uP 5OV Elect. op each DECON-DALO 33pC Marker Etch resistant printed circult marker pen 999 each diagrams, etc., De Luxe Groov-Kleen Model 42 £1-95 Chrome Finish Model 66 £1-50 364. Record/Stylus Cleaning Kit 38p Ref. 43. Record Care Kit 68-48 Ref. 31. Cassette Head Cleaner 889 Ret. 32. Tape editing Kit £1-68 Model 9. Wire Btrtpper/Cutter 637 Ref. B. Stylus and Turntable Cleaning Kit 4p R The largest selection BIB HI-FI ACCESSORIES Ret, P. Hi-Fi Cleaner 31p Ref, 324. Stylua Balance #1-57 Ket, J, Tape Head Cleaning Kit 629 Ret. 56. HI-Fi Stereo Hints & Tips 43) VEROBOARDS Packs containing approx., 50eq. ins. various ANTEX SOLDERING IRONS PLUGS | samen ae WORLD SCOOP! JUMBO SEMICONDUCTOR PACK Transistors-Germ and Silicon Rectifiers- Diodes-Triacs-Thyristors C's and Zenners ALL NEW AND CODED APPROX 100 PIECES! Offering the amateur a fantastic bargain Pak and an enormous saving—identification and data sheet sixes, all 0-1 matrle 5p X25, 25 watt 62-08 PS 1 D.LN. 2 Pin (Speaker) 0-11 in every Pak OCN 240, 15 watt £2-48. PB ow ONLY p&p 30p REPANCO CHOKES & COILS | model G. 18 watt 42-28 Hd O15 RF Chokes BK2, Boldering Kit 68-25 O16 a ~~ edad cons CHS, 1-bmH 28p SOLDER: 188WG Multicore 70s $1.61 Pa 7 DIN. 7 Pio os MAM MOTH I .C. PAK 1 61. 188) a T DRE] Crystal tet 19 DRE? Daal range Ap | STO Te Sgr teawe sar Ep PS § Jack 2-5mm Screened O18 APPROX. 200 PIECES PS 0 Jack 3-6mm Plastlo og ji ircuits i ing: ; COIL FORMERS & CORES Assorted fall-out integrated circuits including: Logic, 10 Jack 3°51 ened. i , ri i Cores & Formers top n™ pee MOCO Bae Teatst ous} 74 Series, Linear, Audio and D.T.L. Many coded id i - PS 19 Jack }° Bereened exe) devices but some unmarked—you to identify. 102 For mode) CN240 yy 42p SWITCHES . 106 For model CN240 %” 4gy | PB 15 Jack Stereo Bereened 0-38 OUR SPECIAL PRICE DP/DT Toggle 387 SP/ST Toggte Sop 1109 For model OON240 gi’ 42p aie Phono o-10 £1.25 including V.A.T.-& p. &p. 15 Car Acrial o-Re 1101 For model OCN240 42 6 8 16 Co-Axial 6-15 FUSES. soma, soma, oma, |i formes come a SPECIAL PURCHASE by BI-PAK A 1 4 * £1020 240 A” . . SO TA TER ZA ICE BLOW 5 em. Ho oat For modal 240 ft a | penbax soe nee ou} 2N3055. Silicon Power Transistors NPN EARPHONES 1022 For mode! G340 ¥" 429 | P8 22 DLN. 3 Pin 020) Famous manufacturers out-of-spec devices free from Crystal 9:5mm plug 42p 50 For model X26 yy” Mt } PS 28 DLN. 5 Pin 180° 9-201 open and short defects—every one able! 115 watts TO3. Crystal 3-Smm plug 42p 51 For médel X25 4° 48 | PS 2¢ D.LN. 6 Pin 240° 0.20 Metal Cas S ohm ¢smm plug 229 59 For model X25 4° 8p | PS 25 Jack 2.6mm Plastic 0.16 ota av ase) ind ELEMENTS PB 26 Jack §.5mm Plastlo 0.16 OUR SPECIAL PRICE 8 for £1. ECN 240 $130 ECON 240 1-88 PB 27 Jack 4° Plastic 0.80 Bizoe 20 gine pe et ee Sg | 2.240 1.07 EX.25 $1.16 PS 28 Jack 4° Gereened 0-85 | B-TRACK CART-CASES BOOK BARGAIN 2-Smmn and 3°bmem plugs 8188 ANTEX HEAT SINKS 10p | 7529 Jeck Stereo Piastic eas f Ho. 28: 139" 95 oe io BUNDLE z a V A T included in all prices, Please add | PS 31 Phono Screened 0.18 | Both with lock and handle. 8 Books compriaing: PHONE SUNeTION: BOX Dida nd estes for Postage eee Her | Pa 30 Car Aerial °.221 CASSETTE CASES £1-30 J Ratio & Eleciroals colour code and Biota ___61:67 a ie nial 9-227 Htolde 12, 10° x 34° x 8°. Lock & Handte j ‘sa chart = NEW COMPONENT PAK | ZocKETS : 3 "Other “centurion! books oa Re an oe ER PET) PS 30 DLN. 2 Pin (Gpeaker) ot¢| SOLVE THOSE STICKY | Ais0 9 General soasteoction book K4007. 60 ohma Imp. Insertion toss 34B 81-21 | Ho. Qty. Deseription Price | 3 97 DLN. 5 Pin 180° ou} PROBLEMS! pATUE Gr OUR PRICE C1200 ‘Resi roixed val 7 ee ; ‘ 2 P &p Op. TRANSISTOR EQUIVALENT count by welght PO. g4 § P8338 DLN, 5 Pin 240 oul) with BPL Handbook of Translator ced y ©2150 Capacitor mixed. valuea apron. | P8 30 Jack 3-5mm Switcined ole Equivalents & Substitutes 9th EDITION count by welght 0.64 | PS 40 Jack 3-5mm Switched og BP2 Handbook of Radio, rv"? 256 pages of cross references and equivalents | °? 