PRACTICAL ELEC ONICS MARCH 1973 20p

BI AS

3.75 S ORO VU BIAS 1138 75 Mi.

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- ******** ******** HI ILIAPE LINK is this the price youpay?

Probably, if you're still using an ordinary soldering iron. Ordinary soldering irons can cause damage to transistors and integrated circuits - damage which wastes time and costs money. Now, with the unique ANTEX X25 and CCN low leakage soldering irons no harm can come to the most delicate equipment, even when soldered 'Live' (You could be making quite a saving).

MODEL X25 220-240 Volts or 100-120 Volts. The leakage current of the NEW MODEL G X25 is only a few microamps and 18 watt miniature iron, fitted cannot harm the most delicat, with long life iron -coated bit equipment even when soldered 3/32". Vol -ages 240,220 "live". Tested at 1500v. A.C. MODEL or 110. PRICE: £1.83 This 25 watt iron with it's CCN Irec. retail). truly remarkable heat -capa- 220 volts or city will easily "out -solder" 240 volts. The any conventionally -made 15 watt miniature 40 and 60 watt soldering model CCN irons, due to its unique also has negligible s*" construct ion.advantages. leakage. Fitted long -life iron - Test voltage 4000v.`\, coated bit 1/8". 2 A.C. Totally enclosed MODEL CN other bits avail- element in ceramic shaft. able 3/32" and Miniature 15 watt Fitted long -life iron -coated soldering iron fitted N MODEL CN2 3/16". Totally bit 3/32. 4 other bits enclosed element 3/32" iron -coated \Miniature 15 watt solde ing available 1/8", 3/16", 1/4" bit. Many other bits,)iron fitted with ceramic and steel and 3/64". shaft. Bits do not available from 3/64" nickel plated bit 3/32". PRICE: £1.80 Irec. retail) to 3/16". Voltages 240, Voltages 240 or 220. "freeze" and can OR Fitted with triple -coated, easily be 220, 110, 50 or 24. PRICE: £1.70 iron nickel and Chromium bit 1/8".\ removed PRICE: £1.70 (rec. retail) Irec. retail) PRICE: £1.95 Irec. retail) j, PRICE: £1.75 (rec. retail) / Suitable for production work and as a general purpose iron. MODEL SK.2 KIT Contains 15 watt miniature MODEL MES.KIT iron fitted with 3/16" Battery -operated 12v. bit, 2 spare 25 watt iron fitted MODEL bits 5/32" , and 3/32" with 15' lead and 2 SK.1 KIT heat sink, heavy clips for con- Contains 15 watt solder, stand nection to car battery. miniature iron fitted with 3/16" and "How to Packed in strong plas- bit, 2 spare bits 5/32" and Solder" tic wallet with booklet 3/32", heat sink, solder, stand book let. "How to Solder" and "How to Solder" booklet. PRICE: £2.40 PRICE: £1.95 Irec. retail) PRICE: £2.75 Irec. retail) (rec. retail)

Please send the ANT EX I enclose cheque/P.O./Cash colour catalogue. (Giro No. 2581000) Please send the following: I

From radio or electrical dealers, NAME car accessory shops or ADDRESS in case of difficulty direct from:- ANTEX LTD. FREEPOST no stamp required) PLYMOUTH PL1 1BR Tel: 0752 67377. Pd PRACTICAL ELECTRONICS VOLUME 9 No. 3MARCH 1973

CONSTRUCTIONAL PROJECTS HI Fl TAPE LINK by P. S. Ewer All the electronics to bring Hi Fi to an existing tape deck 210

P.E. SOUND SYNTHESISER -2 by G. D. Shaw Twin stabilised power supply unit and racking details 232

SIGNAL INJECTOR and TRACER by R. A. Penfold Useful dual-purpose item of test gear for a.f. and r.f. applications 238

P.E. DIGI-CAL-9 by R. W. Co/es Logic and construction of the programme board 242

GENERAL FEATURES ELECTRONIC TIMEPIECES -1 by J. B. Dance Evolution of designs up to tuning -fork principle 221

DESIGNING WITH I.C.s-6 by A. Foord Basic memory circuits 249

NEWS AND COMMENT

EDITORIAL-Our Transistor 209 SPACEWATCH by Frank W. Hyde Is someone tryihg to contact us?-USSR meteorite research 217 ON THE FRINGE by Gerry Brown The more unusual aspects of electronics 218

INDUSTRY NOTEBOOK by Nexus What's happening inside industry 226 TRANSISTOR SILVER JUBILEE The team behind the invention-anniversary events 229 TRANSISTOR TRAIL Highlights of research and development leading to the first transistor 230 NEWS BRIEFS Tidal Monitoring-Radar Testing-UK Tops In Data Transmission 241 POINTS ARISING Biological Amplifier-I.C. Linear Ohmmeter 241 BOAT SHOW REPORT A look at marine electronics for the small boat owner 253 PATENTS REVIEW Thought provoking ideas on file at the British Patents Office 254 MARKET PLACE New products and component information 258

Our April issue will be published on Friday, March 9, 1973

Cc) IPC Magazines Limited 1973. Copyright inall drawings, photographs and articles publishedin PRACTICAL ELECTRONICS is fully protected, and reproduction or imitations in whole or part are expressly forbidden.All reasonable precautions are taken by PRACTICAL ELECTRONICS to ensure that the advice and data given to readers are reliable. We cannot, however, guarantee it, and we cannot accept legal responsibility for it.Prices quoted are those current as we go to press.Subscription Rates including postage for one year, to any part of the world, £2.65.

PracticalElectronics March1973 185 THE FABULOUSLY SUCCESSFUL VISCOUNT III AUDIO £52complete 14 + 14 watts r.m.s. 40Hz to 40kHzr.3dB. Total distortion at 10 watts PR CES SYSTEM Viscount III R 101 amplifierL22.00 +90p p&p at !kHz- 01%. 2 Duo Type 11 speakers L14.00 -1-L2 p&p This is real value for money! We have designed 2 systems and the heart of them Garrard SP25 Mk. 111 with all is the Viscount Ill amplifier. A unit of great eye appeal with teak finished cabinet. MAG. cartridge plinth and FET's (Field effect transistors) are incorporated on the input stages, just like top cover L23.00 +L1.50 p&p priced units.FET's give you more of the signal you want and almost none of the Total L59.00 hiss you don't.Both units have output sockets for headphones and tape recorder. Available complete for only L52 Filters and tone controls give a wide range of bass and treble adjustment. i- L350 p & p For both systems we have chosen the famous Garrard SP25 Mk.Ill deck, with fitted magnetic cartridge, which comes complete with simulated teak plinth and PRICES: SYSTEM 2 tinted acrylic cover. Viscount R 101 amplifier C22.00 +90p p&p The exclusive Duo loudspeaker systems are incomparable for quality within their 2 > Duo Type 111 speakersL32-00+0 p&p G d SP25 Mk. 111 with price range.Large speakers in extremely substantial cabinets.There's a choice of MAG cartridge plinth and the Duo II's for the smaller room or the big Duo II I's for real bass response. cover C23.00+ L150 p&p SPEAKERS Total 07.00 Duo Type II Size approx. 17in. 101 in. 61 in. Drive unit I3in. 8in. with parasitic tweeter. Available complete for L69 L4 p & p Max power 10 watts, 8 ohms. Simulated Teak cabinet. II4 pair + C3 p & p.

Duo Type I 11 Size approx. 23fin. II lin. ',fin. Drive unit 13fin. 8,1in. with H.F.speaker. Max power 20 watts 8 ohms. Freq. range 20Hz to 20kHz. Teak veneer cabinet. C32 pair + C3 p & p. SPECIFICATION R101 distortion IOW I kHz 0.1%. P.U.I. (for ceramic cartridges) 150rnV into 3 Meg. P.U.2. (for magnetic cartridges) 4mV . [kHz into 47K equalised within ±1dB R.I.A.A. Radio 150mV into 220K. (Sensi- tivities given at full power.) Tape out facilities: headphone socket, power out 250mW per channel. Tone controls and filter characteristics. Bass: -I-12dB to -17dB 601-4z. Bass filter: 6dB per octave cut. Treble control: treble -1-I2dB to -I2dB 15kHz. Treble filter: 12dB per octave. Signal-to-noise ratio: (all controls at max) -P.U.I. and radio -65dB, P.U.2 -58dB. Cross talk better than -35dB on all inputs. Overload characteristics better than 26dB on all inputs. Size approx. 131in. 9in. 3/in. Send S.A.E. for fully illustrated brochure. 12 MONTHS' WRITTEN GUARANTEE.British made. S.A.E. for illustrated leaflet. -ONLY FROM US

Times of opening: Acton-Mon.-Sat. 9.30-5. Closed all day Wed. Edgware Rd.-Mon.-Sat. 9.30-5. Closed all day Thurs.

186 PracticalElectronics March1973 MUSIC MAKERS

UNISOUND FOR THE NEW SOUND The whole system is complete including superb cabinets in simulated teakjust simply screw

hcaos emdp o. nn faanmd oy;ou ei e! system.Gharradrdi 202d5TC trntable.cpolms- AT stereo ceramic ge

the bigI 3in. Bin. EMI Twin -cone speakers ready for mounting in their elegant cabinets, which simply need screwing and gluing together. All glue and screws supplied. Easy to fellow step-by-step instructions guide you quickly and effortlessly to taking the wraps off truly realistic stereo sound. E25 complete plus E280 p. & p. Diamond Stylus EI25 extra. Power output: 4 watts per channel into 8 ohms. Inputs:120 mV (for ceramic cartridges). Stereo headphones with adaptor C4.00. UNISOUND MODULES ONLY E6.95 If you prefer, you can buy the three modules-pre-amplifier Power .4,1,1Y/dual power amplifier, and control panel-by themselves for only L6(95. P. & P. 50p extra. No soldering, just simply screw together with screwdriver supplied. Their overall specification is the same as shown for the complete Unisound console, using the high efficient I.C. mono- lithic power chips to ensure very low distortion at all power levels, correct operation in all ambient temperatures, full power over the audio spectrum. AN EXCLUSIVE DESIGN

AlATURAC ONLY FROMR C If you can solder on printed circuit THE PULLMAN PB CAR RADIO KIT board,youcanbuildthispush- Apart from the output stage, which is an integrated circuit, the only other electronic button car radio kit.It's simple- components that need soldering are some capacitors, resistors, etc. The kit includes a just follow the step- pre -built RF tuner unit, and fully modulised IF stages which are pre -aligned before despatch. As well as electronic components, this kit also contains 2 diamond -spun by-step instructions. aluminium knobs, elegant matching front panel, dial, washers, screws and wire. The Tourist PB is suitable for 12 volt working on both negative and positive earth vehicles. It covers the full medium and long wave bands. Four push -buttons for medium wave, one for long wave. It is permeability tuned and sturdily constructed. Output is a full 2:5 watts into an 8 ohm speaker. But the Tourist PB will operate into any loud- speaker from 8 to 15 ohms. Power consumption is less thanI amp. The Tourist PB can be mounted in any standard size dash panel and it has an illuminated tuning scale for easy reading at night. Approx. chassis size is: 7in wide, 2in. high and 411 in. deep (excluding front panel, etc.). * Circuit diagram and comprehensive instructions 50p, free with parts. * Fully retractable lockable car aerial L1.25 post paid. PRICE ONLY E7p & p 50p Speaker with baffle and fixing strips El .50 25p p & p, post free if brought with the kit. Send for illustrated leaflet

RELIANT MK.IV *5 Electronically Mixed Inputs. * 3 Individual Mimi% Controls. * Separate bass and treble controls common to all 5 inputs. * Mixer employing F.E.T. (Field Effect Transistor). * Solid State Circuitry. * Attractive Styling. * Sides finished in solid teak. INPUTS: -I. Crystal Mic. or Guitar 9mV. 2. Moving coil Mic. or Guitar BmV. Inputs 3, 4 & 5 are suitable for a wide range of medium output equipment (Gram., Tuner, Monitor, Organ, etc.). All 250mV sensitivity. CONTROLS: --3 Volume controls. Bass control range: 13dB (a 60Hz. Treble control range:: 12dB 15KHz. Separate ON/OFF Switch. Neon indicator. POWER OUTPUT:12 Watts R.M.S. into 3 to 4 ohms speaker. SIGNAL NOISE: Better than -60dB on inputs 3, 4 and 5 & -50dB onI & 2. SUPPLY: -220-250 A.C. Mains. SIZE:--12¢in. 0.50 6in. <3f in. NEW VERSION: 20 watts into 8 ohms 83.50 + 60p p&p plus p & p 60p The new 20 watt (into 8 ohms) version for just E3extra.All other specifications as JUST ANNOUNCEDabove. plus p & p 60p£1503 Radio and TV Components (Acton) Ltd. 2ID High St., Acton, London W3 6NG VISIT OUR 323 Edgware Road, London, W.2 R C Moil orders to Acton Terms C.W.O. All enquiries S.A.E. SHOWROOMS Goods not dispatched outside U.K. 187 PracticalElectronics March 1973 tonnouseur B.D.2 Press Button Speed Change Turntable The Connoisseur BD2 belt drive turntable with press button speed change is an integrated turntable and pickup arm assembly, the raise/ lower device of which is operated by the knob at the front right hand corner. The head shell allows for the lateral adjustment of the cartridge. The BD2 is supplied as a chassis unit or spring mounted cm a wood plinth complete with dust cover. B.D.1 Turntable Kit S.A.U.2 Pickup Arm The B.D.I. well known for its Recognised as one of today's most advanced superb performance and pick-up arms it features quality two speed working Auto -bias Compensator through a flexible belt drive Hydraulic Lowering Device system is now available in kit Precision Balance form. Construction is New Adjustable Head Shell. simplicity itself with no soldering required. Now it's so easy to own the best.

A.R.SUGDEN & CO.(ENGINEERS) LTD. Atlas Mill Road. Brighouse, Yorkshire HD6 1ER. Telephone: Brighouse 2142. Telegrams & Cables. Connoisseur, Brighouse VISIT OUR STAND AT SONEX

Vary the strength U.H.F. TV AERIALS of your lighting with a SUITABLE FOR COLOUR & MONO- CHROME RECEPTION All U.H.F.aerials now fitted with TA ITCH tilting bracket and 4 element reflector. DISCOUNT LOFT MOUNTING ARRAYS PRICES 7 element L225. 11 element L2.75. 14 element(3.25. 18 element £3.75. WALL MOUNTING c/w WALL ARM Newest, neatest S SIZES AND BRACKET. 7 element L3.2S. II element L3.75. 14 element L4.25. 18 element [4.75. system ever ALL INTERIM= CHIMNEY MOUNTING ARRAYS c/w C- devised for storing small MAST AND LASHING KIT,7 element E4. parts and components 11 element L4.50. 14 element L4.75. 18 resistors,capacitors,diodes,transistors, element L5.25. etc.Rigid plastic units interlock together MAST MOUNTING arrays only 7 element inverticalandhorizontalcombinations. L2.25. I I element L2.75. 14 element [3.2.5. Transparent plastic drawers have label slots/ 18 elementL3.75. Complete assemblyin- structions with everyaerial. LOW LOSS removable space dividers. Build up any coaxial cable 9p yd. size cabinet for wall, bench or table top. KING TELEBOOSTERS from L3.75. LABGEAR allbandV.H.F.-U.H.F.-F.M.radiomains BUY AT TRADE PRICES ! operated pre -amps L7.50.State clearly channel number required on all orders. P. & P. on all SINGLE UNITS (ID) (Sins 21ins 2tins). [1.35 DOZEN. aerials 50pacts.15p.C.W.O.min. C.O.D. The DIMMASWITCH is an attractive and effic- charge 25p. ient dimmer unit which fits in place of the normal DOUBLE UNITS (2D) (Sins 4f ins 21ins) £215 DOZEN. BBC -ITV -FM AERIALS light switch and is connected up in exactly the BBC (band I) Wall S/D [2. LOFT inverted same way.The white mounting plate of the TREBLE (3D) L2.35 for 8. 'T' £115. EXTERNAL 'H' array only CI ITV (band 3)5 elementloftarray 0.SO. DIMMASWITCH matches modern electricfit- DOUBLE TREBLE 2 drawers, in one outer 7 element L3. COMBINED BBC -ITV loft tings. Two models are available, with the bright case (6D2), L3'65 for 8, EXTRA LARGE 1 +5 L2.75. I +7 E3.50. WALL AND chrome knob controlling up to 300 w or 600 w SIZE (6D1) 0.30 for 8. CHIMNEY UNITS ALSO AVAILABLE. Pre -amps from L3,75. of all lights except fluorescents at mains voltages PLUS QUANTITY DISCOUNTS ! COMBINED U.H.F.-V.H.F. aerials 1+5 +9 44. from 200-250 v, 50Hz. The DIMMASWITCH has 1 +5 +14 04.50.I +7 +14 LS.F.M. RADIO Orders L5 and over DEDUCT V. in the L loft S/D LI.3 element L3.25.4 element 0.50. built-in radio interference suppression: Orders CIO and over DEDUCT 71% in the L Standard coaxial plugs 9p. Coaxial cable Sp yd. 600 Watt-- L3.20.Kit Form 42.70 Orders a0 and over DEDUCT 10°;, in the Outlet box 30p.P. & P. all aerials 50p, aces. 30p. 300 Watt-- t2.70.Kit Form 12.20 C.W.O. min. C.O.D. charge 25p.Send Sp for PACKING/POSTAGE/CARRIAGE: Add 35p fully illustrated lists. All plus !Op post and packing. to all orders under L5. Orders L5 and over, CALLERS WELCOMED Please send C.W.O. to:- packing/postage/carriage free. OPEN ALL DAY SATURDAY QUOTATIONS FOR LARGER QUANTITIES ALL PRICES TAX PAID K.V.A. ELECTRONICS DEXTER & COMPANY (Dept. PE3) 124 Cricklewood 40-41 Monarch Parade, London Rd. 1 ULVER HOUSE, 19 KING STREET IVORYET Broadway, London, N.W.2 Mitcham, Surrey CHESTER CH1 2AHTel. 0244-25883 LIAM IrED Tel. 01-450 4844 Telephone 01.648 4884 As supplied to H.M. Government Departments

188 PracticalElectronics March 1973 IWIRle-fivrampletdiemiamtketorStOrd SPECIAL OFFERS! PLESSEY DITEORATED CIRCUIT INTEGRATED CIRCUITS 8 Watt Ambler SLIOSD Why buy Itrnatives whn you can buy the genuine article from us at SEMI -CONDUCTORS Complete with 8 -page compatitiv prices from stock. BRANDED FROM TEXAS I.T.T FAIR- BFT90 S9p2N2926 10p booklet, circuits CHILD 1000MCIS All Colours and data 25 + 2.0p 25 + 9p 100 + 17p 100 + SP £1.50each 500 + 1Sp 500 + 6P 1000 + 3P TRIACS STUD WITH ACCESSORIES Type 1/11 12/24 25/99 Type 1/11 12/24 26/99 Type 1/11 12/24 25/99 AFI I7 Mullard 2Sp2N3819Texas35P Type VoltaPrice P P P 25 +17p 25 + 30p P.I.V.1-11 8E7400 0.200.18 0.16 13E7450 0.20 OAS 0.10 13E74145 1.50 1.40 180 100 +I Sp 100 + 23p 3 AMP RANGE 8147401 0.20 0.18 0.18 9117451 0.20 0.18 0.10 6E741508.85 2-95 2.15 500 + lip 500 + 20p 8C35 A 100 759 8147402 0.20 0-18 0-16 8E7453 0.20 0.18 0.16 8N741511-10 0.95 0.90 1000 + 15p 8C35B 200 79p 0N7403 0.20 0.18 0.16 BN7454 0.20 0-18 0.16 13/04153 1.85 1.27 1.20 SC35D 400 859 8N7404 0.20 0.18 0.18 8107460 0.20 0.18 0.16 8E741542.00 1.75 1.55 OCI70 Mullard 25 BC107, BC108, 6 AMP WOE (T048) 8N7405 0.20 0.18 0.16 8E7470 0.80 0.27 0.25 8E741551-55 1.47 1.35 25 + lOp BC10910p each 8040A 100 85p 8E7406 0.80 0.27 0.25 8E7472 0.80 0.27 0.25 8E741581.55 1.47 1'86 100 + AllMakes 0040B 200 90p 21E7407 0.80 0.27 0.25 13E7473 lip BC4OD 400 61 00 3 Amp 0.40 0'87 0.85 13E74157 1.80 1.70 1.50 500 + 15p 25 +Op 8E7408 0.20 0.19 0.18 8N7474 0.40 0.87 0.85 13E74180 2.80 2.40 2.25 8C40E 500 SI 20 T048 8E7409 0.45 0.42 0.85 6N7475 0.56 0.52 0.50 8E74181 2-80 2.40 2.25 1000 + 13p 100 + 7p 10 AMP RANGE (10481 8N7410 0.20 0.18 0.10 13E7476 0'45 0.42 0.89 13E74162 3.40 8 26 2.70 500 + 6p 13C45A 100 95p 8N7411 0.23 0'22 0.20 6E7480 0'80 0.75 0.67 8N741638'40 3.25 2.70 1000 + 5p SC458 200 61.0 BN7412 0-42 0.40 0.85 13E7481 1.25 1.15 1 10 6E741042.75 2 30 2-10 BYI27 Mullard 15P 50450 400 61 26 8N7413 0.80 0.27 0.25 8E7482 0.87 0.80 0.70 8E741854.00 8.50 8.0 25 + 12p ADI61, ADI62 3Sp8045E 600 6145 8N7416 0.80 0.27 0.25 8E7483 1.00 0.90 0-85 8E741884.0 8.50 3.00 100 + 10p each 16 AMP RANCE (T048) 8N7417 0.80 0.27 0.25 6/47484 0.90 0.85 0.80 81074167 6 25 5.80 5.10 500 + 9p 25 + 32p EIC50A 100 21 25 8107420 0'20 0-18 0 10 8/47488 0.45 0'41 0 88 13E74170 4.10 8.55 3-05 1000 +Sp 100 + 2.8p BC5OB 200 61 85 807422 0'48 0.44 0.40 9E7490 0.75 0.70 0'65 0E741742.00 1.75 1 80 500 + 25p BC50D 400 81 86 967423 0.48 0.44 0.40 13/47491AN 1-00 0.95 0.90 8E741751.85 1.27 1.15 1000 + 22o SCOOE 600 61 85 8107425 0-48 0'40 0.85 0E7492 0.75 0.70 0.135 8E74178 1.80 1.86 1.20 0A202 10P DIAC D92 259 6E7427 0'42 0.39 0 85 8E7493 0'75 0.70 0'65 8E74177 1.80 1.35 1.20 25 + 2N3053 20o TRIACS- 8E7428 0'50 0.45 0.42 8N7494 0.80 0.76 0 70 81174180 1.55 1.80 1.20 100 + 7p 25 + 18p Add ltbanal Types 13E7430 0 20 0.18 0.16 13E7495 0.80 0'75 0.70 8N741817.00 6.00 5.50 500 + 6p 100 + 15p 40430 (T066) 859 15 Amp 8E7432 0 42 0-89 0.85 8N7496 1.00 0.97 0.95 8E741822.00 1.80 1.130 1000 + Sp 500 + 12p 40669 (Flange) 8117433 0.70 0-81 0'44 6E7497 11.25 5.50 5-00 8E741842.40 2.00 1.80 1000 + 10p I 1048 8E7437 0.65 0.80 0-50 6E741002'50 2-80 2.00 8N74185A 2.40 2 00 1-80 40486 (T05) 690 8107438 0.85 0.80 0'50 13E741041.45 1.85 1.20 0E741901-95 1.85 1.75 0C35 Mullard 50P 2N3055 55p BN7440 0.20 0 18 0.16 8E741051'45 1-85 1.20 8E741911.95 1 86 1.75 25 + 45p 25 + 50p NEW BRIDGE 0E7441 AN 0.75 0.72 0.70 8N741070.50 0.45 0.40 8E741922 00 1.90 1.80 100 + 40p 100 + 45p RECTIFIERS 9E7442 0-75 0'72 0.70 13E74110 0.80 0.70 0.80 13E741932.00 1.90 1.80 500 + 3Sp 500 + 38p BN7443 1.00 0.95 0-90 13E74118 1.00 0.95 0 90 0E741942'50 2'25 1.90 1000 + 30p 1000 + 33p SMALL SIZE AND LOW COST 13147445 2.00 1-75 1.80 81174119 1'90 1.78 1.66 8E741951.85 1.70 1.80 Type VoltaPrice 8E7448 13E74121 0.80 0'55 0.50 8E741981.50 1 40 1.80 P.I.V.1-11 2.00 1'75 1.60 0E741221.35 1.25 1.10 8E741971.50 1.40 1.30 HALF AMP 8E7447 1.75 1.80 1.45 0E741232.70 2.55 2 47 8E741984.60 3-70 3.85 B05/05 50 20p 13E7448 1.75 1.60 1.45 8E74141 1.00 0.95 0-90 8N741994.80 8.70 3.85 ZENER LINEAR B05/10 100 255 PRICES OF 7400 SERIES ARE CALCULATED ON THE TOTAL NUMBER DIODES (0/P AMPS) ONE AIRY Ix IH ORDERED REGARDLESS OF MIX TUBULAR LARGER QUANTITY PRICES PHONE(01) 402 4891 400 M/W 5% 702C TO5 755 B1/05 50 250 TEXASHANDBOOK NO. 2.I.G. 700 PAGES DATA60p. POST 20p. Miniature 7090 T099 851) B1/10 100 259 HIGH POWERSN 74 H001 Now in stock -send BZY 88 Range 7090 D.I.L.36p B1/20 200 SOp LOW POWERSM 74 LOO ffor list No. 36 600 859 All voltages 723C D.I.L.956 ONE AMP (ILL) 3.3 - 33 Volt 7250 T099 6460 TUBULAR A SELECTION OF SEMI -CONDUCTORS FROM STOCK lOp each. 741C TO9965p W005 50 309 23+ 99 741C D.I.L.656 WOl 100 UP AAY80 10p BC147 125 110105 2-25 0C44 155 T1943 65p 2N3055 55p 100+ Sy 747C T099 6110 WO2 200 40p AAY42 155BC169C lop BY100 15p 0045 155 V405A2552N3440 76p 500+ 1165 7470 D.I.L. WO 600 45p AAZ1310P BC182 109 BY12615p 0057 50p ZTX108 1292N34421.25 1000+ 61 10 TWO AERS O II x 4 L AC107 859 BC214155 BY12715p 0071 155 ZTX300 129 2113525 75p 72741P D.I.L.80p AC128 259 BCY32 755BYZ13 35p0072 26p ZTX301 1552N3614 509 Any one type. 72748P D.I.L.605 11205 50 85y AC127 259 BCY34 355 C106D855 0077 46p ZT1302 1852E3615 75p SINCLAIR B2//100 100 40p AC128 25p BCY39 1.000ET111 5550081 25p ZTX341 20p 2N3702 lop 11 Watt 5% 1C12111.80 B2/200 200 45p AC176 259 BCY42 80pGET115 55p 0083 259ZTX500 1552113704 lOp Wire Ends TOSHIBA B2/600 600 50p AC187 259 BCY43 2690ET880 45p0014055pZTX503 179 2N3705 10p MetalCase TH9013P 112/1000 1000 60p AC188 25P BCY55 2.50 1.11309K 0C17025p20301 110y 2N3714 1.80 All voltages 20 WATT AMP FOUR AMPS ACY17 805BCY70 169 1T03)1.87 00171 80p 2N404 209 2513771 1.75 6.8 - 100 Volts 6947 POST PAID OR x x ACY20 20pBCY71 20p MAT121 255 0020046p2/4527 859 2N3773 2.00 20peach TH9014P Pre Amp B4/100 100 60p ACY2120p BCY72 155 MJE340 509 00201 76p 211896 15p 2N3790 2.25 111.50 B4/200 200 65p ACY39 559BCY87 2.99 MJE370 705 0020280p 211697 159 2N3819 359 25+ 18p DATA AND B4/400 400 709 AD140 SOP BCZII505 MJE520 709 00203609 2N706 105 2N3820 50p 100+ lip CIRCUITS REF. B4/600 600 75p AD149 50P BD124 809 MJE2955 OCP71 1,252N930209 2E3886 855 500+ 129 42 109 B4/900 800 110 AD161 851) BD13176p 1.10 ORP12 6052N987 459 2/43903 155 1000+ 1011 SIX AMPS AD162 FREE WITH 85p BD132805 MJE3055 ORP60 40p2111131 269 2113906120 Any one type. x6 AF117 20p BF11525p 75p P3466.209 2111132 25p 2114061 12p PURCHASES B6/100 100 709 AF118 SOP BF167265MPF105 40p RA8310AF 2111302 1892114062 129 B6/200 200 75p AFI2425p BF173269 NKT214 209 459 2111304 2292144126 150 3 Watt Plastic 116/400 400 90p AF13980p BF179805 NKT216 405 15A8508AF 2111305 2292114871 856 Wire Ends 5% TRANSISTORS, B6/600 600 61.0 AF186409 BF180805 NKT217 40p 659 2111307 Shp2115457 305 9EZ Range AF239409 BF194155 NKT403 705 TAA263 759 2N1308 2592N5777 555 IC's, TRIACS, SILICON CONTROLLED ABY27 SOp BF195159 ERT404509 TIL209 89p2N1613 20p 28001 1-00 All voltages B RIDGES, =Tun= A9Y28 259 BP8612590A5 60p TIP29A 505 2111671 1.0028012 10.00 6 - 100 Volta Type Volt.Price BAI02 $09 BF898255°A10 85p TIP30A flOp2112147 75p 28018025 305 each. SCR's, LDR's P.I.V.1.11 BA115 7y BFX13 2590A81 lOp TIP31A 8052242160 509 280268 90 ORE AMP BA145159 0A91 7p TIP32A 70p2112217 269 28301 501, CRS 1/05 50 25p BFX34 755 SILICON BARB 59BFX37 80p0A200 7p TIP33A 2N2221 205 28303 65p misers X159110 CRS 1/10 100 809 BAX16 79 0A202 1.00 2N2222A RECTIFIERS CRS 1/20 200 809 BFX 88 209 105 28324 95p WIRE ENDED BC107lOpBFY50 20p 0C16 759TIP34A 259 40250 SOP CRS 1/40 400 855 BC108 109BFY(I1 2050020 95p 160 2N2369A 40360 406 PLASTIC ORS 1/60 600 459 (1048) BC109 1011 FIFY52 205 0023 85pTIP35 A 15p 40361 40p Type P.I.V.1-11 THREE AMP CRS 3/05 50 110p BC109C 129BFY64 5050025 409 2.502112906 20p 40362 509 1 amp miniature 0028 65pTIP36A 2112926 (all 40408 509 CRS 3/10 100 30p BC119 169BFY90 595 IN4001 50 6 BLY36 8.00 0035 609 cola) lOp 40486 755 IN4002 100 7 CRS 3/20 200 359 BC117 36 400 'Amp 209 BSX20 15p 0036 859 TIP41 A3751 2N3053 205 40636110 I N4003 200 8 CRS 3/40 459 13C143 855 138V27155 0C42 40p TIF42A 85p 2103054 509 40430 1 00 I N4004 400 8 CR8 3/60 600 bhp T05 I N4005 600 10 FIVEANY (10401 INTEGRATED CIRCUIT SOCKETS IN4006 800 12 CR8 5/400 400 609 LOW PROFILE PLATED PINS QUANTITY DISCOUNTS IN40071000 15 NEWFREE SEVER AMP 1T0481 CR8 7/100100 GOD 10",, 12 : 15% 25+ ANY ONE 1.5 amp miniature B OOKLET PL4001 50 8 CR8 7/200 200 659 20% 100 1-: 26% 260+ TYPE CRS 7/400 400 709 PL4002 100 9 (No. 36) CRS 7/600 600 Front above sections except Integrated PL4003 200 10 OVER 1500 969 .Circuits and SpecialOffers where dis- PL4004 400 10 SIXTEEN AMP (16 Leaf' (14Lead (8 Lead count. are included. PL4005 600 12 TYPES - SCR 16/100 100 669 SCR 16/200 200 70p D.I.L.) D.I.L.) D.I.L.) Minimum order value II please. PL4006 800 15 .1, I Icr pure 3 Amp 175 155 155 Footage 7p on all order, 16 SCR 16/400 400 80y P L40071000 0,'R 000,00 .100 11 00 T048 MAIL ORDER DEPT: 303 EDGWARE ROAD, LONDON, W.2. RADIO RETAIL SHOP: 404-406 EDGWARE ROAD. (01-402 8381/2) HENRY'SLIMITEDOpen 6 days a week 9 am -6 pm Monday to Saturday

PracticalElectronics March 1973 189 Go Hi-Fi yourself!Areyoualright New Goodmans Din 20 loudspeaker kit for Jacks? specially designed to give the D.I.Y. enthusiast excellent hi-fi reproduction at

moderate cost Ask for Rendar Jack plugs and sockets at your local This system has been thoroughly tested to stockist. They come in a wide variety of configurations, It will provide extremely and in cases of difficulty can be ordered DIRECT from Goodmans high standards. the Rendar factory. satisfactory listening levels from amplifiers rated at Standard, mini and sub -miniature sizes ... plugs in both 10 watts (per channel, in the case of stereo equipment) screened and unscreened versions...socket bodies in high melting but it may also be operated from amplifiers of point thermoplastic ... several unique features (some protected by UK higher power. and US Patents) ... Post Office and NATO specifications. The kit contains all parts needed to complete the If you want to study all the facts and figures, all the ingenious con- system (except timber and other material for the cabinet struction details, send for the Rendar Electronic Components Catalogue of technical data sheets covering their entire range of products. itself) and has detailed, illustrated assembly The cost of the catalogue is 25p, including P 8 P, and it's money very instructions. well spent I Contents Bass unit 204mm (8in) diameter. RENDAFC Dome HF radiator 25.4mm (tin) diameter. Port tube. Rendar Instruments Ltd., Victoria Road Crossover panel with colour coded leads. Burgess Hill, Sussex.Tel. Burgess Hill 2642-4 Terminal board. Cables: Rendar, Burgess Hill Foam gasket. Input lead complete with DIN plug and spade terminals. Acoustic wadding foam pad. Fixing screws and hardware. Cabinet template (on bottom of box). THOUSANDS FM TUNERNOW IN USE Specification NELSON -JONES Reduced prices 20 watts DIN, 4 ohms impedance, 8in bass unit, Approved parts of this outstanding design (VV.W. April 1971). dome HF radiator, Featuring 0.75/N sensitivity.Mosfet front end.Ceramic I.F. strip.Triple gang tuning, 4V r.m.s. output level, suitable for crossover frequency phase locked decoder, as below. Designer's own P.C.B. 4,000Hz. Tuner parts with box.Less than EI I.50.S.A.E. please for lists. NEW Solid State Tuning Indicator and Dial -Chassis Kit. High Performance Decoder also available. For further details NEW IC Stabilised PSU. SC, overload protected, low ripple. and the name of £3.55 p.p. 19p. your Goodmans dealer, send the coupon now LIGHT EMITTING DIODES (Red) Improved Type panel or PCB mounting with free mounting clip clear or black.Order LEDIA.Please add postage. Monsanto miniature PCB mounting with radial leads.Order LED2. Please add postage. NOW ONLY 3Sp each with connection data. 7 SEGMENT LED DISPLAY 0.325in Characters 0 9 and nine letters. TTL, DTL compatible. ONLY E2.46 each, p.p. ILIP. BCD -7Seg Dec Driver, L1.30. ELECTRONIC CALCULATOR MODEL BC806 Pocket Size Downley Road, Havant, Full 4 Functionwill perform Addition, Subtraction, Multiplication Hampshire. and Division including Chain or Mixed Multiplication or Division as Please send me free well as true credit balance.Constant Key: Fixed or Floating decimal Sound reasoning. leaflets on Constructors' point.Batteries and leather case supplied. equipment and the name of (POST FREE) my Goodmans dealer. PRICE ONLY f4625 Name (Mains adaptor £4450) Address INTEGREX LIMITED, DEPT. P.E. P.O. BOX 45, DERBY DE I ITW. Tel. 0283 89 3580 PE3

190 PracticalElectronics March 1973 ZI1414 £l.25 PAU FORS I Thermistors Potentiometers Capacitors The I.C. Radio in a T018 can. Supplied complete with data sheet No. 10 which Al 5B 75pGL23 £1 '00 VA1 005 15p dine ceramic low voltage contains specification, circuit and details CZ1 15p R53 El -32 VA1 026 13p croif -ot,r18v Sp 0.1pR 30v Sp and prices of components such as ferrite CZ4 13p R54 E1,48 VA1033 13p 022pF 180 Sp 0-22pFflv Sp rods, compression trimmers etc. CZ13A 13p VA1040 10p MI ir.,1 lir 047pF 12v Sp 0.470F 3v Sp E298 ED/A258 rep VA1053 10p ceramic plat* 30V I.C. Sockets 0296 ZZ/06 tap VA1055S 10p 5pil 1003pf 1Sp 4700pf 10p 501112 500K a 22000 10p 10,0000 10p Dual-inline or Zip.Zap (Dud(. 14 and 16 pa GL1 6 Cl VA1034 100 101(11 1001(11 1M!) Our Prise fp per pin 25Kf1 250K SI 2M11 log or lin less switch (& 1Kil lin) 12pp log or lin with switch 24 Slider Pots Resistors dual less swatch 40p Single dual with switch 10K, 100K & 1M Commie - Piste 83V (C333) Dual lov i watt 5% Carbon Film - low noise 1-8pf 82pf 33pf 120pf 10K 10 . (OK or Hi -Stabs log only 52p 10K log 10K antilog less switch 40p 2-201 1001 39pf 15001 25K 25 t 251( All E24 values 1p each plus p. & p. 7p for up 3.3of 12M 47pf 180Pf i to 50 Resistors and a further 2p for each 50K 50+ 50K 3-90 15pf 56pf 220p1 additional 50. Deduct 335% for 100 of one 4 1pf 18pf 270Pf 100K 100 . 100K Knobs 68pf type or 2556 for mixed orders over Cl in value Ellissiostors 500 22pf 82pf 330pf 30p 50p 10p 1 W 10% Carbon Composition 3p each 68pf 27pf 100pf 2 W 10% Carbon Composition 8p each all Sp. each NEW LISTS 2! W 5% Wire wound 9p each LOUDSPEAKERS No. 4 51M Wire wound 9p each mylar film 100V COILS AND INDUCTORS No. $ 10W Wire wound 10p each 1000pf 2p 01 pF 3p 068pF 4p TRANSFORMERS No. $ plus p & o 7p for up to 25 resistors plus 1p 2000pf 2p -020F 3p 1 pF 4p for each additional 25. (postage Si') 5000pf 2p '040F 3p -20F 5p 05pF 3p Diodes 6 Rectifiers , polystyrene 00V sust.. lOpf to 10,000pf in multiples of 10, 15, 22, 33,1 9 volt a/ 20mA (PP3) £1.25 47 6 68. AA1 19 9p BA1 56 15p 131176 E150 EA1000 6 volt ./ 50mA E1.50 AA1 20 9p BA243 56p BY182 E1.50 metallised polyester 250V (C280) t, 9 volt, 50mA £1.50 29 9p0A47 10p BY250 23p 6 6 volt. 50mA E2.50 01 pF30 '0689F 35p .479F BpAA1 69102 25p 0979 9p N40016p 9 9 volt, 50mA £2.50 015pF 30 1 pF 4p680F 11 p BA115 17p 0990 7p N4002 7p 75 volt for cassette recorders £2.00 0229F 3p 158F 4p 19F 13p BA130 10p 0A917p N4003 8p 6. 7i or 9 volt £3.00 033pF 3p -229F 5p 1-50F 20p BA145 20p 0920010p N4004 SP 3. at. 6, 75. 9. 12. 500mA 01104.1 047pF 3p 339F 8}p' 229F 24p -1 £3.99 89148 20p BY100 15p N4005 10p a wan , Car Battery Converter fully stabilised to BA154 13p 511 26 15p 54006 12p Audio provide 6, 75 or 9 volts £4.99 metaRised polyester 400V (C281) 13915514p 13112715p N4007 15P AmI"e' (p. & p 15p on all types) 01 pF 45p .yes 6p 22 pF 10p Our Price inc. handbook -', 015pF 45p ,088pF 6p 33pF 14p 82 - M 022pF 45p 1 pF 7p '47pF 15p 033pF 55p 15pF Bp to less 151, 8 Presets silvered mica 1% (>5110) 500V FM TUNER "' 19" °V. 20p1 7n 100. less 3311. 2.2pf-820p1 Tp lip chose. Nay Vertical or Horizontal 1nF-2,20 Ilp 61300pf--01pF 211p tram...lee2.7nF-36nFo von 5 Watt 01 watt 5p D25 watt 7p 111p operation. Audio 100 1K 12 10K l/ 100K 11 1M 12 mixed dielectric 600V OUR PRICE Amplifier 250 2.5K II 25K 12 250K it -01 pF 7p EI25 2.5M 12 0479F 7p -220F 16p Our Al e 8380 500 5K!1 50K 11 500K 11 5M 12 '0220F 7p 06/30F Sp .47pF 24p 11:11.',"°:':.'rw.::.°7;.-- Less dome*, discount 033pF 7p 1 pF Sp 1 pF 33p

MAIL ORDERS: Where no p. & 0. charge is shown, minimum of 7p applisi, overseas wows is charged at cost ADDRESS TO: M. O. Dt TMT1)\:i[g -Telectronics 54. Fortis Gramm O. don N10 MN. I TIphone 01.883 3705 m ixed Meat Transistors 6 Integrated Circuits 1000pfd 6ieplectric6800pf 9p°0°-1 pF 12p Sinks 2200pf Sp 01 pF 9p 22pF 22p AC107 25p octet tap EIFIN 15p °Cal 19p 261304 112p mitt.: 15p 3300pflip -022pF 9p 470F 30p TO5 I T066 14p AC125 i'fis 13C146 10e BF197 15, OC140 elp 261711 me 132263 1 47000 lip 0470F 12p TO18 T03 , -P AC127 15p BCI49 11/p ORM 53p 0C170 23p 251893 lipawss rep, 5P 411141. 12KV.d.c. IIKV.d.c. HI -K 750V. Power 1., AC128 15pcCeramicBC157 12p BFY50 24p 0C171 30p 262926all100 100511 L1.58 1091 9p 200pf 9p 1 000Pf 5P Tab ''P AC176 15p BC158 10p BFY51 21p ZTX107 15p 2213053 230 1036T1 L1.50 15p1 9p 220pf 9p 1 500pf 5p AC187 25p 9C159 12p BRYN Hp ITX10(1 12p 2713054 500 L03771 LIAO 22pf 9p 250pf 2000pf 5p AC18711 350 BC169 IS p 135X21 Rip ZTX109 lip 263065 Mei 68pf 9p 270pf 9p 3000pf 5p AC188 25p BC2118 150 EIS795A 14p IT0300 t2p 253702 120 9p MC1330 Hp 82pf 300pf 9p 50000 5P 'Ifill ACI881, 25p 8010510201.75 ZTX301 263703 12p 100pf 9p 750V DISC 1 0,000pf 5P KM, 070 rip 210131 70p MJE340 ZTX302 2ip 263704 100 1200 9p 4700 Sp feed- 1.1111' ACY20 20p Pp .C1351 LI.N ,,,,,. ,,,, 1311132 70p SAPF192 419 Z7X303 Hp 253705 10P Op 1000pf Sp through qqq .C13.n.. 150pf 9p 50000 5P Iiili 'ti 1301/254.P MPFI03 3H ITX304 25p 263706 1110 A0149 Hp MFC40008 411, 180pf 9p 10,000pf Sp 1000pf 5p 341 zep 263707 15p MFC4010A 55 :rg} 13F160 7; MIAPPFF1N'05 40nPp 2TT:500 I5p 263708 P ,140pfDIP 10/2 "° Loa.° eta AF114 1Ip 111F167 20p MPF106 45p ZT X501 15p 263709 12p Mullard4 Siemens for 51.403D 5(.4030 21.511 AF115 Illp 137173 Hp OCH lap 210503 28p 253710 12p IOD COp 15p T A11100 21.50 A F116 18p 13F180 Hp OCIS Hp 210503 17p 253711 12p Electrolytics AFtil 18p 111F1111 30p Odd 15p 210504 58p 2143819 asp VOLTAGE Veroboard AF139 2ip I3F184 Hp 0C45 ISp ZTX531 25p 263903 15p AANK RR uCFAP 4 63 to 111 as 40 63 Copperclad Plain BC107 lip 13E185 25p OCT, 11p 26697 tip 253904 lip eA710 Mg - 60 0.15" 0.15" BC106 10p BF194 15p 0072 17p 214706 lap 253905 Hp 0A723C MAI 1.5 Be 22R ep BC109 10p BF195 15p OCM 15p 26706 15p 153906 12p PAMC 21/2" x I" 6p 6p - " 3.3

21/2" x 331" 20p )6p (9) 100 . 4.7 21/2" x $" 240 21p (7) 12p ROTARY SAAJNs II -- 15P OP 41.14.9.1.6 10 -- 6P 111/ 3N" x 3N" 24p 21p (8) - A'-' Caw Is so 6P 011 3.8" x 5" 17p - 27p 27p (10) PI 6p - 6t7 - 61, 17" x 21/2" 670 50p 770 Silittli P187 aglAPArt 33 - Ls - 6p - 0 6p 6p 17" x 331" 90p 70p 52p 25p 47 01/ 011 60 6p 00 17" x 5" 750 Nag 68 - - - 109 100 tip - OP - 6P 6P MP L700 ',74. El .70 pA p, 10p k". .."53;iV C°.' 150 PrO 00 61/ 113P 1213 $potface Cutter 36p i (Flush) - - if/0,, 19 110 6p tfir MP MO 10p 47p 5,60,e) L646 46 El .85 p.6 p. 10p SINGLE WAFE 220 - Pin !Nation Tool , 04,-,_ 50 - 6p 10p - - 21rs Terminal Pins Illip per peek of 36 Bp ROTARY 410 - thr 10p - 12p rep 40p .1...,11 ...... 4, MO -Hp - Ilp Illp 210 NEW LIST S 25p 1000 10p - 12p lep 21p HP HP Coon 1500 - 140 180 21p 1 pole BOXES, CHASSIS, etc.Din (Surface 12 way 2200 - ispzip sop HP RIP 93P TRANSISTORS, IC's, etc. Socket 3 pole 4 way 3300 - Shp 4 pole 2 wey 4700 21p -- KV MP 11150 -I3P ( Post -toe 5p) 4 pole 3.qI CAP VOLTAGE 16 25 40 64 PR nom - - SLIDE --- MP HP 01/essioiox Roses Plug -rseee,--IL ' 500 Including baseplate and screws c D. P. D T 1250 Hp - 5, Din "'"?'r 1000 75P 17p 40P 50P No. L. W. D. Price p. & p. Sacker Insulated 2000 - 2500 - 750 030 A, llosC TERMINALS - 3200 HP --- (7) 2-8" x $14" x 155" 35p Sp sa 75p 03P 13p each TOGGLE 40110 (8)0" x4"x DV 350 Bp 6400 MP HP - Laudrpealrer elks 4rem plug A S. P. S T Ouentily Pnc. on application. (9)4"x 23i" x 11/2" 350 Bp 250V.I A P1i0 Available In Red, Black, Green,S17,,I1 5.11147 0611.07 (10) 4"x $%" x 11/2" 40p Bp 18p While, Yellow, Blue and Grey Contains 12 A. of coiled 11 4"x 21/2" x 2" 35p Sp 18 s.w.g. Erato Multi- IIIlfolt Electrolytics 12 3"x 2"x I" 32p 9p 4 eachsort HAI. Alloy. TOGGLE 1: 2. 4. Bpi 4500 lip 32nr 4501 100 13 6"x 4"x 2" 50p 10p 18p D.P.D.T. 1130F 4500 15p500i 350020p 14 7" 0 21/2" Loudspeaker each 250V. x 5" 58p 12p I A 8 80, 450 V.W . lip32 , 32of , 350 11.W25p 6,, 4wes. PLUG.Stsciroble same 15 8"x 6"5 3" 75p 18p lap 8 HO, 450 VW 20p 32 320- 450 V.W43p 10p "'II... i ...me Ceel m 16 10" x 7"x 3" 85p 20p tere(nals. 16 11114, 450 V.11 25p 5050pi 350 VW 350

PracticalElectronics March1973 191 USED EXTENSIVELY BY GOVERNMENT DEPARTMENTS, INDUSTRY, EDUCATIONAL AUTHORITIES, ETC. LOW COST QUICK DELIVERY OVER 200 1-1 --1.71 PAEJELMETER RANGES IN STOCK OTHER RANGES TO ORDER CLEAR PLASTIC PANEL METERS " SEW " BAKELITE 4 :in. x Fronts Type MR.88P. 1 21/32in. square Fronts. PANEL METERS TYPE SW.100100mm r 80mm Fronts Type MR.85P. Type MR.85. 3lin. square Fronts. 30µA 13.80 30mA £3.10 -...---.. 21.76 50-0,50µA /3.80 100mA tR10 2301/rini'.A1. 111.75 1 amp. .... 12.15 100µA 19.80 300mA £8.10 300mA 1146 3 amp. 12.15 100-0-100µA 13.70 1 amp. E.3.10 ,''''''''''IqA8,, V 750mA i176 15 amp 1215 o amp 13.10 1 amp ia..75 30 amp £2.15 500µA 13.50 32.15 13.40 15 amp. 2840 Ir.:I' .., ,177: 2 amp. 21.75 30 amp.... 5 amp 3V d.c. £2.15 20V d.c. 13.40 30 amp. 13.20 ..41t. 30V d.c. £3.405 amp. d.c...£3.40 201, £3.10 10 amp. 1911:7755 10V d.c. £215 300V d.c. £3.40300V ax. 63.40 30V d.c. £310 9V d.c. 11.75 20V d.c. 2215 1 amp. d.c £3.40VI" Meter . 34.1530pA 13451504' d.c. £.3.10 30µA 1240 10% d.c.....£1.76 30V d.c. 12.15 50-0-30pA.. 23.40300V d.c. 111.10 50-0-30µA IMO 15V d.c.....31.75 130V d.c. . 12.15 100µA £3.4013V a.c. 1240 20V d.c. . ..21.76 300V d.c. 32.15 Type 8D.830 82.6mm x 110mm Fronts 100-0-100µA 2340300V a.c. 1133..1001101-0-A 100pA £1.96 30V d.c.....21.75 13445 30nIV d.c.. 22.40 200µA 13.308 Meter lmA 13.15 E1.96100V d.c. . 21.76 13.00100mV d.c. 32.40 . 10mA 1240 . £2.20 300µA 11.80ALSO 150V d.c. 11.75 30V s.c. 30mA 1240300µA 18.20VU Meter ... 50-0-50µA 12410 500-0-300µA E8.101 amp. a.c. 43.10500-0-500µA. £1.76 300V d.c....11146100µA £2.6050V a.c. . £2.20 100mA £2.50 1mA £2.20 lmA £8.10 aamp. a.c. . 23.10 £1.75 500V d.c....£1.75100-0-100µA 12410 130V a.c. 300n,A 1240 1-0-1mA £1.75 750V d.c....11.76 300V a.c. t2.20 1 amp. 1.2.601-0-1m A. 28.1010 amp. a.c 23.10 300µA 22.45 3111A 134020 amp. ax.. 43402mA £1.7613V a.c.... .1146500-0-500pA £2.15300mA a.c. £215 3 amp. £2.50 3mA 21.76 50V a.c.... .1146 1 amp. ax. 12.15 10 amp 1240lOmA 12.1030 amp. ax. ..f.R10 1mA £8.15 10mA 11.75130V a.c. . . 11.915 3 amp. a.c. £215 3011A 62.75 3V d.c. £2.50 1!.-0-1A111.4 1245 20mA 11.76 300V a.c. . . 2146 22.1510 amp. a.c. 42.15 50-0-30µA... 12.7010V d.c. . 1240 £1.75 500V a.c. 20 amp. a.c. 22.15 £2.70 20V .1.c. 18.60Type MR.62P.Cin. square Fronts. 30mA 2141510mA 12.15 100µA 100n1A £1.758 Meter lmA. 11415 124530 amp. a.c.2245 100-0-100µA12.70 30V d.c... £2.5030µA 18.40IOV d.c. . E820150mA 11.75 VU Meter ...12410 30 amp. a.c. 3.215 E6.70 300V d.c. UM30 0 30µA. 1245 20V d.c. tR20 r1404tAtA 1245 200µA 82.15VU Meter .. 1340 300µA £2.55hiv a,. 12.75100µA 112.115 30V d.c. IR20 500mA 1246100-0 100µA£2.75 300V d.c....AR20 1mA 22.50 300V a.c. Type MR.45P. tin. square Fronts. Type 8-80 80mm square Fronts 3mA 62.50VI' Meter . 13.003043µA 15V a.c..... 1240 1mA 112.20300V a.c....12.3030µA 12.505 amp /1415aciAA 13.50 3mA 12.208 Meter IniA. 22-3030-0-30ttA .. 1240 10V :I.e. 114550-0-50pA 23.40 Type 8D.640 63.5mm x 86mm Fronts 10n, 4 12.20 VU Meter 13.50100µA £2.30 20V d.c. 21.85100pA £8.40 100-0-100µA 12.05 50V d.c. /1413 30µA 12.60 300mA £2.8530mA 12.801 amp. a.c... 42.20 100-0-100pAISM 200p-1 300V d.c. . £1.85 30-0-30ttA .. 12.551 amp. UM100mA 12.805 amp. a.c... 42.20 12.05 300pA 141.05 300mA 112.2010 amp. a.c.. 42.2030010A 1111.95 13V .e. £2.00110.4 68.85 100µ.1 E2.553 amp 12.35 500-0-300pA 11.85300V a.c. 12.00 100-0-100µA. E8.5510 amp £2.85I amp. 12-20 20 amp. ax.. 42.20 ... 3 amp. 1D21130 amp. we.. Z2.20InIA 11.86S Meter IniA .£2.0550%. d.c. £2.85 200pA S855 3Vd.c. 1246 5mA 11415 VU Meter ...12 50 . 300V .1.c....1245 300µA 1245 20V d.c. E2 36 lOmA 11.861 amp. a.c. 11.85 1mA I8.3530V the. . t2.315 30mA 11.855 amp. a.e... 4145amp. d.c. 1245300V a.c. . 12.86 . Type gmegp. nin. x 81in. Freida 3mA 9315 300V d.c. I835 100mA 11.8610 amp. a.c.. '11.855 amp. .1 e. £2.85 V1- Meter /8.70 . 1240 10mA 18.3513V a.c. £2.40:CµA 13.70 300mA 21.8520 amp. a.c.. .11.85 . £2.40 £3.00 20V d.c. 12.40 SOmA £2.35300V ax. 30-0-50µA .... 1 amp. 11.8530 amp. a.c.. 41.85"SEW" EDUCATIONAL 100mA 12.35VI' Meter . £2 70100µA £3.00 30V d.c.....£.2.40 100-0-100µA£2.90 150V d.c.... 1240 METERS 22-40 200,AA 42.90 300V d.c.... Type ED.107. Size Type SD.480 48mm x 59.5mm Fronts 300pA £2.8615V a.c.....£2.56 overall 100mm t< 90mm 30µA E8.40I amp. 1245500-0-300pA£2.40 50V a.c.....12.55 x 108mm. 50-0-30µA... E2.353 amp 12.15ImA 130V a.c....f2.55 A new rangeofhigh 12.3510 amp £2.155mA £240 300V a.c....42.55 100µA quality moving coil 100-0-100µA. 12.35 3V .1.c. £2.1510mA ER40 300V a.c....12.55 instruments ideal 30mA tR40 8 Meter IniA.£2.80 300I4A 10V .1.c. 42.15 43.70 for school experi A £2.2020V d.c. £2.15100mA E840 VU Meter ... menu and other 300mA £840 50mA a.c. ... 42.40 £2.1530V d.c. £2.15 ER40 100mA ax. .. '12.40 bench applications. 3inA £2.15 1 amp 31n.mirrorscale.The 300V ii.e. . E8.16 E840 200mA ax. .. 22.40 " SEW " lOntA 12.15 12.30 meter mot ement iseasilyaccessibleto 131 a.c. . 30mA 2.2.15 10a an'tipm 1240 500mA a.c. '92.40 demonstrateinternalworking.Available 100mA £2.15300V a.c. . 12.30IS amp. tR40I amp. a.c. 22.40 EDGEWISE METERS In the following ranges: 300mA 12.15VI' Meter. £2.5520 amp fR405 amp. a.c. 92.40 30 amp. E85510 amp. a.c.'9840TypePE.70. 3 171021n. x 1 15/321n. x50pA 25.5010V d.c. 1446 .i0 amp. tR75 20 amp. Ac.. 42-10 211n. deep. 100µA 65.1020V d.c. 1440 mA £4.85 30V d.c. 5V d.c. 224030 amp. a.'-.12.4050µA 23.40 500µA 11845 1445 *MOVING IRON - 30-0-30µA.. £R11.2 50-0-50µA. tb.10300V d.c. 100µ2 112.701-0-1mA Dual range ALL OTHERS MOVING COILSendforIllustratedbrochureon SEW100-0-1000A. £3.20ilk' 300V a.c. A d.c. 14.85300mA/5A d.c. 66.10 Please add postage Panel Meters- discounts for quantities. 200µA 6340 VU Meter...t314:77505A d.c. 14.855V/50V d e. £5.10

LB4 TRANSISTOR TESTER 240° Wide Angle lmA Meters Testa PNP or NPN transistors. MW1-6 60mm square 15417 Audio Indication.Operates POWER RHEOSTATS MW1-8 80mm square 14.97 on two 1.3V batteries. High quality ceramic construction.Windings embedded is vitreous Post extra Complete with all instructions, enan- ' 11,avy dm) "rush wiper. stinnous rating.Wio, range etc. es -stock.',Mete bole fixing, :'a. dia. ohatt,. .,,,s"titles avalla.ts. 4440. Post 20p. 26 WATT. Iiii,3r.0/100/250/3tn,,,, or 504.0. Am:4,90p. P.P. 73p. RP214 REGULATED POWER SUPPLY W.. 7T '..1/701, .100/250/Z'.'0,1000/2..0 ..:.. 300 ohm.:. (1.16.P. & P. p 100 WATT.I /3/11.1/u.nst, ,w/ 230/,m../1000 or 2300 ohms. £1.85.P. & P. 7Ip. Solid state.Variable output 0-24V d.c. upUM TRANSISTOR TESTIS toI amp.Dual scale meter to monitor voltage and current.Tests ICO andB. "YAMABISHI" VARIABLE VOLTAGE TRANSFORMERS Input 220/240V a.c.Pny/npn. Operates from Excellent quality.Low price.Immediate delivery Size183 x 83 X9V battery. Complete II -280 General Purpose Bench Mounting 8-280 Panel Monuthig 105mm.28.97 with all instructions, etc. I amp. 17.00 1 amp .... 17.00 Post 25p. 13.96.Post 20p. 2 3 amp. 98.05 RS amp 18415 5 amp. £11.75 Please addpostage 8 amp. 115.90 ALL MODELS PS.800 REGULATED PAU. MCA -220 AUTOMATIC 10 amp. 222.60 INPUT 230V 50/60 CYCLES Solid elate. Variable outputVOLTAGE 12 amp. £28.60 OUTPUT VARIABLE 0-260 STABILISER 20 amp. 149.00 VOLTS. 5-20V d.c. up to 2 amp. 93 amp. 158.00 Independent meterstoInput 88-125V a.c. or 40 amp. 182410 special discounts for quantity monitor voltage and cur-176-250V a.c.Output 120V rent. Output 220/240V.a.c.or240Va.c. 200VA a.c.Size711n. x 52in. xrating.211.97. Poet 50p. AUTO TRANSFORMERS AVOMETER 31in. 114.97. Post 25p. 0/113/230V.Step up or step down.Fully MOVEMENTS shrouded. P0.10005 REGULATED 80W 32.10P. & P. 18p POWER SUPPLY 130W £2.70P. & P. 18p 300W A8.80P. & P. 23p Solid state.Output 8, 9 SEND S.A.E. FOR LIST OF 500W £5.26P. & P. 33p orI2Vd.c.upto3 SEMICONDUCTORS AND 1000W 1740P. & P. 38p amps. Meter to monitor 1500W £10.20P. & P. 43p current. Input 220/240V VALVES 2250W 11745P. & P. 30p Ac. Else 4In. x 331n. X 3000W 935.00P. & P. £1 Slin. 21147. Post 25p. 230 VOLT A.C. SO CYCLES 830V/240,/ SMITHS SYNCHRONOUS G. W. SMITH RELAYS GEARED MOTORS & CO. (RADIO) LTD. Built in gearbox.All brand Brandnew. 3 set:, of Also see next three pages changeovercontactsatSpare movements for Model 8 or 9.(Fittednew and boxed.30 RPH 3 amp. rating.50p each.with Model 9 scale) or basis for any multiCW; 2 RPH CW; 20 RPM Post10p (100lots1401 CW; 2 RPH ACW; 30 RRH meter. Brand New and Boxed. CW. 30p each, Post 12p. Quantit les available. £350Post 23p. 192 PracticalElectronics March1973 MULTIMETERS forEVERY purpose! Selected TEST EQUIPMENT

IIWM POCKET ROUND SCALE TYPE PENCIL TESTERFTC -401 TRANSISTOR TESTER TE-16A Transistorised NULTIMETER MODEL T8.68 Fullcapabilitiesformea- Signal Generator. 5 ran- High-precielon at low -coat. Completelyportable, simplesuring A, 11 and ICO. ges 400k Hz -30MHz. An Ranges: D.c. 15V, 150", touse pocket sizedteeter.;wit or pop.Equally adapt- inexpensiveinstrument 1,000V (10,000 O.P.V.). A.c. Ranges 0/3/30/300V a.c.ableforcheckingdiodes. for the handyman. at2,000O.P.V.Suppliedcomplete with in- Operates on 9W battery. I5V, 150V, 100V 11,000 andd.c. Wide easy to read scale. O.P.V.). Resistance 0.20K ohms.structions, battery and leads. D.c. Current 150,oA.Resis- ONLY 21.97, Post 13p. 1740.Post 20p. 800kHz modulation. tance 100k ohms. 51,in x 5:in X 3lin. Post 15p. Complete with instruc- 21.65. LT 601 MULTI - tions and leads.17.97.Post 25p. METER Model S -100TH MULTIII/TER/ T R AUDITOR TRANSISTORISED L.C.R. A.C. MODEL 1092Testmeter. New style20,000 TESTER. 100,000 O.P.V. O.P.V. pocket mirror scale/overload protec- MEASURING BRIDGE 5,000 O.P.V. multimeter. 5/25/ A new portable 0/3/15/150/300/1,200V d.c. 50/250 / 500 / 2,500V tion.0/0.12/06/3/12/30/120/ bridge offering en 0/6/30/300/600V a.c. d.c.10/50/100/500/ 600V d.c. 0/6/30/120/600V a.c. cellentrangeand 0/300µA/300MA 1,000V s.c.50µA/ 0 / 12 /1300/zA / 12 / 300mA / 12 accuracyat low 0/10K/1 meg 0 amp. d.c. 0/10 K/1 MEG/100 250A. 6K/6 meg ohms. -20 to +22 dB.MEG. -20 to +50dB. 0.01-2 cost. Ranges:R. Decibels -10 to +16 dB 83.75.Post 20p. Ia-11.1 mega 18.75 each. Poet 15p. MFD. Transistor tester Ranges 1%. measures Alpha,beta and 6 L.1 µH -- 1 1 1 MODEL TH-12 Ico. Complete with batteries. HENRYS 6 Ranges -2%. C. 10pF -i. 1 1 1 0 HIOKI MODEL 7201 20,000 O.P.V.Overload pro-instructions and leads. 20,000 O.P.V. tection.Slide switch selector. mFd.6 Ranges 2%. TURNS RATIO Overload protection 11860.Poet 23p. 1:1/1000-1:11100.6 Ranges 1%. Bridge 0/B25/2.5/10 / 50 / 250 / 1,000V Operated from 9V 5/25/100/500/1,000V d.c. d.c.0/10/30/250/1,000V a.c. voltage at1,000cps. 10/50/250/1,000V a.c. 0/50/zA/25/250mA rt., 003K/ 100µA. Meter indication.Attractive 2 tone 50µA/250mA.20K/2meg. MODEL 449A IN metal case.Size 7: in x .sin x 21n.ISO. 30K/300K/3meg. -20to Post 23p. ohm. -5 to +62411. +50411. CIRCUIT TRANSIS- 2447. Post 15p. 2447.Post 15p. TOR TESTER MODEL TE16 GRID DIP Checks true a.c. betaMETER MOH' MODEL 7301 MODEL TN -800. 30,000 in/out.Checks lcbo.Transistorised. Operates O.P.V.Mirror scale,overload Checks diodes in/out.asGridDip,Oscillator, 30,000 O.P.V. Overload pro- Checks SCR, etc.AbsorptionWaveMeter tection. 6/30/60/300/600/ protection 0/06/3/15/60/300/ 1,200V d.c. 0/6/30/120/600/ Beta HI 10-500 andOscillatingDetector. 1,200V 11.e.12/60/120/600/ LO 2-30 Frequency range 44001.- 1,200Va.c.60µA/30mA/ 1,200V a.c. 0/30µA/6mA/ 60mA/300mA/600mA. 0/8K / cbo 0-5000p.A. 280MHz in 6 coils. 500/AA 300 mA. 2K/200K/2 meg- 801C/800K/8 meg. ohm -20 to 220/240V ac. operation.217.50.Post 25p.meter.9V battery opera- ohm. -10 to +63 dB. -63dB. 25.97. Post 15p. tion. Size 160mm x SOnint 2680. Poet 15p. X 4Ortitn. 21240.Poet 20p. MODEL PL436 TE-200 RF SIGNAL GENERATOR MODEL TE-12 BELCO AF -5A SOLID STATE SINE 20k 0 /Vd.c.8k 0/V Accurate wide range sig- 20,000 O.P.V. 0/06/6/30/120/ nal generator covering SQUARE WAVE C.R. OSCILLATOR a.c.Mirror scale. Sine 18-200,000 Hs: 600/1,200/3,000/6,000V d.c. 0.6/3/12/30 /120 / 600V 120 kHz -300MHz on 0/6/30/120/600/1,200V a.c. 6bands. Directlycali- Square 18.50,000 d.c. 3/30/120/600V . 0/60µA/6/90/600mA. 0/6K/ bratedVariable R.F. at- II z. Output max. a.c. 50/600µA/60/ +10dB (10 K ohms/ 600K/13Meg./60 Meg.050pF. 600mA. 10/100K/ tenuator,audiooutput, <7, socketforcalibra- _ Operationinternal 0-2mFd. 25.97. Post 17p. 1 Meg/10 Mega. Xtal tion. 2.20/240V a.c. Brand 41, batteries. Attrac- -20 to +46dB. 26.97, Post 12p. t tve 2 -tone case 20,000O.P.V. new with instructions. 215. MODEL TE-200 Carr. 37p.Size 140ntni x 7/in X Sin X _in. Mirrorscale,overloadprotec- 215mm x 170mm. Price 137.50.Carr. tion. 0/5/25/125/1,000V d.c. TIM MODEL TW-60K 46 17p. 0/10/50/250/1,000Va.c.0/50/IA/ ranges,mirrorscale,56K/V 250mA. 0/60K/6 meg 0. -20 to d.c.5K/Va.c.D.c.:Volts MODEL MG -100 +62dB. 28.96. Poet 15p. 0i25.025,222,20,5,10,25,50. SINE SQUARE 125,250,500,1,000V.A.c.MODEL L-65 FET WAVE AUDIO Volts: 1.5, 3, 5, 10, 25, 50, 125,V.O.M. GENERATOR MODEL 600 30,000 O.P.V. Inputimpedance 10 with overload protection 250, 500, 1,000V. D.c. Current: Range 19.220,000 25, 50/AA, 2.5,5, 25. 50, 250,meg of . 0/03/1.2/6/ Hz. Sine Wave mirror scale0/0.5/2.5/10/25/ 30/120/600V d.c. 0/3/12/ 100/230/300/1,000V d.c. 500mA, 5, 10 amp.Resistance: 19 - 100,000Hz. 10K, 100K, 1 MEG, 10 MEG 0.60/120/600V a.c. 0/120µA Square Wave. Out- 0/255/10/25/100/250/500/ /120mA d.c. 0/1K/100K/ 1,000V a.c.0/50µA/5/50/ Decibels: -20 to +81.5 4113. put Sine or Square 28.50. Poet 17p. 10 meg/100 meg ohms. wave 10V. P. to I'.Size 180mm x 90mm x 500mA. 12 amp. d.c. 215.97.Post 23p. 0/60/K/6Meg./60 Megtl. 90mm. Operation 220/240W a.c. 2847. Post paid. MODEL 217.50.Post 97p. K228A MODEL AT201 HIOKI MODEL -760X Taut band CI -5 PULSE OSCILLO- DECADE 50,000 O.P.V. auspension. SCOPE ATTENUATOR 43 ranges 0-0.3 to 1,200V d.c. Overload pro- For display of pulsed and Frequency range 0.3 to 1,200V a.c. tection. periodicwaveformsin 0.200kHz. 0-30/2A/300mA. Polarity re- electronic eircults.VERT. Attenuator 0-111.1 B, 0-3K/30 meg ohms.-10 to versing switch. AMP. Bandwidth 10MHz. 0.1dB step. +17dB. 30,000 O.Y.V. Sensitivityat100kHz Impedance 600 28.97.Post 20p. 0/0.5 / / 15 / V RMS/mm. 0I-25; ohm. Max. input power 301113m. 50/250/500/1,000/2,500V d.c. 0/15/50/150/ HOE. AMP. BandwidthSize 180111m x 90mm x 55mm. 500/1,000Va.c. 0/50µA/5/50/150/500mA/ 500kHz. Sensitivity at Post 37P. HT100B4 MULTI -METER 5A d.e. 0/3K/300K/3meg. 28.95.Post 20p. 21860. Feature. s.c. current 100kHz. V RMS/mm. 0 3-25; Pre-set triggered sweep 1-3,000/zsec.; TE-65 VALVE VOLTMETER ranges. 100,000 O.P.V. 28ranges. D.c.volts Mirror Scale, Overload HIDE! MODEL 7001 free running 20-200,000Hz In nine ranges. x 360ininx 1.5-1,500V ac.volts protection. 100,000 O.P.V. Or erloadCalibrator pips.220mnt 1.5-1,500V. Resistance 0/0.5/2.13/ 10 / 50 / 230 / 300 / protection. Mirror orate.430mm. 115-230V a.c. operation. op to1,000 megohms. 1,000V d.c. 0.3/0.6/1.2/1.5/3/6/12/30/60/ 129.Carr paid. 200/240Va.c. opera- 0/2.5/10/50/250/500/ 1,000V 120/300/600/1,200V 11.c. with 15/3/6/12/30/60/150/300/ tion. Complete a.c. TO -3 PORTABLE OSCILLOSCOPE probe and instructions. 0/10/250µA/2.5/25/250MA/ 600/1,200V a.c. 217.60. Poet 30p. 10 amp. d.c. 15/30µA/3/6/30/60/150/300mA Additional probes avail- 10 amp. a.c. 0/2010200K /2MEG/20 MEG. 6/12amp.tl.c.2K/200K/ Sin tube, Y amp. Sensitivity BlV p-p/CM.Bandwidth able: R.F.28.12; H.V. -20 +62dB. 112.60. Post 25p. 2 Meg/20 Meg ohm -20 to 22.50. +6341111850. Post 20p. 1.5cps-1-5MHz. Input imp. .2 meg025pF X amp. MODEL U4511 SUB -STANDARD 870 WYE MULTHIETER sensitivity 0.9V.p-p/CM. Features s.c. current MODEL C-7080 EN MULTI -RANGE VOLT AMMETER Giant gin mirror scale. Bandwidth 1.5cps-800kHz. Sensitivity330 ohms/Volt ranges. 20,000 O.P.Y. Input imp.2 meg 0 20pF. a.c. and it.c.Accuracy 0.5% 0/0.15/ 2.5 / 10 / 50 / 250/500/ 20,000 O.P.V. 0/0.25/1/2.5/10/50/250/ Time base.5 ranges 10cp.- il.e. 1% a.c.Seale length 1,000V d.c. 300kHz. Synchronisation. 163mm. 0/2.5/10/20/200/500/1,000% 1,000/5,000V d.c. 0/2.5/10 /50/250/1,000/5,000V s.c.Internal/external.Illuminated scale 140mm 0/300/750µA/ 1.3/3/7-3/13/30/ x 215nott x 330mm.Weight 1511b. 220/ 75/130/300/730mA/1.5/3/7.5 0/50µA/1/10/ 100mA / 1 / 10 0/50µA/1/10/100/500mA/ 10 amp. d.c. 0/2K/200K/240V a.c.Supplied brand new with hand- amp. d.c. 0/3/7.5/15/30/75/160/ amp. d.c. book.240.00.Carr. 50p. 300 / 750mA 11.5 / 3 / 7.5 a.c. 20 meg. 0/100mA/1/10amp. -20 to +504 B. snip. a.c. 0/75/150/300/ 9/5K / 50K / 500K / 5115EG / 50MEG 730mV/1.5/3/7-5/15/30/ -20 +62dB. 216. Post 25p. 21895.Post 35p. 75/150/300/750V d.c. 0/ RUSSIAN CI -16 DOUBLE BEAM 750mW/1.5/3/7.5/15/30/ Ri79SIAN 22 RANGE MULTIMETER U4312 MULTI:METER OSCILLOSCOPE 75/150/3001750V a.c. Model U43710,000O.P.V. Extremely sturdy Instrument 5MHz Pass Band. Sep- Automatic cut out. Sup- Afirstclassversatilein - forgeneralelectricaluse arate Yl and Y2 plied complete with test leads, manual and Instrument manufactured in 867 O.P.V. amplifiers.Rectangular test certificate..149.Post 50p. U.S.S.R.tothe highest 0/03/1.5/75/30/60/150/300/ -in X 4inC.R.T.Cali- standard..Ranges: 2.5/10/ 600/900V d.c. and 75mV. brated triggered sweep 50/250/500/1,000Vd.c.2.0/ 0/0.3/1.5/7.5/30/60/150/300/ from0.2u/secto100 10/50/250/500/1,000V a.c. 600/900V s.c. milli -sec per cm.Free D.c.current 100wA/1/10/ 0/30013A/1.5/6/15/60/150 running timebase50 G. W. SMITH 100mA/1A. Resistance 600MA/1.5/6 amp. d.c. Hs-1MHs. Built-in & CO. (RADIO) LTD. 300 ohms/3/30/300K/3m 0. 0/1.5/6/15/60/150/600MA/ time base calibrator and Complete with batteries, 1.5/6 amp. s.c. 0/200 0 /3k/30k 0 .Accuracyamplitude calibrator. Also see opposite page test leads,instructions and Knife edge pointer, mirror scale.CompleteSupplied complete with and next two pages sturdysteelcarryingcase. with eturdy metal carrying case, leads andallaccessoriesandinstruction OUR PRICE 45.97. Poet 25p. instructions. 1340. Poet 25p. 287.Carr. paid.

