Radio Schools in Honduras

APRIL197735p

Aboweeftioi Radio schools in Honduras

Australia $A1.20 Canada 51.50 Denmark Kr. 11.00 Finland Fmk. 6.50 Germany Dm. 4,50 Greece Dr. 45.00 Holland Df1. 4.50 Italy L. 900 Malaysia M$3.25 New Zealand SNS1.40 Norway Kr.10.00 incl. moms Portugal Esc. 40.00 South Africa R. 1 10 'rain Ptas. 80.00 eden Kr. 6.90 incl. moms 51.50

www.americanradiohistory.com wireless world Electronics, Television, Radio, Audio

APRIL 1977 Vol 83 No 1496

Contents 35 Time, gentlemen, please Front cover, showing the 36 NRDC surround -sound system by M. A. Gerzon medium wave aerial at Radio - lándia, Comayagua, Honduras, 39 News introduces the article on edu- 40 Characteristics and load lines -5 by S. W. Amos cation by radio in that country 44 Wireless World amateur radio station (page 57). 45 Sensitive metal detector by D. E. O'N. Waddington Photographer Paul Brierley 48 H.F. predictions 53 New of the month IN OUR NEXT ISSUE Bullock's boardroom and the engineer Britain pioneered the integrated circuit Electrolytic capacitor tester. Vmos devices "middle of this year" Enables the value of an electro- 57 Education by radio in Honduras by M. K. Bates lytic capacitor to be measured 60 Literature received. 100 years ago automatically and the result displayed directly by meter. 61 Circuit ideas Leakage is also indicated. Simple noise generator Variable band -pass filter Ripple eliminator Two -stage linear amplifier. A 65 Viewdata -3 by S. Fedida discussion of the design of 70 World of amateur radio solid -state 50W and 300W linear amplifiers for the h.f. band 73 Electronic rhythm unit -2 by A. Battaiotto and G. Ronzi (1 .6- 30MHz). 76 Letters to the editor The Warden Report Current dumping amplifier Radio in the '80s, a look Advanced pre -amplifier design forward to sound receiver design 79 Broadcast stereo coder by T. Brook and the ideal set of the future by 83 Power semiconductors by M. R. Sagin the BBC's chief engineer of radio 93 New products broadcasting. 96 Just for the record by A. D. Foster APPOINTMENTS VACANT INDEX TO ADVERTISERS

ISSN 0043 6062 Current issue price 35p, back issues (if available) 50p, at Retail and Trade Counter, Paris Garden, London SEI. By post, current issue 55p, back issues (if available) 50p, order and payment to Room 1,1, Dorset House, London SEI 9LU. Editorial & Advertising offices: Dorset House. Stamford Street. London SEI 9LU. Telephones: Editorial 01 261 8620: Advertising 01 261 8339. Telegrams /Telex. Wiworld Bisnespres 25137 London. Cables. " Ethaworld. London SEI. Subscription rates: 1 E7.00 year: UK ana overseas ($l8.20 USA and Canada). Student rate: 1 year. l3.50 UK and overseas ($9.10 USA and Canada). ibpa ABC Distribution: 40 Bowling Green Lane. London EC I R ONE. Telephone 01 837 3636. Subscriptions: Oakfield House. Perrymount Rd, Haywards Heath, Sussex RH I6 3DH. Telephone 0444 59188. Subscribers are requested to notify a change of address. C 1.P.C. Business Press Ltd, 1977_'

www.americanradiohistory.com 34 Wireless World, April 1977 f r 1 Ili MNIIIIIIIM>« ANIIWNINI710/4141/701r 11O11 mow AM 1 4/.111110li 1W1\11111l4110l1.If11111f 1A1MA11[1/J\Il11/1I`1y 1NINIII:/i11\!\\st'I.1!\dill ram r/ia isi I111=r : oZ/111..'

yW117 WWM NMAMR MIMI 1r

10N1

I r'I ...., 7f r11w1111111111r...111JrM 1 81. .Ya ' 1 t airy J /111w lAt as JA M.u..amY..,r u....rr J ítá1'ie\ äs0 s+i 1= -_ v,¡!r 011111... .410'%11.110in L4ulf= i

? 1"S iti ' 1_. ri w1. - 01l:-+Ir- \-_rYSoru_ 1r-+. 1V1Ulls\t1ti ft `Ìl1iÁ1\151.I!'11f7 I r i t >'...... _± - t\/!!J 1r1MfM1J1 7Ñ1rr17f...UV_.i i S AwSJ =MON I_r t/ls1 7i\! Ji/ris /f'A IU.11o!/7t1AI% -..!'911 ft7 t:et' ,tal WPM tlftl SA1 -t'\/.W'a!,r V11Y Jt (¡' Jr i rii- IìIA` f 7 ..JAa.ll5N/11\ The Test of Time

Critics were most generous in their praise when the Shure V -15 Type III pickup cartridge was introduced. The ultimate test, however. has been time. The original engineering innovations, the uniquely uniform quality and consistent performance reliability of the V -15 Type Ill have made it THE classic choice as the source of sound for the finest music systems, both here and abroad. Consider making the relatively modest investment of a new cartridge to upgrade the performance of your entire hi -fi system. Why not ask Shure Electronics Na' Limited for their recommendation? Addre..s Shure Electronics Limited Eccleston Road. Maidstone ME15 6AU Telephone: Maidstone (0622) 59881 d > best

The original manuscript by J. S. Bach shown is repro- by of The British Library. HLJRE duced kind permission j WW -010 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 35 wireless world

Time, gentlemen. Please!

Editor: TOM IVALL, M.I.E.R.E. When this issue of Wireless World appears on the news stands the deadline for submissions to the Home Office on British policy on frequency reallocations for the 1979 WARC will be only six weeks away. (See News of the Month, March Deputy Editor: p.37). Yet a few months ago even this much PHILIP DARRINGTON consultation seemed out of reach. Phone 01 -261 8435 The Home Office is to be congratulated on reversing its policy of selective consultation and giving the public a chance to have their say. It could be argued, indeed, that the process might have begun much earlier had the electronics Technical Editor. GEOFFREY SHORTER, B.Sc. industry and its representatives been less acquiescent in the Home Office's Phone 01-261 8443 reluctance to encourage public intrusion. Even though the discussions to which the discreet trusties we referred to in December found they had an exclusive Assistant Editors: entrée were on matters of public concern far beyond their immediate interests, MIKE SAGIN they made, at first, no effort to press for a programme that might dilute their own Phone 01-261 8429 RAY ASHMORE, B.Sc., G8KYY bargaining strength. Phone 01 -261 8043 But it is for the electronics industry, singly and collectively, to put its own JOHN DWYER Phone 01- 261 8620 house in order. The immediate need is to make sure that the 1979 package is a fair reflection of the views of all those with an interest in the allocation of frequencies. The Home Secretary's statement is only a beginning. Indeed it Production: a I). R. BRAY contains surprising admission of the inadequacy of what he has craftily called "the preliminary phase" of the work for the conference: although, he says, a substantial measure of consultation with users and manufacturers has already Advertisement Controller. taken place, during the next phase "those known to have an interest will be ROWELL G. BENTON specifically invited to comment." One wonders how "substantial" the measure of consultation during the preliminary phase could have been. Advertisements: One hopes, too, that equal weight will be given to the public's views as to-those PHILIP NOSSEL (Manager) invited." This be if is Phone 01- 261 8622 "specifically can only the case the public as well informed as those "known to have an interest," yet we have not received any details of the Home Office proposals for disseminating the contents of the Warden reports and LEO KEMBERY any others relevant to the WARC. If the "wider programme of consultation" is to Phone 01 -261 8515 be anything more than an empty political gesture these reports must be made public.

OWEN BAILEY (Classified Advertisements) The ten days following the publication of the next issue of Wireless World will Phone 01 -261 8508 or 01- 261 8423 not give enough time to read the available material, to consult colleagues, and to draft a considered proposal. The consultation period should be extended, just as the Annan committee extended theirs. An extension to the end of the year would JOHN GIBBON (Mahe -up and copy) Phone 01- 261 8353 give officials a clear year to collate and prepare the British case. Is that so much to ask?

Publishing Director: GORDON HENDERSON

www.americanradiohistory.com 36 Wireless World, April 1977 NRDC surround -sound system

Michael Gerzon reveals the thinking behind system 45J by Michael Gerzon, M.A Mathematical Institute, Oxford

This article gives a feel for how it has are in -phase or out -of -phase with the (divided by the pressure amplitude) proved possible to evaluate the whole pressure signal components are used by should be one for real -world sounds, range of possible methods of encod- the ears. In practice the 90° -phase and so decoders should be designed ing and decoding surround -sound components of figure -of -eight pick -up with a pressure -to- velocity ratio assur- based on fundamental psychoacous- do affect localization quality toward the ing this requirement for all reproduced tic principles. Although the full top end of this low frequency range, and sound directions at low frequencies, in development was highly mathemati- produce an effect called "phasiness." addition to ensuring correct Makita cal, the basic principles underlying In practice, the head may rotate, so localization. It is an incorrect velocity - the Ambisonic or NRDC 45J system' that the forward -pointing figure -of- vector length that makes the side image of surround -sound are described eight pick -up of sound information is reproduction so poor in conventional without mathematics, this new sys- also used to determine sound direction. "discrete" quadraphonics. tem being the best possible according The relative intensity of in -phase If there is too high a phasiness, it is to the methods used. figure -of -eight signals in the forward clear that this can be reduced for a given Up to now, surround sound system and sideways direction defines a vector decoder design by subtracting from the design has to a considerable degree pointing in the apparent sound direc- figure -of -eight signals a suitable been based on guesswork as to what tion according to Makita's theory and is amount of 90° phase- shifted pressure signals fed to an array of loudspeakers susceptible to calculation as described in signal. In practice, the amount of will produce a "desirable" directional reference 4. The length of this vector unwanted 90 °- shifted figure -of -eight affect. As an exhaustive experimental information varies with sound direc- evaluation of the directional effect of tion, so that phasiness compensation to arbitrary crosstalk patterns for even reduce phasiness in one direction will just a square speaker array involves tend to increase it in the opposite consideration of a six -parameter family direction. Nevertheless, it is possible to of crosstalk configurations, and as even (a) use this technique to give a subjectivity small variations of the crosstalk pattern optimized phasiness, as shown in Fig. 2. can produce significant alterations of The block diagram of Fig. 2 is a directional effect, it would be necessary psychoacoustically optimized decoder to do experiments for about 10' different consisting of a phase- amplitude matrix crosstalk patterns before one could say producing pressure, forward and that a system could be optimized purely sideways velocity and 90° phase- shifted on the basis of experimental data. This pressure signals from the input chan- is impracticable. nels; the design of the phase -amplitude A very general theoretical framework matrix depends on the encoding system. has been developed' to assist in maxi- mizing the information that can be Fig 2: Block diagram of decoder deduced from limited experimental satisfying the main psychoacoustic tests on human directional psycho - requirements. Shelf filters are all -pass acoustics. Certain aspects only of this Fig 1: Pressure and velocity types designed to have identical phase psychoacoustic framework are dis- (figure -of- eight) pick -up characteristics responses, and make the decoding cussed in this article. of the sum and difference of the inputs matrix varying frequency according to At low frequencies, the information to the two ears of a listener at low the frequency- dependent properties of reaching the brain consists of the sum of frequencies. human hearing. ears, i.e. an the inputs to the two Pressure omnidirectional or "pressure" sound Shelf filter I pick-up and the difference of the inputs w Speaker distance to the two ears, i.e. a sideways -pointing compensation -up, C figure -of -eight or "velocity" pick E Forward E ol Fig. 1. Most low frequency ( <700Hz) II Amplitude o velocity X theories of hearing assume that only the a matrix

interaural phase is used to determine Q E Sideways direction, which is equivalent to saying e ) II that only those components of the velocity Y sideways figure -of -eight pick -up that i T , System 45J is the subject of a UK- section AES r (optional) 90° shifted held on 12 April at the IEE, savoy meeting to be I Phasiness Speaker Place, 19.00h. Title is "Hearing and sur- pressure compensation layout round- sound," by P. B. Fellgett, M. Gerzon and T. -jW compensation Takagi.

www.americanradiohistory.com Wireless World, April 1977 37 The shelf filters are frequency- depen- Left parameters of motion decoders that optimize dent gains that permit adjustment of the reproduced psychoacoustics of the the relative Right velocity and pressure gains motion (4 directional effect for every sound so that at low frequencies the velocity - direction. vector length is correct, and at higher The requirements on surround -sound frequencies other psychoacoustic (a) performance of such systems include requirements, described later, are satis- the following. fied. The "distance compensation" is Right The two baseband stereo signals L high -pass RC filtering of velocity, motion and R must be decodable for surround typically - 3dB at 20Hz, to compensate directional reproduction in a way the bass boost of the velocity signals i phase satisfying all the basic psychoacoustic produced at the listener by the curved criteria discussed earlier. sound field (caused by finite loud- It must be possible to supplement the speaker distance). It is mainly the phase baseband with a third signal capable of response of this filter that is being decoded with improved direc- psychoacoustically important. The out- Left Right tional effect. A fourth channel is not put amplitude matrix produces speaker only only required as it can only degrade direc- feed signals, dependent on the speaker tional reproduction. layout used, that create correct pres- To achieve high quality from carrier sure and velocity at a central listening (b) discs, which have certain inherent position. Anti phase theoretical limitations determinable by At higher frequencies, about 700 to information Fig 3: Angle O of stereo stylus motion standard theoretic analy- 5kHz, a different class of theories of in record groove corresponds to sis, it is necessary to bandlimit the hearing take over. In these theories an angle 20 on a circle representing subcarriers to a few kHz. localization is via signal energy, and is possible stereo positions. It is required that satisfactory determined by drawing a vector point- decoders be designable for the case ing to each speaker having length equal when the third channel is bandlimited, to the energy of a sound from that Left not only in directional effect, but also in speaker. The sum of these vectors is a flat reproduced frequency response in vector pointing in the intended sound all encoded directions. The directional direction, which direction is the "energy effect requirement for such "21/2 chan- vector localization." The length of this nel" use means that, as the third vector, divided by total energy (energy channel is attenuated the Makita (and vector magnitude) is 1 for real -world hence energy vector) localization of a sounds, and should be as large as three -channel decoder should remain possible in decodecs for good localiza- unaltered. tion. Right Within these above constraints, the There is a transitional frequency Fig 4: Circle point A goes to point B on two channel decoding should be capa- band, 250 to 1.5kHz over which both ble simultaneously of low phasiness for sphere by a rotation by angle O equal to classes of theories may apply, and it is the phase lead on the left channel. front -stage sounds, good localization at important that decoders should give the left and right side positions, and both correct pressure /velocity and with a uniform reproduction of energy localizations as far as possible ambience information around the over this transitional range. This is listener on "natural" ambient record- ensured by designing decoders to give ings. Makita and energy vector localizations A way of describing the two -channel that are identical at all frequencies; this baseband encoding is the "energy may be ensured for many types of sphere" (ref. 2) which represents the speaker layout (rectangle, hexagon, relative phase and amplitude gain of etc.) by a suitable design of output each sound on the two channels as a matrix. The shelf filters in Fig. 2 are then point on a sphere. A sound recorded on chosen to give optimum velocity mag- the two groove walls of a stereo disc nitude at low frequencies and optimum (Fig. 3), without the use of phase energy vector magnitude at high fre- shifters is represented by a point A on quencies. Note that this design proce- the horizontal circle of this sphere, at an dure involves designing not only opti- angle from the right -most point of the mum low and high frequency decoding circle twice as big as the angle made by matrices, but an optimal variation of the Fig 5: Typical stylus motions (for sine the stylus motion from the right -chan- matrix over the transition frequency wave signals) and left and right nel -only direction of stylus motion. In. range. channels gains corresponding to this way all in -phase and out -of -phase One result that emerges from this various points on the energy sphere. lines of stylus motion are mapped to theory is a remarkable mathematical points around a circle. If the left channel theorem to the effect that the optimal is now made to phase -lead one right accuracy of reproduction of images in then to find the best encoding system, channel by a phase angle .1), then the non -speaker directions via a rectangle i.e.. the one whose optimized decoder point B on the sphere representing the of speakers can be obtained only if the gives better results than for all other method of encoding is also obtained four speakers are fed with not more encoding systems. from A by rotating the circle about its than three information channels; it may It is possible to classify mathemati- left /right axis by an angle as shown in +RB be shown that -L5 +LF -RF should cally all systems with not more than Fig. 4. Stylus motions and left and right always be zero for best results. Experi- three channels that are capable of channel phases and gains correspond- ment confirms the theory. satisfying the Makita, energy vector ing to various points on the energy Given that we have a means of and velocity magnitude requirements sphere are shown in Fig. 5. designing decoders for optimal psy- via suitable decoders. This classification One may describe a method of choacoustic results for any encoding involves about 40 pages of mathema- encoding by the way its energy sphere system capable of producing suitable tics, but can be solved exactly. The point varies with encoded direction. The pressure and velocity signals, the aim is theory involved also gives the detailed locus traced out on the sphere as the

www.americanradiohistory.com 38 Wireless World, April 1977

Left leads Right go° 90° 90° 65°

180° Antiphase

Unusable region -120 -90° -115.5°-115.5" -90° Speaker - 107.5° position Left lags Right Fig 8: Three possible choices of Fig 7: Quality of mono and stereo two -channel encoding system having Fig 6: View from right side of energy reproduction shown on energy sphere sphere, showing RM (Regular Matrix) optimized mono and stereo viewed from right side. "Speaker reproduction. BMX and BBC Matrix H system position" curved indicates appearing to two -channel encodings. Angles come from one speaker only in stereo. indicated round edge show the phase 90° lead of the left channel. CF 450 System 45J encoding sound rotates through 360° is shown as pan locus the "pan locus" of the encoding system. Circle 180 ° -1 The best -behaved systems are those in (not energy sphere) which the left -half and the right -half of J the pan locus are mirror images of one another. For such systems, it is convenient to view the locus on the sphere ca from the right hand side; Fig. 6, shows -115° -90° the side view with various existing Fig 9: Showing optimized loci. The angles round the 10: view) system pan non -symmetric distribution of different Fig Energy sphere (side edge indicate the relative phase lead of within the circle picture of two -channel version of right channel, encoded directions the left channel over the "pan locus" of the systems shown System 45J encoding. and the centre point represents left -only edge -on in Fig 8. CF stands for -only. seems best to satisfy the needs of the or right "centre- front," RB for "right- back," CL 7 .a indication of the widest range of users, including record Fig. gives rough for "centre- left" and so on. This figure acceptability of the mono and stereo companies and broadcasters. Moreover, is not a picture of the energy sphere. quality, as previously discussed. The this locus has good performance when shaded nearly antiphase region at the used with existing regular matrix (RM) back of the sphere must be avoided for Another constraint lies in the and UMX equipment for decoding. Thus direct sounds, both because sound in requirement for good surround decod- a changeover to this standard should this region is excessively attenuated in ing. The effect of using a bent locus, see cause minimal disruption, and could mono, and because the sound is very Fig. 6, rather than a circle locus (whose simplify the confused market situation "phasey" and hard -to- localize in ster- side view is -a straight line!) is that by reducing the number of systems on eo. (It is not always undesirable to have surround decoders give poor side - the market. reverberation information in this image localization and it can be proved A further optimization of reproduced region, however). Approximate regions that this is inevitable for any design surround effect comes from a careful of low and medium phasiness effects in made for such systems according to choice of the way different encoded di- stereo are also shown, although the psychoacoustic theory. The asymmetry rections are distributed within the circle boundaries are not in practice sharply between side -to -side and front -to -back locus. Low decoded front -stage phasi- defined. It is possible to have a sensa- performance of bent loci means also ness in surround may be combined with tion of unpleasant phasiness for some that ambience reproduction is poor and uniformly reproduced ambience if a programme material even when it is all that 21/2-channel decoders cannot give a sound -azimuth distribution within the in one low phasiness region, and some substantially flat frequency response circle locus is chosen, as in Fig. 9. This material can sound acceptable even in for all directions of encoding. For these distribution helps widen the stereo the high phasiness region. In practice, it reasons, a circle -locus system must be presentation for front -stage sounds, is found préferable to minimize stereo chosen; otherwise surround reproduc- thus also giving much better stereo phasiness for front -sector sounds, even tion quality inevitability must be compatibility. The front quandrant of if this means making phasiness margin- degraded. directions alone gives an image filling ally worse for rear -sector sounds. Pulling a circle locus as far forward as over 0.8 of the stereo stage in subjective The stereo image must have full stage it will go on the sphere while touching tests. Such "asymmetric circle encod- width. This need not mean the locus the speaker position curve yields possi- ing" requires a careful choice of third - passing through the left -only point, but bilities shown in Fig. 8. As the front - channel encoding to achieve the best can be achieved as long as the pan locus centre interchannel phase angle 21/2- channel decoded results; the mathe- touches the "speaker position" curve increases from 30° to 65 °, the stereo matics of this is described in reference 4. Fig. 7 along which sounds appear to lie phasiness becomes progressively worse The resulting system of encoding, Fig. in one speaker only in stereo. Thus to for front- sector sounds, but better for 10, is called System 45J, and was chosen get good mono and stereo compatibility, back -sector sounds, and mono compa- only after both exhaustive theoretical the locus must be moved as far forward tibility improves. One can argue inde- studies and experimental tests, as well as possible, especially for front- encoded finitely about which compromise of as international discussions within the sounds, while touching the speaker -po- compatability properties is best, but we audio industry. As it is the first system sition curve. have found that the 45 °/- 115.5° locus design based on a complete mathemati-

www.americanradiohistory.com Wireless World, April 1977 39 cal analysis of both system theory and connected to the system would be "a human psychoacoustics, it is possible to Post Office "holding cumbersome, expensive and ineffective say with some confidence that no process and the consumer would have system appreciably different from it can back technical improve- to bear the costs." Another was that all exceed its performance in optimal ment" Mr Ridley hoped to achieve was the surround -sound decoding, so that no creaming off of profitable parts of the further system change is ever likely to Post Office's operations, of which this be needed for horizontal encoding. Sixty -one votes prevented Mr Nicholas was one, leaving the Corporation with Unlike all previous proposals, System Ridley from introducing a bill on unremunerative services like the 45J can handle virtually any legitimate expensively- maintained 'phone February 1 to end the Post Office boxes. requirement in terms of recording monopoly of the supply of telephone There was already competition among philosophy and yet be suitable for equipment. Seeking leave to introduce a private firms for making small private listening in mono, stereo, two -channel bill he said: "It may be that there are branch exchanges, special telephones, surround, 2'/2- channel surround or some subscribers who want telephones data transmission and teleprinter three -channel surround, giving good of different colours from those provided equipment provided by the Post Office, results in all modes. There are no sound by the Post Office, and they cannot get though he agreed the range of the which producers positions should not them. The Post Office monopoly pre- equipment so provided ought to be no use, incompatibility with types of vents it. extended. "The Post Office needs to be recording technique such as coincident "A more important example is the much less cautious and more aggressive microphones, and no requirement that pushbutton telephone device. We have in its-marketing and in the number of variable- matrix decoders be used with pieces these in this House, and I can well of equipment that it provides." their inevitable side- effects. understand why they have not been Joint efforts with manufacturing This choice of encoding system does industry to provide exportable equip- not prevent equipment manufacturers allowed outside. If they were unleashed upon the ment for sale abroad ought to be done from using their own decoding philo- unsuspecting public, dissatis- faction with the Post Office would through putting pressure on the Post sophy if they desire. For example, both increase apace. But there is no reason Office. Sansui Variomatrix and the logic In the division 175 members voted for decoders can easily be adapted or why a really effective pushbutton telephone should not the motion, 236 against. designed for System 45J. However, if be offered to optimum musical results are required, subscribers." decoders satisfying the maximum Other examples, he said, included number of requirements of human utomatic telephone dialling equip - directional psychoacoustics should be ent, loudspeaking telephones, and more varied answering used. We have outlined how such equipment. New hope for solar "Telephone engineers believe that decoders may be built *; and in the near eventually it will be possible for power future, a decoder will be publicly the demonstrated reproducing sounds via telephone connected to one's house to operate as a minicomputer and to give an arbitrary rectangle speaker layout, A student working on a PhD thesis on access to one's bank, department that can also be hooked up to feed a store the properties of films at the depart- or supermarket direct, hexagonal six -speaker layout for an and to allow ment of plasma physics at Sydney one's meter to be read direct by even closer approach to the ideal the University appears to have discovered telephone. There are all ima- illusion. sorts of an important way of tapping solar ginative, labour saving So far, experimental testing has been and exciting energy. Until now, 'solar cells have devices all within the realms of possibi- carried out via about 30 psychoacoustic managed to produce temperatures of a lity. But there is one small difficulty decoder designs for a wide variety of - maximum of 150 C, but the reports the Post Office is sitting on encoding systems, and a broad spec- them, and its from Australia indicate that the new is technology developed to monopoly preventing the proper is trum of studio development of method able to achieve 300 C as well get the best possible results. This these technical as being cheaper than other methods. devices." information will be made available to Details of the method are not yet This criticism also affected the industry. The use of System 45J with the degree available, but it appears to be based of choice available to this technology gives results that are far those subscribers simply on a characteristic of one film more convincing and musical, even via with their own exchanges. His bill that was tried, with chromium oxide as proposed that a two channels, than was the underdeve- committee of indepen- a main constituent, in converting much dent loped "quadrophonic" approach to people should check that any of that part of the sunlight it absorbs equipment developed for was surround sound which has now been the home into heat. The student is a pupil of Dr rendered obsolete by this work. This compatible with the Post Office Charles Watson Monro, the professor of network. was done as a part of the plasma physics, and Professor H. Mes- work The reply to Mr Ridley, the Conser- project of the U.K. National sel. Ambisonic vative member for Tewkesbury, a civil Research Development Corporation. News of the development came about engineer and the opposition spokesman a week before the government pub- References on technology and trade from 1969 to lished its long awaited paper on solar 1970, was given by Mr Ian Wriggles - 1. M. A. Gerzon. Surround -sound psychoa- energy (Solar Energy: its potential coustics, Wireless World vol. 80 1974 pp. worth, the Labour and Co- operative contribution within the United King- 483 -6. member for Thornaby and press dom -Dept of Energy, Energy paper 16, model for 2. M. A. Gerzon. Geometric spokesman for National Giro. He gave a HMSO £3) and announced that the four- speaker matrix stereo two -channel, number of reasons why the bill should Department of Energy would be adding systems, JAES vol. 23. 1975, pp98 -106. be not read. The first was that the £3.6 million to the £2.4 million already 3. M. A. Gerzon. Compatible two -channel Carter committee on the future of the encoding of surround sound Electronic being spent by the Industry and Envir- Post Office was still sitting, and would onment Departments in r & d on solar Letters vol. 11 1975 pp. 615 -7. probably consider 4. M. A. Gerzon. Optimum choice of sur- this very point. The energy. The main areas of the new study round -sound encoding specification, 56th second was that the Annan committee will be in domestic water and space AES convertion, Paris March 1977 was also sitting; "It will no . doubt heating. Up to half the cost of suitable comment on the future of cablevision projects by commercial firms would be Following articles will give circuit details of a and on the whole question of common supplied. decoder based on these principles and which will carrier cables." decode system 45J and stereo for sqùare, restangle A lecture on "An experimental and hexagon speaker layouts, with distance and A third reason he gave was that the energy- saving house" will be given at psychoacoustic compensation. - Tech. ed. testing of each piece of equipment to be the IEE, Savoy Place on April 21 at 5.30.

www.americanradiohistory.com 40 Wireless World, April 1977 Characteristics and load lines 5 - Non -linear load lines by S. W. Amos, B.Sc., M.I.E.E.