59 Precision Resistors mixed values | PS 41 Jack 4* Switched oko Yndustrial Tube & Valve for "European, American and” Japanese 13% 0-64 | P8 42 Jack Stereo Switched °301 CYANQACRYLATE C2 ADHESIVE Equly. os transistors. Approximately 9,000 types with | 04 76 ith W Rerlstors mized preterred f P8 43 Phono Single O18 The wonder bond which works in | BPS Handbook of Tested Tran- more than 56,000 substitutes have been valves. 0-54 | ps 44 Phono Double 10] seconas bond plastic, subber, transistors sistor Circuit ndbook 12% Tresaged: Zhe tates were complied with the | C5 5 Pieces aasorted Ferrite Rods 0.84 | ps 49 Co-Aaia Surface 0-10 | components permanently, immediately! Bo er rere specication, The’ mos “comprehensive [C8 2 Tuning Gange, MW/LW VHHFO.64 | ps 47 Cocareyee 0201 OUR PRICE ONLY 54p Radio Stations and FM/T.V. Equivalents Book on the market today! }C7 1 Pack Wire 50 metres assorted 5 Listings 85 : ONLY £2-30 Ser 04 [LEADS for 2gm phial BPS Handbook of Simple Trar” Bm pacer O54 F381 Boeater lad 2 ro D.LN. pag to open rr aE oie tet RUMENT CASES C8 3 Micro switches 0.54 | ends approx. 3 metres long (coded) 0°20 BATTERY HOLDERS ‘codes and Data Charts. 15p INST C1015 Assorted Pots & Pre-Beta 0.54 Takes 6 hp 75 complete with terminal] BP dound and Loudspeaker Cll 5 Jack Bockets $x 30m 4 2 | CABLES clipand lead. S4p exclt ‘weual 3 Standard Switch Type 0.54 {CP 1 Single Lapped Screen 0-07 BPP 38 Practical Teated Diode 12 30 Paper Condensers preferred types CP 9 Twin Common Screen 011] CARTRIDGES Circuta for “the Home talxed valued 0-54 JOP 3 Stereo Screened 0-12 | ACOS GP92-180 200m at 1-2ems/sec $1:38 | BP10 Modern “Cryatal and Trane ©1320 Electrolytice Trans, types 0-54 [cP 4 Four Core Common Screen 9.28 | ACOB GEOG, 260mV at Lem/sec nas sistor Set Clreulte for (Black Vinyl covered) C14 1 Pack assorted Hardware— CP 6 FourCore Individually Screened 0-30 | ACOSGPOG'} 100m at lem/sec : beginner et Neo Ugngth Width Helaht Price Nuta/Bolta, Grommeta etc. 0-54 f cp § Microphone Fully Braided Cable 010] te Y-2010C Ceyetal/ i “Output Compattine pad Poincar Novel i a a a F138]C15 5 Mains Slide Bwitches,2Amp O-54 cp 7 ‘Three Core Mains Cable 0-08 81.20 | P13 Electronic Novelties for the <4 C16 20 Aseorted Tag Btripa & Panels 0-54 }op ‘Twin Oval Mains Cable 0-07 | TTC J-20068 Stereo/HI Output 1.75 Motorist Sop cl7 lo Assorted Control Knobs 0-54 cP 9 3 er Cable 0-08 TTC J-2105 Ceramic MedLOutooy $1.95 |} BP14 Second book of eee ALUMINIUM BOxES 1 C18 4 Rotasy Wave Change Bwitches0:541 CP 19 Loe Laws Co: Axial 0-15 | “ncioiting wtylegn nn OY /Semmlnec. BPLB Consiructors Manual of Blee Baa ae x a oS Tf Peper 2 Retayss-aev 0, Cl ro ‘TTC J-22038 Replacement stylus for tronleGieults” for the A3 4° C20 1 Bheeta Laminate ke above £3.00 home Ba Ho x 2 x it sep lor ee matr POTENTIOMETERS ‘TTC AT-55 Audio-technica magnetic 129 Universal Gram Motor Speed BAS ¢ xX 2 x 3 4p eat cartridge 4mV/Sem/sec 43.30 Indleator Pp Bar fe x ge x dj. ae (7K, 108, 22K, 42K, 100K 220K, «70K,1 CARBON FILM RESISTORS | asiswbandelitjs isp BAT 7- x 5 x fe BS Please add 10; .d pack! ‘7K, 10K, 22K, 47K, 100K, 220K, 470K, serials BAS 8° x 6 x aL on all component packs, lua a | TM, 200 The E12 Range of Carbon Film Resistors. | 241 Radio Servicing for Amen in ee a farther 10p on pack Nos. Cl, C2, 1 VC? Bingle Leas Switch O16 |} watt avallabie in PAKB of 50 pleces, {14g High Fidelity Loudspeaxer P & p L6p on each box GED VO2 ingle D.P. Qwitch 0-28 f assorted Into the following groups:— enclosures wat VC3 Tandem Less Bwiteh 0-48 [R150 Mixed 100 ohms-820 ohms 0p 156 Transistor Circulte PLEASE NOTE: ALL OUR PRICES INCLUDE V.A.T. VC 4 1K Lin Less Bwitch O16] R2 60 Mixed 1K ohms-8:2K obs SOPH 159 GNI ang Construct? AMTRON KITS VC 5 100K Log antl-Log 0-46) R3 50 Mixed 10K ohms-82K chms 50p ‘Manus ‘Modet No. er HORIZONTAL CAR N R4 50 Mixed 100K obms-1-Meg. ohms §0p J 161 ae T.V. and Bec " ce BO. THESE ARE UNBEATABLE PRICE8— ata book 65 Simple transts tester . ‘Transl Vals Ampliteriow” £791 PRESETS JUST 1p EACH INCL. V.AT. bt teense oubminiatre UK220 = Signal Injector 0-1 watt 0-06 each r ‘Transistor Test Equipment & UESI0 AM/FM Ancuna Ampliner 2353 )02 we ' BI-PAK SUPERIOR QUALITY | “genic Tart Equipment | UE275 Mike Pre-amplifier 27-38 | [Od 220, 470, 1K, 2-2K, 47K, 10K, 22K, 176 = Manual of Transistor Audio bret f-chaonel Radio Gootrot Tranmniter Er bb) ATK, 100K, 220K, 470K, 1M, 2M, 4-7 LOW,NGISE Cael “arablinaeg lo Con! . UKS25 ‘GCX2" Chancel splitting unit 1,000 & 2,000 Hz je3 eo) SELENIUM BRIDGE Se P0120 589 ____ [178 conupretenstve Raut Valve UK330 “GCX2' Channel splitting unit 1,600 & 2,500 Hz 20-75, RECTIFIERS SEE OUR COMPLETE RANGE | 183 How to receive foreign T.V, DEBS Batio Control Field Strength Meter £7.25 | Chargers. 