PracticalElectronics March 1973 193 AKAI BARGAINS

U1111-110 RECEIVER SUPER MONEY List Price 12-98SAVING OFFERS -BUY OUR 4 Bands covering 550kHz-30MHz. BFO. PRICE 1.80NOW WHILE STOCKS LAST! Built -In Speaker 220/240V a.c. Brand new Y. & P. 10p. with instructions. 1111675. Carr. 37p. SINCLAIR EQUIPMENT ALL BRAND NEW AND Project 60 -- ^"2, Package FULLY GUARANTEED offers. 2x Z30 amplifier, stereo 60 pre -amp, PZ51721 Tape Rec. 273-95 power supply. 61696. Carr. 37p. Or withX5000 Tape Rec. . 299.95 PZ6 powersupply.11600.Carr.97p.0X370 Tape Deck .. 4259.95 x Z50 amplifier, stereo 60 pre -amp, PZ84000D8 Tape Deck L73.95 GXC40 Cassette Rec. /82.26 .. 1641-96 power supply. 112015. Carr. 37p. 40001)8 Dust Cover . 1975GXC4OD Cassette Deck Transformer for PZ8. 1E97 extra. X201D Tape Deck . 213295 GXC4OT Cassette/Receiver /128.95 Add to any of the above 1945 for activeX221D Tape Deck .. 1169.96 GXC43D Cassette Deck .. 189.95 UR-1A SOLID STATE COMMUNICATION GXC46D Cassette Deck .. 1105.50 RECEIVER filter unit and 113 00 for pair of Q10 speakers. GX220D Tape Deck 1148.50 All other Sinclair products in stock. 0X280D Tape Deck 1249.40GXC46 Cassette Recorder .. 1117.60 4 Bands covering 5501(113-30MH z.FET.2000 amp. 181.95.Carr. 37p.; 3000 amp.X1810D Tape/8 track Deck 2169.96 GXC6OD Cassette Deck .. 2111.26 Meter. Variable BFO for NB, Built-in168.50. Carr. 37p.: Neoteric Amp. 14395.GX1900D Tape/Case. Deck 1177.96GXC65D Cassette Deck .. /11026 Speaker, Bandspread, Sensitivity Control.Carr. 97p. 1C12. 11110. P. & P. 10p. X200081) Tape/Cas/8 Rec... 1223.80C835D Cassette Deck 26940 220/240V a.c. or 12V d.c. l2tinx4t in x 71n.NEW PROJECT 605-82097. Carr. 37p.CR8ODS8 8 track.. 212240AA6300 Receiver /8260 Brand new with instruction.. M. Care. 37p. CR81 8 track Rec... 280.95 AA8030 Receiver 1111 60 CR81D 8 track Rec. /65.95AA8080 Receiver 1144.96 CR81T 8 track/Receiver.. 1118.90.4A8500 Receiver WHARFEDALE YID -RANGE III -PI UNITS Carriage 50p extra (recorders and deck. 75p1. ELWOOD CX208 COMMUNICATION As used in world famous CR8088 8 track system .. 1146-00 RECEIVER system.Sindia.Impedance Carriage 30p extra (recorders and decks 75p). 4/8 ohms. High fluxceramic magnet. 20W RMS. Brand new 1150. Carr. 371, GENUINE BARGAIN! DOLBYSYSTEM NOISE KOSS SP.SEC REDUCTION UNIT STEREO SPECIAL OFFER! HEADPHONES Response GOODMANS 10-15,000Hz. linprov, the performance of cassette and AXIOM 301 Impedance 4-6 ohms. senilltrufessional recorders. Reduces tape hiss Solid state. Coverage on 3 bands 200-420Hi-Fi 121n .20W twin cone full Brand new. by SIB at 00011s, 11dB at 120011. and 10,10 kHz and 055 to 90MHz. Illuminated eliderange speaker. 30-16,000Hz. Boxed and fully g'teed for all frequencies above 3000Hs. Controls for rule dial. Bandspread. Aerial tuning. BFO,16,500 gauss. 8 ohm imped- (List 49-30). OUR Input levels and noise reduct Ion on record and AVC, ANL, "8" meter. AM/CW/88B. Inte-ance. Brand new and boxed. PRICE 16-50. replay. 2 meters for Dolby level. Off tape grated speaker and phone socket. Operation(Listprice021.72).OUR Poet 25p. monitoring. Frequency response: 20Hz to 220/240V a.c. or I2V d.c. Blue 325 x 266 X 150PRICE 11240 each. Carr. 50p. 1,1619kHz -3:8111.Size13Iin X mm. Complete with instructions and circuit. 1021 STEREO 9in X 311n. A.c. 200/230V. 118.50. Carr. 50p. LISTENING OUR HA -I0 STEREO STATION PRICE E32.50 Carr. 30p. HEADPHONE For balancing and AMPLIFIER gainselection of BORDEN DUO -SO STEREO HEADPHONES LATAYE'PrE HA -600 SOLID STATE loudspeakerswith Wonderful value RECEIVER Allsilicontrans- lator amplifier oper- additionalfacility and excellent per- General coverage ates from magnetic, for stereo headphone formance combined. 150-400kHz, 550ceramic or tuner inputs with twin stereo switching.2gain Adjustable head - kHz-30MHz. FETheadphone outputs and separate volumecontrols, speaker on -off slide switch, stereo hand. 8 ohniini- front end. 2 mech.controls for each channel. Operates from 9Vheadphonesocket,.. bin x 4102.11n. 1225. !mdance. 20-12,000 filters, productbattery. Inputs SMU/100MU. Output 50MW.Post 13p. cps.Completewith detector, variable1997. Post 13p. lead and plug. ,BFO,noiselimi- MP7 MIXER PREAMPLIFIER ONLY 1247. ter. 8 Meter. Bandspread. RF Gain. 151n X 5 microphonein- Post 12p. 9Iin x 8tin. 18Ibe. 220/240V se. or 12V d.c. puts each with TAPE Brand new with instructions. 150. Carr. 50p. SPECIAL PURCHASE ! individual gain CASSETTES controls enabling Top NEAT G30) STATIC complete mixing quality TRIO BALANCE PICK-UP ARMS facilities. Battery operated. 91in x Sin x 31n. 96591)13 Inputs Mice:3 x 3mV 50K: 2x3mV 000 Low Noise GOA ,r-74 . COMMUNI- ohm. Phono meg. 4mV 50K. Phono ceramic in Library CATION 100mV 1 meg. Output 250mV 100K. RECEIVER 18.97.Post 20p. COO 3 for 758 10 for 1245 - 4 band cover-Identical specification to NEAT 030 arm C90 3 for 2106 10 for 1830 ing 350101.-but with two-tone chrome and black finish. T/6.1036 STEREO C120 3 for 11-36 10 for 1420 90MHz con-Complete with head shell, pick-up rest and HEADPHONES Tape Head Cleaner 300 each. tinuousandelectrical bandspread onplug In phono leads.BRAND NEW - Low cost high perform- Post 10p extra. 10,15,20,40 and 80 metres.8 valveFULLY GUARANTEED. ance stereo headphones. plus 7 diode circuit. 4/8 ohm output andONLY 1995. Post 25p. Foam rubber ear cups. EA.41 REVERBERATION phone jack. 88B-CW. ANL. Variable BFO. Adjustable head -band. AMPLIFIER 8 meter. Sep. bandspread dial. IF frequency ohm impedance. 25-Self contained,transistor- 455kHz. Audio output 1.3W. Variable RFKAZODEN HM -350 TRANSISTOR TINTER I 8,000Hz. With lead and ised,batteryoperated. and AF gain controls 115/230V a.c. SizeHigh quality instrument stereo jack plug. ONLY Simply pluginmicro- 7In x 13in x 10in with instruction manual. totestReverseLeak 21.97. Post 12p. phone, guitar, etc., and 14950. Carr. paid. current and D.C. current. output into your ampli- Amplification factorof fier. Volume control, NPN, PNP, transistors, NEW GARRARD depth of reverberation control.Beautiful ENT LOUDSPEAKERS diodes, SCR's, etc. 4' X walnut cabinet.7 In x 3iu x 4)0. 26-97. Model 350. 131n x 8inwith4i" clearscalemeter. MODULES Post 13p. single tweeter/crossover,20-Operates from internal 20,000Hz. 15W RMS. Availablebatteries. Complete with TRANSISTORISED FM TUNER * 8 TRANSISTOR 8 or15ohms. 1746each. instructions,leads and Post 37p. carrying handle. 11240. HIGH QUALITY Model 450. 13In x 8in with twinPost 30p. TUNER, SIZE tweeter/crossover. 55-13,000Hz. ONLYBin X 4in x 8W RMS. Available 8 or13 2; in. 3 I.F. stages. INSULATION RE - Double tuneddis- ohms. MIN each. Post 25p. KAMODEN HMG -500 criminator.Ample SISTANCE TESTER output to feed most Range0-1,000 amplifiers. Operates on UV battery. Coverage HONEYWELL Megohms, 500 Volt. 88-108MHz. Ready built ready for use. Fan- DIGITAL Batteryoperated. tastic value for money.16.37. Post 12p VOLTMETER Widerangeclear Stereo multiplex adaptors /497. VT.100 meter45" X4'. Complete with de- PopularrangeofGarrarddecks TX 1018 DR -LURE Canbepanelor luxe carrying case, with Shurecartridge fittedin MONO HIGH IMPE- bench mounted. batteries, instructions. deluxeplinthwith hingedlid. DANCE HEADSET Buie meter mea- Post 30p. sures 1V d.c. but 119.56. sr23 III Module/M75-0 . 12850 Sensitive, soft earpads, can be used to measure a wide range of s.c. A P76 Module/M75-6 adjustable headband. AP96 Module/M75-13 /003-76 Magnetic, impedance and d.c. volt, current and ohms with optional ARP -300 AFiRY 2,600 ohms. plugincards.Specification:Accuracy: SIGNAL GENERATOR Zero 1008 Module/1493E..15260 ± ±1 digit. Resolution: lmV. Number All transistorised, com- Carr. 50p extra any item. 11-97.Post 13p. of digits:8 plus fourth overrange digit. pact, fully portable. AF Overrange:100%(upto1999).Input sine wave 18 Hs to 220 HOS1DEN DH -01111 DE -LUXE STEREO impedance: 1000 Meg ohm. Measuring cycle: KHz. AF square wave HEADPHONES 1 per second. Adjuetment: Automatic zero- 18 Hz to 100 KHz. Out- Features unique mech. ing, full scale adjustment against an internal putsine/square 10v. anical 2 way units and G. W. SMITH P -P. RF 100 KHz to fitted adjustable level. reference voltage. Overload: to 100V d.c. controls.8 ohm im- & CO. (RADIO) LTD. Input: Fully floating (3 poles). Input power: 200 MHz. Output lv. Also see previous pages 110-230V a.c.50/60 cycles. Overall size: maximum. Operation pedance 20-20,000cp. Of in x 2*In X 8*In. AVAILABLE BRAND 220/240v. AC. Complete Complete with sprint and opposite page withInstructionsand lead & stereo jack plug NEW AND FULLYGUARANTEED. 1747. Post 12p. 11115.50. Carr. 10p. leads. 12995. Post 50p.

194 PracticalElectronics March1973 FANTASTIC OFFER! NIKKO /#47 WNW" SAVE UP TO TRM50 33JS% OR MORE STEREO AMPLIFIER SEND S.A.E. FOR FULL 17+17W rams. stereo amplifier with inputs for Magnetic and List price E59.30 Crystal phono, Tuner, Tape, Aux and Tape Monitor. Outputs for OUR PRICE DISCOUNT PRICE LISTS two pairs of stereo speakers and tape. Stereo headphone socket. Full range of controls including loudness control, scratch filter, etc. Sire 13in x 91in x 31 In. £3915AND PACKAGE OFFERS ! Unrepeatable oder -limited stocks! Carriage 50p WHARFEDALE SAVE ELL' s RECORD DECKS NIKKO TRM 50 PHILIPS GA308 (Post 50p) SYSTEM LINTON SYSTEM 88KMcDONALD TRANSCRIPTION 0114 Mini 14-97 C129 Mono 26 50 NIKKO TRM50 17+ TURNTABLE C137 £8 35 17W rnis stereo Wharfedale Linton2 speeds 33i and MP60 £9 60 amplifier, BBR MP60, Amplifier, Linton 610 £12 96 plinth and cover, Turntable, pair of45 r.p.m. Light- GOODMANft 810 £31.26TD100 Teak151-95 Goldring 0800cart- Linton 2 speakers andweighttubular 210/TPD3 £8.75 ridge, pair of Linton 2 all leads. counterbalanced MP60/G800 £12.95 speakers and all leads. arm. Belt driven MP60/TPD1118.06GOLDRING MPI10/TPD1/ 0L69/2 11840 OUR Carr. and low speed syn- 0L72 120.95 PRICE £104-90 Ins. 11.30 chronous motor. 0800 119 50 OUR Carr. and MP60/TPD2£14.86OL72/P 227.50 PRICE E104 Ins. £1.25Viscous damped 610/TPD1 11895Plinth 69/72 17-02 Carr.pick-up lift/ 117-95LID 72 23-25 EDITOR RECEIVER SYSTEM 1155. 510/TPD1 GL75 and Ins. 01-50. lower device. HT 70 113.911 12395 LEAK DELTA 30 Completewith HT70/6800 217.25GL73P 235-25 teakplinthandhingedcover.HT70/TPD I12085Plinth 73 £7 85 SYSTEM HT70/TPD1 LID 75 13.60 AMSTRAD 8000 II GA308 lesscartridge (list 136.55) G99 219-25 Post 50p. 0800 223-90 15396 Leak Delta 30 stereo SYSTEM OUR PRICE 12450. 810 Plinth/ GL85P/C amplifier,Goldring LIMITED NUMBER ONLY! Cover 19-25GI01P/C 120 50 GL75, plinth, cover and 0900 cartridge.Amstrad8000 11 7+7" CONNOISSEUR LEAK Pair of Leak 130amplifier. BIM 18P60, plinth BD1 Kit 11090Delta 15350 speakersandalland cover, Goldring LEAK BD1 Chassis118-60 leads. 0800 cartridge, pair 0.- BD1/SAU2/ MICRO-SEIKI of Apollo speakers Plinth/C 033.10MR111 129 50 OUR and all leads. BARGAINS ! BD2/SAU2/ MR111 Plinth PRICE LI23.50 Ins.C'rr. El 50 OUR Chassis 125-95 and Cover 19-50 PRICE £45.50 Carr. and .ipmemmik BD2/SAU2/ Ins £1 Plinth/C 133-135 PHILIPS Amplifier only, 114.50. Carr. 50p. GAI05 116-95 TELETON SAG120613 GARRARD GA1130 Teak 127-00 2025 T/C 12350 *was GA308 Teak SYSTEM Stereo 611.50 GA212 656 75 MONOTONE 6750 40B Stereo 119-25 Teleton BAQ206B8+8W LIMITED OFFER ! SP23 III 6/0-25 amplifier, BBR MP60 SYSTEM ALL STOCKS BRAND NEW8P23111/ PL12D 134-50 plinth and cover, AND GUARANTEED M73-6 11.696PL13C 15145 Goldring 0800 8P25 III Module/ Monotone AM/PM 4+4W Delta 30 .. £4695 123-50PLA33 132-65 cartridge, pair of stereo tuner amplifier, Delta 70 .. L5795 M75-6 PL50 2111-85 Apollospeakers SL113B 113-75 1113-50 and all leads. Garrard 2025 TIC, plinth Delta FM .. .. 15515AP76 117-95 PL41D and cover, stereo - PLO! 1119-95 OUR cartridge. pair of Delta AM/FM .. 167.95AP70 Module/ PRICE £54.40 Carr. said Delta 75 .. ..112510 M75-6 133130 Ins. £ -20matching 137.500L72B 121-95THORENS Amplifier only, 222.95. Carr. 50p. speakers and all Leak 150 pair .. 131.95B 132.26TDI23 II 16350 leads. Leak 250 pair £4795 401 125.95TDI23AB II19995 Leak 600 each £33.95ZERO 100A13/3.95TX25 16 95 OUR 'Al T. amt Post 50p extra each item. ZERO 1008136-95 TD160C 16895 PRICE E3550 In.. LI ZERO 1008 TD130A II 135 95 SUPER BARGAIN! Mod/1193-E 152-60 ROTEL BARGAINS ! AP96 Module/ WHARFEDALE 8 -TRACK CAR STEREO MW/LW AU. BRAND NEW AND GUARANTEED M73-6 113875 Linton 126 95 TAPE PLAYER CAR RADIO PLINTHS AND COVERS (Post 50p) Fully transistorised, dual waveband.Sion 61in X 41 in X 2in. 12V d.c. Neg. or pos. earth. Budget SP25, etc. /320 Complete with fixing kit, speaker and leads. Budget SP23 Play on £480 Budget AP76/Zero 1008 £450 ONLY E7.50 Post 20p Budget B.S.R. 1325 Tone. volume awl balance controls.Trod. RA2 0 Amp. 123.35SME 2000 System 23450 selector.Complete with matched pair of RA3 0 Amp. £35.95 stereo speakers, connections and fittings. RA6 0 Amp. .. 14815 RECORD DECK PACKAGES (Poet SOLO Post 30p R X150 Receiver . . .. £45.95 ONLY LI595 157.50Decks supplied with RX200 Receiver.. stereo cartridge RX400 Receiver.. £7095ready wired in Post 50p extra any item. plinth with cover. HOMER INTERCOMS GARRARD Ideal for home, SPECIAL OFFER! 2023TC/9TAHCD 112 75 office,stores,fac- ROTEL RH 700 SP23 III/6800 113-50 tories, etc. Supplied SP23 III/M75-6 1113-50 complete with bat- STEREO S023 III/M44-7 819-75 teries,cableand B.S.R. TD8S 8 -TRACK HEADPHONES SP2.3 III/M44-E 120-95 4 free Instructions. 20-20,000Hz. 8-111 ohm. (ListSP23 III/MLLE 122-40 STEREO TAPE PLAYER DECK 09.93). OUR PRICE 1675.AP76/61800 127.95 2 Station, 1397. 3 Station 1.325, Post 15p. Post 23p. AP76/3175-13 230-25 4 Station 1642. Poet 17p. Integrated preamps (output 125mY) to feed AP76/MILE 13350 into any stereo amplifier.Automatic and AP76/5175EJ 132-50 manual programme selector.4 pole syn- SPECIAL OFFER!AP76/G800E 130-75 BH.001 HEAD chronous motor. 210/240Y s.c. STEREO AP76/M44E 130-50 SET AID BOOM OUR PRICE SPEAKERS AP76/2473ED 1313-95 MICROPHONE Carr. 37p. E1625 Matched pair of stereoB.B.R. McDONALD bookshelf speakers. De-MP60/13800 117-50 Moving coil.Ideal for luxe teak veneered finish. MP60/M44-7 111335 language teaching, com- CREDIT TERMS FOR CALLERS AND Size:14rin X gin X 711n. 11395 munications. Headphone MP60/1144-E MAR, ORDER CUSTOMERS. 20. deposit. 8 ohms. 8W RMS.GOLDRING Imp. 16 ohms. Micro- Balance over 12, 18, 24 or 86 months. phone imp. 200 ohms. 16W peak.CompleteGL73/G800 139 50 with DIN lead. 112-95.GL73/0800E 242-50 11462.Poet 16p. ACCESS & BARCLAYCARD WELCOME - Carr. 50p. 10 TOTTENHAM CT. RD. LONDON, W.1 Tel: 01-637 2232 27 TOTTENHAM CT. RD. LONDON, W.1 Tel: 01-636 3715 All Mad Ordts to 257/258 TOTTENHAM CT. RD. LONDON. W.1Tel: 01-580 0670 11 /2 PaddingtoVVn Gr.., Tel: 01-437 8204 London 2 G.W.SMITH & CO (Radio) LTD 3 LISLE STREET, LONDON, 1/V.C:2 Tel01 262 6562 34 L SLE STREET. LONDON. W.C.2 Tel: 01-437 9155 Personal Callers Welcome -All Branches Open 9-6 Mon. to Sat. 311 EDGWARE ROAD, LONDON. W.2 Tel: 01-262 0387

PracticalElectronics March 1973 195 COMPARE OUR PRICES S peaker Bargains ACOB GP95 stereo crystal 146 E.M.I. 13in x 8in 3. 8 & 15 ohms 9THAC Bonotone stereo ceramic plain 2-00 (diamond) 2.00 A.M.C. CS LTD. with tweeter 2-26 AC08 GP67/2C mono crystal es twin tweeter 8.50 ACOB CIP101 compatible crystal 76 Type 350 -20 watt with 19 -TI Bonotone stereo crystal 90 tweeter 8 ohm.. P.P. 37p. 7.25 Postage 5p per cartridge X bin 3. 8 2 15 ohms 1410 "GEMINI" FM STEREO TUNER 7in x 4in 3 2 8 ohms 1.05 Amplifier Modules FARE 8in 8 ohm, dual cone 2.30 One valve chassis amplifier for record CELEBTION 8in 15 ohm 1.50 player, 2W output, volume control and GOODMANS 101n x 61n 3 ohm 1.80 tune control, on/off switch, 12.60 (P. a BAKER GROUP 25 12in 25W P. 25p). 8 or 15 ohm 5.75 3W mono audio module (transistorised). Postage 25p per speaker 4240 (P. & P. 10p). 21 in 8 or 64 ohm P.P. 10p 50 15W mono audiomodule(transis- torieed).11496 (P. a P. 10P). Klt-form eablneis, teak' 3W stereo module (11In watt/channel), (17in X 10In X 610) $375 28-75 (P. a P. 10p). with a 13in x 8in or 8in cut out SW stereo module (20n. watt/channel), (121n x 12in x with a 8in x 5640 (P. a P. 13p) Bin or 8in cut out. 2 25 (please specify cut out) Stereo Headphones Add 36p per Cabinet for poet & packing De -Luxe finish 8-16 ohm matching imp. All components to build this outstanding phase mono/stereo switch complete with lead lock, easily aligned tuner. As described in April/ Microphone Bargains SP and stereo jack plug only 02-76 (P. a P. MIC45 "ACOB" metal cum, 215p.) May/June P.E.We areoffering an optional crystal hand 95 CM 20 Crystal Hand 45 Ito Stereo Phono Socket? chassis and wood sleeve. Completekit,as DX143 Dynamic, cassette -type Headphone adaptor only 41416 (P. a P. stick 1.00 10p). illustrated, including chassis and solid wood MIC60 "AC08" stick crystal 1.00 C3170 PLANET stick metal, Tapes-"MYLAR" base Anent quality sleeve L33 90 post paid. switch crystal 145 British made. DM160 Dynamic unl-dir, Sin BOOft Up 5f In 180011 81111 Allcomponents availableseparately. Send ball metal S-75 In 200ft 46p 71n 1200ft 66P -In It D130 50K/600 ohm unidir, 1200ft 60p 180011 80p S.A.E. for details and itemised price list. ball metal 440 "lin 900ft 49p 71n TW209 Leeson dual Imp ball -lin120011 Up 710 2400f196p metal unl-dir 6.76 Postage 9p each Guitar mike 45 Lapel type, crystal 40 THIS MONTH'S SCORPIO ELECTRONIC IGNITION Postage 17p each SPECIAL OFFER Cartrldgefi--with standard fittings BIB Groot -Klein Complete kit with comprehensive construction A stylii Sp Model 42, effective record cleaner. and fault finding data. £11. Post paid. Data 10p. ACOB GP91/2BC or OP91/38C stereo Retail price £1 .95. Our price 11'60. compatible 1.06 (P. 2 P. 15p) Itemised prices, S.A.E. please. ACOS GP94 stereo ceramic 1.90 Mail Order Dept. E11/71. RIVERSDALE P.O. Box 470, AMCEL, MAIL ORDER, 160 DRAKE ST., Manchester M60 48U SEND Up FOR ROCHDALE Tel. 0706-46234 ELECTRONICS COMPLETE CATALOGUE ALL OUR MERCHANDISE ISFULLYGUARANTEED

SINCLAIR EQUIPMENT- OSMABET LTD. "Z.".',1',7ttcr.VM1',4". IC12 (2.00.. CALLERS BARGAIN AUTO -TRANSFORMERS Z50 . 500W, LBW; 750W, 112; 1,000W, 415; 1,500W, 621; 2,000W, 227; 3,000W, 087.50; 4.000W, 25240. PZ543.97 A limited number of LOW VOLTAGE TRANSFORMERS Z30(350 Prim. 200/240V a.c. 6.3V 1.5A, 11.05; 3A, 01.80; TWIN TAPE DECK UNITS BA CT 12-05; 12V 1.3A, 11145; 3A CT, 12-15; 6A Project 60 iPir CT. 12-80;18V 1.5A CT, 22.15;'24V 1.5A CT, tuner L16.80 ,Z, 22.15; 3A CT, 812.110; SA, 2440; 8A. 16.75; 12A, AFU 44.30 PZ6 119.40; 40V SA CT, 12.715; SOY BA CT, £10. ' III MIDGET RECTIFIER TRANSFORMERS Stereo 60 £7.50 56.40 For FW rect., 200/240V a.c. 9-0-9V 0.3A, 12-0-12V KITS OF PARTS FOR THE IC12 0.25A or 20-0-20V 0.15A, 11.45 each; 9-0-9V 1A, Includes allparts for the printed circuit and 111.15; 12-0-12V IA or 20-0-20V 0.75A. 4145 each, volume bass and treble controls needed to 0/P TRANSFORMERS FOR POWER AMPLIFIERS complete the mono version41,30. Stereo P.P. sec. tapped 3-7.5-15 ohms, A -A 6.6 Kn 30W version with balance control £3.00, (KT66, etc.), 54.65; A -A 3Kn 50W, 1740; 100W I EL34,KT88, etc.). 21240.Multi 0/P lOW, S2-25. POWER UNITS FOR THE IC12 MAINS TRANSFORMERS POWER AMPLIFIERS A set of components to construct a 30V, 0,5 Amp Prim. 200/240V a.c., TX6 sec, 423-0-425V 500 Ma. power supply L2.27. Also suitable Sinclair PZ5 6.3V CT 6A, 6.3V CT 6A, 0-5-6.3V 3A, 13.4-25; fully constructed £3.97. TXI 425-0-4251' 250Ma, 6-3V CT 4A, 6.3V CT 4A, PROJECT 60 KIT 1240 0-5-6.3V 3A, £9. 250V 10051a, 63V 2A, 22.70. Our extremely popular kit contains the extra These superb twin tape deck units were originally G.E.C. MANUAL OF POWER AMPLIFIERS capacitors.DIN plugs and sockets, cables and Covering valve amplifiers of 30 to 400W, with price fuse holder needed to complete Project 60. designed for installations remitting the continuous listof transformers and chokesspecified,80p. replay of filmic or speech when connected to suitable Bernards Amplifier Manual, 5 to 1,000W, 75p. amplifiers and cost approx. £450 each to manu- LOUDSPEAKERS FOR POWER AMPLIFIERS S-DECS AND T-DECS facture.Consisting of two cmiipletely self-contained FANS 15W w/tweeter, 54-99; 30W, 210-90; 60W, tape decks operating at either31in(3button 5-DECS L144 1 1112-90; 100W, 12240; BAKER 25W, 118.40; 35W, 1 - track model) or 7;in (6 button track model). 17.20;Hi-Fi Major Module, 20W W/Tweeter and T-DECS (.5$ I -I ' Constructed to the highest specification with the Xover 30-17kHz, 09.20; EMI 13in X 8in, 1246; ..-:.. finest components available. Nothing has been 8in x 5in 8n, 11415; floodmans Tweeter 311, 12. µ-DEC A 13-00 spared in the construction and the superb beans LOUDSPEAKERS duty capstan motors (2off) and rewindmotors 16fillIC . me? (4off), top grade relays, solenoids, etc.,all bear 2On 16n, 21i0 25n, 3in 30n, 75p; 31in 3 or 150, carriers £1.25 4in 8 or 15n, Sin 3, 8, 15 or 25n, 5in X Sin 3, 8, 15 or witness to the high standards set.A.c. 220/230V 25n,11.05 each; 6Iin 3n, 6in x 4in 8 or 25n, 7In x 50c/s.Verticalorhorizontaloperation.Size: 4in 3 or 15n, 8 x 21 in 3n, 01.25; Pin x 5in 3. 8, 13 SINCLAIR EXECUTIVE 91in x 19In x sits deep.Weight 341b. 25n £1.50; loin 150, 12-50;10 . 6in 30, 12-25. CALCULATOR We have a limited number available requiring either SPEAKER AUTO MATCHING THANEFORMERS _ parts or attention or both to put them in working 12W, 3 to 8 or 150, up or down, 1146. 1101111.1 orderthese are offered to personal callers only. BULK TAPE ERASERS (Depending Instant erasure, tape spools, cassettes, demagnetises Dna= on tape heads a.c. 200/240V. 82.60 plus 25p P. & P. From £10 each cored it ion) RELAYS Bub mini, 6/9V. 2500. 1111.1111 15, 20 or 30V d.c., 2 C.O's 50p each. i imam FIRST COME - FIRST SERVED 12V DC FLUORESCENT LIGHTING -Personal callers only 01-472 2185/2110 for Silicon transistor invertor for 20W tube, 15.75. 1111101111 appointment to view PAPER CONDENSERS OURPRICE Tubular W/E 2.2 mfd, 250V Xovers, etc., 16p, 45 ONLY L69 (List Price L79) Few workingand completeE35 100.Block 4 mfd, 800V, 75y, 1,500V, 41-25. Carriage extra on all orders, etc. SWANLEY ELECTRONICS Carriage and Insurance including Packing case E3-50 S.A.E. ENQUIRIES -LISTS. MAIL ORDER ONLY 32 Goldin' Road, Swanley, Kent 48 Kenilworth Road, Edgware, Middx. HA8 8Y0 Mail orderonly.Postage 10pperitem. Lists 10p. SYPHA SOUND SALES LTD. Tel. 01-958 9314 Official credit orders welcome. 191-193 Plashet Rd., Upton Park,London, 513

196 PracticalElectronics March1973 ALMOST UNBELIEVABLE!Think os the year 1984 and what might be produced then-now get the fantastic ASTRADdor,THIS YEA 17 and SEE for yourself that the incredible Russians have done itall NOW! It's the radio perfectionist's dreamAffre!RUSSIAN MIRACLE'*COMPUTERISED.? corn* true! THIS ONE SUPERSEDES ALL EARLIER MODELS!It will probably make your p t radio seem . THE FAB LOUS\ like a "crystal set"!Complete with optional battery eliminator( ONLY! THeuclIEFEPTION for both battery and mains use!We're almost giving them away,910-go a \is 0TDIFATNHIIIIDE tonSIMITATIONDREROLF at only C20.75-a mere fraction of even today's Russian miracle, ASTRAD17 MISSIO1 price! We challenge you to compare performance and value SO r`?` WA. POstIR IN FROM TIFFS tat C 1.1°-S E A i, with 8110 radios!*Send quickly, after receiving goods test 71 TABLE RADIO& days-refund if not astounded. Elegant black & chrome finish BEMAKINF'otog aomt 111114-11, facia, sat in fabulous Cabinet built case-constructed of MMUNICATION "MAGIC EYrtuning fine Russian hardwood in beautiful Teak Veneer finish- Aso! level indicator vibration, ensures purer & sweeter tone than aver! RECEIVER Volume controlled from a whisper to a roar that would fill a hall! Much wider band spread, for absolute "pin -point" station selection!Plus "MAGIC EYE" tuning level indicator for TARN/IV:Ell ultra perfect tuning sensitivity!Yes, the Russians have sur- 8 .-.- --, --_,,--_-_ ---- I 2 Mom passed themselves, proving again their fantastic ability in the field of WAVEBANDS: --_-_------:.--Z-,4) electronics and brilliantly reflecting their advanced micro -circuitry ,-,----,,,,,._,...._ techniques in the field of spaceship and satellite communications. STANDARD LONG and MEDIUM , , ,.. , __,. ,_,..,.,...... ,., _,.., ...... _,. I Yes, EVERY WAVEBAND instantly at your fingertips including --,..,...,...... ,... 1 Standard Long, Medium, Short and Ultra Short WavesNO 5 SHORT WAVEBANDS."'*COMPARE ,,-,_,---_,,...... , to the four corners of the earth during 24 hours a day ITS PERFORMANC.....,,,,.....,...,,,, including all normal transmissions. VHF: FM/USW. AM: LW,114 ULTRA SHORT WAVES' -,,,.....--,,,-.....,---. MW, SW, gets locally,local and new stationsnot yet with £80, oaerational, and massages from all he world! Expensive TURRET TUNER side control waveband selection unit (as used (V.H.F.Atintr) RADIOS! on expensive T.V.'s!).Every waveband clicks into position giving 41I incredible easeof stationtuning!Genuine push-pull output! F,Earr ON/OFF volume and separate Treble and Bass tone controls for utter or/e.S7 perfection of reproduction and tone!Press -button dialillu- TM, mination!Take it anywhere-runs economically on standard .7CETC. t (We/ batteries(obtainableeverywhere)ordirectthroughbattery01E21:11 SOp eliminator from 220/240v AC mains supply.Internal ferrite rodMAINS/BATTERY faraowateArdahr aerialplusbuilt-in"rotatable" telescopicaerialextendingto 39ins approx.It's also a fabulous CAR RADIO. Can alsoELIMINATOR£148 extra WORLD be used through extension amplifier, tape recorder or public address system.SIZE 14ins x No TUNING 101ins x Ifins overall approx. Magnificently designed, made to give years of perfect service. (U.K. service MOREGUEsswORK_GUIDE! facilities & spares available for years & years to come, if ever necessary!).With WRITTEN GUARANTEE INSTANT DATA manual with simple operating instructions & circuit diagram. ONLY L20.75 (with mains/battery eliminator enablesyou L1.48 extra)BOX, POST, ETC. 50p. BUT WAIT, for only 55p extra you get the sensational at your fingertips transmissionsto T NE! "COMPUTERISED" WORLD TUNING GUI DE (It enables you to time, pinpoint & get transmissions A FLASH- the whole world over-even a child can do it in a flash-it even lets you know when to tun* into the the world to U.K. when abroad. NO GUESSING! NO MESSING!) PLUS Standard 'longlife' batteries PLUS over! ultra sensitive earphone for personal listening. (Sorry-We cannot change these new radios for any earlier model purchased.) HURRY!Send quickly, after receiving goods test 7 days-refund if not delightedOr call. CAVE120.25 NOW. tinkfEEYEEP.:CAVE mine This equipment's got

Or SOLID STATE EVERYTHINGI NEW igeANDAIFW AC/DC BATTERY/MAINS

BATTERY/MAINS AC Combined ea -OdleTAPE 410' ia-aa FIRST V.0.1 AMIFM RECORDER CLASS RADIO and &PLAYER MAKERS CASSETTE With remote control WE COULD TAPE RECORDER ureENDED RECO^- E L44 microphone. CHARGE UP TO & PLAYER gTAIL PRIG £26'97!

OURf23. cAR WITH REMOTE pocE 7c ETC. RW felf CONTROL MICROPHONE 0 eir35 POSTETC. 31p Shopertunities "thunder" ahead with an offer that's FANTASTIC (even by our standards!).We've snapped up 500 magnificent machines. Latest sensation in the world of sound!First-class makers!Fabulous VHF, AM/THE ONE STEP FORWARD EVERYONE HAS WAITED FOR! NOW a superb FM Radio AND Cassette Tape Recorder & Player combined & it alsode -luxe portable BATTERY/MAINS tape recorder and player-and incredible runs off standard batteries or mains. (Simply plug in the 220/240V AC lineShopertunities,brirrg it to you for ONLY £12.49!Due to our cut price we cord.) Record and play back anything, anywhere! RECOMMENDED RETAILcannot name fi rst-class makers-but rest assured you're getting one of the BEST! PRICE GENUINELY E44! WE OFFER AT ALMOST HALF PRICE!Expensive"PIAN 0 KEYBOARD" CONTROL PANEL (or latest MASTER Wonderful features:* Press -button Keyboard Control Panel or latestSWITCH control) AND AUTOMATIC LEVEL CONTROL. No MASTER SWITCH CONTROL! * "MAGIC EYE" Visual Battery check/fiddling with awkward tape and reels, just "slap -in" a cassette and off you go! recording level indicator or built-in automatic Leveller! * Separate ON/(Takes 30, 60, or 90 minute standard cassette tapes obtainable everywhere). OFFand HI -LO volume controls! * Heavyduty built-in speaker! * Ear-Amazing performance ensures perfect tapings and superb reproduction! Remote phone (for personal listening or "monitoring") and ion speaker sockets!control microphone.Rapid Rewind!Fast forward!Beautiful tone from a * Remote control microphone! * Built-in swivel telescopic extensionwhisper to a roar!Completely self contained-record anywhere, indoors or aerial(24in approx.)!Magnificently made case with carry handle.out!Runs on standard batteries AND 220/240V AC mains.Separate (DESIGNS VARY SLIGHTLY.)Takes standard 30, 60, 90 or 120 -minutejacks for remote control microphone.etc.Size 9# in Sin 2/in approx. Cassette Tapes obtainable everywhere. AND the amazing built-infullDesign can vary slightly.With carry handle.WRITTEN GUARANTEE and circuit VHF, AM/FM Radio gives you superb clarity of tone, incredible stationfull instructions. ONLY £12.49 post, etc., 31p. * Refund if you don't a selection. Unique rotating Station Selector Dial, gets locally, local city and regionalwe could charge up to 026.97! BONUS OFFER (one per customer)- stations in every part of the country plus B.B.C. National, VHF.Picks up dozensCassette tape, set of standard batteries AND microphone stand all for of foreign stations.Fabulous in your car!You could payC C's more for a50p extra, if required.Send quickly, after receiving goods test 7 days- Car Radio or Car Cassette player ALONE! E23.75, CARR. ETC. 35p.Com-refund if not delighted. Or call: plete with simple instructions remote control microphone with on/off ma= mom ma- aaa mmi m switch and microphone stand. WITH WRITTEN GUARANTEE. SendrrOrder by post to Uxbridge Road address or call at either store. quickly, after receiving goods test 7 days-refund if not delighted. Or call..Bargains galore at both stores.-(COMMERCIAL TRAVELLERS PLEASE BONUS OFFER; Batteries and Cassette Tape 25p if required. NOTE : Merchandising office at Holborn Store.)

.m10 MN= am= MIN Dept. PE/26, 164 UXBRIDGE RD. (facing Shepherds Bush Green), LONDON WI2 84141.(Thurs. I, Fri. 7).Also at 37/39 HIGH HOLBORN (opposite Chancery Lane), LONDON, W.C.I. (Thurs. SHOPERTUNITIES LTD. 7 p.m.) BOTH OPEN MON. TO SAT. 9 A.M. TILL 6 P.M.

PracticalElectronics March1973 197 Nowg A FAST EASY for fasteasv reliable soldering Ersin Multicore Solder contains 5 cores WAY TO LEARN BASIC of non -corrosive flux, instantly cleaning heavily oxidised surfaces. No extra flux RADIO & ELECTRONICS is required. IDEAL FOR HOME EASY -TO -USE CONSTRUCTORS DISPENSERS.` Build as you learn with the exciting new TECHNATRON Outfit! No mathe- Size 5 matics. No soldering-you learn the (Savbit) 18swg, practical way. 18p (illustrated) UMW Size 19A Learn basic Radio and Electronics at home-the fast, modern way. (60 40 alloy) Give yourself essentialtechnical "know-how"-like reading circuits, 18swg. 18p &OLDER assembling standard components, experimenting, building-quickly and without effort, and enjoy every moment.B.LET.'s simplified study Size 1 cartons all at 25p each Size 15 method and the remarkable TECHNATRON Self -Build Outfit take the in 40 60, 60 40, (60 40 alloy) mystery out of the subject, making learning easy and interesting. or Savhit alloys in 7 gauges. 22swg. 22p Even if you don't know the first thing about Radio now, BIB WIRE STRIPPER AND CUTTER you'll build your own Radio set within a month or so! Model 3A Strips insulation ... and what's more, you will A 14 -year -old could understand from cable or flex without understand exactly what you are and benefit from this ciourse-but nicking wire.4 different doing. The TECHNATRON itteachestherealthing.The Outfitcontainseverythingyou easy to understand,practical settings, 4&6 BAspanner ends, need, from tools to transistors- projects-from a burglar -alarm to ground cutting edges Price 32p. even a versatile'Multimeter which a sophisticated Radio set-help ,Also available, we teach you to use.All you need you master basic Radio and Elec- NEW! de luxe Model 8. Price 58p. give is a little of your spare time tronics-even if you are a "non- andthesurprisinglylow fee, technical" type.And,ifyou From Electrical and Hardware Shops. If unobtainable, write to: payablemonthlyif youwish. want to make it a career, B.I.E.T. And the equipment remains yours, has a fine range of clourses up to Multicore Solders Ltd., Hemel Hempstead,Herts.HP2 7EP so you can use it again and again. City and Guilds standards. You LEARN-but Ws as Specialist Booklet fascinating as a hobby. If you wish to make a career in PRACTICAL PAPERBACKS Among many otherinteresting Electronics, send for your FREE FROM experiments, the Radio set you copy of "NEW OPPORTUNI- build-andit'sa good one-is TIES".This brand new booklet FOULSHAM-TAB -just out-tells youallabout really a bonus. This is first and TECHNATRON andB.I.E.T.'s lasta teaching course, but the full range of courses. FEBRUARY HOW TO READ training isas fascinating as any ADVANCED RADIO CONTROL ELECTRONIC CIRCUIT Edward L. Safford, Jr. 11.00 DIAGRAMS hobby and it could be the spring- EASY WAY TO SERVICE Robert M. Brown and Paul board for a career in Radio and RADIO RECEIVERS Lawrence Electronics. Leo G. Sands E1.00 104 EASY PROJECTS FOR 104 EASY TRANSISTOR THE ELECTRONICS PROJECTS YOU CAN GADGETEER BUILD Robert M. Brown L1.40. FREE Robert M. Brown L1.20 MODEL RADIO -CONTROL SOLID-STATE PROJECTS Edward L. Safford, Jr. 1 40. FOR THE EXPERIMENTER Wayne Green L1.20 APRIL BRITISH INSTITUTE TEN-MINUTE TEST 125 ONE -TRANSISTOR TECHNIQUES FOR PROJECTS OF ENGINEERING ELECTRONICS SERVICING Rufus P. Turner L1.40' Elmer Carlson E1.00 INSTALLING AND TRANSISTOR CIRCUIT SERVICING ELECTRONIC TECHNOLOGY GUIDEBOOK PROTECTIVE SYSTEMS Byron Wels EI.20 Harvey F. Swearer L1.40" Dept. BPEI3 ALDERMASTON COURT, READING RG7 4PF USING ELECTRONIC PRACTICAL SOLID-STATE .4 ccrediled by the Council for the .4 seredelnlion of Correspondence Colleges. TESTERS FOR CAR PRINCIPLES AND PROJECTS TUNE-UP Ken W. Sessions, Jr. L1.40* Albert Wanninger [1.20 RAPID T.V. REPAIR G. Warren Heath 1 -40 - MARCH TEST INSTRUMENTS FOR BEGINNER'S GUIDE TO ELECTRONICS CL T.V REPAIRS (Ed. by) Martin Clifford L 1 .40 - I George Zwick VIDEO TAPE PRODUCTION DIGITAL ELECTRONICS AND COMMUNICATION I NAME AGE PRINCIPLES AND TECHNIQUES (BLOCK 1'.1 PITA Ls) I PRACTICE Joel Lawrence Efrein E1.40* Brice Ward LI.40* HANDBOOK OF ADDRESS ELECTRONIC PUZZLES SEMICONDUCTOR I AND GAMES CIRCUITS LI .40- Matthew Mandl OHO* 'Prices subject to revision I I FOULSHAM-TAB LTD. ISUBJECT OF INTEREST YEOVIL ROAD. SLOUGH. BUCKS. LINS ...... -- I 198 PracticalElectronics March 1973 THE FREE HEATHKIT CATALOGUE ..perhaps the most valuable stereoHifi/Electronics kit publication available today

NEW MULTI -SPEAKER KIT rtomtc Ors OF ELECT Features Four KEF Drive Units. Offers SELECTION monitor qualityat lowestcost. LARGEST vioeLos ror% THE NEW AM FM STEREO RECEIVER KIT IF Ci: y two IC's, two ',is.Black magic' lighting. NEW PORTABLE ENGINE ANALYSER KIT Versatile astomonve teemand tiouble shgoting LOW-PRICED TESTERS AND INSTRUMENTS :or the hobbyist and technician. \\\ PLUS ail the models you have read about in international publications- illy NEW 1214 SERIES STEREO HI-FI Ideal for use for quadraphonic sound. the HOW AND WHY OF KIT BUILDING E,o F in the HEATHKIT way. BUILD YOURSELF A PAIR OF SPEAKERS in an evening - enjoy Ste; vund. GET THE BEST IN HI-FI Enjoy worthwhile kit save:.:. SOMETHING FOR ALL THE FAMILY even a hattei y charge! for dad. LOW COST STEREO RECORD PLAYER value.

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HEATH Heath (Gloucester) Limited,Dept. PE/3/ 73 Gloucester GL2 6EE. Telephone 0452 29451 Schlumberger Heath (Gloucester) Limited. Gloucester GL2 6EE L

PracticalElectronics March1973 199 Catering toyour particular service and production requirements Speciprod OUR RANGE INCLUDES : Screwdrivers : Allen - Ball head - Bristol - Clutch Aerosol Aids : From Kontakt, Antistatik spray - cold head - Hold -e -Zee - Phillips and slotted. spray - Fluid spray - Graphit spray - Oil spray - Soldering Equipment : Resistance and heat controlled Plastik spray - Soldering lacquer - Switch and units. Also thermal wire stripping equipment from contact cleaners - Video spray for cleaning tape American Beauty and Wassco. heads. Tweezers : Quality Swiss made electronic tweezers. Allen & Bristol Keys : L Type. Standard and Long Arm. Ultrasonic Cleaners : Bench models and accessories from American Beauty. Contact Cleaners : Diacrom Diamonded Spatulas and Kontakt aerosols. Work Positioners : The versatile Panavise 300 series for modern precision and allied industries. Nut Drivers : Hex - A.F. - Metric. Solid and hollow shaft and Palnut. Work Viewers : Distortion free Ednalite viewers and optical glass lenses for single and group viewing. Pliers, Seizers and Nippers : Quality precision made hand tools from Xcelite, and other leading products For catalogues and other information on the above of special tools. write : Tel.: 01-629 9556 Special Products Distributors Ltd. Cables: Speciprod 81 Piccadilly, London W1V OHL. London W1V OHL

GEMINI STEREO TUNER (Apr./Jun. 72) Rs, Cs, Pot, [380.PCB as published, L2-10. LOGICAL RADIO CONTROL (Dec. 71/Jan. 72) -Sets incl. Rs, Cs, S/c's PCB'S PHOTO: and Pots (where requ.) but excl. I.C's. Coder I and Clock Pulse Gen., 12.95. GEMINI Coder 2A, [2-80.Coder 28, L3. Decoder, 53p.PCBs as pub., 75p each. MAIN AMPLIFIER MODEL SERVO CONTROL (Feb./Mar. 72) -Sets incl. Rs, Cs, S/c's and Pots (where requ.) but excl. I.C's.Servo Amps: "A", 11.40; "B", [2.55; "C", [1-30. Fail -Safe, 65p. PCBs as published: "A" and "B", 600 each; FROM "C" and Fail -Safe. 50p each. MICROPHONE MIXER (Apr. 69)-S/c's, Rs, Cs, Pots, [1.90.Slider Pots extra, LI.15.PCB (3f in x 41 in) -also holds pots, [1.20. PHOTOPRINT PROCESS CONTROL (Jan./Feb. 72) Finds exposure, controls timing, stabilises mains voltage. PHONOSONICS S/c's, SCR, LDR, Rs, Cs, Pots, Relay. Sw, T/former, [7.60. PCB (31 in 54 in) also holds pots, relay, Keyswitch, All PCB's Fibreglass, Drilled, Rolled Tinned Circuit Diagram and Assembly SOUND SYNTHESISER -Details on request. Notes Free with each PCB. PCB -Mounting Slider Pots with Knobs supplied TAPE NOISE LIMITER (Feb. 72) -Mono Circuit as Alternative to Rotaries at Extra Cost where indicated. PCB's designed by S/c's, Rs, Cs, Pot, PCB (f in x 3in), [2.20.Regulated Power Supply (will Phonosonics except where stated otherwise feed 2 units) and PCB ( I I inx 2f in), L3.20. DESIGNS PUBLISHED IN P.E. ULTRASONIC TRANSMITTER -RECEIVER (May 72) Rs, Cs. Pot, S/c's, Transducers, Relay, [9-90. Dual PCB (tin x S/in), 75p. AURORA (Apr./Aug. 71) Multichannel Sound Controlled Light S/c's (excl. SCRs), Rs, Cs, Cores, Pots., 8 ch., E17.75; 4 ch., [1015. Slider VERSATILE LIGHT EFFECTS UNIT (Jun. 71) -Single Channel Sound Pots extra, 8 ch., L3.70; 4 ch.,12-2.0. Power Supply (supplies 8 chans.), Controlled Light -also has built-in variable strobe. S/c's (excl. SCR), Rs, Cs, unstab., £285: stab., [3.65.PCB (4f in xII in) for Pre -amp and 4 Chan:. Pots, 7/formers, Keyswitch, [8.85. PCB (5} inx5fin) also holds Pots, Sw, incl. all pots, [2.35.PCB (4Sin x 61 in) for PSU, Sync. Gen, 8 cores, 8 SCRs, 7/former (T/T7), LI-SO. Slider Pots (cod. 25R Lin. -Rotary only), 11.10 extra. LI-35. A.F. SIGNAL GENERATOR (Nov. 72) SOME OTHER DESIGNS AVAILABLE Sic's, Rs, Cs, Pots, Sw's, [2.25.PCB (2 in 4in) also holds Sw's, 90p. REVERBERATION UNIT (Practical Wireless Nov. -Dec. 72) AUDIO MIXER (Jan. 72) Sic's,Rs, Cs, Slider Pots, T/former, [630 (with rotary pots [070). PCB (tin X II lin) also holds sliders (compatible with publ. panel) [120. Rs, Cs, Pots (i.c. cud.), PCB (1 fin 2in), LI .55. BIOLOGICAL AMPLIFIER (Jan./Feb. 73) -Pre -amp Set 8 WATT AMPLIFIER (Practical Wireless Nov. 72) S/c's, Rs, Cs, Pots (i.c's excl.) [2.05. PCB (tin 4in), 85p. Main Amplifier-Sic's, Rs, Cs, Pot (Mono Set), [330. PCB (24 in x 3in) (Mono), 60p. Pre-amp-S/c's, Rs, Cs, Pots, Maka-Sw., Mono, 12.50; Stereo, I.520.Slider CALLERCORD (Jul./Aug. 71) Automatic Answering Machine Pots extra, Mono, LI.26; Stereo, (1.52.PCB (3I inx 7f in) (Stereo) - S/c's,Rs, Cs, Pots, Switches, Relays, Transformer, [1215.PCB (4in x also holds all pots and Maka-Sw., LI-SO. 71.in) also holds relays, connectors, LI-SO. Recorder, (6.95. Pips Gen with PCB, LI-SO. AURORA AUXILIARY CONTROL UNIT (2variablefreq. strobe lens. and 4 variable amplitude freq. gene.), Rs. Cs, Pots, S/c's, DOOR BELL YODELLER (Apr. 71)-S/c's, Rs, Cs, Pots, [4.20. [325. Slider Pots extra, [2-34. PCB 131 inSim), also holds all pots, [115. Transformer, [1.30.Loudspeaker, [1.30.PCB (3in x 3f in), 90p. THYRISTORS (400V P.I.V.) ELECTRONIC PIANO (Sept. 72/Jan. 73) IA 50p. 3A 5Sp. 7A 70p. 16A 95p. Pre -Amp -Rs, Cs, Pots, [1.90.PCB as published, [1.60. Power Supply - Rs, Cs, [1.15. PCB as published, 95p. Pitch I -12 -Rs, Cs, [2.10 each set. Pitch Lists for these and latest new designs -send S.A.E. 13 -Rs, Cs, [1.50, Pitch PCB as published L135 each. Discounts for Qty. Orders: U.K. leo P. & P.Overseas at test.Moil Order only. GEMINI STEREO AMP (Nov. 70/Mar. 71) Stereo Sets and PCBs Pre-Amp-S/c's, Cs, Pots, Maka-Sw's-with PA, 2% M.O. Rs, E13.45 -with fW 5% C.F. Rs. [11.20. - with PP/ 5% C.F. Rs, [1075.- with Slider Pots V.A.T. WILL BE CHARGED ON ALL U.K. ORDERS FROM APRIL Ist. extra,(1.65. PCB (3f inx10lin)forkits with M.O. or SW C.F. Rs. Holds pots and Maka-Sw's, [2.10.Main Amp -Rs, Cs, Pots, 1530. PCB (3Iin Sin), [1.40. PSU-Rs, Cs, Pot, [3/0.PCB (tin x 4in), 75p. Dept. P.E.3, 25 Kentish Road, Belvedere, Kent DAI7 SEW

200 PracticalElectronics March 1973 A Speaker System to meet every need

EMI provides the speaker system to suit To: EMI Sound & Vision Equipment Limited. EMI Pathe your needs and your budget, all with one thing Division, 252 Blyth Road, Hayes, Middlesex. 01-573 3888 in common, superb quality of sound over the Please send me details of EMI loudspeaker's full audio range. Choose from new elegant and name of nearest stockist. speaker enclosures for the connoisseur; home Name assembly enclosure kits and matched speaker Address kits and a range of basic chassis loudspeakers PE/3 as used in the highest quality sound reproduction equipment. EMIPerfection in Sound Send for full details and name of your A member of the EMI Group of Companies. International leaders in Electronics. nearest stockist. Records and Entertainment.

PracticalElectronics March 1973 201 MAIL ORDER DEPT. COMPONENTS AND HI Fl No. II FOR THE HOME CONSTRUCTOR MAYES RD. RADIO TO OUR SHOPS ARE OPEN ALL DAY CRESCENT LONDON FROM 9 A.M.TO 6 P.M.6.30 P.M.ON FRIDAY 1422 (WE CLOSE ALL DAY THURSDAY) 6TL 111 40 MAYFS ROAD, ONDON Nil 611 888 3206 13 SOUTH MALL, EDMONTON, N.9 803 1685 LOW VOLTAGE TRI-VOLT BATTERY DIGITAL CLOCK KITEA1000 3 WATT AUDIO AMPLIFI ELIMINATOR 24 -hr. Nixie dig. clock kit. AMPLIFIER We supply: a complete set An Audio Amplifier designed around the 5 transistor amplifier complete Enables you to work ---W1-1of components; a complete TAA621 Linear I.C. with volume control, is suitable your Transistor setofeasytofollow Supply Voltage 9-24V for 9V d.c. and a.c. supplies. Radio, Amplifier or instructions;printed circuits made to Speaker Imp. 8-16 ohm Will give about 1W at 8 ohm Cassette,etc.,from make construction as simple as possible; Frequency .. 5011,25kHz . dm. output. the a.c.inains through this compact a cabinet and front panel to give Overall Size ..tin X 3I0 x Lin With high IMP input this ampli-Eliminator.Just by moving a professional finish. All for the price of Ideal Amplifier for radios, recordplayers, stereo units, etc. fierwillwork asa recordplug you can select the voltage you the components. 122.150 + 50p P. & P. £2.63 player, baby alarm. etc.,require,8,7;or9volt.This Please send S.A.E. if you require more Full technical data and diagrams with each amplifier. means all your transistor power information. module. All guaranteed and a bargain at + 5p P. & P. pack applications can be handled by this one unit.Approx. size I.C. MODULE TYPES1,403D MUT LOIIIHPRAZERS MAINS TRANSFORMER 3W e.m.s. power amplifier and pre- 211n 8 ohm . 21in Y 21in Y, 31in.Our Price 5OP Fused Primary 240V. Secondary 220V 12.75 plus 10pP. &P.Same amp.Complete with data sheet. 21in 80 ohm 1:604 @ 50mA. 6.3V @ 1A. This trans- 11.75modelsuitablywiredforthe Fully 211n 40 ohm . . 609 former Is made to very plus 13p P. & P. Philips Cassette 13 plus loP P. & P. guaranteed. %111,1111 Please Include 5p P. & P. onhigh standard and is a 8140. ear, 7p. each L.B. small size :2ln X 21in 1.0. BROWN -DIPLOMAT" MONO/ TRINOLT CAR SUPPLY X 21in.63p plus 15p ITEREO HEADSET. Finest quality ADD LUXURY TO YOUR CAR P. & P. British made Lightweight Enables you to work your Tran Igor Radio, Amplifier Headphones. Incorporate or Cassette, etc. from the 12 volt car supply.Positive orWITH A MOTOR DRIVEN ceramic piezo electric negative earth. Approx. sine w tin. x 31in. x liin.OAR AERIAL transducers. 8prefft- This converter supplies 6, 71 orvolts and is transistorSpec.: 5 Section caffon:-Frequency- O regulated. A real money savindevice for 42.50 plus Extended Length 100.11 20-17,500 CPS.Impedance -Pre- 10p P. & P. Length under Fender 40cm dominantly capacitive, at 001MFD Cable Length 120cm per earpiece can be regarded as 150K MINIATURE RELAY Supplied complete with Fixing at Ikea Weight-3.5oz. (98 grams). 6 volt 70 ohm. plus 25p EMI LOUDSPEAKER 450 Please include 10p per set P.P. Single Pole Changeover 40p plus 5p P. & P. ControlBracket Switch.itch. L3'/3 P. & P. lOW 13in x 8in ± two 2.21in A Bargain at 41.50 each set. Approx. size w 1110. x lin. X lin. E5.75 tweeters and cross -over.All wired and readyforuse.This ever - CRESCENT CASSETTES R. A 4. popular 450 in 3-8-15 ohm imp. U.BUILD.IT E3-50 plus 38p P. & P. each. Top quality cassettes at unbeatable prices (complete withWe supply the three modules for you to build this Disco-Group-P.A standard storage case): COO 28p, C90 589, 0120 40p tth).. amplifier into the cabinet of your choice. 5p P. & P. * THE POWER AMP MODULE TP100W 7 1" LOUDSPEAKER 170W r.m.s. sq. wave 300W instantaneous peak into 8 ohm (60W A top quality PSYCHEDELIC LIGHT CONTROL UNIT into 16 ohm). 1114.88carr. 45p speaker ideal where ThreeChannel: Bass -Middle --Treble. * THE PEE -AMP MODULE small size Is Import- Each channelhasits own sensitivityFour control pre -amp, Vol, Bass, Treble. Middle controls. Designed ant.Manufactured control.Just connect the input of thisto drive most amplifiers using F.E.T. first stage.SEMIcare. 25p by E.M.1. for well- unit to the loudspeaker terminals of an* THE POWER SUPPLY MODULE P1100 known hi -fl set amplifier, and connect three 260V up to carr.50p gt) maker. Rise: 71n. x Is supplied complete with the mains transformer. 29-66 500W lampstotheoutput terminalsCompletefixinginstructionsaresuppliedand no technical 4in.Impedance: 8 ohms.Flux: / of the unit, and you produce a fascinatingknowledge is required to connect the three ready wired modules. 38,000. Max. Free range: 90Hz to sound -lightdisplay. (Allguaranteed) A fantastic bargain.If you purchase all three modules. 12kHz. Power handling: 5W. 11810 plus 38p P. a P. 225 care. 75p Unbeatable. Price: *1.60.Free If you require more information please send S.A.E. Send S.A.E. for further details on this or our ready built amplifiers.postage on this item.

P.E. SOUND SYNTHESISER Get away to a flying start with this exciting Space Age project. Precision cut metal parts to form modular units as described in this issue are available NOW. A. Power supply subframe with tabdrillingsonly £1.35 (P. & P. 25p). B. Circuit board support plates fully drilled, 94p.