Part 3 (October 1976) and Part 4 (February) were devoted to linear load Input current lines but in practical circuits load lines waveform can, be non -linear for a number of d.c. load line reasons. In this part we shall examine the forms of pon- linearity of load lines that can occur and the effect this has on circuit performance.

d.c. load lines 40µA A.c. and Output current When a load resistor R1 is capaci- waveforms tance- coupled to a following resistor R2 there are effectively two load lines, one representing the steady -state or d.c. conditions in the circuit and the other representing the signal- frequency or a.c. conditions: these are sometimes A known as the static and dynamic load lines. Because the a.c. resistance in the load circuit is necessarily less than the Ic a.c. load line has a d.c. resistance, the ( mA) greater slope than the d.c. load line and intersects it at the quiescent point as shown in Fig. 1. As a result the output VC (V) voltage available from an amplifier is reduced by the connection of R2: in Fig 1 the peak -to -peak value of the voltage is reduced from AB to ab. It is possible that the reduced output may still be Output voltage adequate for the following stage but the waveforms restriction of output voltage is sometimes serious and it is useful to know precisely how great it is. The calculation Suppose the amplitude of the input Fig. 1. The reduction in output voltage is easy because the voltage developed signal to an amplifier with an unshunt- due to the different slopes of d.c. and across an unshunted load resistor R1 is ed load resistor is adjusted so that the a.c. load lines. IR1 where I is the alternating compon- operating point moves over the entire ent of the active device output current. length of the d.c. load line. If the load is a.c. load For the shunted resistor the output now shunted the operating point line voltage is IR1R2 /(R1 + R2) in which the transfers to the a.c. load line which is reactance of the coupling capacitor is rotated clockwise with respect to the assumed negligible compared with R2 at d.c. load line about the quiescent point. 1 d.c. load the operating frequency. The ratio of As a result one half cycle of the output line the two voltages is R2 /(R1 + R2) which signal is clipped as shown in Fig. 2. In shows that if the shunting resistor is effect the a.c. load line now includes a equal to the load resistor the output short length of. the voltage axis and is voltage is halved. To limit the reduction thus non -linear. This may seem an in output voltage to 10 per cent of that academic point because any distortion R1 alone, R2 must not from such non -linearity could developed across arising v be less than 9 R1. This underlines the easily be avoided by reducing the c requirements, well -known for a voltage amplitude of the input signal so that the amplifier, that the output should be excursions of thè operating point are terminated in a high -value resistor. confined to the linear portion of the a.c. Fig. 1 also shows the output current load line. The reduction in amplitude waveform as a reminder that there is no required to do this is given by the corresponding reduction in amplitude expression deduced above R2/ (R 1 + R2). I Output voltage I waveform as a result of shunting the load. On the This is not an academic point, however, contrary the effective reduction in the because in diode a.m. detectors har- Fig. 2. Clipping of output voltage value of the load resistance increases monic distortion can arise from pre- waveforms as a result of the difference the current output. cisely this cause if there is a resistive in slope between a.c. and d.c. load lines.

www.americanradiohistory.com Wireless World, April 1977 41

1V pk 0 5V pk OV passes through the quiescent point as 05 shown by P'QR' in Fig. 3. This load line intersects the voltage axis at -0.15V, so clipping one of the peaks of a 100 per 04 cent modulated input to the detector as a.c. load line (3.33kO) shown by the shaded area. This 0.3 represents serious distortion because 7.c. load he the upper third of the amplitude range (5kí1) of the signal is not reproduced. The 02 detector can operate reasonably successfully only if the depth of modulation u 0.1 of the input signal is limited to 67 per I u cent. The tendency in a.m. broadcasting II I R Fig. 5. Skeleton form of a driver feeding is, in II I I II fact, to keep the modulation -B -1-0 -0.8 -0.6 -0 4 -0.2 R' O a complementary class stage. percentage high so to give a good signal -to -noise ratio. Thus to enable the DIODE ANODE VOLTAGE Tra detector to handle high modulation conducts percentages the shunting effect on the diode load must be minimised and the a.f. amplifier should therefore have an input resistance high compared with the value of the diode load. Perhaps the easiest way of ensuring low distortion would be to interpose an emitter a.c. load Peak not line follower reproduced between the diode load and the Tr2 a.f. amplifier. Fig. 3. Clipping of output voltage of a Conducts diode detector as a result of the different slopes of the a.c. and d.c. load lines. vc Non- linear load resistance in Fig. 6. D.C. and a.c. load lines for the So far this series it has been assumed circuit of Fig. 5. that the loads presented to active devices are purely resistive: the load lines are accordingly linear, showing the direct proportionality between current and voltage for such loads. Ib If, however, active devices are connected in cascade as in multi -stage equipment the load for one stage is often largely determined by the input resistance of the following stage. For a bipolar transistor the input resistance is Vb - not linear but varies with input voltage as indicated by the lb-Vb characteristic Fig. 4. Relationship between base in Fig. 4. The slope of this curve is low current and base voltage for a bipolar for small values of Vb showing that the transistor. input resistance is high for such values but as Vb increases the slope increases and the input resistance decreases. For shunt on the diode load. The mechanism Fig. 7. A.C. load line P'QR'shows the small alternating signals the changes in of the effect is illustrated in Fig. 3 which effect of doubling the step -down ratio input resistance may be negligible and it shows the anode voltage /anode current of the driver transformer feeding a is common in the design of small -signal characteristics for a diode. These are class -B stage. amplifiers to assume that the input sometimes known as rectification char- resistance is constant throughout each acteristics and each curve shows the cycle of input signal. For large signals, relationship between current and vol- the characteristic for 0.5 -V peak value however, the variations are significant tage for a particular value of peak input. intersects the load line. In the absence and must be taken into account in It is assumed that the diode feeds a of modulation, therefore, the diode designing circuits. This is particularly capacitor which charges up to the peak anode has a voltage of -0.38V and the true of the input resistance of class -B value of the applied signal. Thus for a diode current is 0.07mA. When 100 per stages where the transistor is biased 1 -V peak input signal the diode anode cent modulation occurs the operating near collector -current cut -off and is takes up a voltage of -1 V for zero point moves up and down the d.c. load driven into conduction. by the input anode current. If current is taken from line between the limits of 0.86V (1.7mA) signal. Because a transistor so biased the diode the anode voltage falls as and zero. This represents the perfor- can amplify only one half cycle of a indicated by the slope of the character- mance of the detector if its true load at sinusoidal input, class -B stages in linear istics. If the signal applied to the diode is signal frequencies is 5 kilohms. equipment are operated in push -pull. amplitude -modulated the peak value In a practical circuit, however, the This makes the stage symmetrical so varies in accordance with the waveform output of the diode must be applied to that the input resistance for a particular of the modulating signal and for a 0.5 -V the following stage, normally an a.f. value of positive -going input is the same peak signal, modulated 100 per cent, the amplifier, and this stage has an input as for a negative -going input of equal input swings between zero and 1V. The resistance which shunts the diode load. amplitude. diode load can be represented by a d.c. Let us assume that this has an input As input increases, however, input load line as discussed earlier and PQR resistance of 10 kilohms. The a.c. load resistance decreases. To deduce the shows a load line for 5 kilohms, a value resistance is thus 3.3.kilohms and the a.c. effect of such input- resistance varia- commonly used in transistor a.m. load line therefore has a slope corre- tions on the shape of the load line for the receivers. Q is the quiescent point where sponding to this value of resistance and driver stage consider the circuit shown

www.americanradiohistory.com 42 Wireless World, April 1977 in Fig. 5. The d.c. load line for R, is PQR for operating points near Q) for which which matters and, provided the load in Fig. 6 and this represents the the class -B stage presents a high line is reasonably steep, there is unlikely relationship between Try collector vol- resistance. The rotation increases how- to be serious distortion of the current tage and collector current in the ever as signal amplitude increases and waveform. This is to be expected absence of any shunting effect from the operating points move away from Q. because a current amplifier should be following class -B stage. Q is the quies- Thus the a.c. load line has the elongated presented with a low -value load. Such a cent point at which, we shall assume, S shape shown as P 'QR' in Fig. 6. load ensures that any load -value varia- the two class -B transistors Tr2 and Tr3 If a sinusoidal signal is assumed tions have negligible effect on the are almost cut off. The effect of a applied to Try base it is possible to output current and that most of the resistive shunt on R° is to introduce an deduce from Fig. 6 the waveform of the current enters the class -B stage rather a.c. load line which passes through Q corresponding collector current and than R. and is rotated clockwise with respect to voltage. The curvature of P 'QR' is such If a transformer is used to couple a the d.c. load line to an extent which that it can cause serious distortion of class -B stage to the driver stage, the increases with decrease in the value of the collector -voltage waveform but this turns ratio can be adjusted to present the resistive shunt. Thus the rotation is is not generally of importance because the driver stage with a desired value of slight for small-amplitude signals (i.e. it is the shape of the current waveform load resistance. As an example consider Fig. 7 which shows at P'QR' the load line representing the input resistance of a class -B stage. If the step -down ratio is doubled, the effective resistance at the primary winding is quadrupled and the driver stage is called upon to deliver twice the voltage swing and one half the current swing. The load line thus rotates anticlockwise about the quiescent point and its new position is at P'QR'. Elliptical load lines In linear amplification where transformers are used between cascaded stages it is normal practice to make the v primary inductance so large that the reactance even at the lowest frequency B is large compared with the load resistance. The effective load is then purely resistive and the load line is linear as C described earlier. Suppose, however, that the shunt D reactance is not large and absorbs an appreciable fraction of the output current, or that an inductor is connect- IE ed in series with . a load resistor to extend the upper frequency limit as in a Fig. 8. Current- voltage relationship for a linear resistor. video amplifier. How does the reactance so introduced affect the load line? To determine this consider Fig. 8 which shows the current- voltage relationship for a linear resistor initially free of associated reactance. It is assumed that the resistor is the load of a transistor and the voltage plotted along the horizontal axis is not the voltage drop across the resistor but the voltage at one end of it, e.g. the collector voltage of the transistor feeding the resistor. The other end of the resistor is assumed U connected to the positive supply terminal. Thus an increase in the collector voltage means a decrease in the voltage across the resistor and a proportional decrease in the (collector) current through it. If the collector current varies sinusoidally as shown at abcde the corresponding collector voltage ABCDE is inverted with respect to it. Suppose now that the resistor is shunted by an inductor with a reactance C at the frequency in use of twice the ohmic value of the resistor. The sinusoidal current abcde flows in the resistor as before but there is now an additional current (in the inductor) which has half the amplitude of the resistive current and lags it by 90 °. This Fig. 9. Derivation of the elliptical load line for a parallel LR combination. reactive current is shown as a'b'c'd'e' in

www.americanradiohistory.com Wireless World, April 1977

t- V

F V

Inductive voltage

Fig. 10. A purely- reactive load has a load line in the form of a true ellipse. This ellipse and the associated current Combined Resistive I voltage and voltage waveforms apply to a voltage purely- capacitive load.

Fig. 9. The current in the LR combination, i.e. the output current of the active Fig. 11. Elliptical load line for a series LR combination. device, is the sum of abcde and a'b'c'd'e'. If we take the datum line ace as representing zero current, the sum of 16 100mA a and a' is at a'. Similarly the sum of b 90 and b' is at b. By continuing in this way 1 4 Collector current we can deduce the shape of the wave- 80 waveform form of the net current. It is in 12 shown 70 dashed lines a'bc'de' in Fig. 9 and is, of course, sinusoidal with a frequency 1 0 60 equal to that of the voltage I (A) but phase 0.8 retarded relative to the voltage. The 50 amplitude of this current is in fact 06 40 approximately 1.12 of that of the t resistive current and is 26.5° retarded 04 30 relative to it. We now know the waveform of the voltage across the LR 02 20 combination and that of the net current 10 through it. From this information we o can deduce the form of the load line in 10 20 30 1 40 50 60 70 the following manner. The current corresponding to voltage A is at a': vertical and horizontal lines from these points meet at U which is therefore a point on the load line. Similarly the current corresponding to voltage B is at I Collector voltage b giving point V on the load line. By waveform continuing in . this manner we obtain points X and Y and the next point is back again at U, showing that the load line has the form of an ellipse and that the operating point moves in a clockwise direction around the circumfer- ence of the ellipse at the rate of one revolution per cycle of signal. Fig. 12. An elliptical load line superimposed on a set of I,V,, characteristics. The elliptical shape results from the interaction of two sinusoidal signals at the same frequency but with a phase The ellipse shown in Fig. 9 was for a time moving anticlockwise around the displacement between them and can be parallel combination of resistance and perimeter. demonstrated on an oscilliscope by inductance. For a parallel RC circuit the In a series LR combination it is the applying the two signals to the X and Y reactive current is phase advanced on current which is common to the two plates: the ellipse is, in fact, one of the the voltage but a similar elliptical load components. As shown in Fig. 11 the Lissajous figures. line results, the operating point this voltage across the resistor is in phase

www.americanradiohistory.com 44 Wireless World, April 1977

with the current; that across the the antiphase condition by 261/2°. If the current swing from 13mA to 83mA gives inductor leads the current by 90 °. The load line for a parallel reactance /resis- a collector current swing from 0.15A to two voltages are added to obtain the net tance combination is known only as an 1.25A. The corresponding collector voltage across the combination and ellipse the position of the linear load line voltage swing is from 60V to 10V. this, together with the current wave- representing the resistive component Although the current limits are 0.15A form, enables the shape of the load line can be found by drawing two vertical and 1.25A some of this is due to to be deduced. It is again an ellipse and tangents to the ellipse at its left -hand reactance (see Fig. 9) and the useful operating -point rotation is clockwise. A and right -hand extremities and by power output is provided by the swing series RC combination gives a similar joining their points of contact. (For a between 0.2A and 1.2A, the current ellipse but the operating point moves series reactance /resistance combina- limits for the linear load line. The anticlockwise around it. tion the tangents should be horizontal single -peak current and voltage values The "fatness" of the ellipse, i.e. the and touching the upper and lower are thus 0.5A and 25V giving the power ratio of the minor to major axis, extremities of the ellipse). The recipro- output as 6.25W. depends on the phase displacement cal of the slope of this line gives the This has been by no means a complete between the current and voltage in the value of the resistance. This construc- account of load lines: for example there load. If there is no displacement the tion has been carried out in Fig. 12 and has been no mention of load lines for ellipse becomes the linear load line VY the linear load line PGR corresponds to push -pull amplifiers. It is hoped, how- in Fig. 9. If there is 90° phase displace- a resistance of 50 ohms. The shunt ever, that it has proved an interesting ment, as for a purely inductive or reactance is 100 ohms. An input (base) introduction to the subject. capacitive load, the ellipse has the form shown in Fig. 10. The major and minor axes are now vertical or horizontal and this is a true mathematical ellipse obeying the equation x2 /a2 +y2 /b2 =1. *. By suitable choice of scale for the current and voltage axes the major and minor axes can be made equal and the ellipse then becomes a circle. An elliptical load line such as that shown in Wireless World amateur radio station ,Fig. 9 is a combination of a true ellipse (representing the reactive component On January 29 Wireless World's amateur Dorset House, Stamford Street, London of the load as in Fig. 10) and a linear load radio station went on the air. This club S.E.1, is situated at the top of a nine storey line (representing the resistive com- station, call sign G8LWW, is licensed to building at about 50m above- sea -level. In due operate in the amateur frequency bands from Wireless World intends to design and An important course ponent of the load). point 144MHz and above (conditionally up to build its own equipment but until time can be is that the ellipse is not symmetrical 24GHz). Under the recently- modified licens- found to carry out this project the station will about the linear load line but is rotated ing conditions this means that Wireless continue to use tried and proven commercial slightly about the quiescent point in a World is permitted to operate the n4odes of equipment. Equipment presently in use in the clockwise direction for a parallel reac- fixed, mobile, pedestrian mobile, r.t.t.y. 144 to 146MHz (2 metre) band is the Icom tance /resistance combination and (radio -teletype), television, slow -scan tele- IC201 multi -mode transceiver which pro- anti -clockwise for a series combination: vision, facsimile, data and d.s.b.s.c. (double - vides f.m., u.s.b., l.s.b. and c.w. modes. This thus the resistive load line does not sideband suppressed carrier). This will also 'rig', which uses a v.f.o. to give full 2 -metre through full for repeater coincide with the major axis of the include satellite communications coverage, also has facilities the amateur satellites Oscar 6 and Oscar 7. and reverse repeater, an automatic tone ellipse. The decision to have a permanent station burst, break -in on c.w., and v.o.x. The shaded areas in Fig. 9 represent was made in order that Wireless World can (voice- operated switching). The 10W output the additional current which the active participate, in the practical sense, in com- is fed into a ten -element crossed -yagi aerial device has to deliver as a result of the munications in the same way that it does in mounted twenty feet above the roof of the reactive component of the load. The the electronics field through constructional building on a heavy -duty rotator, and voltage swing is unaffected by the projects. This is the first time the journal has connected for right -hand circular polariza- addition of the reactive component as had a permanent amateur radio station; the tion (in preparation for satellite would be expected for a parallel com- only other time that an amateur station communication). The aerial apparatus and operated from its offices was when Wireless associated equipment was supplied by South bination. World celebrated its 60th anniversary in 1971 Midlands Communications Limited. G8LWW 11 applies to a series LR combin- Fig. with the station GB3WW operating under a is presently being operated by the licensee, ation and the shaded areas here repre- special short-term licence (see May 1971 Ray Ashmore, an assistant editor of Wireless sent the additional voltage which the issue). World, whose own call sign is G8KYY. The active device must deliver as a result of The station, whose "main address" is at station also has available an h.f. (3 to 30MHz) the addition of the reactance: the transceiver, the Yaesu Musen FT301, which current swing is unaffected. has been operated from the Wireless World Curvature of load lines is usually station by Ron Leath under his call sign with waveform distortion G4ASE. This transceiver, which is capable of associated delivering the maximum permissible output and it might therefore be expected that of 400W, was used with a 40 /80m trap -dipole an elliptical load line (which has and, after only three QSOs on 80 metres, pronounced curvature) would also made contact with SV4KS in Greece. produce disortion. In fact, as shown in One disadvantage of the station location is Fig. 9, it produces phase shift between a 31 storey building, part of the IPC complex, the current and the voltage waveforms. directly to the north and only about 100m This is perhaps clearer in Fig. 12 which away from the aerial. Although the effect shows the same elliptical load line that this building has on transmission and reception from and to the station has not yet a set of lc-V° superimposed on been accurately determined, it represents a characteristics. For the particular reac- line -of -sight restriction of about 12 degrees, tance /resistance ratio chosen (2:1) the which will make contacts to the north of collector voltage is phase advanced on England and Scotland more difficult on 2- metres. However, it is hoped that the favourable "take -off" towards Europe will prove interesting, especially during the * This equation applies when the centre of months when good v.h.f. propaga- the ellipse is the origin of the rectangular summer will be more frequent. co- ordinate system. tion conditions

www.americanradiohistory.com Wireless World, April .1977 Metal detector

B.f.o. circuit using fifth search oscillator harmonic for enhanced sensitivity

by D. E. O N. Waddington, M.I.E.R.E.

Metal detectors have fascinated If you find any gold or silver, report to affect the sense of the change. At people for a long time and a great the find immediately to the police, who first sight, it would appear a simple many have been designed and built. will inform the local coroner. He will matter to apply this principle to a Some work, but a high proportion hold an inquest to decide to whom the practical metal detector but there are a have been abandoned as impractical find belongs. (A study of the laws number of problems which need to be by their disillusioned constructors. relating to 'treasure trove' will help you overcome before a satisfactory design This article, in addition to giving the to understand your rights.) can be achieved. The first of these design for a practical metal detector, If you find unexploded ammunition concerns the search coil. will explain some of the pitfalls and or a bomb, mark the place, leave well The frequency of oscillation will show how they may be circumvented. alone and inform the police. change if the reactance of the coil Do not leave a mess after excavating changes at all. Thus it is as susceptible your finds. to capacitance as to inductance The issue of a licence does not changes. Indeed the change in coil absolve the licensee from obtaining All the metal detectors known to me capacitance caused by moving it any necessary consent before entering relative may use the modification of the magnetic to the ground well exceed on any private property with any the inductance change caused by the field associated with one or more apparatus. inductors to locate metal. Three main object being sought. Fortunately, it is quite easy to minimize this effect by types are made commercially; b.f.o., The principle of b.f.o. the detector is fitting a Faraday screen to the coil. This induction balance and pulse induction. illustrated in Fig. 1. The outputs of two is done by wrapping the coil with a I will confine my description to the oscillators, tuned such that there is a conductive foil, which is to b.f.o., since this is the simplest to small frequency connected difference between the internal "earth" of the oscillator. implement and, provided that due them, are mixed. The difference There should be a break in the foil so precautions are observed, it is adequate frequency is selected by a low -pass that it does not constitute a short -cir- for most purposes. filter, amplified and fed to a loud- cuited turn. When I first tried this out, I Before proceeding any further, how- speaker or headphone. When a metallic feared that it would reduce ever, I think that it is as well to look at object is brought near to the search the sensitivity of the coil to metallic objects some of the legal aspects of metal coil, its inductance changes causing a but measurements showed that the detectors. Since, under the terms of the change in 1 the frequency of oscillator sensitivity was unchanged, while Wireless Telegraphy Act 1949 they and a corresponding change in the have been deemed wireless telegraphy difference frequency. capacitive effects were reduced to Non -ferrous negligible proportions. Another apparatus, they come under the metals will cause cause the frequency of the frequency jurisdiction of The Home Office who, at search oscillator to increase of spurious change is heat: and moving the coil from sunlight to shade present, requires that a licence should ferrous metals should have the opposite can cause a large and fairly rapid be obtained for the use of the detector. effect. I use the word "should" since, in frequency change. This effect can Currently, this is £1.20 and permits the practice, both the shape be of the object reduced by suitable thermal insulation. use of a "pipe finder" for a period of and its state of decomposition appear five years. In addition, the frequency of In order to select the best size of coil 1. for the I made a series operation is limited to the range from Fig. Block diagram of a simple b.f.o. detector of tests metal detector. 16 to 150kHz, with a forbidden band plotting the frequency change caused from 90 to 110kHz. In practice, the preferred bands are 85 to 90kHz and 110 to 144kHz. Before a detector may be used it must be "type approved" by the Home Office. Needless to say, the circuit to be described has approval. With regard to the use of the detector for "treasure hunting" it is as well to observe a few rules: Never prospect a known archaeological site. If you do, you will incur the undying wrath of the archaeological fraternity in addition to possibly destroying historical information. Report unusual historical finds to your local museum.

www.americanradiohistory.com 46 Wireless World, April 1977 of 250Hz this change could only be heard by a trained listener. Since a normal loudspeaker or headphone does not reproduce low- frequency tones, the (a) low frequency waveform can be converted into a pulse train, which is then easily reproduced. The sensitivity of the b.f.o. can be increased as shown in Fig. 3. Here the search coil oscillator is operated at a frequency of 125kHz and its output is converted to a square wave, which is rich in harmonics. The beat oscillator runs at a frequency of 625kHz, i.e. five times the search oscillator frequency. Thus, the beat oscillator is mixed with 4 I 3 O 1 a.n the 5th harmonic of the search oscillator so that any frequency change is multiplied by five. This makes it very much easier to hear a change in frequency, although the susceptibility to drift is much greater. A higher harmonic could be used but it should be remembered that, with a square wave, only odd harmonics are present and the amplitude of the harmonic will be equal to the amplitude of the fundamental divided by the harmonic number. The rather odd choice of frequencies has been dictated by the fact that most constructors will only have a medium -wave radio receiver for setting up purposes and will have no simple means of checking the frequencies. If 4 the beat oscillator is set to 625kHz, the beat note will only be heard strongly if Hz (c) the search oscillator is tuned to an odd sub -harmonic (625/5 = 125 or 625/7 = 89.286) and the forbidden band from 90- 110kHz will be avoided. This pre- caution is necessary as it is difficult to control all the stray capacities associated with the search coil. Design The circuit of a metal detector based on 6in 6in the above considerations is shown in Fig. 4. I chose the "long- tailed -pair" because it Fig. 2. The lines show the contours of oscillator for this application equal frequency change for a''hp coin one of the main problems in using a is easy to design, the tuned circuit needs at a frequency of 100kHz with various b.f.o. metal detector. One very practical only two connexions and the output is coil sizes (a) 6" (b) 8" (c) 10" solution is to set the oscillator isolated from the tuned circuit so that frequencies such that the frequency the frequency of oscillation is virtually by loading or signals fed to difference is very small < 1 OHz. When unaffected by a '/zp coin with various coils. The this is done a change of one or two the output. This last is particularly inductance of the coil does not appear hertz is readily discernible. If the important for this application, in which to be an important factor, but the frequency difference were of the order it is essential that the oscillators do not diameter is. The results for 6in, 8in and lock to each other when the frequency, Fig. 3. Block diagram of an improved 10in are shown in Fig. 2. They may or in this case, harmonic frequency coils metal detector. not be strictly accurate, since the measurement is a very tedious one, but they do show what is to be expected. The important points are: Search coil The frequency change is very shall. The sensitivity at the centre of the I Search smaller coils is much the same, while oscillator the loin coil is less sensitive. 125kHz The larger the coil, the larger the sensitive area. However, this is not alw. an advantage, since it is still dt necessary to pin point the article being sought and the smaller coil gives a much better "focus ". For my own Beat oscillator design I have chosen the 6in coil. 625kHz The magnitude (or should I say smallness), of the frequency change is

www.americanradiohistory.com Wireless World, April 1977 47

R1 2k2

R2 1k8

Fig. 4. Circuit diagram for metal wind 45 turns of 26 s.w.g. (0.46mm) wire and wind this around the coil. Cover the detector. around the pins. Tape the coil in four whole with another layer of tape. places to stop it springing undone. Assemble the coil to the handle and difference is small. The search oscillator Remove the pins. Tape the coil tightly to paint it with white waterproof paint. uses Ir1 and Ire with L1, C1, C2 and C3 the underside of the wooden ring, forming the tuned circuit. It will taking care that the ends of the winding probably be necessary to select C, to come opposite to the tab for the handle. Setting up give the correct frequency, since the Cover the coil with a second layer of The first step is to set the beat oscillator Faraday screen and the screened lead tape. Cut a strip of aluminium cooking add an indeterminate to the correct frequency. amount of capa- foil about 1 in wide and tape the coil with citance in parallel with the coil. This it, starting on one side of the tab and Short the search coil to disable the capacitance depends upon the physical finishing at the other. It will probably be search oscillator. construction of the coil and the necessary to use more than one length materials used and is rather variable. Switch on and adjust the core of L2 so of foil, in which case the ends should be that the frequency of the beat oscillator Coarse tuning is carried out by C2, while overlapped. However take care that the is set to 625kHz. If you have no access to C3 is used for fine adjustment. The start and finish of coil the do not short a frequency counter, a medium wave search oscillator output is taken from to each Bind other. the finish of the coil radio receiver may be used. Set the dial the collector of Tr2 to the mixer Tr3. The with 22 s.w.g. tinned copper wire and of the receiver to 625kHz (480m). If beat oscillator uses Tr4 and Try; L2 the and connect it to one end of the coil and to receiver has an aerial connection, place Ca form the tuned circuit, which reson- the screened lead. The other end of the the aerial lead close to the oscillator, but ates at 625kHz. The drive to the shunt coil is connected to the centre conduc- if it only has a ferrite rod aerial it will be gate mixer Tr3 is taken from the tor of the screened lead. Cover the coil necessary to place the receiver close to collector of Tr4. The difference fre- with a layer of tape. Cut a lin wide strip the oscillator. This setting up must be quency is selected by the low -pass filter, of Vain thick expanded polystyrene sheet carried out with the detector circuit formed by R9 and C9 and is amplified by mounted in its screened box lid IC1, with the differentiated and then fed to Tr6, Fig. 5. Layout of circuit, which drives using pin off. Tune for maximum signal. Re- the 'phones or board (no copper tracks). member that you will be looking for an loudspeaker. The volume can be controlled by connecting a variable resistor in series with the output.