16p each. 10 for 85) PRACTICAL ELECTRONICS, fis ar-nF Reactance-Frequency teats = 30 ——— ea UR0 iChannel AP tones 4ilss] REPANCO TRANSFORMERS| PRACTICAL WIRELESS, || Handbook of Practical Elere Etectroaice Unit for Metal Detector £12.89 ] 240V. Primary, Secondary voltages avaliable] RADIO CONSTRUCTOR, tronic Musical Novelties 60p PRESS Guitar pre-amplider £537 | trom selected tapings 4V, 7V, 8V, lov,| EVERYDAY ELECTRONICS, | 21 practical Trasslat: seed Nove UKES7§ Capacitive Discharge Electronic Ignition for Internal Combustion Engines £14.47 J 14V, 15V, 17V, 19V, 21V, 25V, 31V, 33Ve ELECTRONICS TODAY elles for Hi-F¥ Batbuslats 40¥, 50V, and 25V--25V, 2 VISIT OUR COMPONENT SHOP roy ARM Pie EL On SEND SN FOR THE |? Uagitock of leer MTS “33 45>] OR SEND 5p, FOR THE Circle Rquivalente an 18 BALDOCK ST., WARE,.HERTS. (A10) MTBO/L 1 rer} 48p] FULL LIST OF ALL BI-PAK j po, i0bttutes a iP Open Mon,-Sat. 9-5.30 p.m Tel. 61593 MT50/2 a $320 80p PRODUCTS Calculator 10 = e = @ = . A NOW WE GIVE YOU 50W PEAK (25W R.M.S.) PLUS 74 Series T.T.L. 1.C’S THERMAL PROTECTION! coR ONLY BI-PAK STILL LOWEST IM PRICE, FULL SPECIFICATION The NEW AL6O Hi-Fi Audio Amplitier GUARANTEED, ALL FAMOUS MANUFACTUREES £4. 25 — @Max Heat Sink temp 90° @Thermal Feedback . Quantiggs Type Gvantiies ‘Quanctles i $] ‘ i) 2s i] ‘ 1 25 . on) (Ola O13 | rag) feta = £607 EOS 070 668 ~—«-.065- | @Frequency Response 20Hz to @Latest Design Improvements Os 014 «013 | 74800 OS A013 075 073 «© 070 100KH2 O15 O14 0413 | 7451 O15 014 013 0.85 082 079 @Load - 3,4, 8 or 16 ohms ols OM AR FAST oe O14 ely £130 el2s ret eD . ey h 0.1% Os O14 i W484 OL: Ol Ol £150 £14 130 istortion better than e o1S of4 013 | 7460 O15 O14 O13 £L10 «£408 ELO0 tiKH @Signal to noise ratio 80dB , 039 «034031 | 74700032029 027 £100 095090 a B . - 0.39 034 ou 1472 ox 939 027 £t 10 £165 £1.60 Cant , 15-50 vol @Overall size 63mmxi0Smm @ FR. 0-25 024 2. FAIR O4t 0.35 £120 cis {1-10 u! voltage i volts aos om 92 024 os | 771 ot 3908s £200 fs eg Ply a 63 Detatid - O14 L TATS 0. t 9S o i 4 A ‘ at er oe oS ep OO 9 9 yop 035.038 TF Especially designed to a strict specification. Only the finest is 028 027 026 7480, 060 O58 A 55 el Ae el a3 ei iy components have been used and the latest solid state circuitry Sands 032 O31 03» TAR) £1-10 £105 00 1-40 £L3S £130 i yr i u H H i bats 339 O28 eae ed ORS O80 iva E838 ELGO acorn stated) in Gy Gea Bt] amplifier which should cy 030 0290 028 | 74X32 £8200 EIS £105 £180 £1.75 £1.70 f Satisfy the most critical A.F., enthusiast. ols Ol O13 | 7494 £1.00 097 0.95 £180 £175 £1-70 FULLY BUILT - TESTED and GUARANTEED 030 029 028 TARS £1.60 £15 £150 £1.60 £USS £150 O40 039 038 T486 035 O34 033 £1-60 ESS £150 040 039 038 THRO £4.00 43-75 £3.50 £1-10 £105 £1.00 040 «038 «= 036 | 7490 06S 0630-60 £125 £0200 £118 040 038 036 7491 £10 £105 £1.00 FANTT £1.25 £1.20 Enis O45 042 ae ue O74 o7 foe Ay £1-25 £1-20 ay os ol 49 074 O71 64 IRL £3.95 £3.85 £3. . 