Panelsdrilledwithlocatingholes only:C. 20mm, 18p; D. 38mm, 21p; E. 60.5mm, 28p; F. 64mm, 31p; G. Module locking rods complete, £1.20. SAVE MONEY by obtaining a complete kit of hardware which comprises I off each A, C, D, F, 5 off E, and 7 off B, G C17.42, Post Free. "SCOPE" built REGULATED POWER SUPPLY fully assembled and GUAR- ANTEED. Voltagerailsadjustable from 8-17V. Nom. 15-0-15V at 500mA per rail.Stab. ratio 250 : 1; Ripple and Noise 5000/ at full load.Load regulation < 1% zero to full become load, line regulation < 4% for 10% change in mains voltage. Size 4in x 2}in x 7in fits easily into power supply subframe. Terrific value at E19-50 Post Free.(Include 15p for insurance a RADIO -AMATEUR ! if required.) learn how to become a radio -amateur Let us quote you for bulk supplies of any items listed. in contact with the whole world. We give a. skilled preparation for the G.P.O. licence P.O.Box No. 3 ST. NEOTS free ! Brochure, without obligation to: EATON AUDIO HUNTINGDON BRITISH NATIONAL RADIO & ELECTRONICS SCHOOL P.O. BOX 156, JERSEY TERMS: MAIL ORDER ONLY. C.W.O. Cheques or crossed P.O. payable to Eaton Audio. Minimum order E2. POSTAGE/ NAME PACKING: some items show P. & P. charges in brackets, ADDRESS: EB33 where P. & P. charges are not shown please add 10p in the LI to orders under £5. Orders over a will be sent free of P. & P. BLOCK CAPS please

202 PracticalElectronics March1973 THIS IS THE FIRST PAGE OF THE GREAT BI-PAK SECTION BRAND NEW FULLY GUARANTEED DEVICES AC107 0.20AD162 1438BCI48 0 10 BD187 0.45 BF188 0.400C19 0.3520371 0.16 AC113 0-20AD161 S BC149 2N2219 0 20 2113054 0.46 2114059 0.10 0.12 BD188 040BF194 0.110020 0-4320871E0 12 2112220 0 22 2113055 AC115 043 ADM (MP) B0150 0.18 BD189 0.60 2N40600.12 0.65BF195 0.120C22 0-3820373 0 17 2112221 0-20 2113391 0.14 2N4061 0.141 AC117 K 0.20 0.55 BC151 0 20 BD140 040 B F196 0.140023 0.4220374 0 17 AC122 0.12 ADT140 0.50 BC152 2112222 0.20 2N 3391 A 0.102N4062 0.12 0.17 BD155 020 BF197 0.140024 0.5820377 0 30 2112368 0.17 2113392 0.14 AC126 0.17 A F114 0.14 BC153 0 28 BD176 8.88 BF200 2N4284 0.17 50196 0.17 0-450025 0-8820378 0 16 2N2369 0.14 2113393 0.142N4280 0.17 AF115 0.24 BC154 0 30 BD176 0.00 BF222 0.95 0026 0-2520281 0-16 2N2369A 0.14 AC127 0.17 AF116 0.24 BC157 0.18 BD177 2118394 0.14 2114286 047 4.65 BF257 0.450028 0.6020382 0 16 2112411 0 24 2N9995 0.17 2114287 0.17 AC128 0.17 AF117 0.54 110158 0.12 BD178 0.66BF258 0 600029 0.8020401 AC132 0-14 A FI18 0 80 2112412 0 24 2113402 0.21 2114288 0.17 0.35 BC159 011 BD179 0.70BF259 0.95 0035 0.4220414 0.80 2112646 0.47 AC134 0.14 AF124 0.10 BC160 2113403 0.21 2114289 0.17 0.45 BD180 0.70 BF262 0.611 0036 0.5020417 0 25 2N2711 0.21 2N34040.282N4290 50187 0.14 AF125 0.26 BCI81 0.60 BD185 0.65 B F263 0.550041 0.20 017 AC141 AF126 2N388 0.35 2112712 0-21 2N3403 0 42 2114291 0.17 0.14 0.211 11C167 0 12 BD186 0.65BF270 0-250042 0.54 22438850.56 2N27140-21 50141K 0.17AF127 0211 BC168 2144140.152N4292 0.17 0.12 BD187 0.70BF271 0.200044 015 211404 ,0 20 2112904 0.17 2113415 0.15 AC142 0.14 A F139 0.20 BC109 0.12 BD188 070BF272 2N4293 0.17 0.500045 0.12 2 N404 A 0 28 2N2904A 0.21 2113416 0.28 21115172 012 AC142 K 0.17AF178 0.60 110170 0-12 BD189 0.75BF278 0-35 0070 0.10 2/1524 0 42 2112905 A0161 0.15AF179 0.60 0.21 2113417 0.282/15457 042 110171 044 BD190 0.75BF274 0-350071 0-10 211527 0 49 2N2906A 0-21 2113525 AC164 010AF180 0.60 BC172 0.14 BD192 0.75 21115458 041 0.85BFW10 0.600072 0 14 211598 0.42 2112906 0.15 2118646 0-09 2115459 0.40 50166 0.110 AF181 0.4580173 0.14 BD196 0.85BFX290.270074 0.14 211599 50166 0-20 0.45 2N2906A 0.18 2143702 0.1028301 0.60 AF186 045BC174 0.14 110197 0 90BFX84 0-2200'75 0.15 211696 0.12 2/12907 0.20 2113703 AC157 0-24 Ann 0.37 80175 0.29 BD198 0.102830250.42 0 90BFX850.300076 0.152N097 0.18 2N2907A 0.22 2113704 0.11 28902 0.411 5C165 0.90AL102 0.45B0177 0.19 BD199 0.95 BFX86 0.1111 0077 0 25 AC166 211698 024 211292o 0.14 2113705 0.10 221303 0.55 0.20ALIO 0.65BC178 0.19 BD200 0 96 BFX87024 00,81 0-15 211699 0.85 2N2924 2N3706 AC167 0.20 519Y26 0-25 110205 014 0.0928304 0.70 BC179 0.19 0.80 BFX88 0.22 008113 0.152N706 0-08 2112925 0.14 2118707 0.11 28305 0.04 AC168 0.54 5BY27 0.50 110180 0 24 BD206 0.80 BFY50 0.900082 0.152N706A0.09 2N2920 (0) AC169 0.14 ASY28 045 BC181 0 24 2118708 0-0728306 0.54 BD207 0 95 BFY51 0.5000820 0.15 211708 0.12 0.12 2142709 0.0928307 0.54 AC176 020 ASY 29 0.25BC182 0.10 BD208 0.95 BFY59 0.200083 0.20 211711 0.80 AC177 024 ASY5O 2N2926 (Y) 2113710 0-09 28921 0.58 0.26BC182L0.10 BDY201.00BFY52 0.170084 0.20 211717 0.85 0.11 2113711 0.09 5C178 0.23 58Y51 0.94 110283 0.10 28922 0.42 BF115 0.24BPX25 0.6500139 0.202N718 0.24 2112926 (0) 2113819 0.28 283225 0411 A0179 028 A0Y62 0.25BC183L0.10 BF117 0.45B8X19 0.1500140 AC180 0-17 58Y34 0-20 2N718A0.50 0.10 2N3820 0.6028929 056 02550184 0.12 BF118 0.70 B8X 20 0.1500169 0 26 211720 0 28 2112926 (8) 2N3821 0 85 28824 0 70 ACI80K 0.20 A8Y55 0-UBC184L0 12 21F119 0.70 B8Y25 0.1500170 0 26 211727 0.28 AC181 0.1755716 0.10 2113823 0-2828325 0.70 0.25 BC186 0 28 B9121 0.46 130026 0.1500171 0 25 211743 020 2112926 (B) 2113903 0 28 28326 0.70 AC111180.20 58Y57 0.25 100187 0 28 BF123 0.50 BSY27 0.1500200 0 25 211744 0.90 AC187 0.22 A8Y58 0-35 B0207 0.10 2113904 0 80 28327 0 70 0.11 BF125 0.46 B0Y28 0.1500201 0-28 211914 014 2113010 070 2113905 0-28 28701 0.42 AC187K 0.2058821 0.40BC208 0.11 BF127 0.50 BSY29 0.1500202 0 28 211918 0.80 2119011 AC188 0.22 BC107 0.09 014 2113900 0 27 40301 0 40 BC209 0.12 BF152 0.55 ABYSS 018 00203 0.252N929 0.21 2113053 0.172N4058 0.1240362 0 45 AC188K 0.20 BC108 0.09 BC212L0-11 BF159 0.45 1321Y39 0-18 OC204 0 25 2N930 0 21 ACY17 0.25 BC109 0.10 BC213L0.11 BF154 0.45 1181`..0 0-28 00205 0.85 2111131 020 ACY18 0.20 BC113 0.10 BC214L0.14 BFI55 0.70 BSY41 0-28 00809 0.40 2111132 0112 ACY19 0.20Be114 0.15 BC225 0-25 BF150 0.44B8Y95 0.12 P346A 0-20 2111302 DIODES AND RECTIFIERS AC Y20 0.20BC116 0.14 0.15BC226 0.85 BF157 0-45B8095A 0.12 P397 0.42 2141303 014 A5119 0.08BY133 0-21 0510 0.25 a. AC Y21 0.20 BC116 0-15 BCY30 0 24 BF158 0.56 Bu105 5.00 OCP71 0 43 2111304 0-17 ACY22 0.16 AA120 0.08BY164 0.50 0A47 0.07 (/) BC117 0-15BCY31 0.24 BF159 0-60 C11114 0-60ORP12 0 48 2112305 0-17 A5129 0.00BYX38/30 0A70 0.07 50427 0.18BC118 0.10 BCY32 0.80 BF160 0-40 0400 11.80 ORM 0.402N1306 AA Y30 cb ACY28 0.19 091 0.09 0.42 0A79 0.07 BC119 0.30BCY33 0 22 BF162 040 0407 0.25 031P61 0.40 2111307 0.21 A A7.19 0.10B0ZI0 0.85 0A81 0.07 ACY29 0.85BC120 0.20BCY34 0.25 BF103 0.40 C424 0-208T140 0.12 2111308 0-28 BAI00 0-10 ACY30 0-2880125 BYZ11 0.80 0A89 0 09 0.15BCY70 0-14 1/F164 0.40 C425 0-50 ST141 0 17 2111309 0.23 BA 116 0-21 BYZ12 080 0A90 0 06 ACY31 0.2850126 0.15 BCY71 0.18 BF265 0.40 0428 0.25 TI843 0.80 0.21 2N1613 0-20 BA126 0.22 BYZ13 0.25 0591 0 08 ACY84 BC182 0.12BCY72 0.14 BF167 0-220428 0.20 U T46 0 27 2111711 0.20 BA148 0.14 BYZ16 0.40 0A96 0.07 0 20 BF173 0-22 C441 0.8020301 0.09 2111889 0.82 ACY86 35154 0.18 BY Z17 0.85 05200 0.00 0.28 30185 5.12BCZII 0-25 B F176 0-850442 0-3020302 0.19 2111890 0.45 BA155 0.14 BYZ18 0.85 ACY40 017 BC136 0.15BCZI2 0-26 05202 0.07 BF177 0-85 0444 0.2620303 0.192N1899 0.27 BA156 0-12BYZ19 0.28 ( /. ACY41 0.15 BC137 0.11BD121 0.60 BF178 0-800450 0-3220304 0 24 2112147 0.72 BY100 0.150062 0D108D10 05 ACY44 0.85B0139 0.40 BD123 0.65 B9179 0-80MATIOO 0-1920306 0 40 2112146 0.57 BY101 50180 0.12 BC140 0.20 BD124 0-19(85) 0A91 11134 0-07 0.60 BF180 0-30MAT101 04020308 0.85 2112160 0.00B1105 0.17 0.05 11134A 0.07 AD140 0.48 110141 0.30 BD131 0.60 BF181 0.30MAT120 0.19 20309 0.85 2112192 0415 BY114 0.18 AD142 0 48 110142 00651 111914 0 06 0.20 BD132 0.60 B2e182 0-40MAT121 0.20 20339 0-20 2112193 0 85 BY126 0.14(14q) 0A70- 111916 AD143 0 38 110143 0.14 BD193 BF183 0.00 0.65 0-40MPF102 0.42 20339A0.16 2N2194 0.85 BY127 0.150579 0.06 111414/10 06 A D149 0 50 130145 0.46 BD135 0.40 11F184 0.25MPF104 0.37 20344 0.18 2112217 0-22 BY128 01/101 0 38 0C147 0 10 0.150A3 0.85 18021 0 10 BD130 0.40 B Fl 85 0.30 MPF 1050.8720345 0.162N2218 0-20 BY 130 0.16 OA 58L 0.21 18951 0 04

11711B0 COMPONENT PANS THE NEW S.G.S. EA 1000 AUDIO NEW COMPONENT PAK BARGAINS I X ED ELECT SONIC COMPONENTS Pack Excepi I may good valve AMP MODULE *Guarantee No.Qty. Desuiplion Price Resistors.capacitors, note,electrolytl., C 1 and coils plus many other useful item, 250Resistors mixed values approx. count by weight 0.50 Approximately 31bs in weight. Price iglt I C 2200Capacitors mixed values approx. count by weight 0-80 P & P. 61.60 only. 3 Watts C 8 50Precision Resistors -1%, -01% mixed values.. 0-50 C 4 76 4th W Resistors mixed preferred values 0.80 R.H.S. C 6 5 Pieces assorted Ferrite Rods .. 0.50 BRAND NEW ONLY C 6 2Tuning Gangs, MW/LW VHF .. 0.60 C 7 1 Pack Wire 50 metres assorted colours POST OFFICE .. 0-S0 C 8 10 Reed Switches 0.50 TYPE TELE- 22.63 each C 9 3Micro Switches 0.60 Modual Tested and Guaranteed'. C10 15Assorted Pots & Pre -Sets 060 PHONE DIALS Qty. 1-9 12.63: 10-25 UN Price each. Larger C11 6 quantities quoted on request. Full hook-up diagrams Jack Sockets 3 x 3.5m 2 x Standard Switch Types.0 50 and complete technical data supplied free with each C12 40Paper Condensers preferred types mixed values ..060 ONLY 75p each modual or available separately at 10p each. C13 20Itlectrolyti. Trans. types 0.50 014 1 Pack assorted Hardware-Nuts/Bolts, Grommets etc... 0.50 015 4Mains Toggle Switches, 2 Amp D/P 0.50

C16 20Assorted Tag Strips & Panels .. . 0 50 C17 10Assorted Control Knobs 0.50 018 4Rotary Wave Change Switches 050 SYSTEM 12 STEREO C19 3 Relay. 6-24V Operating .. 0.50 C20 4 Each Kit contains two Amplifier Mod- Sheets Copper Laminate approx. 10' xr . 0.50 Please add 10p post and packing on all component packs, plus a further 10p ules, 3 watts RMS, two loudspeakers, on pack Nos. Cl, C2, C19, C20. 15 ohms, the pre -amplifier, trans- former,powersupplymodule, PLUS -MUCH MORE- front panel and other acces- At .0 sories, as well as an illus- -..-w, trated stage -by -stage instruc- SEND NOW FOR THE tion booklet designed for the ONLY BI-PAK "Component Catalogue" beginner. Further details available on FREE 5p to cover postage etc. request. £16 95P. & P. NOW -TURN OVER FOR MORE FANTASTIC OFFERS

PracticalElectronics March1973 203 The largest selection NEW LOW PRICE TESTED S.C.R.'s KING OF THE PAKS Unequalled Value and QualityQUALITY TESTED SEMICONDUCTORS Pak No. Price PIV IA 3A 5A 5A 7A 10A 16A 30A cp TOO T086 TO16 T064 TO48 TO48 TO48 T048 NEW BI-PAK UNTESTED 500.230260.350.350.470.500.531.16 Q1 20 Red spot transistors PNP 0.50 100 0.250.330.470470.500.580.63140 SUPER PAKS SEMICONDUCTORS Q216 White spot R.F. transistors PNP 0.50 2000.350.370.490.490 570.810.751.60 Q3 4 00 77 type transistors 0.50 400 0.430.479560.560.670.760.931.75 Q4 6 Matched transistors 0044/45/81/813) 0.50 600 0.690.570680.680.770.971.25- Satisfaction GUARANTEED in Every Pak, or money back. Q5 4 OC 75 transistors 0.50 8000 610.700.800800.901201.504.00 Q6 5 00 72 transistors 0.50 Pak No. Description PriceQ7 4 AC 128 transistor PNP high gain 0.60 Q8 4 AC 126 transistors PNP 0.50 SIL. RECTS. TESTED 17 1120 Giese Sub -Min. General Purpose Germanium Diode...0.50 49) 7 OC 81 type transistors 0.50 60 Mize° Germanium Transistors AF/RF 0.50QI07 OC 71 type transistors 0.50 10A 30A U 2 PIV 900mA 750mA IA 1 5A SA 76 Germanium Gold Bonded Sub -MM. like 0A6. 0A47 0.50 Q112 AC 127/128 Complementary pairs 50 004 005 0.06 0.07 0.14 0.21 0.60 U 3 PNP/NPN 0.50 100 004 0.06 005 0.13 0.16 0.23 0.76 U 4 40 Germanium Transistor. like 0081, AC128 0.50Q123 AF 116 type transistors 0.50 200 005 0.09 0.06 0.14 0.20 0.24 1.00 U 6 60 200mA Sub -211n. Silicon Diodes 0.60Q133 AF 117 type transistors 0.50 400 0.06 0.19 0.07 0.20 0.27 0.87 1.25 U 6 30 Sil. Planar Trans. NPN like BST95A. 2N706 0.50Q143 OC 171 H.F. type transistors 0.50 600 0 07 0 16 0.10 0.2., 0.34 045 1.86 Q157 2N2926 fill. Epoxytransistors 800 0 10 0.17 0.11 0.25 0.97 0.56 2.00 U 7 16 OM Rectifiers TOP -HAT 750mA VLTG. RANGE up to 1000 0.50 mixed colours 0.60 10000.11 0.25 014 0.30 046 0.63 2.60 U 8 50 811. Planar Diodes DO -7 01w 2150mA like 0A200/202 0.50Q162 GET880lownoiseGermanium 1200 - 0.33 - 0.38 0.57 076 - U 9 20 Mixed Voltages, 1 Watt Zener Diodes 0.60 transistor. 0.50 Q176 NPN 2 x ST.141 & 3 x ST.140. - .0.60 U10 20 BAY60 charge storage Diode. DO -7 Glass 0.60 TRIACS FULL RANGE Or Q18 4 MADT'S 2 X MAT 100 & 2 x MAT 1511 25 PNP fill. Planar Trans. TO -5 like 2N1132, 2N2904 0.60 120 0.50 V BOM 2A 6A 10A ZENER DIODES VOLTAGE RANGEUt2 12 Silicon Rectifiers Epoxy 500mA up to 800 PIV 0.50Q193 MADT'S 2 x MAT 101 & 1 x MAT TO.1 TO -66 TO -88 0.60 121 0.641 2-33V. 400mV (D0.7 1713 30'PNP-NPN Sil. 'humidors 00200 & 28 104 0-50 19 Sp Q204 OC 44 Germanium transistors A.F 29 Csse) 139 ea. 15W (Top -1514160 Mixed Silicon and Germanium Diodes 0.50 Q214 AC 127 NPN Germanium translators 0.50- 100 50 Hat) 1119 ea. IOW (90-10 60 76 Stud) 25p ea. All fullyU15 25 NPN 811. Planar Trans. TO -5 like BFY61, 2N097 0.50Q22 20 NET transistors A.F. E.F. coded 0.60 300 60 60 90 10 3 -Amp Silicon Rectifiers Stud Type up to 1000PIV 0.60Q29 10 OA 202 Silicon diodes sub -min 0 60 tested5% tol.and 1716 Q248 OA 81 diode. 0.60 400 70 76 1-10marked.StatevoltageU17 80 Germanium PNP AF Transietore TO -5 like ACV 17-22 0.50Q25 16 IN914 Silicon diodes 75 PIV 75mA 0.50 required. 8 6 Amp Silicon Rectifiers BYZ13 Type up to 600 PIV 0.60Q288 0A95 Germanium diode. sub -min DIACS 1718 019 25 Silicon NPN Transistors like BC108 0.50 IN69 050 FOR USE WITH 10 amp POTTED Q272 10A PIV Silicon rectifiers 15425R 0.50 TRIACS 1720 12 1.5 Amp Silicon Rectifiers Top Hat up to 1000 PIV 0.50Q282 Silicon power rectifiers BYZ 19- .0.50 BR100 (D32) 1173) each BRIDGE RECTIFIER 1721 30 AF. Germanium Alloy Transistors20300 Series 4 00710.50Q294 Silicontransistors 2 x 2N696, on heat sink. 30 MADT'e like MHz Seriee PNP Transistors 0.50 1 x 274697, 1 x 2E698 0.50 FREE Q307 Siliconswitchtransistors 2N706 100PIV. 909 each 1724 20 Germanium 1 Amp Rectifiers GJM Series up to 300 PIV 0.50 NPN 0 50 One 50p Pakofyour 0.50 ownchoicetreewith U26 25 300 ME. NPN Silicon Transistors 2N705, BSY27 Q316 Siliconswitchtranslators 2N708 orders valued 14 or over.NEW LINE 028 30 Fast Switching Silicon Diode. like IN914 Micro -Min. 0.50 NPN 0 50 Q323 PNP Silicon transistors 2 x 2N1181, Plastic Encapsulated 1727 12 NPN Germanium AF Transistors TO -1 like AC127 0.50 BRAND NEW TEXAS 1 x 2N1132 0.50 2 Amp. BRIDGE RECTS. 1729 10 1 Arno SCR's TO -5 can, up to 600 PIV CRI91/25-600 Q939 Silicon NPN transistors 2N1711 0.50 GERM. TRANSISTORS 50 v RMS 1129 each 1780 15 Plastic Silicon Planar Trans. NPN 2N2926 ...... 0.50Q947 Silicon NPN transistors 2N2369, Coded and Guaranteed 100 v EMS 379 20 Silicon Planar Plastid NPN Trans. Low Noise Amp 2N3707 0.60 500M112 (code P997) 0.50 400 v EMS 40v 1731 Q95I Silicon PNP TO -5. 2 x 2N2904 & Pak No. EQVTSire 15 mm xfi mm. 1732 25 Zener Diodes 400enW DO -7 case 3-18 volts mixed 0.50 1 x 2742905 0.50 U33 15 Plastic Case 1 Amp Silicon Rectifiers IN4000 Series 0.50Q357 2913646 TO.18 plastic 300 MHz NPN 0.60 T1 269719 0071 3 2N3053 NPN Silicon transistors 0.50 T2 3)1374 0075 UNLT'UIICTION U34 30 Silicon PNP Alloy Trans. TO -5 BCY26 28302/4 0.50Q97 TS D1216 0081DLIT40. Eqvt.2N2646, Q387 NPN transistors 1735 25 Silicon Planar Transistors PNP TO -18 2N2906 0.50 2213702 0.60 T4 26381T0081 Eqvt. T1843. BEN3000 0.60 T5 20382T0082 27peach,25-99261, 1736 25 Silicon Planar NPN Transistors TO -5 B1,1'50/51/52 TO 20344B0044 100 UP 20p. U37 30 Silicon Alloy Transistors 130-2 PNP 0C200, 28322 0.60ELECTRONIC SLIDE -RULE T7 20345B0045 1738 20 Fastwitching Silicon Trans. NPN 400 11H. 2N3011 0.50The MK Slide Rule, designed to simplify Elec- T8 20378 0678 0.50 T9 2N1302 CADMIUM CELLS 1739 80 RF. Germ. PNP Transistors 2N1303/5 TO -5 tronic calculations features the following scales: - 10399A of andWavelength. TIO 20417 AF117 ORP12 489 1740 10 Dual Transistors 6 lead TO -5 2N2060 0.50Conversion Frequency ORP60, 0 RP61 40p each Calculation of L, C and to of Tuned Circuits. All 609 each Pak 1741 25 RF Germanium Transistors TO -6, 0C40, NKT72 0.50Reactance and Self Inductance. Area of Circles. GENERAL PURPOSE 1742 10 VHF Germanium PNP Transistor. TO.1 NKT667, AF117 0.50Volume of Cylinder.. Resistance of Conductors. 2N2060 NPN OIL. DUAL 0.50WeightofConductor..DecibelCalculations. TRANS. CODE DI699NPN SILICON SWITCH-U43 25 Oil. Trans. Plastic TO -18 A.F. BC113/114 Angle Functions. Natural Logs and 'e' Function.. TEXAS. Our price 265 ING TRANS. TO -1/1 044 20 SU. Trans. Plastic TO -5 BC115/NPN 0.60Multiplication and Division. Squaring, Cubing Slid. TO 21706/8. MT - 1.00 each. 29/28/95A. AllusableU45 7 SA SCR. TO66 up to 600PIV and Square Roots. Conversion of kW and Hp. devices no open or short A must for every electronic engineer and enthusi- Code No's. mentioned above are given as a guide to the type of device inast. Size: 2 cm x 4cm. Complete with case and 120 VCB MIXIN DRIVERcircuits. ALSO AVAIL- Price each: 13135 TRANSISTOR. Sim.ABLE in PEP Sim. tothe PH. The devices themselves are normally unmarked. instructions. 88X21 & C407, 2N18932N2906, BCY70. When FULLY TESTED ANDorderingpleasestate SILICON PHOTO TRAN- INTEGRATED CIRCUIT PAKS CODED ND 120.1.24preference NPN or PNP. SISTOR. TO -18Lem end 179 each. TO.5 N.P.N. 00 hPN Sim. to BP X25 and P21. Manufacturers "Fall Outs" which include Functional and Part -Functional Units. 25 up 169 each. 20 For 0-50 BRAND NEW. Fulldata These are classed as 'out -of -spec' from the maker's very rigid specification., but 60 For 1.00 available.Fully guaranteed. are Ideal for learning about 1.C's and experimental work. 100 For 1.75 811.trans.suitablefor Qty. 1 24 25.99 100 up Pak No. ContentsPrice Pak No. ContentsPrice Pak No. ContentsPriest P.N. Organ. Metal TO -18 500 For 7.60 Price each 459409869 Eqvt. ZTX300 69 each.1000 For 1300 1.71000 -12 x 74000.50 U1C46 x 7446 0.50 17IC86 x 7486 0.54)- Any Qty. 171001 -12 x 74010-50 U1C47 =5 x 7447 0.60 1J1C90 = 5 x 7490 0.50- SIL. G.P.DIODES by F.E.T.'S 171002 =12 x 74020-50 U1048 =5 x 7448 0.50 111091 =6 x 7491 0.50- 300mW 30..0-50 UIC03- 12 x 74090.60 me6e-12 x 74500.60 UIC92= 5 x 7492 0.60 2N3819 06p2E5455 50p 0I004-12 x 74040.50 1.11051 =12 x 74510.60 UIC93=6 x7493 0.50 POWER 40PIV(Min.)100..1.50 2913820 5092N5409 40p Sub -Min. 500..5-00 U1605-12 x 74050.60 U1613=12 x 74530 60 U1094= 5 x 7494 0.60 2N3821 369BFV/10 400 U1C06 -8 x 7406 0.50 1.7105412 x 74540.50 01085 =5 x 7495 0.50 TRANS Full Tested 1,000. 9-00 MPF105 Ideal for Organ Builders. 2N3823 SOp 409 U1007 - x 7407 0.50 151060 = 12 x 74600 50 UIC96 -5 x 7496 0.60 BONANZA! UIC10..12 x 74100.50 010708 x 7470 0.50 1710100=x 74100 0.60 1.71C13 -8 x 7413 0.50 171072 = 8 x 7472 0.50 UIC121 = 5 x 74121 0 . 50- GENERAL PURPOSE GERM. PAP 171020 - 12 x 74200-50 171C73 = 8 x 7473 0.60 1710141 = 5 x 74141 0.60 Coded GP100. BRAND NEW TO.3 CASE. POSS. NEW EDITION 1971 UIC30 =12 x 74300.50 UIC74 = 8 x 7474 0.50 1710151=5 x 74151 0.60 REPLACE., -0C25-28-29-30-35-136. NKT 401-403- 171640=12 x 74400-50 171075 = 8 x 7475 0.50 UIC154 =5 x 74154 0.50 404-405-406-430-451-462-453.TI9027-3028, 2/4260A, TRANSISTOR EQUIVALENTSUIC41 x 7441 0.50 171076 =3 x 7476 0.50 01C193 =5 x 74193 0.50 2N4513A-457A-458A, 2N511 A & B. 20220-222, ETC. BOOK. A complete ems. reference171042 -5 x 7442 0.50 1.7IC80= 5 x 7480 0.50 U1C199= 5 x 74199 0.60 VCBO 80V VCEO 60V IC 10A PT. 30 WATTS Hfe and equivalents book for European,0I048-6 x 7443 0.50 171C81= 5 x 7481 0.50 30-170. American and Japanese Transis-171044=5 x 7444 0.50 171C82 =x 7482 0.50 UICXI =25 Assorted PRICE 1-24 25-99 100 up tors.Exclusive to BI-PAK 009UIC45 =5 x 7445 0.50 U1683 -5 x 7483 0-50 74's 1.50 Sep each each. 439 each 40p each Packs cannot be split, but 25 aaaorted pieces (our mix) is available as PAK UIC Xl. SILICONHighVoltage250V NPN TO -3 case. G.P. Switching & Amplifier Applications. Brand new Coded R 2400 2113055 A LARGE RANGE OF TECHNICAL BI -PASS NEW COMPONENT SHOP NOW OPEN WITH A VCBO 260/VCEO 100/IC 6A/30 Watts. AND DATA BOOKS ARS NOW HFE type 20/fT 6MHZ. 116 WATT SILAVAILABLE EX. STOCK. WIDE RANGE OF ELECTRONIC COMPONENTS AND OUR PRICE EACH : POWER NPNSEND FOR FREE LIST. ACCESSORIES AT COMPETITIVE PRICES - 1-24 25-99 100 up509 EACH 509 459 40p 18 BALDOCK STREET (A10), WARE, HERTS. SILICON 50 WATTS MATCHED NPN/PNP TEL. (STD 0920)61593. ADI6I/162 pig/. BIP 19 NPN TO -3 Plastic.BIP 20 PNP. Brand new. open MON.-SAT. 9.15 a.m. to 6 p.m., FRIDAY until 8 p.m. 31/P COMP GERM TRANS. VCBO 100/VC110 50/IC 10A. HEE type 100/ft 3mHZ. OUR LOWEST PRICk OF OUR PRICE PER PAIR: All mail orders please add 10p post and packing. 659 PER PAIR 1-24 pea. 1109 15-99 pre. 669 100 pre. 50p Send all orders to BI-PAK, P.O. BOX 6, WARE, HERTS.

204 PracticalElectronics March 1973 the lowest prices! 74 Series T.T.L. I.C's BI -PAN STILL LOWEST IN PRICE. FULL SPECIFICATION BI-PAK DO IT AGAIN! GUARANTEED. ALL FAMOUS MANUFACTURERS

1 15 110. 1 15 OD. SN7400 33 14 12 SN7489 £3.55 t5 25 1344 SN7401 IS 14 12 SN7490 047 144 0-111 50W pk 25w (RMS) SN7402 15 14 13 SN7491 1144 015 01111 SN7407 IS 14 32 SN7492 047 044 118 SN7404 IS 14 32 SA17493 147 514 130 SN7403 15 14 12 SN7491 II 77 074 048 0-1% DISTORTION ! SN7406 35 31 11 SN7493 177 0-74 018 HI-FI AUDIO AMPLIFIER SN7407 -35 31 Xi 5547196 117 ON 71 SN74041 -II 17 ,111 SN74100 1145 1140 II 53 SN7409 11 17 I/ 55474104 1117 011 OM SN7410 IS 14 II 5N74105 1117 044 1111 SN7411 25 -24 13 S5474107 441 1-30 31 5N74I2 35 31 NI 5N74110 0-55 153 SS THE AL50 SN7413 11 -II 34 5N74I II 1113 II IS II II S547416 43 Alb III S5474118 1144 1115 010 SN74I7 13 -Of 31 SA174119 II 35 11 25 LI 10 * Frequency Response 15Hz to ONLY 5547410 -15 14 12 SN74121 544 37 34 SN7412 -SO 48 -45 S5474122 1146 11-341 11 II 100,000-1dB. SN7423 SO 41 .45 SN74123 1201 12 71 1240 5547425 .511 41 43 55474141 047 144 053 £3.25p each SN7427 -45 41 es 5N74141 II SS 1110 11 35 * Load -3, 4, 8 or 16 ohms. 5547428 711 45 44 55474130 1300 11 74/ 12 50 SN7430 15 14 12 55474131 11 40 015 110 * Supply voltage 10-35 SN7431 -45 -42 AO 5N74133 LI 20 II II 015 SN7433 10 75 71 554741 34 II 4141 (170 1144 * Distortion-better than -1% at Volts. SN7437 44 42 40 55474133 11-01 II 34 II -31 5547438 44 42 40 55474136 1145 11 30 11 20 1KHz. SN7440 -15 14 12 SN74137 11111 11.10 11.74 SN7441 47 44 SO 55474160 1110 LI 70 1141 * Overall size 63mm x 5547442 47 14 SN74161 1100 11 70 11411 * Signal to noise ratio 80dB. 105mm x 13mm. SN7447 1130 1125 1151 55474161 14415 L375 1310 SN7444 11 31 II 25 1 IS SN74163 a44 13 75 L3 SO Tailor made to the most stringent specifications using top quality components S547441 11.11* 1177 II 75 SN74164 12.38 12 15 12 10 SN7446 417 014 10 55474163 12-23 12 30 11 IS and Incorporating the latest solid state circuitry and ALSO was conceived to fill SN7447 11 441 17 15 SN74166 13 SO 13 25 1314 the need for all your A .F. amplification needs. SN7448 1140 17 45 SN74174 12 31 12 20 12 111 FULLY BUILT - TESTED - GUARANTEED. S547430 13 14 12 55474174 1144 11 51 1140 S547411 IS II 12 55474176 12 SS 1101 11 30 SN7433 15 -14 II SN74177 12-511 1141 12 31 5547414 15 14 12 55474180 1244 11 *0 11 411 STABILISED POWER SN7460 15 14 ,2 SN74111 13 61 1544 ass SN7470 21 21 24 554741112 1241 1110 11 40 MODULE SPM80 5N7472 21 26 024 55474184 13 511 L3 25 L341 SN7473 -37 35 132 55474190 1115 11 10 1163 AP80 Is especially designed to power 2 of the AL50 SN7474 37 35 132 55474191 1110 1115 11 OS 5547471 55474191 1115 11 10 1113 Amplifiers, up to 15 watt (r.m.s.) per channel simul- 45 .43 542 taneously. This module embodies the latest components SN7476 41 31 30 5N74195 1200 ITN 11 75 5547400 47 44 555 SN74194 127 12 410 125 and circuit techniques Incorporating complete short SN7481 II is LI IS II le SN71195 1240 11 141 11 SO circuit protection. With the addition of the Mains Trans- SN7402 047 044 043 S1,74196 11 10 II 71 1140 former MT80, the unit will provide outputs of up to 1-5 SN7483 le II 1143 015 SN74197 III SD 11 71 11/4 amps at 35 volts. Size: 63mm x 105mm x 30mm. SN7404 1100 015 514 55474198 L5.50 1.540 14 SS These units enable you to build Audio Systems of the highest SN7415 1341 13 SO 1.344 55474199 LS 511 1.5 *4 14 50 quality at a hitherto unobtainable price. Also ideal for many SN7486 32 031 30 other applications Including:-Disco Systems, Public Address, Intercom Units, etc. Handbook available, 10p PRICE £2.95, ROCK BOTTOM PRICES LOGIC DTL 035 Series I C. LINEAR I.C. e-FULL SPEC. Type Prke TRANSFORMER BMT80 £1.95 p. & p. 25p. Prke No. I-24 23-11100 ep Type So. 1-24 25-11 100.4 BP910 lip rap IN BP912 BP201( -SI 201( 111, 51, 45, 13, lip lip BP701( -SI 701( 61p 50, 45p 13P931 13p I2p lip STEREO PRE -AMPLIFIER TYPE PA100 5P97' 13, 129 lip 13P702(--SI 702( 4.8p 511p 45, BP702-71702 53, 45, BP936 13, 12p 1 1p Built to a specification and NOT a price, and yet still the greatest value on the market, MV 13p 12p 1 1p B P709-72709 31p 349 311, BP944 the PA100 stereo pre -amplifier has been conceived from the latest circuit teconiques. P709 P-5. A709( 36p 349 31, 15P943 25p 24p 22, Designed for use with the AL50 power amplifier system, this quality made unit incorporates BP710-72710 44p 42p 41p 6P946 12p lip 10, no less than eight silicon planar transistors, two of these are specially selected low noise 6P948 25, 24p 22, BP711-,A711 43p 43, 4415 NPN devices for use in the input stages. BP741-7274I 44p SO, FIP931 15p 441, 55, 75, 5P962 Three switched stereo Inputs, and rumble and scratch filters are features of the PA100, A701( A703( 28p 21, 24p 13, IIp 10p 11P9091 4110. !Sp 3Sp which also has a STEREO/MONO switch, volume, balance and continuously variable T A A263-70p 11.11p 35p bass and treble controls. 75p 70, 15P9094 4111, 314 35p TA A 293-141, liP9097 111, 38p 35p TAA330 1711p 151110 150, SPECIFICATION St.% F A1000 243 0P9099 40, 36p 35, lie one.to.y herntnedlolitlial(V rOr Frequency Response 20Hz - 20KHz f 1dB quan10 y(el, 1 arperquantily pm, Harmonic Distortion better than 0.1% on4 ppli, moon (DTI 930 Sent. onlyi Inputs :1. Tape Head 1-25 mV into 50K 0 2. Radio, Tuner 35 my into 50K 0 3. Magnetic P.U. 1.5 my into 50K 0 NUMERICAL INDICATOR TUBES All input voltages are for an output of 250110/. Tape and P.U. Inputs equalised to RIAA curve within 4, 1dB. from 20Hz to 20KHz. 15dB at 20Hz Treble Control * 15dB at 20KHz MODEL cDee 0E116 9015F Minitron Filter. : Rumble (High Pass) 100Hz ill Scratch (Low Pass) 8KHz Signal/Noise Ratio better than - 65dB Anode voltage (Vdc) 170m1n 175min 5 Input overload + 26dB AllIndicators Supply + 35 volts at 20mA Cathode Current (mA) 2.3 14 8 0.9 + Decimal Dimension. 292mm x 82mm x 35nun Numerical Height (mm) 16 19 9 point. All side ONLY £11 95 viewing.Full COMPLETE KIT COMPRISING 2 AL50's, 1 Tube Height (mm) 47 32 22 data Tor all SPECIAL types available SPM80, 1BMT80 & 1 PA100 ONLY £2300 FREE p. & p. Tube Diameter (mm) 19 19 12 wideon request. I.C. Driver Rec. BP41 orBP41 or BP47 AU prices quoted in new pence Giro No. 388-7006 141 141 Please send all orders direct to warehouse and despatch department 11!1f PRICE EACH 41.70 111-66 111-P0

ETL MICEOLOGIC CIRCUITS DUAL IN LINE SOCKETS. 14 & 16 Lead Sockets for use with Pries sash Rpoly TO -5 cam1-24 25-99 100 up DUAL-IN-LINN IBC's. TWO Ranges PROFESSIONAL & NEW LOW COST. uL900 Buller Up Up t74 PROF. TYPE No. 1-24 25-39 100up. uL914 Dual 21/p T80 14 pin type SOP 2711 Up HI-PAK tote Bhp SSp 87p T8016 36p 42p SOP P.O. BOX 6, WARE HERTS uL929J-K 50p 47p 464 LOW COST No. Postage and packing add tOp Overseas add ertra for Date and Circuits Booklet forIC's BPS 14 - LIP MO 11.4 Minimum order 50n Cash with order please. Peke 7p. BPS 16 lip 14p lip Guaranteed Satisfaction or Money Back

PracticalElectronics March 1973 205 kii i TRANSFORMERS d_7 meet the precision

'INVADER'IkaRDuEak-Ps 30 36 Precision 52 instrumentssuppliedwithstandarddetachable 52 copper chiselface bits. Standard temp. 360°C at 19/23/27 67 watts. Special temps. from 250°C/410°C. 82

For perfection in soldering 11076 1646 BIT SIZE 1/4" BIT SIZE 3/16" 6.34 mm Dia 4.75 mm Dia 27 watts 23 watts. £.2.18 £2.12

1706 BIT SIZE 1/8" 111050.25 12 76,5.7.440-12V at 0 25A 2 0.85 22 3.2 mm Dia 213 10 05 I 0 8 3 5 I 5 I 0-12V at 0 -SA 2 I.0122 71 2 1 I 0 7 0 6 4 5 70-12V at IA r 2 1.33 22 19 watts /9' 18 4 2 2 4 8'3 7 0 7 00-12V at 2A 2 106 36 70 6 3 3 12 102 -7 6 ,8 60-12V at 3A 2 1.24 42 L1'96 108 8 4 5 4 100'03 820-12V at 4A , 2 2.4852 72 10 5 6 3 79108.1020-12V at SA 2 2.9452 17 16 8 7 8 12-1 9 5 , 1020-12V at 8A 2 4.54 52 115 20 10 II 13 12.1 11 4 10 20-I2V at 10A 2 5.78 67

187 30 15 1612 13 3 . 12 1 12 1 0-12V at ISA 2 10.6782

226 60 30 34 0 170 14 5 12 50-I2V at 30A 2 19.61 30 VOLT RANGE Ref. Amps. Weight Size cm. Secondary Taps P&P No. lb oz L p

111 05 1 4 8.3 37 4.90-12-15-20-24-30V 1 01 22

79 1.0 2 0 70 6.4 60 1.3536 3 20 3 2 89 70 76 201 36 20 30 4 6 10.2. 8'9 8.6 2.48 42 21 40 6 0 10.2 100 8.6 294 52 51 50 6 8 12.1 ,10.0 366 52 117 60 7 8 12.1 10.0<10-2 4.36 52 88 8.0 10 0 14.0 n 11.7, 10.0 5 64 67 89 100 12 2 140,102. - 11.4 7.14 67 50 VOLT RANGE Ref.Amps. Weight Size cm. Secondary Taps P & P No. lb oz L p

I 02 0-5 II 7.0 ,7.0 5.7 0-19-25-33-40-50V 1.3330 03 1.0 210 8.3 x 74 .<7.0 1.9436 04 2.0 5 0 04x 8.9 -8.6 2.69 42 05 3.0 6 0 02 x 10-2 -8.3 3.65 52 06 40 9 4 2-1 -11.4-I0.2 4.8352 07 6.0 12 4 2.1 z I 1.1x 13.3 7.14 67 18 80 18 9 3.3 13.3 x 12-1 9.32 97 19 10-0 19 12 6.5 11.4 15.9 11.68 97 60 VOLT RANGE the Ref. Amps. Weight Size cm. Secondary Taps P&P No. lboz I p 124 0.5 2 4 84 x9 5 x6 7 0-24-30.40-48-60V 1.3536 126 1.0 3 0 8 9y 7 6>:7.6 1.88 36 127 20 5 6 0 2< 8 9 x8'6 .. 2.94 42 Don't take chances. 125 30 8 8 1.9 x 93 .,10 0 .. 4.48 52 123 40 10 6 1 4- 9 5 11 4 5.78 67

We don't.All our 110 6.0 1612 3 3 x 12 1 ., 12 1 .. 847 82

122 10.0 2 AOCOLA Instruments 23 6'5 -12 7 16 5 - - 13 85 are of impeccable qual- LEAD ACID BATTERY CHARGER TYPES Ref.Amps. Weight Size cm. P & P ity. You can depend No, lboz L p on ADCOLA day after day. IS 1.5 I 9 7.0 x6.0 -6.0 1.3430 5 4.0 3 11 10.2 ,7-0 8.3 Please note, these 203 42 That's why they're so popu- 86 6.0 5 12 10.2 ,8.9 ,8.3 units do not in- 3.0752 larYou get good service ... 146 8.0 6 4 8.9 . 10.2 10.2 elude rectifiers 3.49 52 50 12.5 11 14 13-3.,10-8 x 12.1 5.20 67 relia bility...from our famous All ratings are continuous. Standard construe ion: open with solder ther mally controlled ADCOLA tags and wax impregnation.Enclosed styleso order. FULL SPEC. TRANSISTORS Element and the tough steel BC107/108/109 9.0p each 2N 305568p each AD 161/162 60p pair construction of this production 25+ 7p +mica and bushes+ mica and bushes tool. ADCOLA day after day. 100+6.5p 25+ S5p 25+55p 500+6p 100+45p 100+50p Minimum order 10 500+ 40p 500+45p Send for NEW pieces this range. 1000+ 40p catalogue today AVOMETERS - MAINS KEYNECTORYNECTOR ELECTROSIL RESISTORS CABILIAOE VIA HU ADCOLA PRODUCTS LITI ADCOLA HOUSE GAUDEN ROAD LONDON.SW4 6LH Regd. No. 442782 ENGLAND Postage,packing paid on orders over (2. underE2.add £0.10 BARRIE electronics Models required 11 MOSCOW ROAD, QUEENSWAY Enclosing WO or cheque for Name LONDON W2 4AH TeI:O1-229 6681/2 Address NEAREST TUBE STATIONS BAYSWATER QUEENSWAV PE2

206 PracticalElectronics March1973 B(sales]

SOLID STATE TACHOMETER SPECIAL OFFER! Functionallystyledforunder or AUTO BURGLAR ALARM overdashboardinstallation,this PLUS "POP -OUT" CIGARETTE LIGHTER electronictachometerfitsall4 - Designed for easy installation on any car (whether 6V or 12V) cycle,4 -cylinder,or 2 -cycle, 2 - cylinder I2V vehicles.Negative or this device activates the horn when a theft is attempted of positive earth. Calibrated white on equipment or personal belongings. This neat unit reacts when black 0-8,000 r.p.m. in100 r.p.m. the vehicle is disturbed or rocked and continues its warning divisionstogetherwithsetable for 15 seconds after tampering. The sensitivity of the device "danger" line, simple installation isadjustable and controlled by a separate ON/OFF panel which can be located wherever convenient. 2 screws, 4wires.80mm (3in) Supplied with diameterdial, 50mm deep. On connecting wires and screws in attractive bubble pack, con- *no adjustableanglebracket. Sealed taining installation instructions and diagrams. ISO 65 20rnm black crackle finish. plus panel 65 45 20mm. f2. I 0 FOR BOTH £6.86

ANTAVOX STEREO LOUDSPEAKER SYSTEM 420E5 MICROSCOPE These high quality speaker enclosures are made of Anextremely modestly priced yet tough black moulded plastic and have been designed efficient microscope capable of magnifi- for fitting on to almost any vehicle surface. The cation up to 750 times with clear sharp smart louvred fronts are silver trimmed and house heavyduty5in(125mm)ceramic loudspeakers images. Thismodel is ofthe self - rated at 3/5 watts.8 ohms impedance.Already illuminatingtypeandincorporatesan wired with generous length connecting leads and sup- easily rotable four -position turret mag- pliedinpacks of speaker pairs complete with fixing nifying lens with rack and pinion focusing. screws. Each cabinetmeasures 190 105 165mm; The crackle black metal body houses the 055kg. batteries foradjustableillumination. 1052 FADER CONTROL Packed in carton with built-in carrying Neat, custom-made appearance slide fader control for balance of front and rear speaker volume. Simulated wood finish panel which can be quickly fitted below car dash. Sup- handle and full notes for user. A sample plied with generous connecting cable and fitting screws. Will suit 4, 8, 16 ohm instal- slidealsoprovided. 105mmatbase;

lations. 10038 30mm (including knob but excluding fitting bracket). 180mm high; 040kg. All for E4.70 £4.95 G5555 PROFESSIONAL STEREO HEADPHONE "SPRITE" LIGHTWEIGHT STEREO HEADPHONE An outstanding achievement followinglengthy Lightweight materials are skilfully usedin the con- development by one of the world's leading audio struction of this model in black crackle moulding and manufacturers, the T.T.C."Sprite" offersthe kid -soft leathercloth with contrasting bright metal. following specification: Extreme lightness (only 150 grammes-,5oz); Each ear pad houses a highly efficient 60mm reproducer Instant wearing adjustment with sliding unit and features ear muffs removable for cleaning. earpieces and flexible headband; 10 self -coiled lead plugs fitted. Highly efficient Mylar reproducer units; Removable, washable foam padded ear muffs; Freq. Response: 20 20,000Hz.Impedance: 4-16 ohms. 3 metre lightweight lead with stereo plug fitted Sensitivity:1 10dB. Power: 0.5W. Weight: 039kg. Frequency Response: 30 13,000Hz. Sensitivity: 105dB.Impedance: 4 16ohms.Power: 0-2W. £9.25 Weight: 015kg. £2.25 ADASTRA "HI -TEN" 10in LOUDSPEAKER K2006 HORN CONE TWEETER The British made "Hi -Ten" unit has also had minor Neat 3in (75mm) pressure driven tweeter with spun metal cone improvements oflateincludinganextendedtop giving excellent H.F. response with up to 10 watts load.Designed response and a new matt black chassis finish.This for fitting into a rebate (80mm dia.) with fitting by four corner holes full range 10in. loudspeaker handles up to 10 watts on outer flange. Screws provided. Polarised connections. 8 or 15/16 withconvincingallroundperformance andtotal ohms, impedance matching. I 65 reliability.A highfluxceramic moulded magnet Freq. Resp.: 1,500-- I 6,000Hz . Crossover Freq.: 3,000Hz. Sensitivity: 104d B. keeps the unit compact. An idealunit forallfull Size: 85 85 80mm. Weight: 0.30kg. Impedance: 8 or 16 ohm versions. range music, audio and monitoring purposes and K4004 VARIABLE CROSSOVER particularly suitable for column enclosures.Available Continuously variable from 2,500Hz to infinity in 8 or 15 ohm versions. f2-70 and matching any Bass/H.F. unitcombination Frequency Response: 40 --13,000Hz. Bass Resonance: 70Hz.Power Handling: this variable crossover is housed in a two-colour IOW. Impedance: 8 and 15 ohms.Flux Density: 10,000 lines.Voice Coil: metalcase with marked andpolarisedcon- 25mm (lin.).Baffle Aperture: 228mm (9in).Fixing Centres: 244564mm. nections. 102 66 55mm. Dimensions: 2558 . 9I-9mm. Weight: 0.91 kg (21b). £1.05 ALL THREE FOR£5.20 rMMMMMMMMMM INN INN All orders value a or over post free. Other orders please add 10p P. & P. We only sell new productsdo not confuse with "seconds" orIName surplus stock. Because of our keen prices we regret the prices apply to U.K. and B.F.P.O. addresses only.Please fillin the coupon and send with 10p (refundable on ordering) for catalogue. IAddress ALL CALLERS WELCOME To G.S.P.K. (Sales) Limited, Dept. E.E., Head Office: Hookstone Park, Harrogate, Yorkshire HG2 7BU. 11141;n. to Fri. 9-5. P.E.

16NM ME IIMI INN El MN INN ISO

PracticalElectronics March 1973 207 STANDARD dN CUSTOM- BuUsl ILCTAAL Ui NDSI TORaun frid EELECTRONIC Es S ands DISTRIBUTORS FOR A.K.G. HIGH QUALITY MICROPHONES

SA25-SA35-SA100 OTHER SAXON PRODUCTS... LOW-PRICED AUDIO MODULES FOR 120 WATT HEAVY DUTY MODULE El 3.90 + 20p carr. or with DOMESTIC and COMMERCIAL USE Featuring a rugged class A driver stage, this module will run supply 118.95+40p Carr. from all our mixers etc., and most other makes of mixer.It delivers 120W into an eight ohm load and employs 4 TO3 1111-"1.41111101.11...111., can (I 15W) output transistors.

SPECIFICATION Power output 120W into 8 ohms Freq. response 20-20,000Hz ± 2dB Input sensitivity 200mV into 10K Construction Fibreglass board Size Bin x 4in x 4in (sin with supply) Low distortion parallel push-pull output stage. NEW: 160 act version & supply L27-90

THESE THREE MODULES HAVE ENJOYED UN- SINGLE CHANNEL SOUND/LIGHT CONVERTER PARALLELED SUCCESS DURING THE FIRST FEW This compact and reliable unit operates from amplifiers with MONTHS OF THEIR BEING MADE AVAILABLE TO outputs from 5-100W.Does not impose a heavy load on THE GENERAL PUBLIC. WE ARE PLEASED TO the amplifier, or,if connected in the wrong polarity, cause ANNOUNCE THAT WE CAN NOW OFFER FAST any damage. as with some units. DISPATCH ON MOST OF OUR ADVERTISED ITEMS, INCLUDING THESE THREE MODULES. Operation is simplicity itself and the unit is fully fused.The carr. unit is supplied to function from bass notes but may easily be free converted to respond only to treble or mid -range notes by carr. SA2522.95 the addition of components costing less than 5p. free 25 WATTS R.M.S7 transistors, 7 diodes 2890 carr.

free SA3524.45 ;;..",',7' 35 WATTS R.M.S. 7 transistors, 7 diodes THREE CHANNEL SOUND TO LIGHT UNIT Handling the total of 3,000W (3kW) this unit isnique for its price in that not only bass middle carr. and treble but also master controls are provided.uTwo amplifier sockets eliminate the need for SA100 210°90 free split leads, etc.Supplied in tough white steel case with a blue hooded cover.Fully guaranteed. £19.75 carr.30p 100 WATTS R.M.S. I I transistors, 6 diodes ALL THREE MODULES HAVE OPEN AND SHORT CIRCUIT PROTECTION, AND THE SAI00 IS PROOF MONO VERSION E650, carr. 20p (As illustrated below. S.A.E. details. 9V operation) 5'80 30pcart". AGAINST OVER -DISSIPATION AND FAULTYIN- OUTPUTS UP TO IV RMS SAXON STEREO DUCTIVE LOADS. CONTROL UNIT ONLY ADVANCED DESIGN TECHNIQUES MAKE THESE EXTRAORDINARILY LOW PRICES POSSIBLE.

BRIEF SPEC. FOR ALL THREE MODULES Two decks, and full headphone monitoring.The unit is mains operated and measures 170) r Sin Freq. response 20 40,000Hz I dB 4in deep and is finished with a smart white on black facia.The controls are: Left/Right deck I kHz fader, volume, bass, treble, headphone selector and volume, microphone volume, bass, treble, Distortion 02% at mains on/off.THIS IS A MUST FOR THE HOME BUILT HIGH QUALITY DISCO- Loads 4 to 16 ohms THEQUE AN OIS COMPARABLE TO UNITS AT OVER TWICE THE PRICE. Quiescent current 15mA Noise Better than -75dB Supply voltage 25-45V, SA25/35 COMPLETE AMPLIFIERS 40-70V, SA100 THE CS 100.E34.90 carr. free Size 44in 4in lin (SA100) 4in Sin I in (SA25, SA35) This versatile unit is now available in a black vynide case and so represents even better value than ever, Circuits, connecting instructions and application data delivering speech and music powers of up to 100W are supplied free with all modules. R.M.S. and continuous signal outputs of 70W. Two individually controlled inputs with wide range bass and treble controls. Ideal for small groups. D.J's, etc POWER SUPPLIES FOR THE SA25/35 and SA100 AUDIO MODULES The SAXON 100.E48.50, carr. free. 1.0 L 4 4- With an R.M.S. output of 120W speech and music, PU45 Unstabilised supply for 2 SA25/35's, L4.90. 100W continuous power, four individually controlled PU70 Unstabilised supply for one or two SA100's, ' F.E.T. input stages and wide range bass and treble 0.75, carr. 40p SAXON controls, this amplifier has established itself asa MT4S Transformer for above, heavy duty, L2.85, unit offering quality and reliability at low cost. carr. 20p PS4S Stabilised module for 2 SA25's or two SA35's, LOUDSPEAKERS British made bargains !!! L3.50, carr. free I2in 25W 8/15 ohms 0.95, carr. 30p. 15in 50W 8/15 ohm, [1440, carr. 50p. MT70 Transformer for PS70, L4.90, carr. 40p PS70 Stabilised supply module for one or two I 2in 40W 15,000 gauss magnet system 8/15 ohm, t11.50, carr. 40p. SA100's, L4.90, carr. free A.K.G. MICROPHONES suitable for disco, group or general P.A. use SEND S.A.E. FOR DI I DHL r.r.p. LI I, our price 0.45 post free. OUR A.K.G. PRICE ALL MODULES ARE BUILT ON GLASS FIBRE P.C. D190C High Z r.r.p. E2150, our price LI7.45 post free. LIST. DISCOUNTS BOARD DI 000C 24 ct. gold place r.r.p. L37, our price 432 post free. ON ALL MICS.

CALLERS AND MAIL CALLERS ONLY: BUSINESS TERMS OF BUSINESS: C.W.O. or ORDER: OUR NEW DISTRIBUTORS. HOURS: C.O.D. (35p extra). All cash in regd. 351 Whitehorse Road CIRCLE SOUND 9.30 a.m. to envelopesplease!Telephone orders Thornton Heath, Surrey 328-330 The Banks 5.30 p.m. to our CROYDON BRANCH. TRADE Tel. 01-689 3685 Rochester. AND EXPORT ENQUIRIES Medway 404199 INVITED

208 PracticalElectronics March1973 PE OUR TRANSISTOR 'r HISseems a good time to reveal our own secret suspicions Iconcerning the origin of the transistor.We admit that for long we have had an irresistible feeling that this device was in fact conceived with the private constructor expressly in mind. Yes indeed, and plenty of evidence points this way- other important users and impressive applications notwith- standing. Forget, for a moment or two, those epic moon journeys monitored on colour television. Forget (if you can) those ubiquitous transistor radios.Forget those prodigious com- puters-and those in -vogue status setting personal appurten- ances like pocket calculators and solidstate wristwatches. Instead, reflect upon what the transistor has meant to us as private constructors and experimenters. For we as much as any other body of individuals have cause to be jubilant and grateful in respect of that revolutionary technological break- through a quarter century ago. We suggest that if the trio of research physicists at Bell Labs had been working to a specification drawn up with the private constructor's interests foremost in mind, they could hardly have done better. Those readers able to cast their minds back to the pre -transistor days when the valve ruled the roost will certainly be appreciative of the transformation set in train by the solid state amplifying device. It ushered in an era of expansive amateur activities, by bringing within the private individual's reach, literally to his table top, previously undreamed of electronic techniques. By comparison with the thermionic devicesit was going to replace, the transistor when it made its debut seemed so ridiculously simple to handle, so small and undistinguished in appearance, so undemanding in power, as not to be true. Not that there were no headaches for the average constructor and experimenter initially, when trying to get to grips with strange new concepts involving solid state physics, with a little chemistry and metallography thrown in.It was rather a traumatic experience trying to adjust to the transistor's idiosyncrasies. (An h.t. line of minus 6 volts-what nonsense was this?Though we got our potentials right once again Editor when the npn version arrived.) First attempts to make prac- F. E. BENNETT tical use of the strange component were accompanied with Editorial trepidation, for burnt -out transistors weren't uncommon in D. BARRINGTON those pioneering days. G. GODBOLD littleteething S. R. LEWIS B.Sc. Seen now inretrospect,these were but Art Dept. troubles. The advantages and rewards arising from the solid J. D. POUNTNEY Art Editor state device were soon made apparent. Without the transistor J. A. HADLEY and its descendants amateur activity would never have reached R. J. GOODMAN the advanced technical stage, nor have been able to embrace S. W. R. LLOYD such wide and diverse applications asit does today. Un- Advertisement Manager doubtedly the basic simplicity of constructionis the great D. W. B. TILLEARD single factor which has stirred up popular interest in solid Phone: 01-634 4202 state electronics. It is now an ideal sparetime hobby which P. J. MEW can be pursued without difficulty in the home. Phone: 01-634 4210 Yes, constructors and enthusiasts all, there is cause to be C. R. BROWN Classified exuberant. And don'tforget, without thetransistor there Phone: 01-634 4301 could hardly be PRACTICAL ELECTRONICS. So we all owe a Editorial & Advertising Offices: Fleetway House, Farringdon St., vote of thanks to Messrs. Bardeen, Brattain, and Shockley. London EC4A 4AD And surely no true enthusiast will dare deny that our sus- Phone: Editorial 01-634 4452 picions are well founded.-F.E.B. Advertisements 01-634 4202

PracticalElectronics March1973 209 Hill Tape Link By P S EWER rHERE must be many readers who possess a tape the record amplifier isfed via a resistor and the Irecorder whose quality does not match that of relay contacts to the record/replay heads. It is also the rest of their hi-fi system and who would like to fed to the meter circuit which can also be used to improve it to save the expense of buying a com- read the bias voltage. pletely new deck. The resistor between the record amplifier and the This article describes how to convert a reason- head is used to achieve constant current drive. able quality deck to hi-fi by renewing the electronics In the record mode the relay contacts connect the and the heads whilst retaining the original tape trans- heads to the record amplifier. The bias oscillator is port system. All that is required is a tape deck of on and feeds the erase heads. Two 50 kilohm potentio- reasonable quality, the author using a Collaro Studio. meters (VR7 and VR107) are used to control the Full constructional details relating to the deck will bias. When only single track operation is selected be given. then the unused outpUt of the biasoscillatoris Sinceitisassumedthattheconstructorwill grounded via a 10 kilohm resistor (R42). already possess a high quality amplifier, this will not In the playback mode the output of the heads is be described. Microphone facilities are not included fed directly to the playback amplifier and then out because in the author's opinion these are best pro- via another DIN socket. vided by a comprehensive mixer.

OVERALL SYSTEM HEAD REQUIREMENTS A block diagram of the overall system is shown inFig.I. A six -pole three-way switchisused A tape recorder is only as good as its heads and to select either upper -track, lower track, or stereo to achieve the required performance heads of very operation (S3). A. relay (RLA) is used to control high calibre are essential. record and playback modes. The relay itself is con- The characteristics required for the record/ replay trolled by an external switch normally fitted to the head are tape deck. This switch is also used to control the 1. Low eddy current loss at high frequency so' that supply to the bias and erase oscillator, which is on a high bias frequency can be used both to avoid in the record position and off in the playback. interference (this being particularly important when A ganged potentiometer (VR6, VR106) controls recording stereo radio transmissions with its attend- the gain of the record amplifier which is fed from ant sub -carrier output problems), and to enable the the input signal via a 'DIN socket. The output of minimum pre -emphasis to be employed.

210 PracticalElectronics March 1973 SPECIFICATION..

System Distortion Quarter track stereo tape link intended for use in 1% at 0VU conjunction with a high fidelity system. Features include two level indicators, adjustable metered Signal to noise ratio bias, and single track mono operation 60dB weighted according to the CCIF charac- teristic and using low noise tape Overall Frequency Response 7f i.p.s.30Hz-17kHz Crosstalk i.p.s.40Hz-11.5kHz +1, -1.5dB 45dB 11 i.p.s.40Hz-6.5kHz +2dB Input Replay Characteristic 55mV r.m.s. to infinity at 10 kilohm CCIR 71- i.p.s. 7012S Output 31 i.p.s. 140pS 1 volt r.m.s. from near zero source impedance. i.p.s. 280p.S Protected againstaccidentalshort circuit

2. A well -engineered gap which is as close as pos- The erase head should be very efficient, requiring sible to the mechanical gap width. This results in a low input power and so causing minimal damping minimal gap losses at short wavelengths. of the oscillator tuned circuit. 3. The magnetic core should have a low coercivity The heads specified for the recorder fulfil these topreventmagneticsaturationoccurringwhich requirements and are manufactured by Wolfgang would reduce the signal-to-noiseratio and cause Bogen of West Berlin. They are obtainable in the second harmonicdistortion.This is particularly U.K. from Cole Electronics Ltd., the sole agents important at low tape speeds or when using low (see Components List for the address). noise tapes. On the playback side the important characteristics RECORD AMPLIFIER REQUIREMENTS are: A recording amplifier raises the level of the input 4. Low source impedance consistent with a high signal to an amplitude suitable for driving the head. output, which is required to enhance the signal-to- It must incorporate pre -emphasis to compensate for noise ratio. the high frequency fall -off inherent in the head to 5. A narrow gap width anda small gap depth. tape characteristic, and provide a constant current 6.A ripple free response at low frequencies. output to the head.

.-NA.A0C) 180k11

U = UPPER S = STEREO L. LOWER

MET ER

,

33kfL SET BIA U RECOR 101,11 log 50kfl 15 kfl

INPUT RECORD/ 'LAYBACK HEAD ERASE HEAD

%A.A.r.....ILURLA 4 SOkil 15kfl 330 pF JF 33krL SO +27V REC/PB. 0U RLA UT PUT BIAS 8 ERASE 4 OSC

4711

Fig. 1. Block diagram of thecomplete stereotape link

PracticalElectronics March 1973 2i I F'g.2a. Constant currentdrive Fig.2b.Constant currentdrive rig.2c.Actualmethodused using the high output impedance using the head inthe feedback which uses a series resistor to of a transistor collector loop provide the constant current Furthermore, even allowingforthefullpre - the record current is truly negligible, and even up emphasis required, there should be no overload, and to 18kHz the drop in current is only 3.7 per cent. the general distortion figure should be low.

CONSTANT CURRENT DRIVE RECORD AMPLIFIER CIRCUIT Because the record/replay head is an inductor its The output required from the amplifieris10.8 impedance rises with frequency. Therefore to induce volts peak -to -peak 'for full modulation of the tape. a constant magnetic flux in the tape head the head Allowing for thefullpre -emphasis to be utilised should be driven from a constant current source. and for the saturation losses in the amplifier tran- (This is the opposite of the constant voltage drive sistors, a rail voltage of at least 48 volts is required. which requires a low output impedance from the In fact 55 volts are available thus allowing for a amplifier.) small overload. A high impedance in comparison with that of the Referring to the circuit diagram (Fig.3),it will head is thus required and there are many ways of be seen that the circuit is similar in conception to achieving this in practice. that commonly employed in audio power amplifier' Use can be made of the intrinsically high collector design. impedance of atransistor,or the head may be Transistor TR1 forms a low noise input stage and included in the feedback loop of an amplifier as has a gain of 4.5 times. TR2 is the workhorse of the shown in Figs. 2a and 2b. Both thesei approaches amplifier. It has a boot -strapped collector load for give an excellent approximation to the ideal current high gain with low distortion due to the limited drive requirements. modulation index of the collector current, and forms However, both systems have the disadvantage of the driver for the output stage. bias rejection problems and the consequent need for Transistors TR3 andTR4comprise the output tuned circuits inseries with the head. As thisis stage which operates in class A, a requirement for considered to be a major drawback, the author has low distortion when a large output is required. adopted a different method of obtaining this constant The amplifier has good linearity even before feed- current. back, and this, coupled with the high gain and hence large amount of allowable feedback, serves to reduce METHOD USED distortion to a very low level. The basic recording amplifier has a very low out- The overall loop gain at d.c. is unity giving excep- put impedance- and the record signal is fed to the tional stability of the mid -rail voltage. Components head via a resistor of a value which is large in com- R5, R6, and C9 provide a.c. feedback, and the fre- parison with that of the head over the frequency quency response for the different speeds is shaped range under consideration. by LI in conjunction with C5, C6, or C7, the fre- The bias signal is now attenuated by the resistor quency of maximum treble boost being switched and the output impedance of theamplifier(see according to the speed in use, and the amount being Fig. 2c). preset by the series resistors VR1 to VR3. The penalties to be paid for this solution are: The nominal gain is approximately 70 and this firstly, the departure from accurate current drive (the gives an input sensitivity in the region of 55mV. source impedance is now no longer negligiblein C11isa phase shifting capacitor required to give comparison with the head impedance); and secondly, stability by preventing high frequency oscillation. the need for a high rail voltage if a reasonable value of series resistor is to be used. The impedance of the specified Bogen head varies METERING CIRCUIT from 170 ohms to a maximum of 10 kilohms. At Itisthe author's opinion that average reading even the highest tape speed under consideration, the meters of the volume unit (VU) variety allow short output fromthe head begins to drop atthree duration overloads to occur without any indication. kilohertz. Departure from constant current above The recording meters in this recorder are therefore this frequency can thus be compensated for in the of the peak reading kind having a fast attack, and recording pre -emphasis. a slow decay time of about 2.5 seconds. A value of 33 kilohms was chosen for the series This reduces the effect of meter movement inertia, resistor. Between 20Hz and 3kHz the variation in for the pointer generally has less far to travel to

212 PracticalElectronics March1973 COMPONENTS. . .

Resistors Inductors R1, R101 390k CI R26, R1261k52 T1 20V -0-20V +A (R.S. 20V Rectifier) R2, R102 180k0 R27 5.6k0 T2 Bias transformer(see next month for R3, R103 100k11 R28 1.2k 0 L1, L101 4mH (2 off) }details) R4, R104 6.8k0 R29, R1291M 0 R5, R105 100k 0 R30, R130 151(0 R6, R106 10k 0 R31, R131 10k0 Heads R7, R107 1500 R32, R1322.2k0 EH1 Bogen erase head type UL296 R8, R108 10k52 R33, R133560 RPH1 Bogen universal head type UK207E R9, R109 39k0 R34, R1348.2k0 R10, R1106.8k0 R35, R13510MO (These are available from Cole ElectronicsLtd., R11, R111 220 0 R36 270 0 7-15 Lansdowne Road, Croydon CR9 2HB and R12, R112 220k 52 R37, R13739k0 Brenell Engineering Co. Ltd., 231/5 Liverpool Road, R13, R1132200 R38, R13882k0 London, N.1 who also market a tape deck incorporat- R14, R11433k 0 R39, R139150k0 ing these heads). R15, R115180k 0 R40, R14010M0 R16, R116 100k R41, R141 10k0 R17, R11733k 0 R42 10k 0 Transistors R18, R11839k 0 R43, R14315k0 -1W 5% TR1, TR101 BC159 R19, R1193.3k 0 R44 100 +W 2% TR2, TR102 BC147 R20, R1203.3k 0 R45 3.31(0 TR3, TR103 BC157 R21 220 0 R46 3.3k0 TR4, TR104 BC147 R22, R122 560k 0 R47 100 fW 2% TR5, TR105 BC148 R23, R12322k 0 R48 220 5W 5% wirewound TR6, TR106 BC157 R24, R12418k0 R49 470 fW 10% TR7, TR107 BC149 R25, R1254.7k 0 TR8 BC158 All 4-W 5% carbon film histab unless otherwise TR9, TR109 2N3823 stated, 2 off of each except R21, R27, R28, R42 TR10, TR110BC159 and R44 -R49 TR11, TR12 BFY50 All 2 off except TR8 Capacitors C1, C101 560pF polystyrene Diodes C2, C102 2.2µF 25V Tantalum D1, D101 0A47 (2 off) D2 C3, C103 10µF 25V Tantalum BZY88C 27V 400mW Zener C4, C104 100µF 64V elect. D3 BZY88C 20V 400mW Zener C5, C105 0.15µF 5% polyester D4, D5 BA145 (2 off) C6, C106 0.068µF 5% -polyester D6 12V 1.5W Zener D7 -D10 C7, C107 0.027µF 5% polyester BA148 or 1 N4002 (4 off) (use 0.022µF and 0.005µF in parallel) C8, C108 50µF 25V elect. Integrated Circuit C9, C109 2.2µF 25V Tantalum ICI, IC101 SN72741P or 7410PA (2 off) C10, C11016µF 40V elect. C11, C111 47pF 10% polystyrene C12, C1120.47µF polyester Relay C13, C1130.33µF polyester RLA 12V 1850 4 changeover contacts (ITT) C14, C11410µF 10V Tantalum C15, C1155µF 10V Tantalum Meters C16, C11650µF 16V Tantalum ME1, ME101 VU meters.Sensitivity 1.228V a.c. C17, C1172.2µF 16V Tantalum for 0dB (300µA) (2 off) C18, C1180.1µF polyester C19, C1191,800pF 2% polystyrene C20, C12050p -F 25V elect. Switches C21 50µF 40V elect. S1 4 pole 3 way (R.S. miniature Maka-switch) C22, C1221µF polyester S22 pole changeover miniature slide C23, C24 2,500µF 40V elect. S36 pole 3 way (R.S. miniature Maka-switch) C25, C125330pF ceramic S4 see text C26 0.022µF 10% polyester C27 0.22µF 10% polyester C28 0.022µF 10% polyester Miscellaneous C29 640µF 25V elect. SK1 5 pin 180- DIN socket 2 off each except C21 and C26 -C29 SK2, SK3B9A valveholder (2 off) S K4 5 pin 180° DIN socket PL2, PL3 B9A plug (2 off) Potentiometers PL4 Mains plug Bulgin type P429 VR1, VR101 1 LP1 12V 0.75W lamp and holder VR2, VR102 -1000 preset (R.S. Mouldtrim) (6 off) LP2 Mains neon with integral resistor VR3, VR103 J gin x 5in Olin matrix plain Veroboard VR4, VR104 1k0 submin skeleton preset (2 off) 16 s.w.g. aluminium for chassis (see Pt. 2 for VR5, VR1054.7k0 submin skeleton preset (2 off) dimensions), T05 clip -on heatsinks(2off), VR6, VR106 1002 10k0 log ganged pot plastic cable clips (2 off), capacitor clips (2 off), VR7, VR107 50k0 50k0 lin ganged pot 21, 30 and 34 s.w.g. enamelled copper wire

PracticalElectronics March 1973 213 R21 +55V

22011. R8 10 kfl.

R9 TO LOWER CH. SK2 PIN I 3960 C TR4 RI 390k11 R1 +27V BC 147 O 6.8kfl R5

RI 100 kfl R13 2200 C9 R6

10 kfl 22)/F C121 BIAS OEM C8 0470 F R3 00kIl t 1.6.4 BC 157 TR7 50}.1 F DI BC148 Bc 149 TR1 4 m 4 C2 Ai& 0A 47 BCI59

2.2)/F VR1 VR C7 R7 R11 R12 1500 2200 220611 100R 10onj 10027

C5 VR3 R2 R4 c1 MIN 180 TR 560p F. OEM kfi 0 I5yF 100068 C11 BC157

71'2 I PS 47 pF S1 a 14 R15 C3 TR2 1-1 33k0 16okn R22 BC 147 =I C15 7F 560kfl 5,5

RECORD AMPLIFIER METER CIRCUIT

C22 53c C25 [I N PUT[ R43 VR7 SKI

0 330pF 15kIl sokri

7. 4 5C I TO SK2 PIN 9 SK3 8

6c >irE-

C122 IC125 3

50kfl S3d 0 330pE 1pF [BIAS] TO LOWER CH.

TO LOWER CH.

T22 Q10Q.Q.000, PL2 SK2 )7_,...Tlil-N5E5V

C23 -.1wim 2 } R4 3 2500yF -404- C27 220 9 ).-*'1.PCIINS13 AmINI 6 8+27V LINE I I IP 1 ..mim 7 022+F 120 6OrnA 55 2V RLA

POWER SUPPLY 155 C29 3.31,11 33kfl 640p F BIAS/ERASE BFY 50 C26 BP/ 50 OSCILLATOR R49 R44 ton R47 1011 0 0222F 00220F 470 0 V t

214 +55V O TO PIN 9 SK 2

R36

D2 27011 &Y88 928 12 kJ,. C27V 937 39k11

712 IPS 827V 93882kf1 33(4 Sib

R39153kfl 17/8 TO LONER CH. +27V LINE T c19 R30 151Ln TR 8 -kF111 TRIO BC 158

BC 159

C17 934 7

8.21,11 IC1 TR9 225E SN727 IP

R35 10MR

R32 22kfl.

R27756k11 C16 MIM C1B C20=1 = C21 NNW 015F 50yF 50).JF

VR5 R33 47k11 941 >10kf1 5611

O.V.

O TO LONER REGULATOR vat 9130 TRI10 PLAYBACK AMPLIFIER EMITTERJUNCTION TO LOWER CH. IC 101 PIN 7

SK4 EH1 53e

RLA I RL A 2 CLOSED -RECORD OPEN -PLAYBACK

RLA 3 RLA4 fik0 1 .2.2z" 0 S31 RPH 1

TO LOWER CH. TO LOWER CH.

L S3 a TO S3g SOD L. LOWER CHANNEL RELAY CONTACTS SHOWN IN PLAYBACK POSITION ( DE -ENERGISED 1 S. STEREO U. UPPER CHANNEL

SCREEN

Fig. 3.Full circuit diagram of the stereo tape link. Only the upper channel has been shown; the lower channel electronics being identical to the upper channel. Components numbers of the lower channel are upper channel numbers plus 100

215 indicate a transient, and iseasier for the eye to When considering the connection of the head to follow. the amplifieritisimportant that no appreciable Referring now to the circuit diagram, transistors direct current flows through it, as this would result TR5 and TR6 comprise a unity gain voltage follower inmagnetisation of the head, and a consequent having a very low output impedance. increase in the background hiss of the tape. Itis The metering signal is rectified by diode DI and thus inadvisable to couple the head via a capacitor stored in C15. Because of the low impedance of the as the charging current for it will pass through the voltage follower the major limitation on the charging head. time of C15 is the forward resistance of the diode which is a gold -bonded germanium type. F.E.T. INPUT STAGE The discharge time is governed by the combination of the reverse resistance of the diode, R22 and the The use of a field effect transistor as an input input impedance of TR7. device allows direct connection of the head. Because In the absence of an input signal the base of TR7 of the very high input impedance of thef.e.t.it is at 6.7 volts. Preset VR4 is set so that TR7 is just requires only a miniscule bias current (about 2nA) cutoff and hence no current flows through the which isinsufficient to affect the head. Compared meter. As the signal input increases the charge on to a bipolar transistor thef.e.t.also possesses a CI5 increases positively hence forward biasing TR7. generally lower noise and distortion level. Resistor R23 providesthemeterwithoverload The f.e.t. and TRIO comprise a complementary protection. feedback pair operating at a gain of 50 from an input signal of 2.7mV at 1kHz and at 7+ inches per second. This stage has a flat frequency response. BIAS AND ERASE OSCILLATOR The f.e.t. has a considerable spread in the gate to A very pure bias waveform is needed if the full source bias voltage for a given drain current, being dynamic range of the tape is to be realised. Also, anywhere from 0.5 to 7.5 volts.Itis not easy to due to the dependence of frequency response, out- design away thisvariation, and apresetresistor put level, distortion and modulation noise on the (VR5) has therefore been provided for setting -up. bias amplitude, the oscillator amplitude should be drift free. SUPPLY RIPPLE REDUCTION Push-pull operationisusedto minimise even harmonic distortion and the rail voltage is regulated An interesting feature of the input stage is the to ensure amplitude stability of the waveform. method of supply ripple reduction. Transistor TR8 So that adequate filtering of the oscillator har- is biased as a current source. Zener diode D2 main- monic output is assured, the tuned circuit must have tainsthebase -emitterpotentialconstantinthe a high working Q. This is achieved by the employ- presence of ripple on the 55 voltline,reducing ment of a low impedance tuned circuit wound with modulation of the collector current. thick wire on a low loss high permeability pot core. The high source impedance of the current com- The tuning capacitor should have low dielectric bined with the low slope resistance of the Zener losses as well. diode D3 attenuates the ripple to a negligible level. The transistors are protected against reverse bteak- doNn of their base emitter junctions by diodes D4 EQUALISATION and D5. Although this breakdown does not inter- The function of equalisation is left to the last stage, fere with the operation of the oscillator, it can, after thus resultingin lower noiselevels, and greater a period of time, cause reduction in the current gain accuracy of equalisation which, if carried out earlier of the transistors. could cause variations in the input impedance. Zener diode D6 regulates the voltage supplied to The general purpose operational amplifier type 741 12 volts. The bias is arranged to decay slowly by is the equaliser and output stage and is eminently discharging C29 when switching off from record. suitable for this application. Because of its high gain This is essential if magnetisation of the heads is to and low output impedance itis capable of produc- be avoided. ing very accurate equalisation. It has its own internal In practice, the oscillator works well. The output frequency compensation for stability and its output rises by 0.25dB over the first minute of operation is short circuit protected. and is thereafter stable. The waveform is good, as The d.c. source impedances of the inverting and indicated by the inaudible change in the tape noise non -inverting inputs are similar and the d.c. gain of after virgin tape has been passed by the erase head. the stage isset to unity to minimise drift of the It is important when performing this test to pull the quiescent output voltage with temperature. tape away from the record head as this will record The equalisation components R37-39 and C19 are modulation noise. Modulation noise is inherent in all biased recorders and can be reduced only by selected according to the speed in use and set to the the use of low noise tapes and careful design of CCIR standards of 70, 140 and 280 microseconds. the heads. POWER SUPPLY REPLAY AMPLIFIER The power supply is quite simple, providing two outputs of 55 volts and 27 volts. Full wave rectifica- The output of the record/replay head when play- tionandlargevaluereservoircapacitorsare ing a tape rises at the rate of 6dB per octave (i.e. it employed to produce good supply regulation and doubles for every doubling of frequency) up to the low output ripple. point at which high frequency fall -off occurs. The replay amplifier compensates for this charac- teristic, and provides a high level output signal suit- In the second part of this article, next month, con- able for feeding long screened cables. stuction of the Hi-Fi Tape Link will be described

216 PracticalElectronics March1973 ARE WE ALONE? the length of reflection paths. Itis, From time to time the question therefore, possible for a signal to ofotherlivingentities,whether go round the earthseveral times they be elementaryformsor beforeemergingataparticular whether equivalent to homo sapiens angle that could be recorded as an or better,is revived. Over the past echo. year or so the climate of accept- It would be possible to expand ability has improved in these matters on the Lunan theory, but suffice to and there are less sceptics each year. say that the answer to the appear- While all science fiction has been ance of regular patterns can only treatedas havinglicenseinthis come fromaspecificattemptto ( make apracticaltestof Lunan's direction, examination tends to show thatinourgalaxy,atleast,the work.Itisinfact an experiment chancesofbug-eyed monstersor that could be undertaken by intelligentvegetationsbeingour t amateurs and perhaps hereisan companionsislosingground.In opportunity for UFO supporters to general all the findings so far point produce some practical answers to toacycleof emergencetothe their claims. presentlevelof homo sapiens as themostlikely,thoughminor USSR RESEARCH variations could occur. As a result of finding amino acids At the present state of knowledge intheMurchisonmeteoritethe the evidence is in favour of similar Russians have beencarryingout forms of lifeto that which exists SiEWATCH furtherexperiments onmeteorites now. This being the case the field BY FRANKW. HYDE that have fallen in the past. They is narrowed quite considerably and concluded - so state academicians statisticallyitis known that there Vinogradov and Vdovykin - that is a high possibility of life existing thereis evidence for the chemical elsewhere,butthepossibilityof be the source from which a probe evolution of life. communicationpresentsamajor has been dispatched. They alsostatethatitisnot problem. The probe may be in orbit and necessaryfortheretobespecial Fromseveralsourcesrecently attemptingtomake earthbeings fortuitous circumstances for this to there have come new suggestions aware of its existence by re -transmit- come about:inshort,lifecould forcontactingotherintelligences. ting broadcasts. Itis also suggested evolve anywhere where thereisa Some are based on the concept that that the probe may have arrived dust accretioninthe galaxy. This if therearefundamental laws inthesolar system about11,000 has been deduced from an exam- governing thematter, they would years ago. inationoftheMigheimeteorite be the same forall. The use of Perhaps all the evidence has not which fellin the Ukraine in1889. mathematicalconstantsand the been released but the matter was The Murchison meteorite revealed geometric forms regarded as funda- given considerable discussionata amino acids and the Mighei mental, is a natural step. meeting of the Interplanetary meteorite shows an acid whichis Society. similar toDNAbut has a spiral ECHOES FROM SPACE? The echoes are both long-time, whichissymmetrical.From this Therehavebeentworecent thatisyears, and short -time, that factthey conclude thatitisnot suggestions, one which relates to a is3to15 seconds anditisthe of biological derivation. cyclic condition of the movements latter that Lunan has investigated. of heavenly bodies and one which It is easier to offer an alternative CRAB NEBULA AGAIN isbased on the problem of long forthissuggestionbecausethe time echoes of known broadcasts. periods are short enough to avoid The crab nebula has been much The first of these suggestions in- the complication of dissipationof in the news of late. The original volves the possibility ofnear power.Ashorttimeofthree notingofthissupanovabythe approaches to the solar system -by seconds could be a direct reflection Chinese astronomer Yang Wei-Tek stars which might have a planetary from the earth's other moon that was on July 4,1054.Little other system.Statistics show thatthere has so frequently been postulated record of this occurrence is found isaquitefrequent approachto or even from the moon itself over inliterature thoughit must have within 50 light years of the solar a long path. been an event of considerable note. system. However, for both of the extremes However, in1955 W. C. Miller A secondlineputforwardis of timing there is a simple answer discovered evidence that the North based on the phenomenonof whichinvolvesthe model of the American Indians had recorded the echoes, first noted by Stormer and ionospherethat wasconsidered event. Pictures were found showing Van der Pol in1928. While they satisfactory for a long time. This the crescent moon with the nova appeared to be curious and puzzling was alayertype modellikethe nearby. This was thought to be a at that time thisis not really the successive skins of an onion. uniquerecord and thedate was case now. The ionosphere in factis not a confirmed as July 5, 1054. However,renewedinteresthas bit like that and not only are there Recently another discovery was been aroused byD.Lunan, who now many doubts about propagation made at Fern Cave in California. has studied available data over a theories that have been held for so This cave was occupied at the time long period and has offered certain long,butthelayertheorydis- of the event in 1054 and so could suggestions as to the reason for the appeared with the advent of be depicting an event duringthe echoes. Sputnik 1.In this connection there formationofthesettlement. The One of the suggestions is that the is much evidence that indicates that timing has been checked by four echoes behave as though they were there is no homogenity about these investigators and though no abso- reflected from a point at or near the layers at all. lute claim for identification is made orbitof the moon. He has con- Moreover, thereisconsiderable it seems unlikely that it records any structed mapswhicharevery variationinthedensityofthe other event. similartothestar maps ofthe northern and southern hemispheres. The fact that the nova was more northern hemisphere andsuggests Thisvariationofdensityinthe brilliantthanVenusmusthave that the star Epsilon Bootes might layers has a considerable effect on made it an outstanding sight.