Construction The layout of the circuit does not appear to be critical - a practical version using matrix board is shown in Fig. 5. Mount the circuit inside a screened box so that hand capacitance does not affect the tuning. The construction of the search coil is very important. It should be sufficiently o robust to withstand rough handling, Phones + light, so as to be portable and adequa- `C12 C13 tely insulated against temperature change and moisture. I found that the, construction shown in Fig. 6 works very well. First cut a ring of about 3/ein plywood as shown. To wind the coil, draw a 6 %in diameter circle on a piece of wood. Hammer 3/4in panel pins at about lin intervals around this circle and then

www.americanradiohistory.com 48 Wireless World, April 1977 HF predictions

Wood former 6M inside dia. 3/8 in cross section Predicted disturbed days are 1st to 3rd and 17th to 24th of the month. Seasonable trend and low solar activity combine to produce FOTs and LUFs which give a restricted choice of time and frequency for reliable day to day communication. The charts show that this restriction is Expanded Hole for screened lead particularly severe for circuits having both polystyrene terminals in the northern hemisphere.

Screened lead MHz

20 Note break in screen 15

10 8 Fig. 6. Coil construction. (c) If the frequencies are too close 6 5 unmodulated carrier, so that only hiss together, the search oscillator will 89.3kHz. 4 will be heard. However, you can check probably be running at Reduce whether you have the correct carrier by the value of C1 and repeat the proce- 3 dure. If possible it is a good idea to selèct shorting the coil. The next step is to set Aires a value of C 1 which gives the correct Buenos 111111111111. the search oscillator to the correct 30 C2 This frequency. frequency with set to mid travel. ------.-- will allow for any drift which may occur Remove the short from the search 20 IMMINEENIIIMME_ coil. during the life of the detector. --25- 15 ;_ Set both the coarse and fine controls nwÇjfgÓQ1ZQm..a.m.. to mid -travel. 10 -r V/e1i'1rQQ == ===Q for C 1. C.N Fit a 470pF capacitor 6 Table 1 Adjust C2 and check that a beat note úä can be obtained. If necessary increase 6 M11111>7.i Harmonic s IMM=W.NINIMMIEMMII C2 r'/iMaMMIMMMMMIIIMINIMMMMOMii the value of by 100pF. Number Frequency Wavelength 10111111-NNN1111==N=N When a beat note is heard, check the 4 M1r NNNNN frequency of search oscillator as NN11NNNNNNNN the 5 625 kHz 480 m follows: 6 750 kHz 400 m Johannesburg (a) Short the beat oscillator tuning coil. 7 875 kHz 342.85 m 30 (b) Using the receiver near the search 8 1000 kHz 300 m 9 1125 kHz 266.67 m coil, look for the harmonics of the 20 1250 kHz 240 m which should be as 10 search oscillator 11 1375 kHz 218.18 m 15' shown in Table 1. It is very probable 12 1 500 kHz 200 m kHz m that you will only be able to identify the 13 1625 184.615 10 frequencies. odd harmonic 8

6 5 4

PARTS LIST 3 Capacitors Resistors Hong Kong 1 560pF polystyrene (see text) 1 2k2 All resistors 1/4W ± 5% 30 2 1k8 2 150pF variable 3 1 opF variable 3 1k 20 4' 6k8 4 0.01-1F disc ceramic 5 .:F ceramic 5 15k 0.01 disc 15 6 15k 6 0.01.:F disc ceramic 7 1k 7 0.01..:F disc ceramic 10 \ 8 6k8 8 150pF polystyrene 9 100V P.E.T. 9 1k 0.1-:F 8 -1 -- 10 1k 10 0.1 .,F 100V P.E.T. 6 11 4k7 11 47-:F 10V electrolytic 12 470k 12 4.7_F 10V electrolytic 5 13 2k2 13 100-F 10V electrolytic 4 14 10k 3 15 300k o 4 8 12 16 20 G.M.T. Tr1, 2, 4, 5. 6 BF238, BC I0á or equivalent Tr3 BC308, BCY72 or equivalent D1 2 1N4148 IC1 .:A741C L1 see text L2 49t 0.28mm wire or Mullard Vinkor LA1 157 (260_H)

www.americanradiohistory.com The new T 900 fromTektronix is good news for everyone. (See it at theA l l- Electron ics Show) Here's the feature story: And second, because they cut to a minimum and are reliable and freely maintenance is simplicity This new development in portable - at only 15 lbs. itself thanks to new levels of oscilloscopes from Tektronix The T900 range takes reliability engineering. is a family of workhorses. Tektronix into new territory. The T900's are very rugged, And they're going to 10 to 35MHz; single or dual very strong. become very familiar to you. trace; all with 2mV And they're so easy to use First, because their sensitivity; one with storage. you'll soon come to regard specification is tailor -made You will also benefit from the model you choose as to the increasing require- a new level of economy and a indispensable. ments of engineers for lower operating cost. enhanced performance. Unprofitable downtime is W W-005forfurtherdetails. ;; TEKTRONIX Tektronix U.K. Ltd., Beaverton House, P.O. Box 69, Harpenden, Herts. 'l'el: Harpenden 63143. Telex: 25559. \^V'; the five new oscilloscopes':} approach to possible servicing Ar 7- ? 'î cI tronix now tieing introdu9 ,,§% requirements. .,...-o P*large or 1.--.4, , 'ç Ott\ e e, to the UK, we would like to V' ,s`';crcit boards are toy ' The "%a , you some background s .-.' . . 3 ,' le sided tA ... sS 5.6 -a . -c5 ~ information before you begin ce. p só; their evaluation. Gta 1;* g (All the spec. details are red at contained in our full colour d eep sheet - which is yours for the asking.) of the

Atfi. Aky see ther IMTl,Srf ds up to G àr asbei- ° icatFts al graticule 1-(per'. ro Nat b ¡°'er ^¢ ° all _7for o . , so 01. ..., s ; eir`. ,c, oa1 ch s, are to o`4v ht /,so hay 0v't higher was felt possible for inst at their price. Here's How We developed,oscilir' circuits with f vr- ö save than before increased reli-11Aone nts are reduced com grater keep the price servicing Then we mum. possible use of machin. components to further re the cost of purchase. Still on an innovato.: .trail, seein`

looked for a CRT . .. a :would require only a fra r t . :._. he www.americanradiohistory.com Wireless World, April 1977

The new Maplin Catalogue is no ordinary catalogue...

`EciAPáp111

SUPPLIES '/ ,

some super digital clocks. A alai with alarm. the eat weslock snooze ana r lock wdh Pdispl yblanl automa dis0laY When switchtthe blanking enc off ur to timer thats very time wither and Ottp apresettime on ate Preset got a tape- recorder -it there's no need míos Your favourite Programmes toe eaam. ever

Catalogue includes a very wide range of components: hundreds of different capacitors; resistors; transistors; I.C's; diodes; wires and cables; discotheque equipment; organ components; musical effects units; microphones; turntables; cartridges; styli; test equipment; boxes and instrument cases; knobs, plugs and sockets; audio leads; switches; loudspeakers; books; tools - AND MANY MANY MORE.

1 R CATALOGUE FORYOURÓOP MONEY NOW. NA APPROVALPrrice50p-SEN MO 197717. satisfied Ì your completely days APPRO 1 am 14 ' ON a copy by n rush me post. 50p 'within d Please return °f tinny, Will 1 send catalogue p a return the catalogue every 1 may tasd°uld understand I it is worth m not satisfied, that am Without obligation. o{ receipt. 1 1 4 daysa from Your within anythingthing you not purchase Our bi- monthly newsletter keeps you up to date with latest need it to keep guaranteed prices - our latest special offers (they save you choose pounds) - details of new projects and new lines. Send 3Op i NAME for the next six issues (5p discount voucher with each copy). I I ADDRESS WW'

Box J 1 S=plies - MaPhn Electronic pun ELECTRONIC SUPPLIES .--' DON'T DELAY POST COUPON NOW P.O. BOX 3, RAYLEIGH, ESSEX SS6 BLR Telephone: IT COULD BE THE BEST 50p YOU'VE EVER Southend (0702) 715155 Call at our shop 284 London Road, Westcliff -on -Sea. Essex SPENT (Closed all day Monday) Telephone Southend (0702) 47379

WW - 007 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 53 the sector working party reports but Radar simulator for the also on the whole range of Government RAF policies. News of An element of the Government's as yet vague proposals especially welcome to the components chiefs will be that A simulated timebase and echo although in the current economic the Month generator (STEG) is to be added to the circumstances resources are limited, "to airborne early warning mission trainer the extent that public money is needed at RAF Lossiemouth. The STEG will to solve the problems of the five sectors generate fifteen controllable radar set out above (or those of other sectors) targets on the AEW trainer displays as or, indeed to push forward the work on well as "own" aircraft movement, sea industrial strategy generally, the clutter, Indicate Friend or Foe, thermal resources will within reason be availa- noise and a blind arc. The simulator, ble." which is portable, can also superimpose The proposals also follow news of a radar echoes on to a background £20 million aid scheme for the compon- picture derived from a video recording ents industry, which Wireless World of an actual mission. Operators learn to reported last month. Still further help spot unidentified radar echoes and to is expected from the European Com- guide interceptor aircraft on to the mission (see WW News, March p48). CEI split again intruders. Four hand -held keyboards are connected to the simulator by flexible leads. The Council of Engineering Institutions The keyboards first set the STEG to has attacked the government's believed match the radar parameters and then to intention to hold an enquiry into the set up and control the targets and other Students for industry engineering profession. Sir Charles effects. Marconi, who make the device, say the system is one of many applica- Pringle, the chairman, has told the Sponsored students tions of STEG, which can be coupled to may get an extra Prime Minister in effect that such an £500 a year from their employers enquiry would cause a further period of any continuously rotating pulse position without a reduction in the local author- uncertainty just as the CEI was sorting indicator radar display via an ity interface. grant under a scheme outlined by the itself out after its two years of Education Secretary, Mrs Shirley Wil- dissension. But at although least half a liams, in the Commons on February 3. dozen Of 15 the CEI's members are said From September 1977, she said in to share a Sir Charles Pringle's objections written reply, "payments by employers to an inquiry, among the larger institu- to students whom they wish to sponsor, tions there is a feeling that Sir Charles Components helped or by institutions who wish to give has spoken out of turn. All the signs are again scholarships of up to £500 per annum that yet another big row is brewing. will not be taken into account in the The CEI reached their attitude after a assessment of mandatory awards by council meeting on February 10. They Electronic components is one of the five local education authorities. This will say that in opposing the enquiry they industrial sectors singled out by the be in addition to the amount of income were reflecting the IEE and the IMechE Chancellor of the Exchequer, Denis disregarded under the present arrange- though these bodies had also said that if Healey, and the Industry Secretary, Mr ments which is £185 per annum and now there were an enquiry they would want Eric Varley, for special help as part of an under review for the academic year it to include certain topics. The CEI say experiment "to see whether there is 1977/8." their attitude is that an enquiry is scope for the government to act as a At present a local authority, in unnecessary but that they would co- catalyst in bringing about, in concert assessing a student's income for making operate if one were held. with both sides of the industries con- a grant, does not take into account the It appears, however, that the two cerned, a more rapid improvement in first £185 per annum of income, any senior institutions take a more positive performance .. . holiday earnings, or various pensions attitude to the putative inquiry. On 27th Because each industry sector is and benefits. Later in the year changes January they wrote to Mr Eric Varley different the approach will be different in the rates and conditions applying to saying that they would welcome it, and in each case, but Healey and Varley say mandatory awards, including the £185, that it should cover: the education and in their memorandum to the National will also be announced. training of engineers; how that educa- Economic Development Council, Currently about 7,200 undergraduate tion met the needs of industry; a study responsible for bringing together the students and 2,600 postgraduates are of compulsory registration in other necessary elements to the working of fully supported by employers rather countries; a study of how compulsory the Government's industrial strategy, than by a grant. About a third are registration might be applied in the UK, that "One possible approach would be supported by industrial or commercial and the allocation of certain jobs in to begin in the case of each sector with a concerns and the rest by Government industry to professional engineers. general wide -ranging meeting with departments. Normally an employer The CEI say publicly there is merely a both management and trade unions in makes a choice between giving a student difference of emphasis between them- that sector together with the members £185 on top of his grant or paying him a selves and the IEE and IMechE, but we of the Sector Working Party, under the salary greater than the grant would have are told reliably that the CEI sent a chairmanship of the appropriate minis- been. About 400,000 students in Britain letter to the two institutions, after they ter. This meeting would identify the receive grants totalling £382 million, sent their letter to Varley, asking for an main issues to be tackled. Thereafter, according to the Department of Educa- open apology for putting forward their we envisage that it would be useful to tion and Science, though this includes a' point of view outside the auspices of the hold discussions with individual firms controversial £107 million supplied by Council. From the other side, the or, if particular subjects lend them- parents or spòuses. In 1974 -75 a De- dissenting Institutions have been so selves to more broadly based consulta- partment survey showed that about half ' angered by the CEI's public pronounce- tions, with groups of firms, to pursue the students on mandatory grants did ments that they would now like the these issues." Companies would be not get all the parental contribution, or enquiry to review the CEI itself. asked fOr their views, particularly on £90 for each student underpaid.

www.americanradiohistory.com 4 Wireless World, April 1977 give the impression that some workers has increased 117%, while Bullock's boardroom employees had a special, and therefore manual union membership has higher, status in the eyes of the law. increased 0.1 %. In the four years to 1974 and the engineer Bullock adds that there is no objec- union membership among manual. tion to a staff association or profession- workers actually fell 1.3% but rose 19% al association or any other employee among those off the shop floor. organisation not affiliated to the TUC Lord Bullock himself has acknowledged The `Y' element majority his from being represented on the board that the proposals the of For the moment, a much more likely committee agreed after a year's work provided it is independent of the opening for engineers lies in the propo- may never be carried out. But he is not company but recognised by it. sal that a third element should balance discouraged. The vigour of the debate Trade Unions the shareholder and union rep -esenta- since his report was published on So if the Bullock proposals are imple- tives. This third element, the Y in the January 26 has shown that the call for mented the degree to which technicians now famous 2X+ Y formula, has to be greater involvement of workers in and engineers will be able to contribute company policy decisions which affect an uneven number greater than one, to the better running of their companies must be less than a third of the whole them has suddenly become a political will be largely dependent on the extent board and its membership must be issue. It is likely to remain so. to which they are involved in trade agreed by the other two elements. The Among those who gave evidence unions. The Confederation of British system, says the report "will provide an were the Association of Professional Industry has made clear its bitter important means by which special Scientists and Technologists, the Busi- opposition to Bullock on just these experience and expertise can be ness Equipment Trade Association, the grounds, saying that trade unions speak brought into the boardroom from inside CEI, the Electrical, Electronic, Tele- half workforce. The true for only the and outside the company . . . It may be, communication & Plumbing Union, picture is, however, a great deal more for example, that there will be someone EMI, GEC, Philips Electronic and complicated than the CBI makes out. in the company itself - among senior or Associated Industries, and the United Trade union membership is not distri- middle management who both sides Kingdom Association of Professional - buted evenly throughout industry, and agree could be a useful addition to the Engineers. The EETPU expressed the the smaller the firm the less likely it is to board." strongest opposition to the representa- be unionised. tion of trade unions on the board Of the total workforce, it is true, 50.4% The industry view because they saw a conflict between are members of a union. But in collective bargaining and such repre- The electronics industry has identified manufacturing industry membership is itself with the CBI's view of Bullock. sentation: "It is not the responsibility of 62 %, and if enterprises with less than 200 work people to manage the enterprise The Electronic Engineering Associa- workers are left out of account the tion told Wireless World: "Our input on . . . It is essential that trade unions proportion jumps to 89 %. in the Post The EETPU that will be done through the CBI." retain their independence." Office and telecommunications the thought that the job of the trade unions Latest figures are not available but a figure is 87.9% and in metals and was, through collective bargaining, to quick check of 39 of the companies in engineering 69.4 %. Bullock's proposals, "consider, contest and oppose, if neces- the EEA shows an average number of if adopted, would only affect enterprises sary, the exercise of managerial prero- employees of around 9,6700. Many of but Bullock, unimpressed, employing more than 2,000. In the these are companies with a large gatives," to Bullock, says unions and management "have the others, according trade number of subsidiaries with activities only 20% of same objective: to enable employees to unions represent the across the whole range of electronics. A workforce, and it is because of this that participate in decision- making in the council meeting of the British Radio these firms have been excluded from the enterprise in which they work." Equipment Manufacturers' Association proposals. Reading the report makes you no wiser on February 10 decided that the attitude Against that, these smaller corn - about the future role of the engineer, of many of their members would be panies represent 11 million of the 18 the scientist or the technician in the decided by parent companies here or million people employed in the private proposed new democratic boardroom. It abroad, many of them in the EEA. sector, and two thirds of the total is a fact of modern industrial organisa- number of enterprises. It seems true Size of firms however, their skills and tion, that that small firms are becoming less According to figures for the third are badly needed. experience important the 1968 census of produc- quarter of 1976 at the Business Statistics Most of what Bullock says that is - tion showed that firms with over 2,000 Office at Newport, 48 enterprises in relevant to engineers is about middle telegraph and telephone equipment management. employees then represented only 21% of the enterprises - but it also seems that employ 73,100 people; 252 enterprises in Staff associations count the Bullock idea is not to extend radio and electronic components "Some people have suggested to us that industrial democracy to workers in the employ 126,700; 37 computer firms managers and other professional groups small firms, where the majority of work employ 44,300; and 132 firms in radio, play a particularly important role in the is done. The CBI has not been heard to radar and electronic capital goods running of companies and often occupy complain about that. employ 90,400. No figures are available a unique position between the board for the number of employees in the and other employees - at one point Unionised engineers broadcast receiving and sound repro- representing the company in discus- On the other hand, trade unionism is ducing equipment sector. sions with employees and at another still a more potent force among the being employees themselves - and they wearers of blue than white collars. The Does it matter? have argued that a special seat on the qualified engineer is generally regarded Membership of the EEC, for which the board should be reserved for these as a white collar worker and as such if CBI must hold itself largely responsible, groups. Provided that professional and he is a member of a union, he is one of commits us to some form of worker managerial employees are organised 4.3 million, whereas his manual union participation in the boardroom. How- collectively, as increasingly many of colleague is one of 7.5 million. Engin- ever, the National Enterprise Board has, them are, we can see no reason why eers, therefore, stand less chance than since the report was published, dropped they should not be represented on the manual workers of getting into the its commitment to putting worker board amongst the employee boardroom if Bullock is adopted. But directors on its board, and the Prime representatives. But we do not think the report also notes the increasing rate Minister agreed with the CBI in Feb- that a special seat should be reserved for at which white collar workers have ruary that the Bullock proposals need them on the board by law." Bullock joined trade unions. Since 1948, union not be implemented as long as there is explains that it would be unfortunate to membership among white collar greater consultation below board level.

www.americanradiohistory.com Wireless World, April 1977 55 the pound started to fall this Lenco V.m.o.s. devices "mid- equipment became uncompetitive in dle the market they relied on. of this year" Another blow was that Lasky's stopped selling Goldring equipment when the Japanese put the marketing American Microsystems (AMI) say pressure devices which on direct -drive turntables. use their patented While a belt- driven model might have v.m.o.s. technique will be available withstood this, Goldring's commercially rim -driven around the middle of turntables were too far behind the 1977. "We are in currently the process of times. They could not rely on the kind bringing them into production," said of business BSR had so successfully AMI's president and chief executive built up, supplying turntables for fitting Glenn E. Penisten at a press conference to other sound systems. BSR turntables in February. can even be found in audio systems He described the device as a "short imported from Japan, as in the case of channel n.m.o.s. fabricated in structure Crown, now imported by York Elec- v- shaped grooves which entered the tronics. Goldring also imported Toa silicon surface." Advantages included public address equipment, which had vertical current paths, higher current been affected by import restrictions. density, and higher gain bandwidth To add to everything else Goldring's than was possible with other devices. It premises at Leytonstone were compul- was possible to get 285 from dies each sorily purchased by Walthamstow Liquid -cooled logic. Current mode logic 3in wafer of silicon with a side length of council, and they were faced with the circuits used in Honeywell's new 66/85 145 mils each. In line with the general disruption and cost of moving to Bury computers. Honeywell say the tendency for a reduction in the memory St Edmunds, still a matter of dispute elimination of transistor storage time cell area per bit, such devices could be with Walthamstow council. Cost con- makes each chip five to seven times as used to store 16kbits of information and trol was not too strict, and they spent fast as t.t.l., using half the power. One this could be increased to 65k "before £100,000 there in offices alone, accord- 3in square micropackage there are up 1980 ". Mr Penisten told Wireless World ing to one account. Although staff had to 110 chips, "almost as much circuitry that the speed of the devices was been reduced from 298 to 179 during as a standard I2in square circuit "approaching bipolar speeds, the 40ns 1975, effecting a reduction in the wage board." At the back of each kind of category." AMI also say the bill from £466,772 to £427,622, directors micropackage a liquid cooled heat speed is less dependent on temperature fees went up around £200 £46,629. In exchanger eliminates the need for change, and could work to well at "en- the same year, the Barclay's bank system air cooling. The exchanger is an hanced ambient temperatures of 70 °C." overdraft jumped from £3,650 to oxidised copper diaphragm which, Although others might be producing £160,746, and the company borrowed a when pressurised by liquid flowing discrete products using the technique further £200,000 from the family of Mr behind it, conforms to the surface of AMI were further ahead, they say, in the micropack. has 12 E. Sharf, the president. - Each board optimising "the speed /power relation- According micropacks arranged in four columns ships." It had been thought that v.m.o.s. to an informed source the receiver has now recovered of three. The coolant is pumped in was a dead -end technology because it the money owing to Barclay's and it now remains parallel through each column. The could not be scaled (reduced in size to liquid is cooled in an air -cooled radiator lower silicon consumption), but, said to get back the Sharf money, after which the future of the company seems cabinet with an air blower. If the Penisten, that was wrong. "Our product fails the grim indeed. Most of the money so far cooling system computer shuts is a product that has been scaled and . down automatically. scaled again." The first obtained has been won by selling off the commercial considerable product, a 1K static memory would be stock at a low price and available "probably by mid -year." keeping staff on while there are enough parts in the store to make more. The makes a work- main value of the Goldring name the experimenter "who will ing model" and the exploiter "who rest on the pickup cartridges and styli, develops and produces it." He writes: and it has been suggested Sharf will Goldring falls with that "The pioneering stage was certainly eventually buy the goodwill of the pound the Royal Radar Establishment .possibly liquidated firm. Toa have that of the 'wasted no time in setting up Toa (UK) (RRE) in Great Britain. It must be Ltd, and C. E. Hammond have remembered that the "solid circuit" idea A receiver was appointed on February already taken over the Lenco agency. was no flash in the pan, but the result of 3 for Goldring, which in 1973 was six years' work on miniaturization. The trading so strongly that it offered 1.5 model shown to US military and other million 10p shares at £1.17 each and visitors at the United Kingdom Sympo- closed the offer oversubscribed. The sium in 1957 was intended to indicate day before the receiver, Mr Christopher my views on the logical future of Morris of Touche Ross, was appointed component miniaturization tech- they were down to 8p. "Britain pioneered the niques." The real inventors of the Goldring was heavily dependent on integrated circuit" integrated circuit, in Dummer's opinion, the home market. About 85% of it's were "Noyce and his dedicated team at business was in the UK, according to Fairchild." the Financial Times, and this had a Mr G. W. A. Dummer, formerly super- As a result of reporting the 1957 UK number of effects. The first was that intendent of applied physics at the symposium under the title "Solid Cir- when VAT was increased to 25% they Royal Signals and Radar Establishment, cuits," Wireless World (Nov. 1957 issue) suffered more than firms like Garrard, has no doubt that Britain was the subsequently ran into a spot of bother which now exports something like 70% pioneer in the invention of the integrat- with the lawyers of Texas Instruments of its output. At one time Goldring ed circuit, though not the inventor in because TI, at a date somewhat later stopped producing almost completely the full sense of the word. In a letter to than the report, had decided to use and relied on selling Swiss Lenco the American journal IEE Spectrum "Solid Circuits" as a trade name for their turntables, for which they had an (December 1976) he distinguishes devices (before the term "integrated agency. Another effect was that when between the pioneer "who thinks of it," Continued on page 92

www.americanradiohistory.com Wireless World, April 1977 with two different microphone tech- response up to 15kHz, but the top was Binaural broadcast niques. One used a 10 -in diameter "edgy" and "rather hard" and the perspex disc with two forward- pointing quality was not the best. Results with eccentric omnidirectional microphones this arrangement on a real head were "a mounted either side to correspond with little better with the `stethoscope' mikes First announced BBC programme ear -to -ear spacing. This was used in the but not good enough," commented interview of the cook, but gave too Richard Imison. "Not really up to From a preliminary analysis of listeners' much ambient noise on most inter- broadcast standards ". letters, a large majority of respondents views. The alternative was to mount This was the point where an alterna- got a sound sensation outside of the microphones on the head of the speaker tive had to be found; in fact the project head when listening to "Oil Rig" on in "stethoscope'? fashion - hence an was nearly abandoned, recalls Richard headphones, says the producer, Richard in -head image. Imison. Derek Taylor of programme Imison. The Radio 3 programme was One sometimes found it disconcerting operations then found that good results made with "binaural" microphones when the out -of -head speech, clearly could be obtained using better quality intended for headphone listening and directed at the listener, didn't come microphones in stethoscope fashion - was the first announced broadcast of its from in front where one would have Sony omnidirectional ECM50's were kind in the UK. After reading the first liked it to come from. This lack of centre mounted on a headband with wind- 500 letters, Mr Imison said about a third front speech is not so upsetting on shield and worn at the ears. had experienced good all -round percep- special demonstrations that are intend- Because of the obvious limitations of tion, but of the remaining two- thirds, a ed to startle, such as on the Sennheiser this technique, checks were then made majority had good sound except within dummy head recording, but it can spoil to see how much an artificial head an arc of around ±45° of centre front, the illusion where a speaker is address- actually contributed, starting with a found every- and a significant minority ing you constantly from behind or the head -sized carpet baffle between ear - thing in front and nothing behind. The sides - in real life one would quickly spaced microphones (with and without programme, auditioned for the press six turn to face the speaker. plasticine pinnae!). Directional pro- days before transmission on 8th Fe- perties of the set up didn't seem any bruary, was a 75- minute distillation of worse. In Derek Taylor's words "As 37 hours of interviews and sound effects Why dummy heads weren't used long as the mics were about ear from a North Sea oil rig. This disc baffle arrangement came distance apart, with a baffle between to An interesting choice of location, this, about after three years of experiments give the correct path length, the for while life on an oil rig may possibly by BBC Radio using first the Neumann directional effects were not significant- make for good journalism, its remote- artificial head and then the Sennheiser ly different. Model ears or baffles behind ness from everyday life did perhaps (both pictured on page 336 September the mics did not seem to help in make it a little difficult to relate it to 1974 issue). They say the heads were resolving front -to -back confusion." reality, acoustically. But it wasn't subject to countless tests involving Richard Imison agrees: there is "no difficult to discover the weak point of hundreds of tapes, starting with a large, significant difference" between the the technique, that is, in portraying dead studio and going on to other techniques tried as far as front localiza- studios and the open air, with different frontal sound images, a widely recog- tion is concerned. (They also agree that nised problem with such binaural kinds of material including test there isn't much difference in results techniques. sequences, plays, outside broadcasts, between closed and open -type head- One found the background sensation music. phones either.) They found that while the Neumann to be good and generally located outside Front -to -back ambiguity, it is argued, the head, though almost always taking head was "convincing" and impressive on headphones, it had quality short- occurs with single, transient live sounds place behind. Three kinds of speech For or longer live comings on loudspeakers, in particular anyway. continuous were heard. Studio -produced mono one's head has more of a chance a steep roll off at 5kHz. The Sennheiser sounds narration which, as it was fed to both at assessing direction, either by channels equally, appeared in the head. head and "stethoscope" -type microphone arrangement brought a unconscious minute head movements On location, speech was either in the or by conscious larger movements, and head or out of the head and elevated but the poor frontal localization with never in front (for those at the audition headphones is thought to be due to loss anyway). The baffle and (right) "stethoscope" of such clues. were produced The two sensations microphone pairs described in the text. The BBC have obviously reached a point where they want to experiment with a large audience. But the data from listeners will have to be carefully interpreted as it seems far more likely that those who were impressed with the technique - say on account of well -defined images - would respond more readily than those for whom the technique was disappointing. The ear- spaced microphone with baffle arrangement was made into more permanent form, as in the photograph, and used for the Oil Rig programme, as well as on other occasions including a proms recording. The prom recording, as with others, was not nearly so effective on loudspeakers though BBC personnel found it as good as the conventional stereo recordings, in some cases better. In simple informal prefer- ence tests between conventional and binaural stereo over loudspeakers, the binaural version was the preferred one. - GBS.