040 O38 036 7494 Oss 082 075 74182 £125 £120 £Lis MODULE SPM80 £3 25 042 040 038 7495 oss 082 07s TAR £1-80 £175 £1-70 03s 032 030 1496 0% 093 086 W490 £195 £1-90 £1.85 SPMRO is especially designed to power 2 of the ALA0 Amplifiers. up to 035 032 030 T4100 £1.50 £145 £1-40 191 £195 £1.90 £185 1S watt (r.m.s.) per channel simultaneously. This module cinbodies the ols ol4 013 74104 060 oss O55 TAI92 £1.95 £190 £L8S latest components and circuit techniques incorporating complete short O14 o7 0-64 TAOS 060 058 055 T4193 £1-98 £1.90 £185 circuit protection. With the addition of the Mains Transformer BMTRO, 074 «071 «= 064 | 74107 044 042040 | 7514d 10 N25 £1.20 the unit will provide outputs of up to |S amps at 3S volls, Size: wai £120 EIS bt | 74110 06008580 | 7319S E110 «£1.05 £100 62 ayn oC 10S mm x 20 mm. These units enable you to build Audio Mas £120 fvis £110 74 090 08s 08s 731% £120 £05 £110 Systems of the highest quality at a hitherto unobtainable price. Also W448 £160 ELS £150 | 741k £100 095) = 090 | 74197 1200 EIS EEO ideal for. many other, applications including: Disco Systems, Public W460 £1200 EES E110 | 74119 ESO. «£140 £130 | T419k «27542-70265 Address. Intercom Units. ete. Handbook availahle. 10p. 447 £110 £1.07 £1-05 T4121 050 0-48 045 74199 £2.80 12-40 £2.30 DEVICES MAY RE MIXED TO QUALIFY FOR QUANTITY PRICE. (TTL 74 SERIES ONLY) DATA IS . AVAILABLE FOR THE ABOVE SERIVS OF Les fh GOOKLET FORM. PRICE Sp. TRANSFORMER BMT80 £2.75p. & p.40p INTEGRATED CIRCUIT PAKS. turers Fall Outs” which include Functional and Part Functional Units. These are classed is “nu a the maker's very rigid specifications. but are ideal for learning about LC 's and experimental with Pak No. Contents Price Pak No. Contents Price Pak No. Contents Price Uicod 12. 7400 054 UCI S$. 1446 084 LIEV Ss . 7490 054 vicor 12. 7401 034 UICaR 5. 744K 054 Oley). 7491 054 uicor 13 - 7402 084 UICSO 12. 7430 O54 ice? § . 1492 054 UICor 13 - 7403 054 UIC! 13. 7401 054 uneyi § . 7493 034 13 - 7408 054 UICS? 13 7453 054 UIeds § - TH98 O54 12 7408 054 UECSS 13 + 7484 054 ices § - 7496 0-54 8. 7406 0-S4 VICHO 13 7460 054 UICs 8. 749% 054 8. 7407 054 UICI -#- 7470 054 UIC1oH $7410 054 12. 7410 054 Ui? x. 7472 054 UII. 7411 054 1 720 054 UIC? &- 7473 054 UICLaL S$. 74144 054 13. 7430 054 UIC74 K - 7474 054 UICISE &- 74181 054 12.1490 054 UIC! - 7476 054 UICIS4§ - 74184 034 S441 054 UICKO$ - 7480 0-54 UICI9s 74193 054 S 7482 054 UICRI & . 7481 054 tele $. 74199 054 5 7443 054 WICK? & 5 7482 054 5. 7444 054 UICRIS . 74R3 054 UICXY 28 Assorted 74's £165 ules. 7445 054 UICRS 5. 7486 054 Paks cannot he split, but 28 assorted pieces (our mix) is available STEREO PRE-AMPLIFIER TYPE PA100 Built to a specification and NOT a price. and yet still the greatest value on the mprket the PAIOO stereo pre amplifier has heen conceived from the latest circuit techmaues Designed for use with the AL60 power amplifier system. this quality made unit incor prates mo fess than eight silicon planar transistors, two of these are Specially selected low noise NPN devices for use in the input stages Three switched stereo inputs, and rumble and scratch fitters are features of the PA 100. which also has a STEREO'MONO switch, volume. balance and continuously variable ass and trebie controis. SPECIFICATION: Frequency response 20H2—2ukHz + 14B Baas control $158 at 20H: Harmonie distortion better than 41% Treble control £150B at 20kHs Tepute:1. Tape bead 1-26m¥ Into 50KQ Filters: Rumble (high pass) 100 Hz 2. Radio, Tuner SMV into SOKN Berateh (low pass) 8kHz 3. Magnetic P.U, —1-Sm¥ Into 30KQ Gigoaljnoise ratio better than +654B All Input voltages are for an output of 250m¥. Laput overload +2648 Tape and P.U. inputa equalled to RLAA curve Supply +35 volte at 20mA within 4 1dB trom 20Hz to 20kHz Dimensions 202 x 82x 38 mam LINEAR I.C's—FULL SPEC. DTL 990 SERIES DUAL-IN-LINE SOCKETS. only £14.25 Type No 128 100 LOGIC 1.C's . 1802 050 048 = 045 Fite M4 16, Lead. Soskets_for use wih RW O25 023 020 BP 2 C's, anges: 73709P 020 019 © 018 ness PROFESSIONAL & NEW LOW COST AL10/AL20/AL30 AUDIO AMPLIFIER MODULES B70 035 033) © 030 Bf nim 4 1S- 77st 030 0.29 028 hens Ppa ' EME 99 00NpE The ALI0, AL20 and AL30 unite are BIBIC 028 027 0 26 TSO 16 38p 3Sp 32p aimilar In their appearance and in tbeir 72741P 030 029 0.28 Mime TO2. 