Practical Electronics March 1973 217 Using this new way to sense smell at SHOCK THE VILLAINS to adistanceought not be too Mugging, and the crop of difficult, but may be complicated by pensioner -bashing cases we have the fact that odours do not seem to be witnessed lately must be distasteful represented to us in the same way to anyone with a sense of respect for that, say, colour is;to wit, itis not their fellows.For a while now I have simplyaquestionofdiscovering considered a number of possibilities primary odours then combining them forbeatingthis,veryreal,public to produce "hues" (or phews!). menace, but it is not something to be No doubt, the limitation would be easily reckoned with. on the number of trained bacteria Anyhow,havingcontactedthe packages one could incorporate in a Chief Constable for my area and transducer,since each package would only respond to a particular smell. Assuming a compromise could be accepted at around one hundred or so packages, that is one package for each of the more common smells, then by fanning air over the device,sequentialinterrogationof the bacterias' photocells would SENSE OF SMELL classify both type and amplitude of Apropos of our discussion some odour. discovered that, "no, you were not months back, relating to "sniffing", This, though, is only part way to the permittedtouseportablehigh - itseems that someone elsehas ultimatein communication. There voltage equipment witha view to latched on to the idea of recruiting still needs to be a method for repro- shockingthe villiansintosub- bugs to serve as extensions to our ducing the "pong" from the trans- mission", theonlyeffectivealter- probosci.This time it's some form ducer output waveform. This should native seemed to be a notion based (goodness knows what)of marine be a simpler job because, following onthe word"shock".The best bacteria which come as a package - receipt of this signal, it might then be deterrent thus appeared to be one deal for detecting the smells decoded within the receiver and the that could attract a lot of attention to associated with just about anything resultantemployedtoaddress a one's predicament by others in the from bombs to pineapples. corresponding set of control valves, vicinity of the incident. These wonderfullittle"critters" so releasing the correct aromatic. As An electronic device to meet our can, Igather, be trained (presumably an alternative,heaterscould be requirements generallyneedsto in the good old Pavlovian way) to arranged to vapourise the material. havequitebulkyproportions,so glow whenever they sense or come in Whether there should be a delay probablythebest"noise -maker" contactwithamaterialofone's between different signals is a moot would be a small klaxon employing a choosing.It is then simply a matter point;naturally, it would not be the miniature electric motor, this driving of detecting a photo- best of schemes to follow one smell a coarse -pitch gear pinion bearing cell (photomultiplier?) to identify the by another when the chance existed directly against a piece of bent metal type ofsmell. Unlike previous that they might clashor produce (certainlynoisierthananyloud- attempts to make bugs useful in the some offensive "mixture". speakeroftwicethesize).The role of an olfactory sense, this way Honestly,imagine one of these metal "noise -maker" could be carved would appear to be far more flexible. things going wrong. There islittle out of the lower partof a hand- The particular application to which doubt that TV servicemen would held lamp casethe upper portion this artificial nose might show some suddenlyfindnew usesforthe being utilised for photo -flash real worth ultimately is tele-olfaction. humble pair of bull -nosed pliers! attention lamps. This kind of alternative, at least, should come within the limits of the Fig. 1 law andFig. 1 gives the general LAMP picture of how such a set-up would DRIVE function. KEEP ALIVE Two switches control the device. LAMP The "arm" switch (preferably con- 'ARM' (SPRING RELEASE) cealed) connects a supply battery SWITCH 'TRIGGER SWITCH preparatorytopossibleoperation. o o Simultaneously,photo -flash lamp drive is inhibited while a "set" pulse isfed toasix -stage ring counter 52 whose outputs all go to logical "0". Release of the spring -return "trigger" switch starts the klaxon and also causes the clock generator to run.In turn, a (deliberately over -run) "keep -alive"lamprapidlyflashes while the divider counts down the PHOTO- ONE 6 STAGE signal from the clock.Thus, every FLASH SHOT RING 13 or so seconds, the ring counter LAMP FLASH COUNTER will be advanced one step and so DRIVE LAMPS fire (one at a time) the photo -flash -01 lamps. Naturally, the device ought not to betooinelegantphysically,but -12) should be of sufficient size to prevent ATTENTION SET RING COUNTERTC7(Tf- any feeble-minded body -vandal LIGHTS shoving it in a convenient Gladstone INHIBIT DRIVE bag!

218 PracticalElectronics March 1973 introducing MAUI HITINE1135 LEL";)

an associate Company of LST ELECTRONIC COMPONENTS LTD. `Service the way it ought to be'

When it comes to retail distribution we re head NEW PRODUCT and shoulders above the rest! The unique test instrument illustrated gives an We're a new Company but our experience instertly visible display of they Logic State of and ability in electronic components goes back DU_ Integrated circuits. The idikvice automati- a long way .... cally selects its power supple rrcm the termi- Here at ArrowElectronicsfast,reliable nals eat the IC's being inspected_ Each Logic service is law! Checker is supplied complete with a set of We offer a rapid, same day turn round on cilic-cm Logic plates. For fuller details see the ailmail received up to 3 pm on any given new Arrow/ catalogue. weekday. What's more, when we promise to clear all orders on receipt. we really mean it! Our no fuss, no bother ordering system is a joy to behold. We'll give you all the forms and envelopes you could possibly need. Corn- bine them with our simple Catalogue Coding and hey presto, you can order and order, time and time again without the slightest error of mistake. You'll always be up to date with as-we're continually adding to our high quality stock range and we're always up -dating our cata- SVP(31%** logue. c)k° Get to know us and you'll soon raise your "siC-01k:a\C°4- hat to our customer discount-it's tops with a NEW PRODUC1 total order value discount of 10% on orders exceeding E4.00. Arrow are the first to offer the new double Now's your chance to getto know us wound pingcore chokes designed for RF inle,ferenze suppression in Be -Polar SCR and better.Our brand new Catalogueisnow awaiting you, hot from the presses. TR IAC circuits. The chokes are supplied as a kit including a Delta Capacitor. For details see NEW PRODUCTS the new catalog ue. Products featured in the ArrowElectronics Mail Order Catalogue inCode the following: - Extended ranges of Bridge Rectifiers, alt,cte Capacitors including Variable Capacitors. .Low cost Integrated Circuit Mounting Pins, Instrument Knobs. Light Emitting Diodes. Magneto Resistors. Optically Coupled Isolators. Extended Range of Potentiometers. Medium current and High current ReLtifiers. Temperature controlled Soldering Irons Extended Range of Thyristors. Many new types of Passive Components. Hardware and Accessories includingtools. Chassis. Aluminium Boxes. An extendedrangeofOptoElectronic Devices. A very wide range of new Semiconductors. Test Meters. and many other items of great interest to the home constructor.

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7 Coptfold Road 2, fp ' ...11 Brentwood Essex bf _ Tel: Brentwood 219435 eP

V- .1c,

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",..-,,,-,-,-,-,-,-,-,-!;;";"-vig=-,,,t- ,,,,,,,,V7.:44ZZZZZZ7.7.4ki...kAZZ44kZZZ,Z4i7. Z;ZZZZZZ4ZZZZZZZ444 ,T1TAVVNT1,,,,V7,,,,,,,,,AIIIVT1,1"1,171,1,1,,,,,,,IN ...-. t .' T.44LANVVV71,47,174,4,1,4,,,,,NTIN:1,,N. ...,.0 r4 0 z4 ff. .., ul0 646.6.6646.6.6664.oirdods88.66.6.666ipcia66a.o.i.eoe:3141t1232Sagr-32EX.4'..1SLI.1:123,0.2.133:::: .. 0 ...... 132:23="3381M223,Z34n32=43?2.133U3Vir:122231:122.1.:-..?..WM...1...ci.6.66.4666666eacideetioaogi.4.66.66awi.6,6eoe568e5666.6c58.i.otien144.:geoe.68,6666c6a vv oite.611 1' NkliiitiOniiPillinliPi""".'"" -22ao.o.io .,.-g -. 0,.,. Q. x i 4, 7718 . .k-.. ,4 < z . c!1-Il CgD024, i-:fi,,.nn,..W...f...U..r,,...:',WAgHniliarithaii-4riErithwh,..,N,-.:. --, -gEig2,,n....., g,:,72n-..-z;-'------t,TINTAN,iNN,4,111N,AVNINN,,,,,,,,,4NVV.I.VV,INVVAZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZVTIVTITITINVV,IINV.,1,1,17,1,41NNTIN:74,,,,48;...0Zg ,..g...---,...... -..tr4-...... ,0,..., 0*.tt -7, ELECTRONIC D 0 TIMEPIECE. Iv JD BINGE Wu. mos-r watches and small clocks being manufac- a main spring. They have the advantage that they tured at the present time still employ a main- do not have to be wound, but their accuracy is not spring as the source of power and a balance wheel generally so much greater than that of a conven- plus hair spring as the timing mechanism. The basic tional watch. design of such timepieces has remained essentially Second generation watchesemploy a tuning fork unaltered since Huygens developed the balance wheel mechanism operatingat about 300-500Hz asthe mechanism in the 17th Century. timing device; a transistor circuit drives the tuning fork. Such watches have an accuracy of about one RECENT PROGRESS minute per month, thisbeing considerablybetter The first battery powered wrist watch was marketed than that of an ordinary watch. Tuning fork watches in 1952, but recent developments in micro -miniature do not tick, but emit a slight hum. integrated circuits have enabled high quality elec- Third generation watchesemploy a quartz crystal tronic watches to be produced which are much more oscillator which normally operates at a frequency accurate than the more common types of watch. of between about 8kHz and 33kHz; most types Most of the quartz crystal controlled watches show have an accuracy of about one minute per year. 1 he an accuracy or about one minute per year. pulses from the quartz crystal are used to control Electronic watches do not have a spring which the speed of a motor which drives the hands of the requires winding periodically,but their miniature watch. Various techniques are employed to accom- battery must be replaced about once peryear. plish this. Smaller movements suitable for ladies' watches are Fourth generation watchesdo not employ hands to becoming available, but considerable problems arise indicate the time, but incorporate a digital display in designing watches which can be powered by minia- which shows the time in actual figures. These watches ture mercury cells which must have the minimum have no moving parts and are completely electronic. They employ a quartz crystal oscillator and have an acceptable life of one year. accuracy of about one minute per year. They are only just becoming available. TYPES Some of the main types of electronic watches can PRICES be classified in the following way. Many variations Unfortunately the price of electronic watches is of these main types are available. stillquite high. The price of many watches is in- First generation watchesemploy a conventional creased because a gold case is employed. balance wheel and hair spring as the timing mecha- In the case of stainless steel cased watches, one nism, but they are powered by a battery instead of finds tuning fork models ranging from just under

PracticalElectronics March1973 221 THE FIRST ELECTRIC WRIST WATCH NEGATIVE CONNECTING WIRE The first battery driven wrist watch was developed by the French Company LIP in collaboration with the Elgin Company of the U.S.A. This watch was introduced into the LIP range on 15th March 1952, POWER but the same type of movement isstill being pro- duced by this Company. The Hamilton Company introduced a similar type of movement very shortly after the LIP watch became available. BALANCE WHEEL Although this type of watch is electric rather than FRAME OF WATCH electronic, it will nevertheless be discussed, since it led to the development of some electronic types and POLE OF CONTACT SOLENOID A has been described as the greatest advance in watch design for some centuries. The same basic principle

CONTACT has also been used in clocks manufactured by the WIRE ELECTRO-MAGNET POLE OF Hamilton, Vedette, Bayard and Odo Companies. BALANCE I WHEEL PRINCIPLE OF OPERATION CONTACT TERMINAL DIODE The principle of operation of theLIPtype R.148 REGULATING A LEVER movement is shown in Fig. 1. The R.184 is similar, but it also indicates the date. As the balance wheel rotates in an anticlockwise Fig.1. The circuit diagram of the first electric watch direction, the jewelled cam on the balance wheel pivot pushes the contact wire onto the contact. A current then flows from the power cell through the electro-magnet and the contacts and back to the cell. £40 upwards, with the smaller ladies' watches rather The energising of the electro-magnet at the instant moreexpensive.Thequartzcrystalcontrolled the pole of the balance wheel is approaching the watchesaregenerallypriced from about £100 pole of the magnet causes the two poles to be upwards, but some of the watches providing a digital attracted together so that the balance wheel is given display are not so much more expensive than other an impulse. quartz crystal controlled watches. The balance wheel continues to rotate after the It seems fairly certain that the prices of electronic contact has been made and the wire returns to its watches will fall during the next few years. The com- normal position. When the balance wheel swings in all electronic digital watches can be mass the opposite direction, the cam merely pushes the produced and assembledbyrelativelyunskilled contact wire away from the contact and the magnet personnel. This will effect a great saving in labour is not energised. The electro-magnet passes a current costs at a time when the general trend is for labour which increases to about 1mA over a period of costs to rise rapidly and integrated circuit production 3 milliseconds and then the current falls rapidly to costs to fall-especially if large numbers are pro- zero. The current pulses occur every 0.4s. For sim- duced. Thus it seems we are experiencing a revolu- plicity a magnetic shunt employed in this type of tion in watch design. watch is not shown in Fig. 1. Although one has the annual cost of the power cellreplacement(typically£1),mostelectronic SPARK SUPPRESSION DIODE watches do not require servicing so frequently as A diode is connected in parallel with the electro- ordinary watches. The forces inthe transmission magnet. When the contacts are joined little current gearing are usually less than in conventional watches flows through this diode, since the potential across and therefore satisfactory functioning is almost in- the electro-magnet reverse biases the diode. When dependent of the increase of viscosity of the oil with the contacts break, however, the current ceases to time. In general the regular cleaning and preventative flow through the electro-magnet and a back e.m.f. is maintenancerecommendedforbalancewheel developed across the latter, owing to its inductance. watches are unnecessary with most electronic types; The diode shorts out this back e.m.f. and thus pre- one only has the watch attended to if it stops or does vents damage to the delicate contacts by sparking. not keep time with its normal accuracy. The cam illustrated in Fig. 1 consists of a jewel. The amplitude of the balance wheel oscillations can CLOCKS be controlled by adjusting the contact regulating Electronic clocks are also available with either a lever; the latter rotates the contact arm on its axis. digital display or with the analogue display provided The amplitude of the oscillations of the balance by ordinary hands. Many electronic clocks are quartz wheel remains fairly constant and this results in the crystal controlled and provide an accuracy of about watchkeeping moreaccuratetimethan many one minute per year.Both battery powered and watches which are powered by a main spring. There mains types are available. is some negative feedback, since if the amplitude Some of the main types of electronic timepieces of oscillation decreases, the contact time is increased will now be considered in reasonable detail. The and this provides more power which helps to stabilise development of electronic clocks has followed a the amplitude of oscillation. rather similar pattern to that of watches (although The mean current taken from the 1.55V cell is the problems of size are not nearly so acute) and normally 5µA, but does not exceed 7µA. A 100mA- thereforeclocks and watcheswillbediscussed hour battery therefore has a life of some 15 to 18 together months.

March 1973 222 PracticalElectronics Fig. 2 (left). A circuit which tan beusedtodrivethebalance wheel of a watch Fig. 3(right). A circuit used in some self-startingwatches and clocksfordrivingthebalance wheel

ELECTRONIC WATCHES WITH A BALANCE produced which powers the balance wheel. The pulse WHEEL duration is typically 10 milliseconds. Spurious oscilla- The main problem with the type of electric watch tions of the circuit can be suppressed by connecting just described is that the contacts must be very care- a capacitor between the base and collector of the fully designed and positioned if they are to have a transistor. The resistance of the coils may be a few reasonable life. In any case, the contact life tends hundred to a few thousand ohms. to be limited. One of thedisadvantagesof this type of circuit is The work of Marius Lovet of France has led to that the balance wheel does not commence to oscil- the development of electronic watches with balance late automatically. The watch must be rotated to wheels in which the switching is carried out by a start it. This difficulty can be avoided by connecting transistor. a resistor of about 100 to 200 kilohms in the base The balance wheel of such electronic timepieces circuit (as shown in Fig.3) so that a very small carries small permanent magnets which move near current flows in the base and collector circuit even to two coils-a feedback coil and a power coil. The when the balance wheel is stationary. currents induced in the feedback coil by the move- The current flowing through the power coil inter- ment of the balance wheel magnets drive the tran- acts with the magnets of the balance wheel and sistor into conduction so that the power coil receives causes the latter to move. The minute oscillations a pulse. The magnetic field developed by this coil are built up by transistor action until the normal acts on the magnets to give the balance wheel a amplitude of vibration is reached. driving pulse. Although a current flows throughthecircuit continuously,thiscurrentcanbe eliminatedby connecting an electrolytic capacitor inseries with CIRCUIT the feedback coil (as shown in Fig. 3). The type of circuit shown in Fig. 2 may be used Contactless circuits of this general type are widely in timepieces which employ an electronically driven employed in some of the more economical types of balance wheel. If the latter is stationary, the base electronic watch. For example, theLIPmovement and emitter are at the same potential and therefore type RE.50 (introduced in 1970) was the first elec- the collector current is extremely small. tronic watch for ladies available anywhere in the When a magnet of the balance wheel moves past world. Much of the internal volume is occupied by' the feedback coil, however, the voltage induced in the1.55V, 60mA-hourcellwhichis7.9mm in this coil causes the transistor to conduct. A current diameter. One findssimilarcircuitsinthe 9154 therefore flows in the power coil and an impulse is "Dynotron" movement produced by Ebauches S.A. The Swissonic 10 electronically driven balance wheel movement. The The Nepro Elevox watch magnets can be seen fixed to the balance wheel and the power coil whichincorporatesanelec- under the balance wheel. The firstthree lettersof the days of the tronic alarm week are shown in French

inch

mm

EBAUCHES SA

PracticalElectronics March1973 MAGNET OVER WHICH REGULATOR COIL IS PLACED

Fig. 5. ThecircuitoftheBulova214seriesof "Accutron" watches

FIXING SCREWS WL PAWL JEWEL X JEWEL

INDEX PAwL DIRECTION OF ROTATION INDEz Fig.4. The miniature tuning fork used in the Bulova WHEEL 214 series of "Accutron" models (alargegroup of Swiss watch manufacturers), in the Junghans 600.12 self starting wrist watch pro- duced in Germany, etc. Electronic clocks employing this type of movement are produced by Junghans (type ATO-MAT-WERK 726);the mean current consumption isless than 160µA at 1.4V or a total of less than 1.5A -hour per year. Similar types of clock are produced by the Jaz Company. ELECTRONIC ALARMS Thefirstwristwatches withelectronicalarm Fig.6.The pawlmechanism usedintheBulova systems were introduced by the Nepro Company of "Accutron" watches forconvertingthe tuningfork Switzerland in 1972 after five years of development vibrations into a rotary motion work.Although watches which have analarm powered by a spring are available, the stored energy is rather small and this results in the intensity of sound being low and the duration limited. In addi- in watch design. It was the first watch to employ an tion, the alarm spring must be wound each time the electronic mechanism and the first to use a timing alarm is used. mechanism not based on the balance wheel. In addi- The Nepro watches employ a1.5V battery of tion,it was the first watch to be delivered to the 40mA-hour capacityto power theirwrist watch purchaser with a written guarantee of its time keep- alarms. The current is about 8 to 12mA and the ing accuracy; this is +1 minute per month. battery has a life of about a year with normal use. The frequency of operation of the tuning fork The alarms of these watches sound for five minutes watches made by Bulova for men is 360Hz. The unless cancelled by a push button. mechanical loss of energy has been reduced to a very low level and this enables the low power con- ALARM MODELS sumption of about 8/AW to be obtained. The tuning One type of wrist watch with an alarm produced fork mechanism is relatively insensitive to shock. by Nepro is the "Memotron". A vibrating membrane The tuning fork employed in the Bulova 214 series generates the sound in the MB 500 alarm system is shown in Fig. 4. It is made of a special alloy which contained in this watch. This is the smallest elec- is little affected by changes of temperature. A strong tronic alarm in production, having a volume of only conical magnet and a magnetic cup are fitted to each 0.8 cubic centimetres. prong of the tuning fork. Watches using this type of alarm can be used to A coil is fitted over each magnet. The coils must reminda personofappointmentsthroughout be fixed in position so that they are very close to the the day and can therefore be used for many purposes vibrating magnets but never touch them. The coils for which normal alarm clocks are unsuitable. The have a total ofabout 16,000 turns, comprising about Nepro Company also produce a range of very small 200 metres of insulated copper wire of diameter alarm clocks with battery powered alarms. 0.015mm. About one quarter of the number of turns on the one coil is used for feedback purposes. TUNING FORK WATCHES The first tuning fork movement was announced CIRCUIT by the Bulova Company on 25th October 1960. This The circuit of the 214 series of Bulova watches is watch, which was the result of six years of research shown in Fig. 5.It consists of a simple transistor by Dr Hezel of Bulova, represented a real revolution oscillator with a feedback coil (or "phase sensing

224 PracticalElectronics March1973 COILS & CONICAL MAGNETS DRIVE & PHASE SENSING COIL

PILLAR PLATE DRIVE COIL

COIL ASSEMBLY TRANSISTOR

HOUR WHEEL MINUTE WHEEL

LEADS FROM COIL CAPACITOR

TUNING FORK RESISTOR

TUNING FORK FASTENING HACK SPRING

Fig. 7. The inside of a Bulova 214 series "Accutron" watch coil") and two power coils. Indeed,itisbasically pawl holds the index wheel in position during the very similar to the circuits of Figs. 2 and 3 which return stroke of the index jewel. Although the index drive balance wheel watches. wheel isonly 2.4mm in diameter and 0.04mm in The alternating voltages inducedinthe phase thickness, it has 300 teeth spaced at 0.025mm inter- sensing coil are applied (via the battery and capaci- vals. The index wheel drives a gear train which turns tor) to the base -emitter junction of the transistor. the hands of the watch. This diode junction rectifies these voltages and the The rate of rotation of the index wheel is un- capacitor is charged with such a polarity that the affected by any normal changes in the amplitude of voltage across it opposes the power cell voltage. vibration of the tuning fork. The index wheel will The resistor in parallel with the capacitor allows move one tooth per vibration of the tuning fork the charge of the latter to leak away slowly so that when the index jewel moves any distance between a small pulse of current flows each time the voltage just over one and just under three times the distance across the phase sensing coil is near to its maximum between adjacent teeth. If the index wheel moves a value and at a time when the polarity of the voltage distance just over the distance between successive induced in the power coils opposes that of the power teeth, the pawl jewel will push it back during the cell. time the index jewel returns; the net movement is If the total voltage induced in the power coils at then one tooth. the instant the transistor conducts were exactly equal continued on page 231 to the cell voltage, no current would flow through them. At the correct amplitude of vibration, the voltage induced across the power coils at a time Four small Accutron watches for ladies, using a tuning when the transistor conducts is about 10 per cent fork movement less than the cell voltage. A 10 per cent increase in the amplitude of vibration would therefore result in the current pulses to the power coils becoming zero and the amplitude would then quickly fall to its correct value. Similarly, a 10 per cent decrease in the amplitude would raise the current through the power coilstodouble its normal value and return the amplitude quickly to normal. TRANSLATING THE VIBRATIONS The vibrations of the tuning fork are converted into rotary motion by means of the rachet and pawl mechanism shown in Fig. 6. Attached to one arm of the tuning fork is a straight spring (the "index") tipped with a tiny jewel which engages ratchet teeth on an index wheel. The wheel advances one tooth for each complete vibration of the tuning fork. A

PracticalElectronics March1973 stage where costs are becoming managing director of SDS, says that appreciablylowerthan discrete he intends to break down the bar- assemblies. So confidentisNew- riers between the amateur fraternity market that they are inviting users and industrial manufacturers. ofcircuits usingdiscretecom- ponentstosenddetailstothe Newmarket design team who will NEW OUTLET FOR EVR thenevaluateitinhybrid terms ElectronicVideo Recording - free of charge and submit a quota- EVR - has been slow in market tion for supplies. developmentbutgoodbusiness Yet anotherfirmspreadingits couldresult fromitsuse atsea. wings with hybrids is Coutant Elec- Most ships now have TV for the use tronics, best known as a supplier of the crew wheninport and in of powersupplyunits.Coutant coastalwaters. In factMarconi INOUSIRY started a thick filmfacility forin- Marinehassuppliedmorethan house usemanufacturingmainly 4,000multi -standardreceiversto encapsulated voltage regulators vessels of all types. and over voltage protectionunits. Ships' crews are justlike their Now the company is offering a full shore -based counterparts and like NEBOOK design and manufacturing service tohave TV on tapallthe time. to allcomers. Hence the interestin EVR which will allow the TV to keep entertain- ing from video telecartridges when POLLUTION out of normal reception range. Marconi Marine has entered an tiyAkPl' MEASUREMENT agreement with Telmar Programme The big investment in design of Service for the supply of recorded YEAR OF THE HYBRID pollutionmeasurement equipment programmes on the EVR film cart- This couldbe the year of the by Plessey looks asifitmay be ridge system which is manufactured hybrid microcircuit. Thick film tech- starting to pay off. The company's at Basildon, Essex. The cartridges nology has made enormous strides water quality monitoring equipment eachgivetwo30 -minutemono- throughdevelopment ofspecial came through a four -month evalua- chrome programmesorone 30 - inks for printing resistive networks, tion at the Water Pollution Research minute colour programme. plenty of chip capacitors and active Laboratory, Stevenage, withflying Many thousands of recorded devices are available and potting colours and installations are now programmes are available and techniqueshave alsohadtheir operating with the Sussex, Lanca- shipswillbeabletoexchange share of improvement. The result shire and Trent River Authorities. programmesatportsthroughout is a neat module of high reliability Orders have been taken from the world. The playingunitsare which has become extremely similar authorities in Sweden, Italy manufactured by a number of com- attractivetoequipment manufac- and France, the forerunners of a panies under licence from the EVR turers. profitable export trade. partnership of ICI and CIBA- The manager of the very active Another notable order, although GEIGY. hybrid microcircuit division of valued onlyat £20,000isfor an WelwynElectric,BrianAttwood, environmental monitoring system RACAL AND THE tells me thatalthoughWelwyn at Lovisa, Finland, wherethat started research on thin films some country's first nuclear power station YOUNGER MAN seven years ago and reached a is scheduled to come into operation Chairman and managing director high degree of perfection, the less in1975. The Plesseyinstallation ofRacalElectronics,Ernest Har- expensive thick film technology has measures meteorological, hydro - rison, believes in youth. He likes to now reached the stage where it can graphic and water quality data at spot likely managers earlyinlife do all the jobs of thin film. Welwyn theoutfallofthestation'swater and then give them the opportunity are now fully concentratedinthe cooling system.Atotal of 38 to show what they can do. thick film area with a plant capacity separate parameters are auto- Some recent promotions prove capable ofhandling £1 million matically monitored and the result- the point. Keith Thrower who heads worth of circuits a year, although ingdata should prove extremely up a newly -formed Advanced he admits thatactualproduction valuable evenbeforethestation Development Team has made big has not yet reached this figure. comes into operation. progress on the engineering side. Welwyn is engaged in the high He now has a top job at the age technology end of the business with of38. DavidElsbury, 36,has as many as a couple of dozen com- PROFESSIONAL climbedthe ladderto become ponents in a single package. At any COMPONENTS FOR managing director of Racal Mobil - one time some 60 different circuits cal Ltd., one of the most profitable are going through the plant and THE AMATEUR ofallRacal companies and the some 500typesofcircuits,all SDS Components at Portsmouth one that recently bookedthe custom built by Welwyn, are in field have opened a retail shop for the largest ever contract for the com- service. home constructor at their premises pany valued at £1.8 million. Also bidding for a big share of at Gunstore Road, Hilsea Trading Two other youngsters who now the hybridmarket but in the Estate. This is not the first time a havetopjobsareGerrySmith, higher volume areais Newmarket whollyprofessionalsupplierhas heading up Racal's Singapore Transistors Ltd., a member of the turned to the amateur market for office, and Jim Diggins, who joined Pye Group. extra revenue and it will be interest- Racal at the age of 25 and is now Tworecentlyannounced pro- ing to see if the project fares better managing director of Racal Com- ducts are a low level audio ampli- than some earlier attemptselse- munications Ltd. fier, the performance of which can where which,inthe end, proved Harrison told me that in general be adjusted as required by external uneconomic. successful people need to be "well components orlinks, and aself- Many famous names are listed in seen" before they are 30 years old. contained hearingaidamplifier. theproductlistwhichcan be Very few good people,he says, The company statesthatthick obtained by sending 20p to SDS ever leave the company because filmhybrids have now reached a Components Ltd. Tim Curtis, promotion prospects are good.

226 PracticalElectronics March 1973 I.L.P. (Electronics) Ltd

THE HY41 The HY41 supersedes the popular HY40 introduced by ILP last year. This highly improved module achieves true High Fidelity with a dramatic reduction in distortion (typically 0.05% at 1 KHz into 8 ohms!) and is electronically and mechanically compatible with the HY40. With this important improvement the HY41 retains all of the quality characteristics found in the earlier version and P.C. board, Resistor, Capacitors, Hardware Mountings and comprehensive manual are included in the basic kit. No further components are required to construct a complete power amplifier of extremely high performance sufficiently versatile to provide power notmerely for Hi-Fi but also for public address systems and industry. The free manual gives a full circuit diagram of the HY41 and its various applications including a complete stereo amplifier. Like its predecessor the HY41 is based on conventional and proven circuit techniques developed over recent years.

OUTPUT POWER:British Rating 40 WATTS PEAK, 20 watts R.M.S. continuous. LOAD IMPEDANCE: 4-16 ohms. INPUT IMPEDANCE: 30K ohms at 1KHz. VOLTAGE GAIN: 30db at 1KHz TOTAL HARMONIC DISTORTION: less than 0.15% (typical 0.05%) at 1KHz. FREQUENCY RESPONSE: 5Hz-50KHz +1db. SUPPLY VOLTAGE: +22.5volts D.C. SUPPLY CURRENT: 6.8 amps maximum.

PRICE: inc. comprehensive manual, P.C. board, five extra components and P. & P.:- MONO: £4.90 STEREO: £9.80

UNIQUE HYBRID PRE -AMPLIFIER The HY5 has rapidly established a position in the WORLD as the sole hybrid pre -amplifier to contain all feedback and equalization networks within an integrated pre -amplifier circuit. Supplied with the HY5 are two stabilizing capacitors and by the addition of volume, treble and bass potentiometers itis ready for use. Internally the HY5 provides equalization for almost every conceivable input, the desired function is achieved by use of a multi -way switch or by direct interconnection, Two distinctive features of the HY5 are its inbuilt stabilization circuit, allowing it to be run off any unregulated power supply from 16-25 Volts and a balance circuit which, when linked by a balance control to a second HY5, forms a complete stereo pre -amplifier. Specifically and critically designed to meet exacting Hi-Fi standards, the HY5 combines extremely low noise with a high overload capability. When used in con- junction with the HY41 and PSU45 forms a completely intergrated system. INPUTS OUTPUTS Magnetic Pick-up (within +1db RIAA curve) Main Pre -amp output 500mV. 2mV. 47K c2 Direct tape output 120mV. Tape Replay (external components to suit head). 4mV. 471(0 ACTIVE TONE CONTROLS (Baxendall) SUPPLY CURRENT Microphone(flat)10mV. 47K Treble +12db. 6mA approx. Ceramic Pick-up(equalized and compen- Bass + -12db. OVERLOAD CAPABILITY satable) 20-2000mV. variable. INTERNAL STABILIZATION better than 26db on most sensitive input Tuner (flat) 250mV. 100K ci Enables the HY5 to share an unregulated infinite on tuner and auxl. Auxiliary 1 250mV. 47K2 supply with the Power Amplifier. OUTPUT NOISE VOLTAGE: 0.5mV. Auxiliary 2 2-20mV.100K2 SUPPLY VOLTAGE 18-25 volts PRICE: MONO: £3.60 STEREO: £7.20

POWER SUPPLY PSU45 The versatile P.S. U.45 is designed to supply your HY41's +HY5's in stereo or mono format.

Specification Input: 200-240 Volts. Output: + 22.5 Volts at 2 amps. Overall Dimensions: L. 7"; D. 3.8"; H. 3.1" PRICE: £4.50 inc. P. & P.

CROSSLAND HOUSE - NACKINGTON-CANTERBURY° KENT CANTERBURY 63218

Practical Electronics March 1973 227 mf: 0.1, 0- IS, price 4p; 022, price Sp; 0.33, price 6p; 0 47, price 7p; 0.68, price 10p;1.0, price 13p. WATFORD ELECTRONICS Mullard 280 series P.C. mountings.400V d.c. mf: 0.01, 0.015, 0.022, price 3p; 0-033, 0047. price 4p. 35 CARDIFF ROAD, WATFORD 250V d.c. mf: 0.068, 0.1, 0.15, price 4p. mf: 0.22, 0.33, price 5p. C.W.O. Please.P. & P. please add lop to order under mf: 0.47, price 7p; 0.68, price 10p;1-0, price 1 Ip. L2. CERAMIC DISC CAPACITORS Working voltage 50V d.c., Plaquette body with 25in leads. Range: 22pf-10,000pf, price 2p. RESISTORS High stability, low noise, carbon film resistors.Tubular miniature, high power resistors. POTENTIOMETERS Power Carbon track,I K -2m, log or linear, single gang, price 12p; 5K --2m, Values Price log or linear, dual gang, price 37p; 5K, 2m, log or linear, single gang Watts Tolerance Range available 1-99 100-f 5% with switch, 24p. 2.2-2.2M0 E12 Ip 0.8p Knobs for above 10p. 5% 2.2-10M12 E12 Ip 0-8p 5% 22--10M S2 E12 2p I -5p 4 10% 1- 10M SI Ell 6p - SLIDER POTENTIOMETERS Quantity prices available for any selection.Ignore fractions on total Single 10K, 25K, 50K, 100K, log or linear, 3Ip. order. Dual gang, 10K plus 10K, etc., above values log or inear, 50p. Knobs for above 10p. CAPACITORS Electrolytics, general purpose, miniature, axial lead Mullard 015, PRE-SET POTENTIOMETERS SKELETON .016, 017 series. Horizontal or vertical mountings, 0-25W, miniature, price 50. Imf 63V 6p 22mf 63V 6p I.5mf 63V Op 47mf 63V 6p VEROBOARDS 2-2mf 63V 6p 100m/ 40V 6p 0.1 0.15 0.1 0 -IS 3.3mf 63V Op 150mf 25V 6p Dimensions metrics metrics Dimensions metrics metrics 4.7mf 63V 6p 220mf 25V 1 1p 2fin 3fin 22p 16p I7in . 2fin 75p 57}p

6.13mf 63V 5in 6p 470mf 25V 13p 2fin 24p 24p 171n Sin (plain) 82p

l0mf 63V - 6p 680mf 25V 20p 3fin 3fin 34p 24p I7in 3Iin (plain) - 60p

I Smf 63V - 6p 10Ornf 25V 25p 3fin Sin 27p 27p I7in - 2fin (plain) 42p Pins insertion tool. 52p.Spot face cutter, 42p.Pkts. of 50 pins, both POLYESTER FILM CAPACITORS sizes, 20p. Mullard C296 series.400V d.c. mf: 0001, 0.0015, 0.0022, 00033. 00047,00068, 001, 0015, 0022, JACK PLUGS AND SOCKETS price 21-p. Standard screened 12p 2.5mm screened 8p mf: 0'033, 0047, 0068, 0 I, price 4p. Stereo screened 30p 3.5mm screened 10p mf: 0.15, price 6p. Standard sockets 12p 2.5mm sockets 7p mf: 0.22, price 7p. Stereo sockets 15p 3.5mm sockets 7p mf: 0-33, price 10p. 0.47, price Bp. DIN PLUGS AND SOCKETS 160V d.c. 2 pin, 3 pin, 5 pin (180' or 2401.Plugs, price 12p.Sockets, price Op.

HOME RADIO no pages 11'/" 81/4" COMPONENTS The Catalogue pictures 1,750 you MUST

?vice list have! regulaslY titillated

Details of our popular Credit Account Service and our Easy Ordering System are included in the catalogue. r

NameIADVe Only 55p. Address /'5 0, 1-01F.LACk okvE, POST AND POST THIS COUPON plus 20pPACKING with cheque or P.O.for75p. rfp-EoP-o, woicif4tisuiz-{1.4 1 I 1 HOME RADIO (Components)LTD. a Dept. PE, 234-240 London Road, Mitcham CR4 3H0 The price of 75p applies only to catalogues purchased by customers in the UK and to, BFPO addresses. ===== 228 Practical E!ectronics March 1973 5112VER JUBILEE ...THE FIRST TRANSISTOR THE TEAM THE original transistordevice A wholenewfieldof semi - was demonstrated in public for conduction technology sprang from the first time on June 30. 1948, at the exploitation of thepnjunction. Bell Telephone Laboratories' New as originally proposed by Shockley. York premises. This was the point - An amazing range of devices have contact transistor, invented by been developed through the appli- two physicists, John Bardeen and cation of thepnjunction principle. WalterBrattain,whohadbeen whereconduction is performed researching into solid state through minority as well as materials. They formed part of a majority current carriers-holes and Bell Laboratoriesteam led by electrons. William Shockley. William Shockley was also Afewmonthsfollowingthe responsible for proposing the four successful experiment that resulted layerpnpndevice,whichledto inthefirstpracticalsolidstate the silicon controlled rectifier amplifying device. Shockley set out (thyristor); and also for a different toformulateatheorytoexplain classofunipolardevices,based transistoraction. He proposed,in upon the field effect. These inven- fact, the junction transistor tions followed within a few years structure.Thistheorywaslater of the junction transistor. developed in practiceandthe Fortheiroutstandingcontribu- DR WILLIAM SHOCKLEY junction transistor became the very tionstotransistorphysics.John Dr W. Shockley was born in London of successfulsuccessortothepoint - Bardeen. Walter Brattain. and American parents on February 13, 1910. contacttransistorandthelatter William Shockley were awarded the Reared in California, he received his B.Sc. degree at the California Institute of Tech- was obsolete by about 1956. 1956 Nobel Prize in Physics. nology in 1932 and his Ph.D at the Massa- chusetts Institute of Technology in 1936. He joined Bell Telephone Laboratories in 1936. During the war he served as Director of Research for the U.S. Navy. Afterwards he returned to Bell and became director of thesolidstatephysicsresearchpro- gramme which saw the development of early junction transistors. In 1963 Dr Shockley was named the first Alexander M.PoniatoffProfessorof Engineering Science at Stamford University.He hasreceived numerous awardsforscientificachievement and public service, and serves on many top 1 level Advisory Committees in the United One of the first experimental point - An early version of a junction transistor States.Dr Shockley has contributed over contact transistors. one hundred articles to scientific journals, and more than 70 U.S. Patents have been granted for his inventions. *Dr William Shockley is to lecture at the IERE and IEE I.E.E. in London on February 14. The IERE is marking the 25th anniversary 12th -18th February 1973 oftheinventionofthetransistorby An exhibitionattheInstitutionof devoting a specially enlarged issue of its Electrical Engineers demonstrating An early production version of the Journal-The Radio and Electronic the evolution from the point -contact point -contact transistor. ii Engineer-to a unique collection of nearly transistor to complex integrated 20 papers on semiconducting subjects circuits. contributed by leading British scientists and engineers who have worked in this 13th February 197310.00 a.m. ii field during the past quarter of a century. A colloquium "The 25th anniversary of This Transistor Issue of the Radio and the Transistor" at the Royal Society. Electronic Engineer which is dated 14th February 19735.30 p.m. January -February 1973, may be obtained A lecture byDr William Shockley from the IERE Publications Sales Depart- "The invention of the transistor: an ment, 9 Bedford Square, London WC1B example ofcreative -failure method- 3RG, price L200 per copy, post free. ology" at the IEE. 15th February 197310.30 a.m. A half -day discussion meeting "What To celebratethissilverJubilee,the next in semiconductors" at the IEE. Institute of Electrical Engineers, in con- junction with the Institution of Electronic 3.00 p.m. andRadioEngineers,has arrangeda A lecture by Dr W. E. J. Farvis "The number of events which will takeplace influenceof thetransistorinour between the 12 and 16 February 1973. society and economy" at the IEE.

PracticalElectronics March 1973 229 Transistor 25Trail FROM RECTIFYING CONTACTS TO PN JUNCTIONS

STARTINGLY new and revolutionary technical POINT -CONTACT RECTIFIERS device rarely appears simply out of the blue. Point -contact rectifiers were first put to practical The invention or discovery is generally a culminant use as signal detectors in the early days of wireless, achievement by a research worker who has followed around 1904. Natural lead sulphide was commonly in the train of a number of earlier researchers and used. During the mid -1920's the crystal detector was experimenters. finally ousted from radio receivers by the thermionic Experience suggests that requisite conditions for a valve. momentousbreakthroughare(1)asufficiently advanced state of theoretical knowledge, (2) a large PLATE RECTIFIERS demand or potential need for a particular kind of Plate or "metal" rectifiers consist of thin semi- device and (3) a sufficiently sophisticated technology conducting layers with metallic electrodes on either capable of undertaking development and then quan- side. Cuprous oxide and selenium are the two most tity production of some innovation. important materials that have been widely used. Amplification of electric currents is an essential The rectification effect of contacts between metals part of electronics. The idea of a solid state ampli- and cuprous oxide was already known to Braun. fier had been a vision in the minds of many scientists The first useful device appears to have been made and experimenters for many years before the triumph by Grondahl in 1920. of 25 years ago. The cuprous oxide rectifier was used on a large As beneficiaries of the electronic wonder of the scale for power rectification and for use in measur- century, itis appropriate for us to look back and ing instruments, from the mid -1920'sto thelate try to pick out some of those stepping stones that 1930's. Then it began to be replaced by the selenium formed a path, no matter how faint and discon- rectifier which offered many advantages. tinuous, which led to the ultimate success of Messrs. The selenium photocell was widely used during the Bardeen, Bratain, and Shockley. period 1930-40. EARLY INVESTIGATIONS NEW CONCEPTS With some justification we can identify the com- Investigation into the properties of semiconducting mencement of the trail to the transistor with Michael materials appears to have received a great impetus Faraday, whoin1833recordedthenon-linear in the 1930's. One important new concept was the characteristics of certain conductors of electricity. "hole", introduced by A. H. Wilson in 1931 when He found that silver sulphide had a negative tem- formulating the transport theory of semiconductors perature coefficient. based on the band theory of solids. In 1873 Willoughby Smith discovered that light But the mechanism by which the widely used affected the resistance of crystalline selenium. metal -semiconductorrectifiers("metal"rectifiers) In 1876 Adams and Day observed non-linear con- operated was not clearly understood. One theory duction phenomena on light-sensitive selenium cells. that received general acceptance was based on the (A fascinating light beam wireless communication Schottky effect (1938), a concept similar to the ideas system was created by the American experimenter put forward to explain thermionic emission. Accord- and inventor Alexander Graham Bell (1847-1922). ing to Schottky, cold emission or field emission is Speech was transmitted some distance in space by produced by the application of a few volts across a modulating a light beam and then received upon a thin film of semiconducting material (the copper- selenium element, which produced an electrical out- oxide coating); and this is due to stable space charges put corresponding to the speech input.) in the semiconductor alone, without the presence of The earliest detailed investigation of the rectifying a chemical layer. effect of dis-similar materials in contact, was carried Also during the same period N. F. Mott offered out by the Austrian physicist Braun around 1874. a theory for swept -out metal semiconductor contacts Braun explored a variety of crystals, but mainly lead which is known as the Mott Barrier. and ferrous sulphide, and used a base electrode and In 1938 Helsch and Pohl published an account of wire as a point -contact. He observed that the resis- a solid-state amplifier.This consisted of a single tance was dependent upon the polarity of the applied crystal of potassium bromide with a single wire of voltage, as well as on the nature and condition of platinum providing control of current through the the contact surfaces. Braun likened this phenomena crystal.No practical developments resulted. to the conduction between closely spaced electrodes in a gas. WAR -TIME ADVANCES Braun also appears to have been thefirstto The invention of radar just before the second observe the rectification effect produced by selenium. World War stimulated a new interest in the solid Like many pioneers, Braun had his critics and his state rectifier as a detector of microwaves. And so discoveries did not gain immediate recognition. the silicon point -contact detector was developed.

230 Practical Electronics March 1973 ELECTRONIC TIMEPIECES During the 1940's the technique of crystal "doping" was introduced. Boron added to highly purifiedsili- continued from page 225 con was found to result in highly sensitive crystals. This arose from experiment and the theory behind this effect could not then be explained. This was a very significant period for the future of solid state.For one thing, the requirement for improved detectorsforoperationatcentimetric wavelengths ledto an intensivesearchfor new materials. The discovery of germanium was one direct result of this activity. The Omega f300 watch. A balanced tuning fork move- POINT -CONTACT TRANSISTOR ment is used Shortlyafterthewar,Bardeen,Brattain, and Shockley were involved in research on copper oxide rectifiers.Bardeen showed that a Schottky barrier layer could exist at the free surface of a semi- conductor. This layer makes the contact properties independent of thermionic work functions. Follow- ing upon this, Bardeen and Brattain initiated the series of experiments that led to the invention of the point -contact transistor. They placed two point -contacts close together on the surface of a crystal.It was found that a current flowing through one could influence the current flow- ing through the second circuit. The first practical Regulation of the watch is effected by moving solid state amplifying device had arrived. This was either of the small regulator plates which are attached December 1947. to the ends of each side of the tuning fork. This In working out the basic mechanism involved in makes an extremely minute change in the effective point -contacttransistors,Bardeen discoveredthe length of the fork. An adjustment of half a second carrier -injection phenomena. This injection of extra per day can be made. current carriers into the semiconductor in the region An interior view of the mechanism of the Bulova of contact when forward bias voltage is applied pro- 214 series watches is shown in Fig. 7. duces the "transistor" action. Later, Shockley carried out a research experiment MODELS to diagnose the surface phenomena of the original The Bulova tuning fork watches are known by the transistor.In the process, he found he had devised name "Accutron", a word derived from "accuracy" a new type of transistor. This waspatented as the and "electronics". In 1970 this Company introduced junction transistor. An account of this important thefirst Accutron watches for ladies (series 230). discovery was publishedin1949.Within a few These employ a power cell of the same size as that years the pn junction device was to provevastly used in Accutron watches for men, but the frequency superiortothepoint -contactdevice,both from of the electronically driven tuning fork is 480Hz so manufacturing and application view points. that the movement can be made far smaller. The It is of interest to note that around the mid 1930's shape and construction of the tuning fork is different Shockley had instigated some research into copper from that in the models for men, but the current oxide rectifiers in an attempt to invent a solid state consumption remains at 8-10/AA. amplifying device. The results were negative. A few other companies now offer tuning fork watches. Longines offer the Ebauches caliber 6312 DIFFERENT MECHANISMS "Mosaba" movement in their "Ultronic" watches. The rectifying properties of metal -semiconductor ( Mosaba is a word derived from "Movement sans contacts are due to a different mechanism tothat balance"). Baume and Mercier have given the name now understood to be responsiblein the case of pn "Tronosonic" to their tuning fork watches, Whilst junctions. Omega refers to such watches as "f300". Bulova also During the last decade, the metal -semiconductor produce clocks with tuning fork mechanisms. type of contact has returned to favour, albeit with new materials, and it has assumed a new prominence GRAVITATIONAL EFFECTS in special devices such as field effect or metal oxide The frequency of some typesof tuning fork semiconductortransistors(m.o.s.t.),and Schottky watches is dependent on their position owing to the barrier diodes used for microwave purposes. The pull of gravity on the prongs of the fork. When the m.o.s. technique is extensively used in integrated cir- prongs (or "tines") point downwards, the watch may cuit manufacture. run a few seconds per day faster than when the Thus itseems thecircle has been completed. prongs are horizontal. Development of the pn junction has stimulated fur- This disadvantage has been almost eliminated in the ther widespread research into solid state physics over balanced Mosaba movement designed by Ebauches these last 25 years, and a new interest has arisen in S.A. It operates at 300Hz and is marketed as the the rectifying phenomena which was the starting Swissonic 100 range by Longines in their "Ultronic". point of this "trail to the transistor". And so more The Omega "f300" range also employs a balanced devices seem likely to be developed in the future tuning fork movement. which make use of both mechanisms of current Next month the final article will look at, among transport. other things, quartz, cybernetic and digital watches. Practical Electronics March 1973 231 PE Sound Synthesiser 2 STABILISED POWER SUPPLY By G. D. SHAW

I F the modular concept outlined last month, is to self tapping screws. Repeated removal and replace- be followed in its entirety, this implies that not ment of these screws will result in wearing of the only must each circuit be entirely self contained but threads whichwill,inturn, make the assembly also that each circuit, complete with its various con- sloppy.Itis suggested therefore that assembly of trols, should be capable of operating as a separate the mainframe is only attempted when all necessary entity either within, or external to, the framework of drillings, etc. have been completed, and that, once the synthesiser as a whole. assembled,itisleftso.If the constructor wishes, These factors, coupled with the experience gained for any reason, to have the facility of stripping the inbuilding the prototype, contributed towards a assembly down repeatedly he would be well advised decisiontoredesignthe instrument intoafully to redrill the securing screw holes and tap them to modular form based on one of the many commer- take a suitably sized metallic thread insert. cially available racking systems. This month modifications to a standard racking system will be described together with constructional details of the twin stabilised power unit that will COMPONENTS supply the various synthesiser card modules. ...

CHOICE OF RACKING SYSTEM RACKING SYSTEM It was believed that, in the interests of economy, Card Frame the Card Frame System 1 by Vero offered the Kit of parts for a System 1 Card Frame with a pair greatest value. Utilisation of this particular system, of guide mouldings to suit (Part No. CFMN/1) however, means that the constructor will be obliged SK7-SK13 8pin McMurdo sockets (Part No. RS8) to manufacture his own modular inserts which may (7 off) perhaps be a deterrent to those not having the PL1-PL7 8 pin McMurdo plugs (Part No. RP8) facilities or experience to tackle sheet metal fabrica- (7 off) tion.In this case the modular racking system type 3E also by Vero has the advantage that it covers a Frame parts above available from Vero Electronics range of components which may be easily assembled Ltd., Industrial Estate, Chandler's Ford, East- into modular inserts. leigh, Hants., S05 3ZR This latter system is extremely well designed and the component parts of the assemblies are precision made, these factors, naturally enough, being reflected in the price of the 3E System which is several times greater than that of System 1. Fig. 2.1 shows a general view of the assembly of the card frame to be used as the mainframe of the MODULE FRONT PANELS synthesiser chassis. The aluminium end plates are Fig. 2.2 shows the composite front panel layout already pre -drilled to suit the standard Vero com- with dimensions.It will be seen that the panel is ponents normally used in the assembly of a System 1 divided vertically into eight separate sections. These Card Frame.It will be necessary, however, to pro- sectionsrepresent thefront panels of individual vide additional holes to allow for modifications to modular units and, with the exception of the strip the standard assembly and to provide mounting on the extreme right of the panel, can be removed facilitiesforanumber of. components.Drilling from the mainframe complete with their respective details are shown. card supports and circuitry. The right hand strip is permanently fixed to the MAINTAINING A TIGHT ASSEMBLY mainframe by two small aluminium brackets. The left-hand panelisslightly wider than the The slotted card support sections are made of remainder mainly to act as "fill-in" on the full width plastic and are secured to the end plates by means of of the front panel.

232 PracticalElectronics March 1973 SECURING BRACKET for PowerSupply Control Strip 14 SW G Alurnirim 14 (2 off)

Lower Mounting Rail shown for reference CONNECTOR MOUNTING only. Rail flange drilled 6 -BA in 3 RAILS CFMR/1(2.0 positions tee Fig2-4 and assembled to P.S.U. X holes via slotted holes in PS.U. Final adjustment of Raab) be made to, suit McMurdo sockets GUIDE MOULDING CFMW/1 8 (toff) N.B. Holes for End Plate -to -Guide Moulding fixing exist as standard drillings 40.4

150 14.5 2

SUPPORT PLATES CFSP 4U/W modified as shown and assembled into Frame at appros 1/3 spacing (2otf)

END PLATE CFEP 4U/13 (toff) Note orientation of Support Plate it,rear and front edges\ of Plate are located with r to mounting lug position. Front lugs closer to edge,Rear lugs further bock from edge

Ensure Guide Mouldings are assembled with slots Holes '8 in End Plates Securing Brackets 68A clear chamfer facing toward front Holes id in Securing Brackets 4 BA ckar of Frame All dimens.in mm.

Fig. 2.1. Perspective view of the Card Frame System 1. The end slots on the upper mounting rail require to be elongated for future adjustment of McMurdo sockets

640 606 38.5 60.6 606 60 -1- .1

METER/REVERB RAMP/GENERATORS TONE CONTROLSAMPLE/HOLD OUTPUT/DIFF SHAPER OSCILLATORS P S.U. AMPLIFIERS

177 (Check Diension)

4255 (Check Dimension) NIL Finished size dimensions are All dimensions in mm. for REFERENCE only. Final assembly of Panels into Case are to correspond to overall Check Dimensioni shown Fig. 2.2. Composite front panel. These sections represent the front panels of individual modular units as indicated 233 PracticalElectronics March 1973 Dimensions shown thus* are for reference only and are to be marked from Components Fig."2.3a. Drillingandbending Board_ detailsforcircuitboard support All dimns in mm. plateandMcMurdoplug (131 details of retaining rod

FRONT PANEL MODULE SUPPORT PLATE Circuitboards are supported on a plate to one end of which isattachedthemodulefront panel and to the other end plug which mates with a socket at the rear of the mainframe assembly. Fig.2.3a shows details of this supportplate.Care should be taken in bending this item and

thebends should be made as156 tightlyaspossible. Lackof attention to this 'point will mean that the overall depth of the plate is greater than specified with the result that the front panel: when CIRCUIT BOARD SUPPORT attached, will not be flush with MODULE LOCKING 14SWG Aluminium the card support moulding in the ROD - - main frame. 222 Modules are retainedinthe 2 Holes 6BA clear 8 6BA clear main frame by means of a Mn & c/sunk (4.5mm) rod, Fig. 2.3b, screwed Hole 'C 4 BA clear 2B.A. at one end, which passes 2 Holes TC Z BA clear (a) through the front panel and en- 16 gageswithaRosanbush,or similar, in the power supply sub - omm dia socket head frame. This' arrangementalso grub screws and Rod providesameans whereby the 4.5mm(3/46) dla recessed to suit module may be withdrawn from bright mild steel

the main frame and,forthis Threaded 2 BA

purpose, a locking collar is pro- 1 -\---- 10dia Knob parallel vided to. abut the lower lug on knurled the circuit board support plate. From Aluminium or Dural (b)

P.S.U. SUB -FRAME ASSEMBLY regulation from zero to 400mA is better than I per Fig. 2.4 shows the bending and drilling details of cent. (Totalcurrentrequirementforthebasic . the power supply sub -frame.As with the circuit synthesiser is 400mA per rail.) board support plate care should be taken that the The output voltage of the i.c. is specified as being clamping and bending is carried out as shown and plus or minus 5 per cent of its nominal rated voltage thatthe bends are made astightlyaspossible. thus the constructor may find up to 1.5 volts varia= Details have not been provided about the positioning tion across the two power supply rails.This is not of holes for Rosan bushes or components within the necessarilyadisadvantagesinceallthevoltage sub -frame. dividersinthesynthesiserwhichrequirean accurately set voltage are fitted with presets. POWER SUPPLY UNIT In a project of this kind the predictability of circuit CIRCUIT performance depends largely on the ability of the The circuit diagram of the power supply unit is power supply to maintain its voltage rails within shown in Fig. 2.5. relatively close limits. This is particularly true where Construction is perfectly straightforward (see Fig. theoscillatorsand holdcircuitsareconcerned 2.6) the only recommendation being that the leads since quite small variations in supply rail voltage from the transformer tothe bridgerectifiers be can cause significant changes in the low frequency routed to avoid passing directly over the regulators and "droop" characteristics respectively. and that they be twisted together in the interests of The power supply unit, is based on one of the hum reduction. latest regulator i.o.s to appear from Fairchild, the Wires carrying a.c. to the power supply control /LA7815. This particular device is capable of passing strip on the front panel should pass through holes up to1.5 amps without the necessity of external drilled in the rear of the sub -frame and fitted with series regulating transistors, thus it is operating well rubber grommets. Theseleadsshouldbe10in within its maximum capability.Output ripple and (254mm) in length measured from the rear face of noise is around 500 microvolts or less while load the sub -frame.

234 PracticalElectronics March 1973 e611A X 5fi long P- in 3 positions CONNECTOR MOUNTING RAIL CFMR/1 to be lightly assembled to CHASSIS prior to installation in Fig z.fra me see Fig 21

1105

tt1 Outside dimn. 10

46 15' 12 Holes 6BA clear 46 6 Holes 6BA clear& c/sunk 427 6 Holes 'C' 48A clear Outside 7 Holes 4BA clear 8 dimn. c/sunk IHolitE. din 8 fit grommet 3 Slats 'F' to 5mm dimn. 8 6BA clear

All dimn. in mm 94 Minimum bending radius throughout Outside dimn. Material: 14 S.W.G. Aluminium

Fig. 2.4.Bending and drilling details of the p.s.o. sub -frame COMPONENTS... TWIN STABILISED P.S.U. Resistors

pA71315 R1 2.7k i2 R2 -R5 2000 (2 off)

ICI R62.7ki1 +t5t 071315 All 2% + watt metal oxide 0/P SKI red C159 Gait RI Capacitors 71 2.7 LP1 kfl C1 -C23,300µF 63V 562 High ripple elect. (2 off)

R2 C3 -C4 100µF 25V elect. (2 off) 200 .11 510 Bridge Rectifiers 500mV D1 -D8 REc 41A (2 off) R3 C1 C3 200 3500pF T 100 Integrated Circuits OV 0 IC1-1C2 µA 7815 (Fairchild) blue Macro Marketing Ltd., IC2 396 Bath Rd., Slough, Bucks.

p47815 Transformer R4 T1-Main transformer, 200 0 cam primary 240V; secondary 30-0-30V at 1.5A 564 500mV

R5 Miscellaneous 200 LP2 S1-Miniature double pole, SK 5 single throw on/off 'switch

R6 LP1-LP2 miniature 28V 21111 filament lamps, C2 C4 516 FS1-500mA fuse, 100 15V pF 3300 F black SK1-SK6 1mm miniature sockets -15 V0 (6 off) 14 s.w.g. aluminium as required Fig. 2.5.Circuit diagram of twin stabilised p.s.u.

PracticalElectronics March 1973 235 C1

To P.S.U. Control Panel via grommet in rear of Cast

I. NE Spring Line and Mains Plug Input driver Transformer positions

OV -t5V +15V

To MU Control Panel and McMurdo socket SK7

Fig. 2.6.Mounting and wiring details of p.s.u. components

Smoothed d.c. supplying the indicator lamps and the assembly, the correct position of these plates is calibrating voltage points is taken from the d.c. bus - intheslot immediately totheright of the one bars coupling the McMurdo Red -Range sockets and occupied by a circuit -board support plate. thus may pass over the top of the sub -frame. Since component placement on allfront panels When the power supply unit has been wired up, offers very little clearance at the left-hand side of with the exception of the d.c. to the indicators and the panel itis necessary to cut out the front face of calibrating voltage sockets, the mainframe assembly the support plates as shown in Fig. 2.1. The 18mm may be commenced. depth of the cut-out is adequate to clear potentio- meters and sockets on all front panels except that ARRANGEMENT OF PANEL UNITS of the output amplifiers which will be fitted with Referring fora moment toFig.2.2,the con- ganged "pan -pots". structorshoulddecideatthisstagetheactual The optimum position for the support plates is arrangement or order in which he wishes the panel approximately one third of the distance in from the unitsto be placedrelativeto one another.The end plates, the exact point, of course, depending arrangement shown need not be adhered to with the upon the module arrangement chosen by the con- exception of the meter and reverberation unit and structor. the power supply control strip, which have to be sited as shown at the extreme left- and right-hand MAIN FRAME ASSEMBLY sides of the front panel respectively. Assembly of the main frame should be started by This decision is necessary at this time in order that loosely securingthe bottom slottedmoulding the support plates may be correctly placed between between the end plates.The support plates may the slotted mouldings.Viewed from the front of then be dropped into their respective slots and the upper slotted moulding placed over the lugs on the top edge of the panels and loosely secured between the end plates.Ensure that the chamfered edge of the slots in the mouldings are towards the front face of the assembly and that the vertical panels are in the same respective slot in both mouldings. This being so, the securing screws may be fully tightened and lugs on the vertical panels twisted through 45 degrees where they protrude through the upper and lower faces of the mouldings. SECURING THE P.S.U. The power supply sub -frame may now be secured to the rear of the end plates. The lower socket sup- port should be drilled to mate with the slotted holes in the power supply sub -frame (Fig. 2.4) and loosely securedinposition.Similarlythe upper socket support should be placed loosely in position.

Practical Electronics March 1973 To P.S.U. Control Panel

OV -15V

Upper Socket Support

-1901[1.

Lower Socket Support -1-15V- SV Sockets are shown in approximate positions only. Final alignment to be made From P w r Supply when Modules are in place in Frame. tag stip

Fig. 2.7.Socket arrangement and wiring on connector mounting rails

POSITIONING THE SOCKET SUPPORTS socket lugs and are parallel with the front face of the mouldings.The socket supports can now be Thefinalpositionoftheselattersupportsis secured firmly at this point and the socket placed determined by inserting an assembled circuit support in position for the first of the modules to be incor- plate, complete with plug, into the slotted mouldings porated into the assembly. until the front panel is flush with the face of the Ideally all the sockets should be placed in position mouldings. at this time; but if this is not possible the first socket A socket is now placed over the plug so that its to be positioned should be immediately adjacent to securing lugs abut the supports at the rear face and the power supply control module so that its terminals the supports adjusted so that they align with the can provide a convenient jumping off point for the leads supplying d.c. to this latter assembly. The arrangement forsupplying powertothe individual socketsisillustratedinFig.2.7, while Fig. 2.8 illustrates the arrangement for wiring up the rear ofthe power supply control strip. TESTING THE P.S.U. The power supply may be tested on completion of assembly and wiring up the main frame. The main purpose of testing is to establish whether the ripple and noise and output voltage levels of each regu- lator are within their rated specification. Load regu- lation may also be checked by coupling a 30 ohm 10 watt wirewound resistor across each power rail and observing the change in output voltage on the 154mm oscilloscope.If the offset on the scope is not suffi- Ref dime. cient to enable the trace to be observed at a sufficient Front Panel Skin holes 4 BA clear degree ofsensitivity,a highresistance voltmeter cisunk to be should be used. made to suit Brackets on End The levelof change of output voltage atthe Panel moment of connecting the resistor across the power rails is likely to be of the order of 150 millivolts or less. Note that the resistor will be dissipating about 7.5 watts and is likely to get uncomfortably hot after a few moments across the power rails.Itis best therefore to incorporate a switch in series with the

Mains resistor. Input The main frame assembly is designed to be accom- modated in a standard l9in case in the Vero range. A later article will include details of the types of cases which may be used and modifications necessary in order to fit a.c., d.c., and keyboard sockets to the rear of the case. Next month: The operation and construction of the voltage controlled oscillators and voltage inverter Fig. 2.8.Wiring details for rear of p.s.u. control strip will be given.

PracticalElectronics March 1973 237 THISprojectusesasingle,inexpensive, TTL integrated circuit, type SN7402, and a few dis- 14 13 12 11 8 crete components. Fig.1. The internal circuit 10 9 The SN7402 i.c.is a quad, two -input, positive, of the SN7402N quad two NORgate, intended for switching rather than linear input positive NOR gate 9174026 applications.However, this deviceis available for less than the price of many single transistors. SI. V ICI CC 4 5 6 7 Although when used as a gate its usefulness to r the home constructor is rather limited, with a little C2 ingenuityitcanbeadaptedtoperformother functions. 110.22uF CI C3 100 Ile-4 N 0.2218F THE SN7402 INTEGRATED CIRCUIT 6V GI R2 2101141. Internal connections to the pins of the SN7402 are /490402 917102 TuF JK1 shown in Fig. 1. kb

It is housed in a dual -in -line 14 pin package. As Injector will be seen from looking at Fig. I, each gate has two Sib Output inputs, and a single output. The output voltage of 0 the gate will be high only if all the input voltages L SIGNAL INJECTOR are low. The output potential will be low, if any of the inputs are at a high potential. Therefore, if r one of the inputs is connected to earth, the input will be controlled by the remaining input alone. R4 10) The gate may now be biased into a linear operat- C7 ing condition, by connecting this input to earth SRI through a suitable resistor. The value of this resistor 500 Must be suchthat the voltage at the outputis 60 C6 0-47uF approximately half the supply voltage. G3 C8

!Tracer C5 I 1 LS1 INJECTOR CIRCUIT 2 kfl1/4567402 The function of the gate under the conditions 2 2uF described above is that of a Class A amplifier. The JK2 input and the output are 180 degrees out of phase, and the stage thus has very similar characteristics to SIGNAL TRACER a single stage transistor amplifier. L_ _2 By capacitively coupling two gates together, with Fig.2.Circuitdiagramofthe completesignal each output connected to the input of the other gate, injector and tracer unit

238 PracticalElectronics March1973 a circuit similar to that of a free -running, or astable and the opposite will occur. The circuit will thus multivibrator, is obtained. A circuit diagram show- begin to oscillate continuously, the actual frequency ing two gates connected in this fashion is shown in of oscillation being determined by the value given the upper half of Fig. 2. to C3 and C2. The circuit operates as follows. When the supply The output is taken through the isolating capacitor, is connected, the voltages at the outputs will begin C4, to the output socket. The output wave shape to rise, and due to slight variations in component will be almost square, and harmonics of the funda- tolerances in the circuit, one will start to rise more mental frequency will thus be available up to fre- quickly than the other. quencies of many megahertz. For example, assume that the output voltage of gate 1 rises most quickly. This rise in voltage will ' be coupled by C3 to the input of gate 2.This will cause the output voltage of gate 2 to fall, this fall TRACER CIRCUIT ,involtage being coupled by C2 to the input of The signal tracer circuit consists of the remaining gate 1. twogatessuitablybiased,andcoupledbya A further rise in the voltage at gate 1 output will capacitor, C6. The circuit of the tracer is shown occur, and this regenerative process will continue in the lower half of Fig. 2. until this voltage is at its highest level, and gate 2 There is enough output available to drive a 25 ohm output is at its lowest level. impedance loudspeaker. This should preferably have Capacitor C2 will now begin to charge through a fairly high efficiency, as, the output is not very gate1, and the voltage at gate 1 input will begin large, although perfectly adequate for this function. to rise, causing the output voltage to fall.This fall Capacitor C7 is used to limit the high frequency in voltage is coupled to gate 2, causing its output response of the amplifier, whichisotherwise so voltage to swing to a slightly higher level. good, that instability arises. A regenerative action will again take place, until Resistors R4, and R5 bias the output stage, and as gate 1output is very low, and gate 2 output is very R5 is connected to the output, it also introduces a high, C3 will now begin to charge through gate 2, certainamountofnegativefeedback tothe amplifier. The input to the amplifier is taken through C5, andthepotentiometerwhichisthesensitivity COMPONENTS.. . control.