www.americanradiohistory.com Wireless World, April 1977 5. Education by radio in Honduras

A case study in electronics technology in a developing country by Michael K. Bates B.A. 4Eng. Tripos, Cambridge)

Electronics technology is at such a level of sophistication that few loo 200 countries can sustain their own elec- kilometres tronics industry. Nevertheless radio is BELIZE an effective means of communication the world over and it has had a significant impact on developing' CG countries. In studying a particular La Ceiba application in Honduras, the author draws lessons Radio about the suitability of San Isidro present technology for use in other "1 :San Pedro El Progreso01 Sula developing countries. Radio Progreso HONDURAS Honduras, Central America, is reputedly the second poorest country in o Comayagua the Western Hemisphere. Although Radiolindia Honduras is less than half the size of the . Tegucigalpa. UK, its population density is low since F SA ...... V i Choluteca !...... /.... the total population is Radio GJP only three .41604. Paz i million, of whom nearly all are Span- ßP ish- speaking Catholics; over two million eke out a subsistence living in rural \-\ areas and are known as campesinos, or peasant farmers. Most of the land is mountainous, containing small but fertile valleys. The wide strip of highly Fig. 1. Map of Honduras showing productive land on the Caribbean the station controls four transmitters locations of radio stations mentioned in with a combined output of over 750kW. seaboard is mostly owned by foreign, the text. banana companies. Meanwhile radio schools were started in fifteen other Latin American Communications systems within the stations country are on the whole ineffective: transmitting in the 540 to countries, including Honduras. 1600kHz band, although is not even all the major towns are linked use also \The radio schools of Honduras have by paved roads, made of the 60m short-wave band and .grown up under the auspices of Acción many villages are the standard accessible only on foot or horseback, v.h.f. f.m. band. Cultural Popular Hondureñá (ACPH), a non -government indepen- telephone links are over -subscribed and Radio schools unreliable, and both the circulation of dent development agency which is Although education is free in Honduras newspapers and the coverage of financed from voluntary sources. There tele- and primary school is, in vision are mostly confined to the theory, have been considerable problems in cities. compulsory it is evident few But radio has proved to be highly that achieving autonomy from the compesinos benefit from it: most have suitable and is the dominant medium for influences of commercial enterprise, been to school for perhaps only a year or mass entertainment, dissemination of political forces and more recently a two and over 65% are illiterate. information and passing of messages. There sector of the Catholic Church, partly are obvious difficulties in sparsely because The success of radio broadcasting is ACPH relies on agreements populated areas in largely due to an influx of cheap bringing together with sympathetic radio stations to buy portable transistor radios, enough pupils to make a conventional air -time for transmission of the schools ownership of school viable, which is often regarded especially if the aim is classes: hence, its effectiveness is as an indication education of social status, and this may of working adults. Use of closely linked to the progress of these account radio for the range at which the average can, however, offer a solution to stations. problems like these. Experimental transistor set is audible. Most broad- education of adults by The system of radio schooling preva- radio began casting is on a private commercial in 1959 with broadcasts basis lent in Latin America from Radio from nearly one hundred local radio originated in Católica in Tegucigalpa, the Colombia in 1947, when Radio Sutaten- capital, and grew successful to encom- za went on the air with a 100W pass 700 school groups by 1964. After 'Volunteer radio engineer with the Catholic transmitter and Institute just forty -five pupils. several years of organizational prob- for International Relations from The idea proved September 1974 to December 1975 as part of the successful and the lems, the system was re- vitalised in 1969 British volunteer programme. organization grew rapidly, until today with the opening by foreign priests of

www.americanradiohistory.com 58 Wireless World, April 1977

Radio Paz, in southern Honduras, and 1110kHz, with a modified 10kW Collins with supplementary material on Satur- the acquisition the following year of on 4920kHz; on both frequencies there day including news and current affairs Radio Progreso in the north by Jesuits. are back -up transmitters, a rare for campesinos. These programmes are As well as transmitting schools pro- achievement for a Honduran station. followed by some 1200 community grammes, then as now recorded in the Radio Paz transmitted on 990kHz using school groups involving about 22,000 ACPH offices in Tegucigalpa, both a modified Contel unit with 4 -1000 students which means that, with their stations followed normal commercial tetrodes in the modulator and 3 -1000 families included, the broadcasts affect schedules. Plans for more comprehen- triodes in the final, and the locally some 100,000 people, around 5% of the sive coverage of the country developed, constructed transmitter for Radiolándia rural population. Each group is guided and in 1974 surplus equipment was draws from the same series of valves but by a monitor who will be a local bought in the USA and shipped to with a single anode -modulated zero grid campesino with approximately one Honduras for in- country construction bias 4 -1000 on the r.f. side to deliver month's training at one of a number of of transmitters and studio facilities with 1.5kW on 1460kHz. For short -wave regional centres. The monitor also plays local help. However this scheme has not broadcasting at both Radiolándia and, an important part in a feedback path of reached fruition due to diverging aims Radio San Isidro BC610 transmitters are opinion via a regional co- ordinator to of ACPH and the Catholic Church, a in use, boosted to 500W with a final 833, the production team in the capital. situation which has also caused Radio a good robust valve which has been Instruction is given in reading, writing Católica to cease passing schools known to withstand accidental use as a and basic arithmetic, progressing to classes. Some expansion of the network light bulb. Even surplus equipment like geographical and cultural knowledge, was nevertheless achieved in 1975 with this looks elegant alongside some but at all stages there is practical advice a low power short-wave installation at home -made transmitters, which have on agriculture, health and home man- Radio San Isidro, La Ceiba, and com- been seen to use wood blocks to support agement. However it is the teaching plete new studios and transmitters for and isolate transformers and domestic method which is significant. Education medium and short wavebands at Ra- light switches on the control panel. It follows the idea, originated in Latin diolándia, Comayagua. But these gains will be noticed that transmitter powers America, of "conscientization ", a very were offset by the closure of Radio Paz are all fairly low: 10kW is the legal upper pragmatic philosophy intended to in June 1975 by the military govern- limit and Honduran stations are at the create a critical awareness of one's ment, following struggles over land moment spared the spiral of ever -rising environment and capabilities within it, tenancy in the east of the country, and powers. Despite the higher radio noise with emphasis on democratic and attempts to regain the broadcast licence levels under tropical conditions, most co- operative processes as means of have so far only brought prevaricative areas are served well by their local achieving communal aims. Hence it is responses. transmitters and there is little adjacent not so much a "handing downwards" of The current disposition of facilities or co- channel interference even at information but rather a combined illustrates the wide spread of techniques night. search by students and teachers in the which occurs in any technology in On the studio side, there is such a context of a localized community to Honduras, ranging from the relatively range of equipment in use as to prohibit find solutions to very real practical sophisticated to the unbelievably crude. more than a mention here. The radio problems. At the more impressive end of the schools central recording studio is well The importance of employing local spectrum, Radio Progreso broadcasts equipped with a double turntable sound radio stations is noteworthy. Firstly the via a new Gates /Harris 5kW mixing desk, two Magnecord profes- schedules of classes need to differ in pulse -width modulated transmitter on sional recorders, three Ampex series 600 various parts of the country to accom -. machines and two high -speed tape modate variations in the tending of duplicators. So too Radio Progreso has crops. Secondly there is a chance for the an impressive line up of Ampex 351 local radio station to become the focal Fig. 2. Transmitter recorders in two fully interchangeable point in a community and give a sense construction in workshops at Radio control rooms serving three studios, of identification to those living around Paz. Cháuteca. On the right is the However, at the other end of the scale, it, through their knowing personally the completed transmitter for the type of station with "mic and two announcers, being able to participate in Radiolándia; in the centre is a copy decks" (one of them probably non- discussion programmes, or merely by of it under construction; on the left is a operational) is common. hearing their own record dedications. BC610 US surplus being converted for short wave broadcasting. Note the tin bath, used to supply cooling water for a Broadcasting policy Fig. 3. A typical radio schools class, dummy load during necessarily brief Radio Schools classes are broadcast making use of a primary school out of transmitter tests at full power. from 4 p.m. to 6 p.m. Monday to Friday normal school hours.

www.americanradiohistory.com Wireless World, April 1977 59 can also be troublesome; for example such as electronics, or to manage the Radiolándia transmitter shows a without them., The extent of radio tendency to trip out on the surge caused ownership leaves no doubt that radio by a local factory shutting down at the broadcasting is both desirable and end of the day. successful in Honduras, yet even an Many stations have no technical staff organization like the radio schools, and hence no regular maintenance, trying to go its own way to suit the repairs being effected only when break- needs of its own people, has to accept down occurs. In a country dependent on the technology of the industrialized agriculture rather than industry and countries and the way in which it is technology, the whole environment is administered. non -scientific and there are few techni- Furthermore, there is no half -way cians and engineers of any description. stage in radio, no "intermediate" tech- There appear to be several reasons for nology. Other branches of engineering, this. The social circumstances of most for example transport, can be upgraded families tend to inhibit rather than by better techniques while remaining encourage a child's natural curiosity; within the framework of traditional the education system, for those who styles: the wooden wheels and axles of benefit from it at all, is biased towards an ox -cart can be replaced by pneuma- learning by rote rather than from tic tyres and a suspension system exploratory and logical deducation without a complete changeover to use processes, and Honduran technicians of a tractor and trailer. But there is no experience particular difficulty in fault parallel process in radio, which is not a Fig. 4. An exercise in Handwriting for a diagnosis. For those few privileged development of a traditional method of Honduran campesino. enough to go on to higher education, communication but a totally new most seeking technical studies would science. It is hard to simplify a trans- travel to the U.S.A: or M-exico, and mitter beyond a basic valve- driven Operational problems perhaps not return. Latin American anode -modulated circuit, yet at present Operation of a radio network in a technicians encounter additional prob- this remains as incomprehensible to developing tropical country brings its lems with language, as a large propor- most Hondurans as ampliphase, Doher- own special difficulties not normally tion of service manuals and ty or pulse amplitude systems: it is just encountered here. There are frequent specification sheets are in English only. another proverbial "black box ". troubles with the campesino transistor Nevertheless, the enthusiasm and So how suitable is present day radios which are often subjected to capacity for hard work of those trying electronics technology for developing extreme conditions of heat or mechani- to better themselves is an inspiration. countries such as Honduras? Despite cal abuse, such as use as a temporary Moreover most Hondurans are capable the extent and importance of radio seat in a bus with doubtful suspension with their hands and adept at impro- systems in such countries, little equip- driven along a rocky dirt road. Some- visation with what materials and ment is manufactured specifically for times a little "home servicing" is knowledge they possess. their needs and often standard equip- attempted too, with the aid of the first ment is unsuitable without modifica- implement which comes to hand, nor- Electronics technology for tions such as tropicalized components mally a machete, and often the back of developing countries or additional cooling. At times equip- the set is lost and the loudspeaker cone One of the dilemmas which developing ment cannot be set up correctly or is eaten by cockroaches. countries face is whether to accept maintained through lack of test gear Broadcasting stations also suffer certain totally imported technologies, and spares: an example is an ampliphase from the climatic conditions. Ventila- transmitter imported into Honduras tion can be a major difficulty: at the which has never given optimum perfor- Fig. 5. Radio schools Radio Paz transmitter in Choluteca, classes are often mance. On the other hand, confusion is held admittedly one of the warmest parts of in ordinary campesino houses caused when a range of test equipment such as this the country, shade temperatures in one near Choluteca. is specified which is not normally used March and April regularly exceed 40 °C, and even after increasing the size of blowers it was necessary to run the transmitter without sides and play a domestic fan on the modulator chassis. Concurrent with temperature problems are often those of high humidity: a particuarly bad case is in La Ceiba, where the damp salt -air has affected even the BC610, designed for military and tropical use. During the wet season, lightning strikes cause frequent disruption of service and damage to transmitters and for this reason a folded unipole (caged) aerial configuration, in which the base of the tower is earthed, has been adopted for m.w. radiation at both Radio Progreso and Radiolándia. The studio equipment is not normally subjected to such extreme conditions, but in studios without air conditioning there are problems of overheating in turntable and tape- recorder motors, and much valve equipment such as line amplifiers and compressors has to be blown. Fluctuations in mains voltage

www.americanradiohistory.com 60 Wireless World, April 1977 outside a laboratory; the list of "required equipment" for tape -head alignment on one model of recorder One hundred years ago included a valve voltmeter, a low -distortion oscillator and a spectrum analyser. The station concerned did not No, Wireless World was yet a thing of the when the first really effective "talkie" film, ", with Al Jolson, was a possess even a multimeter. future in 1877, but the groundwork for the "The Jazz Singer twentieth tremendous success. The Western Electric American development of the electronic Nevertheless, the Latin century was being laid and already, a sound system - the Vitaphone - used 16in broadcast equipment market is boom- hundred years ago, an impressive list of disc turntables driven at 331/2 r.p.m. from the ing; a periodical is produced, in English theoretical and practical invention was in same constant speed motor system as the and Spanish, for free distribution to any existence. Computers, relays, transformers, film projectors. But this method of synch- radio personnel requesting it, and many diaphragm microphones, motors, fuel cells ronism was soon to be supplanted by the of the larger electronics companies now had all been made and the theory of wave "sound track" (sound -on -film system) intro- have agencies in Central and South propagation was well advanced. duced in the same year by Fox Movietone News. a quieter and somewhat less America. In April 1877, Thomas Alva Edison filed a On U.S. patent application for the design of the distorted note, but highly significant to audio in mind possible size of Bearing the carbon microphone, which immediately took engineering, was the invention in 1927 of the the market for electronic and radio precedence over the efforts of Reis negative feedback amplifier by H. S. Black of goods in developing countries, it seems (diaphragm type - 1860) and Bell (magnetic Bell Laboratories. appropriate to consider some of their - 1875). The "other end" of a speech These are just a few of the significant basic requirements. It would indeed be a communication system was attacked by E. inventions described in a new book "Elec- noteworthy advance if there were W. Siemens, who applied for a German patent tronic Inventions 1745 -1976" by G. W. A. available a cheap, simple, foolproof on the moving -coil loudspeaker in De- Dummer just published by Pergamon Press cember, 1877. The device used the transistor radio, in a tough impact -re- at £4.00. This contains mainly brief accounts now -familiar motor with a circular coil inventions in electronics but firmly secured of important 'sistant case with back moving in a radial field. also has some interesting graphs showing and control knobs, with reliable battery A rather more publicized centenary this historical trends. For example, it shows that contacts and protection against incor- year is the invention by Edison of the in the 200 years from 1745 to 1945 some 106 rect battery insertion. Suitable circuitry phonograph (or gramophone) using tin foil electronic inventions originated in Europe might include integrated circuit i.f. and wrapped round a hand -cranked cylinder. against 66 in the same period in the USA; but a.f. stages and ceramic filters, with This patent was applied for in December, in the mere 31 years from 1945 to 1976 the servicing simplified to the level of quick 1877. situation was reversed with 32 inventions for ago, 1927 was an -block replacement or perhaps Moving on to fifty years Europe and 85 for the USA. circuit important date in the history of the cinema even a complete change of encapsulat- ed, throwaway electronics. The criteria of low cost, robustness under exacting conditions and misuse, reliability and ease of servicing by non -expert personnel also apply to broadcasting equip- Connectors in the Amphenol range include the r.f. types to DEF standards - the 27GB Subminax, the ment, appearing more important than 31GB series quick disconnecting connectors and high performance and sophistication of (Literature ) weatherproof type. A set of data sheets the 82GB'C' design. Such ideas as solid -state relays, covering all these is now obtainable from ball -race bearings lubricated for life, Received Amphenol Ltd, Thanet Way. Whitstable, Kent CT5 modular construction but with far more 3JF WW407 attention given to connectors, and Distance measurement techniques over a period of Power supply price list is now available from Weir, generously rated components immedia- 5000 years are illustrated on a new wall -chart from including bench types, a unit for use with tely suggest themselves. A plea might Tellurometer, which has been involved in only the microprocessors and a range of card supplies. Weir later, microwave methods of measurement. well be added for VU meters with Instrumentation Ltd, Durban Road, Bognor Regis, Tellurometer, Oakcroft Road, Chessington, Surrey W W401 flexible pointers and unbreakable Sussex KT9 1RQ WW408 end -stops. Video cassette recorder control unit is made by Capacitors and semiconductor devices by RIFA are Current technology can adequately for use with the Ampex ACR -25. A Crow of Reading fully described in a catalogue, now available. A very if which is satisfy these requirements suitable leaflet describes the function of the unit, full range of capacitors is offered and the production and marketing policies are designed for remote control of the programmed are rectifiers, timers and driver/ recorder. Crow of Reading Ltd, PO Box 36, Reading, semiconductors adopted. Future demands from deve- interface circuits. Rifa, Fac, S -161 11 Bromma, RG 1 2NB WW402 loping countries are likely to be for Sweden W W 409 television as well as radio equipment in Demonstration panels for teaching electronics are Power supplies by Gardners are detailed in a series ever -increasing quantities, but under- produced by Taran International. The panels take of recently published leaflets. Chargers for the form of large mimic diagrams with the circuit nickel- cadmium cells, 50Hz d.c.- to -a.c. inverters, standing and ability to use the techno- printed on the front, the components being plugged logy can only come slowly. In the regulators and d.c.- to -d.c. converters are all in. A leaflet can be obtained from Raynham Road, described and the leaflets can be obtained from meantime, these countries require the Bishop's Stortford, Herts CM23 5PG WW403 Gardners Transformers Ltd, Christchurch, Dorset, sort of equipment which can be used BH23 3PN W W410 Component lead forming machinery from Eraser successfully in the present environ- International is described in a "Wyber" catalogue. The Honduran campesino needs Speaker drive units, crossovers, materials and ment. Hand -operated and automatic forming and crop- accessories for loudspeaker construction are listed illustrated and several implements his indestructible transistor radio for ping tools are in a new catalogue. obtainable from Badger Sound and for education, and for cleaning printed boards are described. Eraser Services Ltd, 38(a) St Andrews Road South, St entertainment Parade, East International Ltd, 2/3 Hampton Court Annes, Lytham St Annes, Lancs FY8 1PS at 10p per must hope that progress in electronics Molesey, Surrey KT8 9HB WW404 technology will move towards provid- copy. ing it. And there might even be Prices of measuring instruments in the Electroplan something in it for us. catalogue are brought up to date in their February Pressure transducers of various types are made by' 77 list, which briefly describes additions to the Bell & Howell who describe them in four bulletins. range from Advance, Solartron, Weston, Bryans. Types covered are: thin -film types. high- output Telequipment and Systron- Donner. Electroplan versions with amplifiers, marine and industrial Ltd, PO Box 19, Orchard Road, Royston, Herts SG8 transducers with electronics in a bulkhead- mount- Acknowledgements 5HH WW405 ing case and flameproof transducers. Bell & Howell Ltd, Electronics and Instruments Division, Lennox Hants RG22 4AW WW411 Thanks are due for the considerable assis- Printed- circuit manufacture by the Nevin group is Road, Basingstoke, which includes a tance provided by R. J. Levey, engineer for the subject of a new brochure, wall -chart of board design information, protective General electronic components, instruments, kits P. with the British ACPH; G. Nairne, now finishes and metric conversions. Nevin Electric and books are all listed in the Maplin 1977 Council; and the Catholic Institute for (Holdings) Ltd, Arkwright Road, Poyle Trading catalogue, available at 50p from Maplin Electronic International Relations. Estate, Colnbrook, Bucks SL3 OHJ WW406 Supplies, PO Box 3, Rayleigh, Essex SS6 8LR.

www.americanradiohistory.com Wireless World, April 1977 61 N- stable multivibrator the last mentioned, between two and thirty pulses can be obtained. This has This circuit produces a fixed number of been realised using a single CD4001 i.c. Circuit pulses when triggered. Applications A pushbutton can be used instead of a include number indicators, frequency trigger pulse for manual circuits. multiplication, and number loaders. A Dr K. Padmanabhan, Ideas monostable feeds a gated astable and, University of Madras, by adjusting the frequency control of India.

+5 to 12V

10k<

r b 3 ^ l--- On J U U l Voltage /current meter n pulse 100k 2 switch 2n The circuit arrangement shown enables ,U U U a single pole two way switch to be used FOn-I. in place of the two pole, two way type which is usually required when one meter indicates both current and voltage. Resistors R1 and R2 are the meter shunt and series resistances respectively. The change of output voltage due to MONOSTABLE GATE ASTABLE R1 being switched in and out will usually be negligible if the circuit is included in the feedback loop of a Variable band -pass filter stabilised power supply. S. V. Essex, Sometimes it is required to have a and output of the all -pass network. The London W.14. high -Q, bandpass filter which is sum becomes zero when there is exactly adjustable over a wide frequency range 180° phase shift over the cascade, and without an appreciable change in Q, or thus the overall gain approaches half R1 more particularly, without the loop - the open -loop gain of amplifier A. At gain becoming greater than unity other frequencies the gain tends which causes oscillation. With this towards unity. circuit the centre frequency can be Because the frequency determining adjusted over a 100:1 range whilst components only affect the overall maintaining Q> 100, and over smaller phase -shift and not the gain, there is a frequency ranges, a Q of up to 104. In no danger of having a loop -gain greater addition, a two -phase output is also than unity. If the two -phase output or available. large frequency range is not required Two cascaded all -pass networks, B one R can be fixed. The Q is adjusted by and C, each have a 0° to 180° phase R2, and with the values shown gives the variation, and unity gain at all circuit a 20Hz to 2kHz range. frequencies. This cascade is driven from J. M. Worley, a third operational amplifier whose Colchester, feedback signal is the sum of the input Essex.

R2 Mh 82k "Ar 25k log 10p --I l- 100k* -----100k* 100k*

100k* 100kdE cos sin output input R1 R3 100 k 1k 100k I- 1u. 1k Jog log

68n 1,u. 100k 68n o sin output

* denotes close tolerance

www.americanradiohistory.com 62 Wireless World, April 1977 Ripple eliminator Earth warning indicator

This shunt regulator circuit virtually low levels of collector- emitter voltage. Line removes all mains ripple without using The zener diode should be operated a large capacitor, and is inherently with enough current to make its 2M2 is short- circuit proof. The regulator dynamic resistance significantly less 1/2W ideal as a stabilized supply line for audio than R1. Transistor Tr3 may be a power preamplifiers and other applications type or a Darlington. The Miller Si where a precise voltage level is not capacitor should be large enough to important but freedom from ripple is. stop high frequency oscillations. The circuit's simplicity is due to silicon P. S. Bright, transistors" which can operate at very Christchurch, New Zealand. 150k 0 22 1/2W 150V

Equipment frame or casing Neutral

This simple circuit gives a warning if the earth wire is disconnected from the chassis of an instrument. It is particularly useful for oscilloscopes which may be left in a hazardous state when the earth wire is purposely disconnected to avoid hum loops etc. The neon is normally extinguished, and flashes if the earth is not connected. R. H. Troughton, Gatwick Airport, Surrey.

Simple noise generator impedance is approximately 50052. Four the recovery of a 500Hz signal from stages of gain have been used to noise of similar frequencies. The circuit Phase -lock loop techniques, for the minimize instabilities and provide the will operate at maximum ne e output recovery of low level information from maximum noise amplitude without into a load of 1.5kS2. For smú -r load noisy signals, have become increasingly reaching the limits of output excursion. impedances, the noise level must be important. This note describes a simple The a.c. coupling between stages reduced or the 100011.F power supply noise generator in which both signal eliminates offset compensation and capacitors increased to prevent and noise levels are continuously and provides low frequency roll -off. High oscillation. independently variablé from zero to frequency roll -off is determined by the The author wishes to acknowledge maximum. The only point requiring gain of each stage and varies slightly the contributions of Dr T. G. L. care is the positioning of the transfor- with the noise level control. Output Shirtcliffe, Mr J. E. Nixon and Mr P. D. mer to avoid 50Hz hum. The voltage_ noise is essentially "white" from below Turner to the project. doubler supply may be replaced by any 50Hz to above 5kHz. This range was J. E. Morris, convenient configuration. The input selected as appropriate to demonstrate University of Wellington, New Zealand.

100k NOISE 10k

100k

741

output 1p. 10k 741 I h- +/ 1µ 10k Ok 10k

www.americanradiohistory.com Wireless World, April 1977 ;3

We complete the open circuit in your money supply.

In almost any industry Alex. Lawrie will bridge these days, the gap between your creditability gap by convert- invoicing and getting paid is ing up to 75% of your invoices widening so fast it's causing cash into ready cash - immediately. flow problems even for sound You inject it into your business - companies. immediately. And together, you It's the creditability gap. and Alex. Lawrie generate a It affects the quality of work sound cycle of money supply. and frustrates plans for improv- Let's face it, if you've.got a ing productivity and profits good business going in this through expansion. It prevents critical economic climate, you good companies from forging have no alternative but to protect ahead. it. Phone the Alex. Lawrie Here's the professional Regional Manager and talk to answer to the problem. him now. Or send for details.