15) 70p 68p general specification. Howeve: 72787 085 080 0-75 pane LOW COST N. selection of the plastic power di 7374RP. 038 036 034 fine BPS 8 pin type 3p 3p 1t reaulted in & range of outpat powers trom SL201C 0350 048 = 0.40 Bes if top ib 2p 2 to 10 watts B.M.B. SLI01C 050 045 © 040 BPS 16 1% Iso 3. The versatility of their design makes them SL702C 050 045 040 Paemptemmanisin Ideal for use {n record players, tape recorders, TAA] 080 070 «0.60 TUMERICAL stareo ampliders and cassette and cartridge TAA29R £100 O95 09 INDICATOR TUBES tape players in the car and at home. TAAMSOA £1-BS £180 £1-70 Ty De: vATOXC 0-28 0260.24 ee, Pee eS i bey 3015F. Muntron 7 Segment jndicator £1.20 tATEL O35 033 0-30 MAN 3ML.E.D. 7 Se; nt Disp: VOLTAGE REGULATORS -emet isplay gATI2 O35 038930 DTG. Plastic 1-5 Amps 0.127" High Characters £1.90 aremeles: Reptliite Mectermasse 74003 £150 £148 £140 1A, 7805/1129 $V (Equiv. to HARMONIc DiSTORTION Po= 3 WATTS [=1KHs 025% 1602 £bSO £145 £1.40 MVRSV £135 BE FARUATS, — TeAao 095 093 090 IATRIZ/LAAO L2V (Equiv to CATALOGUE AND LISTS LOAD IMPEDANCE a 8-160 LM380- £100 097 0.95 MVRI2V) £135 Send $.A.E. and | 8p. Nees 065 063 060 INPUT IMPEDANCE 1-1KHs 100% ah o.33) lees C Th STEREO 20 FREQUENCY RESPONSE GB 34B Pe Wattt bo KH: ZNA14 —_£1-20 e £14.45 pap ssp QUEN 4B om? WATTS Br-25KBs SENSITIVITY for RATED O/P Veu35V. Ri=8Q t=1KEs TomV. RMS TEAK VENEERED ‘The ‘Stereo 20° amplifier ts mounted, ready wired and tested —m CABINETS for: 08 one-piece chassle measuring 20 em x 14cm x 8-8 em. DIMENSIONS ~ ox ay" x OF: ‘Thie compact unit comes complete with on/off swite! ‘STEREO, 20 yolume control, , bass and treble controls, The above table relates to the AL10, AL20 and ALSO TC 20, £3-95 p&p 4$p lormer, Power sapply and Power amps. modules. The following table outlines the differences Attractively printed front panel and match. in thelr working conditions TC 100. £650 p&p 40p. tag control nobs, The ‘Stereo 20° haa bees EM. LEK 350 Loud: . jesigne it into most turntable plinths ce wit tering oh the mechan Fenner § alternatively, into eo seperate cabinet. a leneer, including speakers. Output power 20w peak. Input 1 (Cer.) imam Supply Voltage Rec Retail Price £4$-50 per pr. 00mY Into 1M. Freq. res. 26H: es. OUR SPECIAL PRICE £35-50 lopat 2 (Agx.) 4mV into 90K. Harmonle Fower/outputisre|20t7 EDS er pair p&p £1. ONLY WHILE atscortson 4 Bam control a: 124B fet Teatis Udon) yp! ly 0: a watt, ble con. STUCES LAST #1423 ot Vania. PRICE FRONT PANEL, 4 [nobs, Headphone, Socket, ‘oft switch and neon for PA MK FPK 100 £2.95. ° on/ 50. TRANSFORMERS can be from their ad power T461 (Use with ALI) £4.60 P&P 22p | Thare are two stereo lopata, one has been designed for use 1538 (Use with AL20 & AL30) £2.30 & P 22p Fwith *Ceramic cartridges while the suriliary Input will BMT80 (Use with AL60) £215P&P i7p J ealt most tMagnetic cartridges, Full detaiis are given io POWER SUPPLIES PS 12. (Use with ALIO, AL20 & AL30) SPM 80. (Use with AL60) PA 12. PRE-AMPLIFIER SPECIFICATION ‘The PA 12 pre-amplifer has been designed to mateb into most budget stereo systems. It ts compatible with the AL 10, AL 20 and AL 30 audio power amplifiers and it Prequency response— ‘20Ha - 60K Ha (— 348) ‘Bass control— & 1248 at 60He ise 282mm x S4mm x 35mm. 95p £323) PFRONT PANEL FP 12 with knobs £1-00 the specification teble. The four controls are, trom left to right: Volume and on/off awitch, balance, bass and treble. PRICE £4-35 . | Treble coutrol— & 144B ot 14K Bs *Topat 1, Impedance 1 Meg. ohm Gevsltivity 300mV tInput 2, Impedance bine v eo » O 30 K 01 Bensitivity 4m’ BIC VENTURI LOUDSPEAKERS These BIC Venturi speakers utilise a new method of reproducing bass freq- uencies based on the Venturi principle. The acoustic energy output is much higher and a much purer signal results. Low-velocity air motion in the cabinet is transformed to high velocity air motion in a venturi-coupled path. At very low bass frequencies the amp- litude of the signal from the opening of the venturi-coupled path is sub- stantially greater than from the front of the woofer itself. The venturi- coupled path’ functions also as an acoustic low pass filter, removing unwanted harmonic content. All the BIC Venturi speakers feature a continuously variable “Brightness” control on the front panel. There are four speakers in the News digest range. The Venturi Formula 1 will handle up to 50 rms, and. will cost approximately £45.00 each (exclud- ing VAT). The Venturi Formula 2 will