INJECTOR AND TRACER RADIO FREQUENCY DETECTOR Resistors Ifthe tracer isto be used with r.f.signals, a Rt, R2, R31.3kit(3 off) detector must be added at the input of the amplifier. R4 1k0 This could be made an integral part of the unit, but R5 4.3ka in the prototype a separater.f. probewas used. The All ±5%, PA( carbon circuit of this probe is shown in Fig. 3.

Potentiometer To metal prod or R.F input C9 Al ToTracer VR1 500kO logarithmic jack socketI 2-2ka Capacitors 1000pF+ R6 E 56 C1 100µF 6.4V elect. INPUT INPUT ear C2, C3 0.221.4F (2 off) C4 0.1µF disc ceramic Fig.3. The circuit of a simple detector which C5 2.21.4F non elect. can be built into a small metal tube to enable C6 0.47µF the tracer to be used with radio frequencies C7 0.056/AF C8 100µF 6.4V elect. Integrated Circuit COMPONENTS... IC1 SN7402N positive NOR gate Miscellaneous R.F. DETECTOR S1 Double pole single throw slider Resistors JK1, JK2 3.5mm jack sockets with break contact R6 56kf.2 R7 2.2kS2 PL1, PL2 3.5mm jack plugs ' Capacitors LS1 15 to 300, 21 to 3iin speaker C91,000pF 1.6in x 2in 0.1 in matrix Veroboard UniversalChassismembers:4in x 2inside Diode panels (2 off); 5in x 2in side panels (2 off); D1 0A91 5in x 4in plates (2 off) (Home Radio type CU51A, CU52A and CU156 respectively) 1+V batteries Miscellaneous type U7 (4 off) and battery holder Metal tube for case plus metal for prod

PracticalElectronics March1973 139 same time. The internal wiring of the i.c.is such, that the power supply must be connected to all, or none of the gates. The circuit has, therefore, to be arranged so that when the plug is inserted into the tracer input socket, the break contact of the jack disconnects one of the biasing resistors of the injector, thus disabling it. When the injector lead is plugged in, the result is the same, except that it is the tracer, output stage biasing which is removed. The unit requires 6V at about 20 to 25mA, and this is supplied by four batteries wired in series. A supply of no more than 7V may be used, or the i.c. will be destroyed. Photograph of the completed signal injector and tracer unit showing the layout of the front panel. The box is built using universal chassis members CONSTRUCTION The circuitis The casing,and metal prod for the probe will both built on a piece of 01 in matrix have to be home made. They can be constructed Veroboard, measuring 2inxI .6in.A diagram from whatever suitable materials are at hand. Pen giving the layout of this board is given in Fig. 4. cases, pen light torch cases, and 35mm film con- When completed this board is bolted to the rear tainers are popular for housing this type of probe. right-hand side of the case and must be insulated The metal prod can be a long bolt, or something from the case. This may be achieved by placing a similar. The hardware used for the prototype probe piece of expanded polystyrene between the board consists of adisused penlight torchcase, some and the case. CI is not mounted on the board, but rubber grommets, and a steel knitting needle for the is mounted on switch SI . metal prod. The output should be taken through a screened lead to a 3.5mm jack plug.The com- ponents can be mounted on a small piece of 01 in ALUMINIUM CASE matrix Veroboard. An aluminium caseis constructed using Home If the detector isto be an integral part of the Radio Universal Chassis Members, and measures unit, an extra jack socket will have to be mounted 5in x 4in x 2in. on thefrontpanel.The break contact ofthis Thefront,back,andsidepanelsarebolted should be wired in parallel with that of the other together using eight 2BA bolts, the holes for which input socket. The detector is wired between these are already drilled in the panels. two sockets. The base plate is fixed in place by four 6BA bolts. CIRCUIT ISOLATION Duetobreakthroughbetweenthetraceand injector circuits, these cannot both be run at the

2 View on taped jack socket Breakcopperstripsat9D, 10F, 10G, 101, 10J and 10K

JK1 LS1 JK2

1 2 3 5 6 7 11 12 13 1415 A o 00 o o 8 o 0 o C oo 0 0 0 D o 0 Ra 512. E oo CI F 0+0 0 G000 o H 0 0 C7 o R5 jpoo ooo06 J000 000 K o 0 0 t)0 o OR3

Direction of Batteries in i holder ex11/2V wiper LSI AA, copper strips ,-___ , JK2 ""1"-"'"

Fig.4.Layout of the components on the Vero - Component Board secured to Box board Mtn 2-65A fixings and mounted panel and interwiring details on ta thick expanded polystyrene

240 PracticalElectronics March1973 NEWS BRIEFS

Tidal Monitoring System THE TASK of monitoring tidalconditions and wave height along the coast of Spain presents enormous difficultiesusingconventionalmonitoringtechniques. ToovercomethisproblemPlesseyEnvironmental Systems have supplied pressure sensors and a digital logging system to the Spanish maritime authorities to providepreciseinformationat25oftheharbours around Spain's coastline, which is one of the longest in Europe. The pressure sensors are accurate to+0.3 per cent of full scale and this measured pressure is encoded into Two 4BA self -tapping screws are required to hold a frequency modulated analogue signal which is trans- the lid in place. The holes for these should be drilled mittedtoacentraldata collectionunitinMadrid centrally on the flanges of the side panels, using a whereitisstored on magnetic tape for subsequent No. 31 twist drill. analysis by computer. A drill of the same size may be used to drill the holes for the 6BA bolts. A No. 24 twist drillis New Radar Testing Equipment for Europe s MRCA The used to make the mounting holes in the lid. EUROPE'Snewmulti -rolecombataircraft (MRCA) speaker should be mounted on the lid at any con- usesahighlysophisticatedradarsystemand venient place. efficient testingisvital for such a system. EMI Elec- Details of the front panel can be seen in the photo- tronics'Systems& WeaponsDivisionhavejust graph. The exact size of the mounting holes will vary announced that they are supplying radar testing equip- according to the type of switch, or jack socket used, ment to assist in-flight testing. but the positioning of the holes will of course remain Unlike conventional airborne radar testing methods which limit thorough evaluation of the radar to the the same. period that the aircraft isin flight, the EMI systems The batteries are positioned to the rear, and at the will enable the radar's performance tobe examined left-hand side of the case, opposite the main com- in detail on the ground. ponent board. They should be mounted in a battery When fitted to the aircraft, the equipment will con- holder of the type specified in the components list. tinuously record the video signal from the radars onto Battery clips of the type used with PP3, or PP6 bat- magnetic video tape which can later be replayed on teries are used to make the connection to the holder. ground equipment. The new techniqueisexpected toyieldfar more information from each test than was previously pos- USING THE UNIT sible. Switch S1 is the main supply on -off switch. As described earlier,the function of inject, or UK Tops Europe in Data Transmission trace is obtained by merely inserting the appropriate THE NUMBERofterminalssendingandreceiving test lead. computer datain the Post Office's Datel services When using the injector, the first test would be to has grown by more than a quarter over the last year. Datel terminals inservice reached a new peak of the speaker of the radio, or amplifier under test. 22,214, a growth of 27 per cent. Although the UK Tests should then be made at the inputs of the earlier has only a quarter of Europe's computers, there are stages, working forwards towards the r.f. stages, or more data -transmission terminals in Britain than in the the amplifier input. rest of Europe combined. When a test is made, and no output comes from the speaker, the faulty stage has been located.It isthe stage which lies between the last, and the penultimate one to be tested.Because the output of the injector is so rich in harmonics, it may be used to test the a.f., r.f., and i.f. stages. POINTS ARISING I.C. LINEAR OHMMETER (January 1973) USING THE TRACER This article was the work ofCharles Griffiths B.Sc To use the tracer, the same procedure is used, (Eng). We apologise for the fact that an incorrect except in reverse, with the first test being made at initial was attached to our author's name. the input of the amplifier, and then working towards BIOLOGICAL AMPLIFIER (January 1973) the speaker. In Fig. 3, page 34, the value of resistorR5 should be A signal of some kind must be connected at the 56kfl.In the last paragraph under the side heading input and when this signal is not received by the Alphaphone on page 38 reference to C10 should read tracer the faulty stage has been located.It is again C11. the one that lies between where this last test, and the Fig. 5, page 39, the pin numbers 9 and 10 should be previous one were made. transposed in both the circuit diagram and case inter - When testing i.f., or r.f. stages of a receiver, the wiring.In the case interwiring pin 12 should be 11. r.f. probe must be substituted for the ordinary test These corrections bring Fig. 5 into agreement with the leads. circuit diagram Fig. 3.

PracticalElectronics March1973 241 By R.W. COLES PART 9 PROGRAMME BOARD

THE BULKof the Digi-Cal logic has now been way each location in the memory is addressed in described. Throughout the articles covering the turn starting each time at address "1" and continuing logic boards fromDISPLAYtoADDER,readers will to the final address of each R.O.M. in an incremental constantly have encountered a variety of signals . fashion. attributed to a mysteriousPROGRAMME BOARD. It is not possible to jump back or forward in the The far-reaching influences ofthis board thus sequence and random addressing of a particular having been established, the time has arrived to location is likewise impossible. delve into the method of deriving the plethora of Pausing during a sequence for an indefinite length programme output signals, a most important aspect of time is possible, as is aborting the sequence by of the calculator. clearing the address counter and stopping the clock.

DIGI-CAL PROGRAMME BASIC CIRCUIT The requirements of Digi-Cal are humble, re- The incrementalADDRESS COUNTER/ R.O.M. pro- programming ,notbeing requiredinthe normal gramme system is best understood initially by means run of things and the tasks for which a programme of a simplified circuit without any trimmings (Fig. is necessary, namely the four arithmetic functions 9.1). of addition, subtraction, multiplication and division can be carried out with only a few programme steps and without recourse to any high level language 4 STAGE COUNTER CLOCK facilities other than the press of an appropriate key. INPUT STROBE Programming theniscarried out at the basic level of logic gates and flip-flops, and the Digi-Cal philosophy is retained by making the programmes variable by wiring in diodes where required in a matrix arrangement. The separate jobs to be controlled by the pro- gramme include shifts, transfers, register and counter A B C 4-16 LINE DECODER clearing, routing and clock pulse initiation,all of ENABLE which must be carried out in a strict sequence. SN74154 0 12 3 456 78 9 10 11 12 13 14 15

PRINCIPLES OF PROGRAMME GENERATION 111110111111111111111111111M D OPERATION a The programmes for Digi-Cal are formed in a 1111111111MIONIIIIIID OPERATION b diode matrix in the form of a Read Only Memory or R.O.M. "Memory" because a number of separate 1111E111111111D OPERATION x addressable locations are provided, and "Read Only" because the instruction data in each address loca- tion is fixed at the wiring -up level and is not altered impimm OPERATION n by the operator. InthepresentsystemtheR.O.M.arrayis Fig.9.1.Principles of Read Only Memory Pro- addressed sequentially by means of a counter. In this gramme generation

242 PracticalElectronics March1973 Here, a four stage binary counter with 16 possible FULL CIRCUIT states is driven continuously by a clock pulse train. The full circuit looks very much more complicated The system states of the counter are individually at first sight but the R.O.M. arrays can be easily decoded by gates which produce an active low out- identified, and the rest of the tangle breaks up into put when inputs are in the appropriate states. sections with specific jobs. These gates are in the form of an SN74154 TTL First out of the way are IC108, 109 and 110 which M.S.I. decoder which has extra facilities to generate are simply there to divide the master (ungated)clock the complement versions of the four inputs required signal from board CB by a factor of a thousand, to by the decoder gates and a common overriding allow the programme circuits to operate at slow enable, or strobe input which can be used to inhibit speed. all outputs. Thiseasesreflectionanddecodingproblems The pin connections of the SN74154 is shown in while keeping the operation of the calculator logic Fig. 9.2.Referring again to Fig. 9.1 with Fig. 9.2 tied to a master synchronising clock signal. The only inmind,itcan beseenthat,asthecounter special thing about these dividers is the fact that the steps through the sequence, each output from the three SN7490 are connected in the ÷10 mode which decoder is enabled in turn for one clock period, thus gives a 1:1 mark space output from the final stage. establishing the programme steps. This is arranged by connecting the A stage of the The number of operations to be controlled by the programme depends on the requirements of the circuit after the B, C, D stage. machine controlled, and can be few or many as required only four being shown in the basic circuit. STOPPING AND STARTING All that remains to perform a particular operation An SN7493 (IC112)isused as the programme in a particular programme step, is to connect a diode counter, and it is made to stop or start counting by across the appropriate intersection where the step means of a gate in its clock line. Gate GI itself is line crosses the operation line. controlled by a latch flip-flop which is SET by a pulse from the EQUALS key monostable in the keyboard DIODE MATRIX logic and RESET by the programmes themselves. Setting the latchis accomplished by using the Inverters are used at the output end of the opera- clock input with a permanent "1" on the D input tion linesto act as what could be described as and clearing is achieved by using the programme "senseamplifiers"intraditional memory terms. STOP PROGRAMME operation to energise the CLEAR Another way of looking at the operation lines and input of the first flip-flop via a monostable formed inverters is as multi -input NOR gates with the number from the other flip-flop and a couple of inverters. of inputs to each gate being determined by the num- Thismethodofformingamonostablewas ber of times that an operation is used. described in the article covering the CLOCK BOARD, Note that each operation can be used any number Fig. 7.5, a monostable being necessary in this case to of times and also that any number of different opera- prevent "race" conditions removing the RESET input tions can be activated simultaneously. The basic circuit has no facilities for stopping or before the latch was properly cleared. startingthe sequence which therefore runs con- tinuously. Also only one programme is catered for PROGRAMME SELECTION and, because of the ripple -through counter circuit Three separate programmes are required in Digi- propagation delays combine to give spurious pulses Cal; three rather than four because the sequences for of a few nanoseconds width on some of the step ADDITION and SUBTRACTION are identical, the distinc- lines. tion being drawn by the fact that the ADDER BOARD All of these disadvantages have to be overcome operateseitherasa subtractororanadder in the Digi-Cal circuit, which is shown in Fig. 9.3. depending on the FUNCTION CODE which is produced directly by keyboard depressions. The ADD/SUBTRACT programme is quite simple as might be expected and requires only a few steps. Seven steps are, however, provided to allow repro- INPUTS OUTPUTS gramming if any "frills" such as round -off or true negative answer are considered possible later. The MULTIPLY and DIVIDE programmesare separate and have a possible 15 steps each, to allow 11111...110. for the increased complexity of these operations. A B C D G2 G1I51413 12 Some spare steps are also left in these operations, and can be employed as required. Theselectionoftherequired programmeis 910 1 2 3 4 5 7 8 accomplished by utilising the GI/G2 ENABLE inputs on the SN74154 decoders providing the MULTIPLY 11111-n1111-e-s-re111111111 and DIVIDE sequences, and by using the D input for alre eirm the same purpose on the SN7442 of the shorter OUTPUTS ADD/SUBTRACT sequence. Using the D input as an enable is possible with the SN7442 because if the D input is high, the output selected must be greater than seven and since only outputs one to seven are used, a high D input means Fig.9.2. The pin connections of the SN74154 all programme steps are disabled even though they four line to 16 line decoder may be addressed by the A, B and c counter outputs.

PracticalElectronics March1973 243 99351/6 IC120 15 14 13 KEY o BA CODE DEC PT SEL FUNC v 0 2 2 1/4 1C113 B 5N7442 IC114 C 12F-* D -0- INPUTS OUTPUTS R R 2021 /0 o DISP ENTRY 5Vol 3 SN7400 13 2 L1 L2 DISP ANSWER 71 G3 11 12 2I 3 4 IC118 S 5 12 1 13 TTTTC TTGND10,uF ij. i= 0.3FC0 47j1 SN7493IC112 C 98 USED)(L3,L4SN74119 NOT ----- 9 R R R S 5 R 1622.15 DISP ENTRY 4 31 6 141Au, B., A B 12 5 A 14 13 12 23122 A B 21 C 20 18 61 19 G2 231 22 21 20 18 19 // 0 L5S S L6 0S 9 IC 122 o RCL K COUNT DIR 3 32 12 SN7442 ICBCD 1 5 SN74154 IC 116 ABC 0 SN 74154 IC 17 61G2 1. IC 122 - o ADD ENABLE 1 a.- 2 9 II_Ro 3 2 4 3 4 5 6 7 1 2 3 4 4 5 6 10 11 12 13 1415 .2 3 4 5 6 7 8 910 11 12 13 14 15 14 E2 INPUT B 2 3 5 6 7 9 2 3 5 6 7 8 9 10 7 8 9 11 73 14 15 16 17 2 3 4 5 6 7 8 9 10 11 73 15 16 /7 o E2 OUTPUT '/3SN7400 IC121/2 IC113; 118 Dc SN7490 IC110 R9 6 2 ENORM REG SN7404 5 14 Ate.BY -- 3 o CARRY CLEARCLEAR Z 2 13 1 E TO Z 73 12 A9 B 89 3 e SN74041/3IC121 0 STARTCLOCK 8 C SN7490IC109 6 1 0 A TO Z SN7474IC111 11 14[ 4,6 R97 9935616IC119j 9 8. G4 1/4IC113 SN7400 CLEARo CLEAR E e L 12 9 BA IC108 Ro 32 5 4 o0 COUNTPRESETCLEAR NORM A 12 D 11 8 C ikon SN7490 B Rg 76 73 10 2 53 0 M TO A 13 CL 9935V6IC1191-/4 I 1 8 9935 V2 IC122 0 NORM PRESET M A REG SN 7404/6 IC121 10 ADD/SUB MULTIPLY DIVIDE e° 66IC120 le SN7404 IC121 SN7404 UNGATED0 NORM E REG CLOCK SN7490andFig. SN74119 and 9.3. SN7493 The are full which showncircuit has diagramin of the PROGRAMME BOARD. Power supply connections. to the SN74154 Figs. to pin 5 9.2and and GND 9.6. to GND to pin 8 All others have V1.7. to pin 14 and GND to pin 7 except the pin 10, and SN7442 which has to pin 16 and START PROGCLOCK This selection system involves ICI14, G2 and G3 COMPONENTS... and to make the principle clearer it is redrawn in an Capacitors integrated way as Fig. 9.4. Two states of the final C35, C3610µF 15V elect. (2 off) divider (ICI10), count sequence are detected by gate C37 -C400.047µF (4 off) G2 which gives a negative strobe pulse near the end of the run (see Truth Table). Diodes The strobe pulse is applied to the c input of ICI14 D104 -D142 West Hyde type "red" (or any small which is being under -used in this application as a silicon diode) (39 off) two to four line decoder with strobe input. One of the outputs zero to three is addressed by Integrated Circuits the two lineFUNCTION CODEgenerated by theKEY- C108-IC110 SN7490 (3 off) BOARDin response to the arithmetic selection made C111 SN7474 C112 SN7493 by the operator. C113 SN7400 The selected output will remain high however, 0114, IC115SN7442 (2 off) until the strobe pulse takes the c input low. The C116, IC117SN74154 (2 off) result of allthisisthat a continuous stream of C118 SN74119 strobe pulses isdelivered, via the logic described, C119, IC120DTL9935 (2 off) totheSTROBEorENABLEinput of theselected C121, IC122SN7404 (2 off) programme decoder. Gate G3 is used as a negative ENABLEthe singleADD/SUBTRACT Printed Circuit Board logic NORgate to Veroboard (8.2in x 3.4in) programme whether addition or subtraction is called. Edge Connector PROGRAMME OUTPUTS 32 way 0.1in pitch edge connector (optional) Fifteen programme operation'sare possible on this board, and although more of these would be STROBE SYSTEM useful, board space is a limiting factor for the lay- Enabling the appropriate programme decoder is out of the R.O.M. matrix. not done inad.c. manner, with a constant input Because of this limited number of available lines, throughout a particular sequence but in ana.c. some outputs do two or more jobs which seem to be manner by routing enabling or "strobe" pulses to the unconnected. For example, lineAis responsible for selected decoder which occur in the centre of each normalising the entry register, clearing the zREGIS- addressing period. TER,and clearingtheEQUALS LATCH ontheM This scheme is used to kill two birds with one COUNTER boards. stone, since by enabling decoder outputs only in the middleof each address periodthe problem of PROGRAMME OPERATION CODE spurious outputs or "glitches" is overcome. ASSIGNATIONS By the time the enable, pulse arrives the address a Normalise Entry Register counter is resting in a particular state and propaga- Clear Z Register tion delay problems are overcome. Clear M Counter Equals Latch bClear Carry Store Clear M Counter (to 000000)

c Set latch, changing clock count to DOWN and disabling A inputs to ADDER TO PROGRAMME COUNTER STOP' d Transfer the contents of the E register to GATE the Z register

FUNCTION CODE eStart Arithmetic Clock INPUTS B f Stop programme sequence

B C A g Transfer the contents of the A register to the 0000 Z register 000 h Clear the Programme Counter 0 00 i Clear E register 0 0 0 0 0 j Clear A register 00 STROBE 0 0 lilDOUTPUT kPreset NORM code from the thumbwheel into 0 the clock counter

0 I Transfer contents of M counter to A register ADD/SUB MULT DIVIDE m A register NORM in progress Fig. 9.4. Gate G2 is used to generate a strobe pulse by detecting simultaneous C and A outputs n Preset M counter to 999999 during the clock period as shown in the truth table. Thedecoder isusedtoselectthe o Clear latch array/select A register for display appropriate part of the programme according to with point position determined by thumbwheel the FUNCTION CODE inputs

PracticalElectronics March 1973 245 These operations are not related and are grouped together because they do not interfere with each %7AIAKAWAW/W4WIAV other if performed at the same time. S1A It must be remembered, however, that if a CLEAR Z Vcc signal is required by a programme, the other signals are also produced which may or may not be impor- S1B S6B tantifa "home-made" programme sequenceis R1 employed. S6A Programme outputs are arranged to be either Q1 R6 "active high" or "active low" depending on the requirements of the logic they drive, and for this Q2 Q6 reason either one or two inverters are placed at the end of the operation lines. R2 Q5 The inverters connected directly to the R.O.M. S2 lines are from the DTL family and are type 935 L3 R5 which do not have input diodes (Fig.9.5). This Q3 enables the R.O.M. diodes to be used as an integral S5 part of the circuit without reducing noise immunity. R3 Q4 LATCH ARRAY S3A R4 The latch array performs a variety of jobs which S3B S4 are relatedtothe programme, one of the most obvious of which is to stretch programme operations GND Reset over a number of steps. "Stretching" is achieved by using the programme to SET a latch in a particular step, and to RESET it in another. The latch output is then used to control a particular operation which must be continued for Fig.9.6.InternallogicoftheSN74119hex longer than one step. SET/RESET LATCH Latch L6 is used in this way to control the CLOCK COUNTER direction and ADDER ENABLE during A REGISTER NORMALISATION in the MULTIPLY sequence. Latch L5 is used to control routing logic during an CLOCK AND CLEAR E2 operation, being SET by pressing the E2 key and There are only a couple of items left on the full RESET by the CLEAR LATCH ARRAY programme opera- circuit to be mentioned, the first of these being G4 tion at the end of each sequence. which is used to NOR the CLEAR E output from the Latches L3 and L4 are not used, but are available programme and the CLEAR E input from the CE key if required, and LI and L2 operate together to con- to give a combined signal. trol the display selection. Next, the E REGISTER normalising clock output is Latch LI controls the decimal point selection (fixed taken as a tapping from the divider -chain so that or floating) and L2 controls the register selection although much faster than thefinal programme (A or E). clock, the normalising clock is slower than the arith- The i.c. used in this position is the very versatile metic clock to prevent difficulties with the long line SN74119, which like the SN74154 decoders is housed lengths used. in a 24 pin dual -in -line package. The logic of this device is simply that of six cross -coupled gate latches PROGRAMMING with a common clear line, and is shown in Fig. 9.6. The programmes used in the prototype are shown in Fig. 9.7, which presents the sequences as flow diagrams. The operations inside the shaded boxes in the MULTIPLICATION and DIVISION programmes show the conditionalbranchingoperationcarriedoutby R.O.M. DIODES Vet the CLOCK GENERATING BOARD, and are included in the flow diagram for completeness. Each of the square boxes corresponds to the pro- gramme step with which itis numbered, several OUTPUT operations being possible at each step.The spare steps do not give rise to any outputs from the board, but may be used to advantage if the basic programme is expanded or re -arranged. DTL INVERTER Re -programming does not require any particular TYPE 935 skill other than commonsense and a knowledge of the way the circuits operate. The writer has had very little time to consider just what improvements could be programmed into the calculator, but with a little ingenuity and perhaps Fig.9.5.This diagram shows how the R.O.M. modification, true negative answers (as opposed to diodes and the DTL inverters are used to form complement versions as the machine stands) should NOR gates be possible.

246 Practical Electronics March 1973 ADDITION MULTIPLICATION DIVISION SUBTRACTION

9

SPARE STOP PROG

START ARITH CLOCK (SUBS)

9

CL Z REG CL M LATCH NORM E REG CL Z REG NORM E REG CL M LATCH NORM E REG CL E REG CL Z REG 2 CL M = LATCH NORM E REG CL Z REG CL CARRY STR CL M LATCH 2 CL M CNTR 10 CL CARRY STR RESTART PROG CL M CNTR SET CLOCK CNT TO __- 2 3 DOWN. DISABLE ENTER NORM TRANSFER A INPUT TO ADDER CODE INTO ARITH A TO Z ENTER NORM CNTR CODE INTO ARITH 10 TRANSFER CNTR CL A REG E TO Z

CL A REG NORM A REG 11 SPARE START ARITH 3 CLOCK (SHIFTS) NORM A REG START ARITH CLOCK (ADD or CL CARRY STR START ARITH 12 SUB) CL M (CNTR) CLOCK (SHIFTS)

SPARE TRANSFER M CNTR CONTENTS TO A REG 12

4 SPARE SPARE CL E REG

SPARE

CL LATCH ARRAY 13 DISP A REG DISP FIXED D.P. SPARE

STOP PROG

TRANSFER 5 START ARITH 14 E TO Z CLOCK (ADDS) SPARE

CL LATCH ARRAY CL LATCH ARRAY DISP A REG DISP A REG DISP FIXED D.P. 7 DISP FIXED D.P. 6 CL CARRY STR SPARE CL M CNTR

15 CL E REG STOP PROG CNTR RESTART PROG PRESET M CNTR AR P ROG (to 999999) CNTR

Fig.9.7. This flow diagram shows the three programmes used on the PROGRAMME BOARD. The same programme is used for addition and subtraction as mentioned in the text

PracticalElectronics March 1973 247 PROGRAMME BOARD

10 20 30 40 50 50 80 0 0 000

fl IC111 IC 112 ICT13 40 1C114 1C115

3 5 7 21. 6 6 13 V.1 3 5 7X9r 05 xrxxxxxxxxxxxxxxxsxxxxxxxxxxx -a 03 10 110

*E bo IC106 p x`-v-°xxx 4,'kXxxxx'

STEP LINES

CONSTRUCTION This circuit is built on a Veroboard panel (Fig. 9.8) and carries a good deal of wiring on both sides. The R.O.M. operation lines are formed by the printed tracks on the board, but the step lines are formed from bare tinned copper wire running at right -angles to the tracks. These are spaced from the board by about lin so that diodes may be soldered -in where required. Note that the diodes are inserted with their red Diode matrix construction ends uppermost, connected to the step lines. Wiring is congested but not critical, thanks to PROGRAMME BOARD WIRING the low programme speed, and both sides of the DESTINATIONS board carry wire interconnections. as not used An edge connector of 32 or more ways is recom- ab START PROG (fr kbd) mended for use with this board, but it is not essen- ac RECALL K (fr kbd) tial; connections can be soldered directly to the ad UNGATED CLK IN (fr CB/43) printed tracks if desired.If an edge connector is ae FUNC CODE A (fr kbd) useditisnecessarytocleanthetrackends of DISP E (to disp) ag E2 (fr kbd) thoroughly with fine emery paper and then coat ah DISP E (fr kbd) them with a tarnish preventer and cleaner such as ai FUNC CODE B (fr kbd) Electrolube. aj CNT DIR'N (to CB/28) ak CLEAR E (to ED/2) TESTING al CLEAR E (fr kbd) amnot used Programme selection and step sequences can be an GND easily checked after construction by using a large ao E0 (to E2 logic) value capacitor on theCLOCK BOARDto give a very ap +5V slow programme sequence.Steps can then be fol- aq CLEAR Z REG etc (to Z2/43, kbd (NORM) and lowed with a multimeter set to a low voltage range. M1/19) Operational testing can be carried out only with ar CLEAR CARRY etc (to AD/23, M1/20, M2/20) theADD / SUBTRACT M COUNTER as DISP A (to DISP) programme until the E2 at START CLK (to CB/44) boards and logic are constructed, but when this is au not used working, little trouble should be experienced with the av DEC PT SEL'N (to kbd) other programmes. awTRANSFER E TO Z (to Z1/24) ax E REG NORM CLK (to kbd) ay ADD ENABLE (to AD/37) Not: In Fig. 6.10 (Dec. 72) Z1/22, Z1/43, Z2/22, and az NORM A REG (to CB/37) Z2/43 goto Z2/44 not CB/13. Z1/21, Z2/21 goto ba PRESET NORM CNT (to CB/27) CB/23. A1/42, A2/42 go bbTRANSFER M TO A (to CB/39) to CB/40. A1/43, A2/43 go to CB/38.InFig. 7.7 (Jan. 73) CB/40 should go to be not used A1/42, A2/42. bd PRESET M (to M1/21, M2/21) be CLEAR A REG (to A1/44, A2/44) bf TRANSFER A TO Z (to Z2/24) Next month: M Counter Boards

PracticalElectronics March 1973 Designing with Integrated circuits BY A.FOORD Simple Memory Circuits

THISmonth we will show how simple memory circuits may be constructed from gates and how the master -slave bistable is developed.In the way that a transistor bistable can be made from two IC1 a :/4SM7400m cross -coupled inverting stages, a bistable can also 0 be made from two inverting gates. This is shown in SET 1 Fig. 6.1 forNANDgates, although a similarNORcir- cuit is also possible. If the clear and set inputs are at I, and so have no effect, then for either gate a 1 at its input would produce a 0 at its output, and vice versa. Since the , output of one gate is the input of the other, the two DIC1b outputs must be in opposite states.If Q is I then CLEAR 1,4 sN7400R ?5 must be 0, and vice versa. If the clear input is 0 and the set input isI, then TRUTH TABLE Q becomes 1 and Q becomes 0.If the set input is INPUT OUTPUTS CLEAR SET 0 -CI 0 and the clear input isI then the opposite state is set up with Q equal to 1 and 75 equal to 0. o 1 0 1 If a momentary 0 input is applied to either the set 1 0 1 0 or clear input the corresponding output will become o 0 1 1 1 (last 0) 1 0 1 a I and will remain in this state until a 0 is applied to the other input. The circuit can therefore act as 1 1 (last 0) 1 0 a memory and can be used to eliminate the effects that are obtained from contact bounce on a mechani- cal switch. This could be checked as an experiment Fig. 6.1. The basic bistable circuit (Fig. 6.2). From the truth table it can be seen that, if 0 levels are applied to both inputs, then both the Q and SN7400N 1. RI outputs will be For a true bistable circuit this nn condition would be avoided. 01 GATED MEMORY When input gates are added to the basic memory in Fig. 6.1, it can be made to respond to input levels 4_ G2 only during a specific clock time interval, as shown in Fig. 6.3.While the clock input is at 0, gates 1 R2 1k0 and 2 have a 1 at their outputs and the set and clear inputs are locked out of the memory. New ov information can only reach the memory when the 0 clock input is at 1. momentary 0 on an INPUT sets corresponding OUTPUT A Iat the set input with a 0 at the clear input to 1 will give a 0 input to gate 3 and a 1 input to gate 4, Fig.6.2.The basicbistablecircuitusedto then Q will be a 1.The other possible states are eliminate the effects of switch contact bounce shown in the truth table.

PracticalElectronics March1973 249 If both set and clear inputs are at 0 when the clock goes high the inputs to the memory remain at 1 and the output does not change from its previous state.In the truth table Tn represents the time dur- ing the clock pulse while Tn +1 represents the time after the clock pulse. Similarly Q represent the state of the memory at the time of the clock pulse. (These BISTABLE CIRCUIT A circuit in which are common terms used in manufacturers' data on the output has two stable states. digital i.c.s.) NAND GATE A logic circuit where all in- When the sampling interval is over and the clock puts must have 1level signals to produce a returns to 0, further changes in set and reset can have no effect until the next clock pulse. The memory is level output. said to have "clocked", because the sampling point NOR GATE Any one input or more than can be timed to occur when the required data isat the set and clear inputs, and data outside this time one input having a 1level signal will produce will be ignored.For this circuit the set and clear a 0 level output. levels need not be pulses because input pulsing is TRUTH TABLE A chart which tabulates provided by the clock. all the combinations of possible states of the DATA LATCH inputs and outputs of a circuit. The previous circuit had three useful conditions. Qn, 0, and1.In some applications the data latch

G1 DATA 12 G3 INPUT

CLOCK OR GATE IC1 10 SNIMOON +VCC -PIN14 EARTH PIN 7 TRUTH TABLE INPUTS 7",, OUTPUT To 4,1 Fig. 6.5. The gated memory with a single data CLEAR SET input and the minimum number of gates.It can Q be realised with an SN7400N o o Qn(Q at T.)

o 1 1

1 0 0

1 1 INDETERMINATE J 0

Fig. 6.3. The gated memory with SET and CLEAR CLOCK° MASTER SLAVE inputs Ko 11.

TRUTH TABLE

INPUTS OUTPUT T , J K Q o 0 Q at T ii o 1 o

1 0 1

1 1 0 at T.

HIGH

CLOCK INPUT OUTPUT LOW 4 D Q 1 Isolate slave from master 0 0 3 Disenable inputs 2 Enter information to 1 1 4 Transfer information from master Fig.6.4. The gated memory with a single data master to slave Fig.6.6.The basic actionofa master -slave input bistable circuit

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Op Oa , (continuation of Lurke Street) DM 0.17 AFZ12 1.00 BYZIO 045OAZ211 04228170 010 Tel.: Bedford 51961 10423 0.20A8Y26 0.23 BY7.11 042OAZ222 045Z8271 0.18 1084 0.88A8Y27 0.8$ OAZ223 045Troi 0.2g BYZ12 040 I C296 POLYESTER FILM CAPACITORS 1E253 0.50Afir28 046 0AZ224 0.45 - IIYZ13 045 ZT43 0.26 400V: 0.00 1, 04015, 0-0022, 0-0033, 0-0047, 21p.0.0068, 0.01, 0-015, 0-022, 121256 0.50 A8Y.29 0.80 0AZ241 042 0.033,3p.0.047, 0068, 0.1, 4p.0.15, Hp.0.22, 7p.0-33, 101p.047, BYZ15 100 '1.1,Xxi10078 0,;1125 114645 045 ASTMS 046 12p. 1N725A .20 ABY50 0.17 BYZ113 B62 160V: 0.01, 0-015, 0-022, 0-033, 0-047, 0.068, 3p.0.1, lb.0.15,4p. 0.22, 0..4.1E914 -07 Af3Y51 040BYZ8803 3 0AZ246 0.25 ZTX3000.12 0-68, 10p. 1.0, 12p. 1144007 0.20 kflY53 41p.0.33, Hp.0.47,7p. 040 0150A2290048ZTX304B25 18118 015 ABYSS 0.20 C111 0.05 0016 030 18130 0.13 Af3Y62 046 CRI31/050.25 OC16T 048ZTX500018 MULLARD C280 METALLISED FILM CAPACITORS 250V - 18131 018 Af3Y86 0.330R81/400.4501'19 0417 ZTX503017 0.01, 0.015,0-022, 3p.0.033, 0-047, 0.068, Hp.0-I,4p.0.15, 0.22, 41p. 18202 028 413121 042 01348 2.500(20 045ZTX531045 0.33, 6p.0.47, 71p.0.68, 10p. 1-0,lip.1.5, Illp.2.2,2.1p. 20371 042A8Z23 076C810B 3.18 1)022 0.50 20381 0.25 Al1Y10 0.9$D000001 0.1600023 0.60INTEGRATED CERAMIC CAPACITORS 50V ( plaquette body) 20414 0410 AU101 140DD003 0150024 0.80 CIRCUITS E12 Series 22pF4,000pF, 11p.E6 series 0-0015-0.01, 2p.E6 series 0 015- 20417 02200107 0-10 DD006 0-18 0.37 710o 0-20 /3.047, 21p. , 2E404 0.20 BC108 0.10 0000007 0400025 400.1 020 214697 0.15110109 010 DDOOS 0.380026 4106.0.25 Mr 30698 0.40BC113 0.831 00.28 HIGH VOLTAGE CAPACITORS 1000V d.c. (300V a.c.) 016 GD3 0.601 7403 00:2200 moo 2N706 qii. 040 BC115 B20 GD4 0450029 040 0.00 I,0-0022, 0.0033,0.0047, 7p.0.0068, 0-01g 0.022, 10p.0-047,0.1, 12p. 7404 020 0.22,20p.0-47,22p. 204706A 0.12BC116 0.25005 0480030 0407405 020 221708 0.1$ BC1164 B800D8 0.25 0035 040 ' 7400 0.30 2E709 43BC118 B 25 '' POLYSTYRENE CAPACITORS 125V, 26.% 0.60 7407 0.30 2041091 0.88 BC121 B20 CIET102 0.800C36 B20 Valuesin p8: 5, 10,15,22, 33, 47, 56, 68, 100, 150, 220, 330, 470, 560, 680, 820, 2E1131 0011 045 7.7.101 0851 00122 0.20GET103 0.22 0.45 1000,36p. 2041132 0416 BC125 048GET1131.0 20 0042 040 I 74111 0.20 2E1302 0411 I 0C120 0.86 GET114 .0.1.6E 0C43 040 .7411 B23 j SOLID TANTALUM RESIN DIPPED BEAD CAPACITORS 2/41303 0.18 110140 0.55 OET115B450044 017 - ., 1.0/35,2-2/35, 4-7/35, 10/6-3, 10/16,10/25, 2211304 0.22 110147 015OET116 0.42, µF/ V: 0-1/35, 000.22/35, 0.47/35, B50 OCA4M 0.17 '4i- 0.30 22/16, 47/6-3, 1/3, 1So. 2N1305 0.22 110148 0.18 GET1200.26 i 0042 0120:18 0.30 2211306 0.25 110149 B150ET8720.300015M F' 'L 7417 030 2E1307 0.25 110157 0150ET8750230016 027 74.,0 MULLARD 015/016/017 ELECTROLYTICS (Replace C426/C437) 2/41308 B25 110158 0.12GET880B37 020 µNV: 1/63, 1-5/63, 2.2/63, 3.3/63, 4-7/63, 6-8/63, 10/25, 10/63, 15/10, 15/63, 0057 0.o, 0-48 2E2147 0.75 110160 04 3 GET881 B250058 0605 22/25, 22/63, 33/16, 33/40, 47/10, 68/16, 100/4, 100/10, 100/25,I 50/16, 220/16, - 0.48 2212148 0.60 00169 0180ET8820.25 0059 065 7493 5p.47/63,470/6.3, 5p. 68/63,330/16,9p.100/63,150/63.680/16, 2212160 0.50 7425 0.48 1000/16,15p.330/63, 680/40,1000/25. 030 1101131 0450ET885 0066 1509/6.3,Ilp.220/63, 470/40, 2N$218 0.20 GEX44 0.030.25 0070 012142' 042 1500/16, 2200/10, 3300/6-3, 18p. 2042219 0.20 1101132 046GEX45/1 0.100071 012l4''8 0.50 2N2369A 0.16130Y33 045 GEX9410.15 0072 0,20 /4.1.0, 020 RESISTORS 3/42444 1493CY34 0.80 033M 026p073 0.30 135 042 Type Tolerance Range Values Price each 2142613 048BCY38 0.40OJ4M 0480074 030 . 070 ISKRA I/2W 4R7 -2M2 E24 Ip 2/42646 *045 2OCY39 1.000.15M 04 0075 0125 0.65 ISKRA I/2W 10795 3M3 -10M I26 Ip 2142904 040BCY40 0400,1714 B870076 (ha i MULLARD I/3W 10Z2, 1R -3R9 Ell 1 2272904A 045IICY42 023 11011103 B500077 00.-4208 7440 gge MULLARD I/5W 5% 4R7 -I M E24 Ipp 2142906411111040 BCY70 0.15 118100A 0.200078 0,20 1441 METALFILM I W 5° 27R -IM E12 lip 2N2907 043BCY214800. MAT1000240079 0.22 075 WIREWOUND 2-5W 10 A R22 -R33.R47 612 9p 2142924 040BCZIO 045MAT101 0410 0081 0.20 0450 0.20 WIREWOUND 24W 3% 1R -270R 612 7p 3/42925 045BCZI1 060 MAT1200.2500811) 0.20 7451 0.20 PRESETS 100R, 250R, 500R and Decades to 5M, 0.1W, 5p.0-25W,6p. __....2029260001000121 045MAT121 B30 0081111 0.20 7453 0-20 ""'"2N8(124 040BD123 0.80MJEPO0.67 0081D51 018/41 0.20 Post and packing lop on orders under [1: at cost. 2273055 0.76BD124 0.75 MJE2955 14700811 0.40 "b 0-20 FULL CATALOGUE ON REQUEST. 2273702 0.10BDYII 1.82YMJE30550.87 0082 0.25 74-''470 0-30 2E3705 0.10BF1I5 so,(1.2MNKT1280.3500820 0.20 - 0 30 2043706 043BF117 040NKT1290410 0083 0.25 i 0-40 2043707 012BF187 045 NKT2110460084 0-25 I 0.40 2043709 040BF173 045NKT218 0240C114 0.38 0.55 2213710 040BF181 0.85 NKT214 01500122 0.60 0.45 2E3711 11.10 BF184 040 NKT216 001230.65 no 0.80 BATTERY OR MAINS 2E3819400.$5BF185 040NKT217 B3500139 0.25 1 087 2046027 ONBF194 0.17 NKT2181.13 00140 0.35 7483 1410 2215088 043BF195 045NKT2100.38 100141 0.60 7404 040 WORLDMASTER 28301 040BF196 015NKT2220.201 00169 0-20 7481 0.461 28304 0.76BF197 0.16NKT2240.2200170 0.25 7490 046 A COMPLETE VHF RADIO 28501 047 BI2861 040NKT251 02400171 0.30 7491AN 1.00 28709 042 11E898 0.28NKT271 02600200 0.40 7402 046 A.A129 040BFX12 010NKT2720. 5 00201 0.70 7493 0'76 COMMUNICATIONS RECEIVER AA212 040 13EX13 0.215 NKT2730. 00202 0.80 7494 010 AAZ13 0411 BFX29 045 NKT2740. 00203 0.40 7495 080 FORGET ABOUT 1.0107 047BFX30 045 NKT2750. 00204 0.40 7496 140 EVERYTHING ELSE A0126 040 113FX35 048NKT277 04000205 0-75 7497 646 YOU'VE SEEN, THIS AC127o 046BFX63 0.50 NKT278 02600206 0.90 74100 240 IS IT! -the most amazing AC128 A.620 BFX84 0.25 NKT3010.40 00207 0.90 74107 040 portable VHF Radio and communications A0187 025 BFX85 040NKT304 07500460 0.20 74110 040 A0188 0.25 DFX86 045NKT403 07300470 0.80 74111 146 receiver we've yet offered. BRAND NEW ACY17 040 BFX87 0.25 NKT404 054OCP71 0.97 74118 1.00 -manufactured and guaranteed by one of the ACY1$ 0.25 BFX88 020NKT678 040 4°. 0 60 74119 140 most reputable companies in advanced radio ACY11110.25BETIO 1.00 NKT713 026ORM 0.40 74121 0-80 and electronic communications equipment. ACY20 0.20 BEY11 1.25 NKT7730.23ORP61 0.4274122 143 You won't match this for valye and ACY21 020 BFY17 0.46NKT7770.88819T 0-80 74123 2.70 ACY22 010 BYF18 0.23078B 04881.040 0.2574141 1. variety of performance anywhere -we ACY27 046 BFY19 045 OAS 0408FT308 0.38 74145 140 sell similar sets at three times this ACY28 0.17. BFY24 0.46 101.6 0128T722 0.38 74150 345 price! AND YOU RISK NOTH- ACY39 040BFY44 14001.47 0.109T7231 0.881 74151 140 ING because you can return within ACY40 046 BEY50 0420A70 0.108X68 0-20 74134 2410 10 daysifnot 100% satisfied. We ACY41 043BEY514.4.2001.71 0.10 , 81631 0.30 74153 146 can't list everything that this remarkable ACY44 045 !1321252 B22 0.473 0 8X635 0.40 I10 74136 146 AD140 0401321153 0.17 01.74 01081640 0.50 74157 1.80 receiver picks up. BUT we can say that AD149 040 ' BEY64 0.420...79 0108X641 0.55 74170 4.10 the 8 wavebands cover just about AD161 .". 047 .650A81 048B 64 0.60 74174 240 everything that's broadcast -by any- AD162 0$58127BEY7 27 0 01.85 0.128X644 0.75 74175 1.33 one -from anywhere in the world.You name it -it gets it!Exciting AF106 040 138X60 0. 0A86 01 8X645 07574176 1410 specialised transmissions as well as BBC, Local Radio, Luxembourg, AF114 045B8X76 0.160A90 V15/30P0.5074190 146 AF115 045B8Y26 0.18 01.91 '4.40 030/2010 0.75 74191 14111 Continental and Pop Stations. PLUS broadcasts from all AF116 046B8Y97 0.170A95 0071'60/201 040 7419.2 ZOO of the world on the earth shrinking SHORT WAVEBANDS. AF117 046B8Y51 0400A200 0.07 V60/201P 074 74193 ZOO Attractively finishedinleatherette and stainless steel to enhance any AF118 048B8Y95A 0420A202 040X.41014)0.10174194 2.60 AF1I9 04000Y95 04201.210 lounge or study.USE ANYWHERE -costs virtually nothing to run 045XA102 0-18 74195 1415 using standard batteries or plugs into mains.Tone, volume and tuning AF124 045BT102/500R 01.211 030X AI51 01574196 1.30 AF126 040 0.75OAZ200 045XA152 01574197 1.60 controls enables adjustment to individual listening perfection.2 aerials. AF126 047BTY42 0420AZ201 040 74198 440 advanced keyboard type push button waveband selector. Dial light AF127 047IITY79/1000 OAZ202 0.42 X A161 0-25 XA162 045 440 (essential for use in darkness).Special world-wide dial and world map AF139 040 0.75OAZ203 0.42 74009 Personal hi-fi AF178 0.65 1ST Y79/40OR OAZ204 040XB101 048 computes time in any country of the world. earphone for private listening.14 transistors, 9 diodes. I thermistor. AF179 066 14601.2205042XB102 040-_lowr i. profile AFIBO 045BY100 041OAZ206 042 FREQUENCIES: Long:ISO-350kcis; Medium:565-1605kcis; 3 XB103 04514 pin OIL AFI81 042BY126 0.160AZ90" 0.47 XB113 012 SHORT BANDS: I.6-4.5Mcis; 4-12Mcis; I2-24Mc/s; 3 VHF BANDS: AF186 0.40BY127 0.17 OAZ208 0.32 88-108Mcis; I08-135Mcis; 13S-174Mcis. C27.50 + SOp P.& P. or [MO dep. AFY19 1.13BY182 085OAZ209 042XB121 045 iDi pica DIL0.111 ZR24 SOp P. & P. and 6 months at te (631.50). AFZI1 060BY213 025OAZ210 042 043 I 047 Send Sp stamp for Comprehensive Brochure of Unusual Frequency Radios. Open daily to callers :Mon. -Fri. 9 a.m.-5 p.m. SCIENTIFIC & TECHNICAL Valves, Tubes and Transistors Closed Sat. I p.m. -3 p.m. TOWERFIELD TRADING ESTATE,SOUTHEND, ESSEXWeil Orders) Personal Shoppers: 507-511LONDON ROAD. WESTCLIFF. ESSEX. Terms C.W.O. only I Tel. 01-677 2424-7

252 PracticalElectronics March 1973 isusedforstoringtheoutputinformationin counters or computers until the readout has been achieved.This enables countingto recommence while the readout from a previous phase is still tak- BOAT SHOW '73 ing place. If only the two middle entries in the truth table THE Yachtsman's winter break, this year in the set- are required (as is usual) then a single data input can tingI of a sunny Spanish harbour, the annual Inter- be used while the complement is obtained from an national Boat Show provides us with a shop window of inverter, Fig. 6.4. The input data is up -dated during marine electronics for small craft. the clock pulse and retained when the clock goes low. As in previous years there has been a steady develop- ment of the electronic gadgetry available, this year has seen the introduction of the l.e.d. (light emitting diode) to boat electronics, a new type of knotmeter and some MINIMISED DATA LATCH advancement in the receiver, transmitter field. The circuit in Fig. 6.4 required five gates to realise One firm whose name must be to the forefront when it because the D was obtained by the direct inver- we consider this year's innovations is EMI; in fact one sion of D. However, D can be obtained from the could call it their year of innovation, with no less than output of gate1, because D is only needed at the four completely new instruments available. The most input to gate 2 when the clock is high; therefore, gate interesting new product is a magnetic log. 1 will provide the required information. The new log operates by the transducer generating an a.c. magnetic field in the water surrounding it. As the The minimised circuit shown in Fig. 6.5 may be boat moves through the water a small e.m.f., dependent realised as an experiment using a single SN7400N. on the boat speed, is produced and sensed by the trans- Data D will be entered into the memory while the ducer head. This induced signal, fed back through the clock is high and retained when the clock is low. system,isamplified to givea display of speed and distance. Housed in the normal EMI Electra range case the biggest advantage of this instrument is that there are LOGIC GATE BISTABLES no moving partsbelow the water and virtually no In the previous circuits the inputs are coupled to projection (only 3mm) below the hull surface. is The other innovations from EMI are an automatic the bistable circuit all the time the clock pulse directionfinder,anf.m.radio telephone, and a gas high, so that these circuits can only bemade to detector and alarm. The direction finder is a three band toggle (divide by two) if the inputs are a.c. coupled. receiver covering the range 175kHz to 3,000kHz. To use However, it is essential in logic circuits to overcome it,itis tuned to the required radio beacon and auto- this problem without giving up the advantagesof matically gives an immediate and ccfntinuous bearing of d.c. coupling, so circuits were developedwhich pre- the transmitter. The unit has its own internal supply or vent the output transitions fromaltering the input can be powered from a 12V or 24V ship's supply. edge The Electra Gas Alarm uses a solid state imported information which was present when the leading detection unit and provides both visual and audible of the clock occurred. form alarms of dangerous concentrations of gases. These circuits are usually designed in the Itisinteresting to note that the Electrascan MKII of two gated memories, one holds the output state radar has been ordered by the RNLI for use in lifeboats. and one holds the input information read in at the Whilst on the subject of radar both Decca and Electronic beginning of the clock pulse. Since this information LaboratorieshaveintroducedMKIIradars and the islater transferred to the output memory,such a Decca Super 101 MKII is now sold with a magnifier circuit is called a "master -slave" bistable. that increases picture size to 9 inches. Several different versions are available butthey all have the master -slave action shown inFig. 6.6. TECHNICAL INNOVATION Here the operation shown is the J -K functionwhere As far as real technical innovation goes, thisis the information is transferred from master to slave on first time that we have found a l.e.d. used in a depth truth sounder. Produced by Marine Electronics and available the falling edge of the clock pulse. From the for about £39, the sounder works on the same principle table it can be seen that thisJ -Kmaster -slave bistable as a neon type and probably has a similar accuracy. will divide by two ifJand K are taken toI. and Instead of providing a point of light at the depth an input applied to the clock. reading, the l.e.d. is turned on when the pulse is trans- mitted and off when the pulse is received, thus providing an arc of light showing the depth. CONCLUSION Brookes and Gatehouse-manufacturers of perhaps We have shown how the simple memory circuit the most reliable and widely used instruments for the racing yachtsmen-have, we feel, done 1)14e sensible thing develops into the master -slave bistable, with its many in offering most of their instruments for use on ship's advantages. supply. At last no more fiddling with batteriesina heavy seaway. Part 7 will describe counters and displays Baron Instruments, another contender for the "crack" racers' instrument panel, have redesigned their meter faces and introduced a new range-the Baron Sailboat Console-the meters are lit by 1.e.d.'s and are 41- inches in diameter. Provided the instruments can prove. them- selves at sea, with the new meters (which were in fact suggested by us last year) we feel that this range is the most likley to rival B. and G. this year. Finally we think it is a pity to see Smiths Industries cashing in on the boat market with standard Radio - mobile car radios and tape units. Without the necessary The International & Allied Equipment marinisation we feel that these units will not stand up Exhibition, Bloomsbury Centre Hotel, to marine use-particularly in salt water-and for Smiths London, WC2 March 13 to 15 to push the standard product for this purpose is surely not good policy.

PracticalElectronics March1973 253 4111k

conductor by a pin connector accountthe high coldcurrent WIRING HARNESSES FOR CARS which bites through the insulating surgesinvolvedinlightingmost materialandintotheconductor. vehicle lamps. The Ford Motor Company patent Similar power connectors can be Although SCR's may be usedit No. 1 287 074 is concerned mainly usedtoconnect the power con- is easierand cheaperto use with wiring harnesses for cars but ductortoanyelectricaldevice switch resistors R1 and R2 most electronic enthusiasts will see whichrequiresa permanent sup- (around 100 ohms each)which, far wider applications. ply of power. together with the resistances con- In a vehicle all the various elec- Each remote electricalfunction nected between the emitters and trics,such assidelights, head- thatrequiresonly a switchable bases of the transistors, form lights.stoplights and Wipersare power supply (such as headlights, Potentialdividers which hold the usually connectedto a power etc)isconnectedtothepower base potentials constant at a level source by separate power carrying connector by a gated plug.The to which they fallon closing the cables. The electrics are con- gated plugs each house atran- switch.Current through the tran- trolled by switches (usually sistor of which the emitter isper- sistor can only increase untilthe locatedinside the vehicle remote manently connected to the power voltageacrossthelowemitter fromthedevices)intheoower conductor. resistance(cable resistance, etc) cables from one of the supply ter- A resistor of around 1,000 ohms raisestheemitterpotentialtoa minals.The vehicle chassis acts isconnectedbetweenthebase similar value to the base potential. as a common return to complete and emitter of the transistor the circuit to the other supply ter- and the base of the transistoris minal. alsoconnectedtotherequired Providing heavy duty power controlconductorofthewiring BIO-NOTES linesforeachseparateremote harness. The transistor collector is electrical function is uneconomical. connectedexternallytowhatever Readers of Gerry Brown's fasci- The Ford systemis based on the electrical function is to be natingcolumnwillhavenoticed house "ring main" idea and uses powered, Fig. 2. his comments in the January 1973 a flatstrip power conductor cap- Thegateis controlledby a issue concerning"Electrophonic able of handling the total current trigger signal from the control con- Hearing" and his loadforallthe vehicle electrics, ductor and willonly pass current the effect of feeding electric cur- see Fig. 1. toitsload when a control signal rents direct to the brain should be Thestripconductorisflexible is present. re-examined as apossible aidto and is coated with flexible insulat- InFig.2,theelectricalfunc- the deaf. ingmaterial. On thesurfaceof tions or loads are lamps LP1 and Anyone wishingtofollowthis the insulating material a thin con- LP2. When manualswitches S1 line of research will be interested ducting layer isdeposited and and S2 are "off" the base of tran- by thecontentoftwo British 1 286 etched awaytoform a parallel sistors TR1 and TR2 areatthe patents Nos. 284 158 and 1 series ofthin low current control same potential as the emitters and 316respectivelyfromtheZCM conductors. Eachofthese has neithertransistorconducts;thus Corporation of USA and Hermann connecting pads spaced out along lamps LP1 and LP2 do not light. Mengeler of Germany. Both itslength and Ford suggest that Ifswitch S1 isturned "on" the patents were published some while in a practical system 20 to potential of control conductor CC1 ago but each contains useful tech- 30 controlconductors can be falls, transistor TR1 is switched on nical information on the subject. used along with one main power andcurrentflowsthroughlamp The ZCM patent details a conductor. LP1. Similarly if switch S2 is method ofusing an audio signal The vehicle power source is per- turnedon,current flows through to pulse a microwave radio signal, manently connected to the power lamp LP2.The circuit takes into the resultant pulses being then fed toelectrodeswhicharecapaci- tively coupled to the subject's skin. This is claimed to produce a brain sensation in some respects equiva- lent to hearing. BP1 287 074 The Mengeler patent claimsa comparable system for introducing Law o.rnwil video information to the brain. In brief, a miniature TV camera pro- duces a scanning voltage which is capacitivelycoupledtothesub- ject'stemples. Thissupposedly stimulatestheoptic nerveand produces sensationswhichthe subject may train himself to equate with sight sensations. Reference to these two oatents before experimentation could well save readers wasted time and work Fig. 1 Fig. 2 -it could also save their subjects unnecessary electric shocks.

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PracticalElectronics March 1973 255 LINDAIR (ELECTRO-TECH) LTD "PRECISION FAN CO." (Smiths Industrie") DOUBLE FURTHER BULK PURCHASE ENTRY CENTRIFUGAL FAN/ BLOWEIL-This is a beauti- fullybalanced,particularly SILVANA quietrunningunitgiving approx. 90cubicft./min. MAGNETIC SWITCHI The motor is a 2 pole shaded pole 240V Mycalex, drawing NOW COMPLETE WITH REFERENCE only 240ma on run.Weight MAGNET! A magnificently activated switch. 2116. Sizes: Case dia. 31 in., width (cane only) 3.125in., Vacuum sealed in a glass envelope. Silver width overall (inc. motor) 5.25in., aperture 3.1251n. by contacts normally closed, rated 3 amp at TANGENTIAL HEATER 1951n.Offered well below makers' price at 12.95 120V, 1; amp at 240V. Size (approx.) 11.* long P. & P. 25p. 1" dia. Ideal for Burglar Alarms, Security systems, Silently driven by a shaded pole etc., and wherever non -mechanical Mycalex motor. Compact, powerful switching is required.New Lower and quiet running with aluminium Price. Only 18-10 for 12, 18 for 50 impeller (outlet 5f X 1(1.Mains AMPEX 7.017 D.C. MOTOR. This c 115 for 100 complete with magnet. voltage. PLUS matching heater unit £16o is an ultra -precision tape motor £21 with spiral element. May be switched.. designed for use in the AMPEX for 500 or 1,000 watts.PRICE ONLY 1". & P. 50p model AG20 portablerecorder. Torque 450GM/CM. Stall load at 500ma. Draws 60maonrun. PROGRAMMER TIMER 600 rpm ±5% (+peed adjustment, SYNCHRONOUS Internal AF/RF suppression,I" BY HONEYWELL dia. X 1' spindle, motor 3' dia. AUTO -RESET XI ;". Original cost £16.50. Our price 61.86. P. & P. 25p. Large quantity available (special quotations). PROCESS Mu -metal enclosure available 76p each. TIMER By LONDEX LIMITED "SOILIDIG" MAINS SOLENOID. 1' travel, 181b. Type IMP Mk, 8 Brand New and Boxed. These well pull (approx.). Size: 21" long known timers are already in world-wide use and are X 21* x sr high. Powerful perfect for Industrial Electronic Timing, Research and 11-75. P. & P. 25p. for all machine control timing problems. Repetitive accuracy better than 0.5% of full scale setting. Two or "DATE/WET" MAIDS SOLI:1101D. 1' travel. 81b. A bank of 15 micro -switches are each independently more can be interconnected to give control of a series pull (approx.).Size:2;" long x 2,5" x 2' high. operated by 15 pairs of cams which in turn are individu- of processes, 230/250V. 50Hz, also Similarin appearance to "SORENG 11.85. P. & P. ally adjustable to give switching periods of zero to available 8011z.15 minutes fullOUR PRICE 25p. 12 seconds with infinitely variable combinations. A scale, 15 gees. per division. Driven ONLY mains synchronous motor drives the cam shaft at 1 rev. by self-starting sync. motor. Con- per 12 seconds (5 R.P.M.).Designed originally for tact rating 5 amp at 250V a.c. In- NEW AND UNUSED vending machines at a cost of 11540 corporates solenoid operated clutch Postal or carriage charges are for Brut Britain only. plus. Many applications where con- alsolever actuated micro switches. tinuous sequence programmes are Normal pric probably in excess of We welcomeordersfromestablished companies, £650 educational depts., etc.All orders under 12-50, cash required, such as lighting effects, etc. E16. Complete with multi -pin con- with order please. New in original makers' cartons. First nector as illustrated. class value at 15.75 plus 25p P. & P. £5.75

315 EDGWARE ROAD, LONDON W.2. Tel. 01-723 5667 Open 9 a.m.-6 p.m. MON. to SAT.

LOUDSPEAKER TRANSISTOR AUDIO ZIGGY'S 2001 ELECTRONICS Co. Ltd. BARGAINS AND RADIO CIRCUITS by MULLARD Fine Pop 100 Watt IV 8/15 ohm 119.50 RARE BARGAINS Fans Pop 60 Watt 15" 8/15 ohm E1115 LI .80. Postage 12p. Fane Pop 50 Watt 12"8/15 ohm C925 SPECS. MULTIMETER Pane Pop 25/2 12" 25 watts 8!15 ohm £5.40 U4324. Sensitivity 20,000 OPV Fane Pop 1512" 10 watts 8/15 ohm £4.00 TRANSISTORIZED RADIO CONTROL DC. Usually high current . Baker Group 25 12" 3, 8 or 15 ohm E660 FOR MODELS by D. W. Aldridge. 62.50. 3 amps AC/DC. Voltages Baker Group 35 12" 3, 8 or 15 ohm £8,00 Postage 12p. AC3 to 900V DC. 0.6 to 1200V. CelestIon PS8 for Unilex £2.35 HI Fl YEAR BOOK 1973.L150. Postage Resistance 500ohms -20-200- EMI 13 x 8, 3, 8 or 15 ohms £2 25 20 p. 2,000K ohms. Transmission EMI 13 x 8 3, 8 or 15 ohms £2 60 level - 10 to + I2db.This high EMI 13 x 8 twin tweeter 3, 8 or 15 ohms E3-110 BEGINNER'S GUIDE TO TELEVISION quality instrument has diode EMI 13 x 8 type 350 15 watt 8 ohm £8.00 by Gordon J. King.LI.60.Postage 10P. protection. Complete with Richard Allen 8" 3, 8 or 15 ohm. E2.35 9 test leads, batteries, etc. Richard Allen 12" dual cone 3 or 15 ohm £2.50 RADIO TECHNICIAN'S BENCH PRICE ID plus 25p post, etc. Pane 8" dual cone 808T8 or 15 ohm £2'85 MANUAL by H. W. Hellyer. L3. Postage OTHER RUSSIAN METERS IN STOCK Fane8"d/cone roll surround 80778 or 15 ohm £3 50 15p. AT BARGAIN PRICES. Model U435, £8; Elan 59RM109 9" x 5" 15 ohm E270 INTEGRATED CIRCUIT POCKET BOOK U4312, 6810; U4313, 1940; U434I,19.50. Elac 59RM114 9" 0 5' 8 ohm E270 by R. G. Hibberd.0.50, Postage 12p. Packing and postage, 25p. Elac 61 dicone 8 ohm E225 NEW TTC SPRITE HEADPHONES IN Elac 63" d/cone, roll surround 8 ohm £3 50 FIELD EFFECT TRANSISTORS by RED. Quality stereo phones at only 6145 plus Elac 4' tweeter 8 ohm CI 50 MULLARD.El .00. Postage 12p. 15p postage. Crossover for above (p. & p. tree) £1 50 HAM RADIO: A BEGINNER'S GUIDEby EAGLE LT700 TRANS., LT44 TRANS. ES, 75 Goodman, 8 P, 8 or 15 ohm R. H.Warring. El.64). Postage 12p. Our price 32p each, postage 6p. Goodman' 10 P. 8 or 15 ohm 1E5 25 TWEETERS BY TTC, Type K2006 Horn,, Goodmans 12 P, 8 or 15 ohm E10 50 110 THYRISTOR PROJECTS USING lk-18k, [1.50. 13 or ISO. Type 32007 Horn, El, Goodmana 15 P, 8 or 15 ohm E17 00 SCRs AND TRIACS by R. M. Marston. 6140. SO. Type K2011 Dome, 6345 BO. Packing and Goodmans 18 P, 8 or 15 ohms E27 50 Postage Sp. postage 20p-N.B. crossovers must be used 2', 23' or 3' 80 ohm 65 to avoid damage. Phillips 5.8 ohm £195 50 PHOTOELECTRIC CIRCUITS AND SUBMINIATURE TOGGLE SWITCHES 7" x 4" or 8" x 5" 3 or 8 ohm £1 50 SYSTEMS by P. S. Smith.LI-30. Postage 8p. -very useful, very small. S/P 2.5p, DP/ST, 33p; 10" x 6" 3, 8 or 15 ohm £2 00 FOUNDATIONS OF WIRELESS AND DP/DT, 45p. Postage Sp each, over 10, post free. ELECTRONICS by M. G. Scroggie.£1.80. SUBMINIATURE MAINS TRANSFOR- FREE with orders over £6-"Hi-Fi Loudspeaker Postage 25p. MERS. Eagle MT6, 6.0-6,100 M/A. 80p, Enclosures"book, postage10p. MTI2, 12-0-12, SO M/A, 800. RADIO VALVE & TRANSISTOR DATA postage 10p. All units guaranteed new and perfect. by A. M. Ball.75p. . Postage 12p. MINIATURE TYPE MAINS TRANS- Prompt despatch p. & p. 25p per speaker. FORMERS. EagleType MT280,6-0-6, 280 M/A, II -20;MT150. 12-0-12, ISOM/A. 1140, MTI00, 24-0-24, 100 M/A, 6140. R/S OySeasMpIPL0,-511761'.. ;OsTtaappinpt1P06n.mitrilaV: WILMSLOW THE MODERN BOOK CO. cure size. UT46 Unijunctions, 25p plus 3p postage. BRITAIN'S LARGEST STOCKIST E/S Screw BATTEN HOLDERS.Ideal for AUDIO, Dept. PE of British and American Technical Books spots, lamps, etc. Top class, 48p plus 7p postage. FOR D ELIVERY OF THESE 10 Swan St., Wilmslow, 19-21 PRAED STREET MINTSPEEDYCONDITION COMPONENTS LONDON W2 1 NP PLEASE SEND C.W.O. to ZIGGY'S 2001 Cheshire, SK9 1HF ELECTRONICS CO. LTD., DEPT. P.E., Phone 01-723 4185 34 MABLEY STREET, LONDON, E.9 Closed Saturday Ip.m.

256 PracticalElectronics March 1973 OF TEST EQUIPMENT 1000's BARGAINS! R 1100 0 bpi WO V The famous DIGITEST 500

1'1

500V 500140 sm. 50 v . 50 wn

SH II A SIMPLE II ALL-AROUND A PROFESSIONAL DIGITAL MULTIMETER BRAND NEW AT A FRACTION OF THE ORIGINAL PRICE! 3 digit plus polarity indicator. Its17 positions allow it to measure in the following ranges: d.c. volts100µV to 999V; a.c. volts100IAV to 420V; d.c. 100µA; a.c. 100µA. Resistance 0.10 to 999k0 Operates from 230V 50Hz. 12V d.c. external. Dry cells or Ni Cad batteries. 50p Original Price CE19. OUR PRICE 55 PLUSP. & P. SECURITY BRAND NEW DIGITAL PANEL VOLTMETERS 10mV toI .99V, 199 measuring points.Input Z =.100M0 Automatic zeroing.Dimensions PLUS 72mm H x 72mm W x 155mm D. 50p OriginalPrice 02. OUR PRICE22450P. & P CANNON XLR AUDIO0.150 AUDIO WATTMETER SERIES Dual range 0-50 and 0-150W. 15 ohms XL3-I 13 -pole socket (free, lineimpedance. Dimensions 10in x Tin x 4in. ALARM mounting),XL3-32 3 -pole Ideal for determining output power of plug (chassis mounting). L1.25 P.A. systems, audio amplifiers, etc.,etc. per pair Supplied as new.Price L1610 post paid. XL6-32 6 -pole (chassis mount- ing).XL6-I 16 -polesocket HELICAL POTENTIOMETERS Secure your house and holdings against burglars (free,line mounting). [1.50 STC Relcon,10 -turn, Type No. HEL/ per pair 07/-10/1/001/A. Following values supplied or vandals with this bridge balanced sense loop XL3.32 3 -pole plug.75p each ex -stock. that cannot be tampered with. BARGAIN OFFER-LOW Res. 5000 lI% 11,11 Skil 201,0 VOLTAGE STABILISED All above Helicals are brand new stock. Easy to build three transistor design with low POWER SUPPLIES Quantities available.Price LI25 each. running costs. Voltage Range 16-24V. P. & P. 5p for one. Current Range to 6A. Beckman Type AHelicalpots.SW. 10 turn. Resistancesavailable. 30k0 Full over -voltage and Current and 501,0.Brand new and boxed. protection. Price L1.75 each. AC Ripple content better than Bournes Helicalpots.Miniature type. SmV. Resistance !Oki).Brand new.Price These PSUsareconstructed LI SO. to exacting standards and incorporate the very best 10-15V D.C. REGULATED, STABI- ofcomponents and circuit LISED P.S.Us. design for long life and relia-Rating IA.Measurements: B,Finx Sin x bility. Employs Silicontran- 4in. Limited quantity, cannot be repeated. sistors, thyrissors, C -Core Brand new units only. Price £650 post NOVEL BATTERY ELIMINATOR transformer,etc.Offeredin paid. perfect condition, carefully checked before despatch.List MULLARD FERROX-CUBES A d.c. power supply unit with the unusual feature price over C125. Our price Type LA4.Brand new boxed.Price 95p. only L26.50. Carriage El. P. & P. inc. of being contained within a flat pin mains plug. AERIAL CHANGEOVER RELAYS Simply plug thisin and you have a regulated of current manufacture designed especially for mobile equipments, coil supply of 60mA at 9V suitable for your radio, voltage 12V, frequency up to 250MHz at SOW.Small size only, 2 in. x. in. cassette or record player. Offered brand new, boxed. Price LI50, inc. P. & P. ADVANCE AUDIO OSCILLATOR TYPE J.I. 1SHz to SOkHz in 3 ranges. Output 0-25V into 6000.In good, serviceable condition.PRICE 115.50.P. & P. 50p. Special Feature WE SPECIALISE IN SUPPLYING NEW AND ELECTRONIC TIMEPIECES -2 USED TEST EQUIPMENT .. to industry, educational establishments and private enthusiasts.Whatever The evolution of electronic timepieces your requirements: signal generators, audio oscillators, frequency meters, oscilloscopes (by Tektronix and other leading makers), high and low voltage power supply units, relays (simple or special), panel meters, chart recorders, etc.-a telephone call to us could save you pounds!

P. F. RALFE PRACTICAL IO CHAPEL STREET, LONDON, N.W.I Tel. 01-723 8753 ELECTRONICS PracticalElectronics March 1973 APRIL ISSUE ON SALE MARCH 9 /7 pulse train is passed to a chain of . SPECIAL OFFERS three cascaded pump circuits. Com- ponent values have been so chosen Here is a chance to stock up with solid state devices at bargain prices. that the incoming pulse is summed We have been advised by A. Mar- MARKET inunits, tens, and hundreds. A "ring -of -ten"counter strobes shall & Son Ltd.,thattheirad- eachNixienumeralterminalin vertisement next month willlista sequence and for each strobe "tops seriesofspecialoffers,available up" the pump circuits. This action only to readers of this magazine. PLACE This well-known component sup- isused to time the point in the strobesequence when the supply plierwillbe disposing of alarge Items mentionedinthis feature are usually amount of stock at reduced prices, available from electronic equipment and com- is switched onto the relevant Nixie prior to moving into new premises. ponent retailers advertising inthis magazine. to illuminate the correct numeral. However, wherea fulladdress is given, This instrumentisavailable, by enquiries and orders should then be made direct mail order, direct from the makers, to the firm concerned. SinclairRadionicsLtd.,London Road, St. Ives, Huntingdonshire.