OM IN P

Alex. Lawrie Factors Limited

London Region: (Ol) 6260484 Northern Region: Manchester (061) 834 7415 Midland Region: Banbury (0295) 51126 Southern Region: Southampton (0703) 22968 Belfast Branch: (0232) 22350 Scottish Offices: Glasgow (041) 221 3637 Edinburgh (031) 2264599 Registered Office: Beaumont House, Beaumont Road, Banbury, Oxfordshire OXI6 7R N.

WW -051 FOR FURTHER DETAILS

www.americanradiohistory.com 64 Wireless World, April 1977

Gould Advance offer a comprehensive range of generators - and every one's a winner. Take the J3A and J4A Test Oscillators, for example. Both PG52B feature a choice of four different outputs, and both give you * *_ *0( 4*** outstanding performance at a very ,aae a' a, modest price. I° Then there's the SG200 RF Signal Generator, offering 7 ranges from 160 kHz to 230 MHz, and excellent frequency stability with fine setting to within 1 kHz. The Generation Game There are Pulse Generators too. waves. And the PG52B; not really The PG58A, for instance: one instrument, but up to eight an inexpensive general -purpose modular units in one Main Frame. instrument providing single or There are twelve modules to choose double pulses as well as square from, enabling you to generate an extremely wide range of pulses and pulse patterns. And if you need still more versatility, there's a 16 bit Word Generator and a Gate Module to provide even more complex pulse patterns. Look into the Gould Advance range for yourself. You'll find that it's hard to beat for price, performance and reliability. In fact, we've guaranteed every, instrument in the range for noe less than two years. ' Didn't we do well! 'L1

Gould Advance Limited, ü-, k5 Instrument Division, Roebuck Road, Hainault, Essex IG6 3UE. Tel: 01 -500 1000 Telex: 263785 GOULD ADVANCE WW -073 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 65 VIEWDATA 3 - Operation of the system: terminals and codes

by S. Fedida, B.Sc. (Eng), M.Sc., F.I. E.E., A.C.G.I. Post Office Research Centre

Part 1 of this series, in the February side of the cradle. Once contact is user may enter the entertainment 'page issue, gave an introduction to View- established, the computer transmits a direct by keying *3230. An example of data, with mentions of earlier sys- first frame, which requires the user to one of the pages in the entertainment tems. Part 2, in the March issue, dealt enter a user number. When this has sequence was Fig. 6 in the February mainly with applications. This article been done Viewdata offers the first issue. In later models of the 'terminal, now describes the overall arrange- index (shown in the February issue, p. use is made of the calling key on the ment of the system, the codes used 32). keypad. This calls the Viewdata com- and the Viewdata terminal. The action is now transferred to the puter automatically and switches over keypad. On this the user keys -in his user to the modem without the user's

Fig. 1 gives an overall view of a Viewdata number and any further responses. intervention. The keypad may then be connection. The home terminal, shown Suppose the user wishes to obtain used as previously. at the bottom left hand side, comprises a information about entertainment acti- The design philosophy of Viewdata domestic television set, a telephone vities for a given day of the week. The which has been dealt with in the first and a Data instrument, a Viewdata adaptor banks këypad. The actual assembly is shown Fig. 1. Overall picture of connections in in 2. Two types of keypads proposed Fig. Viewdata, showing the telephone in Figs. 3 and 4. The basic are shown system at the top and the home and is Fig. 3; this provides the ten keypad office terminal at the bottom. numerals, and í symbols and keys for automatic dialling, if installed. Fig. 4 is an alphanumeric keypad. This contains Viewdata in addition to the above, the complete Telephone computer upper case alphabet, punctuation marks exchange and symbols like £, %, /, arithmetic and algebraic symbols and cursor control A typical Viewdata terminal characters. Strowger, for the office, the Viewdataphone, is crossbar at the bottom or TXE shown schematically exchanges right hand side of Fig. 1. This consists of a Viewdata terminal and a self- contained telephone instrument. A typical Viewdataphone was shown in the March issue. The Viewdata com- Local telephone puter is shown at the top of Fig. 1, exchange notionally connected to a variety of data banks, either direct or through the ,switched telephone network. 75 bits /sec As mentioned in the February issue communication between the terminal t v set and the Viewdata computer is at a rate 1,200 bits /sec Other of 1200 bits /s from computer to termin- customers al and 75 bits /s in the opposite direction. More details of this arrangement will be given later. In order to establish a connection to the Viewdata computer the user dials Dial or pushbutton the telephone number of the computer telephone as for a normal telephone call. When the connection is established the computer generates a high pitched tone (frequency 1300Hz) which is heard in the telephone receiver. The user then Viewdata presses a button marked "data" on the phone telephone set, which switches the Vey pad telephone line from the telephone set to a modem (modulator -demodulator). EQUIPMENT IN THE HOME EQUIPMENT IN THE OFFICE The telephone receiver is then set by the

www.americanradiohistory.com 66 Wireless World, April 1977 except for the actual codes transmitted over the line, where a slight change is made to comply with International Standards Organization recommenda- tions. The table of codes used for Viewdata is shown in Figs. 6, 7 and 8. Fig. 6 shows the joint Viewdata and teletext codes for alphanumeric characters only. This differs from earlier versions in the following characters:

Column Row Was Is now 5 11 5 12 C'/z 5 13 1 5 15 6 o 7 two parts of this article referred 11 '/4 to the Fig. 2. Home terminal for Viewdata, 7 12 need to keep the cost of Viewdata down II with television set, telephone (right) 7 13 iI 3/4 to very low levels, both on the terminal and keypad on the table. 7 14 side and on the computer usage side. Indeed, unless the cost of using the Note: The top, left -pointing, arrow is used as computer facility is kept substantially an assignment statement; the lower, right - below that of using current computer pointing, arrow means "go to "; and the sign time -sharing systems, the whole project is used as a terminator and for special may not become viable. This therefore functions. Note also that the arithmetic operator x (multiply) postulates the use of a distributed used in Viewdata is shown as x (lower case computer system, so arranged the x), while the minus that sign ( -) is code 2/13 and the exponentiation majority of users may have access to a sign is code 5/14 shown as r. nearby computer centre, at the cost of a local telephone call for the connection Fig. 4. More elaborate, alphanumeric, plus a correspondingly modest charge v keypad with a variety of other symbols. for the use of the computer and the information provided. The resulting network is typically as shown in Fig. 5. Users are within a local. call distance of their computer centres, shown as rectangles. A cluster of local computer centres is grouped under the Fig. 3. Basic keypad used in control of a regional for a Viewdata centre the terminal,providing ten purpose of data gathering and distribu- numerals and a few other keys. tion. A national data centre controls the operation of the whole system and distributes to each regional centre new carried out over the past two years from information, news and data updates. a large number of centres in the UK and Regional centres also accept informa- on the Continent. In all these tests the tion of regional or local interest and public switched telephone network was distribute this to the local centres. used to connect up to the experimental Viewdata system based at Martlesham, The Viewdata terminal near Ipswich, and transmission diffi- Display format. The display format of culties have been very rare. Fig. 5. A distributed Viewdata network, Viewdata is identical with that of The character codes used for View- showing local computers, regional teletext, i.e. a page consists of 24 rows of data and teletext are also identical, centres and national data centre. 40 characters each, each character being generated by a 5 x 7 matrix with Regional data,news National data, upper and lower case, character round- news ing, graphics symbols and colour. Thus. a great deal of the electronics in a terminal may be common to Viewdata and teletext, the differences being Regional primarily concerned with the addition- centre al functions needed in Viewdata, the different modes of transmission appli- cable to these two systems and the different contraints appertaining to the Regional different communications media centre involved. In the case of Viewdata the data enters the terminal via the telephone line at relatively low speed, and, as the probability of data corruption is quite low, little is needed for the purpose of Local Local Regional clusters computer 2 computer 3 error detection and correction. Indeed, 100,000 customers each extensive Viewdata tests have been

www.americanradiohistory.com Wireless World, April 1977 67

1 1 1 b7 o o o o 1 1 1 1 I. b7 o o o o 1 bb o o 1 1 o o 1 1 f r b6 0 0 1 1 0 0 1 1 o 1 o 1 o 1 1 b5 0'1 I( t b5 o 1 o 1 o o 1 Col Bits b7b6b5b4b3b2b1 Oa la 2a 3a 6a 7a Bits b7b6b5b1/4b3b2b1 o 1 2 3 4 5 6 7 Rowol R 0 0 0 0 0 S P 0 (aî P- p 0 0 0 0 0 (NUL) (DLE)

0 0 0 1 1 A Q a q !"1 alpha " - graphics 0 0 0 1 1 u B R b r red red ® 0 0 1 0 2 . 2 0 0 1 1 3 £ 3 C S c s alpha graphics F 0 0 1 0 2 green green ] i 0 1 0 0 4 $ 4 D T d t graphics 0 1 0 1 5 N. 5 E U e u 0 0 1 1 3 aÿellOw 7 'i 1 1 8, 6 F V f v 0 0 6 algue^ graphics ® LT 0 1 0 0 4 0 1 1 1 7 , 7 G W g w blue blue e x 1 0 0 0 8 ( 8 H X h alpha" graphics ® 0 1 0 1 5 magenta magenta u L 1 0 0 1 9 ) 9 I Y I y t alpha" graphics ® 1 1 0 10 J Z j z 0 1 1 0 6 0 *: cyan cyan 1/4 1 0 1 1 11 + ; K.4- k alpha^ graphics , L Yz O 1 1 1 7 1 1 0 0 12 < t u white white ® u i

1 1 m 3/4 1 0 13 -= M-. conceal 1 0 0 0 8 flash display ® 1 1 1 0 14 . > N t n-

1 1 1 1 15 S1 ? O t$ o I contiguous / 1 0 1 9 steady 0 graphics ® ' u 5 Fig. 6. Codes for alphanumeric characters only, separated 1 0 1 0 10 end box graphics as used in both Viewdata and teletext. i ' i

1 0 1 1 11 start box (ESC) ® u a normal black us 1 1 0 0 12 Fig. 7 shows the graphics and control height background characters use in teletext, as at Sep- double new 1 1 0 1 13 background tember 1976 *, the conventions being as height hold II before, that is: 1 1 1 0 14 (SO) 1. All character rows start in the release "steady ", "alphanumeric white" and 1 1 1 1 15 (S1) graphics us "unboxed" condition without control characters. Fig. 7. Codes for graphics used in teletext. 2. Control characters shown are displayed as spaces, but control whether alphanumeric or graphic characters are displayed and what colour is used. 3. Alphanumeric characters in columns

4 and 5, i.e. all of the upper case letters b7 o o o o 1 1 1 1 and a few others, may be displayed next I b6 o o 1 1 o o 1 1 1 O 1 0 1 to graphic symbols without an inter- bs 0 1 0 vening space. 7a Bits b7b6b6 b4b3b2b1 1 2a 3a 4a 5a 6a While the intervening space conven- Rowol 0 a is tion following control character 0 0 0 0 0 NUL - 1..Iji" essential in teletext, it has been accept- alpha" graphics , ed in Viewdata for the sake of unifor- 0 0 0 1 1 DC1 red red % mity, although it is not really essential alpha" graphics [y[am and imposes undesirable constraints on 0 0 1 0 2 DC2 green green W the page format. 0 0 1 1 3 DCg Additional control characters have 7 r ayel ow graphicsyel ow % recently been added to teletext to g provide enhanced display facilities. The O 1 0 0 4 DC4 ablue" blueics IC convention is IC alpha" graphics it "intervening space" 0 1 0 1 5 ENO somewhat modified and made less u magenta magenta E alpha" graphics onerous, although not all its undesirable 0 1 1 0 6 ® u cyan cyan C 1111 effects are eliminated. graphic s The new control characters, which 0 1 1 1 7 ® alwhite white t C may be applied equally in Viewdata are us conceal in four groups: 1 0 0 0 B BS CAN flash display i Contiguous /separate graphics. Codes 1/9 1 1 HT steady and 1/10 in teletext, 5a/9 and 5a/10 in 0 0 9 N : cgraphss i 5 Viewdata. This provides the choice of separated 1 1 : end box graphics symbols filling the whole of a 0 0 10 LF graphics Li character rectangle, or only six discrete and separate dots. 1 0 1 1 11 VT ESC I start box Ill :I Normal height /double height. Codes 0/12 black 1 1 12 FF : and 0/13 in teletext, 4a/12 and 4a/13 in 0 0 I height background ¡ Viewdata. This provides for the optional double new C I 1 1 0 1 13 CR display of alphanumeric characters in the height background % standard size, i.e. within the normal char- cursor hold 1 1 1 0 14 home ® graphics il 'Broadcast Teletext Specification. Published IS2 release jointly by the Broadcasting Corporation, Indepen- 1 1 1 15 Il dent Broadcasting Authority and British Radio Equipment Manufacturers Association. Fig. 8. Control and graphics codes used in Viewdata.

www.americanradiohistory.com 68 Wireless World, April 1977 acter rectangle or stretched vertically to and 1/15 in teletext, 5a/14 and 5a/15 in Cursor. The cursor in Viewdata is a double height, the width of each character Viewdata. This allows a limited range of symbol which shows up on the display and the intervening spaces between char- abrupt display colour changes in a row as a bright rectangle, filling of acters remaining the same. whereas normally the space there is at least one space an upper case alphabetic character. It between rectangles with different display Black background /new background. The colours in the same row. may be switched on and off, as required. background colour of the character rectangle by a switch on the terminal or on the is normally black. Whenever the new keypad, or by remote control from the background control character 1/13 in tele- The graphics and control characters computer. It may also be moved any- text or 5a/13 in Viewdata occurs, the display in Viewdata are show in Fig 8, but where over the display either manually colour then obtaining is adopted as the new before these are looked at in detail, the background colour. by using special keys on the keypad or use of a cursor in Viewdata should first by remote control from the computer. Hold graphics /Release graphics. Codes 1/14 be explained. The cursor has many functions.

b7 o o Fig. 9. Complete b6 o o o o set of Viewdata b5 o 1 codes. columns 2a, 3a, 6a Bits 070605b4ó30201 0 1 2 2a 3 3a 4 4a 5 5a 6 6a 7 7a and 7a Rowol for graphics and NUL P columns 0000 o S o P p 4a and 5a for the alpha" graphics 0 0 0 1 DC) A red Q red a q controls.

0 0 1 0 .2 2 B alpha" graphics DC2 green R green b r alpha" graphics 0 0 1 1 3 DC3 3 C c yellow S yellow s alpha" graphics 0 1 0 0 4 DC4 4 D T b blue blue d

ohi 0 1 0 1 5 ENO alpha" graphics 5 E magenta U magenta e u alpha" graphics 0 1 1 0 6 8 6 F V cyan cyan V alpha" graphics 0 1.1 1 7 7 G white w white g w

1 0 0 0 8 BS CAN 8 H conceal flash X display h X

1 0 0 1 9 HT contiguous 9 steady Y graphics y separated 1 0 1 0 10 LF J end box Z graphics z

1 1 1 1/4 Fig. 10. Bloch 0 11 VT ESC s K start box k diagrams of (a) a

1 1 0 0 12 FF L normal black Viewdata 1/2 I height background I terminal and (b) 1 1 O 1 13 CR M double new height background m 3/4 a teletext cursor hold terminal, 1 1 1 0 14 home N graphics n showing video release connections to 1 1 1 1 15 o graphics o 1 the television set.

COLOUR TV RECEIVER COLOUR TV RECEIVER Tuner To c.r.t. Tuner To c.r.t. RGB RGB 111 111 Colour R Video i.f. strip Colour G Video decoder G Lt. strip N., amps 1 decoder G . amps B B t B

Video input

Electronic Line Electronic video video change -over Outputs G change -over 04A- switches Outputs G switches

VIEWDATA TELETEXT DECODER DECODER UNIT UNIT INTERFACE BOARD INTERFACE BOARD Switch control Switch control (á) (b)

www.americanradiohistory.com Wireless World, April 1977 69

1/4 DC4 Device control 4. Used to switch off both tape recorder and hard copy unit (a) 1 /8 CAN Cancel. Used to delete line of character. This code is used only from terminal to computer 1/9 ESC Escape. Used to indicate to terminal that TELETEXT the character DECODER UNIT following is from another set of control codes (in this case the control code set 2a to 7a of colours or graphics) 1 /10 IS2 Home. Returns cursor to character position 1 on screen Video input (top left hand side)

Graphics characters. The graphics and colour control characters for Viewdata are shown in Fig. 8 columns 2a, 3a, 6a, 7a for graphics and 4a and 5a for the controls. For line transmission the ( b) control characters of 4a and 5a, are always preceded with ESC (code 1 /11). VIEWDATA On receipt of this code the terminal DECODER UNIT reverses the polarity of bit 7 from 1 to 0, thus restoring compatibility with teletext and places the characters in store. The graphics characters in columns Line input 2a, 3a, 6a and 7a are fully compatible Video input with teletext and are treated in the same way when displayed. The complete set of Viewdata codes is shown in Fig. 9.

Block diagram of terminal. A block diagram of a Viewdata terminal is shown in Fig 10 (b). This shows the Fig. 11. Block diagrams of (a) a teletext interconnection between the Viewdata Basically it gives a visual indication of terminal, terminal and (b) a Viewdata decoder and the video amplifier of the the position on the screen at which the to the showing r.f. (u.h.f.) connections colour tv receiver. An interface board next character sent by the computer television set. When the computer contains the electronic switch which will be displayed. from tv new page of information to the provides the changeover sends a reception to Viewdata. The input to the terminal, it first sends a code which puter and user which resembles a returns the cursor, whether visible or pointer (but more about this later). Viewdata decoder unit is, of course, the 'telephone line. By contrast Fig 10 (a) to the "home" Control characters in columns 0 and 1 not on the display, connections position which is at the top left -hand must comply with ISO7 for line trans- shows the teletext decoder (Wireless World, December 1975, pp. side of the display. Thereafter, as each mission and so far 15 have been character is entered, the cursor is allocated. Additional characters in the 563 -566). The input to the teletext moved one character position to the same columns may be allocated in decoder is obtained from the i.f. input. right. The position of the cursor, future as more facilities are included. Fig 11 shows a similar set of connec- whether this is switched on or off, is The control characters wnicn nave so tions where the entry to the television recorded by two counters, a character far been allocated in the experimental set for display purposes is the aerial counter and a row counter, which system undergoing pilot trials are: socket of the tv receiver. In Viewdata maintain at all times a knowledge of the only (b) a u.h.f. modulator has to be position at which the next character is Col/ Name Function added, wnereas for teletext (a) an to be displayed (and entered on row additional tuner and i.f. strip must be' 0/l NUL None -used for timing purposes provided. Hence the considerably memory). Thus we talk of the cursor as 0/5 ENQ Code sent by computer to it it were a real entity, whether or not it .terminal to initiate automatic greater attraction of a built -in decoder is displayed. terminal identification in the case of teletext. By moving the cursor by means of the 0/8 BS Back -space. Moves cursor one (To be continued) controls available (see below), the character position to left computer may position it to where the, 0/9 HT Horizontal tab. Moves cursor `one character position to right character is to be entered. Thus it is 0/10 LF Line feed. Moves cursor one line not necessary to send a series of spaces position down or more blank lines are where one 0/11 VT Vertical tab. Moves cursor one required, or where a row of characters is line position up shorter than the full length of the line. 0/12 FF Form feed. Erases screen and The cursor also enables the computer to moves cursor to top left hand overwrite a portion of a display without side of screen (position 1) The journal you like cursor to having to first erase and retransmit the 0/13 CR Carriage-return. Moves Wireless World's average circulation position on same line whole page. first last year was up 4,604 copies to 69,220 at the Combinations per month, according to the Audit The cursor may also be used Device of these char- terminal for editing purposes, e.g. when 1/1 DC1 Bureau of Circulations. Overseas control 1 acters will be composing messages or doing calcula- readers, in countries from the USSR and 1/2 DC2 Device used to switch USA the Falklands and Seychelles, a feature of the to tions, or to point at control 2 on tape recor- bought 21,000 of these. On average, for display it is desired to manipulate. In 13 DC3 Device . ders and hard the past eight years 200 more readers this context the cursor is a powerful control 3 copy devices have joined our circulation each month. communication channel between coin- remotely

www.americanradiohistory.com 71) Wireless World, April 1977 minimum of Sunspot Cycle 20 was Arrays for 5.8 and 10GHz which can reached during July 1976 with a maxi- more readily be based on dishes have mum for Cycle 21 predicted around proved more successful. World of 1981. The problem of obtaining gains (reference dipole) of above about 14dB Licence totals on 432MHz is underlined in the results Amateur The Radio Regulatory Department of of the 10th national antenna -gain the Home Office are currently distri- measuring contest held in the United buting (as renewals fall due) the new States last year. The leading designs Radio form of amateur licence (see February were: eight times 16- element Yagi issue). Two reasons are given for the (K2CBA) 16.1dB; four times 13- element changes: "(1) To give you greater wooden -boom Yagi (K2UYH) 16dB; flexibility to pursue each aspect of G3JBL -type 28- element long quad -loop amateur radio without having to apply Yagi (K1LOG) 15dB; 15- element to us each time for authority to do so; WOEYE -type Yagi (K1LOG) 11.8dB. On (2) we, in turn, expect to be able to keep 1296MHz a 7ft dish aerial (WA2FGK) within the Government's staff ceiling registered a gain of 24.3dB; a over the next few years while main- G3JBL -type 28- element long quad -loop taining the issue of amateur licences Yagi (K2UYH) 17.1dB. without undue delays." Such events indicate that many amateurs have On January 1, 1977 the number of an inflated idea of the new -style Class A and B licences were: forward gain of their aerials, possibly due to high front Class A 15,956; Class B 6202; total /back ratios. Space and propagation 22,158. How Martin Sweeting, G3YJO, of the Uni- the number of old -style licences versity of Surrey's Oscar telecommand built up to over 29,000 during the past In Brief station reports that early this year one few years is shown below: The death has occurred of Austin of Forsyth, OBE, G6FO, for many years the NiCad cells in the upper half of end- end- end- end - the Oscar 6 spacecraft (launched in 1968 1971 1974 1976 editor of Short Wave Magazine. Before the war he operated from Newport, 1972) "took a turn for the worse" and Class A 13.082 14.082 15.304 15,956 may fail completely; if this happens it is Class B 1,352 3.012 4,966 6.142 Monmouth and for a time from North likely that the battery will be irretrie- Class AIM 2,589 2,666 3.424 4,173 Devon; more recently from Maids Class B/M 132 545 1,549 2,463 vably damaged. He appeals for strict Morton, Buckinghamshire. . . . A Class F/M - - - 23 working party is being set up by adherence by all amateurs to the Television 186 214 277 318 the operating schedules if Oscar 6 is to Totals 17,341 20.502 25,520 29,075 RSGB "to study the whole Society in survive the year. Additional telemetry depth with a particular relation to the information received from the satellite organisation of the Society's head- would be welcome and should be sent Amateur TV News quarters, the organisation of Council to: UOS-AMSAT, Department of Elec- Mr R. C. Hills, G3HRH, Chief Engineer and its committees and the inter -rela- tronic Engineering, University of Sur- (Transmitters) of the IBA, is the new tion between HQ, Council and Com- rey, Guildford, Surrey. Incidentally, the President of the British Amateur Tele- mittees "... . Seychelles now use the UK FM Group (London) state that vision Club. He succeeds Mr R. S. prefix S7, and the prefix S8 has been many amateurs in the Thames Valley Roberts, G6NR, who recently complet- allotted to Transkei... . A mountain area have been puzzled by the ed his four -year term of office. BATC top in the Antarctic has been named 144.8MHz wideband transmissions from has recently published a new 110 -page "Cima Radioamatori" by a recent the UOS -AMSAT telecommand station, book "A guide to amateur television" Italian expedition that kept in daily G4DVT, at Guildford. This station (non- members £1.75 post paid from touch with northern Italy with the help operates daily for up to 25 minutes at a BATC, 64 Showell Lane, Penn, of a number of Italian amateurs . . . time, repeating every 100 minutes Wolverhampton, Staffordshire). Endorsements for five -band operation between 0530 and 2300 GMT. P. Blakeborough, G3PYB, is con- are now made by the RSGB for the GB3LBH, the 10GHz beacon station structing a vision transmitter for British Commonwealth Radio Trans- at Romford, Essex recently increased 1296MHz in addition to his 100 -watt mission Award, the British power and now uses a 200mW Gunn 625 -line transmissions in the 432MHz Commonwealth Radio Reception oscillator on 10.1GHz; it is regularly band. Alan Morris, G4ENS, of Luton is Award and the DX Listeners' Century received at distances up to 25km trying to raise interest in proposals for Award. . . . The ARRL National Con- including some obstructed paths; this an amateur tv beacon on 432MHz and vention for 1977 is being held (June 3 -5) beacon may be used for studies being later a 1296MHz repeater capable of in Canada at the Sheraton Centre Hotel, carried out by students at Imperial handling tv signals. Toronto: special get -togethers are College. A 144MHz beacon (possibly planned for visiting British and "ex -G"

9H3ML) may be set up in Malta. The amateurs.. . . Attention was drawn last 1.3GHz beacon at Andover (GB3AND) U.H.F. aerial gain September to the attractions offered by with a power of 5 watts e.r.p. has been Des Clift, VK2AHC (formerly G3BAK) crystal ladder filters for the home heard in Devon. who has operated on every available construction of s.s.b. filters. Now, after 28MHz c.w. and s.s.b. activity periods band from 1.8MHz to 10GHz has extensive investigation of this type of are now being run by the RSGB on the commented in Electronics Australia on filter, J. A. Hardcastle, G3JIR, has first Sunday of each month (1200 -1800 the problems of reproducing aerial reported: "If a single outstanding factor GMT, 28.0 to 28.1 and 28.5 to 28.6MHz). designs from constructional articles, were to be chosen from all the mea- A new 28MHz beacon is expected to be noting that the element dimensions surements which have been made, it set up at Lannion in Brittany, France, given by different constructors for the would be that it is almost impossible not with the callsign F3THF on 28.227MHz; same bands often show surprising to produce a filter of some sort, if it also hoped that 50MHz beacons may differences. For 1296MHz he has guidelines are followed. This should be be established at Lannion and also at attempted with only moderate success sufficient to encourage even the most Gibraltar as part of a new series of to build 8- over -8 skeleton slot array; hesitant to try to construct their own 50MHz transatlantic tests. 34- element long Yagi; four square helix; crystal filters." It is now thought likely that the conical reflector with dipole feed, etc. PAT HAWKER, G3VA

www.americanradiohistory.com Wireless World, April 1977 On the bench or in the field. Model 1455.41 digit accuracy, exclusives that enable us to offer stability, resolution. £ 260 you 'this kind of accuracy, flexi- for Here is a 41/2 digit DMM that bility and dependability £260 won't tie you down. It's Data For versatility and value you Precision's Model 1455, the 41/2 won't find anywhere else, carry digit bench instrument that goes off a Data Precision Model 1455. into the field with you. Or for the same specs and features in a unit designed for line use The 1455 gives ±0.02% only, we offer our Model 1450 for reading ±-0.01% f.s., ±1 digit basic are specs you'd expect from lab only £240 They're both a lot of accuracy for 6 months. A five units costing twice as much. multimeter. function multimeter with large 1/2" But the extraordinary 1455 gives high, 7 segment planar display you still more. With its built -in and 100% overrange, it measures rechargeable NiCd battery, it is Farnell 100 µV to 1000 VDC, 100 µV to completely portable, meaning 500 VAC, 100 milliohms to 20 you can have this in -lab accuracy, International Megohms; AC and DC current anywhere you go. Farnell International Instruments Ltd 1 microamp to 2 amps, AC The 1455 incorporates 4DH response, 30 Hz to 50kHz. These Wetherby West Yorkshire LS22 Tri- Phasic ' Conversion Cycle Telephone 0937 3541 Telex 557294 and our patented Isopolar ' Refer- encing, just two Data Precision

DATA PRECISION ...years ahead

WW -056 FOR FURTHER DETAILS

www.americanradiohistory.com 72 Wireless World, April 1977 When did you last buy your Ford direct from Henry?

them in Even if you could get a available. We stock Fro: ITT Instrument Services, 1 car straight off the Dagenham depth.And we fully document them Edinburgh Way, Harlow, Essex. production line, chances are it in a comprehensive catalogue Telex 81525. wouldn't be the model or colour available for the asking. Please send me your instrument you wanted. No account to open (if you and power supply catalogue. And the same limits on choice have one with ITT Electronic apply if you're buying electronic Services, then you have one with Name instruments and power supplies us), no second bests to put up Company direct from the manufacturer. with. If you deal direct with ITT Just phone, write or telex over Address Instrument Services though, it's a your order. different story. Then sit back and admire our We select the best instruments easy handling and remarkable turn [Tel. No. from all the manufacturers' ranges of speed. ITT instrument services Our catalogue features the full range of Racal counter timers and the 9913 and 9915 frequency meters. Its a range that uses I.s.i. The onlywayto buy. technology to bring you the ultimate in reliability combined with the features you need for your measurement requirements. They're Harlow(0279)29522 all stocked in depth and can be with you before you can say 99!