handle 75 rms watts, and will cost approximately £65.00 each (excluding VAT). The Venturi Formula 4 wiil handle 100 rms watts and will cost approximately £80.00 each (excluding VAT). The last speaker in the range is the Venturi Formula 6 which gives a response of 20Hz to 23kHz, and can handle 125 rms watts. The price will be approximately £130.00 (excluding VAT). These speakers carry a three year (parts and labour) guarantee and are available through Belmont A/V Limited Fircroft Way, Edenbridge, Kent. DIGITAL WATCH PRICES TUMBLE Digital watches may soon be selling for less than £30 — and could be as low as £12 in two years time. This forecast was made by Victor Kiam of Benrus Corporation during a digital watch seminar held in New York.earlier this month. As if to illustrate Kiam’s point, Litronix (Cupertino, Califronia) announced a range of five LED readout watches costing from $50 — $60 (£20 — £24). Not all manufacturers are aiming for ultra-low prices however. Intersil for example are about to introduce an LED readout wristwatch range (called Cronus) selling for around £80 — £150 NEW COMET DISCOVERED Astronomers in the Crimea have discovered a new comet — provisionally named 1975-E, It is relatively close — not more than 400 million miles away but the size and orbit have not yet been calculated. SASER? Professor S. Altshuler of Kazan University, USSR, is developing acoustic generators and amplifiers working on the same principles as the laser. They are the outcome of the university’s research into acoustic Paramagnetic resonance in solid body physics. FRANCIS GRAHAM It is with deep regret that we announce the death of Frank Graham on May 17th at the tragically early age of 27 after a long illness which he bore cheer- fully. Frank was ETl's regular photographer and although rare- ly credited in the magazine, few issues in the last two years did notcarry his work. Although not a staff member, Frank was a regular visitor to ETI’s offices and we downed many a pint with him. He was invariably cheerful, helpful and, was a perfectionist in his photography. We shall miss him. LASER MISSILE INTERCEPTOR The US armed forces may soon have a laser missile interceptor. Air Force reports state that prototype deuterium fluoride lasers have been successfully tested at ‘very very high’ power out- puts. Power output is apparently so high that the laser beam burns straight through heavy gauge stainless nickel steel plate. SOVIET RADAR BLAMED FOR HIGH HEART DISEASE A Russian radar tracking station near the Finnish town of Ilomaritsi may be responsible for a sharp increase in heart disease and cancer according to Dr. Milton Zaret, an American micro- wave expert. ° The Finnish border towns have the highest rate of heart disease in the world and cancer has increased inexplicably. ELECTRONIC CHEQUEBOOK CALCULATOR A pocket calculator that will hold and display bank cheque account balances for a year or more is shortly to be announced by the US Mostek Corporation. During the times that the calculator is ‘off’ data is stored in a static shift register (drawing a mere 100 micro- amps). This data is then clocked solely when access is required. The unit is expected to retail for less than £16 and will be built into a plastic chequebook holder. ©) a) SS asa A: SN SU A I NI CA i Se Eada KE mame Please mention news digest in any enquiry. When the Chancellor, Mr. Healey, introduced the higher rate of VAT (25%), this was clearly done to tax ‘luxuries’. Amongst other categories of goods qualifying for the higher rate are Radio, TV and Audio equipment; When component suppliers received the new instructions they found in the small print a number of other cate- gories, most of which were obvious candidates — TV aerials etc. — but also listed specifically were transistors, valves, resistors, coils and capacitors suitable for use in these higher rated goods. The position of kits was not covered. H.M. Customs and Excise, who administer and collect VAT, were asked by ETI what the new rate covered. They have been placed in the unenviable position of having to interpret