CASES Encouragedbythesuccessof LOW COST DIGITAL their Contil Mod -2 range of instru- ment cases, West Hyde Develop- MULTIMETER mentsrecentlylaunchedanew A new £49digitalmultimeter complementary range of cases fromSinclairRadionicspromises designated Mod -3 types. tobeastrong contenderinthe The Mod -3 cases have fixed sides, professionalquality meter market in scuff resistant p.v.c. coated steel. having asit does a claimed high made of two parts rigidly locked accuracy,highinputimpedance, together. A chassis is supplied with portability, and relative low cost. It the case, this and the panels being made up first and then assembled is aimed at the replacement market Contil Mod -3 casesfromWest asaneconomicalsubstitutefor afterwards in the case. Hyde Developments analogue multimeters. Interior drilled side flanges allow Measuring 190 x130 x 58mm the chassis plate to be positioned in andweighingIflb(0.6kg),the any convenient position. The side multimeter can easily be held in the flanges also take the rear and front hand when making measurements. panel fixing screws. The leads are fixed to theinstru- Case dimensions vary from 3in ment and wrap around a recess in x 7in to 6in x1 lin and further the lightweight polypropylene case. details and price list can be obtained Simpleyeteffectivefingerplate fromWestHydeDevelopments selector switches form an integral Ltd., Ryefield Crescent, Northwood part of the case. Hills, Northwood, Middlesex. The instrument has ranges extend- ing from 1µA up to IA d.c., ImV to1,000Vd.c.anda.c.,andre- sistance ranges from 1,000 ohms to WAFER SWITCHES 1Mf2 full scale. Display is by three The wafer switchisstill one of Nixies with a carry of one in a thewidestusedcomponentsin single neon. This gives an effective electronics,andUltraElectronics 31digitswithout usingafourth (Components) Ltd are now market- tube. ing a range of wafer switch kits. The measuring technique is such One of theadvantagesofthe as to reduce current consumption switch kit is its versatility and ease TheSinclairlow to a minimum, in fact, the manu- with which the designer can make cost digitalmulti - facturer's specification promises 80 up prototype switching assemblies meter hours of switched -on operation with and change them on the spot. a current drain of 12mA. TheCentralabSwitchkitsare Input impedance is very high at packaged asseparate components: L000mn comparedtoanalogue the Series PA 1000 and PA 2000 meters, as are the accuracy para- kitcontains,forexample.1.000 meters of 0.4 per cent on volts d.c., clips,800eyelets,925contacts. and 1 per cent on a.c. with an f.s.d. stators,rotors,nutsandpacking error of ± 2 digits. washers, plus 25 index assemblies. Aninterestingaspectofthe 25 adjustable stops, eyeletting pliers circuit is that it is all discrete, with and assembly tools and instructions. a component count of around 300 Further information and details (including 100 transistors) all of the switch kits can be obtained mounted on three p.c.b.s. from Ultra Electronics (Com- In operationall inputs are ponents) Ltd.. Fassetts Road. Loud - brought within a IV range and the water, Bucks. incomingsignalsareanalogue -to - Also available from Ultra Elec- digitalconvertedtoproduce a tronicsisafree switchwallchart pulse. train the length of which is giving typical ratings and configura- proportional to the input level. The tions.

258 PracticalElectronics March 1973 BELLING LEE INSULATED TERMINALS. Red or Black, 3 atop max. 10p pair. p.p. 3ip ELECTRONIC BARGAINS BERCOSTAT WIREWOUND RHEOSTAT.50 volt, 8000,23 watts, tin dia.259, P.P. 71P. SOLDERING IRONS Wouldyou spend FINNED ALUMINIUM HEATSINK. Sin x1 I in. Recommended Our Ready drilled.209, p.p. 61p. Retail Price SUB -MIN. CHOC. CLIPS. Red or Black, insulated 4p. Price Min. quantity, 6, p.p. 31p. Antex CCN240 LI .80 L1.44

GARRARD MAG. TAPE DECKS: I 50V, Antex CN240 E170 El .36 an hour a day solenoid operatedbrakes,etc.Mainsvoltage motors 1740 each, p.p. RI 23. Antex X25 £1.75 LIAO 41in PLANNAIR FANS. Complete. capacitor, en equip. 2.800 r.p.m.23.50, p.p. 40p. STEREO HEADPHONES ELECTRIC MOTORS, HOOVER OR CROMPTON MD802. Frequency 20-18,000 c.p.s. to earn more money PARKINSON.2301'.Single phase a.c. 8 ohm £3.50 £2.25 h.p., 1,440 r.p.m.. 13.75, p.p. XI. h.p., 1,423 r.p.m. or 2,800 r.p.m.. /11.75, MD806, Frequency 20-20,000 c.p.s. p.p. el .25. 8 ohm 03.00 £4.95 * h.p., 1,440 r.p.m., 12-2.5, p.p. 731I. Coiled Headphone in Electronics- AUDIO CONNECTORS 3 pin Din Plug lap each. Extension Lead £I.35 5 pin Din Plug A type, B type 13p ..

2 pin Din Speaker Plug/Socket 10p 3 pin Din Line Socket 18p AMPLIFIER MODULE 3.5mm Jack Plug Screened.. 10p .1 Amplifier module AEI000 3 watt, Television -Radio ? Standard Jack Plug.. 10p of £2.37. 5 watt, B. Screened Standard Jack Plugs 15p Stereo Jack Plug 18p If you're willing to give up one hour or 18p FERR Screened Stereo Jack Plug .. NTI RADIO CHIP, more a day we can help you get into the Phono Plugs: Red or Black 8p each. ZN41 EI12 P.p. on above items 3*p. lucrative growth industries of electronics, MAINS NEONS D.I.L.RCDERS-14 pj television, radio. Red or Green.Size: tin x 15p, of, 3*p. 16 pin, 16p. And if you're already in, we can help LEVER ACTION P.0.1000 TYPE SWITCHES Lock 4 -pole changeover, 15p, p.p. alp.Ex equip. COMPACT CASSETTE you get on! Lock 2 -pole changeover, 10p, p.p. 3f.Ex equip. With our know-how and wide experience AUDIO LEADS in teaching, plus your determination to Screened Phono Leads 46in long, 15p. C60 30p 87p L250 3.5mm JACK/3-3mm JACK 71t 61n long, 40p. study, we can turn your interest into the 5 -Pin Din A Type, 3 -PIN A TYPE.Approx. oft C90 40p LI17 E3.50 technical knowledge you need for success. long, 70p. P.p. on above items 5*p. Cassette Head Gleaners 32p Once you've got the qualificationsyou 8 -track Head Cleaners need, you'll be in a good position to take MULLARD & MALLORY SCREW TERMINA 75p CAPACITORS 4,50051, 64V, 7,100µF 40V, 50p each full advantage of the opportunities which 20,000 30V, 23,000 25V, 35,00013V, 80p each Fully Guaranteed. Mail Order only exist today in all fields of electronics -in p.p. 10p. Cheque or P/O to: P. & P. 13p television (colour and black/white) and in WILLARD FULLWAVE RECTIFIERS radio.(We teach youthe theory and 6.48V, 13 amp, 70p, P.P. Sip. T. F. J. ELECTRONICS practice of valve and transistor portable BELLING LEE 1.3 amp in -linerubber covered 25 EASTBURY COURT circuits while you build your own 5 valve interference suppressor, 26p. PP. SP. LEMSFORD ROAD receiver, transistor portable and high grade RUBBER 3 PIN 5 AMP NON -REVERSIBLE CABLE ST. ALBANS, HERTS. CONNECTORS. 20p, p.p. Sip. test instruments.) SOLENOIDS 12 VOLT PULL ACTION With ICS you study at home -at your 2in X lin x 1in, 40p, p.p. Op. own pace, when you choose, in the time SIEMENS MINIATURERELAY.Doublepole you've got available.Your ICS tutors will changeover dust evver/base 48V, 2500, 50p, p.p. 5p new. give you all the help and encouragement you need to pass any exams you want to OMRON MK2 MIDGET POWER RELAY.12V d.c. Double pole changeover.New, 70p, p.p. Sp. take. STC MINIATURE RELAY 240 O, perspex cover, Don't waste another day. Take your first 6.15V new. 36P, It P. 5P. step now towards a better paid, more GARDNER'S POTTED TRANSFORMER, 0250V. assuredfuture. Send foryour FREE Input: 18V 500m/n, 30V 130m/a, 6V 250m/a output. Size: Sin x 21in x 21iti.SI, p.p. 20p. Ex equip. Careers Guide today. tested. ICSyour lasylo TELESCOPIC AERIALS n £725 of opportunitythe door Chromed 7in closed, 28in extended. 6 section ball Solve your communica- Jointed base, 25p, p.p. Sp new. tion problems with this 4 -Station Transistor Intercom system a master and Tick or state subject of interest and post to: MIILLARD 4 DM 160 INDICATORS inplastic 3 Subs), in deluxe plastic cabinets for desk or wall holder/cover, ex equip., sizea.. mounting.Call:talk:listen from Master to Subs and I International Correspondence Schools khriffirmx.p....fily Sobs to Master.Ideally suitable for Business, Sur- Dept. 230D, Intertext House, Stewarts Road gery, Schools, Hospital, Office and Home.Operates ILondon SW8 41.11 PRINTED CIRCUIT BOARD/19 ACY 19's 10 0A200 on one SN' battery. On/off switch.Volume control. Diodes: I reed relay: 1 AZ 229 zenner ass. capacitor/ Complete with :1 connecting wires each 6fift. and Subject of interest resistors.Power supply 22V, 250 rn/A d.c. Output other accessories.P. & P. 40p. 240V a.c.11, p.p. 29p.Ex equip. MAINS INTERCOM (new model) Society of Engineers Graduateship No batteries -no wires.Just plug in the mains for (Electrical Engineering) U.Irg.KELYVarious colours.330yd, 8011, p.p. 20p. instant two-way, loud and cleareornmunication. On/off switch and volume control with lock C & G Telecommunications Technicians TOGGLE SWITCHES.Double throw.Ex equip, P. & P. 35p extra. Certificates new condition, 75p doz., p.p. 13p. Price 114.40. C & G Electrical Installation Work TOGGLE SWITCHES.Single pole, double throw. Ex equip., new condition, 50p doz., p.p.13p. INTERCOM/BABY ALARM C & G Certificate in Technical PAINTON PLUG SOCKETS.Type 155 series. Communication Techniques Working voltage 330V ac./d.c. current, max. 3 amp MPT General Certificate in Radio a.c./d.c. 7 pin plug and socket, 50p, p.p. 6p.15 pin Telegraphy plug and socket, 51, p.p. 6p.31 WAY PLUG AND SOCKET, 11.150, p.p. Op. Audio, Radio & TV Engineering & Servicing CASH WITH ORDER PLEASE Electronic Engineering, Maintenance, Same as 4 -Station Intercom for two-way instant Engineering systems, lnstrumention & communication.Ideal as Baby Alarm and Door Phone.Completewith6fift. connectingwire. Control systems FIELD Battery 14p.P. & P. 25p. Computer Engineering and Technology TionsistriTEIEPHONEMPI/PER Electrical Engineering, Installations, ELECTRIC Contracting, Appliances Self -build radio courses LIMITED 1111114 " £2.99 Why not boost Name 3 Shenley Road !stillness effi- ciency with this incredible De -Luxe Telephone Ampli- Address Borehamwood, Herts. fier. Take down long telephone messages or converse without holding the handset. A useful office aid. On/ Adjacent Elstree Mainline Station off switch. Volume control. Battery 14p extra. P. & P. Occupation.. Age_ 22p.Full price refunded if not satisfied in 7 days. IAccreditedbtheCouncil for the Accreditation Tel.: 01-953 6009 WEST LONDON DIRECT SUPPLIES (PE/3) Correspondence Colleges 168 KENSINGTON HIGH STREET, LONDON, W.8 L_

PracticalElectronics March 1973 259 Sinclair Project 60 Project 60 Stereo FM Tuner

STEREO fair FM TUNER Built and tested. Fry 88 90 92 94 96 98 100 102 104 106 108 Mhl, Post free. £25 30 35 40 45 50 55 Chastely 5 10 ' 15 20 25 411 with phase lock loop principle

Amongst the many advanced electronic features to be found inthis SPECIFICIATIONS Number of transistors: 16 plus 20 in I.C. remarkable stereo tuner, use of the phase lock loop principle ensures Tuning range: 87.5 to 108MHz. standards of audio quality better than from any other method of detection Sensitivity: 7kLV for lock -in over full de- circuit coils, an viation. yet used. Varicap diode tuning, accurately formed printed Squelch level: typically 20 I.C. in the special stereo decoder section and switchable squelch circuit Signal to noise ratio: ± 65dB for silent tuning between stations contribute to the unsurpassed per- Audio frequency response: 10Hz-15Khz formance of this tuner, irrespective of price consideration. But the Project Total harmonic distortion:0.15% for 60 FM Stereo Tuner is far from expensive - indeed, it offers fantastic value 30% modulation. Stereo decoder operating level2 µV. for money and will bring the thrill of stereo radio to many who previously Crosstalk: 40dB may not have to afford it. The tuner may be used with any good Output voltage: R M S max. 60 modules, (typically 250mV. stereo) system as well as Project 60, but if you use it with other Project Operating voltage: 25-30V DC at 100mA. you will find the matching front panels particularlyimpressive in ap- Indicators: Stereo ontuning. pearance as well as function. Size: 93 k. 40 v 207mm.

Integrated circuit Super IC.12high fidelity amplifier

sistor circuit contained within a16 lead DI L package, and the finned heat sink is sufficient for all requirements. The Super IC.12 is compatible with Project 60 modules which would be used with the Z.50 and Z.30 amplifiers. Complete with The easy way free manual and printed circuit board. to buy and build SPECIFICATIONS Output power: 6 watts R MS continuous (12 Project 60 watts peak) 6-80. Frequency Response: 5Hz to 100KHz ldB Total Harmonic Distortion: Project 605 is one pack containingone PZ5. Less than 1%(Typical 0.1%)atalloutput two 230's. one Stereo 60 and one Masterlink. powers and frequencies in the audio band (28V) This new module contains all the input sockets Load Impedance: 3 to 15 ohms. Input Im- Having introduced Integrated Circuits to hi-fi and output components needed together with all pedance: 250 Kohms nominal. Power Gain: necessary leads cut to length and fitted with neat constructors with the IC.10. the first time an IC 90dB (1.000.000.000 times)afterfeedback had ever been made available for such purposes. little clips to plug straight on to the modules. Supply Voltage: 6 to 28V Quiescent cur- Thus all soldering and hunting for the odd part is we have followed it with an even more efficient 4528rnm in. rent: 8mA at 28V Size: 22 eliminated. You will be able to add further Project version, the Super IC.12. a most exciting advance cluding pins and heat sink.. over our original unit. This needs very few ex- 60 modules as they become available adapted to Manual evadable separately 15p post free. the Project 605 method of connecting. ternalresistorsand capacitorstomake an astonishingly good high fidelity amplifier for use With FREE printedcircuit Complete Project 605 pack with ail R with pick-up. F.M. radio or small P.A. set up. etc. board and 40 page manual comprehensive manual, post free .1- -ci The free 40 page manual supplied, details many Everything you need to assemble a superb 30 other applications which this remarkableIC. £2.98 Post free watt high fidelity stereo amplifier without having make possible. Itis the equivalent of a 22 tran- to solder.

Sinclair Radionics Ltd, London Road, St. Ives, Huntingdonshire PE17 4HJ. Tel: St. Ives 64311

260 PracticalElectronics March 1973 the world's most advanced high fidelity modules

Z.30 & Z.50 power amplifiers Built, tested and guaranteed with circuits and Instructions manual. Z.30 £4.48z.so £5.48 The Z.30 and Z.50 are of advanced design using silicon epitaxial planar transistors to provide unsur- passed standards of performance. Total harmonic distortion is an incredibly low 0.02% at 15w (8n) and all lower outputs. Whether you use Z.30 or Z.50 amplifiers in your Project 60 system will depend on personal preference, but they are the same size and are intended for use principally with other units in the Project 60 range. Their performance and design are such, however, that Z.50s and Z.30 may be used in a far wider range -of applications. SPECIFICATIONS (Z.50 units aro interchangeable with Z.30s in all applications).- Power Outputs: Z.3015 watts R.M.S. into 8 ohms using 35 volts : 20 watts R.M.S. into 3 ohms using 30 volts. 2.6040 watts R.M.S. into3 ohms using 40 volts 30 watts ,R.M.S. into 8 ohms using 50 volts. Frequency response: 30 to 300.000Hz ± 1dB. Distortion: 0.02% into 8'ohms. Signal to noise ratio: better than 70dB unweighted. Input sensitivity: 250mV into 100 Kohms (for 15w into 8t1). For speakers from 3 to 15 ohms impedance. Size:14 x 80 x 57mm.

Stereo 60 Pre-amp/control unit Built, tested and guaranteed £9.98 Designed specifically for use on Project 60 systems, the Stereo 60 is equally suitable for use with any high quality power amplifier. Since silicon epitaxial planar transistors are used throughout, a really MOM IMP= high signal-to-noise ratio and excellent tracking between channels is achieved. Input selection is by means of press buttons, with accurate equalisation on all input channels. The Stereo 60 is particularly easy to mount. 41004101111 SPECIFICATIONS -Input sensitivities: Radio - up to 3mV. Mag. p.u. 3mV: correct toR.I.A.A. curve 404111:41. +1dB:20 to 25.000 Hz. Ceramic p.u. - up to 3mV Aux - up to 3mV. Output: 250mV. Signal to noise ratio: better than 70dB. Channel matching: within 1dB. Tone controls: TREBLE +12 to -12dB at 10KHz : BASS +12 to -12dB at 100Hz. Front panel: brushed aluminium with black knobs and controls. Size:66 x40 x 207mm.

A.F.U. High & Low Pass Filter Unit Built. tested and guaranteed. £5.98 For use between Stereo 60 unit and two Z.30s or Z.50s. The unit is very easily, mounted and is unique in that the cut-off frequencies are continuously variable. As attenuation in the rejected band is rapid (12dB/octave), there is less loss of the wanted signal than has previously been possible. Amplitude and phase distortion are negligible. The A.F.U. is suitable for use with any other amplifier system. There are two filter sections - rumble (high pass) and scratch (low pass). H.F. cut-off (-3dB) variable from 28KHz to 5KHz. L.F. cut-off (-3dB) variable from 25Hz to 100Hz. Distortion at 1KHz (35V. supply) 0.02% at rated output. Operating voltage from 15 to 35V. Current 3mA. Size: 66 x 40 x 90mm. Power Supply Units

Designed specifically for use with the Project 60 PZ.6 30 volts unstabilised £4.1118 system of your choice. Use PZ.5 for normal Z.30 PZ.8 35 volts stabilised£7.98 assemblies and PZ.6 or PZ.8 where a stabilised supply PZ.8 45 volts stabilised is essential. (less mains transformer)£7.98 PZ.9 mains transformer £15.119 Typical Project 60 applications System The Units to usetogether with Units cost Simple battery Z.30 Crystal P.0 ,1 2V battery£4.48 record player volume control. etc. Mains powered record Z.30, PZ.5 Crystal or ceramic P.U. £9.46 Guarantee player volume control, etc. If. within 3 months of purchasing any product direct from Sinclair Radionics Ltd.. you are dissatisfied with it. your 12W. R MS continuous 2 x Z.30s, Stereo Crystal, ceramic or mag.£23.90 money will be refunded st once. Many Sinclair appointed sine wave stereo amp. for 60; PZ .5 P.U.. F.M.Tuner,- etc. Stockists also offer this same guarantee in co-operation with average needs Sinclair Radionics Ltd. Each Project 60 'nodule is tested before leaving our factory 2 x Z.30s, Stereo High quality ceramic or and is guaranteed to work perfectly. Should any defect arise 25W. RMS continuous £26.90 in normal use. we will Haws it at once and without any sine wave stereo amp. 60; PZ.6 magnetic P.U.. F.M. charge to you, if it is returned within two years from the date using low efficiency (high Tuner, Tape Deck. etc. " of purchase. Outside this period of guarantee a small chugs performance) speakers (typically E1.001 will be made. No charge is made for postage by surface marl. Air Mail is charged at cost. 80W. (3 ohms) RMS 2x Z.509, Stereo As above £34.88 continuous sine wave de 60; PZ.8, mains luxe stereo amplifier. (60W. transformer SINCLAIR RADIONICS, ST IVES, HUNTINGDONSHIRE PE17 4HJ RMS into 8 ohms) Indoor P.A. Z.50, PZ.8. mains Mic.. guitar, speakers, £19.43 Please send transformer etc.. controls I enclose cash/Cheque/money order. F.M. Stereo Tuner (£25) & A.F U. (£5.98) may be added as required. Name

Address PE3/73

PracticalElectronics March1973 261 36V 30 AMP. A.C. or D.C. uperior Quality Precision Made INPUT 230/240V a.c. 50,60 OUTPUT VARIABLE L.T. SUPPLY UNIT NEW POWER RHEOSTATS INPUT 220/240V a.c. VARIABLE 0-260V OUTPUT CONTINUOUSLY 100 WATT. I ohm, 10A; 5 ohm. All Types 4.7A; 10 ohm, 3A; 25 ohm, 2A; fromto 50 amp from stock. VARIABLE 0-36V Fully isolated. Fitted in robust metal case with Volt- SO ohm,I.4A;100 ohm,IA; 250 ohm. 0.7A; SOO ohm, 0.45A;I kfi , 280 mA; SHROUDED TYPE meter. Ammeter PanelIndicatorand handles. 1.5 kr), 230mA; 24 kG, 2A; 3-5k a, 5 ktl, 140mA. I amp, E740 20 amp, L49.00 Input and output fully fused.Ideally suitedfor Diameter3}in Shaft length fin. dia. din. All at 2.5 amp. E845 25 amp, 08.00 Lab. or Industrial use. L70. Post Paid. S amp, 11 1.75 375 amp, 02 00 0.73.Post Paid. 10 amp, £22.50 SO amp, E98 00 50 WATT. I/5/10/25/50/100/250/500/1/ I .5/2.5/5k O. MOTOROLA MAC 11/6 PLASTIC All at 11.23.Post Paid. 15 amp, £25.00 TRIAC 400 PIV. 10 AMP 25 WATT. 10/25/50/100/250/300/500/1/1.5/2.5/3.5/ 2& amp Now available EX STOCK. Supplied with full data 5k(3.All at 98p.Post Paid. (Panel Mounting) amp, £4.75. OPEN TYPE and applications sheet.Price L1.12. Post Paid Black Silver Skirted knob calibrated in Nos. 1-9. I amp, 0.00. 2frnp, 0.05.All carriage paid. Suitable DIAC RCA 40583) 30p each. If in. dia brass bush. Ideal for above Rheostats, lip ea. DOUBLE ENDED MOTOR UNIT STROBE !STROBE! STROBE Powerful, continuously rated, 2 -speed. RELAYS SIEMENS. PLESSEY. Etc. Either 6 or 12 volt D.C. operation. Build a Strobe Unit, using the latest type Xenon MINIATURE RELAYS PRICE 12 incl. P. & P. white light flash tube.Solid state timing and Col.(I ) 2 3 4 triggering circuit.230/250V a.c. operation. Coil ohms 52 3-6 2 c/o 63p. 12 VOLT D.C. MOTOR E XPERIMENTERS' ECONOMY KIT Col. (2) 410 0-18 4 c/o 73p. Speed adjustable I All to 30 flashper sec. Working 600 2-24 4 c/o 78p. Powerful I amp. REVERSIBLE electronic componentsincludingVeroboard d.c. volts motor. Speed 3,750 r.p.m. S.C.R. Unijunction Xenon Tube and instructions 700 6-24 4M 2B 63p. completewith externalgear train 0.55.Post Paid Col. 3 700 6-24 4 c/o 711p. (removable) giving approx. final speed of_ Contracts 700 5-35 2 c/o HD 73p. NEW INDUSTRIAL KIT 700 6-24 6M 65p. either 125 r.p.m. or 240 r.p.m. Size: 44 in Ideallysuitableforschools,laboratories,etc. x 21 in dia. Either type price 93p inc. post. Col. (4) 700 6-12 1 c/o HD 50p. Rollertinprintedcircuit.New triggercoil, Price 700 20-30 6 c/o 73p REVERSIBLE SPLIT PHASE MOTOR plasticthyristor.Speed adjustable1-80f.p.s. 1,250 24-36 4 c/o 63p. 250 r.p.m., 100-115/210-240V A.C., 2in.z I in. Ideal approx. } output of Hy-Lyght. HD =- 2,500 36-45 6M 630 forrim -drivemodels,display,etc. Extremely Price El I.Post Paid. Heavy duty2,400 30-48 4 c/o 500 powerful for size, including small capacitor.75p HY-LYGHT STROBE MK 111 Incl. Base 9,000 40-70 2 c/o Sops post paid. Designed and produced for use in large rooms, Post paid. 15k 85-110 6M 50p. halls and the photographic field and utilises a PARVALUX TYPE 5D19 230/250 VOLT A.C. silica tube, printed circuit, also a special trigger 12 VOLT D.C. RELAY 140 ohm coil REVERSIBLE GEARED MOTORS coil.Speed adjustable 0-20 f.p.s.Light output Type 1: Thr e sets c/o contacts rated at 5 amps. 78p 30r.p.m.40 lb.ins. approx. greater than many (so called 4 Joule) incl. P. & P.(Similar to illustration below.) Positionof drive spindle strobes./12.50.Post Paid. Type 2: One set of c/o contacts. 60p incl. P. & P. adjustable to 3different Type 3: 4-8 volt, 3 c/o HD, 67 ohm coil.78p. angles. M d on THE 'SUPER' HY-LYGHT KIT substantialcast alum- SPECIAL OFFER inium base. Ex -equip- Approx. four times the light output of our well 700 ohm 4c/o. Ex. new equipment. 00 per ment. Tested and in proven Hy-Lyght strobe.Incorporating: 100 incl. bases (minimum 100). first-classrunning order. Heavy duty power supply. A really powerful motor Variable speed from 1-13 flash per sec. 'DIAMOND H' 230 VOLT A.C. offeredat a fractionof Reactor control circuit producing an intense RELAYS (Unused) maker's price. £6.80. Post white light. Three sets c/o contacts rated at 5 amps. Paid. Never before a Strobe Kit with so HIGH an PRICE: 60p.Post Paid. (100 lots /40 outputatso LOW aprice.ONLY 120.75. including P. & P.) PARVALUX Type: SDI.S/ Post Paid. 86896/03 230 VOLT A.C. RELAYS MFG. KEY SWITCH 230/250V A.C. 50 r.p.m. 7 lb/ ATTRACTIVE, ROBUST, FULLY VENTI- One set c/o contacts rated at 7.5 amps.Boxed. LATED METAL CASE. Super Hy-Lyght Kit PRICE: 45p.Post Paid.(100 lots 132 inc. P. & P.) in. Continuously rated. Less including base./6.30.Post Paid. reflector.£745.Post Paid. For Hy-Lyght Kit including reflector./4-45. MINIATURE LATCHING RELAY TYPE: SDI.S/89400/OM 7 -inch POLISHED REFLECTOR Manufactured by Clare -Elliott Ltd. Type F.2 c/o per- 230/250V A.C. 50 r.p.m.22 Ibiin.Continuously Ideally suited for above Strobe kits. manent latching in either direction. Coil 1150 ohm, rated.Incl. busy.0.30.Post Paid. Price 66p. 15-30 Volt D.C. Size' high, wide, r thick. Com- The above motors are new and unused. Post Paid. plete with 3' leads.ew 73p, incl. P. & P. PARVALUX TYPE SD2. 200/250 VOLT RAINBOW STR- OBE FOUR LIGHT U N !SELECTOR SWITCHES A.C./D.C. HIGH SPEED MOTOR CONTROL MODULE Speed 9,000 r.p.m. approx. or 3,200 Will operate four of our 1-1y-Lyght or Super N E W 4 Bank 25 Way r.p.m. if used with built-in governor, 24V d.c. operation.1548, or variable speed over a wide range Hy-Lyght Strobes in either 1, 2, 3, 4 sequence; P. & P. 25p. 6 Bank 25 Way ifusedin 2 + 2;or all together.Thoroughly tested conjunction with our and reliable.Completewithfull con- 24Vd.c.1645. Post Paid. Dimmer Switch, illustrated below. 8 Bank 25 Way, 24Vd.c. PRICE 12. nection instructions. Price: 11845. Post Post Paid. Paid.Send S.A.E. for details. operation. L7.88.Post Paid. 600 WATT DIMMER SWITCH. Easilyfitted. Fullyguaranteed by ..446...COLOUR WHEEL PROJECTOR "HONEYWELL" PUSH BUTTON, PANEL makers. Will control up to 600W of all Complete with oil - MOUNTING MICRO SWITCH ASSEMBLY lightsexceptfluorescentat mains filledcolour wheel. Each bank comprises a c/o rated at voltage. Completewithsimple 10 amps 240V. A.C. Black knob I in. in- 100 watt lamp.200/ Fixing hole } in. ONE bank 30p; structions. i3 incl. P. & P. 240V AC. Features TWO bank 40p; THREE bank1f11'1iD I extremely efficient op- tical system. 118.50+ 55p; incl. P. & P. Quot. for quantity. VENNER ELECTRIC TIME 35p. P. & P. 6 INCH SWITCH 200/250V Ex. GPO. COLOUR WHEEL. 'HONEYWELL' LEVER OPERATED As used forDisco MICRO SWITCH Tested. Manually set 2 on, 2 off every lighting effects, etc.Price 1.5.75 inc. p. & p. I 15 amps 250 volt A.C. c/ con- 24h.Override switch: 15A, £3.45, 20A, tacts. Types N39, N95, N 100. 1345.Post Paid. Also available with BIG BLACK LIGHT NI01 NEW in maker's carton. solar dial ON dusk, OFF dawn.Price as above. PRICE: 10 for E1.90 incl. P. & P. I 400Watt.Mercuryvapour ultra violet lamp. Outer bulb 24 -HOUR TIMER designedtoabsorbvisible Very special offer MICRO SWITCH Can be adjusted to give a switching light and transmit u.v. rays. 5 amp c/o contacts.Fitted with delay of between }hr. to 24 hrs. Extremely compact and removable metal panel Driven by 200/250V A.C. synchronous powerful source of u.v. assembly. Ex. P.O. 20 for 11 inc. motor.15 amp c/o contacts.Mfg. Crater Controls Innumerable industrial appli- post. (Min. order 20.) Ltd.Supplied with scale calibrated 0-10 (2 hrs, cationsalso ideal for stage. per division). display, discos, etc. P.F. ballast Brand New. a. Post Paid. is essential with these bulbs. Price of matched ballast and METER BARGAINS HONEYWELL PROGRAMME TIMERS bulb 11640.Post Paid. BALANCE/LEVEL METERS 240V. A.C. 5 r.p.m. motor. Spare bulb /7.30. Post Paid. 100-0-100 Micro Amp. Size Ifin + If in 4 Each cam operating a c/o BLACK LIGHT FLUORESCENT U.V. TUBES in. Price only 75p including P. & P. micro switch. Cams are 4ft. 40 watt.Price £5.80 incl. P. & P.(For individuallyvariable,allow- use in standard bi-pin fluorescent fittings). AMMETERS NEW! 24 in. Flush ing inumerable combinations. MINI 9 in. 6 watt black light U.V. tube. 11.0. round. Available in D.C. Amps 1, 5, IS. Ideally suited for machinery Post Paid. 20 or A.C. Amps I, 5,10, 15, 20, both control, automation, etc. - - _ types 1145 incl. P. & P. 0-300V. A.C. Also in the field of entertainment, for chaser lights, £1.90 incl. P. P, animated displays, etc. 15 cam model CC Post Paid. SO inI ELECTRONIC PROJECT KIT 10 cam model 1.5.Post Paid 50 easy to buildProjects. Nosoldering, no INSULATION TESTERS NEW! 2 cam model with 15 r.p.m. motor £2.Post Paid. special tools required. The kit includes Speaker, Test to I.E.E. Spec. Rugged metal Meter, Relay, Transformer, plus a host of other construction, suitable for bench or SIMPLE12 CAM PROGRAMMER with 4 componentsand a 56 -page instructionleaflet. field work, constant speed clutch. adjustable cams and 8 that may be profiled to Some examples of the 50 possible Projects are. Size L.Bin, W.4in, H.6in, weight 61b. individualrequirements, available with 15 or 13 Sound Level Meter, 2 Transistor Radio. Amplifier, 1,000V, 1,000 megohms,134.00 r.p.m. motor, L3.75.Post Paid. etc.Price £8.05.Post Paid. carriage paid. 500V 500 megohms, E28 incl. P. & P All Mail Orders -Callers -Ample Parking Dept. PE3, 57 BRIDGMAN ROAD Personal callers only.Open Sat. CHISWICK, LONDON W4 5BB SERVICE 9 LITTLE NEWPORT STREET Phone 01-995 1560 LONDON WC2H 7JJ Showroom open Mon. -Fri. TRADING CO. Phone 01-437 0576

262 PracticalElectronics March 1973 luipiammemammornom. 'Where canIgetexclusive units at lowest es?".. OLSON AWN 4 -WATT STEREO AMPLIFIER pe Here's marvellous value for kimono pot starting to sat them selves up in audio! At only (10 50. yoa gel a fine amplifier in a scratch resilient metal cabinet. with a smart brushed eluniinuim front panel. It incorporstos separate tone sod volume COMMIS for each channel. Inputs are provided for turntable (swum car. odge). tuner and tape Ocli or recorder. F 70 20 000 318. Output2 watts r m. a. I into. ohms. RenMATCHED STEREO LOUD Inputsphone SOmV, tuner/ox IR'V. Size I' wide. 21" high. SPEAKERS. Here'srealvaluein 4)' wide stereo speakers! techunit comes complete with 10 -foot lead and phono plug. end look really smart. Power handling per speaker: 4 watts rms, 8 watts peak. Frequency mg': 40- 16.000 Hz. Flux density: 8,500 puss. 20 -WATT 3 -WAY Impedance: 8 ohms. Dimensions: 9" CRYSLER high, Or wide, 41' deep. Finish: A-3000 36 -WATT 'LIVING AUDIO' oiled mime SOLID STATE STEREO AMPLIFIER SPEAKER C1.60 ROC PRICE E1.50 pair. The A.3000 looks as good as it sounds, Normal PriceE10 75 Giving you a big performance this superb This high quality speak- audio amplifier has a full range of lkilities er has tie owe beih-ia an the front and neer panels. On the front - 3-w itch, all the controls you're ever likely to noel giving pee the ideal frown reeponse for REALISTIC 30 WATT STEREO plus a headphone socket. On the row - hi-fi, astralal tor weed music litoning. Its AMPLIFIER MODEL SA -500 (39.95 each. K signal inputs. speaker outputs Ind a line A superb hi-fi amplifn:r with all the fea- boautifel, hoary. oiled walavt cabinet tures you've ever wanted - for under lase for circuit protection. incerpralw two sop 00000 op Ow wits cc r woofer. end a 5" Specifications: IS watts two per channel 046,00. Saving over 010 00 on the normal midge'ge wish concentric tweeter. Power handling into 1 ohms. Frequency response 20-35.000 r nail value. Up-to-the-minute slider controls for bass and treble. Separate capacity: 25 welter r.m.s into 1 ohms. Overall fragooncy roe - Hz I±2dh)InputsMagnetic.Ceramic. volume and balance controls. Headphone socket on front panel. Pushbutton moo: 35.20,000 ht. Cabinet size: 101 x 71' x Ir. Exactly Tenor. input .controls - magnetic phony thigh/low) tuner. aria, mono. monitor. Tape, Aux. Tape Ploy. Situ right lea inaishing the mast melds decor. 315mai x 300mm int130mm. Loudness push-button control for perfect sound at low output levels. Normal price Left and right push-button on/off switches for speakers. Noose filtering (55.50 end tape monitoring facilities. Two auxiliary AC outlets. Frequency response 20- 20.000 Hz ± 1db at lull power. 15 watts rms per channel. Walnut cabinet with satin aluminium trims. Inputs: phono 2,5mV and 5mV RIAA: tuner/aux 250mV. Hum and noise: phono - 50db: tuner/aux - 65db. How's that for a specification! Item 1Size 41" wide. 3;" high, 10;" deep. CONSTRUCTORS' ..4*1111111111"111111-re OLSON RA -315 AMITM/MPX PALACE AM/RA/MPX STEREO TUNER AMPLIFIER SEA -11 IK STEREO TUNER KITS This is one el the lowest priced MIS Neer amplifiers on the This ROC Tuner is especially de- market. It the fell reap of bath AM and FM breakout signed to match the Olson AM -395 TWO TRANSISTOR frequencies. And whop yoer" switched to FM. en isdicater StereoAmplifier.In priceand lights up when a stork signal ie received - that's thb time to value. as well as it's good look- RADIO KIT switch to 'Stork' I The SSA -11 has all the ficilitios wed et.. ing design! But of course it's also pest to find an tuners costing twice as much ell deal for use with any other am I her. The RA310 costs E10 00 less than Complete with solar cell erne bass. treble, baleen Ind caning controls. Selector iwitch the norm] retail value.and yet 'tis a highly sophisticated unit, incorpo- [2.50 for tape. phene, AM. FM. . Jack socket oe frost panel lee rating the latest solid state thniques. Operation is drift free for sup - stork headphones. Erogeoncy rims, FM MIDI MHz. AM 1.50°' rem, plistation-holding capability. You can connect ths Tuner to a stereo 10 PROJECT 535-1605 kHz. F 50.10.000 Hz ± 3d5. amfier, to a rape deck ortape recorder. And offs OUISI it covers all Power corpus: 4 watts total musts power into two 8 ohm the stations in the AM and FM band . FM: 87-108 MHz, AM: 525-1605 kHz. INTEGRATED CIRCUIT KIT s . Size 1 r wide. FM Sensitivites: FM, 3pV: AM, 2500V. Stereo separation 30dB at 1kHz. image selection Build a radio, morse key, etc high, 8" deep. 60411. Size: 11A" wide, 4' high, 71" deep. 63.50 ROC 7 -WATT STEREO AMPLIFIER REALISTIC SA -1008 6.WATT CHASSIS SK .317 STEREO AMPLIFIER SOLAR ELECTRONIC KIT This exclusive jat Here'sfabulous,excitingvaluein ROC Stork PRE miniature!Thishighviably stereo 20 ways of harnessing the sun's energy Chassis is amplifier measures only 9' wide x 3" completely high x Ofdeep. And yet it has sepa- C4 SO self contannod. and rate ganged volume, balance and tone con- itcosts (225 less ROG PRICE trols. Plus :seeker in/out, mono/stereo. phono) thanthenormal re tuner and power onill slide switches. ends are oiled walnut, with match. TWO OCTAVE 02.45 tail value! The ing enamelled metal top. The front pan I is satin aluminium and walnut -brown ELECTRONIC ORGAN KIT SK -717 is a really Normal Price( on.Pries enamel. Frequency response". 50 to0.000 Hz ± 3dB. Output 3 watts r.m.s. Make your own music. per channel into 8 ohms. Inputs are 100mV for both phono and tuner. compact snit measuring only 51" wide. 11' Complete with speaker high and 111' deep. It contains its own mains *ASO power supply. and has a ganged volume control end warme SPECIAL OFFER! EAGLE LC.07 STEREO treble controls for each channel. Specification: frequency roo- MOVING -MAGNET kies. 40-17 NO Hz ± 30B: output 3 5 watts music power per TEC N/4417 HEAD- CARTRIDGE charnel into I ohms. input. phone. BOOTY: signal -le -notes ROOM RAINO Here's your opportunity save batter than 45dB. VIMn you want to listen to to own atranscription cartridge theradioallbyyourself for the price of a ceramic! le spimially de- Thomthiswillsolvethe signed to match lop quality tone SIMS, and problemSeparate volume to get We very beet from year hi-fi amplifier. andtuningcontrolwith 0 7 mil diemond stylus. Output: 7mV per key -to -see knobs Frequency range is channel. Frequency range: 2021.000 Hz. 535 to IND Mt medium wave band Channel balance ..1dB. Channel aaaaaa Maximum output is 300 mw tion21101. Compliance: t2 x10.8 cm/dyne. Mormon Price E7 15 ROC PRICE 0 ROC PRICE (H 37

OLSON AM -3111 OLSON AM372 IS -WATT STEREO AMPLIFIER n Horn's a really iced amplifier al a really dowe.tawarth price - 411 -WATT STEREO pi at AMPLIFIER nearly (7 less then tho normal retail valeal Jost look et what 1.441 3 -WAY MATCHED SPEAKERS An idol unit for your new the AM -372 will do for you - 00000 dime gimbals from ceramic tune cepwetesystem. r.c These will do justice to your amplifier - and to your or crystal cartridges. AM sad FM tumors. and tops recorders. Itismere than(10 00 pocket. et only (20.00 a pair. they are real value -for -money. Aid it give, you outputs for two sow of . headphones below the norms!retail Each cabinetisheavily lagged and teak finished. They and tape recorders Frequency response is 30 to 20.000 Hz ± petal Malting the AM -3O5 handle 16 watts rms Ill watts rats each). Each loudspeaker 3dB. Outten 1 wefts r.m.s. per channel music power into 1 ohm pfttGE ono of Britain's boss hill contains a 61"hase unit plus tweeter. Frequency range: 40 to speaker,. eerieinpvt 200M. Tunes input2001.6.Size: buys. ft tubas is signals from *senile, inceramic pickeps. 19,000 Hz. Size 14" high, 9' wide. 61' deep. 121' wide. 31' high, 71" deep. fe24.1ta . toms Ins Olean 5.310) and tape dabs. And it's sot set L'0 IR'pets for tiling awl lar koailphonoe. There aro separate bag Fieturn.of-post mail order IIM end table controls. Loft and OF I 1 volume ROC ELECTRONICS LTD service from Edgware controls. And a Iteensiss SWiSCh fee Nesting the bass and Road.Orders over 00 treble notes whoa listonieg at low "Met levels. FrogiNecvN. JORY Esq. 193 EDGWARE RD, LONDON, W2 JET. 01-723 6211 post free (UK only) : 2020.000 Hz ± Idl. (Meet: 20 welts r.m.s. per channel CALLERS WELCOME 9-6 MON. TO SAT. Add 25p for p Ap Nto I ohm. Inputs: magmitie shuns 3011 RIAA. crystal phone 100011. Buy it withyour to orders under £10. tape 116.6: sweet 100mV. Size 1 IA' wide. 0 -high. 11' deep. Theassn AT87 TOTTENHAM COURT RD. LONDON W1 HP terms ',deification o well - mounds wen bettor! TEL: 01-580 3739 OPEN 9-6 MON.-FRI. SAT. 9-1 available for callers

PracticalElectronics March1973 263 PRACTICAL ELECTRONICS "SCORPIO" ELECTRONIC PSYCHODELIC LIGHTING THE TRIFFIDS ARE COMING ! IGNITION SYSTEM UNIT Mk. 3 Build this really high quality A.M. receiver * SIMPLE TO BUILD I * LOW COST/ * NO ALItNMEN7 * NO DRIFT its Printed circuit, fibre glasl,roller -tinned, drilled wit This Capacitor -Discharge Electronic Ignition system was described in the component place er) 60p November and December issues of Practical Electronics.Itissuitable ZN414 I.C.--E1-20 nc. post far incorporating in any I 2V ignition This unit represents a natural pro- system in cars, boats, go-karts, etc., gressionfromourphenomenally of either pos, or neg. earth and up to successful Mk. I and 2 Units. As sixcylinders. Theoriginalcoil, before the drive voltage is derived PKm LEMENT plugs,points and contact -breaker directly from the amplifier output

capacitor fittedin the vehicle are or across the speakers.The unit The Trees Barker Lane used. No extra orspecial com- converts the audio frequency sig- ponents are required. nalsinto a three -colouredlight Helps to promote easier starting display; the colour depending on MELLOR BLACKBURN LANCASHIRE (even under sub -zero conditions), the frequency of the signal and the improved acceleration, better high- intensity on the loudness of the speed performance, quicker engine audio source. warm-up and improved fuel The unit is constructed on profes- economy. Eliminates excessive con- sional fibre -glass printed -circuit tact -breaker point burning and the board material and uses latest full - need to adjust point and spark -plug wave triac circuitry. Thereisa gaps with precision. master -level control, together with Construction of the unit can easily independent sensitivity controls for be completedinan evening and each channel. The original minimum 7Segment LEDs installation should take no longer ambient lightlevelcontrols have thanhalf an hour.A complete been redesigned permittingtheir complement of components is useas faders;allowing dimming These are full spec. devices from a famous manufacturer.The display suppliedwitheachkittogether from max. to zero at the turn of a size is just overinch giving readability at about 12 feet distance. The with ready -drilled roller -tinned knob. R.F.I.suppressionis now display is cast in clear epoxy resin and mounted in a 14 pin DIL package. professional quality fibre -glass incorporated as standard as well as printed -circuit board, custom - provision for D.J. " Pulse -Flash " fully compatible with all good quality sockets and VERO.The uniti s wound transformer and fully - controls.The choice of two inputs driven between a 7447 and the 5 volt line. machined die-cast case. All com- enables operation from both high Prices: I off [MO, 4 off C2.50, 6 off L235.Quantities above 8 L2.15 ponentsareavailableseparately. and low power amplifiers. Max. each.In all cases please add 12p P. & P. Casesize7fin i tin. power I -5kW perchannel at approx. 240V a.c. Complete assembly and wiring Complete assembly built and tested.

manual 1.5p, refundable on purchase Size 9in 7in 3in. Price [25 of kit. Price: L10.50 plus 50p P. & P. carr. paid. MEDD DABAR ELECTRONIC PRODUCTS ELECTRONICS 98a Lichfield Street, Walsall. Staffs. WSI I UZ IBI BURNS ROAD, HEMEL HEMPSTEAD, HERTS. TELEPHONE: WALSALL 34365 TELEGRAMS: DABELEC Walsall Staffs. You may telephone your order and pay by Access. 0442 62757

HOW TO MAKE THE IT'S FREEin `DIGITRONIC' SOLID-STATE DIGITAL CLOCK USING ELECTRONIC COMPONENTS CATALOGUE PHONE NOW FOR YOUR COPY 037-42 79033 JUST 30 BITS:NoT EAsity or write to:d" ------N Full instructions in this month's issue for MAPLIN ELECTRONIC SUPPLIES versions with either four or six figures P.O. BOX 3, RAYLEIGH, ESSEX PLUS A No s.a.e. needed! HERE ARE JUST A FEW OF THE FREE 6"X5" TRANSFER THOUSANDS OF LOW-PRICED LOOK ITEMS IN THE CATALOOIJE. EVERYTHINGGUARANTEED BRANDNEWMARKED BY MANUFACTURER SHEET OF LABELS FOR High -gain low -noiseq q Until further notice silicon NPN 1 pi PRICE REDUCED AUDIO EQUIPMENT BC 109C "I 8 PIN DIL OP a P 115 -Watt Easy to apply and ideal for an impressively Power Transistor 49p a. professional finish. 2N 3055 And many other constructional features, including This very popular SPECIAL IC.fororgan directions for making an electronic maze that FET builders, 7 stage frequency will keep everyone amused for hours. 24p ividerin1, 2N 3819 14 pin TTL Its cost? Around £2. - ackage £2.63orspecial Versatile Unijunct rice for pack of 12, £2.5. ALL IN THE MARCH ISSUE ON SALE NOW 20p TIS 43 (5543) I'.28 ,Z,Z7 yol ausrk cusa tat% sgl, fei a data sheet Postage and packing FREE In UK. But we have to ask you to send a 10p handling charge with order under sop. PRACTICAL WIRELESS

264 PracticalElectronics March 1973 rj.

C.W.O. PLEASE. P PACKING YATES ELECTRONICS PLEASE ADD 10p ORDERS UNDER t2. (FLITWICK) LTD. Catalogue which ains data sheets for most of the ELSTOW STORAGE DEPOT components 1 tedwillbe sentfreeonrequest. K EMPSTON HARDWICK 10p stamp appreciated. BEDFORD OPEN ALL DAY SATURDAYS

RESISTORS MULLARD POLYESTER CAPACITORS C296 SERIES fW Iskra high stability carbon film-very low noise-capless construction.400V: 0001µF, 00015µF, 00022µF, 0 0033pF, 00047µF, 2Ip.00068µF, 0.01µF, bodysize7.5 x 25mm 0015µF, 0022µF, 0033µF, 3p.0 047AF, 0068µF, 0 1pF, 4p. 0.15µF, 6p. 022µF, 7fp. INVMullardCR25 carbonfilm-Verysmall 033µF, Ilp. 047µF, 13p. 1W 2% ELECTROSIL TR5 160V. 0 OlpF, 0 015AF, 0.022µF, 0033µF, 0047µF, 0068µF, 3p. 0' 1pF 34p. 015µF 44p. Power Values Price 022µF, Sp. 0 33AF, 6p. 0 47pF, 7Ip. O'684, I Ip.I OpF113p. watts Tolerance Range available 1-99 100+ MULLARD POLYESTER CAPACITORS C280 SERIES 6.41 4.70-2.2M111 E24 Ip 0.11p I 514 250VP.C.mounting:0 01AF, 0015µF, 0022µF, 3p. 0.033µF, 0047µF, 0068µF, 10% 33M0 -10M111 E12 Ip 0.8p f 35p. 0 1pF, 4p. 0.15µF, 0.22µF, 5p. 0'33µF, 6Ip. 0 47pF, 81p. 0 681,F,I 1p. 1 OpF, 13p. 10(3-1M11 E24 35p 3p 1 5µF, 20p. 2 2AF, 24p. * 117):, 10- 3.912 E12 Ip 0.13p 5./. 470-IMO El2 Ip 0.8p 1S 4 o 10-100 Ell 6p 5.5p MYLAR ALM CAPACITORS 100V 1 CERAMIC DISC CAPACITORS Quantity price applies for any selection.Ignore fractions on total order. 0001µF, 0.002µF. 0005µF, 0 OlpF, 002µF, 100pF tol 0,000pF, 2p each. 21p.004µF, 0'05µf, 0068µF, 0 1pF, 3Ip. DEVELOPMENT PACK 0.5 watt 5% Iskra resistors 5 off each value 47 ato IMO. ELECTROLYTIC CAPACITORS-MULLARD 015/6/7 RANGE REPLACES 0426, E12 pack 325 resistors L2.40. E24 pack 650 resistors L4.70. C457 RANGES. (pF,v) 10:63. I-5/63. 2-2163, 3 3,163, 4 7 63, 6 8,40, 10/25. 1063. 15/16. 15/40,15/63, 22/10, 22;25.22/63, 33/6.3, 33,140, 47/4, 47/10, 47/25, 47 H0, 47 63, 68/6.3, 68/16, 100/4, POTENTIOMETERS 100/10. 100125, 100,40, 15016.3. 150 16, 150,25, 220,4. 220,10. 220116, 330,4, 330/10, Carbon track 5k0 to 2MO, log or linear (log ,W, lin 4W). 470/63, 5p each.68163, 150/40, 220,25, 330,16, 470,10, 680.63, 1.000/4, 9p. 100/63, Single, lip. Dual gang (stereo), 40p.Single D.P. switch 24p. 150/63, 220/40, 470/25, 680/16.1,000'10,1,500/63,12p. 220/63.470/40,680/25, 1,000/16.1,500,10, 2,200/6 3,15p. 330/63. 680'40,1,000/25,1,500/16,2,200/10, SKELETON PRESET POTENTIOMETERS 3,300,6.3, 4,700/4, 18P Linear:100, 250, 5000 and decades to 5M0.Horizontal or vertical P.0SOLID TANTALUM BEAD CAPACITORS 12p mounting (0.1 matrix). 0. 1pF 35V 2 2µF 35V 220F I6V Sub -miniature 0.IW, Sp each.Miniature 025W, 6p each. 022AF 35V 4.7pF35V 33pF 10V 0.47µF 35V 6.8pF 25V 47pF6.3V TRANSISTORS OpF 35V 10pF 25V 1000F 3V AC107 Sp AF I25 20p BD13275p 0C28 50p 2N3702 AC 126 2p AF I 26 20p BD13375p 0C35 50p 2N3703 2pELECTROLYTIC CAPACITORS Miniature P.C. mounting Sp each. AC 127 2pI AF I 27 20p BF I15 15p 0C42 Ilp 2N3704 3p1(µF,1V):10,112, 50/12, 100/12, 200/12, 5125, 10/25, 25/25, 100/25. 1"ACI28 2 AF 1 39 BFI73 20p 0C44 12p 2N37052p ACI31 2 AFI 78 11, BFI77 28p 0C45 tip 2N3706 Ip VEROBOARD JACK PLUGS AND SOCKETS ACI32 2 AFI 80 40p BFI78 32.p OC70 11pj2N37072p 0 15 18p 25mrn insulated 8p Op 0I *5.649MeTred AC 176 2 AF181 40 BF179 32p 0071 12p 2N3708 24 22p 16p 12p 3.5mm insulated 8p 32p 13' Ip Stan and insulated ACI8722p BC107 9 BFI80 0072 122N3709 2+ 5 24p 24p 35p 3.5mm screened 13p 32p 12pj 2N3710 Ip Stereo screened AC 188 22p BCI08 9p BF181 0081 3/ 24p 24p Standard socket 15p 2.5mrn socket 8p AD140 BC109 9p BFI94 15p 0082D 12p 2N37I1 Ip 1131x5 lip 27p 18p 3.5min socket ep ISP 2N4062 Stereo socket ADI49 45Sflp BCI47 13p BF195 2N2904 20p 2p x25 75p 57fp 15p 40360 35p ADI6/ 33 BCI48 I3p BF197 2N2926R 9p 17> 31- 100p 78p D.I.N. PLUGS AND SOCKETS AD 16236 BC149 I3p BF200 32 40361 35p 2N29260 9p 17 v 5 (plain) - 82p 2 pin, 3 pin, 5 pin 180', 5 pin 240', 6 pin AF 14 20 BCI57 14p BFY50 20p 40362 40p 17x 31 (Plain) 60p Plug 12p.Socket 81.. AF 15 20 2N2926Y 9p - BCI58 14p BFY51 20pw2N2926G 40408 40p 17x 24 (plain) - 42p 4 way screened cable, 15p metre. AF 16 20 2} 5 (plain) 12p 6 way screened cable 22p/metre. AF 17 20p BCI59 14p BFY52 20p 10 ZTX302 15p - 2N3054 58p ZTX500 15p 24 3} (plain) - Ilp AF 17 38p BCI8722p BUMS 225p Pin insertion tool 52p 52p AF 2422p BDI3175p 0C26 45p 2N3055 60p ZTX502 20pSpot face cutter42p 42p BATTERY ELIMINATOR t150 Pkt. 50 pins 20p 20p 9V mains power supply.Same size as PP9 battery. ZENER DIODES IRE WOUND POTS, 3W, 10,25, 400mW 5% 3.3V to 30V, 12p. w 500 and decades to 100k O, 35p. LARGE (CAN) ELECTROLYTICS 1600pF 64V74p 2500µF64V 80p 4500AF 16V 50p DIODES 25001,F40V 74p 2800pF 100VL2.60 4500AF25V1168 RECTIFIER SIGNAL 25001F50V58p 3200AF 16V 50p 5000AF 50VL1.10 BY127 1250V IA 12p 0A85 7p BZVIO 800V 6A 25p 0A90 Sp HIGH VOLTAGE TUBULAR CAPACITORS -1,000 VOLT BZYI3 200V 6A 20p 0A91 Sp 001µF 10p 0047µF 13p 022µF 2.0p IN4001 50V IA 7p 0A202 7p 0.022AF 12p 0 IxtF I3p 047µF 22p IN4004 400V IA 1N4148 Sp 1N4007 I 000V IA 10p BAI 14 Sp POLYSTYRENE CAPACITORS 160V 24% 10pF to I,000pF E12 Series Values 4p each. THERMISTORS BRUSHED ALUMINIUM PANELS L2 I2inr6in =lSp; I2in 2Iin =10p; 9in 2in =7pVA 10555 15p SMOKE AND COMBUSTIBLE GAS DETECTOR-GDI VA1066S 15p The GDI is the worlds first semiconductor that can convert a concentration of gas SLIDER POTENTIOMETERS VAI077 or smoke into an electrical signal.The sensor decreases its electrical resistance when R53 Illetaa.S111.5A it absorbs deoxidizing or combustible gases such as hydrogen, carbon monoxide, 86mm x 9mm x16mm, length of track 59mm. propane, alcohol, North Sea gas, as well as carbon -dust containing air or SINGLE 10K, 25K, 100K log. or lin. 40p. eth e DUAL GANG, 10K + 10K etc. log. or lin. 60p. COMPACT smoke.This decrease is usually large enough to be utilized without amplification. KNOB FOR ABOVE 12p. CASSETTES-IN Full details and circuits are supplied with each detector. FRONT PANEL 6Sp. PLASTIC LIBRARYPRINTED BOARD MARKER 97p 18 Gauge panel I2in x 4in with slots cut for useBOX Draw the planned circuit onto a copper laminate board with the P.C. Pen, allow to with slider pots. Grey or matt black finish com-C90 6Sp dry, and immerse the board in the etchant.On removal the circuit remains in high plete with fixings for 4 pots. C120 85p relief. LARGE RANGE ITT/TEXAS ICs NOW IN STOCK PRICES ARE CALCULATED ON TOTAL NUMBER ORDERED REGARDLESS OF MIX 85 75 65 1-11 12-24 25-99 100 + 7447 175 170 165 160 74118 100 35 30 p 175 170 165 160 74121 43 38 p p p 7448 160 130 7400 4 14 7450 20 8 16 14 74124 210 180 20 ''' 18 90 85 100 f 7401 113 6 14 7451 20 8 16 14 74141 95 145 140 135 7402 1111 - 6 14 7452 20 8 16 14 74145 150 '''' 18 260 210 7403 20 18 6 14 7453 20 a 16 14 74150 330 285 95 90 85 7404 10 18 6 14 7454 20 8 16 14 74151 110 10 100 7405 20 18 6 14 7460 20 8 16 14 74153 120 IS 80 170 56 37 7470 38 32 17 23 74154 200 90 7406 48 30 00 85 37 7472 34 30 27 21 74155 150 15 7407 56 48 30 00 7408 36 20 20 7473 40 37 30 27 74156 130 20 80 28 10 90 7409 36 28 20 20 7474 40 35 30 25 74159 130 20 35 20 100 7410 20 18 16 14 7475 60 56 52 SO 74180 155 85 80 175 7411 23 21 20 20 40 36 32 30 74190 195 7476 80 175 7412 36 32 28 24 7480 80 75 70 65 74191 195 85 34 i 28 7481 115 120 115 110 74192 200 80 65 ISO 7413 32 22 ISO 7416 45 38 32 32 7482 87 75 70 65 74193 200 80 65 65 150 7420 20 18 16 14 7483 100 95 90 85 74196 200 80 160 50 45 140 7421 36 32 28 13 7484 110 106 104 100 74197 7422 48 44 38 35 7485 250 / 245 240 235 7426 32 29 25 20 7486 45 J 66 35 30 LINEAR ICs 7427 42 38 36 34 7490 75 70 65 55 40 90 80 75 709 14 pin DIL 32 7428 50 45 32 7491A 100 34 7430 20 18 16 14 7492 75 70 65 90 741 8 pin DIL 80 70 65 SS 741 14 pin DIL 28p 7432 40 36 32 25 7493 14 pin DIL 90p 7440 20 18 16 14 7494 85 80 75 70 723 80 75 70 747 14 pin DIL SOp 7441A 80 76 70 66 7495 85 34p 80 70 7496 100 95 90 85 748 8 pin DIL 7442 76 66 14 pin and 16 pin 16p 7443 100 96 94 90 74100 250 245 240 235 DIL socket,

PracticalElectronics March 1973 265 24 WOODHILL MINITRON DIGITAL INDICATOR Reads 0 9 and decimals TRANNIE HARLOW, ESSEXTYPE 3015F (Data Sheet on request) Add 5p 1'. 6 P. Price list S.A.E. TIL 200 LIGHT EMITTING DIOD (formerly C. R. HADLEY) Made by TEXAS INST. (Red) 35P HARLOW 37739 No calk. please. ONLY £1 .50 VEROBOARD All our stocks are brand new with money back refund 0.13 0.1 BD116 79p0C44 lipTIP33A 95p2/43711 109 Matrix Matrix TRANSISTORS BDI21 DC43 TIP34A 21.8040251 41)p 16 DIL Socket 8052:in X lip 211P 60p lip Sun x 3In 25p 40107 16pAL102 59pBD130 46p0071* lip2E697 18p40636 55P Driven by 7447 980 25P AC126 '11P.AL103 490BD131 0072 2N1171 240 31 in x 31in Sip Sip 59p 12p 31In X 3in 30p Sip AC1'27 t lipAU103 850BF194 lip0081 lip2N1304 261) 01.76 ..AU111 Vero Pins (Bag of 36) 200 95pBFY50) 1500C8ID 13p2N1303 Sip SUPER LOW Vero Cotter 45p C176 BC107 Op/31,1231rap0083 20p2N2646 -47p PRICED LINEAR I.C'S Pin insertion Tools (.1 and -15 matrix) AC141K 20p BC108 Op 2N2926 41111011DIODES BSY93A lip00170 24p at 66p. AC142K 20p BC109 Op11E0402 18p0C200 25p2N3033 SopIN4001 4p301ATo99 49p ADI4 401) BC134 OPME0404-14p00201 25p2E3053 .4911 IN4002 e4p301ADIL 45p yAD130 44p BC168 OpME4401 101i0C23 26p2N3702 lip1N4003 Op 709CTo99 28p SLIDE POTENTIOMETERS BC169 1p)1E4102 1200e28 30p2N3703 lipIN4004 7p 709CDIL 30p D62 '',C.°9BC1821. 8pME6002 14p0C29 88p2N3704 12p0A9 723CTo99 87p 58mm, TRACK F114 15p BC183L SpME6101 14p0C35 26p2N3705 lip 0A910 op0A2110 723CDIL 90P SINGLE GANGED, LOG or LIN F.,.,_.115 lip"BC1841. 13t)ME6102 lip0C36 38p2N3706 10p 10p 741CTo99 gip lk to 1M.40p each. AF116 -15p 11(2212L 13pMP8111 32pTIP29A 48p2E3707 10p0A202 Sp 741CDIL $4p TWIN GANGED, LOG N AF117 lb 111`214L OpMP8311 84pTIP30A Sip 2N3708 Op 1844 10p 741COp in D1L p MP8313 46pTIP31A Sip 2N3709 10pIN4149 4p 747CDIL OP CAPACITORS 0C41 13pTIP32A 89p2143710 10pWO2 32p 748CTo99 38P MULLARD POLYESTER CAPACITORS C280.SERIES VOLUME CONTROLS 230V P.C. mounting: 0.01/2F, 0.0 3,0%0 22µF,39.0 -033µF,0 047µF, 0068µF,8fp.0.1µF, 4p.Potentiometer Pack of 10 0.13/1F, 0,22µF, 6y. 0.330% 8}D. 047µF, 8}1).068µF, lip. I -0/2F, 18p. 1-5p.F,200.22µF, 241p. Carbon track 300 ft to 2.2M CI BC169 5011 Log or Linear (unmarked) but tested MULLARD POLYESTER CAPACITORS C296 SERIES Single lip.Dual gang (stereo) 40). 1, Pack of 10 Single type with D.P. switch lip extra. BC108 50p 400V: 0.001µF, 00015µF, 0.0022µF, 0.0033µF, 0.0047µF, 21p. 00068µF, 0.01µF, 0.015AF. 22,12646 0.022µF, 0.033µF, Sp; 0.047µF, 0-068AF, 0.10,, 4p. 0.15µF, Op. 0.22µF, 75p. 0.33µF, lip.RESISTORS BC107 50P 047µF, 18p. (unmarked) (Plastic can) 1W 3% carbon 1p each 30p each 160y: 0-04.21,, 0.013µF, 0.22µE, 0033µF, 0.047µE, 0068µF, Sp. 0.1µF 8bp. 015µF, 44p.1W 10% carbon 1p each 4D161, AD162 0-22µF, 5p. 033/1F, Op. 0470F, 71p. 068µF, 11p. 1.0nF, 18p. range2711to 10 MO type TR3 AC127 & AC128 M/P triple rated H.:, tin oxide x 2% 1-9 9 64p ELECTROLYTIC CAPACITORS-MULLARD C426 SERIES 6p each range 1013 10 1 MO O. 3p sac plus 48p rttF/V) 10/2.3, 20/25, 80/23, 160/25, 320/2.5, 300/2.3, 8/4, 32/4, 64/4, 123/4, 230/4, 400/4, 10 plus lip100 6 4/6 4, 23/64, 30/64, 100/6.4, 200/6-4, 320/6.4, 4/10, 18/10, 32/10, 64/10, 123/10, 200/10,SLIDE SWITCH plus 9P BC 7-BC108 2.5/16, 10/16, 20/16, 40/16, 80/16, 125/16, 16/23, 6.4/25, 12.3/25, 23/23, 30/23, 80/25, 1/40,SPOT 10p each.D.P.D.T. 120 each C109 4/40, 8/40, 16/40, 32/40, 50/40, 064/64, 2.3/64, 5/64, 10/64, 20/134, 32/64. MINIATURE NEON LAMPS Pack of 10 1-9 Op 240V or 110V 1-4 lip, 5 plus 41p each 2N2926G 40p0-99 d 7p MULLARD C437 SERIES unbranded but 00 plus Op 100/40, 160/25, 250/16, 400/10, 840/64, 800/4, 1,000/25, 9p. 100/64, 160/40, 230/23, 400/16, CARBON SKELETON teed PRE-SETS C 11321.:3-4-212-4 640/10, 1,230/4, 1,000/6-4, 1,600/25, lip. 160/64, 250/40, 400/2.3, 640/16, 2,000/4, 1,000/10, dr (-9 SP 1,600/6.4, 2,300/2 3, 15p. 250/64, 400/40, 640/25, 3,200/4, 1,000/16, 1,600/10, 2,300/64Small high quality, type PR, 1 Meer mil Unmarked but fully10 plus 7p 4,000/2-5, 18p. 1000, 2200, 4700, IK, 21(2, 4Ki tested 10K, 22K, 47K, 100K, 220K, 4711C, 1M 2N 3033 Pack of 10 Miniature Fixed Ceramic Plate 8p each. 2M2, 4M7, Vertical orhoe iontat 9 30p Plastic BC109 Preferred values from 1.8pf to 10,000pf. mounting,Op h. plus SOP 50p 4

PRINTEDCIRCUITKIT BUILD50 INTERESTINGPROJECTSon a PRINTED CIRCUIT CHASSIS with PARTSand TRANSISTORSfrom your SPARESBOX CONTENTS:(1) 2 Copper LaminateBoards 4tin x 2 j in.(2) 1 Board for Match. box Radio.(3) 1 Board for WristwatchRadio, etc.(4) Resist.(5) Resist Solvent. (6) Etchant.(7)Cleanser/Degreaser. (8)18-pace Booklet Printed Circuits for Amateurs. T ELECTRON . (9) 2MiniatureRadio Dials 8W/MW/LW.Also free with each kit:(10) Essential DesignData,Circuits, Chassis Plana, etc.for 60 TRANSISTORISED PROJECTS. Now available from one companyare complete kits for A verycomprehensiveselection of circuitsto suit everyone's requirements and constructionalability. Many recently developedvery efficient designs published for many of the articles published inthe Electronics, Radio the firsttime,including 10 new circuits. and TV Journals. Examples of our rangeare: . -.-- EXPERIMENTER'S SCORPIO IGNITION SYSTEMS(P.E. Nov. 1971) ..... 4.: PRINTED CIRCUIT KIT £9.50.This kit includes all the partsfor the assembly of i , I thispopular andreliable system.The hardware and __v 60p instruction data are included. '.,.$,t, VIP" , Postage&Pack. 10p (UK) s tithi, ELECTRONIC PIANO (P.E. Sept.1972). We can 1 1)1111) beim Commonwealth: supply the various sections for thisarticle in kit form. II _ SURFACEMAIL 15p Power supply, price E6.60. Preampand Tremolo E320.

tFIP 1 (--i' oFtle ...... AIR MAIL60p Main Amplifier (less speakers) E3.30.13 Pitch boards E39.50 ....lice Australia, NewZealand, (less inductors). liP)__.., =

South Africa, Canada DRILL SPEED CONTROLLER(E.E. Aug. 1972). Kit alCrystal Set with biased Detector. (2) Crystal Set with voltage.quadrupler detector. consists of resistors, rectifiers, thyristorand tag board as (3)Crystal Set with Dynamic Loudspeaker. (4) Crystal Tuner with Audio Amplifier. specified in the article, price E1.05.Kit with M.K. box, (5) Carrier Power Conversion Receiver.(6) SplitLoad Neutralised Double Reflex. (7) Matchbox or Photocell Radio.(8) "TRI-FLEXON" Triple Reflex with self- plate and switch, price E2.05. adjusting regeneration (Patent Pending).(9) Solar Battery Loudspeaker Radio. parts including circuit The smallest 3 designs yet offered to the Home Constructor anywhere in the World. LIGHT DIMMER. Kit contains all 3 Subminiature Radio Receivers based on the "Trlflexon" circuit.Let us know and construction data, 480 watts,fully suppressed, price it you know of a smaller design published anywhere. (10) Postage Stamp Radio. E210. Size only 1432in x 0.95in x 226in. (11) Wristwatch Radio 1-15in x 0.80in x 255in. (12) Ring Radio 0.701n x 0,70in 8 0251n. (13) Bacteria -powered Radio. Runs on sugar or We shall also be offering kits formost articles published bread. (14) Radio Control Tone), Receiver. (15) Translator P/P Amplifier. (16) Inter- magazines and in the P.E. and other popular electronics corn. (17) 1,alve Amplifier. (18) Reliable Burglar Alarm. (19) Light -Seeking Animal, Guided Missile. (20) Perpetual Motion Machine. (211 Metal Detector. (22) Transistor will be pleased to quote prices. Tester. (23) Human Body Radiation Detector. (24) Man/Woman Discriminator. All kits sent Post FREE. (25)Signal Injector.(26) Pocket Transceiver (Licence required).(27) Constant Volume intercom. (28) Remote Control of Models by Induction. (29) Inductive -Loop Send for details of all other kits available(please enclose Transmitter. (90) Pocket Triple Reflex Radio. (31) Wristwatch Transmitter/Wire-less Microphone.(32) Rain Alarm.(33) Ultrasonic Switch/Alarm.(94) Stereo Pre- S.A.E.). 0 amplifier.tpoLs 5.1QualityStereoPush-Pullsmiutmp(rilik(.3t Telephone eam TV Sound gBrownie Transmitter. (40) Tbyristor Drill Speed Controller. Plus 10 Photoelectric ELECTROKIT ircuits, Simple Alarms, Long Range Alarms, Projector Modulators, etc. 12 Lauderdale Road,London, W.9 YORK ELECTRICS, Mail Order Dept. Telephone 01-2860011 335 BATTERSEA PARK ROAD, LONDON, S.W.11 Send a S.A.E. for full details and a brief description of all kits and Projecte. Mon. -Fri. 9.30-5.30 Thurs.9.30-6.30