WW - 093 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 73 Electronic rhythm unit

Interfacing the M252 and M253 circuits, described in the March issue by A. Battaiotto and G. Ronzi, SGS -Ates Application Laboratory, Agrate, Italy

So that the rhythm section may be ning of the bar or stops the rhythm. The can be divided into two broad groups, inserted into an electronic organ, a assembly is carried out on two printed namely, sounds consisting of damped, signal must be available which indicates circuits, one contains the sound gener- sinusoidal waves, like drums, and those whether one or more keys on the organ ators and preamplifier, and the other consisting of damped white noise, like key board have been played. This signal, contains the supply, the M 252AA, the cymbals. - which we call the key played,starts the . variable clock generator and the mon In the first category we can include rhythm section. When a key is played ostable circuit for driving the down- the bass drum, high bongo, low bongo, the rhythm section can be arranged to beat lamp. conga drum and the claves, for which start at the beginning of the bar (touch The circuit can be divided into four the basic circuit is shown around the or key operation), i.e. the playing of a parts, the sound generators, the varia- twin -T parts of Fig. 13. key ,removes the reset from the clock ble clock generator, the down -beat This circuit is a simple twin -T oscilla- and from the M 252 or M 253. monostable and the encoder. Operation tor with active c.m.o.s.* element kept Alternatively it can be arranged to of the M 252AA has already been slightly below the point of oscillation by start at any point in the bar (contin- described in the first part, but some the pre -set resistor. To obtain the effect uous or silent operation) i.e. the rhythm further details will be given toward the of different frequency instruments you generator runs continuously, but its end of this description. only have to select the right values for output is enabled by the "key played" the capacitors. The potentiometer also signal. In continuous operation, there- Sound generators regulates the length of the damping, so fore, the down -beat indicator is indis- The generators are designed to repro- that longer or shorter sounds can be pensable as it allows the first key to be duce as faithfully as possible the sounds obtained. played when the bar begins. made by percussion instruments. They The command from the M252AA is A third method (continuous free applied at points BD, HB, etc. As the running) allows the unit to operate Fig. 11. Connections for incorporating M252 produces a square' wave, the RC without any of the keys. This is playing into electronic organ. Rhythm unit A discrete -component oscillator circuit is done simply by selecting a rhythm on parts are within shaded enclosures. available on request. the push button array of the rhythm section. Neither the touch key nor the continous silent key must be on when Keyboard this method is used. Fig. 11 illustrates the insertion of the electronic rhythm section into an organ. The two parts within dashed lines are details of the rhythm section, of interest for the connections to the keyboard of the organ.

Rhythm section with 15 rhythms Continuous -silent and 9 instruments This rhythm section, realized with the M 252AA, is programmed with 15 different rhythms in such a way that each rhythm can use up to a maximum of eight of the nine instruments available, Fig. 12. The 15 rhythms programmed are the waltz, jazz, waltz,. tango, march, swing, foxtrot, slow rock, pop rock, shuffle, mambo, beguine, cha cha, bajon, samba and bossa nova, and can be brought in one at a time by means of the key board. The instruments available are the bassdrum, snare drum, claves, high bongo, low bongo, conga drum, long cymbals, short cymbals and maracas. The three controls are volume, tone and tempo. In addition, a switch allows the rhythm to be started at the begin-

www.americanradiohistory.com 74 Wireless World, April 1977

+5V

VCC Out R22 Bass drum (BD) 22k R36 To X (SD /CL) 22k R21 10k D1 High bongo (HB) Low bongo (LB) C2 Maracas (MR) 10n R37 100k STOP 5 Short cymbals (SC) TEMPO 0 1M Ts CI R20 o Lpng cymbals (LC) log C22 6 220n 22k Conga drum (CD) - 1 R38 300n VGG © 22k -12V r

R56 500k

with M252 R48 R49 only 68k 68k 68k 68k 68k 68k 68k 68k

C33 4n71 C24 C25 C28 C29 C34 C35 10n 10n 12n 12n 1n5 In5 18n 18n

C6 R5 C18 R26 D C26 R43 D C30 R50 C36 R61 BD 150n 27k HB 33n 27k 3 LB 39n 27k CL 4n7 27k 56n 27k 10

R49 R30 R43 R45 R46 R51 R53 R54 R62 R65 1R2k 10k 100k 22k 10k 390k 12k 10k 390k 12k 10k 1M 12k 47k 10k 390k

100k +12V +12V D4 L1 Tr +5V 100mH C7 C21 SD 100n 220n 7 R57 C31 C+ 10k 220n R11 L14 5 2k2 Rio 9 R32 2 8 22k C 1M 4n~1M 4 R56 C32 8 390k 300n 50n T C10 -12V 10k 4n7 I 4 Output LC log R33 R35 C20 25k O 4k7 56k 300n lin VOLUME C11 R13 TONE 330n 10k SC

r`la C12 R15 10k i'T. 1M R18 Tri -Tr5 BC208B MR C13 220n D6 a7ok D1 - D7 IN914A NAND gates are 1/4 of 4011A, Ri6 1-D7 10Ó k C14 22k T 300n VDD = +5V, Vss = 0V

Fig. 12. Use encoder circuit of Fig. 13 with this M252 Below is show a conventional three -rail power supply 15- rhythm unit. (Rhythm selection details for M253 circuit circuit for rhythm generator. will appear in part 3.) Circuit includes twin -T oscillators.

www.americanradiohistory.com Wireless World, April 1977 75

I. . _I

A Ó 0 ' c ° ñ

m F m u m v1 i I i 1 1 1 7 i I i 1 % C a r f o t5V

Fig. 13. In c.m.o.s. encoder for use with ses progressively and then decreases Encodert M252 rhythm unit single-pole switches like the others. This effect was achieved Circuit, Fig. 13, uses HBF4012A be used with if can resistors desired. by means of the integrator- differentia- four -input NAND gates, and HBF 4001A (See part 3 for M253 rhythm selection.) tor circuit which allows controlled two -input NOR gates. If simple sing- amplification of the white noise. The differentiator (e.g. C6 R7) must be le -pole switches are to be used rather snare drum is obtained by adding a introduced so that a fairly short pulse than an array of two -way switches, 15 arrives at the oscillator, which should signal of the second type, i.e. a metellic resistors of 100k12 must be inserted as not interfere with the damping of the sound, to a drum sound. Each sound indicated. starts oscillation but should be sufficient to on the positive edge of the control pulse. activate the oscillator itself. Resistors Rhythm section with 12 rhythms R27,, etc, keeps the input at earth in the Variable clock generator* and 8 instruments absence of a command, otherwise it An alternative rhythm section was would remain floating since the outputs The clock generator is realized with two c.m.o.s. gates and the tempo regulated realized with the M253AA in which 12 of the M252AA are open -drain types. different rhythms are programmed, In the second category are the long by means of a potentiometer. When closed, the switch sets the generator in each rhythm being able to drive simul- cymbals, short cymbals and maracas, taneously a maximum of seven out of for which the basic circuit is shown such a way that the output remains at 1 and at the same time the M252AA is the eight instruments available. bottom left in Fig. 13. Transistor Tr2 The 12 rhythms programmed are the charges the capacitor C8 during the reset. By opening this switch the bar begins i.e. the output immediately goes tango, waltz, shuffle, march, slow rock, short command pulse. This capacitor pop rock, cha to 0 so generating the negative edge swing, rumba, beguiné, then discharges through R12 and the cha, samba and bossa nova. These base of Tr4. necessary to cause the first command pulse or pulses to be produced by the rhythms can also be combined; two The white noise produced by the more can be selected simultaneously. zener effect of the base -emitter junction M252AA, according to the rhythm selected. The instruments are the same as for of a transistor is applied at the base of the preceding unit with the exception of Tr4. during the discharge of Cg, Down -beat* the conga. The adjustments too are therefore, transistor Tr4 can amplify this is This too is made with two c.m.o.s. gates. equivalent, and the assembly noise. The level of amplifica- simply carried out on two printed tion, however, will follow the discharge The down -beat pulse supplied by the M252AA is too short to light a lamp. circuit boards (£6 inclusive from M. R. curve of C8 and therefore a damping Sagin, 23 Keyes Road, London NW2). effect of variable length will be obtained Also it occurs at the end of the bar The sound generators, variable clock . according to the values of C8 and R12. whereas the lamp should be lit at the beginning. This monostable, Fig. 12 top, generator and monostable for the The inductor and the capacitor at the down -beat, are the same as for the M252 collector of Tr4 allow partially selective which starts on the negative edge i.e. at the beginning of the bar, operates with rhythm section. amplification to be obtained so that The keyboard has the function of some harmonics can be boosted and an an auxiliary transistor in such a way that the lamp lights for a sufficient connecting the snare drum or the claves effect more similar to the instrument to the third output of the M253AA, being simulated can be obtained. period of time to indicate the beginning of each bar. according to the rhythm selected. Almost all the instruments used in t Alternative encoder circuits are possible using this ryhthm section start immediately mechanical switching, a diode matrix or t.t.l. gates. * Alternative clock generator and downbeat Copies of circuits may be obtained from the with maximum amplitude and decrease have been designed using t.t.l., h.l.I. and circuits editorial office. exponentially. The only exception is the discrete components. Copies are available from maracas simulator,whose signal increa- editorial office. To be concluded

www.americanradiohistory.com 76 Wireless World, April 1977

+N ) CURRENT DUMPING VL= (ZLIIZIIIZ4)(Val (110') (3) Letters to AMPLIFIER Simplification yields the combination required to make VL independent of N(V0I)

The recent controversy on the current ZIZ¿ 1 dumping amplifier (December 1975 issue and i.e. subsequent letters) Z - 1 Z (4) the Editor has not come up with any 1 + consensus as to whether it is just an elegant A ZIIZ2IIZ311Zg^ method of applying feedback or whether For an infinite gain op -amp, equation 4 there is an element of feedforward in it. It can reduces to Walker's original form. To be shown quite easily that with an amplifier confirm this result an amplifier was made of finite open loop gain (and consequently with a variable open loop gain (A). This finite feedback), the current dump trick variation in open loop gain was obtained in achieves much more than feedback alone an elegant manner by connecting a possibly could. An expression is derived potentiometer across the compensating below for the current dump configuration terminals of the operational amplifier used. given by Mr Walker and Mr Albinson in The circuit was designed to have minimum Wireless World (Dec. 1975), but the amplifier distortion for an open loop gain of considered has a finite open loop gain and a approximately 52dB, corresponding to 20dB finite input impedance. With these cons- of feedback. Fig. 2 shows the results which traints, and assuming an arbitrary non -linear confirm that increasing feedback beyond a transfer function for the current dump block, particular value makes the distortion figure an expression can be derived wherein it can worse. In fact with all the current dump be shown that the error in the current elements removed and the same amount of THE WARDEN REPORT through Z4 is exactly compensated for by the feedback (20dB), the distortion measured current through Z1 provided the conditions 3.1% against the null reading of 0.4%. This Having read your leading article "WARC given in equation 4 are satisfied. should remove any doubt about the talk" (December 1976) and the follow -up effectiveness of the method, and Mr Walker article "Who is warden over the Wardens" Vo, =A(V-V1) (1) and Mr Albinson of the Acoustical (January issue), we feel it might be informa- Manufacturing Company should be congra- tive to your readers to learn of the mobile tulated on innovating a most elegant method V,_(Z,aIz31Iz;° radio industry's reaction to these two (2) for removing distortion and for eliminating z 3 zl NZV U ) articles. thermal problems associated with the output We should confirm that the EEA were stages of high power audio amplifiers. given an opportunity to examine carefully D. M. Divan and V. V. G hate, the Warden report, an industry working Philips India Ltd. party was set up and its view of the report was placed before the Home Office Mobile Radio Committee. The industry was critical of many sections Z1 of theort but all companies supported, Vol 27 inter alia, that part of the Warden report which called for additional spectrum for land Vin mobile services. It should be emphasised that this report was probably the first of its kind with anything like its depth, and was a major contribution to the understanding of the many factors which affect the use of the spectrum by all mobile radio users. Subsequently, one of our member companies has produced a report (the Pannell report) which presents a view supported in large measure by the industry and demonstrates that something like 100MHz, is required between now and 1999. [See leader in February issue - Editor.] Fig.1 It is quite understandable for a regulating 2.6 B department to take a rather conservative 2.4 attitude but, as they are aware of the views of the. users and the industry, we have 22 confidence that the Home Office strategy at A Feedback vs. distortion WARC will result in these views carrying 2.0 O Open loop gain vs. distortion considerable weight. 1.8 B In conclusion, we ought to point out that Output level 300mV your "Warden" article is misleading in three c 1.6 matters. Mr Warden has not, as far as we are 1.4 aware, (a) completed a report on broadcasting; (b) reached the conclusion that there ¢ 12 was "no further need for any o allocation to 10 mobile radio above what it had already got "; (c) said that any further channels which did 0.8 become available should go to the Post 0.6 Office" - indeed, we understand that the Fig. 2 Post Office were asked to go to 12.5kHz 0.4 channel spacing and to prove further need for more spectrum. o2

We trust this will be helpful in explaining I o 1 1 I the EEA view on this very important matter. 10 12 14 16 18 20 22 24 26 28 J. W. Carlton, FEEDBACK (dB)

Chairman, Mobile Radio Committee, I 1 I t I I I I I Electronic Engineering Association, 42 44 46 48 50 52 54 56 58 60 London WC2. OPEN LOOP GAIN A (dB)

www.americanradiohistory.com 77 Wireless World, April 1977 obvious differences in sound quality then to detect high order distortion products the data should be produced as a contribu- under heavy masking by low order products ADVANCED PREAMPLI- tion to the art. Our own work appears to and noise. In essence, the ear will react FIER DESIGN show that if a skilled listener has the favourably to 1st order distortion products in opportunity to listen repeatedly to a signal the order of one per cent, provided all higher order products are virtually non existent. The letter from Mr Watts in your February while the time delay is switched in and out Although it has been long accepted that the issue and the answer from Mr Self is notable of circuit, he will eventually come to detect a ear does favour colouration derived from low for two factors the abrasive language of shift of about 3 milliseconds (rather than 5 - order products, the relative weighting ratio the former's criticism and the surprisingly milliseconds quoted above) but these (for a given degree of colouration) has never temperate reply from the latter. Frankly, I, observations only serve to confirm that the been established and I believe has been too, could find much tò fault in the design delay limit specified by CCIR is a reasonable consistently under -estimated. but, of course, there are ways of expressing it, choice for the ordinary situation where repeated comparison is not possible. If one applies this theory to high quality aren't there? are radically Mr Self's design is James Moir, amplifiers, the design rules My main criticism of virtually conceived by a hi -fi James Moir & Associates, altered. Bipolar transistors become that it is over -engineered, of the has not been too Chipperfield, useless in low level stages because enthusiast who apparently transfer characteristic. costing process when putting Herts. complex exponential involved in the Negative feedback (even locally applied) together the elements of a circuit. The tends to be a disadvantage because inno- principle of Occam's Razor is also the essence cuous low order distortion products are of good design technique. He has also converted to lower level, but audibly more overlooked the simple facts of life that - apparent, higher order ones (Ref. Scroggie) the extremes to which one may go in DISTORTION despite and the output impedance of devices designing equipment of this type, the AND THE EAR becomes a significant source of distortion. that are inherent in all pro- aberrations Space allows no further elaboration but a gramme sources available to the domestic After reading D. Self s article, "Advanced simple example of this alternative approach user are likely to be far greater than those preamplifier design" in your November issue, is given in the form of a unity gain buffer introduced by even the most modestly I feel obliged to comment on the general stage. Anyone interested in conducting a designed reproducing equipment. attitude to audio amplifier design taken by comparative listening test (on a high quality Mr Watts is guilty of worse errors, in But the majority of WW contributors. At the core stereo system) between this circuit and the dealing with pure theory, opinion, and of this approach is the assumption that any standard emitter -follower may find the lack dressing it up as fact. Let me take one loss of realism, originating from amplifica- of correlation between measured t.h.d. and and since he seems to invite example - tion within the reproducing train, is a direct audible colouration interesting. here's another from me. If he is challenges, function of t.h.d. Consequently with each A. King, a high grade pickup able to produce for me new design appears detailed analysis of t.h.d. Glenroy, amplitude cartridge capable of the sort of performance but, from the user's point of Victoria, Australia. input when loaded that he linearity correctly view, the lack of any comparative listening insists should be observed in the equalised test is painfully obvious. input stage and will deliver consistently A striking example of the ear's peaks in excess of 200mV, then there is .£5 dissimilarity to a t.h.d. meter would be the ready in my hand for any charity he cares to attempted measurement of distortion from LINEAR PHASE name. an audibly inferior preamplifier of a sinewave Reg Williamson, signal recorded on disc. Wow and tracing LOUDSPEAKERS Norwich. distortion combine to swamp the amplifier's contribution by orders of magnitude, but the As Mr Gorman pointed out in his letter in amplifier's imperfections are all too obvious the February 1977 issue, the arguments through the reproduction of voice or music arising from the advocacy of linear phase from the same source. loudspeakers have generated much interest, If an accurate model of the human audio heat and correspondence. May I be allowed AURAL SENSITIVITY TO processing path existed, it would be possible to add to the last by enquiring of your other to design with confidence circuits that correspondents what importance should be PHASE introduced the theoretical minimum of attached to the position of the listener who audible colouration. Unfortunately, this has set up his linear phase loudspeakers in As comment on the two letters in the model does not exist and any major the normal stereophonic configuration? February issue may I summarise some advancement in amplifier quality can only be In the diagram (overleaf) I shall assume that comment that I have made many times on achieved through extensive, practical listen- two linear phase loudspeakers (which I in a the subject of the effects of phase shift ing comparisons of all types of active devices assume may be regarded as point or at most monaural channel? and circuit configurations. line sources) have been situated at points .A is fed If a wideband speech or music signal After experimenting for several years in and B of an equilateral triangle ABC of side, into a transmission system the system this direction and through the careful say, 2 metres. The listener being conscien- design must ensure that the low frequency analysis of designs proved to be audibly tous (and also being a point receiver) situates components and the high frequency com- superior, the one common factor to emerge is himself at C. Unfortunately before he can ponents arrive at the output end at about an appreciation of the ear's uncanny ability begin to appreciate the benefits of a linear the same time. Clearly there will be some loss in sound quality if the low frequency components arrive today and the high +15V frequency components arrive tomorrow. MPF131 Thus there must be a limit to the differences 40673 in the transmission time that can be allowed. etc. The CCIR standards define the permissible differential time delays for high quality systems, typically the 5kHz components may be delayed by around 5 milliseconds 100 mV with respect to the 1kHz reference signal input level before a quality change is noticeable. If we (mistakenly) choose to express this permissible time delay as a phase shift, it is some 9000 degrees, that is, the start of the 5kHz component can be delayed by about twenty five cycles before the shift is aurally Selected for noticeable. The wave shape at the system 4 -BmA Idss output then bears no relation to the -15V waveshape at the system input. ALTERNATIVE BUFFER If anybody has any evidence that time STANDARD BUFFER delays inside the CCIR values can result in

www.americanradiohistory.com 78 Wireless World. April 1977 back has failed, for an instant, to reduce the 6 signal to its normal working level. Several NORTH cures were suggested including a generous SEA D D overload margin. COMMUNICATIONS May the current vogue and justifications for large overload margins arise from a I have read with interest your report in the possible subconscious reaction to hearing December 1976 issue (p.44) of Mr L. Buttriss's i.m. distortion which is then irrationally talk to the World Offshore Oil Conference. justified in terms of some supposed large How easy it is to knock those who are pace transient output from the pickup? How in a setting and breaking new ground and who practical world would this transient find its occasionally fall short of the standards which way on to the record, and if it could be Mr Buttriss sets. Considering that Mr present will not the normal mechanical Buttriss's organisation is only following constraints ensure it is never produced? along behind others who are in the front line, Why in fact does virtually all discussion of as it were, 1 suppose he is in a very good high fidelity reproduction no assume signifi- position to develop hindsight, which as we all cant defects in the recording amplifiers etc? know is a splendid quality. Were this really true there are, and have long If Mr Buttriss was a little nearer been, the front practical designs for near perfect line action he might recognise the difficulties reproduction amplifiers. with which the British Post Office have had Be that as it may; the recordist does not, to cope, not to mention systems indeed designers phase configuration, a malevolent deity he dare not, shrink back from some like my organisation whose clients found S means of volume compression displaces him a small distance metres along even if it be no themselves at the mercy of a takeover the line EF to C' Trivial geometry shows that more than simple manual control. That is his exercise near to Mr Buttriss. in tool for avoiding the overload these circumstances there is a difference in situation and if It is always easy to generalise on the he has done his path lengths AC'- BC' equal to job properly may I ask what failings of others, unspecified of course, but distressing signal, capable of upsetting a not always the wisest policy if your liveli- +(1 +6)2 +(1 6 pre -amp, can come off a record via \/3 - \/3 -6)2 metres. a pickup? hood depends to a large extent on the said The truth of the situation is more likely others. that pre -amps Thus, assuming a speed of sound of, say, are generally badly designed W. T. Brown, 330m /s, a displacement of 10cm will produce and, transistors being deceiving little beasts, Macclesfield, approximate cancellation of a steady signal they react in ways that are not expected. Mr Cheshire. of wavelength 20cm, i.e. a frequency of Self would not have it that the first part of his 1.65kHz, and will do funny things to the pre -amp was, as Mr Watts claimed, a phase phase of signals near that frequency. shift oscillator, but I can safely say from Of course the listener should not have recent practical experience that similar allowed himself to be displaced from point C, arrangements are quite capable of oscillat- TALKING BOOKS APPEAL but the malevolent deity who is also cunning ing at h.f. or H. and showing h.f. oscillation provided him with two ears placed about on part of an I.f. cycle when fed with a normal A few years ago you were 20cm apart. Thus the poor listener sine wave. They have in fact good enough to (who, mutual publish an appeal conductances far beyond those of valves, and for servicing volunteers for being conscientious has avoided the trap of the British these increase more or less directly Talking Book Service for the inducing phase distortion by, say, waggling with Blind. current flow and have no As a result many new volunteers were his head from side to side) is left in the clear inbuilt enrolled. position that the only way he can effectively limiting mechanism as has a valve, which As the service has expanded so has enjoy the linear phase of the stereophonic limits in most circuits just as soon as the grid the need for servicing volunteers and I would ask set -up is to block -up one of his ears and becomes positive. Without limiting, a tran- anyone who can repair a simple locate the other at C. sistor may well start an h.f. oscillation; the tape recorder, and can spare a little time, N. G. circuit comprising interalia stray to Shipley, reactances, contact the address London, in which its own widely variable given below for further EC4. capaci- details. tances will figure. This of course may These establish a form of blocking oscillator. Talking Books mean a lot to the If the 'blind people who crucial reactances are within the transistor use them and their gratitude for the help given be servicing chip the designer has a fearsome problem on AMPLIFIER DESIGN his hands. volunteers amply compensates for the loss of a few hours spare time. Here Mr Watts chooses a policy of avoid- The address to contact is: British Talking ance by using an i.c. in the no doubt well There is clearly an interesting disputation in Book Service for the Blind, Nuffield Library, founded belief that these have been the making regarding pre -amplifiers between the Mount Pleasant, Wembley, Middx. HAA subject of such exhaustive Messrs Watts and Self (February letters). I designing pro- 1RR. Telephone: 01- 903 -6666 cesses, so may particularly note that both seek upwards of that they be marketed as A. J. Smale, being 40dB overload margin. Why? There is no vice free, that he needs fear no London N21. point in it unless the main amplifier and the unwanted side effects. Mr Self attacks on the loudspeakers could also handle 40dB over- grounds that i.cs have greater noise, which load. But in a real world what would happen? seems to be yet another airing of the If such a sound level could be produced it is irrational oversight of the way in which noise Corrections more than likely to permanently damage the in later stages is lost in the amplified noise The diagram below was inadvertently ears, a fearful consequence of some such from earlier stages. omitted from Mr Graham Nalty's letter little faux pas as dropping the pickup. However, the most intriguing feature of Mr in the February issue on the Advanced Reality calls for a limitation of peak power Self's design and defence concerns the 1 n 5 Pre -amplifier Design. capacitor from base to emitter of the input and that limitation is best achieved by a Also, the heading "Re- invention" means which minimises the resulting and transistor. Why not to earth, if as claimed, it was omitted from Mr K. inevitable distortion. More by accident than is an r.f. bypass? May the truth be that by H. Green's letter (top of page 60). Apologies design valve amplifiers working in Class A some chance it is solving some instability to Mr Nalty, had that useful property. problem? Certainly by trying out a number of Mr Green and our readers. Mr Sundqvist (February issue) is now preamp designs I have learnt to realise RIAA spelling out for us the details of i.m. stages are exceedingly prone to strange Treble Bass distortion and it is becoming more generally problems. But then a warning was issued by de- emphasis boost apparent that transistor design needs far J. Linsley Hood in the September 1971 issue greater thought and attention to detail if i.m. of Wireless World concerning two, let alone and other distortion is to be kept at three, transistor high gain circuits. Perhaps innocuous levels. In particular he .is making we do not learn and continue to fall into the us aware of the danger of feedback over same traps. several stages of undefined bandwidth in that C. Streatfield, a transitory condition will arise of a Poole, maximum signal at some point where feed Dorset.

www.americanradiohistory.com Wireless World, April 1977 79 Stereo coder

1 -Choice of method /oscillator stability by Trevor Brook

A practical design for a high quality and S signals respectively. Monophonic decode a perfect multiplex signal is coder suitable as a test instrument is receivers continue to produce only the presented with signals having the five described. Apart from the audio M signal as audible output thus giving following departures from ideal is filtering, inductors have been avoided the system its compatibility. shown in Fig 2: and a compact board layout produced. - amplitude error between the M and S A v.h.f. unit for servicing checks on Decoding signals receiver performance could also be To retrieve the stereo information -phase error between the M and S used by demonstration showrooms to involves a decoder which can take the signals feed programmes of their own choice form in Fig. 1. The reduction in channel -phase error in the pilot relative to the to stereo tuners. separation if a decoder adjusted to 38kHz suppressed carrier. The require- Part 1 examines the stereo multi- ment for pilot phase accuracy is sub- plex system and establishes tolerance A +B stantially less than for M/S phase limits for signal components. Channel 4 accuracy separation is considered as this would -amplitude error of one sideband only assume increased importance if a of the S signal, typical of the h.f. loss of surround sound matrix system Fig. 2. Inherent crosstalk of the broadcasting were adopted. Part 2 multiplex signal plotted against construction and alignment gives 1) Amplitude error between the M and and Part 3 gives details for the coder S signals to the Portus and modifications 2) Phase error between the M and S sin fit Haywood decoder to provide a low signals distortion reference decoder. A(38kHz) 3) Error in pilot phase Work on this coder started originally Fig. 1. How the stereo multiplex signal 4) Amplitude imbalance between the as to whether an out of curiosity can be decoded. After de- emphasis the sidebands of the S signal would be possible. inductorless design A' and B' outputs. become left and right 5) Phase shift in a sideband of the S Early experiments were promising and channels. signal the design has been pursued to give 70 performance of broadcast quality. The specifications of stereo coders now in use at both national and independent local radio transmitters are given in Table 1 and most existing coders have similar figures. Particular objects of this design are to improve crosstalk at the higher audio frequencies and achieve mid- frequency distortion better than 0.05%. Stereo signal specification The modulating signal in the Zenith -GE pilot tone system is defined as A+B A-B 0.9I + sin27ftt+0.lsinrfJ I, where A is pre -emphasized left channel, B is the pre- emphasized right channel, and fc is 38kHz. 1(A +B) is called the sum or M signal, and '/2(A - B)sin2Tfct is called the stereo difference or S signal, and is a double sideband suppressed- carrier signal. 0.1sinrrfit is the pilot signal at 19kHz. Substituting the maximum values 2 3 4 5 6 7 8 9 10 A + 1. and B= + 1 or -1 gives the PHASE ERROR (deg.) maximum amplitude of 90% for the M AMPLITUDE ERROR ( °/o)

www.americanradiohistory.com HO Wireless World, April 1977 Table 1. Some parameters of the broadcast coders in use today.