the new rulings. It became clear that the Customs and Excise were as confused as everyone else! As a result, Halvor Moorshead, Publisher and Editor of ETI, organised a deput- ation of representatives of the com- ponents retailers to meet Customs and Excise to arrive at a workable inter- pretation. The companies represented were: Marshall’s, Ambit, Heathkit, Electrovalue, Henry’s Radio, Home Radio, Bi-Pak, Bi-Pre-Pak, Maplin, Doram, L.S.T., Bywood, Chromasonics, Tandy, Crescent Radio and Garland Brothers. Representation was made to obtain a workable definition, not to protest VAT AND COMPONENTS the rate, as Customs and Excise cannot make such decisions. The outcome was that the following list was proposed by the delegation and accepted as an interim definition by H.M. Customs and Excise. SUBJECT TO 25% VAT 1. Transistors FET’s and valves, 72, Resistors - fixed value types. 3. Capacitors including variable capacitors. 4, Potentiometers and presets. 5. Diodes and Rectifiers. 6. RF Coils, IF transformers cera- mic filters. 7. Moving coil loudspeakers. 8. Microphones and _ accessories, headphones and earphones. 9. Linear IC's inc. Amps, Op. Amps and PLL. 10. Radio, TV and audio modules. 11. Radio, TV and audio equipment parts and accessories such as aerials preselectors, cabinets, din plugs, printed circuit board, (for Group 2 items) and ferrite aerials. 12. Musical keyboards and access- ories, guitar pick-ups, spring-line units. All other goods are subject to 8% including digital IC’s, transformers, test gear etc. Copies of letter received by ETI from H.M. Customs and Excise confirming this are available to bona fide manufacturers and com- ponent suppliers from ETI on request. Kits were also covered. Where the built-up kit would qualify for the higher rate, the VAT will normatly be charged at 25%. Where a kit, when built-up, would qualify for 8%, the whole kit will be 8% except when those components which normally fall in the 25% category comprise more than 33 1/3% of the final value. In practice, this means that virtually all kits which would qualify for the 8% rate when built, continue to be at 8%. This dual rate is causing enormous problems amongst the component suppliers, so bear with them. It certainly appears that compo- nents have been put in the higher rate to avoid loop-holes, not because the Chancellor wanted to tax the elect- tronics enthusiast. This seems very unfair to us and if you agree there is something you can do about it ~ you don’t have to sit back and take it: write to your M.P. If the number of M.P.’s, especially Labour ones, are convinced by your arguement, the Government may change their mind — it’s not as far-fetched as it appears — there are many precedents for correct- ive Legislation where it is found that the original draft has loop-holes and people are being taxed for something which was included only to prevent loop-holes. Don’t complain to your component suppliers, or to us — write to your MP. ANALOGUE MEMORY A device to store an analogue wave- form, to play it back at a slow speed for oscilloscope or x-y plotter display, has been introduced by Kemo (9 Goodwood Parade, Eimers End, Beckenham, Kent BR3 30Z). The AM1024 digitises a time segment of the signal and stores up to 1024x9-bit words. Sampling interval is controlled either by internal crystal, for the range 3uS to 300mS, or by an external source, for longer intervals. The store is fed continuously until the memory is instructed to hold the waveform, then this is read out to the display. ETI/DANAMETER COMPETITION —APRIL 1975 ISSUE— This competition closed on April 30th and, as usual, it was a great success, The correct answers are shown. We were slightly apprehensive about setting the level too high but reactions from readers show that generally people prefer something challenging. No. 8 down “Earliest ‘air’ crossing of the Atlantic refers to Marconi’s radio experiments — we did put ‘air’ in inverted commas to draw attention to this but quite alot of people got it wrong. The first three correct entries drawn after the closing date were from: S.D. Boyd of Stubbington, Hants. M.P. Conroy, Wimbledon Chase, London sw2o. D.M. Weiss, London NW6. a “Gi 7 1 1 SINCLAIR WIN QUEEN'S AWARD The Queen’s Award to Industry, 1975 has been won by Sinclair both for outstanding export achievement and for technological innovation in scientific calculators: only two company’s have won Awards in both categories this year. In the three years up to March 1974, exports increased 10-fold to £2,232,000 or 56% of turnover. The Award for technical innovation is for the Sinclair Scientific which will be well-known to ETI readers. Sales topped £1 Million, over half of them exported. Of the UK sales a significant proportion resulted from the ETI/ Sinclair reader offer in October 1974. Other electronics companies to win the Queen’s Award are two divisions of BICC, EMI and Micro Consultants, a company employing only 80. in the latter case the Award was for Technical Innovation for its range of video analogue and digital converters. Ry EN AAU IE Eh A MYSTERY WALKIE TALKIE London's Fire Brigade are currently evaluating a ‘mystery’ walkie-talkie system that enables firemen to communicate with each other even inside steel-framed buildings. The ‘mystery’ is that no-one — including Plessey, who developed it — totally understands just how it works! buildings has always been a major problem, UHF and VHF radios are useless in these conditions and cable linked systems are cumbersome and prone to damage. Office investigated the problem and found that rf energy at 3MHz will penetrate steel-framed buildings. The frequency seems to be fairly critical and, say Plessey there must system to work. ‘It works’ says a Plessey spokesman, ‘but honestly we don’t know why’. — known as Figaro — have been supplied to Britain's fire brigades for evaluation. The first real-life test came during the recent Moorgate underground train disaster where it was used to communicate from the disaster site underground up to street level. The system apparently worked extraodinarily well. CLASS OF ANTI-GRAVITY MACHINE THESE DAYS; EH?! news digest Communication within steel-framed Plessey, under contract to the Home be some metal structure around for the Twenty four sets of the new system TIMER IC The Ferranti ZN1034E is an IC that will accurately time processes lasting from milliseconds to weeks. The 14-lead DIL package requires only one external resistor and capacitor. It has a drive capability of up to 25mA. It can be powered by battery, froma 5V TTL rail, or from the mains. Features of the ZN1034E include repetitive and cascade operation, an internal/external calibration facility, mains contact or TTL triggered timing sequence initation, a temperature stability of <0.01%/°C and accurate repetitive timing of typically 0.01%. It provides time intervals up to 7500CR through its 12-stage counter, and gives complementary TTL compatible outputs. The ZN1034E utilises digital and Precision linear functions on the same chip. The frequency of the on-chip oscillator is determined by an externally connected capacitor and resistor. In addition, fine adjustment can be achieved by connections of a calibrat- ion timing. Pulses from the oscillator feed through a 12-stage binary divider which times out after 4095 counts. A voltage regulator is incorporated and two modes of operation can be used. The one off price is £2.99 from Edmundson Electronic Components Ltd., 30-50 Ossory Road, London SE1 5AN. SINGLE CHIP MICROCOMPUTER The TMS 1000 is a complete self-contained micro- computer system on one P-Channel MOS Chip. It contains an 8192 bit ROM for programming, a 256 bit RAM for data storage, and a 4-bit binary ALU. In addition the chip has 13 control outputs set under Program control, 1 4-bit parallel input port and a sep- arate 8-vit parallel output port. An incoming binary word of up to 64 bits is read in in 4-bit hexadecimal digits and operated on by the ALU in digit sequence. There are two mask programmable areas on the chip in addition to the program ROM. The instruction decoding PLA can be mask programmed to provide variations of, and mergings of,