266 Practical Electronics March 1973 4 -SPEED RECORD PLAYER BARGAINS HARVERSONIC SUPER SOUND SUPERSOUND 13 HI -F1 Mains models.All brand new in maker's packing. LATENT B.B.E. C109/0129 4 -SPEED AUTOCHANGER. MONO AMPLIFIER With latest mono compatible cartridge 26.97. Carr. 50p. 10 10 STEREO AMPLIFIER KIT superb solidstate With stereo cartridge 5797. Carr. 50p. audioA :siri:tripll Garrard INNS Mk. DI with heavy precision machined die new component. cast turntable. 91096. Carr. 50p. throughout.5 silicon transistor. plum 2 SPECIAL BARGAIN OFFER! power output Mamie - PRECISION ENGINEERED PLINTHS tore In push-pull. Full Beautifully constructed in heavy gauge "Colorcoat" wave rectification. Waggle coated steel.Resonance tree.Designed to take Output approx. 13W Garrard 1025. 2000, 2025TC, 2500, 3000, 3500, 5100, r.m.s.Into 8 ohm. SP25 II and III, SLO2B, AT60, etc., or B.S.R. C109, Frequency response C129, A21, etc.Black leatherette finish.Sim 125in x 12Hz-30KHz ± 3db. 141in x 35in high (approx. lin high, Including rigid NEW FURTHER IMPROVED MODELV IT li Fully integrated pre- smoked acrylic cover). HIGHER OUTPUT AND INCORPORATING amplifierstagewith P. & P. 35p. NOW ONLY £4.50 HIGH QUALITY READY DRILLED FIBRE separate Volume, Bass boost and Treble cut controls. GLASS PRINTED CIRCUIT BOARD WITH Suitable for 8-15 ohm speakers.Input for ceramic or LATEST ACOS GP91/1SC Mono Compatible Cartridge with COMPONENT IDENTIFICATION CLEARLY crystalcartridge.Sensitivity approx. 40mV forfull 110 stylus for LP/EP/78.Universal mounting bracket. MARKED FOR EVEN EASIERCON- output.Supplied ready built and tested, with knobs, 11-60. P. & P. 80. STRUCTION escutcheon panel, input and output plugs.Overall size SONOTONE (MARC COMPATIBLE STEREO CARTRIDGE 3in high x Sin wide x 71in deep.A.C. 200/250V. T/O stylus. Diamond Stereo LP and Sapphire 78. ONLY A really first-class Hi-FI Stereo Amplifier Kit.Uses P.P. 8260. P. & P. 10p.Also available fitted with twin 14 transistor. including Silicon Transistors in the first PRICE £10.50 Diamond 71/0 stylus for Stereo LP. £3.P. & P. 10p. five stages on each channel resulting in even lower noise LATEST ROSETTE 110 Stereo Compatible Cartridge for level with improved sensitivity.Integrated pre -amp EP/LP/Stereo/78. 111.63. P. & P. 1.0p. with Base, Treble and two Volume Controls. Suitable for LATEST ROSETTE T/O Mono Compatible Cartridge for use with Ceramic or Crystal cartridges.(Very simple DE LUXE STEREO AMPLIFIER EP/LP/78 mono or stereo records on mono equipment. tomodifytosuitmagneticcartridge -instructions A .c. mains S1-60.P. & P. 10p. included). Output stage for any speakers from 5 to 16 200-240 volts. ohms.Compact design, all puts supplied Including Using heavy QUALITY RECORD PLAYER AMPLIFIER MX II drilled metal work, high quality readydrilledfibre duty fully A top-quality record player amplifier employing heavy glees printedcircuit board, smart brushed anodised Isolated duty double wound mains transformer, ECC83, EL84, aluminium front panel with matching knobs, wire, solder, mains trans- and rectifier. Separate Baas, Treble and Volume controls. nut., bolts -no extras to buy.Simple step by step former with Complete with output transformer matched for 3 ohm instructions enable any constructor to build an amplifier speaker. Size Tin. w. x 3 d. 6 h. Ready built and tested. Brief specification: Power output 14W full wave ALSO AVAILABLE to be proud of. rectification PRICE 14.95.P.& P.40p. r.m.s. per channel into 5 ohms. Frequency response ± 3dB giving ade- mounted on board with output transformer and speaker 12-30,000Hz.Sensitivity better than 80mV into 1Mn. ready to fit cabinet below.PRICE VIALP. Is P. 50p. Full power bandwidth ± 3dB 12-15,000Hz.Bass boost quate smoothing DE LUXE QUALITY PORTABLE 11/P CABINET MK II Treble cut approx. to -16dB. with negligible bum. Uncut motor board size 145 x 121n., clearance 2 in. below, approx. to ± 12dB. Valve line up x Negative feedback 18dB over main amp.Power require- 551n. above. Will take above amplifier and any B.S.R. or Overall sire -12- wide8" deep ECL86 Triode Pentodes. GARRARD changer or Single Player (except AT60 and ment. 35V at 10 amp. 1 x EZ80 asrectifier. Two dualpotentiometers are x 25 high. provided for bass and treble control, giving base and SP25).Size 18 x 15 x 8in.PRICE 1.4716.P. & P. 50p. Fully detailed 7 -page construction manual and parts lid treble boost and cut.A dual volume control Is used. free with kit or send 18p plus large S.A.E. Balance of the left and right band channels can be SPECIAL OFFER!! PRICES AMPLIFIER KIT, 51050P. & P. 15p. adjusted by means of a separate "balance" control fitted (Magnetic input components 30p extra) at the rear of the chant..Input sensitivity is approxi- HI-FI LOUDSPEAKER SYSTEM POWER PACK KIT, 53P. St P. 30p. mately 300ni/v for full peak output of 4 watts per channel Beautifully made teak finish enclosure with most CABINET, g3P. & P 30p. (8 watts mono), into 3 ohm speakers.Full negative attractive Tygan-Vynair front. Size 161 in high (Post Free if all units purchased at same time). Full after feedback In a carefully calculated circuit, allows high x 10f inwide x 55'deep.FittedwithE.M.I. Wes service.Also available ready built and tested. volume levels to be used with negligible distortion. Ceramic Magnet 13in x 8in bass unit, two H.F. 12060.PostFree. Supplied complete with knobs, charade size llin. w x 41n. x. tweeter units and crossover.Power handling 10W. Note: The above amplifieris suitable for feeding two Overall height including valves Sin.Ready built and Available 3, 8 or 15 ohm impedance. mono sources into innate (e.g. mike, radio, twin record P. & P. 45p. desks,etc.) and will then provide mixing and fading tested to a high standard.Price £8.92. Our Price 18.40Carr. 65p. facilities for medium powered Hi. Ai Discotheque use, etc CABINET AVAILABLE SEPARATELY 3 -VALVE AUDIO 64'60.Carr. 60p. AMPLIFIER HAS4 UK II NEW! POWER SUPPLY UNIT Also available in 8 ohm with EMI 13in x 8in. bass HI-FI reproduc- 200/240V A.C. Input. Four switched fully smoothed D.C. speaker with parasitic tweeter. 66 60.Carr. 65p. tion of records. A.C. Mains outputs giving 6V and 71V and 9V and 12V at 1 amp operation. Ready built on continuous (If amp intermittent). LOUDSPEAKER BARGAINS platedheavygaugemetal Fitted Insulated output terminals and pilot lamp indicator. 5in 3 ohm 81.05, P. & P. 15p. 7 x 4in 3 ohm /1.15, P.A P. chant., size 75in w. x 41n. d. Hammer finish metal case, overall size 6'< 3fx 21". 20p.10 x gin 3 or 15 ohm 2190, P. & P. 30p.E.M.I. 45in. b. Incorporates ECC83, SuitableforTransistor Radios, TapeRecorders, 8 x sin 3 ohm with high flux magnet 51112, P. 5 P. 20p. EL84. EZ80 valve.. Heavy Amplifiers, etc., etc. Ready built and tested. E.M.I. 13i x13in with high flux ceramic magnet with duty, double wound mains parasitic tweeter 3, 8, or 15 ohm 111420. P. & P. 30p. transformer and output trans. PRICE £4.50P2: P. E.M.I. 13 x 81n, 3 or 8 or 15 ohm with two inbuilt tweeters former snatched for3 ohm and crossover network 114.20. P. A. P. 30p. speaker. Separate volume control and now with improved BRAND NEW.121n 15w HID Speakers, 3 or 15 ohm. BLACK ANODISED leg. ALUMINIUM HEAT SINKS. wide range tone controls giving bass and treble lift and Current production by well-known British maker. Now Negative feedback line.Output 45 watts. Front For T03, complete with mica's and bushes.Size 21in x with Hiflux ceramic ferrobar magnet assembly 51475. cut. P. & P. 5p. panel can be detached and leads extended for remote 3in approx. 25p pair. Guitar model.: 25w Se.7C 35w 8850.P. & P. 38p each. mounting of controls. Complete with knobs, valve., etc., LIMITED NUMBER! COILED SPRING BACK TELE- wired and tested for only 94-95.P. & P. 35p. PHONE CABLE.Closed approx. 10', extends to 36'. SPECIAL OFFER! HIM "FOUR" AMPLIFIER KIT. Similar In appearance to 4 core or 0 core. 25p each. P. & P. 5p. 5 or more post free. LIMITED NUMBER OF BRAND H A34 above but employs entirely different and advanced NEW ELAC 10' TWIN CONE circuitry.Complete set of part., etc. 14-10.P. & P. 40p. SPECIAL OFFER! MAINS TRANSFORMER. 200/240V LOUDSPEAKERS. With large Overall else HARVERSON'S SUPER MONO AMPLIFIER A.C. input.35V at lf amp A.C. output. ceramic magnet and plasticised A super quality gram amplifier wing a double wound fully 21" x 25' x 3' approx.Suitable for drop through or cone surround. 8 ohm impedance. vertical mounting.90p.P. & P. 90p. isolated mains transformer, rectifier and ECL89 triode 12.75.P. & P. 25p. pentode valve as audio amplifier and power output stage. BRAND NEW MULTI -RATIO MAINS TRANSFORMERS. Impedance 3 ohms. Output approx. 3.5 watts. Volume Giving 13 alternatives.Primary: 0-210-240V.Secon- and tone controls Chassis size only Tin. wide3in. deep x darycombinations:0.5.10.15-20-25-30-35-40-60Vhalf 19.in "RA" TWIN CONE LOUDSPEAKER gin. high overall. AC mains 200/240V. Supplied absolutely wave at 1 amp pr 10-0-10, 20-0-20, 30.0.30V, at 2 amps 10 watts peak handling. 3, 8 or 15 ohm. 52-20. P. & P. 90p. Brand New, completely wired and tented with good full wave. Size 3ML v 31 InW x 3inD. Price 111.85. 36 ohm SPEAKERS 3'. ONLY 60p.P. & P. 13p. quality output transformer. P. & P. 30p. "POLY PLANAR" WAFER -TYPE, WIDE RANGE OUR ROCK BOTTOM MAINS TRANSFORMER. For transistor power supplies. ELECTRO-DYNAMIC SPEAKER BARGAIN PRICE £2.95P.38gpP. Pri. 200/240V. Sec. 9-0-9 at 500mA.116p. P. & P. 13p. Size Illin x 14 Gin x 1 jr in deep.Weight 19oz Pri. 200/240V. Sec. 12-0-12 at 1 amp. 95p. P. & P. 13p. Power handling 20W r.m.s. (40W peak).Impedance 10/14 WATT HI -F1 AMPLIFIER KIT Pd. 200/240V. Sec. 10-0-10 at 2 amp. 01.46. P. & P. 30p. 8 ohm only.Response 40Hx-20kHz.Can be mounted on ceilings, walls, doors, under tables, etc., and used with Send S.A.E. for full details.Only A stylishly finished GENERAL PURPOSE HIGH STABILITY TRAN- or without baffle. monaural amplifier 05.95 each.P. & P. 25p. with an output of SISTOR PRE -AMPLIFIER. For P.U. Tape, Mike, VYNAIR & REIM SPEAKERS & CABINET FABRICS Guitar,etc., and suitable foruse with valve or 14 watts from2 transistor equipment. 9-18V. Battery or from H.T. app. 54 in. wide. Usually £175 yd., our price 75p yd. EL84 in push-pull. line 200/300V. Frequency response 15Hz-25KHz. length. P. & P. 15p per yd. (min. 1 yd.). S.A.E. for Super reproduction Gain 26dB. Solid encapsulation size15 x 15 x fin. samples. of both music and Brand new - complete withinstruction..Price HI-FI STEREO HEADPHONES speech, with mill. P. & P. 13p. glble hum. Separate 885. Adjustable headband with comfortable fiexifoam ear- inputs for mike and muffs.Wired and fitted with standard stereoin jack gram allow records HANDBOOK OF TRANSISTOR plug.Frequency response 30-15,000Hz.Matching and announcements impedance 8-16 ohms. Easily converted for mono. PRICE to follow each other EQUIVALENTS and SUBSTITUTES 5245. P. & P. 15p. Fully shrouded section wound ou put transformer to A must for servicemen and home con- HIGH IMPEDANCE CRYSTAL STICKarms.OUR match 3-100 speaker and 2 independent volume controls, PRICE 1106. P. & P. Bp. and separate bass and treble controls are provided giving structors. Including many 1000's of British, good lilt and cut. Valve line-up 2 EL84s, ECC83, EFS° and CENTRE ZERO MINIATURE MOVING COIL METER. EZ80 rectifier. Simple instruction booklet 13p (Free with U.S.A., European and Japanese transistors. 100/5A for balance or tuning.Approx. size lin Xlin parts). All parts sold separately. ONLY 57-97. P. & P. fitip. ONLY 40p.Post 5p. x fin.Limited number 75p.P. & P 10p. Also available ready built and Meted 51007. P. & P. 60p. Open 1-5.30 Monday HARVERSON SURPLUS CO. LTD. I(P/ease write clearly) to Saturday Dept. PE, 170 High St., Merton, London, S.W.19 ZUOTNAPPIITOPir.Cs. ONGLEYS Early closing Wed. 1 p.m. P.& PEONOVERSEAS ORDERS few minutes from South Wimbledon ENQUIRIEST1.1)1M3985 I Tube Station SEND STAMPED ADDRESSED ENVELOPE WITH ALL CHARGED EXTRA.

267 PracticalElectronics March 1973 JAMES B.H. COMPONENT FACTORS LIMITED SPECIAL RESISTOR KITS (*W 5% or 4W Wu CARBON FILM) 10112 Kit: 10 of each El2 value, 10 ohms-I fl, a total of 610, 12.80 net 15111 Kit: 25 of each EI2 value, 10 ohms-IM, a total of 1,525, [6.51) net POLYESTER CAPACITORS MULLARD C280 2.50Y pF: 0.01, 0-015, 0.022, 0.033, 0.047, 3p each; 0.068, 0.1, 0.15, 4p each; 0.22, 5p; SALE OFCOT SURPLUS ELECTRONIC EQUIPMENT 0.33, 7p; 0.47, Sp; 0.68, 10p; 1.0, 13p; 1.5. 20p; 2.2, 23p. MULLARD POLYESTER CAPACITORS C296 SERIES The following items are available for immediate delivery 160V: (pF) 0.01, 0015, 0.022, 2p; 0.047, 0-068, 3p; 015, 0.22, 4p; 0.33, Sp; at very competitive prices- 0.47, 6p; 0.68, 1.0, 10p. 400V: Off) 0.001, 0.0015, 0.0022, 0.0033, 0.01, 2p; 0.015, 0.033, 3p; 0.068, 4p. SCANNING ALARM INDICATOR MINIATURE ILICTROLYTIC MULLARD C426 SERIES (Sp each) Can be used for Automatic Monitoring of All Types of Teat (JAN) 0.64/64, 1.6/25. 4/40, 8/40, 10/40, 10/64, 16/40, 20/64, 25/25, 32/10, Points (Up to 25) 40/16, 64/10, 80/16, 80/25, 100/6.4, 125/16, 200/6.4, 200/10, 320/6.4, 125/10. incorporate*. Auto and Newel Fcrlities MULLARD C437: (pF/V) 64/64, Sp; 160/25, 9P; 160/40,I IP; 640/64, 11P; Illuminated Digital Input Identification I600/64, 14p. Double Pole Gold Plated Confect. on Uni- selectors ILECTROLYTIC CAPACITORS. Tubular and large can Unite Supplied Untested Less Indicating Meter. Price 225 00 (pF/V) 2.5/50, 3p; 4/10, 10/25, 16/15. 20/25, 25/15. 25/25, 40/6, 64/10, 200/6, Carriage end Insurance (U.K. only) El 50 250/10. 4p; 10/6, 10/50, 25/50, 32/50, 50/10, 64/25. 100/25. SP; 50/50, 64/40, 250/15, 1,000/3, gp; 100/50, 250/2S, 400/10, SOO/ I 0, 500/12, 640/10. 1,000/6, DOSIMETER CHARGING UNIT TYPE MI6 Sp; 500/25, 10p; 500/50,11p; 1,000/12, 10p; 1,000/23, 2,000/12, 2,500/12,15P; 1,000/50, 3Sp; 2.000/25. 25p; 2,500/25, 30p; 2500/50, S5p; 3.000/50, 63p; PORTABLE INSTRUMENTS USED TO CHARGE QUARTZ FIBRE TYPE POCKET DOSIMETER TO ZERO. SUITABLE FOR USE WITH ALL 5,000/S0, 115p; 1,000/100. 60p; 8/350, 12p; 16/350, 17p; 32/350, 22p. STANDARD TYPES OF QUARTZ FIBRE DOSIMETERS CERAMIC PLATE CAPACITORS HAVING A MAXIMUM OUTSIDE CHARGING END 750V: (pF) 5,10, 25, 40, 70, 220, 1fp;(1.4F/V) 00047/30, P01/350, 2p; DIAMETER OF 0,8051N. TELEPHONE TYPE A C. AND 0047/30. 3p; 0. I /30, 49; 01/100, Sp; 220-10000 50V, El2 Series; 15000- GENERATOR. THE OUTPUT OF WHICH IS RECTIFIED 01:122µF 50V, E6 Series 26, each. AND CHARGES UP A RESERVOIR CAPACITOR TO A MAXI- MUM POTENTIAL OF ABOUT 360 VOLTS!) C. SUPPLIED CARBON FILM RESISTORS CW 5%, 10 ohms -2.2M, (W 5%. 22 ohms-- LESS GENERATOR HANDLES. PRICE 21 00. P. & P 20p IM. 1p each or 100 for &Sp; 1,000 for 1.4. METAL FILM RESISTORS I W 5% 22 ohms-IOM, lip each or 100 for LI. RELAYS (NATO APPROVED) VSROBOARD 0.1 0.15 IN4001 6p 2 x Sin 25p 25p IN4002 7p GEC 4 pole cio 24V 670 ohm. OEC 2 pole onicH 24V 6/0 ohm. OEC 2 pole cio ClIA9TFY 65V 5.000 ohm. STC 2 pole c,o 12V 170 ohm 2 x 3fin Up 17p 1N4003 Bp DISCO NT 3 x Sin 21Ip 30p IN 4004 9p Price each 20p. P 6 P 10p 3 x 31in 2.5p 25p IN914 6p SPECIAL BULK BUY 2 x fin 2 for 12p 12p µ1.914 lop PRICES ARE AVAILABLE 2x Son (plain) - 120 007( 12p BY QUOTATION FOR PC102 Supply voltage 220-250V cOutput voltages 2 x 3fin (plain)- 1 1p 0075 ISp LARGE PROJECTS 21 Volt. Pc at 330MA 5x nin (plain) - 20p OC83' 18p 21 Volts ec et 540MA Insertion tool54p S4p T ack cutter 40p 40p Screened wire, yd. Sp P ns, pit. 25 Sp Sp Twin screened wire, yd SP NEWMARKET ISTORS Stereo cc. wire, yd. 911 2 pin DIN Plug, 12p; Skc., Quad screened were, yd. 19p NKT361 73p NKT12329 27p 2N2222 11Ip NKT218 23p 10p. 3 pin DIN Plug, 13P; 3 core circ. mains cable White, 3 yds. 24p NKT352 25p NKT12429 270 NKT12 30p NKT221 36p Skt., 10p. 5 pin DIN Plug, Neon bulb 90V wire ended 5 for 20p NKT4013 NKT13329 NKT72 250 60P 27p NKT222 lip 180'. ISp; Skt., 12p. Tran- P skeleton pots I K -1M SP NKT420 E1 80 NKT13429 2/p NKT73 22p NKT223 26p sisterEquiv.Book, 40p. NKT450 30p NKT16229 2/p NKT121 2110 NKT224 22p Carbon pots 5K -2M log, & . NKT803 22p NKT20329 29p NKT124 Sap NKT227 26p NKT613F 2Ip NKT80111 Gip NKT125 30p NKT737 29p lin, single 151p, single with C. W.O. only.P. & P. 10p on orders below L5. N1(7874 30p NKT80113 1111p NKT126 35p NKT2311 Illp switch 2.4p, dual 42p. I Discount: L 10-10%. L20-15%. NKT877 lip NKT80125 NKT127 239 NKT249 29p NKT713 27p I3C107 8p NKT126 lap NKT261 19p Dept. P.R. 61, CHEDDINGTON ROAD, PITSTONE NKT734 24p BC1011 SP NKT129 22p NKT270 lap Near LEIGHTON BUZZARD, BEDS. LU7 9AQ NKT736 300 BCY70 lap NKT135 24p NKT271 Tel. Cheddington 668446 STD. (0296) NKT773 23p BFY51 NKT137 30p NKT272 t50 Inquiries-S.A.E. Catalogue FREE Callers please phone first. NKT0016 20p BSV95A lip NKT142 Up NKT273 1 Bp NKT3055 23p 2N507 13p NKT143 Up NKT274 top NKTE4117 27p 274706 80 NKT212 23p NKT275 21p NKT10339 23p 274914 lip NKT213 239 NKT278 lap NKT113419 17p 2N918 NKT214 21p NKT3131 70p NKT10439 29p 214630 22p 1401215 19p NKT302 /Sp NKT10519 20p 2141990 22p NKT217 Yep NKT303 70P NKT304 210 Stereo radio from S.T.C. 9-BRAND NEW

NOMINAL COIL CONTACT COIL RESISTANCE PRICE FORM your existing tuner. TYPE VOLTAGE (OHMS) EACH

250 ARO 4 CHANGEOVER1 6V d.c 52 CAUTION A complete set of parts E0 SO MAX VOLTS : 250 AGO 4 CHANGEOVER 48V d c. 2.500 03Si le tit from Jermyn to build a Stereo LAMP CURRENT: 75 ma decoder module that will con- vert your existing mono tuner CONTACT COIL SWITCHING PRICE TYPE FORM VOLTAGE ICURRENT EACH for stereo reception whilst SL7222212 3 Pole on/off 12V a.c 10A at 440V a.c. El 00 maintaining a high standard SL71122715 2 Pole CIO 220V c 10A at 440V a.c 22 87 of reproduction. The distortion is very low CONTACT COIL COIL PRICE TYPE FORM VOLTAGE RESISTANCE EACH (typically 0.3% at 560 mV SP13372 Single Pole C/0 6V d.c. 140 ohm PI M RMS composite input signal) SP13386 Single Pole 00 12V d.c 350 ohm ES 40 11301D Single Pole 00 18V d.c GI 40 with 40dB channel separa- 075 ohm tion. The stereo switching is UNISELECTOR SWITCHES O 000 000 a utomaticand there is a light 6 bank 25 way 75coil 50V cl.coperation. I 9 :T)- emitting diode which acts as Mounted on Modular Type Chases with front a stereo beacon. panel containing 20 illuminated Pueh Button O 00 0 00 0 0 Switches. Completely wired for operetion. The kit requires no coil Price 215 P &P 2055. Ca= r-rn and there are no alignment =tax rr-recv problems. Fitting. The module requires a 10-16 volt power supply which can AUTOMATIC CYCLER UNIT normally be tapped off the existing tuner. The signal input is taken The unit generates stepping pulew 150y d c I at intervals of 6 pulses per min to 120 pulses per min.-continuously variableCan be used for Automatic off before the de -emphasis circuit which in practice means discon- Stepping of one or more uniselector switches shown above. Price 212 Se necting one, or at the most, two capacitors. Any radio engineer will be P & P CO 45 able to spot these capacitors, but if you're really stuck send the cir- cuit with a SAE to us and one of our engineers will indicate the output NEWMARKET PACKAGED AUDIO AMPLIFIER point. (This i s the ful I extent of our involvement, no hardware please). PC1 15001W Audio Amplifier. Price El 00 each P & P TO 10 PC10 Magnetic replay head amplifier supply voltage 9V d c r-npedance 150 Of course, if you have a modern mono tuner with a multiplex out- Price E0 e0 each P & P CO 10 put our module simply plugs in. The outputs go via a screened twin cable to the tuner inputs of WE HAVE A LARGE RANGE OF CAPACITORS POST 0 PACKING OVER Elf-FREE. OVER your stereo amplifier. AND RESISTORS. PLEASE SEND A STAMPED El AND UNDER (2-15p LINDER CI -10p And the cost? £4.90 for the Kit with 100%tested integrated circuit. AND ADDRESSED FOOLSCAP ENVELOPE UNLESS SPECIFICALLYMENTIONED. Also available assembled and aligned, checked and ready for use FOR YOUR CATALOGUE P A P. U.K. ONLY at £6.90 (includes 12 month guarantee). Beat that! JAMES SCOTT (ELECTRONIC ENGINEERING) LIMITED To Jermyn Industries Please-rush me El Kitts), O made up Stereo decoders. CARNTYNE INDUSTRIAL ESTATE, GLASGOW G32 6A8 30 Vestry Estate I enclose cheque/postal order for £ TEL: 041-778 4206 Sevenoaks Name Kent Address {_Block Capitals Please J 268 PracticalElectronics March1973 WHARFEDALE SUPER ALL MODELS "BAKER SPEAKERS" IN STOCK Hi Fi Enclosure Manual containing 20 plans, designs. BSR LATEST SUPERS M 10" HI-FI SPEAKER crossover data and cubic tables. 42p Post Free STEREO & MONO 15 watt.4to 8 ohms. Response 20 Plays ir' 10" or r records. c/s to 12 kc/s. Ban resonance 42 e, s. Auto or Manual.A high Massive Ceramic Magnet. Deep fabric BAKER I2in. MAJOR £9 quality unit backed by BSR cone surround. Cut 'alloyframe. - 30-14,500c/s,12in.double reliability with 12 months' Weight S lb. (Value 11050.) guarantee. AC 200/250V cone, woofer and tweeter cone Sire 135 x lltin. ?MITE togetherwith a BAKER Above motor board 3 lin.below motor board 21in. £5.50 0"." ceramic magnet assembly THE FAMOUS WHARFEDALE SOUND having a ffux density of with STEREO and MONO XTALL875Poet 25p. R.C.S. STABILISED POWER PACK KITS 14,000 gauss and a total flux All parts and instructions with Zener Diode, Printed Circuit, of145,000Maxwells. Bass BSR JUNIOR Bridge Rectifiers and Double Wound Maine Transformer resonance 40 c/s.Rated 20W. input 200/240V a.c. Output voltages available 6 or 9 or 12 State 3 or8or15 ohm. Heavy duty 4 -speed motor with or 15 or 18 or 10V d.c. at 100mA or less Post free. separatepick-up armfitted PLEASE STATE VOLTAGE REQUIRED. LP/78 turnover mono£4.50 Details S.A.E. 1.1 x 1in. £2FreePoet cartridge Size 35 x Module kit, 30-17,000c,s Poet 25p R.C.S. GENERAL PURPOSE TRANSISTOR with tweeter, crossover, baffle and PRE -AMPLIFIER BRITISH MADE -.: f I 1.50 Ideal for Mike. Tape, P.O., Guitar, etc. Can be used with instructions. E.M.I.TW a EE RR A 1(117£515 Battery 9-12V or H.T. line 200-300V d.c. operation.Size: BAKER "BIG -SOUND" SPEAKERS Available separately Poet 25p. 11 x 11 x 1 in.Response 25 c/e to 25 s, 26 dB gain. 35''Group 50' Woofer 14.25Tweeter 11.90 For use with valve or transistor equipment. on,..Post 'Group 25"Group Comprising a fine example of a Woofer Full instructions supplied.Details S A E lop /a 12in. 26W ....'35W £9 SOW £20 101x65in. with a massive Ceramic 8 or 15 ohm Magnet.44os. Gauss 13.000lines. GARRARD DECCA DISCO DECK 3 or 8 or 15 ohm 3 or 8 or 15 ohm Aluminium Conecentretoimprove E1850,Post 25p TEAK HI-FI SPEAKER CABINETS.For 12in or 10in middle and top response. Also the E.M.I. Single -play Stereo/Mono Deram dia. speaker 20 x 111 x Bin, 19. Post 25p.For 13 x Bin or Tweeter 31in. square has a special light- transcription head and arm. 81n speaker 16 x 10 x Bin, 15. Post 25p. For 10 x Bin or Bin weightpaper cone and magnet flux 4 speeds.10;in.turntable. speaker 16 x 8 x Bin,£4. Post E5p. 10,000 lines.Crossover condenser and Anti -rumble filter. Bias LOUDSPEAKER CABINETWADDING 18inwide, 15p tollinstructions supplied. compensation. Laboratory CIP Per ft. Impedance Standard 8 ohms motor. Maximum Power 12 watts GOODMANS 61in. HI-FI WOOFER Useful Response ....35 to 18,000 c/s LMETAL PLINTH AND PLASTIC COVER 8 ohm. 10W. Large ceramic magnet. Base Resonance 45 cis Cutout for mint G d or H.S.R. Most will SpecialCambricconesur- SUITABLE ENCLOSURE 10 z 13 x 910. £ Poet2 play with cover in position.115 x 141 x 71in round. Frequency response MODERN DESIGN. TEAK WOOD FINISH high. Latest Design. Covered in black 30-12,000c/s. Ideal P.A. £4 leatherette. £4 50 Columns. lit -Ft Enclosure Systems, etc. SPECIAL OFFER! Poet 35p Bin Standard Cone 12W £4.50 SMITH'S CLOCKWORK 15 AMP ALSO AVAILABLE IN SOLID NATURAL MAHOGANY TIME SWITCH WAX POLISHED FINISH - AT SAME PRICE ELAC CONE TWEETER Single pole two-way. Surface mounting The moving coil diaphragm give. a good with fixing screws.Will replace All poet radiation pattern to the higher frequencies existing well switch to give light MAINS TRANSFORMERS 25p each and a .month extension of total response for return home, garage, automatic 250-0-250 BOmA 8.3V 4A £1.50 from 1,000 c(sto 18,000 c/s.Sine 31x anti -burglar lights, etc. Variable knob. Rating 10W, 3 ohm or 250-0-250 80mA 8.3V 3.5A, 6.3V 1A, or 5V 2A . £2.50 35 x tin deep. Turn on or off at full or intermediate 15 ohm models. settings.Two types available 0 to 60 minutes or 0 to 350-0-350 80mA, 6.3V 3.5A, 6.3V 1A, or 5V IA £3 £ I .90Post 10p. 6 hours. Makers last list price 14.50. Brand new and fully 300-0-300V 110mA, 8.3V 4A 0.T.; 6.3V IA 1.3-25 guaranteed.Fully insulated. MINIATURE 200V, 20mA, 0.3V 1A, 11 x 21 x tin 75p SPEAKER COVERING MATERIALS. Samples Large S.A.E. OUR PRICE 21.50.P. & P. 15p or 13 pair.Post Free. MIDGET 220V 45mA, 6.3V IA, 1/ x 25 x 21n 90p Horn Tweeters 2-16kc/c 10W 8 ohm or 15 ohm 11.95. (Plesse state type when ordering'. De Luxe Horn Tweeters 2-18kc/s, 15W, 15 ohm 13. TWO- HEATER TRANS. 8.3V 3A 60p WAY 3.000 c/s. CROSSOVERS 3 or 8 or 15 ohm 95p. GENERAL PURPOSE LOW VOLTAGE. Tapped outputs LOUDSPEAKERS P.M. 3 OHMS. 7x4in., £1.25; 61in., 11.50; WEYRAD P50 - TRANSISTOR COILS at 2A, 3, 4, 5, 6, 8, 9, 10. 12, 15, 18, 24 and 30V. 12.25 8 x bin, 11.60; 8 x 21in, 11.50; Sin, 11.75; 10 x Bin, 11.00. RA2W Ferrite Aerial . . 72p Spare Cores 3p SPECIAL OFFER: 80 ohm, 21in, 2:in; as ohm, tin, Sin, 33p Driver Tram. LFDT4 58p 1A, 6, 8, 10, 11, 16, 18, 10, 24, 30. 38, 40, 48, eav1225 Ow. P50/1AC 1A, 8, 8, 10, 12, 16, 18, 20, 14, 30, 86, 40, 48. 80V13.15 25 ohm, 21in dia., Sin dia., 6 x 4in.; ,f EACH I.F. P50/2CC 470 kcie . 38p Printed Circuit, PCA1 580 15 ohm, 311n dia, 6 x 4in, 7 x 4in, 8 x bin. TYPE Srd I.F. P60/BCC 36p J.B. Tuning Gang 85p 5A, 8, 8, 10, 11, 16, 18, 20, 24, 30, 36, 40, 48, 80V18.75 3 ohm, 1510, Erin, 311n, bin dia. 6 x 4in 8 ohms 11.50. P51/I or P51/2 36p Weyrad Booklet 10p 3A, 5, 8, 13V 11.00 RICHARD ALLAN TWIN CONE LOUDSPEAKERS Bin. P60/3V 38p OPT1 58p Ditto 5A £1.10 diameter 4W; 10in diameter 5W; 12in diameter. 6W; 3 or Mallard Ferrite Rod 8 x ;in. 20p.0 x ;in, 20p. 3A, 5, 8, 10, 13V, 5-0-5V £1.30 8 or 15 ohm models, £2.20 each. Poet 15p. VALVE OUTPUT TRANS. 25p: MIKE TRANS. 50:1 25P. Ditto 5A 11.50 5 WATT MULTI -RATIO, 3, 8 and 15 ohms 80p. VOLUME CONTROLS 80OhmCoax 4pyd. AUTO TRANSFORMERS. 115V to 230V or 230V to 115V. Long spindles.Midget Size BRITISH AERIALITE 150W 1215; 500W 01.25; 750W £10; 1000W 114. MAJOR 100 WATT 5 K. ohms to 1 Meg. LOG or AERAXIAL-AIR SPACED CHARGER TRANSFORMERS. Input 200/150V. LIN. L/S 15p.D.P. 25p. 40 yd. 1140; 80 yd. £2. for 6 or 12V, 15A, £1.50: 2A, 41.80; 9A, 22.50. ALL PURPOSE STEREO L/8 55p. D.P. 75p. FRINGE LOW LOSS I np TRANSISTOR Edge 5K.S.P. Transistor 25p. Ideal 815 and colour ."yd BATTERY CHARGERS. 11A £2; 3A £3; 4A H. FULL WAVE BRIDGE CHARGER RECTIFIERS: AMPLIFIER 8 or 12V outputs.11A 40p; 2A 55p; 4A 85p.LUCAS 4 inputsspeech and 8in. or 10in. ELAC 206500 Full wave Bridge 70V, 5A 95p. music, 4 way mixing. HI -F1 SPEAKER MAINS ISOLATING TRANSFORMER Response 10-30,000 c'1.Matches loudspeakers, 8.15 ohm. A.C. 200/250V. Poet Dual cone plasticisedroll sur- Primary 0-110-240V.Secondary 0-240V.3A. 720W. SeparateTreble andBass control.. Free round.Large ceramic magnet. Insulated terminal.. Varnish impregnated. Fully enclosed Guaranteed.DetailsS.A.E. £49 in steel case with fixing fee. Carr. 50-60,000 c/e.Base resonance EIO50, BARGAIN AM TUNER. Medium Wave. 155 c/xt 8 ohm impedance, Famous make. (Value 119)t OUR PRICE L495 Sin 10 watts, 10in 12£3.75 Can be used as 800W auto transformer. 240-110V. Transistor Superhet, Ferrite aerial. 9 volt. watts music power. BARGAIN 4 CHANNEL TRANSISTOR MONO MIXER. NEW TO ICS CAR -TYPES -- Add musical highlights and sound effects to recordings. 14p 14p50+50/350V . 1312 /350V.. 250!25V 351 8in. . E.M.I. ' /350V 14p 503/25V . 20p80+100/350V . 5SP Will mix Microphone, records, tape and tuner g3.95 SPEAKER SALE ! /450V. 14p1000/25V 35P 32+32/150V 18P with separate controls into single output. 9V. 'I. 6/450V 15p 1000/50V 47p 31+31/450V 33p STEREO VERSION OF ABOVE 15.95. With twin tweeters. 4.3.95 2/450V 20p8+8/450V 180 . 50p BARGAIN FM TUNER 88-108 Mc/s Six Transistor. 9V. And croesover.10 25/25V. 10 8+18/450V 10 350 + 50/325V watt. State 3 or 8 or 50/50V 10p 16+16/450V 25P31+32+32/350V 43p Printed Circuit. Calibrated slide dial tuning. 15 ohm.As illustrated. Poet 25p 00/25V 10p32+31/350V 25p100+50+50/350V 48p Walnut Cabinet. Size 7 x 5 x 4in. LI4.85 LOW VOLTAGE ELECTROLYTICS. With flared tweeter cone and ceramic 2, 4, 5, 8, 18, 25, 30, 50, 100, 100mF 15V 10p. BARGAIN FM TUNER as above lees cabinet £9.85 magnet. 10 watt. 500mF 12V 15p; 25V 20p; 50V 30p. Base res. 45-80 c/s. £2.25 000mF 12V 17p; 25V 35p; 50V 97p; 100V 70p. BARGAIN3 WATT AMPLIFIER. 4 Transistor£4.50 Flox 10,000 gauu. 000mF 6V 25p; 25V 412: 50V 57P. Push -Pull Ready built, with volume control State 3 or 8 or 15 ohm.Poet 25p 2500mF 50V 82p; 3000mF 25V 47p; 50V 65P and on off switch. 9 volt. 5000mF 6V 25p; 12V 42p; 25V 75p; 35V 85p; 50V 95P. £5 P"'` COAXIAL PLUG Op. PANEL SOCKETS 13p.LINE 18p TEAK CABINET 16 9' 25p CERAMIC, 1pF to 0.01mF, 4p.Silver Mica 1 to S000pF, 4p. OUTLET BOXES. SURFACE OR FLUSH 25p. PAPER 350V-0.1 4p, 0.5 13p; lmF 15p; 2mF 150V 15p. BALANCED TWIN RIBBON FEEDER 300 ohms. 5p yd BRITISH MADE STEREO 500V-0.001 to 0.05 4p; 0.1 5p; 0.25 8p; 0.47 25p. JACK SOCKET Std. open -circuit 14p, closed circuit 23p, SILVER MICA.Close tolerance 1%.2'2-500pF Sp:560- Chrome Lead -Socket 45p. Phono Plug. Op. Phono Socket 5p. MULTIPLEX DECODER 2.200pF 10p; 2,700-5,600pF 20p; 6,800pF-0.01, mid 30p each. Brand New. 7 transistor. Plus integrated circuit. Fibre -Glass JACK PLUGS Std. Chrome 15p: 3.5mm Chrome 12p.DIN TWIN GANG. "0-0" 109pF+176pF, 85p; Slow motion SOCKETS Chassis 3 -pin 10p: 6 -pin 10.DIN SOCKETS Lea printed circuit board. Size It...8/ x1. Pre -Aligned. Com- drive 365pF+385pF with 25pF+15pF, 50p: 500pF stand- plete with stereo beacon indicator. 12V d.c. operation. 400mV 3 -pin 18p: 5 -pin 15p.DIN PLUGS 3 -pin 18p; 5 -pin 25p ard 45p; single gang 500pF 75p; small 3 -gang 500pF 11430. VALVE HOLDERS, 5p; CERAMICS 82; CANS 51, Output for 100mV Input. Full instructions for any L6.50 SHORT WAVE SINGLE. 10pF, 30p, 25pF, 55p, 50pF, 55p. FM Tuner. Some technical experience essential. NEON PANEL INDICATORS 250V AC/DC. Amber 20p. E.M.I. TAPE MOTORS.120V or 240V 21ineider RESISTORS. :W. 5W, 1W. 10% 1p; 2W, Op.100 to 10M. A.C. 1.200 r.p.m. 4 pole 135mA.Spindle BLANK ALUMINIUM CHASSIS.18e.w.g. 0.187x075in. Size 3; x 21 x 21in Sx 4in 45p; 8 x 8in 53p; 10 x 7in 65p; 12 x Sin 85p; HIGH STABILITY. 5W 2% 10 ohms to 1 meg., 10p. Ditto ii.25 14 x gin 90p; 16 x Bin 90p; 12 x 3M 50p; 16 x 10in £1. S'. Preferred values 10 ohms to 10 meg., 4p. (illustrated). Post 15p. ALUMINIUM PANELS 18 s.w.g. 6 x 4in 9p; 8 x flin 15p: WIRE -WOUND RESISTORS 5watt. 10 watt,15 watt. E.M.I. GRAM. MOTORS. 120V or 240V cc. 14 x Sin 18p; 10 x 7in 19p; 12 x 5in 20p; 12 x Sin 28p; 10 ohms to 100K 10p each: 0.5 ohm to 8.1 ohms 10p. 2,400 r.p.m. pole 70mA. Spindle QCp 16 x Oln 18p; 14 x Sin 34p; 11 x 12in 40p; 16 x 10in 50p TAPE OSCILLATOR COIL Va lye type 35p. (1 in. Sise 2; x 21 x Post 15p CALLERS WELCOME HI -Fl STOCKISTS RETURN OF POST DESPATCH MINIMUM POST AND PACKING 15p CUSTOMERS FREE CAR PARK 337 WHITEHORSE ROAD, CROYDON RADIO COMPONENT SPECIALISTS Open 9.6 p.m. (Wednesdays 9-1 p.m., Saturdays 9-5 p.m.) Illustrated Colour Brochure, Radio Book and Component Lists 10p.(Export: Remit cash and extra postage.) Buses SO, 68, 159. Rail Selhurst. Tel. 01-684-1665

PracticalElectronics March 1973 269 ORGAN KITS Build your own Electronic Organ, if you want the best value for your money. Yes you really save over 50°.. and get the best and up-to-date designs. There are four models to choose from. * Portable 4 octavekeyboardwith 10 voices, 3 pitchesvibrato, at E145.29. * Console 5 octavekeyboardwith 10 voices, 3 pitches.Keyboard can besplit into solo and accompaniment.Vibrato builtinamplifier and 50 watt 12" Goodmans speaker at E199.75. * Console --2 x 4 octave keyboards and 13 note pedal boards, 29 voices,Vibrato, Delay Vibrato, Sustain Reverberation, percussion, Wah Wah, etc. at L406.00. * Console2 x 5 octave keyboards and 32 note pedal boards,32voices.Vibrato, Delay Vibrato, Sustain Reverberation, Percussion, 3 Couplers, etc. at E553.60. ALL COMPONENTS CAN BE BOUGHT SEPAR- ATELY. SEND 50p FOR LATEST CATALOGUE, WHICH INCLUDES SPECIALISED COMPONENTS, HI -FlEQUIPMENT AND ELECTRICAL HOUSE- HOLD APPLIANCES. ELVINS ELECTRONIC MUSICAL INSTRUMENTS

8 PUTNEY BRIDGE RD., LONDON =--- S.W.18 TEL. 01-870 4949 Also at 12 Brett Road, London, E.8 Business hours: 10 a.m. to 7 p.m. Monday to Saturday. Thurs- day closed.

SOUND BARGAINS

GIANT POWER Z:tiTEIiAND COMMUNICATIONS RECEIVER i WITH 3 In 1 AC/DC POWER SUPPLY SYSTEM PE TRIFFID MAINS/BATTERY pins BURNS BATTERY BOOSTER

OUR PRICE FERRANTI ZN414 +40p P. & PE1050 RADIO CHIP EI.25 Noless than3 VHF BARDS. PicksupAircraft Transmissions, PopPirates,Taxis, Ambulances,Local TO18 SOCKET 10p Radio, Continental and all BBC, VHF Stations plus Buy it with Access ascinating Public Service Transmissions we are not allowed to mention!Even TV sound in certain areas.PLUS A SPECIAL BATTERY WEATHERBAND. Frequency ranges: MW540-1600k Hz, FM88-108MHz, You may telephone EYEMED CHECK Airband 108-145 MHz, VHF 145-175 MHz, 23 semiconductors ---12 tran- ELECTRONICS INDICATORdstors,11 diodes and thermistors.Automatic frequency control.3lin your order and pay telescopic aerial. /tuns off mains a.c. 230/250V or off 4 Ull batteries, or by Access. EBBERNS ROAD, HEMEL IIEMPSTEAO, HERTS. use re -chargeable nickel alkali cell.Finished in strong leather grained case with 0442 62757 carrying handle. Approx. size 102 in x6; innin. Written guarantee.Special magnetic ear -piece for personal listening, dry batteries free. HURRY! !Amite,' quantity only from Sonic Sound.

Tuneintotheworldwiththisamazing communications receiver. A truly exceptional PRICE£28'95 unit in performance and looks-leatherette The most accurate +50p P. & P. with Stainless steel trim. Look. good any- where. Use either as a portable with standard batteries or plug it pocket size directly Into 220-240V domestic mainssupply. 14 transistors: 9 diodes;1 thermistor. Internal 8 ferrite rod antenna plus telescopic CALCULATOR WAVEBANDS aerial. Separate tone, volume and ASO WORD tuning controls with push-button MAP I TIME selectors for the Li WAVEBANDS. in the world ZOMOIAL Complete with HI -Fl earphone for personal listening. Frequency ranges: Longwave150-350 kHz. Medium353-1805 kHz. Marine 1.6-4 5 MHz. The 66 inch OTIS KING scales give Short Wave 12-24 MHz.FM/VHF 88-108 you extra accuracy. Write today MHz. Aircraft108-135 MHz. PUBLIC SERVICE BANDS 135-174 MHz. Fully for free booklet, or send L465 for guaranteed.N.B. The Ministry of Post & this invaluable spiral slide rule Telecommunications has pointed out that a licence (not generally available to the public) is required for reception of transmissions by Fire Brigade, Aircraft, Shipping, etc, on approval with money back refund if not satisfied. SONIC SOUND (Dept. PE10), 372 EDGWARE ROAD CARBIC LTD. (Dept. PE 45) LONDON, W.2. Tel. 01-723 0094 54 Dundonald Road, London SW19 3PH AUDIOLTD. Callers welcome Mon. to Sat. 9 a.m.-6 p.m. 270 PracticalElectronics March1973 FOR RAPID GARLAND EROS. LTD, SERVICE DEPTFORD BROADWAY, LONDON, SE! 40/1

TRANSFORMERS ELECTROLYTICS PLUGS all with 0-250 Volt primaries 1µF 450V 19p 1,000µF 25V 27p Car aerial I4p Miniature 29F450V 10p I ,000µF SOV 41p Co -axial 9p MM6 6V, 500mA + 6V, 500mA 4µF350V 14p 2,000µF 25V 39p D.I.N. 2 pin (speaker) 10p MM I2 I2V, 250mA t I 2V, 250mA 450V 17p 2,000µF 50V 53p D.I.N. 3 pin 13p MM20 20V. 150mA + 20V, 150mA 169F450V lap 2,500µF 25V 4Sp D.I.N. 4 pin 14p 1149 plus 13p p. & p. 25pF 25V 7p 2,500µF 50V 60p D.I.N. 5 pin, 180' 13p L.T. 259F 50V 10p 3,000µF 25V 4Sp D.I.N. 5 pin, 240' 15p LT1 6.3V, 1.5A -75p plus 18p p. & p. 32µF 450V 2.7p 5,000µF 25V 60p D.I.N. 6 pin 15p LT2 6.3V, 3A -117p plus 26p P. & P 50F 50V 10p 5,000µ 50VL1.10 Jack, 2fmm unscreened 9p LT3 12V, I.5A-87p plus 26p P. & la 100µµF 25V 10p 8-8µFF450V lip Jack, 2f mm screened 10p LT4 I 2V, 3A-41.32. plus 30p 100µF 50V I 1p 8-16µF 450V 20p Jack, 31mm unscreened Sp P. & P. 250µF 25V 149 16-16µF 450V 27p Jack, 3fmm screened 11p LTS 9-0-9V, 0.5A -75p plus 2Ip 250µF 50V 17p 16-329F 450V 63p Jack, fin unscreened 12p P. & P. 500µF 25V lap 32-32µF 450V 499 Jack, fin screened 10pSOCKETS LT6 I2 -0-12V, IA -95p plus 26p 500µF 50V 15p 50-50µF 350V 3Sp Jack, stereo. unscreened 20pCar aerial Bp F. & P. Jack, stereo, screened 31:Co -axial, surface Bp Multi -tapped Phono, plastic top Co -axial, flush 9p MT30/2 0-12-15-20-24-30V, 2A- MINIATURE ELECTROLYTICS Phono, plated metal 11:D.I.N. 2 pin (speaker) I Op IµF63V6p 47µF I6V 7p D.I.N. 3 pin 9p L1.95 plus 30p p. & p. 6p 47µF 25V 6p Wander, red or black MT60/ I 0-5-20-30-40-60V,IA - 2.29F63V Banana 4mm, red or black 6pD.I.N. 5 pin, 180' 9p 3.3µF63V6p 68µF 6V 6p D.I.N. 5 pin, 240' 9p 12010 plus 30p p. & p. 1009F OV 6p MT60/20-5-20-30-40-60V, 2A- 4.7µF63V6p Jack, 2Imm 10p 8µF 40V 7p 220µF 6V 7p LINE SOCKETS Jack, 3fmrn 10p f.2.95 plus 34p p. & p. 1 1p Ch 10µF25V6p 330µF 6V Car aerial 14p Jack, fin unswitched ISp CTIOI 1A-L1.05 plus 26p p. & p. 10µF 64V7p 470µF OV lip Co -axial 17p Jack, fin switched I 7p CT/02 2A-11.30 plus 30p p. & p. 16µF 40V7p 1,000µF 6V 19p D.I.N. 2 pin (speaker) 15p Jack, stereo, switched 249 CT/03 4A-t1.60 plus 30p P. & 33µF I6V6p 1,500µF 6V 13p D.I.N. 3 pin 16p Phono, single Sp Secondaries -0-5-11-17V. D.I.N. 5 pin, 180' 16pPhone, 2 on a strip 7p D.I.N. 5 pin, 240' 16p Phone. 3 on a strip 9p Speaker Matching 3-8-1611 CASSETTE OWNERS' 10p Example: 1611 speaker to 811 Jack, 3frnin ISpPhono, 4 on a strip amplifier. 90p plus 20p p. & p. For Philips and similar cassette recorders. Jack, fin screened 49pWander. single, red or black Sp P012 Power unit for connection to Jack, stereo, screened 34pWander, twin strip 7p 12V -1- or - Ecarelectrical Phono, plated meta! 14p Banana 4mm red, or black 6p SEMICONDUCTORS, etc. systems, giving 7+V, stabilised £3.25 Zeners--400mW, ISp; 1.5W, 2.2fp output. L.D.R.-ORP12, 56p P014 As above but switched for £5.10 S.C.R.-400 P.I.V., 3.0A, 57p 6V, 71if or 9V output. CAPACITORS 0.00279F 500VS/M 15p Bridgerectifier -40 P.I.V.,I .5A, PP75 Mains power supply, output £1.95 0.003µF 500VCer. Sp 125V P.S. SOp 7+V d.c. 2.2pF 500VS/M 7p 0.0033µF 6p Bridge rectifier -200 P.I.V., 2.0A, All units are complete with cable and plug. 3.3pF 500V S/M 7}p 13-0033µF SOOVPoly. 6p 50p 5pF 500V S/M 7 p 0.00339F I,000V MDC 6p Transistor sockets -7p CASSETTES IODF I25V P.S. Sp 0.0036µF 500VS/M 15p D.I.L.I.C.sockets-I4 pin,2.0p; I OpF 500VS/M Tip 0.0047µF 125V P.S. 9p 16 pin, 20p Top quality British made, low noise, complete I SpF 125V P.S. Sp 0.0047µF 500V Poly. 6p 1N4001-50 P.I.V., 1.0A, 6p with transparent library cases- 15pF 500VCer. 4p 0-0047µF 500V S/M 20p I N4002-100 P.I.V., 1.0A, 79 C60-40p ; C90 -55p; Cl 20-70p 18pF 500VS/M 7+1, 00047µFI,000V MDC 6p I N4003-200 P.I.V., 1.0A, Sp 22pF I25VP.S. Sp 00059F IOOV Mylar 3p I N4004-400 P.I.V., 1.0A, 9p 22pF 500V S/M 7p 0.0059F 500VCer. Sp I N4005-600 P.I.V., 1.0A, lip BATTERY ELIMINATORS 25pF 500V S/M 74p 00068µF I25V P.S. 10fp suitable for transistor radios and similar light 27pF 500V Cer. p 0.0068µF 500VS/M 30P current equipment 339F I25V P.S. Sp 0-00689F 500VPoly. 6p ALUMINIUM BOXES PP6 Input 240V a.c.Output 6V d.c. 33pF 500V SIM 7 0.00829F 125V P.S. 10Ip with lids and screws PP9 Input 240V a.c.Output 9V d.c. 39pF 500V S/M 7}p 0p0082µF 500V NM 30p Type L. W. D. Price p. & p. Price 41.50 plus 12p p. & p. 47pF 125V P.S. 00 µ0011pFF IBV Disc 4p GB7 Slin 2finIfin 311p 15p 47pF SOOVCer. 4pP I25V P.S. 10fp GB8 4in 4in Ifin 3Sp 15p 50pF 500V S/M 0.01µF 160VPoly. 4p GB9 4in 21.in'fin 3Sp 13p 56pF 500VS/M 7 p 0.01µF 250V M.F. 3p G1310. 5fin 4in !fin 44p 18p ILLUSTRATED 68pF I25V P.S. p 0 01µF 400VPoly. 3p GB11 4in Ifin 2in 311p 13p 68pF 500V5/M 7p 0-131µF 500VCar. Sp GBI2 Sin 2in lin 33p 13p CATALOGUE 75pF 500VS/M 7}p 0.01µF 500V NM 30p GBI 3 6in4in2in51p 18p 829F 500VS/M 7 p 0.01µF 600V MDC 7p GBI4 Tin Sin 2fin 63p 19p 15p 00pF I25V P.S. Sp 0.01µF I,000V MDC 9p GBI5 Bin 6in 3m Sip 26p Post Free 00pF 500V S/M 74p 0.015µF 160VPoly. 39 GBI6 10in 7in Sin 92p 26p 00pF 500VCer. Sp 0.015µF 400V Poly. 3p These sizes fit 20pF 500V S/M 7fga 0-02µF 100V Mylar standard CONTROLS, Log. or Lin. 50pF I 25V P.S. Sp 0-022µF I8V Disc Sp veroboards Single, less switch, 15p 50pF 500VS/M 7fp 0022µF 250V M.F. 39 Single, D.P. switch, 24p 50pF 500V Cer. Sp 0-022µF 400VPoly. 3p Tandem, less switch, 40p 80pF 500V S/M 7+p 0-0229F 600V MDC7fis 5k11, 10k 0, 25k11, 50k11, IOOkfi,250k11, 200pF 500V S/M 71p 0.0229F 1,000V MDC 10p EQUIPMENT CASES in plain 500k12, IM11,2M11 220pF 125V P.S. Sp 0.0339F 250VM.F. 4p aluminium with sloping front Panel. 220pF 500V Cer. Sp 0.033µF 400VPoly. 4p Type H. W. D. Price P.& p. 250pF 500VS/M Sp 0.0479F 12V Disc 6p SFI 2in 51 in 2fin 45p 12p RESISTORS 270pF 500VCer. Sp 0.047µF 160V Poly. 3p SF22in7/in 3fin 60p 16p Carbon 300pF 500VS/M Sp 0047µF 250VM.F. 3p SF3 2in9fin4fin 75p 19p All 5%, high -stability, Eli values.4W, Ip; 330pF I25V P.S. Sp 0.047µF 400VPoly. 4p Stove - enamelled +W, Ifp; IW, 4p; 2W, 6p 330pF 500VS/M Sp 0.047µF 600V MDC 8p silver-greyham- Wire -wound 390pF 500V S/M Ilis 0-047µF I,000V MDC 10p mer finished, 25p raimw°1 SW, 10p; IOW, 12p 470pF 125V P.S. Sp 0.1µF 30V Disc 6p extra. 470pF 750V Disc Sp 0.IµF 250VM.F. 4p 500pF 500VS/M Sp 0.IµF 400VPoly. Sp CONSOLE CASES SWITCHES 560pF SOOV S/M Sp 0.1µF 600V MDC 10p in plain aluminium, ideal for mixers. Toggle switches, standard size. 680p F I25V P.S. 6p 0.IµF I,000V MDC 14p instruments, etc. 680pF 500V S/M Sp 0 159F 250VM.F. Sp Type W. ABC 12 Price p. & p. SW20-S.P.S.T. lip; 5W21-D.P.D.T. 23p. 820pF SOOV S/M Sp 0.22µF 160VPoly. 6p Push Button, miniature, SW I -13p. 0.001µF IOOV Mylar 3p 0.229F 250V M.F. Sp inin in in in 0.00IµF I25V P.S. 6p 022µF 400V Foil 10p 3 30p Wafer switches (rotary) -24p each. GB20 B 9 3+2 1141 0-00IµF 400V Poly. 3p 0.22µF 1,000V MDC ISp GB2I 3 11.511 30p SW4-1 pole, 12 way. SW5-2 pole, 6 way. 10 9 3+2 0.001µF 500V S/M 10p 0.33µF 250VM.F. Sp 9 312 3 30p 0822 12 1142 5W6-3 pole,4 way, SW7-4 pole, 2 way. 0.00IµF 500V Cer. Sp 047µF 250VM.F. Sp Id SW8-4 pole,3 way. 0.001µF I,000V MDC 6p 0-47µF 400VFoil 1Sp 0.00159F 400V Poly. 39 0-47µF I,000V MDC 15p 0.00 I 5µF 500VS/M 10p 1-13µF 250VM.F. ISp b Z BONDED ACRYLIC FIBRE 0.0015µF 500V Cer. Sp B.A.F. wadding, 18in wide. lin thick. The 0.0018µF 500VS/M 10p Note: I A ideal lining for speaker enclosures. 30p per 0.002µF IOOV Mylar 3p S/M =silver mica 1% tol. yard. p. & p. one yard 12p; each extra yard 4p. 0.002µF 500V Cer. Sp P.5. --polystyrene 2}% tol. 0.0022µF 125V P.S. 6p MDC-a.c. raisin; =300V. VEROBOARD M.F. =Mullard min. foil. 0.1 015 TYGAN top quality loudspeaker covering 0.0022µF SOOV S/M 10p Size matrix matrix material. Please send 6p for samples, sizes and 0.0022µF I,000V MDC 6p Cer. =ceramic. 1 xx 31Inn 11p 16p prices. in 24p 15p 3 in x nin 14p 25p MAGNETIC COUNTERS MAIL ORDERS Some items have apost and packing 3 in x in 27p 29p ,harge shown against thew.Where p. & p. is not shown Iin x 2in 75p 57p Brand new, neat, 48 volt, the charge is lip for any selection.When both classes of I7in x 31in II 750 5 digit counters. 60p goods are ordered the charge is lip plus any p. p. charges Pins-either size, packet of 36, lep shown.(Overseas extra.) Telephone 01.692 4411

Practical Electronics March1973 2,71 BI-PRE-PAK COMPLETE TELEPHONES TRANSISTO CATALOGUE - EX. G.P.O. NORMAL 1,000,000 IN STOCK FREE HOUSEHOLD TYPE FOR .) 1 We hold a very large range of fully marked, tested and guaranteed Tran- TRANSISTORS, ONLY 95p RECTIFIERS, sistors,Power Transistors,Diodes II POST & PACKING 35p EACH DIODES, andRectifiersatvery competitive INTEGRATED prices. Please send for Free Catalogue. CIRCUITS, TELEPHONE DIALS FULL PRE-PAK Standard Post Office type LISTS Guaranteed in working order. Silicon Planar PlasticTransistors, 1 600 000 ONLY 25p unmarked, untested, POST & PACKING 15p factory clearance. A random sampling showed these to be of remarkably high quality. RELAYS FOR TESTED AND GUARANTEED PAKS AUDIO PNP,similartoZTX500, VARIOUS TYPES 1 B2 4 Photo Cells, Sun Batteries. P. & P. 25p 0.3 to 0.5V, 0.5 to 2mA 31.1p 2N3702/3, BCY70, etc. AUDIO NPN, 879 4 IN4007 Sil. Rec. diodes. similar to ZTX300, 2N3708/9, BC107/ I amp. plastic SOp 1,000 PIV 8/9,8C168/9,etc. RF NPN and INTEGRATED CIRCUITS BB I 10 Reed Switches, mixed types SWITCHING NPN types also. large and small 50p Please state type of Transistor 1-12 13-25 26.50 B99 200 Mixed Capacitors. Approx. Clocked Flip Flop, BMC931 20p Op 6p quantity, counted by weight211.lp required when ordering. Ex. 2/4 -input Buffer,BMC932 12p Pp Op H4 250 Mixed Resistors. Approx. ALL TYPES: 500 for E3 2/4 -input Expander, BMC933 12pIp Op quantity counted by weight p Hex. Inverter, BMC934 12pIp Op 1,000 for LS Hex. Inverter, BMC935 12p Ip Op H7 40 Wirewound Resistors. Mixed SOp 10,000 for E40 Hex. Inverter, BMC936 lipIp Op types and values P. & P. 10p for 1,000 Hex. Inverter, BMC937 12p Ip Op H9 2 OphCoPt7.1TLriagn/t I,Soernsitive Hex. Inverter, BMC940 12pIp Op 50p Hex. Inverter, BMC94I 12pIp Op H28 20 0c20011,2/3 PNP Silicon OUR VERY POPULAR 3p TRANSISTORS Type D Flip Flop, BMC942 20p 13p 6p uncoded TO -5 can Ex. 2/4 -input Power,BMC944 12pIp Op TYPE "A" PNP Silicon Alloy, TO -5 can. Clocked Flip Flop, BMC945 20p Bp6p H3020 I Watt Zener Diodes, 50p TYPE "8" PNP Silicon, plastic encapsulation. 4/2 Input Nand GateBMC946I Ip Op 9p Mixed Voltages 6'8-43V TYPE "E" PNP Germanium AF or RF. Clocked Flip Flop, BMC948 3.0p Bp 6p H35 100 Mixed Diodes, Germ. Gold TYPE "F" NPN Silicon plastic encapsulation. 4/2 Input Nand Gate BMC949 lipIp Op bonded, etc. Marked and 50P TYPE "G" NPN Silicon, similar ZTX300 range. Pulsed Trig. Binary, BMC950 10p 8p6p Unmarked TYPE "H" PNP Silicon, similar ZTX500 range Monostable Multivib. 8MC951 25p 13p 21p H3830 Short lead Transistors, Dual J/K Flip Flop, BMC953 20p 18p lop NPN Silicon Planar types SOp Dual J/K Flip Flop, BMC955 20p lap 16p Dual J/K Flip Flop, BMC956 20p I8p 16p H3910 Integrated circuits 6 gates SClp POWER TRANSISTOR Quad. 2 -input Power, BMC958 12pI 1p 10p BMC 962, 4 flip flops BMC 945 2/4 -input Gate, BMC96 I12p Ilp 10p H40 20 laYN5n.2,,Nu69n6c,oredlEir13,-s PRICE BREAKTHROUGH! 3/3 -input NAND Gate, BMC962 lip 10p9p SOp Plastic Cased Silicon PowerTransistorsOof 3/3 -input NAND Gate, BMC963 lip Ilp 10p UNMARKED UNTESTED PACKS latestdesign. 40watts and 90 watts. Audio Amp. 3 -watts, LI-SO LI.40 LI.36 PNP and NPN types.All types available SL403D 131 50 Germanium Transistors at the most shatteringly low prices Linear Op. Amp, 709C 25p 10p 15p PNP, AF and RF 50p ofalltime.Allarefullytested, Decade Counter, SN7490 65p 60p 55p B66 150 Germanium Diodes marked and guaranteed! Min. glass type SOp 1-12 13-25 26-50 B83 200 Trans. manufacturers' re- 40W NPN 20p 18p 16p jects all types NPN, PNP, 50p 40W PNP 21p 19p lip LOW COST DUAL IN LINE I.C. Sil. and Germ. 90W NPN 24p 22p 20p SOCKETS 90W PNP 25p23p 21p s: B84 100 Silicon Diodes DO -7 glass PAKS complementary pairs: 14 pin type at 15p each I Now new low equiv. to 0A200, 0A202 Sap MP40 40W + 40WSOp 48p 46p 16 pin type at 16p each profile type. 886100 Sil. Diodes sub. MP90 90W + 90W 60p58p56p IN914 and 6mti::Pes sop Please state if NPN/PNP or NPN/NP B88 SO Sil. Trans. NPN, PNP are required. BOOKS equiv. to 0C200/1 SOp 2N706A, BSY95A, etc. We have a large selection of Reference and Technical Books in stock. 40 250mW. Zener Diodes A CROSS HATCH GENERATOR H6 50p These are just two of our popular lines: DO -7 Min. Glass Type FOR 13.50 ! ! ! B.P.I. Transistor Equivalents and T'"o.''ion Rectifiers, Substitutes: 40p H1530 ,,A Mixed volts sop YES, a complete kit of parts including Printed This includes many thousands of British, H16 Is Experimenters' Pak of Circuit Board.A four positionswitch gives U.S.A., European and C.V. equivalents. IntegratedCircuits. Data 50p X -hatch,Dots,VerticalorHorizontallines. The Iliffe Radio Valve & Transistor supplied Integrated Circuit design for easy construction Data Book 9th Edition: 7Sp and reliability. This is a project in the September Silicon Stud Recti- Characteristics of 3,000 valves and tubes. 20 SOp edition of Practical Television. 4,500 Transistors, Diodes, Rectifiers and fiers,aerTP,.:n ixed volts. Integrated Circuits.Post and Packing 21 p H2O 20 50p This complete kit of parts costs Send for lists of these English publications. volts E3.50, post paid. H34 Power Transistors, PNP, ISGerm. ,T,Irl:Nsicn O SOp A MUST for Colour T.V. Alignment. Can Ap mu in um % Our famous PI Pak is still Please send me the FREE Bi-Pre-Pak Catalogue. MAKE A REV COUNTER leading in value for money. IINAME

FOR YOUR CAR Full of Short Lead Semiconductors & Electronic ADDRESS to, Components, approx.170. We guaranteeat The 'TACHO BLOCK'. This least30reallyhighqualityfactory marked encapsulated block will turn Transistors PNP & NPN, and a host of Diodes any0-ImAmeterinto a & Rectifiers mounted on Printed Circuit Panels. linear and accurate rev. IdentificationChart suppliedtogivesome counterforanycarwith information on the Transistors. IMINIMUM ORDER 50p. CASH WITH ORDER normal coil ignition system. PLEASE. Add 10p post and packing per order. Please ask for Pak P.I. Only 50p. ADD EXTRA FOR POSTAGE, £1 each 10p P & P on this Pak.