BBC IBA MPX

Amplitude response ±0.5dB 60Hz - 10kHz 50Hz - 15kHz ± 1dB 40Hz - 15kHz Channel separation 100Hz - 10kHz 40dB 400Hz - 5kHz >48dB 10kHz - 15kHz >36dB 30Hz - 15kHz >42dB 38kHz Harmonic distortion 0.3% at 2dB above 0.5% at peak level Fig. 4. Basic arrangement for the (1kHz) peak level switch encoding method. Switch would 38kHz leakage <40dB <40dB typically be a ring of diodes or f.e.t. switch driven by the 38kHz square wave. encountered in receivers (a) -phase error of one sideband only of the am, 100°/ w 88°% S signal. ° 7Z +,

I I For reasonably high channel separation, r I a ut I say better than 45dB, the above effects I I 1s 19 23 53 o tt may be considered as algebraically 4 15 23 53 additive. It is evident that extremely Intermodulation FREQUENCY H3 Ot 15kHz (b) stringent amplitude and phase 15/ 9 &19/23 15/23 \ H2 ot 23kHz Fig. 5. Desired characteristic for the performance requirements are set for a H2 ot 15Hz filter in the simple switch coder, Fig. 5. coder intended to give high channel A linear phase response is required up separation. 4 8 30 45 46 to 531Hz. Another problem in 1 the multiplex Demodulating system is distortion. Apart from the Demodulated 38kHz in stereo usual (C) harmonic and intermodulation 45kHz 30&46kHz distortions, spurious beat tones can be produced in the decoded outputs. This is elay the result of intermodulation 7 8 between FREQUENCY (kHz) the various components of the stereo signal and, though predominantly Fig. 3. Principal possibilities for a L Differences Balanced receiver problem, could also be caused production of beat tone distortion in modulator in the signal generation method or in a any receiver (h) whenever a composite coder's output amplifier. Beat tone stereo signal (a) undergoes intermodulation distortion. 38kHz distortion is worst at the higher audio Additional sine frequencies and subjectively produces tones are produced in a stereo receiver Fig. 6. Bloch diagram for the matrix an unpleasant `splashing' sound on (c). coding method. sibiliants, Most stereo receivers will give clearly audible low- or mid -fre- has too high an amplitude. To quency beats on the 10 and 14kHz remove deficiences in the filter make such the components bursts during the BBC stereo test zone above 53kHz as well as coders susceptible to all the forms of reduce the S amplitude transmissions even though these tones by 7/4 requires a signal degradation listed earlier. A filter with the are not at full level. On mono reception amplitude characteristic complete switching coder design has shown in Fig 5, and a linear phase of a stereo signal the effect is not been published by Mack' and the response noticeable except on very poor at frequencies below 53kHz! virtues of diode cross modulator circuits Broadcast quality coders . receivers. Fig 3 shows the beat tone typically use for applications including coding stereo ten or so inductors in possibilities in both mono and stereo such a filter. Other extolled by the same author2. reception. switching arrangements can avoid the The matrix form of coding is shown in necessity for S amplitude correction Fig 6. A point to note is that the 38kHz and Generating multiplex signals in other respects switching coder fed to the multiplier in this case is a sine performance is largely There are two principal ways of pro- determined by wave. Another alternative would be to switching time and 1:1 ducing the coded stereo signal. The first accuracy of the use a conventional switching multiplier 38kHz square wave. and almost universal are switching Whatever low -pass filter is required practical methods, while the second is the matrix realisations need careful alignment method where the individual signal involving sever- Fig. 7. Complete block diagram of the al interdependent components are generated separately adjustments and coder described. and then added together. Conceptually the simplest and also a Left I 15kHz A P e Ph_. IOw-Pa5$ common way of switch encoding is to filter Phase Corrector M PX switch between the A and B signals I Adder with a diode ring or similar device Mono driven by 38kHz, Fig 4. For a square 15kHz e empha: 1--iii- low -pass Delay o wave switching signal the following filter Stereo output is produced

A +B A -B 4 sin2Trfrt Dlf ferencing A -B Double 2 2 balanced amplifier modulate +3sin6Trfrt +5sin10Trfct+ ... 38kHz 19kHz sine wave Pilot The snag is that sidebands around odd sine wave 19kHz phase crystal notch corrector harmonics of the switching frequency oscillator filter are present in the output and, more difficult, the required difference signal

www.americanradiohistory.com Wireless World, April 1977 S

Fig. 8. Thermistor- controlled oscillator with the R53 bead running at 205 °C, and a resistance of 82 ohms.

fed by a square wave, filter out the difference signal from the odd harmonic components, and then feed it to the adder. With the matrix arrangement in Fig. 9. Oscillator with improved is placed before the multiplier's carrier the diagram the last three degradations amplitude /temperature drift. Tr, and input. The pilot must also arrive at the can be made negligible so crosstalk Tr3 form a long -tailed pair comparator output adder at the correct amplitude performance mainly rests on achieving and R, R6 equalize the signal voltages and phase and a small phase shift is good gain stability and phase matching across the f.e.t. to linearize it and required to equal the time delay between the sum and difference signal reduce distortion of the sine wave through the doubler, amplifier, notch paths. output. filter and balanced modulator. To However, some new problems arise provide balanced outputs a straightfor- with this form of coder. The linearity of prevent gross beat tone effects due to ward unity gain invertor is fed from the the multiplier to audio frequencies will ultrasonic components on the audio adder output. have an effect on beat tone distortion inputs. It is desirable that rejection of Power supplies are entirely conven- performance and in a practical design frequencies of 19kHz and above be at tional, producing plus and minus 15 there is the danger of impurities on the least 45dB so this means that when volts at around 100mA. Power take off 38kHz producing further beat tone pre -emphasis is in use, giving around points are provided for running the outputs. Common to all forms of coder 20dB boost at 19kHz, a filter attenua= clipping amplifier and v.h.f. oscillator is the need for a low distortion 19kHz tion of 65dB is required by 19kHz. If a described later. pilot of correct phase and good stability, !passband ripple of only 1dB is allowed and audio pre- emphasis and filtering to this implies the enormous attenuation 19kHz oscillator limit the bandwidth of A and B signals rate of 200dB /octave between 15 and The accepted frequency tolerance for to 15kHz. 19kHz. the pilot tone is ±2Hz so crystal Fortunately two cascaded Toko filter control, if not essential, is certainly Choice of matrix method blocks can exceed the requirements in a desirable. As a sine wave is With an instinctive loathing of induc- very small space and at reasonable cost. required anyway it seems sensible tors and poor prospects at the time of The drawback of a filter with such to start with a sine wave crystal realising a sensible active filter meeting violent attenuation so close to the oscillator. This, is something which the stringent phase and amplitude passband is that there is little hope of often gives circuit designers a problem requirements while introducing negli- achieving a linear phase characteristic but a reliabl inductorless circuit is gible noise and distortion, the matrix and this is a deficiency common to all easily formed at low frequencies by approach looked more promising. Using stereo coders. Part 2 includes a spec- building a Wien bridge oscillator the matrix principle only the first two trum analyser photograph of the pre- around the correct frequency and then signal degradations should be apparent sent filter response and a graph of putting the crystal across the series and to meet a target channel separation measured phase shift. element of the bridge. Easy starting of 55dB implies an M/S amplitude error The audio difference is derived and with reliable crystal lock is the result. of less than 0.18% and an M/S phase fed via the balanced modulator to the The standard thermistor amplitude error better than 0.1°. output adder while the sum signal is control method, Fig 8, proved adequate The 'block .diagram of the coder is produced by feeding equal amounts of A for an early prototype, but even running shown in Fig 7. Both 19 and 38kHz sine and B directly to the output adder. The the bead as hot as permissible, 200 deg waves are required in this coder and longer route of the difference signal C, still means that its operating point is starting with a 19kHz sine wave which means that it is slightly delayed at the determined roughly 9 parts in 10 by the is then doubled using a linear multiplier adder compared to the A and B com- oscillation voltage and 1 part in 10 by to square its input (a sine -wave squared ponents and at the higher audio fre- the ambient temperature. With this equals a single wave of double frequency quencies this would amount to a circuit I measured an amplitude drift of plus a d.c. term) and produce 38kHz of significant phase shift between the M -0.02dB /deg C over the range + 10 to correct phase involves less filtering and S components, hence the phase +40 deg C and distortion was below than starting with a square wave at a correctors inserted in the A and B lines 0.05%. Evidently some form of amplified higher frequency (38, 76 or 152kHz) and to the adder. control was needed to improve this rift dividing down. Because the linear doubler used to figure tenfold and allow maintenan ±e of If the coder is to be fed from any produce 38kHz is not a perfect device good channel separation over a wide practical signal source other than a some leakthrough of 19kHz may occur, temperature range. distortionless audio signal generator particularly at extremes of the The circuit evolved is in Fig. 9 where then the 15kHz filters are essential to temperature range, so a 19kHz rejector an f.e.t. replaces the thermistor as the

www.americanradiohistory.com 82 Wireless World, April 1977

gain control element but with lineariz- Appendix = ' /zsin'rrfBfit, so that fractional crosstalk ing components to maintain the distor- is sinrfB8t. tion performance. Linearizing is Inherent crosstalk arising from defi- achieved by equalizing the gate /drain ciencies in the coded signal. and gate /source signal voltages and is Crosstalk is expressed relative to the Error in pilot phase. done by R5 and R6. The f.e.t. is also only full level on the decoded channels when Suppose pilot is 0.lsinfc(t +8t), so in the allowed to contribute a small amount of A =B=1 as this is the most convenient decoder the regenerated 38kHz is the total resistance between pin 2 of the reference when making measurements. sin27ff(t +8t). D(t)= i.c. and common, and this fraction is

determined by R3 in the source lead. !A+B A-B I Amplitude error between the M and S + sin2rf.t 'sin2rf,(t+8t). Linearizing produces distortion better signals. than 0.05% compared with around 0.4% Ignoring the pilot signal and consider- without. ing an error 8 so that the composite Add '/a(A +B) and neglecting Transistors Tr2 and Tr3 form a long signal becomes non -baseband terms the decoded A tailed pair which compares the oscilla- signal is A +B A -B tor amplitude with a direct reference sing t voltage. Resistor 8 prevents loading of 2 2 +8 f` the oscillator output by changes in Tr2 (1 + cos2rf,fit) + 4 1-cos21r f,at), 4 input impedance over each cycle. The i.e. S is low in level if 8 is positive. direct error voltage feeds the f.e.t. gate After multiplication in the decoder, and fractional crosstalk is sin27fffit. after filtering (R7, C10) to remove considering only the 38kHz component oscillator components. The two transis- of the reinserted carrier waveform Amplitude imbalance between the tors are identical types and sidebands of the S signal. mounted together so that their two A+B A-B D(t) + sm2rfct isin2rfct If A =0, B =1 and B(t)= sin2rfBt and a, base -emitter junctions provide 2+8 sideband imbalance exists then the temperature compensation; the use of a composite signal is matched pair in a single can does not Adding ' /4(A + B) to give the decoded A seem to be justified. Stability of the d.c. signal, and considering only baseband sin2rfBt cos2r(fe- fB)t reference is assured by using low components gives 2 4 temperature coefficient resistors for R11 A +B A -B cos2r(fc +fB)t and R12 as well as a stabilized negative Al line. 4 + 2(2 + 8) 4 +8 Though a square wave oscillator Considering only baseband terms followed by a filter could have produced Related to peak level, ' /2B, fractional 8 +8 similar amplitude stability simply by crosstalk is 8/2(2 +8). D(t)= -sin2rf8t. defining the voltage excursion of the 8(4 + 8) square wave generator there is a unique Phase error between M and S signals. Adding '/4(A +B) the decoded A signal is advantage in the method described. Suppose A = 0, B = 1 and Namely, the long -tailed pair compara- B(t)= sin2rf8t.lf a delay of fit exists on tor need not look at the oscillator the S signal, the composite signal is output directly; it could look at the level sin2rfót 8 l sin27fBt sin2rfB(t +fit) 8(4 + 8) I of 38kHz which feeds into the multiplier ( I sin2rfct. and thus act as a servo, taking up gain and fractional crosstalk is therefore drift in the doubler, amplifier and notch filter. After decoding, adding ' %(A + B), i.e. 8 1 /4sin2rf8t, and neglecting non -baseband 4(4 +8) Printed boards (a total of three) are components, the decoded A signal available for this encoder for £7.50 Phase shift in the upper sideband of the 1/4 \ (1-cos2rfH7,t)2+ sin 22rf68t S inclusive from M. R. Sagin, 23 Keyes signal. Road, London NW2. Taking equation Al but for a phase error in the (fC +f6) component, signal is sin2rfBt cos27(fc_f6)t 2 4 cos2r(fc +fB)(t+fit) 4

D(t)='/a Isin2rfBt.cos27(fc+ f6)at

+cos2rfBt.sin29T(fc+fB)8t sin21TfBt I 8 and the decoded A signal is '/4sin(fc +f6)6t, giving a fractional crosstalk of' /zsin(ff +GAL

References 1. Z. Mack, Stereo service generator (in German). Circuit of a switching type coder is given. Funk -Technik 1968 p.532. 2. Z. Mack, Comparison of transfor- merless ring- modulators and cross modulators. Radio and Electronic Engineer vol. 44 1974 p.407.

www.americanradiohistory.com Wireless World, April 1977 xs Power semiconductors 2

A survey of devices, technologies and applications

by Mike Sagin, Assistant editor Wireless World

Over recent years much development in the 1950s and was used to replace internally connected transistors as has taken place in the power semicon- thyratrons and mercury -arc rectifiers. shown in Fig. 1(b). A regenerative situa- ductor field. Conventional devices are Since then it has undergone much tion exists when the positive feedback getting larger, quicker and more effi- development to produce devices which gain exceeds unity. Under reverse bias, cient, and several new devices have can switch 1000A or 1000V in one the s.c.r. behaves like a p -n junction been introduced to the design engineer. microsecond, withstand voltages up to rectifier. The switching characteristics These semiconductors allow far more 4kV, handle r.m.s._currents up to 2.5kA of a typical reverse blocking s.c.r. are freedom in the design of a power and operate at frequencies up to 5kHz. shown in Fig. 2 and the important control system provided that they are Several types of construction are now ratings and characteristics are shown in used correctly. This article covers the used, all of which have very definite table 1. various types of device currently advantages and corresponding disad- In general, for high operating vol- available and outlines applications, vantages. Because designers have to tages, the p -n -p -n structure must be together with future developments. "rob Peter to pay Paul" s.c.rs are thicker and possess a higher resistivity. designed for specific applications. Unfortunately, this increases the vol- Thyristors The basic s.c.r. as shown in Fig. 1(a) is tage drop, which reduces the current Thyristor is the generic name for a a half way device whose bistable state rating. High frequency performance is semiconductor bistable switch which depends on a positive feedback loop. also degraded because the rate of rise in has at least four semiconductor layers. When the s.c.r. is forward biased it can current (di /dt) rating is reduced and the The most common type, the silicon be switched from a high to low impe- turn -off time increased, due to a larger controlled rectifier, was first introduced dance state by making the gate positive stored charge in the structure. Another with respect to the cathode. This action important factor which determines the is analogous to a complementary pair of voltage rating is the surface condition Table 1 Important ratings and characteristics Off -state osM Peak repetitive and non -repetitive voltages 'V1

I UHM Peak current 'mA)

On-state V !M On -state voltage 'V) /!,A / Mean on -state current 'A1

I lRM I IISM Repetitive and non -repetitive currents 'Al / Holding current'mA)

Trigger a b Gate trigger voltage 'Vi and current 'mA) Fig. I (a) Basic s.c.r. structure, (b) Fig. 2. Switching characteristics of a Equivalent transistor circuit. typical reverse blocking s.c.r. v Reverse bias hHM .,M Peak repetitive and +15 A non -repetitive voltages 'V' High conduction region IHHM Peak current 'mA1 Thermal R,, Thermal resistance 'deg C /W1 T Junction temperature 'deg C) Maximum 1g2 I 1g=0 Holding reverse current- Turn -on voltage !g! Turn -on time . d / /dt on Rate of rise of current 'A s)

Turn -off + Vat Turn -off time s) 1 d / Rate of fall /dt off; of current and Reverse Forward dV /dt off rise of reverse voltage in Reverse blocking blocking Forward turn -off 'A/ s. V/ s) avalanche region region breakover voltage dV /dt Rate of re- application of region forward blocking voltage (forward avalanche region) V s)

www.americanradiohistory.com 84 Wireless World, April 19774 where the p -n junction meets the silicon Cathode Gate Gate Cathode surface. Surface contouring or bevelling 4 Fig. 4. Centre gate structure. allows higher voltage operation by Gate Cathode reducing the electric field in the deple- tion layer at the surface of the silicon pellet. The allowable current through a device depends mainly on the conducting area. Silicon slices of 50mm diameter are now used in high power s.c.rs and larger devices are being produced in b the laboratory. Anode Switching performance has received A A Fig. 5 (a) Amplifying much attention because of the di /dt Fig. 3. Point gate s.c.r. gate structure, problems which have been encoun- (b) Equivalent circuit. Auxi tered. The turn -on process of a s.c.r. is iary Gate two dimensional because the structure cathode Cathode has an electrical resistance across the silicon wafer. Switching is initiated near to the gate electrode and the conducting area spreads outwards until a uniform current density is established. a If the build -up of load current is too fast, localized "hot- spots" are created which P can damage the device. This problem is High resistivity most acute in the early point -gate n -type structure, shown in Fig. 3. The area P Alloy regrowth initially turned on is very small and is region dependent upon the amplitude of the gate signal. An obvious progression was Anode the centre gate, shown in Fig. 4. This Cathode Fig. 6. Distributed amplifying gate type of construction is widely used in Gate consumer and light industrial s.c.rs and structure. allows di /dt ratings up to 100A /µs when y using gate pulses of 1 -2A. The next development to improve the switching performance was the amplifying gate s.c.r. - see Fig 5. This type of structure may be considered as two radial s.c.rs with a common anode connection. P High resistivity When a positive gate signal is applied, n- type current flows into p the region beneath P the gate contact and across the p -n Alloy regrowth region junction at the nearest point to the gate. This forward biases junction J4 and Anode current flows into a metallized region which overlays the outside edge of this Cathode junction. The gate -pulse current then re- enters the p region and crosses the Fig. 7. Interdigitated amplifying gate p -n junction J3 at the nearest point. structure. Because the length of the auxiliary s.c.r. inner cathode edge is shorter than the main s.c.r. inner edge, the current density at J4 is higher than J3. This ensures that the auxiliary s.c.r. switches before the main section. When the auxiliary s.c.r. has switched, most of the P anode current flows in the lowest High resistivity impedance circuit to the cathode lead n- type which includes the inside edge of the P main s.c.r. The equivalent circuit is Alloy regrowth region shown in Fig. 5(b). Molybdenum Although this structure greatly Anode improves the di /dt ratings, further developments have produced the distributed amplifying gate s.c.r. shown in problems, "Peter" is effectively robbed spurious triggering of an s.c.r., due to Fig. 6, and the interdigitated amplifying again because as the surface area of the the capacitance of the p -n junction and gate s.c.r. - Fig. 7. These are extensions distributed gate increases, so the main the leakage current from the gate of the basic amplifying gate device in cathode area, and hence, anode current junction. The effect is one of increased which the length of the main s.c.r. carrying area decreases. gate sensitivity. This brought about the cathode switching edge has been A second rating which effects the shorted -emitter structure which uses increased to reduce the spreading switching performance is the dv /dt. partial shorting links between the gate distance. Although this appears to be Rapidly rising voltage waveforms and and cathode junction, to produce thé the answer to all power switching high junction temperature can cause same effect as placing a resistor Continued on page 87

www.americanradiohistory.com Wireless World, April 1977 85

International Rectifier makes the most of semiconductors

... to make the most of your circuit and equipment performance! From a discrete diode to a complex circuit function ... from minimum to maximum power where solid state electronic and electrical power conversion and control are involved, we have the experience. Since 1947, the year the semiconductor industry was born, we've chosen to specialise in those areas where our sophistication and high technology make a big difference. When we make a product, we make the most of it. The most in technology ... the most in performance ...the most in configurations ...and the most in reliability. So check our areas of specialisation, and keep us in mind when you begin your next design. You too, can make the most of it with IR semiconductors. I NJTE RNATIONAL RECTIFIE R HURST GREEN OXTED SURREY RH8 988 TELEX RECTIFIER OXTED 95[19 TELEPHONE OXTED 3215(4231

WW-012 FOR FURTHER DETAILS

www.americanradiohistory.com 86 Wireless World, April 1977

POWERER n. ability to do or act;

AEI Semiconductors Limited Low Power Thyristors manufacture a wide range of Medium Power Thyristors industrial diodes and thyristors from High Power Thyristors 1 amp to well over 1,000 amps. AEI are acknowledged experts and Low and Medium Power Inverter have the experience to make power Thyristors SEMICONDUCTORS semiconductors for a wide range of High Power Fast Switching Thyristors applications. AEI's wealth of A.C. Controllers technological expertise ensures that The symbol of pwrer. reliability is the keyword of their Low and Medium Power Diodes product range. AEI are proud of High Power Diodes their reliability and proud of their Voltage Regulator Diodes AEI Semiconductors Limited name. To AEI's customers this Plastic Power Microcircuits Carholme Road, Lincoln, England. ensures that, whatever the Telephone 0522- 29992, Telex 56163. requirement, the best device is Thyristor and Rectifier Assemblies specified and supplied. BS 9300 types Part of GEC Electrical Components Group

WW - 099 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 87 Continued from page 84 between the gate and cathode. The only replaces the solder joints between the s.c.rs connected back to back. These disadvantage of this type of construc- silica pellet and the plates and, in turn, devices are mainly used for a.c. power tion is the slightly increased firing relieves much of the thermally induced control and are generally restricted to requirements. stress on the pellet. This system is the lower power applications. The structure The turn -off time for a s.c.r. will only practical method for encapsulating of a typical glass passivated triac is determine the maximum operating pellets of more than 1 inch in diameter. shown in Fig. 9. Seven steps are frequency of the device. During the An even more recent development in necessary in the construction of such a turn -off period the excess minority pellet encapsulation is glass passiva- device and the process begins with an n charge must either be swept out by an tion. A thin coating of low temperature type high resistivity silicon wafer which electric field or must decay by recom- glass is fused on to the silicon chip and has p layers deeply diffused into both bination within the silicon before the performs the same function as the sides. Silicon- dioxide diffusion masks s.c.r. will block a forward voltage. For silicon dioxide layer used in the planar are grown, and p+ regions are defined rapid decay more recombination diffusion process. Glass passivation is a and diffused into the wafer. A second centres must be introduced. One meth- post- diffusion process and is superior to diffusion mask is grown, and n+ regions od of achieving this is gold diffusion SiO2 because it can be applied in thicker are defined and diffused into the wafer. during fabrication. The introduction of coatings, which also allow higher A silicon- dioxide etch mask is grown gold impurities does, however, reduce voltage ratings. Another advantage of and defined. Grids and gate moats are the voltage and current ratings, and gate glass passivation is the hermetic seal it- etched into the wafer and the glass sensitivity. produces which allows simple plastic passivated layer is then applied in these packages to be used instead of the grids and moats. Finally, contact areas Construction. The heart of a thyristor is hermetic metal containers. are opened on the wafer and nickel - its multi -layered pellet of alternate p Future devices will no doubt have lead -tin solder metallization is applied. and n -type semiconductor material. The improved voltage and current ratings The wafer is then separated into pellets. pellet structure may be' fabricated in especially with the development of The triac can be triggered by either a several ways, depending on the charac- more uniformly doped silicon. As men- positive or negative gate signal regard- teristics and complexity of the device. tioned earlier, 50mm diameter silicon is less of the voltage polarity across the The most popular fabrication methods now commonly used in high current main terminals of the device. The are alloy diffusion, full diffusion and s.c.rs. Larger diameter slices are already triggering mechanism and current flow planar diffusion. The first two methods well advanced and will shortly be used within the triac is shown in Fig.10. Gate use large -area p -n -p wafers which are in commercial devices. trigger polarity is always referred to formed by gaseously diffusing p type terminal 1, and the potential difference impurities simultaneously into both Triacs between the two terminals is such that faces of a thin n type wafer. Where A bidirectional triode thyristor, corn - gate current flows in the direction specific device characteristics are monly called the triac, is basically two indicated by the dotted arrows. Because required, a second diffusion step is used to complete the all- diffused p -n -p -n Cathode junction formed by Fig. 8. Alloy- diffused pellet formation. alloying N -type impurity into PNP pellet structure. To do this, each p -n -p wafer is selectively marked on one side and Cathode Gate contact Fig. 9. Glass passivated centre gate diffusion takes place through the win- welded to triac structure. dows in the mask. The finished wafers gate P- region, T are then diced into individual pellets. N In Glass the manufacture of some higher power P Solder- passivation PNP pellet s.c.rs where only one pellet is available N formed by from the wafer, the original p -n -p wafer gaseous diffusion P is converted into a pellet structure before the final n region is added. In this construction the alloying technique is used to fuse a gold- antimony layer into Fig. 10. Current flow in a triac. Dotted each p -n -p pellet - see Fig. 8. lines show the direction of gate Planar structure describes a type of current. device where all of the p -n junctions are V on a single surface of the pellet. In this construction a thin layer of silicon dioxide is grown over the wafer before diffusion starts. This prevents conta- mination of the silicon surfaces. Be- cause the planar construction requires more silicon per amp, the process is normally used for low current devices G (+) G (-) where many pellets can be cut from a single wafer. Encapsulation of the s.c.r. pellet has played an essential role in the progressive increase of power ratings. All s.c.r. characteristics are temperature sensitive and provision must be made to conduct away heat generated in the silicon. The older, more traditional method is to hard solder the pellet between a pair of thermally matched plates, one of which is then soldered to a copper stud. The stud serves as one G (+) G ( -) terminal and the thermal conducting path. A newer method of encapsulation for devices rated at above about 150A is the pressure contact system. This

www.americanradiohistory.com 88 Wireless World, April 1977 the direction of current flow influences switch from the conducting state to the commutating dv /dt capability of the the gate trigger current, the gate blocking state at each zero- current device, and is specified in volts per requirements differ for each of the four point. This action is called commuta. microsecond for the following condi- modes. The operating modes in which tion. If the triac fails to block the circuit tions. The maximum rated on -state the main current is in the same direction voltage, control of the load power is current IT(RMS), the maximum case as the gate current require less trigger lost. Commutation for resistive loads temperature for the rated value of current than those in which the main presents no special problems because on -state current, the maximum rated current opposes the gate current. the voltage and current are in phase. off -state voltage (VoR0 ) and the maxi- Unlike s.c.rs, turn -óff times are not For inductive loads, however, the mum commutating di /dt. associatéd with triacs because of the current lag causes an applied voltage, The addition of a series capacitor and physical structure of the device. The opposite to the current and equal to the resistor "snubber" network across the ability of a triac to commutate a fixed peak of the a.c. line voltage, across the triac reduces the commutating dv /dt of value of current is an important char- triac after the zero current point. a circuit and is often used for inductive acteristic, which is known as the The maximum rate of rise of this loads. The sizes of these components commutating dv /dt capability of the voltage which can be blocked without vary with the load but typical values are device. In a.c. applications a triac must the triac reverting to the on state is the 100 ohms and 0.1µF. Table 2 shows Continued on page 91

1N3893

20n SCR1 57310E D220 7R5 20W

mm 4 x 1N1196A 415 n 1,000V d. c. 400Va.c 2t I ^I^ I Load / J 220V Fig. 11. Asymmetrical s.c.r. junction a 50F 42µH Current structure. transformer 2t o 11

20n Fig. 12. Practical circuit for an 0' 5CR2 induction cooker hob. For further D2201N l 1 57310E details see RCA application note number AN -6456. 1N3ú93

1000 15k 2N3053 o +30V 20 8W y 4k7 C Current 0- transformer 2k2

25t 3k3 1t 25t +30V 4k7 BD135 2 k2 33 2p.2

20 100p BW

k 33

+ 30V 2N3053 Flip -Flop 50k CD4013A BD135

4k7 10k +8 5V

+85V 4k7 2N3053 15k 1k 12k2

1k2 11

www.americanradiohistory.com Wireless World, April 1977 89

400W ESM 1000 and 2060 TO -83

250W BUX 20 to 25 TO -3 modified

BUX 10 to 15 TO 3

In high speed switching, the Sescosem Division of Thomson -CSF is ready for every industrial and professional application. Main

application areas are : static converters 120W operating on 24V/48V/1 10V batteries, and BUX 39 to 45 static converters operating on 110V/220V TO-3 mains motor speed controls. Write for technical data.