DEPT. A. 222-224 WEST ROAD, WESTCLIFF-ON-SEA, ESSEX

INI TELEPHONE: SOUTHEND (0702) 46344

272 PracticalElectronics March1973 Build yourself a TRANSISTOR RADIO WITH AFTER SALES SERVICE ROAMER 10 WITH VHF INCLUDING AIRCRAFT 10 TRANSISTORS.9 TUNABLE WAVEBANDS. MEWL MW2, LW, SW1. SW2. SW3. TRAWLER BAND. VHF AND LOCAL STATIONS ALSO AIRCRAFT BAND. TOTAL BUILDING Built-in ferrite rod aerial for MW/LW. Retractable, chrome plated 7 section telescopic COSTS aerial, can be angled and rotated for peak short wave and VHF listening.Push-pull output using 600mW transistors. Car Aerial and tape record sockets. 10 transistors plus 3 diodes.Fine tone moving coil speaker.Ganged tuning condenser with VHF section.Separate coil for Aircraft Band. Volume/on/off, wave change and tone controls. 050 Attractive case in black with silver blocking.Size 9in X 710 x 4in. P.P. & INS. 50p Easy to follow instructions and diagrams. Parts price list and easy build plans 30p (FREE with parts). Earpiece with plug and switched socket for private listening 30p extra. (OVERSEAS P. a P. El)

ROAMER ROAMER ROAMER EIGHT SEVEN SIX Mk. I Mk. IV NOW WITH 7 TUNABLE VARIABLE WAVgBANDS: MW1,-MW2, LW, TONE SW1, SW2, SW3 CONTROL AND TRAWLER 6 TUNABLE BAND. Extra 7 TUMBLE WAVEBANDS: MW1, MW2, LW, SW1, WAVEBANDS: medium waveband provides easier tuning of Radio MW% LW. SW2, FM AND TRAWLER BAND. Built-in ferrite rod Luxembourg, etc.Built-in ferrite rod aerial for MW aerial for MW and LW. Retractable chronic plated tele- SW1, SW2. scopic aerial for short waves. Push-pull output using and LW. Retractable 4 section 24in chrome plated TRAWLER telescopic aerial for SW. Socket for car aerial. Power - BAND PLUS AN EXTRA MW BAND FOR EASIER 600mW transistors. Car aerial and tape record sockets. MI push-pull output. 7 Selectivity switch. 8 transistors plus 3 diodes. Fine tone transistors and 2 diodes, TUNING OF LUXEMBOURG, ETC.Sensitive ferrite including micro -alloy R.F. transistors. Fine tone moving rod aerial and telescopic aerial for short waves.3in moving coil speaker.Air spaced ganged tuning con. coil speaker. Air spaced ganged tuning condenser. speaker. 8 stages -6 transistors and 2 diodes including denser.Volume/on/oft, tuning, wave change and tone Volume/on/off, tuning and wave change controls. Attractive case in rich chestnut shade with gold controls. micro -alloyR.F. transistors,etc.Attractive black blocking. Size 9in x 710 N 4in approx. Easy to follow Attractive case with carrying handle. Size 9M X 7in x casewith redgrille,dial andblackknobs with instructions and diagrams. 4in approx. Easy to follow instructions and diagrams. polished metal inserts. Size 9in x 51in x 2:in approx. Parts price list and easy Parts price list and easy build plans 25p (FREE with Easy build plans and parts price list 25p (FREE with build plans 25p (FREE with parts). Earpiece with plug parts).Earpiece with plug and switched socket for parts). and switched .0:et for pi hale listening 30p extra. private listening 30p extra. 0 P. P. & INS. 45p & INS. 45p P. P. & INS. 30p TOTAL TOTAL £5.98 (POVPERSEAS TOTAL BUILDING COSTS£6.90 (OVERSEAS BUILDING COSTS BUILDING COSTS£3.98 (OVERSEAS & P.I) P. a P. El)

POCKET TRANSONA TRANS FIVE FIVE EIGHT 8 TRANSISTORS AND 3 DIODES 6 TUNABLE 5 TRANSISTORS WAVEBANDS: 8 TUNABLE WAVE - MW, LW. BARDS: MW, LW. AND 2 DIODES SW1, SW!, TRAWLER BAND SW3 AND WITH EXTENDED TRAWLER MW BAND FOR EASIER TUNING OF LUXEM- 3 TUNABLE WAVE BANDS: MB% LW AND TRAWLER BAND. Sensitive ferrite rod aerial for MW and LW. BOURG, ETC. 7 stages -0 transistors and 2 diodes, BAND. 7stage -3 transistors and 2 diodes,ferrite Telescopic aerial for short waves.31nspeaker. 8 supersensitive ferrite rod aerial, fine tone moving coil rod aerial, tuning condenser, volume control, fine tone improved type transistors plus 3 diodes.Attractive speaker.Attractive black and gold case. Size 51in x movingcoilspeaker. Attractivecasewithred case in black with red grille, dial and black knobs with ltln X 31in.Easy build plans and parts price list speaker grille.Size 81in x 4I in x llin.Easy build polished metal Inserts. Size 9in x 51in x 21in approx. 10p (FREE with parts). Push-pull output.Batteryeconomiser switchfor plans and parts price list 10p (FREE with parts). extended battery die. Ample power to drive a larger speaker.Parts price list and easy build plans 25p (FREE with parts). TOTAL TOTAL . & INS. 24p BUILDING COSTS (OVERSEAS BUILDING COSTS f2.50(OVPERSEAS 32p £229 P. P.P. & P. INS.63p) 23p P. & P. 63p) TOTAL BUILDING COSTS£4.48 (OVERSEAS P. & P. El) I NEW! "EDU-KIT BUILD RADIOS. AMPLIFIERS. ETC.. FROM EASY STAGE DIAGRAMS. FIVEsUNITS INCLUD- ING MASTER UNIT TO CONSTRUCT. Components 61a HIGH ST., BEDFORD MK401SA. Tel. 0234 52367 include: Tuning Condenser: 2 Volume Controls: 2 Slider Switches: Fine tone moving coil Speaker: Terminal Strip: Ferrite Rod Aerial: 3 Plugs and I enclose £ please send items marked Sockets: Battery Clips: 4 Tag Boards Balanced Armature Unit: 10 Transistors: 4 Diodes: Resistors: Capacitors. ROAMER TEN ROAMER SEVENEi Three tin Knobs. Unita once con- structed are detachable from Master ROAMER EIGHT D TRANS EIGHT Unit, enabling them to be stored for future use. Ideal for Schools, Educa- tional Authorities and all those in- TRANSONA FIVE D ROAMER SIX 0 terested in radio construction.Parts

price list and easy build plans 25p (FREE POCKET FIVE EDU-KIT with parts). ALL PARTS Parts price list and plans for INCLUING CASE AND PLANS£5.50(OVERSEAS P. & P. El) Name FULL * Callers side entrance "Lavell" Shop Address AFTER SALES SERVICE * Open 10-I, 2.30-4.30 Monday -Friday, 9-12 Saturday _ L$ ----.- 1=1 PE Si PracticalElectronics March 1973 273 QUALITY COMPONENTS - BUDGET PRICES PSYCHEDELIC LIGHT UNIT IN KIT FORM Make this fascinating three channel unit from a kit which contains all the components needed to produce a reliable and entertaining display. Takes its drive from the speaker terminals of a record player, tape recorder or portable transistor radio.Will produce a brilliant 2kW of light using normal 240V lamps. All components with full step-by-step instructions .. L9.45 ASWAN RESISTORS 10% Carbon, E12 values, VOLUME CONTROLS 10-10M 4W .. . Ito Global's GOLDEN Small size, LOG or LIN lw ' .. .. .: ii, Ottarantet 5% Hystab, E24 values, 5,10. 25, 50, 100, 250, SOOk 0 WE GUARANTEE THAT WITHIN 7 DAYS OF PURCHASE 10-1M, +/4W .. .. 21p IMO IF ANY ITEM OF GOODS IS KUNO TO BE GENUINELY DEFECTIVE WE WILL REPLACE THE SAID GOODS 2% M.O. E24 values. Only 16p each WITHOUT QUESTION AFTER 7 DAYS GOODS ARE 10-1M, 4W .. 4p COVERED BY MANUFACTURERS IT MONTHS CAPACITORS GUARANTEE Tantalum-µF/V: 0.1/35, 0.22/35, 0.47/35, 1/35, 2-2/35, 4.7/35.10/63,10/25, 10/16, 22/16, 47/6. . 100/3. All at one price ...... 17p GARRARD SP25 Mk. III AMPLIFIERS Moulded Polyester 250V: 0.01, 0-022, 0033, Sp; 0.047, 0068, 0.1, 7p; Please add 85p P. & P. & Ins. 0.22, 10p;0-33, lip;0 47, 15p;0.68, 18p; SPECIAL PURCHASE Amstrad 8000 Mk. II L15.00 1.0, 7.2p; 2.2, 35p. LIMITED NUMBER Amstrad 1C2000 L28.25 Printed Circuit Electrolytic-µF/V, 0.47/63, 1.0/63, 2.2/63, 4.7/40, 10/63, AVAILABLE Amstrad Integra 4000 L22-50 22/40, 7p; 47/40, 10p;100/63, 13p; Garrard SP25 Mk. III E16.95 Armstrong 521 (Teak cased)L44-40 100/10,7p;220/40,470/16,ISP; Goldring G800 Alpha Highgate 212 1,000/16, 15p. Teak plinth and tinted cover. Alpha Highgate FA300 All leads supplied. L32.25 FIXED VOLTAGE REGULATORS Please add El 25 P. & P. & Ins. Alpha Highgate FA400 L35.65 TO3 case.Gives stabilised supply.MVR 5V, MVR I2V, MVR ISV. Leak Delta 30 [44-85 All at (1.50. Leak Delta 70 L5490 Metrosound ST2OE L24.90 TRANSISTORS TURNTABLES Metrosound ST60 L45.00 AC107 28p AD 149 47p BC168 lip 0&72 19p Pioneer SA600 & 610 L57.00 AC126 27p BC107 12p BC169 20p 0075 22p Please add 75p P. & P. &Ins. ACI27 523p BC I08 12.pBDII2 44p 008 I D 19p L9.90 Pioneer SA900 L87.95 Garrard SP25 Mk. III Pioneer SA1000 L93.25 AC128 20p BC109 12p BFY51 23p 2N2926 13p Garrard AP76 L17.45 Rogers R/brook (Chassis) L37.75 AC132 19p BCI47 209 0C28 Sip ADI61 1. .,. Garrard SL658 L13.93 Rogers R/brook (Cased) L41.50 ACI76 20 BC148 2.0p 0071 14p ADI62 I'.1) Pr Garrard 401 L28.95 Rogers Ft/bourne (Chassis) Garrard Zero 100 (Auto) L37.50 (49.45 PRINTED CIRCUIT BOARD Rogers R/bourne (Cased) L52.45 Approximate size: I2in , 8in.Bargain at only 25p per board. Garrard Zero 100 (Single) L35.80 Sinclair PRO60 2 BSR MP60 L9.40 r Z30/PZ5 L14.70 VEROBOARD SERVICING AIDS - Sinclair PRO60 2 x Z30)PZ6 L16.70 AEROSOLS Goldring GL72 020.50 Sinclair PR060 2 Z50rPZ8/ Freezer .. .. . 60p Goldring GL72/12 427.00 rans f20.90 0.1 0.15 . 16p Contact Fluid .. 75p Goldring GL75 L26.90 Sinclair AFU (Filter Unit) [4.20 2fin 31in 2.0p ,. 24p 26p Insulating Lacquer 80p Goldring GL75/P L34.00 Sinclair 605 L17.95 3lin Sin Goldring 10I/P.C. L20.00 Sinclair 2000 Mk. II E20.95 The above shows only a ve y small selection from our Wharfedale Lintori +cart. L26.50 Sinclair 3000 Mk II L28.15 CATALOGUE price 25p post free by return Thorens TDI25A8 Mk. II L92. 95 Wharfedale Linton All orders over 50p POST FREE in U.K.S.A.E. with all queries. L26.80 L42.95 Thorens TD150 Mk. II Teleton SAQ 307 L12.95 We can supply ALL R.S. COMPONENTS, mostly by return of post Thorens TDI60 AB & C L56 00 Rota! RA3I0 L34.50 Rotel RA6I0 f51.75 CELECTRON-E TUNERS SPEAKERS P.O. Box No. I, Llantwit Major, Glamorgan, CF6 9YN Please add 85p P. & P. & Ins. Please add LI-SO per pair P. & P. Amstrad Multiplex 3000 L29.50 & Ins. Armstrong 523 L39.50 Price per pair Armstrong 524 L31.45 Amstrad 138 L13.90 Rogers R/brook FET4 Wharfedale Denton 2 L28.50 (Chassis) L37.25 Wharfedale Linton 2 435.80 Rogers (2/brook FET4 Wharfedale Melton 2 L46.95 (Cased) L43.50 Wharfedale Dovedale 3 459.95 GUNTON ELECTRONIC Rogers R/bourne FET4 Celestion Ditton 120 L39,75 c£795 (Chassis) L44.95 Celestion Ditton 15 (50.90 IGNITION KIT Rogers R/bourne FET4 Celestion Ditton 25 /8495 (Cased) L47.95 Celestion County (new prod.) L313.95 READY BUILT UNIT (60 AOC+ 35 Sinclair PRO60 (Module) L15.60 Goodmans Double Maxim L47.75 GUARANTEED 5 YEARS .P. & P. Sinclair 2000/3000 Tuner L29.30 Goodmans Mezzo 3 44475 Patents Pending.12 volt only -state pos. or neg. earth. Leak Delta FM (Cased) L53.65 Goodmans Magister L82.00 Capacitive discharge ignitionisrecognised as being the most efficient Leak Delta AM/FM (Cased) L62.95 system and will give you: Alpha Highgate FT150 L38.00 * Continual Peak -Tuned Performance Special Bulk Purchase * Up to 20% reduced fuel consumption * Easier All-weather Starting TUNER/AMPLIFIERS * Increased Acceleration and Top Speed £2.90 * Longer Spark Plug Life Please add LI P. & P. & Ins. * Increased Battery Life Alpha Highgate 150 L49.75 Plus 65p P. & P. & Ins. * Elimination of Contact Breaker Burn Armstrong 525 (Teak cased) L69.45 Finished in teak veneer with tinted * Purer Exhaust Gas Emission Armstrong 526 AM/FM dust cover.(Fully assembled).For Kit includes absolutely everything for assembly:Case,Cables,Cool (Teak cased) L77.25 Garrard SP25; 2025TC; 3000; Connectors, Silicon Grease, etc.8 page illustrated instructions cover Leak Delta 75 L120.00 AT60;2000;2500;3500;5100; fitting of all types of tachometers.Call in for a workshop demonstration. Alpha RI50 L48.95 1025: 5L658. Also for BSR, S.A.E. all enquiries please, or Phone 33652. (Many letters from satisfied Philips RH702 L82.50 McDonald MP60 and others. customers.) Teleton 2100 L31-00 ForAP76;AP75;SL72B;SL75: SCORPIO: Transformer L1.85 +25p P. & P.P.C.B. 65p +10p P. & P. Goodmans One Ten 198.90 SL95B.L3.95 + 65p P & P. & Ins. Special interference filter 65p +10p P. & P. Rogers Ravensbrook Also finishedinwalnut to match (Teak cased) L78.25 Japanese equipment -at no extra. Rogers R/brook (Chassis) L73.50 Alpha FR 3000. New product 02.00 CARTRIDGES ALUMINIUM BOXES Please add 35p P. & P. & Ins. Complete with baseplate and screws All prices correct Goldring G850 L3.15 at time of Pre. Goldring G800 L4.95 E. & 0. E. and are Goldririg G800E L7.50 AT DIRECT FROM MANUFACTURERS' PRICES WITH RETURN subject to Goldring G800 Super E L14.15 OF POST SERVICE alterations. Shure M3D L3.70 Shure M5SE L560 Type No. Price P. & P. Ortofon SLI5 L15.95 7. 54 24 25p 15p Sonotone 9TAHC L1.40 4 4 25p 15p

9. 4 2.4 25p 13p 10. 51 4 29p 18p II 4 24 25p 13p

12 3 2 22p 13p 13 6 4 2 35p 18p Dept. (PE3) 174 Pentonville Road, London, N.1. Tel. 01-278 1769 14 7 5 24 42p 19p Or: 4 High View Parade, Redbridge Lane East, Woodford Avenue 15 8 6 3 54p 26p Ilford, Essex.Tel. 01-560 1086 16 10 7 3 6lp 26p Open Monday to Saturday 9.30 a.m. to These sizes accept standard veroboard range. 6 p.m. LATE NIGHT FRIDAY 7 p.m. Nos. 12 to 16 available 15th January onwards.

MAILORDERS: Order yv.oitr dhecrun foindke nce e PGiro siC inset Draft. Cashta1 O Dept. PE3, ELECTRONICS DESIGN ASSOCIATES Mail. CALLERS: Please note that can only be accepted togetner wttn cheque cards Inca Bareas Card). 82 BATH STREET, WALSALL WSI 3DE

274 PracticalElectronics March 1973 MAINS MOTOR POCKET CIRCUIT TESTER Precision made -as used in BATTERY MOTORS Test continuity of any low record decks and tape recor. A bagrain parcel of 7 motors for M.Borne not as resistance circuit, house dent -ideal also for extractor large as a postage stamp and only :in thick, wiring,carelectrim.Tests largest is lila x llin die.Some work off 14V polarity of diodes and rec- fan, blower, heaters, etc. New some as high as 18V.These motors are used in tifiers.Alsoidealsizefor and perfect.Snipat 65p. racing cars, power toys, etc.The largest is so conversion to signal injector Postage 20p for first one then powerful that it will drive a Mini drill, model lathe, (circuit supplied).309 or 2 10p for each one ordered. or similar.This is a 4 pole motor, optimum for 60p post paid. working 16.3V but very powerful even as low as MINIATURE 44V.Don't miss this wonderful snip. AMPLIFIER IN CASE WITH WAFER SWITCHES SPEAKER 2 pole, 2 way -4 pole, 2 way - COMPUTER TAPE Marketed by British Relay under the name 3 pole, 3 way -4 pole, 3 way -2 Lux istor. This is in a very neat looking cabinet and pole, 4 way -3 pole, 4 way -2 pole 2,400ft of the Best -Magnetic Tape money can buy -users claim is ideal around the home or in the workshop for 6 way -1 pole, 12 way. All at SKIP good results with Video and sound.lin wide 11.00 plus 30p post trouble shooting or for testing out a quick lash up. each 11-80 for ten, your assortment. and insurance, with cassette, !in wide 41-00 plus 30p post and glee approx. Siin x al in x 3} in deep. Input is via Insurance with cassette.)in wide 850 plus 21p post and insurance a matching transformer and volume control and l5A ELECTRICAL with cassette.Spare spools and cassettes-lin 759, I in 759 rech amplifier may be powered by an internal 9V PROGRAMMER plus 20p post and insurance. battery or an external 110V source. Speaker is an Learninyoursleep: TANGENTIAL HEATER UNITS R -A eliptical liin x 3; in 10,000 gauss. The ampli- Have radio playing and fier proper is a Newmarket model ref. P.C.4. Price kettleboilingasyou This heater unit is the very latest type, most efficient and quiet running.Is as 114.50 each, 10 for 231-50. Post and Insurance 20p. awake -switch on lights fitted in Hoover and blower heaters costing £15 and more. We have a few only. to ward off intruders - Comprises motor, impeller, 2kW element and 1kW element allowing switching 1 BAKELITE INSTRUMENT 2 and 3kW and with thermal safety cut-out.Can be fitted into any metal lin, CASE have warm house to come a.. case or cabinet. Only need control switch, 111140. home to.All these and many other things you Size approx. (Qin X3flnX can do if you invest in an electrical programmer 2kW.Model as above except 2 kilowatt. 12.50. 2m deep with brass inserts in Clock by famous maker with 13 amp. on/off Don't solos this. Control Switch Up. P. & P. 40p. four corners. This is a very strong switch.Switch on time can be set anywhere to case suitable to house Instruments stay on up to 6 hours.Independent 60 minute 0413and special rigs, etc.Price 45p each, memory jogger. A beautiful unit.Paull:95 + THISMONTH'S SNIP paxlid 10p extra. 20p p & p or with glass front chrome bezel 76p AMP YARIAC for 43 extra. TELEPHONES This heading is not quite accurate because itis not a variable transformer Complete. ae illustritied.Save i RESETTABLE FUSE that we are offering but a solid state device which serves the same purpose in your legs, time and temper, How long does it take you to renew a almost all applications and, of course, much entailer. fuse?Time yourself when next one Made by Ultra simply by putting in some Electronics, can be fitted into ordinary switch box. Engrave a circle on the telephones.Ex. G.P.O. not blows.Then reckoning your time at front plate, mark this off in divisions, fit a pointer knob, calibrate with your £1per hour new -but guaranteed in good see how quickly our voltmeter (you will find the scale almost linear) you now have a power conditionandserviceable. resettable fuse (auto circuit breaker) controller equal to a :3 amp variac costing £12 or more. will pay for itself.Price only Ill each or Supplied with diagram and 111 per dozen, specify OA, 10A or 15A -simply instructions showing how to connect. Price 75p each + 00P fiin place of switch. THYRISTOR LIGHT DIMMER post or 2 for 12 poet paid. FLUORESCENT CONTROL KIT For any lamp up to IkW. Mounted on switch plate to fit Also mailable separately, dials and handsets Rack kit comprises seven items -Choke, 2 tube in place of standard switch.Virtually no radio interference. 409 each + 20p post. ends, starter, holder and 2 tube clips, with Price 22.96, plus 20p post and insurance. ROCKER SWITCH wiringinstructions.Sultable for normal fluorescent 13A self -fixing into an oblong hole. tubes or the new "Orolux" tubes for fish tanks size approximately lin x tin Bp each. and indoor plants. Chokes are super -silent, mostly MULLARD UNILEX 10 for 729. resin filled. Kit A -13--20W, SI. Kit B -30-40W, This D.I.Y. Stereo Amplifier Is still available complete at 27 for the four II.Kit C -80W, 21-20.Kit E --63W, 2140. Mullard Modules, or Modules can be bought separately as follows: SLIDE SWITCHES Kit F for 8ft 125W tube 21.75.Kit MF1 is for 4W amp module (2 required) Mullard Ref. No. E.P.9000-11.05 each. Figlide Switch. 2.pole changeover pane Sin, Sin and 12In miniature tubes, 21.Kit MF2 Pre -amp module Mullard Ref. No. E.P.9001-11.60 each. mounting by two 6B.A. screws. Bikeapprox. for 21in 13W miniature tube, Al.Postage on Power module-Mullard Ref. No. E.P.9002-12.10 each. lin X tin rated 250V lamp. Kits A and B 23p for one or two kits then 29p In addition and made to Mullard Specification weoffer: 0p each.10 for 54p, 100 for 116.10, 500 for each two kits ordered.Kits C, 13 and E 23p Standard Control Unit with escutcheon -02.50 for 024. Ditto se above but for printed on first kit then 18p for each kit ordered.Kit F Knobs -Set of 4- 50P circuit 5p each, 10 for 44p, 100 for114.111. 33p then 23p for each kit ordered.Kit MF1 18p Bub Miniature MM. Smite's. DPDT 19mm on first kit then 13p on each two kits ordered. (fin approx.) between fixing centres. 18p each or MULLARD I.F.MODULE 10 for 01.08. BP Change over spring return 250V r-....' SOLDER GUN This is a fully screened intermediate frequency module IA. 10P. . A must for every busy man, gives for amplification and detection of f.m. signals at 10.7MIla almoettinatant heat alsoilluminated and a.m. signals at 470kHz. The first stage la used as an EDUCATIONAL KITS -all with job. 100 watt 1246 plus post and i.1. amplifier for f.m. and a self -oscillating mixer for a.m. pictorial instructions ins. 20p. BIG JOB 250W model operation, in conjunction with external oscillator coil. THIS BALANCE £4.75 plus post and ins. 40p. 85p each. 10 for 07.85. 100 for 062.50s. With connection die:- KIT FREE Eogleeducational WATERPROOF HEATING ATLAS kits. Japanese ELEMENT made these are TWENTYLITE excellent value 26 yards length 70W. Self-regulating FluorFluorescentescent lighting units with polyester choke and finished white enamel. for money. We temperature control.50p post free. model, ideal kitchen, bedroom, hallway, porch, loft, etc. With tube assembled do not expect to ready to Instal, 21.99, plus P. & P. 30p and insurance. be ables repeat this offer once stocks are sold. Brief description of each kit is given below and MAINS TRANSISTOR POWER PACK STANDARD WAFER SWITCHES with 3 kits or more we give FREE an accurate Designed to operate transistor sets and amplifiers. Standardsize14 inwafer -silver-plated 11 piece balance kit.Price of kits 40p each post Adjustable output 6V, 9V, 12V for up to 300mA 5 -amp contact. paid. Special price for all 8 kits ill with free (class B working).Takes the place of any of the standard tin spindle 2In long -with locking washer and nut No. of Poles 2 way Ii way 4 way 5 way 0 way 8 way 9 way 10 way 12 way balance kit. following batteries: PPI, PP9, PP4, PPS, PP7, Eleven parts, Including candle, PP9 and others.Kit comprises: mains trans. 1 pole HAS Lens Mt. former rectifier, smoothing and load resistor, 4Op 40p 40p 40p 400 409 40p 409 40p one concave lens, one convex lens, stage and slit poles 40p 40p 40p 409 40p 409 40p 70p 70p frame. etc.Watch light rays bend as they pass condensers and Instructions.Real snip at only 3 poles 409 2140, plus 20p postage. 409 40p 40p 70p 709 70p 95p 95p through different lenses. 4 poles 40p 40p 40p 70p 70p 70p 70p 1140 2140 poles 40p 40p 70p 70p 95p 95p 959 21.45 11.45 HA3 Water Pump Hit.Thirteen parts.Top of THERMOSTATS 6 poles pump Is transparent so that operating parts may Type "A" 13A for controlling room heaters, green- 40p 709 70p 709 959 95p 95p1140 21.70 be observed. Small parts are brightly coloured to houses, airing cupboards.Has spindle for pointer 7 poles 709 70p 70p 95p£120 £1.20 01.20 01.95 21.95 8 poles 709 709 70p 95p01.20 01.20 61.20 12.20 12.20 be seen easily while working.Three types of knobs. Quickly adjustable from 30-38 deg. F. 48p. 9 poles 709 pump may be made: Lift pump, Force Pump and Type "B" 10A.This is a 17In long rod type made 709 95p 95p1145 11.45 11.45 1245 2245 Force Pump with reservoir and nozzle. by the famous Sunvic Co.Spindle adjusts this 10 poles 70p 70p 95p 01.20 11.45 2145 2145 112.70 12.70 from 30-350 deg. F.Internal screw alters the 11 poles 70p 95p 95p 0140 21.70 21.70 21.70 02.95 12.915 KA4 Eager Kit.Eleven parts.Transparent setting so this could be adjustable over 30 deg. to 12 poles 70p 95p 95p 21.20 01.70 111.70 £1.70 £320 13.20 covers allow the operation of buzzer to be seen. 1,000 deg. F.Suitable for controlling furnace, Illustrates and teaches how electromagnetism with oven, kiln, immersion heater or to make flame-stat POCKET BLEEPERS an automatic switch results in an operating buzzer. or fire alarm, 50p plus 12ip post and insurance. NototEft.Twenty-fourparts Theseworkonquitealowfrequency,arecarriedinthepocket, Including enamel wire, armature and pole piece, Type "C. Simply clamp to tank, pipe, heatsink, and are mainly used inlarge buildings or areas so that key personnel casing.Break temperatureadjustable by may be contacted quickly.These contain two encapsulated circuits to energise etc.Motor operates from liV battery.Illus- calibrated knob 76p. the relay and cause the bleep as well as rechargeable nickel cadmium cells. trates and teaches how electro-magnetism operates Type "D '.We call this the Ice -stet as it cuts in Quite costly things to buy.The ones we have are not new, but believed to be in a motor. and out at around freezing point, 2/3A.Has good working order and sold on the understanding that if they are not, they will KA7 Electro-Magnet Hit. Fifteen parts, Includes many uses, one of which would be to keep the loft be replaced free.The size of the case, which is intended for carrying in top compass. Makes two electro-magnets,. one with pipes from freezing, if a length of our blanket wire pocket, Is approx. al in long, sin wide and ;In thick.Limited quantity at one layer of wire and one with several layers of (16yd) 50p is wound round the pipes.20p.P. & each. wire. Picks up tacks, nails and any small parts P. 5p. showing how magnetism works. Type "E".This is standard refrigerator thernto- HA8 Current and Resistance Hit. Twenty-nine atat.Spindle adjustments cover normal refri- parts, including bend! and light bulb.Conduct gerator temperature.50p plus Sp post. 9 VOLT BATTERY ELIMINATOR Interesting and educational projects to learn the SPARTAN Portable RADIO EI00 application of "OHMS LAW" and see the differ- Long and medium wave, 7 tran- ence in current and resistance with different types sistor,sizebin x 4in x ltin and lengths of wire. with larger than usual speaker PRESSURE SWITCH KA9 Bell Kit. Eight parts, including bell and push giving very good tone.Built-in We recently received a delivery of a very fine pressure switch made by button switch. Build a complete electric bell and ferrite aerial and telescopic aerial Bailey & Mackey. Their type no. 108R. This is an elaborate switch see how the hammer le triggered to make the bell for distant stations.A real and is adjustable to 16 p.a.i. but is set at 8 pa.l.It has a reset button and is of ring. bargain complete with leather very superior construction with a heavy brass body. We understand that the KAIO Norse Key Banner and Bell KO. Twenty- case, carrying sling, earplug regular price of this is £12 and we have limited stocks offered at 2440 each. five part kit, easy to construct, simple to operate. and case 23.75 plus 25p post and ins. Where postageis not stated then orders THE REHITONE TRANSISTOR over 05 are post free.Below £5 add 20p. Medium wave pocket loudspeaker radio. Loud J. BULL (ELECTRICAL) LTD. and with good tone will make wonderful Semiconductors add 3p post.Over £1 post present.Buy whilestockslast. Full money free S.A.E. with enquiries please. (Dept.P.E.),7 Park Street, Croydon CRO IYD back guarantee.21410 Only. Callers to 102/3 Tamworth Road, Croydon PracticalElectronics March1973 275 Practical Electronics Classified Advertisements RATES: 9p per word (minimum 12 words).Box No. 20p extra.Semi -Display £7 per single column inch.Advertisements must be prepaid and addressed toClassified Advertisement Manager, "PracticalElectronics" IPC MAGAZINES LTD., Fleetway House, Farringdon Street, London EC4H 4AD

BOOKS AND PUBLICATIONS THE PICTURE BOOK METHOD OF LEARNING SIC ELECTRICITY Spts £4.50. BASIC ELECTRONICS 6pts £5.40. BASIC TELEVISION 3pts E3.60 (Postage and Packingincluded) The Pictorial Approach Manuals assure the quickest and soundest method of gaining mastery over these subjects. The clear and concise illustrations make study a real pleasure. Your money refunded if not completely satisfied is your 100% Guarantee.Free Illustrated Prospectus on request. Send now to SELRAY BOOK CO., 60 HAYES HILL, BROMLEY BR2 7HP

KE.RIMONT BOOKS WANTED RECEIVERS AND COMPONENTS 110I.C. Projects (1971),11.20 +5p post; 110 Semi- conductor projects (1969), £1.20 + 5p post; Under- standingElectronic Components(1972).111.50; TransistorCircuitDesign Tables(1971),1210; DRY REED INSERTS Digital Logic (1971).11.50; AudioTechnician, TOP PRICES PAID Bench Manual (1972),18.00;T.V. Technician, Bench Manual (1971),2240:introduction to Semi- for new valves and components conductor Devices (1972),21.90 +5p port. Overalllength1.85'(Body length1.1"), Many others.Pleasesendforlists.Posttree Popular T.V. and Radio types Diameter 0.14- to switch up to 500 mA at up unless indicated. to250v D.C. Gold clad contacts. olioper KILRIMONT BOOKS (0), Kilrimoat House, London KENSINGTON SUPPLIES doz.;13.75per 100;L27'50per 1,000; aso per Road, Braintree. Suez 10,000. All carriage paid. (8) 367 Kensington Street G.W.M. RADIOXTD. THOSE 1,000 BANBURY UFO's!Details of 40/42 Portland Road, Worthing, dune: 0903 54IS7 our Prediction (and list) S.A.E. Numerous Bradford 8, Yorks. ('harts, Map, Detectors.R. & E. PUBLICA- TIONS, Highlands, Needham Market, Suffolk. SOLDERCON SERVICE SHEETS DIY PIN SOCKETS FOR I.C.'s DIGITAL COMPUTER Logic and Electronics. per pin precut 7's and 8's oranylength A four volume Self -instructional course, 12.99 SERVICE SHEETS forTelevisions,Radios, DALO FIBRE PEN postfree.Money backassurance.CAM- Transistors, Tape Recorders, Record Players, FILLED WITH ETCH RESIST 80p. BRIDGE LEARNING, SaRoseCrescent, etc.. from 5p with free Fault -Finding Guide. 1EF ELECTRONICS (P.E.3) Cambridge. S.A.E.orders/inquiries. Catalogue15p. York Mouse, 12 York Drive, Grappenhall, HAMILTON RADIO, 47 Bohemia Road, St. Warrington WA4 2EJ.Mail order only. Leopards, Sussex.Telephone Hastings 29066. C.W.O. P. & P. 9p per order.Price list free. FOR SALE Satisfaction or money back. SERVICE SHEETS, Radio, TV, etc.8,000 SEEN MY CAT? 5,000 Items. Mechanical and models.Catalogue 15p. S.A.E.enquiries. COMPONENTS-Integrated Circuits,Digital Electrical Gear, and materials.S.A.E. K. R. TELRAY, WHISTON, Dept. 1'E, New Mills, Stockport. Displays, Diodes, Resistors, Capacitors, Switches. List .3p. CAVERN ELEC TRONICS, 29ClarefieldRoad,Leicester FOR SALE. Ferrograpli Series Seven -half-track EDUCATIONAL I.E:3 Stereo.Also Tandberg Series 15 four -track. Box 48. HONS. DEGREE IN EDUCATIONAL ELECTRONIC ENGINEERING ENGINEERS.Get a technicalcertificate. Two academic years in college, one year in PostalcoursesinEngineering,Electronics, Radio,TV,Computers,Draughtsmanship, industry and a final academic year in college. Buildings,etc., FREE book from:ItIET (Dept. ZC BYE24),AldermastonCourt, HONS. DEGREE IN Reading. RG7 4PF.Accredited by l'ACC. ELECTRICAL ENGINEERING A SUCCESSFUL Three years on a six -monthly Polytechnic/Industry sandwich pattern followed by a final academic CAREER year in college. IN RADIO H.N.D. IN Get the s,...vss deserve-take ICS home study course.PassC6G. M.P.T.examsFIRSTTIME! Free books.' ELECTRICAL and ELECTRONIC Low cost.Personal tuition. Send TODAY for FREE Guide on Radio, TV, Electronics, Electrical Engineering. ENGINEERING Three year thin -sandwich course. Name For full details apply to Head of Department of Address Electrical and Electronic Engineering, North Staffordshire Polytechnic, Beaconside, Stafford or Dept. 730E1 telephone him at Stafford 52331. Stewarts Road, Please quote reference 2373/PE on both envelope London SW8 4UJ and letter. LIMI= MI MI ME TELEVISION TRAINING (MONOCHROME AND COLOUR) This private College provides theoretical and practical training in Radio and TV Servicing. Courses of 16 months' duration, with daily attendance, are available for beginners and shorter courses for men with EC previous traininginElectronics and Radio.Next course commences April 16th.Training courses inMarine Radiocommunication andRadar are alsoavailable. Write for prospectusto: London Electronics College, Dept. B/3, 20 Penywern Road, Earls Court, London SW5 9SU. Tel. 01-373 8721.

276 PracticalElectronics March 1973 BRAND NEW COMPONENTS BY RETURN, Electrolytics, 16V, 25V, 50V,1, 2.2, 4 7,10 mfds., 30; 22, 47,4p(50V,5p);100,by(50V, PRECISION it9111171.15 gh31111111111i Sp). Subminiature bead -type tantalums POLYCARBONATECAPACITORS All Brand New.No Rejects or 0.1/35V, 0.22/35V, 0.47/35V, 1/35V, 2.2/35V, Remarks. Money Back 4.7/35V, 10/16V,Sp. Mylar Film 100V, '001, FRESH STOCK - FULLY TESTED Assurance. .002, .005, '01, '02, 21i;'04,.05, 20; .068,'1, Close tolerance. High stability.All 63V d.c. DIGITAL INDICATORS: 3p.Polystyrene 6317, E12 series 10 pf.-10,000 0-47µF: ±5% 1109; *2% 40p;11% 50p 0-9DP,withsocketandred pf.,2p. 1.0µF: ±5% 409; ±2% 60p;±1% 60p alter, 1149.Nixie type, 97p. Miniature Highstab Resistors E.42 series 5% Third Watt Carbon Film 112-10Mi2. 22AF; *5% 60P; +2% 1105; *1% 75p A" LED 7SEG + DP 1)11 type, 47µF: *5% 70p;*2% 90p;*1% /1.11 /2.60. (10% over 1M) and 1W MetalFilm 27n-10mn, 6.8p.F: 15% 95p; *2%11145; *1%11.50 LIGHT EM DIODES Red: 8 for Sp.Insured postage 8p. THE C.R. 10µF: *5%1140; *2%11.40;11%11.50 Visible clip/data $6p. SUPPLY CO., 127 Chesterfield Road, Sheffield, 150.F. *5%11.60; 12%1240;11%22.70 709 typ'Ira red type, S8 ORN. 11 TANTALUM BEAD CAPACITORS. Values IC GAS OR.Smoke, Butane apour. rtc available 0-22, 0-47,1-0, 2.2, 4.7, 6.11µF at 35V, /1.87. 10µF 25V, 15µF 20V, 22µF 15V, 33µF 10V, ULTRASONIC transducer/remote control. 12. COMPUTER PANELS.91n x TIM long lead 47µF 6V, 100µF 3V-all at 9p each; 6 for 509; Trans. and Comps., ES, 8 Trans., 259 (10P): 'E45, 14 for 11.Special pack 6 off each value (72 16 Trans., 40p (10p); E47, 10 Trans &Op (10). capacitors) 15. IC digital clock NEW 1-TRANSISTORS.13C107, BC 20 pin DIL 12/24 hr.4/ti digit, 211.50, data 99. AMERICAN PANELS.4 for 60p (12p) with data. BCI09. All at 9p each; 6 for 50p; 14 for LIAll Kit 121.Indicators 2149 ea.PCB 11.89, Case 85p. M.C. METERS.2-3in, three a.Worted. 11.06 (24). brand new and marked. Full spec. May PW ELECTRONIC CAR IGNITION KIT, 1647. WIRE ENDED NEON&10- fof40p'Op); 20 for be mixed to qualify for quantity pri s. 75p 18c).Bank of five with 3'407 Driver Trans., POPULAR DIODES. IN914, 7p each; 9 for 45p. 50p; IS for LI. 1N916,9p each; 6 for 50p; 14 for 0 22 WAY STEPPING SWITCH with Reset, Mains LI. 1S44, Sp each;II for 50p; 24 for LI. All QUAD AUDIO fromstereo,matrix IC,2347. Operation,80p (1p). brand new and marked. MAGNETIC CARTRIDGE. diamond 20-20kHz, NEW 46 WAY AS ABOVE, 11.26 (25p). NEW LOW PRICE - 400 mW Znerv. 2419. DUAL IC PREAMP 11.67. FM H i-Fi TUNER Values available 4.7, 5.6, 6-8,7-5, 8.2, 9-1,10, 11, 18. MC13IOP MPX FM decoder, 12.139; KIT 2845. CROUZET GEARED MOTOR.Mains, 15 r.p.in., 12, 13.5, 15V. Tol. ±5% at 5mA. All new and INTEGRATED CIR UITS: with data, 709 T05, 21p; a.cl.w., 75p (151.). marked.Price 10p each; 6 for 50p; 14 for LI. DIL, 28p; 710 and , p; 723, 65p. 5 FIGURE RESETTABLE COUNTER.IR/22V, will Special offer 6 off each voltage (66 zeners) 44.50. 741 OP AMP DILL 28pPhotodetector p. 83p work on 12V, 22 115p). Voltage regulator 1, , to 20V 3 le , RESISTORS. Carbon film 5%. Range from RECEIVER ZN414 Ferranti 3 lea, 21.1 AF SILICON DIODES 850V 11A.10 on Taglioard, 5011 2.20 to 2.2M0 in E I 2 series, i.e. 10, 12, IS, 18, amps: 2W, 61.19; $.5W, 1143; SL40 5. 15p). 22, 27, 33, 39, 47, 56, 68, 82 and their decades. 555 Timer/mono/sortable osc. clock, 95p. I.C. 7400 SERIES ON PANEL(8).10 for 75p (10p). High stability, low noise.All at Ip each; Bp BRATD for 10 of any one value; 709 for 100 of any one COPPER CLAD PAX.PANELS. 51in x 3;in, value.Special development pack-I0 off each TEXTT 6 for 80p (101). FULL RANGE value 2.20 to 2.2M0 (730 resistors) £5. ttiods, POLYSTYRENE CAPACITORS. 125V,1000, to 440V A.C. CAPACITORS. 0-1µF, size 11in X etc.. (159: 0-012, 200 dozen;0.015 to 0.068, 30p dozen (if 1in, 25p; 0.25µF, size 11in X fin, 30p; 0.47 and ordered alone 109). 7413, 29; p.7470/72, Hp: 7473/74/76, 87p.7.41,741 0.5µF, sizeI linX lin, 35p; 1.0µF, size 2inX lie, 1147: 0, 59p; 7492, 67p: 74121, 40p; 7414I 99p: MIXED POLYSTYRENE/S. MICA CAPS. 100 for 45Pi2.0µF, size 2in XI in 75p. DIL SOCKETS, high or low profile, 14 or 16 pi 189. 459. SILICON PLASTIC RECTIFIERS 1.3A- DIL PLUG or IC case, 16 pin, lOnini high, 85P. 71b ASSORTED COMPONENTS, 11.50. Brand new wire -ended D027.100PIV at Op SEMICOIDUCTORS - 21b ASSORTED COMPUTER PANELS, /150. each or 4 for 30p; 400PIV at 9p each or 4 for BC107, 89. -HMOS, Sp. BC109, SP.228055, 409. , 34p; BOOPIV at 14p each or 4 for 50p. AC125/6/7/8. AC127/8, AC187/8, AF117 15p; S.A.E. gin x 4in FOR LISTS. AD181/2, 85p MP 13C147/8/9, 9p: 11C167/8/9, 17O 5p post and packing on all orders below 15. BC177/8/9, 16p;BC182/3/4, 9p;BC212/3/4, 9p; J.W.B. RADIO V. ATTWOOD, DEPT. B6, P.O. BOX 8, BCY70 lap:BD131/2, 889; BEY50n.. 17p; ALRESFORD, HANTS 0C28/35, 49p; 0071, 27p; TIS4311.1T, 29p , 6 75 HAYFIELD ROAD, SALFORD 6, LANCS 129:2N2369. 21p:2N2646, 49p;223,003; 1 2N8055, 40p; 2N3614, 55p: 2N3702/3/4/5/6/7, lap Postage in brackets Mall order only 2N3708/9/10/11, Op. SITUATIONS VACANT PETS: 2N3819. 289; 2N3823, 299; 2N3866 CH 591 ME 0411/2, 1139; ME 4001, 12p; ME 4102, lip. 1111(976370A91, 5p./ ZENERS: BZY88 400mW, 10p. TECHNICAL TRAINING 124001, 4 1N4004, 8p:30V IA Bridge, 239. TRANSFO ERS: mini 12/24V, 21; 6/12V, K. SCR 400V: IA, 28p: 3A, 49p: 4A, 55p: 6A TH., 139y. IN RADIO, TELEVISION CAPACITORS: 23/30V Electrolytic. ICS 10/50/100µF, 15y: 200/300µF, 8p: 1,000oF, 15p. DISC:22pf to 0047µF, 4p; upto 01µF. BP. PRESETS: 0-23W, Op.RESISTORS (W 3%, 1}9. AND ELECTRONIC ENGINEERING CARBVT POTS, 12p ea.Switch +, 12p.Dual. 60p. All DIN plugs, 18p; sockets, Sp.Vero stocked. First-class opportunities in Radio and Electronics await the I C S trained man. Copper Board 12' x 6'; S.R.B.P., 40p.FeC. lit,, Let I C S train YOU for a well -paid post in this expanding field. Eft. Antex irons at R.R.P.Desolder Braid, 18p. I C S courses offer the keen, ambitious man the opportunity to acquire, quickly and .WEATHER STATION barometer, temp., humid., easily, the specialized training so essential to success. Diploma courses in Radio/ FREE CATALOGUE S.A.E.Discount 20+ 10%. TV Engineering and Servicing, Colour TV Servicing, also Electronics, Computers, C.W.O.P. & P. UH & Europe 7p. Overseas 85p. etc.Expert coaching for:

P.O. BOX 29, BRACKNELL, BERKS. C. & G. TELECOMMUNICATION TECHNICIANS' CERTIFICATES.

RADIO AMATEURS' EXAMINATION.

GENERAL RADIOCOMMUNICATIONS CERTIFICATE.

C. & G. RADIO SERVICING THEORY. FIBRE OPTICS Now available, Colour T.V. Servicing. Crofonlightguide type 1610,64 fibresin Examination Students coached until successful. sheath, LI per metre;5 +, 80p;10 +, 70p. RESISTOR PACKS: 300 5%, 60P (15p);200 NEW SELF -BUILD RADIO AND ELECTRONIC COURSES 5% hi -stabs, 60p (12p); 100I & 2%, 60p (Sp); Build your own 5 -valvereceiver,transistorportable,signal generator and 100 metal oxide, 60p (13p).One of each packs (25p).2N3055, 35p; BC107-8-9, Sp or multi -meter.All under expert guidance. iiIIIIIP14 for LI; 709C, 25p; 741C, 25o; 723C, 40p. POST THIS COUPON TODAY and find out how I C S can help YOU in your Ferric Chloride1lb,401901194,100101b, L3.50 (40p). Reed switchunits,contain 31 reeds career.Full details of I C S courses in Radio, Television and Electronics will be mounted round a drum, magnet inside, also sent to you by return mail. plugs,R's,etc., LI(25p), 2 for £1.65 (35p). CASED AMPLIFIERS, 2 x ECC83, EL84, EZ80. MEMBER OF THE ABCC ACCREDITED BY THE CACC 20µV i/p for 2W o/p.7in x 4in 3 0 speaker. Allinpolished oak -faced cabinet with non- standard single motor tape deck.Only 0 (LI). International Correspondence Schools -1 INTERNATIONAL (Dept. D.X.25), lntertext House, Stewarts Road, GREENWELD (PE6) I London SW8 4UJ 24Goodhart Way, W. Wickham, Kent CORRESPONDENCE Tel.01-7772001. Shop at 21 Deptford NAME Brdwy., S.E.8, open Sacs. Tel. 01-692 2009. I Block Capitals Please I Post in brackets, small parts 3p.S.A.E. list. SCHOOLS 1 ADDRESS I I TV LINE OUT -PUT TRANSFORMERS Tidman Mail Order Ltd., 136 Sandycombe A WHOLE WORLD I Road, Richmond, Surrey TW9 2EQ OF KNOWLEDGE I AGE OCCUPATION 01-948 3702, AWAITS YOU! L -

Practical Electronics March 1973 277 S-N-Channel FETs 3819E-El MEN! Full specification devices complete with circuit AT LAST YOU CAN TRANSMIT AND details for building voltmeter,timer, ohm- £50 p. w. meter, etc. FORGET ABOUT LICENCE EXAMINATIONS Send 10p for full list of field effect istors and because this Ministry approved transmitter/receiver can be yours other top quality transistors available at bar- kit does not use R.F. gain prices. Your transmissions will be virtually SECRET since Jobs galore! 144,000 new computer REDHAWK SALES LTD. they won't beheardbyconventionalmeans. Actually it's TWO KITS IN ONE because you get personnel needed by 1977. With 45 Station Road, Gerrards Cross, Bucks. the printed -circuit boards and components for both ourrevolutionary,direct -from - MAIL ORDER ONLY the transmitter AND receiver. You're going to find America, course, you train as a this project REALLY FUN -TO -BUILD with the Computer Operator in only 4 weeks! EASY -TO -FOLLOW instructions. An extremely flexible design with quite an AMAZING' RANGE- Pay prospects? £2500 + p.a. has obvious applications for SCHOOL PROJECTS. After training, our exclusive ap- 100 WATT AMPLIFIER LANGUAGE LABORATORIES, SCOUT CAMPS, pointments bureau-one of the Fully protected, transformerless, 9 transis- etc. world's leaders of its kind-intro- tor circuit.Input 500 mV.Output into GET YOURS! SEND L5-50 NOW (S.A.E. for details) duces you FREE to world-wide 8 ohms. 0.1% distortion. TO: 'BOFFIN PROJECTS' Opportunities.Writeor 'phone Printed circuit board and full instructions. DEPT. KE2010 TODAY, without obligation. 11.45p + 10p P. & P. S.a.e. for listof 4 CUNLIFFE ROAD component bargains. STONELEIGH, EWELL. SURREY London Computer Operators Training Centre EDMUNDS COMPONENTS, 134 NORTH END M83, Oxford House ROAD, LONDON, W14. (Mail order only 9-15 Oxford Street, W.1 Telephone 01-734 2874 RADIO & TELEVISION AERIAL BOOSTERS £2.95, five television valves 45p.50p hargaii MAXI LIGHT 127 The Piazza, Dept. M83 transistor packs, bargain 81 resistor and cap- Piccadilly Plaza, Manchester 1 acitorpacks. UHF -VHF televisions117.50 6 Telephone 061-236 2935 EMERGENCY FLUORESCENT Carr. £150. . for3 leaflets. VELCO LIGHTING FROM YOUR 12v. ELECTRON , ' gE _St.;Ramsbottom RECEIVERS AND COMPONENTS Bury, Lanes. CAR BATTERY OR TWO 6v. LANTERN BATTERIES (continued) LADDERS Suitable for car inspection, boat, caravan, LADDERS, 24fft£11.80, carr. SOp.Leaflet garagemotor -caravanorwheremains Modern Comput rPanels; with TO5 (DeptPEE),HOME SALES LADDER lighting is not available. and plastic transists, 6 for 15p P. & P. CENTRE, Baldwin Road, Stourport, Worcs. .12 ins. 12v. 8 watt, L2.70 each. P. & P. free. P/C Board S/5 51 n in. 10 for SOp Tel. 029-93 2574. Reduction for quantities. + 15p P. & P. Custom-built D.C./A.C. Inverters or D.C.,/ Transformers, 7.5 + 7.5V app. IA, 60p, MISCELLANEOUS D.C. Converters to your specification. p.p.18-0--18V 200mA + 24V 40mA 70p, p.p. ENAMELLED COPPER WIRE W.E.B. ELECTRONICS Potted Transformer, 1000-0-1000V ,a S.W.G. I lb Reel ilb Reel P.O. BOX 4 250mA, Brand New, £6, p.p. 10-14 £1.15 6Sp 15-19 £1.15 6Sp MALVERN . WORCS. WRI4 3HX F.M. Tuner, with RF stage with AGC. 20-24 LIAO 6Sp 3 plugintransistorsneg. earth. Size 25-29 £1.25 75p 2f in 2in Ifin.With circuit,£1.25 , 30-34 £1.30 110p p.p. 35-40 /1.40 Up Cr GearedMotors, 240 volt The above prices cover P. & P. in U.K.Supplied by 10, IS, 30 or 60 rpm, new, £1.40, p.p. INDUSTRIAL SUPPLIES MUSIC Transformers, 52-0-52V IA -I- 22-0-22V 102 Parrswood Rd., Withington, Manchester 10 0.2A, £2, p.p. 34-0-34V 2A -1- 22 -0 -22V - Telephone No. 061-224 3553 If your interestisin SYNTHESISERS and 2A, E2, p.p. FOR ALL your Electronic Component require- other ELECTRONIC MUSIC projects, you need our 1973 catalogue of circuit assemblies 3EGI Scope Tube, new, £1.75, p.p. ments. Send for free list to B.C.-ELECTRONIC and units. Detailed and informative, complete UHF Tuners, transistorised, EI50, p.p. SUPPLIES. 7Regent Road,Huddersfield, with project layouts.Send 20p P.O. to: Veroboard 0.14in x 21 in. 10 for El + DI. 4N R. TAYLOR ELECTRONIC MUSIC DEVICES 15p P. & P. METER REPAIRS.Ammeters,voltmeters, P.O. BOX 42, Chester CHI 2PW 3BPI Scope Tube with base and screen Send to METER (ex equips.), E250, p.p. multi -range meters,etc. REPAIRS, 39ChesholmRoad, London, CONSTRUCTION AIDS. Screws, nuts, spacers Mullard I.F. Module, A.M./F.M. to suit N16 0115. etc., in small quantities. Aluminium panel our tuner, transistorised, LI.2.5, p.p. punchedtospec.orplainsheet supplied RUN YOUR Fascia panels etched aluminium to individua TAPE RECORDER requirements. Printed circuit boards-masters, R.T. SERVICES (Mail order only) OFF negatives and boards, one-off or small numbers A.C. MAINS Send 6p for list. RAMAR CONSTRUCTOR 77 Hayfield Road, Salford 6 Mains unit supplied complete SERVICES, 29 Shelbourne Road,Stratford - and ready to plug into your cis() on -Avon, Warwks. cassette recorder. (State volt- SPECIAL OFFER.100 mixed resistors.Pre- age, model and plug required.)P. & P. 15p ferred Values }W. and ilV 111.25, including Also available for single outputs 6V, 9V,I 2V. AUDIO KINETICS: X-40, X-60, X-100, and postage. 2.2mF 260V WKG 10p each, including ISV, AM. P. & P. 15p. special equipment amplifiers to be released PP. ALEX A 'CDERS, 16 Inverness Street, R.C.S PRODUCTS (RADIO) LTD. soon. For advance informationwrite: London, N.W.1. Tel. 465 5322. (Dept. PAL), 31 Oliver Road, London, 1.17 IMPULSE DYNAMICS ORG., Box 44. AMAZING MINIDRILL

DontPREVARICATE Indispensable for precision drilling,grinding, polishing, * FOR ' - etching, gouging, shaping. -PREVATITAKE PRECISION Precision power forthe enthusiast. Shockproof. Calculators and components will all go Completely portable power up by 100o, buy now and SAVE! Our MODELfrom 44 volt external battery. So much more 1973 catalogue now available WORK scope with MINI -DRILL. at only 15p includes calcula- Super Kit (extra power, in- terchangeable chuck) 01-95 tor and LSI/LED data. P.P. 13P. BYWOOD are always up to date! De Luxe Professional Kit ONLY with17 tools 045 p.p. 23p. - 13YMODD + 6 TOOLS Money Ref. Guarantee. CALCULATORS You may telephone your MERLIN SUPPLY CO order and pay by Access. 181 BURNS ROAD, HEMEL HEMPSTEAD, HERTS. Pa p.lep 0442 62757 f2 Dept. PE3D, Nailsea, Bristol BSI9 2LP

PracticalElectronics March l973 278 ELECTRONICS FANATICS whether beginner or advanced-we offer a range of over 35 SUPER proj- 12 VOLT ects. Have youeverwantedtobuild A FLUORESCENT LIGHTS Elements of Linear MACHINE THAT LEARNS?Or perhaps (as Illustrated) make a TEACHING DEVICE ?Maybe you fancy the idea of an ELECTRONIC Microcircuits FANTASY MACHINE'How about a " Thing" capable ofREPRODUCING ITSELF? Whatever your electronic turn - of -mind, there's just GOT TO BE LOADS T. D. Towers TO INTEREST YOU in the science -fiction - world of BOFFIN. Beat power cuts.Be independent.Ideal GET YOUR CATALOGUE - SEND JUST for caravans, tents, emergency lighting, etc. Gives practical guidance on the selection 15p NOW! Works anywhere where I2visavailable. of commercially available linear micro- Guaranteed for six months. Ready to use at: circuit devices, and on the handling of TO: BOFFIN PROJECTS 12ins. 4 CUNLIFFE ROAD 8 watt £3.60 post paid these sensitive circuits within an assembly. STONELEIGH, EWELL 21ins. 13 watt L460 post paid The emphasis throughout is on applica- tions and on the everyday problems of SURREY SALOP ELECTRONICS, 23 WYLE COP Designs by GERRY BROWN and JOHN SHREWSBURY, SHROPSHIRE.Callers designing electronic equipment, as op- SALMON and presented on TV. welcome.For lists or enquiries, large s.a.e. posed to production technology. V. 1973 116 pp illustrated 0 592 00077 X L280 FIBRE OPTIC SUPPLIERS P.O. BOX 702, LONDON W 106SL FLEXIBLE LIGHT CONDUIT usedto 50 Photoelectric conveylighttoinaccessiblepositionsfor inspection, panel indicators, photo -electric and other applications. Circuits and Systems

FIBROFLEX Type I glass fibre flexible light conduit,I 14rnrn active dia., bundle sheathed in ASTOUNDING new MARK 7 AC POWER P.V.C. Pricespermetre (U.K.postfree): P. S. Smith UNIT with TWO OUTPUTS and LOW 1-4, 70p;5-9, 55p; 10 +, 40p; 25w, Le per BATTERY DRAIN gives the MOST BRILLIANT reel.Epoxyresin plus ferrulesinc.with and BEST EVER INTERNATIONAL PERFOR- orders over 10m. Contains design details of fifty circuits MANCE ofalltime from 12volt CAR CROFON Type1610plasticflexiblelight incorporating photoelectric cells, covering BATTERY. Fantastic for a VAST RANGE of conduit.64filaments. Activedia.I 80mm. Prices per metre:1-4, LI.20;5-9, LI;10+ overone hundredbasicapplications. HUNDREDS of makes and types of 200-240 80p, 25w. LI6 per reel. volt AC and UNIVERSAL AC/DC ELECTRICAL Since requirements varywidely for APPLIANCES and EQUIPMENT within PLASTIC MONOFILAMENT Type FP20, its 0 Srnris dia. unsheathed. 100m, E3,50; 200m, differentapplications, many the scope.Wonderfulfor of FLUORESCENT C6. circuits are intended as a starting point TUBES up to the GIANT 8ft. 125 watt size. Send S.A.E. for full range of products, price list RECHARGES YOUR BATTERY from any and literature.Overseas orders add 50p forfurtherexperimentalthoughall other battery by using any motorist's please. AC MAINS battery charger. Should be circuits are complete and operable as CI4 LI delivery. OUR PRICE (UNUSED described.Details are given of all com- but case marked) ONLY E6.90 LI deliv- ponents so thatalternativesmay be ery. 8 day's appro. against cash. C.O.D. easily selected if necessary. with pleasure. (Send SAE for details) DeptPE, BROADWAY DISTRIBUTORS, The EX COMPUTER PRINTED CIRCUIT 1972 88 pages illustrated GeneratorCentre,House ofTime, 273 PANELS Cased 0 592 02817 8£2.30 2 - 4in packedwith semiconductors and Limp 0 592 02879 8L130 Broadway, Rossall, Fleetwood, Lancs. top quality resistors, capacitors, diodes, etc. Our price10 boards 50p (8p).With a guaranteedmin.of35 transistors --data Build the Mullard C.C.'T.V. Camera included. Kits are now available with comp- SPECIAL BARGAIN PACK 110 Thyristor rehensive construction manual 25 boards for LI (25p). (also available separately at 65p.) ELECTROLYTICS Projects SEND 857'5A.E.FOR DETAILS TO I0,000u 75V, 33,0008 40V, 4f 2iin dia., 25,0007[25V,20,000,s30V,8,00071 55V, CROFTON ELECTRONICS 4} 3india.SOp (I2p). 15,000u15V, using SCRs and TRIACS 15/17 Cambridge Road, Kingston- 41 2in dia. 20p (10p).2,0007[ 25V wire on -Thames, Surrey KT1 3 NG ended, 3 lindia.I5p (5p)or 12 for LI-SO (I5p). R. M. Marston 250 MIXED CAPACITORS 60p (8p) PSYCHEDELIC MINI -STROBE 250 MIXED RESISTORS 60p (8p) Describes many projects making use of A veryPOWERFUL, POCKET -SIZED 3A STUD RECTIFIERS, 100 p.i.v. STROBE -LIGHT that is SELF-CONTAINED 4 for SOp (Sp) thyristordevicescapableof handling and you can take anywhere. Go to parties ASSORTED RELAYS 8 for El (25p) mains voltages that can control currents and reallyBRAIN -FREEZE themwith DAZZLING PSYCHEDELIC EFFECTS and SUB -MIN. CO -A X. PLUGS & SKTS. of tens or hundreds of amperes. STOP -MOTION FLASHES.Boffin's new 4 pairs 50p (Sp) The projects described, which range MINI -STROBEkitconstitutes a fully MINIATURE GLASS N EONS solid-stateelectronicdevicewhich is from simple electronic alarms to highly COMPLETE with FUTURISTIC case 12 for SOp (5p) reflectorunit. printed -circuit board. REED RELAYS, MIXED 10 for SOp (5p) sophisticated self-regulating electric - electronics, andsource-lamp-theonly MICRO SWITCHES, MIXED heater power controllers, should beof extrais a battery which you can buy 8 for SCIp (8p) locally.The whole thing can beeasily equal interest to the electronics amateur, built in a few hours. PAPST EXTRACTOR/BLOWER FANS A veritable FLICKERING FASCINATOR! 100cfm 41 4} 2in L3.50 (28p) to the student of electronics and to the Adjustable flash -rate. QUARTZ HALOGEN BULBS professional engineer. GET ONE (or two) NOW and BEGIN I 2V 55W STEALING THE THUNDER at DISCOS 50p (Sp) 1972 146 pp illustrated and PARTIES with your own POCKET - Postage and package for each item shown LIGHTNING! in brackets. Cased 0 592 00073 7 £2.40 SEND (195 for YOUR MINI -STROBE, to: Limp 0 592 00074 5£1.40 Boffin Projects KEYTRONICS 4 Cunliffe Rd., Stoneleigh, Ewell, Surrey (Mail Order only) CLEARING LABORATORY, scopes, V.T.V.M's, The Butterworth Group V.O.M's, H.N. recorders, transcription turn- 44 EARLS COURT ROAD 88 KIngsway, London WC2B 6AB tables. electronic festmeters, calibration units. LONDON W8 l'.S.IT.'s, pulse generators. D.C. null - Trade counter: 4-5 Bell Yard, WC2 potentiometers,bridges. spectrum analysers. 01-478 8499 voltageregulators,sig-gens, 1' relays, components, etc.Lower Heeding :231l.

Prattical Electronics March 1973 279 BUILD A PROFESSIONAL SYNTHESISER

using Dewtron (Regd. Trademark) PROFESSIONAL MODULES CASH SAVINGS by buying modules and parts in bulk! All modules are available separately: RingModulator RM2,£8. Voltage -controlled You too can build a professional synthesiser like the Oscillator VC01, £10.50, giving sawtooth and square - oneillustratedusingtheprofessionally -proven waveoutputs. Envelopeshapers, ES1, self - range of Dewtron modules. NEW MODUMATRIX triggeredor ES2 keyboard -triggered,either type modular matrix system replaces clumsy patching. £13. White noise type WN1, £7.Voltage -con- 3 and 4 octave keyboards and contacts. trolledamplifier VCA1, £10.Voltage -controlled selective amplifier (filter for waa-waa, etc.) SA1, £12. VCO-2 STABLE, PRECISION V/C OSCIL- Voltage -controlled Phase PH1, £17.Automatic LATOR gives SINE, TRIANGULAR AND Announcement Fader module for fading of music SQUAREWAVE outputs, 1 volt/octavevoltage by microphone announcement, AF1, £9.etc., etc. control.£22 each or £25 each 2 or more matched. ALL MODULES AREBUILT, TESTED AND SHE -1 SAMPLE, HOLD AND ENVELOPE SEALED FOR LONG LIFE. Simplyconnect MODULE gives variable attack,sustain, touch - coloured wire connections as per easy instructions, sensitive playing when used with VCO-2 signals. build cabinet and wire in controls and patchboard £15. connections!Joystick controls £4.50. REVERB Modules (except VCO-1) guaranteed two years. Module and spring unit £15. With over 7 years' unblemished reputation in these pages, Dewtron continues to lead in new technical developments in electronic sound effects!Ask any of our customers.See our products in the music stores, too.Suppliers of special equipment to a leading group. Our modules are used in professional equipment by other manufacturers and in our own built synthesisers, e.g. "Gipsy" G.I. £330. Send 15n for full catalogue of our famous musical effects. D.E.W. LTD. 254 Ringwood Road, FERNDOWN, Dorset BH22 9AR FERRANTI MICROCIRCUIT RADIO asky's ZN414 Alid10:11r01111CS SAS SEEN Only X1.20. ) SONTV ! ..I WITH FREE DATA Catalogue1973 Post 8 Packing So WE ARE SPECIALISTSIN FERRANTI. SEMI - CONDUCTORS The great1973editionof Lasky's famousAudio-Tronicscatalogueis available - FREEon request.The48 newspapersizepages- manyinfull colour - are BFS59 I 1p ZTX3I0 Bp ZTX504 39p ZS170 9p packedwith1,000sof itemsfrom thelargeststocksin GreatBritain of every- BFS60 18p ZTX3 I I 9p ZTX5I0 15p ZSI71 1 I p thing fortheRadio andHi-Fi enthusiast,Electronicshobbyist,Serviceman and BFS61 18p ZTX3 12 9p ZTX530 19p ZS172 14p CommunicationsHam.Over half thepagesaredevotedexclusivelyto every BFS96 13p ZTX3I3 10p ZTX53 I 20p ZSI74 15p aspectof Hi-Fi(includingLasky's budgetStereoSystemsandPackage Deals), BFS97 21p ZTX3I4 II p ZTX550 15p ZSI76 2Ip Tape recordingandAudioAccessories.Seethegreat newLasky'sCredit Plan BFS98 189 ZTX320 28p ZTX551 15p Z5178 34p Scheme- enablingyouto buy your idealchoiceof equipmenton easy terms. ZTX107 8p ZTX330 3p 2N3055 65p ZS270 10p ZTX108 7p ZTX33 I 4p ZS271 14p ZTX109 10p ZTX382 19 DIODES ZS272 16p Send thiscouponwith 15pforpost and ZTX2I 2 12p ZTX383 1p ZSI20 7p ZS274 17p ZTX2I 3 12p ZTX384 6p ZSI21 9p ZS276 23p inclusionon ourregularmailinglist. IrJ1 7_ TX2I4 13p ZTX450 Sp ZSI 22 1 1p ZS278 33p ZTX300 10 ZTX451 Sp ZSI 23 14p ZTX301 lip ZTX500 Op ZSI 24 16p ZENERS ZTX302 15p ZTX501 1p ZSI40 22p KS030A to

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280 PracticalElectronics March1972 This FREE76 page book canpit you on theroad tosuccess Over ISOways through aBIET Home StudyCourse,Clioose to engineera yoursubject now

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Published approximate!) on the lath ot month hl 1.t.1 Magaelic., Fl.!a .. . Puraludoll Andover. Haute. Sole Agent, for Australia and New Zealatvl E.C.4. Printed England by Chapel KIN., Press. Gordon A: i ! sonlh afrii a ('ends..!NrWN Agency Hhodasi East Africa-Stall...4.y and Office ffupplisa Ltd. and ZambiaKingston, Ltd. : Stihseript ion Irate (including le (0.1,1 1 P!.r ona }ear to any part of (ha ,.,,rid Practical Electronics is sold subject. to the following conditions, namely, thatitshall not, oithout the written consent of the Publishers ids(given,I..1,1). resold, 11704 env otherwise disposed of by way of Trade at more than the. recommended selling price shoo ii on the cover, and that it shall not he mutilated condition or in any unauthorised cover by oay lent, resold!ir hired out or otherwise disposed(ifin Trado, or affixed to or ilq part of any publication or advertising, literary or pictorial neater N4 ha cr. U.K's LARGEST ELECTRONICS CENTRES! eeetP s, * HENRY'S RADIO LTD.EDGWARE ROAD, LON DON, W.2. W 404-406 ELECTRONIC COMPONENTS & EQUIPMENT 01 402 8381 No 354-356 HIGH FIDELITY & TAPE EQUIPMENT 01-402 58'14/4736 ! 309 PA - DISCO - LIGHTING HIGH POWER SOUND 01-/23 6963 303 BARGAIN STORE SPECIAL OFFERS All Mail to: 303. Edgware Rd.. London, W2 1 B W OPEN I' MEN S.WITHIN 200 YARDS. CALL IN AND SEE FOR YOURSELF. (As featured in "Practical Wireless" RECORD DECKS May to August 1972) CHASSIS (Post SOp) SP25/3, 110.25 HT70, £14.50 MP60, £9.95 MP610, 11245 AP76, 11745 GL75, resso PLINTH/COVERS (State Model) TEXAN SP25/MP60/610 1330 (Post 40p) AP76 f.4.50(Post 40p) CART/PLINTH/COVER 20 + 20 WATT INTEGRATED (Post 70P) (HL) MP60/G800H/PC 118.50 I.C. STEREO AMPLIFIER MP610/SCSMD/TPD2/PC g19.95 AP76/M756SM/PC £3250 * FREE TEAK CASE withcomplete kits ! AP96/M756SM/PC 139.95 FEATURES: New slim design with 6 ICs, IC (HL) AP76/G800/PC £2895 sockets, 10 silicon transistors, 4 rectifiers, 2 zeners. (HL) SP25/G800H/PC 11895 Special Gardners low fieldslimline transformer. SPECIAL SLIM DESIGN HT70/G800/7 P DI/PC 04.50 Fibre glass PC panel.Complete chassis work. KIT PRICE WITH (HL) 2025/9TAHCD/PC L13.95 HIGH QUALITY & STABILITY ARE PREDOMINATE FEATURES MP60/SC5MD/PC L17.25 -DEVELOPED BY TEXAS ENGINEERS FOR PERFORMANCE, SILVER TRIM (HL) GL75/G800E/PC 141 95 (HL) GL75/G800/PC 08.95 RELIABILITY AND EASE OF CONSTRUCTION. Overall eh aaa i a vise FACILITIES:On/off switch indicator, headphone socket, E28.50 :Spa P 141 is. z gin.: 2 in. high separate treble, bass,volume and balance controls, scratch and ULTRASONIC rumble filters, mono/stereo switch, Input selector: Mag. P.U., COMPLETE WITH FREE TEAK CABINET TRANSDUCERS Radio Tuner, Aux. Can be altered for Mic, Tape, Tape head etc. Operate at 40kc/s up to100 yds. Ideal remote switching and (Parts list Ref. 20 on request). Constructional Details Ref. No. Designer approved kits distributed by Henry's! signalling. Complete with data 21.30p. and circuits. LOW COST HI-FI SPEAKERS TEST EQUIPMENT!ujetAion PRICE PER PAIR 1.5.90. Post 10p. E.M.I. Size 134in x 81 in and Ceramic Magnet SE2SOB Pocket Pencil Signal Injector, 11.90 MARRIOT TAPE HEADS SE500 Pocket Pencil Signal Tracer, 11.50 4 TRACK MONO TYPE 150 6 watt, 3, 8 or 15 THL33D Robust 2 K Volt, 1455; with case 1495 or 2 TRACK STEREO ohms a.20.Post 22p. TEI5 Grid Dip Meter 440 KHz-280 MHz, 113.45 "17" High Impedance 1200 TYPE 150TC Twin cone ver- 500 30 K/Volt Multimeter. L925; "18 " Med. Impedance 12.00 sion /2.75.Post 22p. with leather case, L10.50 " 36" Med.-Low Imp. 13.50 TYPE 450 10 watt with twin 20014;20 K/Volt Multimeter, /4.20; with case 14.95 Erase Heads for above 75p tweeters and crossover, 3, 8 AFI05 50K/V Multimeter, 0.50; with case, £9.50 "63" 2 track mono - High or 15 ohms. 0.85. Post 25p. U434I AC/DC Multimeter withtransistor Impedance L1.75 TYPE 350 20 watt with tweeter tester with steel case, /10.50 "43 " Erase Head for above 75p and crossover, 8 and 15 ohms. TE20D RF Generator 120KHz-500MHz, L15.95.Carr. 3Sp £7.70.Post 28p. TE22D Audio Generator 20Hz-200KHz, 11750.Carr. 35p POWER INTEGRATED Carr. SOp POLISHED CABINETS 150, 150TC, 450 L4.60.Post 30o. CI -5 Sin Pulse Scope 10Hz-I0MHz, 139.00. CIRCUITS ASSEMBLED IN POLISHED CABINETS (8 OHM) TE65 Valve Voltmeter 28 ranges, 117.50.Carr. 40p Plessey SL403D-3 watt with ALL NOMBREX MODELS IN STOCK 8 -page data, layouts and circuits SERIES 8 (Assembled 450) per pair L18.95.Post 70p. g1.50. P.C. Board 60p; Heat Sink BUILD THIS VHF FM TUNER 14p. Sinclair IC12-6 watt with M L3 MW i LW 5 TRANSISTORS 300kc/s BAND- data and circuits [1.110. WIDTH PRINTED CIRCUIT, HIGH TH9013P-20 watt Power TUNER TO BUILD FIDELITY REPRODUCTION. Amp Module L4.57. MONO AND STEREO. A popular TH9014P-1C Preamplifier L1.50. Uses Mullard Module. VHF FM Tunerforqualityand Data/Circuits ( No. 42) Slow motion tuning.Built-in reception ofmono andstereo. for above 10p. There isnodoubtaboutit - battery.Ferriteaerial. Overall size 7in x VHF FM gives the REAL sound. Post15p. 7 SEG & NIXIE TUBES x 34in. TOTAL COST TO BUILD L4.85. All parts sold separately. (PostISpper I to 6) All parts sold separately -Leaflet No. 6. Free Leaflet No. 3 & 7.TOTAL /6.97, p.p. 20p. GN6 0-9 side Decoder Kit /5.97.Tuning meter unit 1145. XN3, XNI 3, "BANDSPREAD" PORTABLE TO BUILD Mains unit (optional) Model P5900 L2.47.Post 20p. view with data, 85p. Mains unit for Tuner and Decoder PS6/12 13.25. Post 20p. GNP -7, GNP -8 0-9 side view Printedcircuitalltransistordesign with decimal points and data, using Mullard RF/IF Module. Medium 95p. and Long Wave bands plus Medium PA -DISCO -LIGHTING 30I5F 7 seg. a each, L7 per 4 Wave Bandspread for extra selectivity. UK's Largest Range -Write et ersi".41,1 iNa with data. 600mW push-pulloutput, fibreglass phone or call in.Details and , - ee 12 and 24 hour clock circuits. PVC covered cabinet, car aerial. demonstrations on request. Ref. No. 31 ISp. Attractive appearance and performance. DJ3OL 3 Channel sound to TOTAL COST TO BUILD £7.98, p.p. light unit, 3kW. L29.75 32p (Batt. 22p).All parts sold separately FIBRE OPTICS MINIATURE AMPLIFIER DJ4OL 3 Channel Mic (Built-in) to light, 5 transistor. 300mW o/p. -Leaflet No. 2. 3kW. 13845 LIGHTING MICS PRO- Fitted volume and sensitivity D.170S 70 watt Disco amp/mixer, 149.95 EFFECTS £1.75 DISCOAMP 100wattDiscoamp/ JECTORS SPOTS control 9 volt operated. each, p.p. 15p. CATALOGUE mixer, £66.50 DIMMERS Fully detailed and D.11055 30 watt Disco amp/mixer, 02.75 STANDS* MIXERS illustrated covering every Anti -Feedback Quality Mic., /11.50 SPEAKERS QUALITY SLIDER CONTROLS aspect of Electronics - Everything for 60mm stroke singles and DJ500 50 watt PA amplifier, 14400 ganged. Complete with knobs. plus data, circuits and Group 300 150 watt rms Group Valve PA - Disco - 9, information. amplifier, 0600 Lighting. sko,10kfl,25k0, 100kO, 10,000 Stock lines at Portablediscos-details on FREE Stock List 250k:3, sookil .I meg. Log and Special Low Prices and Credit terms for callers Ref. No. 113. Lin.40p each,I Okfl.251c0, Fully Guaranteed. 50kfl ,100kfl, 250k fl, Log and SI NCLAIR PROJECT 60 MODULES Lin. ganged. 60p each. PRICE 55p Paid (40p FOR CALLERS) -SAVE POUNDS HI-FI AND TAPE EQUIPMENT PLUS! FIVE Z30 0.57_Z50 /4.37 Acknowledged STEREO 60 1797 PZ5 £3.97 10p VOUCHERS as U.K 's PZ6 L6.37 PZ8 /447. L Stockist Send to this address - Transformer for PZ8 12.95, Henry's Radio Ltd. (Dept. PACKAGE DEALS Post 25p with Lowest PE), 3 Albemarle Way, ActiveFilterUnit £4.45. 2 x Z30, Stereo 60, PZ5 £15.95 Prices Plus 12 London, E.C.I-for Stereo FM Tuner11615.2 x Z30, Stereo 60, PZ6 /1800 catalogue by post only. 2 x ZSO, Stereo 60, PZ8 £20.25 Months All other mail and callers IC12 1140 Q16's LIS pair.Transformer for PZ8 12.95 Guarantee. to "303", see above. Post, etc. 20p per item. PROJECT 605 KIT 119.95 Write or tall SCR's - for FREE 16 MORE OF EVERYTHING ALWAYS AT HENRY'S TRFEttwes _ IC., - page lists LATEST BROCIIIMCkerNo. 36 on All the parts you need plus Data and Circuits. Get a Catalogue -it's all in there! (Ref. No. 17) Pricer subject to chance without notice. E. & O.E. request or see our earlier page. 309-354-356-404-406 Open 6 days a week 9am - 6pm (303 closed Thurs.) All Stores open all day Saturday. H MORE OF EVERYTHING AT THE RIGHT PRICE ALWAYS AT HENRY'S H