Voltages from 90V to 500V (BUX series) ; from 100V to 200V (ESM series)

Current from 1A to 150A

Frequency up to 50kHz

BUX 59 to 65 TO-66 /// on th e move

THOMSON - CSF

40W Available from these Thomson -CSF distributors: BUX 49 to 55 Spenco Electronics (Phoenix) Ltd., Kelvin Industrial Estate, East Kilbride. Scotland. (035 52 36311). Phoenix Electronics (Portsmouth) Ltd., 169 -141 Havant Road. Drayton, Portsmouth, Hants. (070 18 73441 ). TO-39 Concorde Instrument Company, 42 Dr'cklewood Broadway. London NW2. (01-452 0161). Lock Distribution, Neville Street. Middleton Road. Oldham Lancs OL9 6LP. (061 652 0431). Barlec Ltd., 219 London Road. East Grinstead. Sussex. (0342 24383). Omni Components Ltd., 59 Vastern Road. Reading, Berks. (0734 594834).

Thomson -CSF United Kingdom Ltd., Ringway Hse., Bell Road, Daneshill, Basingstoke RG24 OQG. Tel : 0256 29155

WW -096 FOR FURTHER DETAILS

www.americanradiohistory.com 90 Wireless World, April 1977 Pinnacle hold the power of GENERAL ELECTRIC (U.S.A.)

Power Transistors Triacs Tunnel Diodes GE -MOV Varistors Unijunctions Power Modules Optoelectronics SCR Commutating Er Rectifiers Computer Grade SCRs Capacitors

THE sacIe HOUSE OF POWER

Pinnacle Electronic Components, Electron House, Cray Avenue, St. Mary Cray, Orpington, Kent. BR5 3QJ. Phone : 71531 Telex: 896141 WW -068 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 91 Continued from page 88 Table 2 Cathode Gate 4Fig. 13. Gate turn off s.c.r. structure Commutating di / dt for various currents and N+ emitter frequencies. P- P+ showing centre gate and double p base , layer. Commutating Sine wave Operating di /di Amperes r.m.s. Frequency Hz A /s 141 40 400 88 25 400 21.1 40 60 N- 13 2 25 60 17 6 40 50 MIIIML I Fig. 14. Anode current rise time versus 11.0 25 50 L gate drive current. 1 Buffer Anode V 1.75- commutating di /dt for various currents P+ emitter P CASE TEMPERATURE and frequencies. (Tc)25°C 1.50 Asymmetrical silicon controlled rectifier On -state current A recently introduced device from RCA, (IT) =1oA known as an a.s.c.r., has been specially designed to achieve high dv /dt and w 1.00 di /dt capabilities. A gold dopant is. diffused into the a.s.c.r. pellet to achieve fast turn -off capability but, as discussed 0.75 Fig. 15 (a) turn in earlier, gold doping tends to increase Gate off s.c.r. the 5A on -state and, (b) during turn off. The turn -on time and decrease di /dt capa- 0 500 i I I high density filament forms a 1 1.5 2 25 bility. Special techniques are used 0.5 to non -regenerative region. overcome this problem. The structure of GATE DRIVE CURRENT,Ig (A) an a.s.c.r. is shown in Fig. 11. It differs V from a conventional s.c.r. in that an Gate additional n -type layer is inserted Gate Cathode -Vgq< Vgbrr Cathode between the p+ and n- regions. This new layer is doped so that it increases the forward blocking voltage of the device. The reverse blocking voltage, which is a function of the n- /p+ junction, is much lower than in conventional s.c.rs and is about 15V. The dv /dt capability of the a.s.c.r. is also increased with the introduction of a p+ +VD anode +VD anode ring at the edge of the pellet. (a) (b) Asymmetrical s.c.rs can be used in fast switching applications at frequencies up to 35kHz. A recently s.c.r., but the loop gain is reduced to which allows a low lateral resistance. developed circuit uses these devices in allow turn -off control at the gate. In This low resistance causes a very small an induction cooker hob. A high -fre- effect, turn -on in a g.t.o. is similar to voltage drop from the negative gate quency generator is used to supply an that of a desensitized s.c.r. and, if current. The g.t.o. is surrounded by a alternating current to a flat coil under a sufficient gate drive is applied during non -regenerative section in which the working surface. When an iron or steel turn -on, satisfactory performance can final phase of the turn -off cycle takes utensil is placed above the induction be achieved. The effect of increased place. Device dimensions are about 3 x coil, high- frequency currents are values of gate- current on anode -current 3mm and this size allows a continuous induced into the pan which generates rise time for two values of on -state current operation up to 15A and a heat. A functional circuit for such a unit anode current, is shown in Fig. 14. The forward blocking voltage of above is shown in Fig. 12. This design offers an on -state voltage of the g.t.o. is a 600V. output of 1275W, and a typical efficiency function of the regenerative properties of 80%. of the device, so the transient on -state Gate -drive techniques. For the best voltage drop can be reduced by the use switch -on rise times a positive gate Gate turn-off s.c.r. of an increased gate drive. current of between 0.5 and IA with at Gate turn -off devices (g.t.o.) are also During the turn -off process, the least a two microsecond pulse width is four -layer, three -junction structures as conducting electron /hole plasma is recommended by the manufacturers. shown in Fig. 13 but, unlike the s.c.r., deflected from an area close to the gate, Also, a pulse of -70V between the gate they can be turned off by the applica- which has the highest negative poten- and cathode for the duration of the tion of a negative gate pulse. The g.t.o. tial, to the most remote area beneath turn -off interval is advised. Fig. 16 can be turned on in a similar way to the the cathode, which has the least nega- shows gate drive systems that may be conventional s.c.r. by making the gate tive potential, see Fig. 15. In the on -state used when a negative voltage source of positive with respect to the cathode. As the device conducts uniformly over the 70V is not available. In circuit (a) the positive current is applied to the gate, entire cathode area. Upon application of resistor causes unnecessary dissipation the voltage /current relationship resem- a negative bias to the gate, the plasma is during switching and in circuit (b) an bles that of a forward -biased p -n squeezed into a high- density filament. inductor is substituted to reduce the junction until the point is reached This filament is deflected into a non -re- dissipation. The configuration shown in where regeneration takes over to generative three -layer section and (c) is the best method of switching the switch the structure on. The g.t.o. cannot sustain itself. g.t.o. The peak value of the reverse gate incorporates the regenerative pro- The structure has a centre -gate current carried by the switch in Fig. 16 perties of the two -transistor model of a geometry and a double -layer p /base is approximately half the maximum

www.americanradiohistory.com 92 Wireless World, April 1977

Continúed from page 55 +70V

circuits" had gained currency). Texas were anxious to establish that what we saw at the symposium was not in fact a working device but a model, and our reporter agreed to sign an affidavit to this effect. This incident demonstrates the Americans' awareness of the possi- bility of British priority in integrated circuits. a Mr Dummer is author of a new book "Electronic Inventions 1745 -1976" just published by Pergamon Press at £4.00. Fig. 16. Gate drive circuits for use when This contains mainly brief descriptions a -70V source is not available. In (a) of important inventions in electronics the capacitor charges when the switch but also has some interesting graphs is opened and gate current turns the showing historical trends. For example, g.t.o. on. When the switch is closed the switch is opened the g.t.o. is turned on it shows that in the 200 years from 1745 charged capacitor acts as a source of because of stored energy from L, and to 1945 some 106 electronic inventions negative potential. In (b) when the the increased drive provided by the originated in Europe against 66 in the switch is closed the g.t.o. is turned off stored energy in L2. When the switch is same period in the USA; but in the mere by the capacitor and the extra energy closed the g.t.o. turns off because of the 31 years from 1945 to 1976 the situation stored in the inductor. In (c) when the negative voltage from the capacitor. was reversed, with 32 inventions in Europe and 85 in the USA.

Time by satellite

A digital clock controlled by a time code transmitted from a satellite has been developed by the US National Bureau of Standards (NBS). Once set by the time 46. code the clock, which uses a simple and Fig. 17. Typical d.c. switch. The cheap microprocessor, continues to capacitor and resistor form a keep time in the presence or absence of "snubber" network. the satellite signal. The clock was designed to use transmissions from the National Oceanic and Atmospheric Administration's meteorological satellites, which relay information from buoys, automatic weather stations, ships, aircraft and balloons. The time Fig. 18. Lamp flasher circuit. The on code used dates the information or i2V and off times can be adjusted by the organises its transmission into time -constant networks R1C1 and R,C, sequence. respectively. The clock receives a 100Hz pulse 2 Input stream and time code information in 30s signal data frames. "Since each time code frame differs from the previous one by Ignition coil ' Fig. 19. Car ignition circuit. only 30s there is a high degree of redundancy in this data which can be used to improve the signal to noise anode current of the g.t.o. prior to turn dv /dt. The circuit in Fig. 19 illustrates a ratio. The microprocessor stores the off. This current lasts for about 400ns typical use in a car ignition unit. The received time in random access memory and then decreases to a value less than input signal can be obtained from the and continually updates it by counting 0.7A for the rest of the turn -off interval. mechanical distributor or from an the 100Hz pulse stream." During every The switch may be an n -p -n transistor electronic generator. time code frame the r.a.m. time is or low voltage s.c.r. In the near future it is expected that compared with the new time message Applications of the g.t.o. are mainly in new devices will have much lower gate for errors. The r.a.m. time is assumed to d.c. circuits, and use in cars will be turn -off voltages of around -20V, be correct in the case of error in three popular. Particular devices can operate higher current capabilities, and consecutive comparisons. On the fourth at frequencies up to 30kHz and Fig. 17 increased gate sensitivities. Because the the r.a.m. is assumed wrong and is reset shows a circuit suitable for use as a d.c. g.t.o. can switch higher voltages at in the next frame. switch. Fig. 18 shows a circuit breaker greater currents with a semiconductor To counteract noise in the pulse or lamp flasher. Diacs D2 and D,; are pellet the same size as a conventional stream the microprocessor crystal connected in series to provide a maxi- bi -polar transistor, these devices are oscillator is divided down to 100Hz from mum peak negative gate voltage of likely to replace high power transistors 4.096MHz and phase locked to the -70V during the turn off period. The RC in many d.c. switching applications. received pulse stream. The adjustment "snubber" network in parallel with the of the crystal frequency is accomplished g.t.o., protects the device against high To be continued. with varactor diodes.

www.americanradiohistory.com Wireless World, April 1977 93 Circuit module "time- savers" for New development engineers A range of circuit modules, called Cirblocs, includes power supplies, Products amplifiers, timers, comparators, count displays, waveform generators, relay drivers and switching and phase control units. All of the units are either ready to use or, by simple wire links and component programming, can be set up to provide desired operating characteristics. The manufacturers, Lascar Elec- tronics Ltd, are a new organisation formed specifically to manufacture and market modules covering the most widely used electronic circuits so that engineers can produce many different electronic systems in the shortest Graphic transfers possible time. The managing director of Lascars pointed out that all over the P.c.b. and rub -down acid -resist graphic world engineers are spending time hard transfers, manufactured by E. R. Ni- wiring the same basic types of circuits, cholls, includes space bars which enable during the development stage of their users to lay transfers level and with the particular system. This range, he claims, correct letter, word and line spacings. A offers these engineers a means of saving yellow strip is first placed on to the time by supplying basic, ready to use, artwork below the desired position of circuits, leaving the engineer to devote the wording, and a red straight edge is more time to the development work. positioned over it. The space bar of the Also, he says, fault diagnosis and repair first character is then lined up on the is simplified and complex systems may visible yellow strip so that when rubbed be constructed without specialised down the character transfers to the electronic 'knowledge. artwork and the space bar transfers to Two of the modules, a power supply the yellow strip. By lining up the space and a count -display unit, are illustrated bars of adjacent characters, correct below. spacings will result. White line spacers The ± 15v, 100mA power supply is are used in a similar way to give correct suitable for operational amplifiers, and line spacings. Another important fea- has current, thermal shut -down and ture is counting up to 5MHz, a reset zero, a that the transfers contain output short- circuit protection. Other display latch, and "unwanted zero" adhesive only on the character area and features include a load regulation of suppression. An add -on module is also not on the surrounding area. Transfers 0.6 %, line regulation of 0.13% and an available to convert this count -display include capitals and lower case letters output noise voltage of 0.06V; all of into a digital frequency meter with and numerals in ' /s, '/4 and 'iz inch sizes. these parameters being typical and ranges 0 to 9.999kHz and 0 to 99.99kHz. Prices for complete kits are from £1.00. measured at 25 °C. Five -, 12- and 24 -V Full details of the complete Cirbloc for the '/sin set. E. R. Nicholls, 46 power supplies are also available. range, with Lowfield Road, Stockport, Cheshire. together connection The count -display module is a - WW 302 four instructions and a selection of hand digit unit based on the Ferranti tools, are given in a catalogue which ZN1040E i.c. It has a 0.3in red (or green) may be obtained from Lascars. All of I.e.d. display and may be supplied with a these products are offered on a same - mounting bezel and filter. If the module day basis, if orders are received before 4 is to be fitted in a low- profile instrument p.m. and include no minimum order it may be divided in two and reconnect- charges. Lascar Electronics Limited, ed with ribbon cable. This unit. which P.O. Box 12, Second Avenue, Billericay, has a t.t.l.- compatible input and Essex CM12 9QA. requires a 5V supply, features up /down WW 301

Duplex muting unit potential breakthrough - imitating the Full duplex operation requires the ear by automatically reducing sensitivi- simultaneous operation of both a trans- ty when the owner is talking. The unit mitter and receiver. In order to avoid requires no modifications to existing breakthrough from the transmitter to equipment, is compatible with all the receiver the antennae are often receivers without affecting the "type geographically spaced, typically 30 approval" and can represent. it is miles apart in land -based installations. claimed, a saving of up to 90% against This is obviously impossible with ship- the costs of fitting feeders. board installations. The Duplex Muting The frequency range of the unit is 0.1 Unit, which is placed between the to 30MHz and the insertion loss is receiver and the antennae, eliminates typically 1dB. Callbuoy Marine Elec- breakthrough by monitoring the nature tronics Limited, 6 Somerset Road, and level of the r.f. and introducing Cwmbran, Gwent NP4 IQX. attenuation for the duration of the WW 303

www.americanradiohistory.com Wireless World, April 1977 Polypropylene capacitors Stereo equalizer reluctance motors are totally- enclosed bi- devices with permanently Capacitors in the KP72 range have The EQ2 stereo equalizer has eleven directional lubricated ball bearings. Computer polypropylene dielectrics, instead of bands per channel and provides full Controls Limited, 19 Buckingham polystyrene, and use aluminium foil as equalization from 20Hz to 20kHz with a electrodes. It is claimed that these cut or boost of ± 15dB on each band. Street, London WC2N 6EQ. capacitors offer a considerable Each filter has a control which allows WW 307 improvement in heat resistance com- an ±1 octave variation of the centre pared to polystyrene capacitors. Nickel frequency, and tone controls are also silver terminals, welded to the foil provided allowing very low phase electrodes, make the capacitors suitable distortion equalisations. Balanced Rotary switch for r.f. applications. Capacitances range inputs provide either unity gain or A multi -wafer rotary switch, designated 30, from 100 to 33,000pF in tolerances of switched 10dB gain. L.e.ds are provided as Type has ground, silicone treated h.f. ceramic for high ± 10%, ±5% and ±2.5% and are avail- to monitor and indicate overload. wafers insulation resistance. The switch, which has a able with working voltages of 63, 160 Frequency response is ±0.1dB from roller -type index and 630V. AEG -Telefunken UK Limited, 20Hz to 20kHz and i.m. distortion is mechanism allowing is Bath Road, Slough, Berks SL1 4AW. below 0.01% at the rated output of 2.5V central bush or two -hole mounting, WW 304 r.m.s. Macinnes Laboratories Limited, available with up to 26 shorting and 13 Macinnes House, Carlton Park Indus- non -shorting positions, with or without trial Estate, Saxmundham, Suffolk. stops. Contacts are gold flash on silver WW 306 plate as standard or hard gold plating as an option, and are protected from dust Miniature variable and solder vapour by transparent capacitors plastic covers. Operational life is quoted Miniature trimmer capacitors in the as 25,000 rotations and the temperature Voltronics CP range, from ITT Com- range is -40 to +85°C. Radiatron ponents, are suitable for tuning circuits Drive /stepping motors Components Limited, 76 Crown Road, up to 5GHz. Two basic capacitance A series of drive and stepping motors Twickenham, Middlesex. types 2.5 and 9pF, are available and specifically designed for floppy disc WW 308 these are tuned by sliding a shuttle from drive applications has been introduced one end of the component to the other. by Eastern Air Devices. The standard

They may be used to facilitate rough 1 /100 h.p. a.c. drive motor has a high tuning of several stages before final inertia ratio and output speeds of Precision resistors tuning. The devices have contact resis- 1500rev /min at 50Hz or 1800 rev /min at Wirewound resistors, available from tances of 0.005''-2, voltage ratings of 15V 60Hz. This unit is a permanent- split -ca- G.E. Electronics Ltd, have standard d.c. (300V d.c. max. surge) and temper- pacitor synchronous motor with an tolerances of 0.1 % and are rated at 0.3W ature coefficients of ± 100 p.p.m. / °C. automatic -reset thermal overload pro- (70 °C). These resistors, in values from Minimum life is quoted as 1000 cycles. tector. IOU to 1M12, have temperature coeffi- ITT Components Group Europe, Capa- The stepping motors, sizes 18 and 20, cients of ±3 p.p.m. over the range 0 to citor Division, Brixham Road, Paignton, have single or multiple -start lead screws 85 °C and ±-5 p.p.m. over the range Devon TQ4 7BE. and are available with 15° step angles -55 to 145 °C. The components are also WW 305 for 3 or 4 phase supplies. These variable available in 0.025 and 0.01% tolerances

WW 306

WW 305

WW 307 WW 308

www.americanradiohistory.com Wireless World, April 1977 95 and are manufactured and tested to covering full scale values from 150mV Four mechanical versions, with vertical MIL -R93, MIL -Std -202 and DIN40040. to 1500V. Eight alternating voltage or horizontal mountings, are also G.E. Electronics Limited, 182 -184 ranges, with sensitivities of 31.6kWV; produced for p.c. or conventional wiring Campden Hill Road, Kensington, Lon- cover the range 1.5 to 1500V. Other boards. AEG -Telefunken UK Limited, don W8 7AS. ranges cover direct and alternating Bath Road, Slough, Berks SL1 4AW. WW 309 current, resistance and dBm. The meter WW 313 is supplied with a leather carrying case and is priced at £39.50. Electronic Brokers Limited, 49 -53 Pancras Road, Low -cost 5MHz London NW1 2QB. V.h.f. /u.h.f. amplifiers WW 311 oscilloscope A series of high dynamic range, wide - band linear- amplifiers, from the Mi- The S61 oscilloscope is a single trace crowave Semiconductor Corporation, 5MHz instrument featuring calibrated operate over the range 20 to 1000MHz. 5mV deflection factors from /div to Wheatstone bridge The amplifiers have outputs of about 25 20V /div from I s A Wheatstone bridge, as and sweep rates /div to designated to 29dBm at the 1dB compression point, 500ms of re- /div. Simple trigger controls type 2272, enables measurement with typical gains of 30dB at 1GHz. provide a clear, from 0.00152 to 1,000MS2 with jitter -free trace at all sistances Typical noise figures are 7.5dB and settings and levels over the entire an accuracy of ± 0.002% between 22 and operating temperatures range from bandwidth it is claimed. A trigger 24°C or ±0.005% between 18 and 28° C. -20 to + 70 °C. Tranchant Electronics source may be switch selected from The load on the unknown resistor is less UK Limited, 100a High Street, Hamp- either an internal, external, or line than 50mW. The bridge, which is ton, Middlesex TWqw wST. X equipped with leakage frequency. An external facility is current protec- WW 314 provided for the X -Y display of Lissa- tion for improved accuracy, is supplied jous figures and other interactive by a built -in power supply and has a signals, particularly useful in educa- zero -indicator having a sensitivity of tional applications. The S61 has an 8 x 150nV /mm. Tettex AG Instruments, 10cm screen and is priced at £125 + P.O. Box, CH 8042 Zurich, Switzerland. Silent timers V.A.T. Electroplan Ltd, P.O. Box 19, WW 312 A silent operating elapsed -time control, Orchard Road, Royston, Herts. the Type ET from NSF Controls, is 310 WW variable from 4 to 30 minutes and has a switch rating of 16A at 240V a.c. The U.h.f. attenuators unit has an eddy current brake Variable attenuators in the 67DR range, mechanism and may be produced to General purpose from AEG -Telefunken, are constant customers' specifications for time cy -' multimeter impedance units suitable for use in cles, mounting, shaft details and other The UM11 multimeter, from Poland, has broadband amplifiers - for example in characteristics. Switches are either 38 ranges and offers high sensitivities distribution systems having frequencies s.p.s.t. or d.p.s.t. NSF Controls Ltd, coupled with high input impedances. It 40 to 860MHz. The attenuators are Fence Houses, Houghton -le- Spring, has nine direct voltage ranges having available in three versions: 50, 60 and Tyne & Wear DH4 5RG. input impedance of 100k52 /V and 7552 with attenuations from 0 to 20dB. WW 315

WW312

WW 311.

WW 310

WW 313

www.americanradiohistory.com Wireless World, April 1977 projector. Projectionists of the day Just for the record found this period in the development of the talkies to be a very tedious one indeed. In order to maintain synchroni- Memories of the early years of recording zation between sound and picture, both the film in the projector and the disc on the turntable had to be set at precise by Alan D. Foster starting points. Of course, the inevitable mistake had to happen. Everything was set, the projector and turntable started together. The sub -titles came on the We have already been reminded that deal less about technical matters. I screen, "World Boy Scout Jamboree" the year 1977 marks the centenary of remember him one day standing by the followed by the usual credit titles. the invention of sound recording. To window, closely inspecting a record Meanwhile background music came me, this prompts the very sobering through a pocket magnifier. "I just can't from the record on the turntable. thought that I can clearly remember understand," he said, with a very Everything seemed OK. The projec- further than half way back over this puzzled expression, "how it is possible tionist was himself interested in the period of time. to record so many different notes all at subject to settle down to watch My earliest recollection of the the same time." "After all," he reasoned, the film. The music slowly faded as, on wonders of recorded sound was at "There is only one track of vibrations on the screen, Lord Baden -Powell mounted about the age of eight. An uncle of mine the record and only one stylus to follow the rostrum to make the opening speech had an Edison phonograph and a large them so how on earth does it work!" - and then it happened. number of cylinder records. There may The disc record with which we are As the chief scout's lips moved there in fact have been less than 30 of them in familiar today dates from the beginning came out, not inspiring words appro- all, but to me at the time it was a very of this century, yet so well established priate to the occasion, but the loud impressive collection. The model of was the phonograph that both cylinder sound of a dog barking! Obviously phonograph he had was a fine machine, and disc records co- existed for many something was radically wrong, but all nickel plate and shining black, years. Edison and other manufacturers momentarily the projectionist was lavishly decorated in gold. It had two were producing cylinder records up to transfixed by the near perfect synch- soundboxes, one for making and the 1920s until the demand fell off ronization between the movement of another for playing records, and must completely in favour of the disc record. Baden Powell's lips and the barking of have cost about MO,' with records in The big breakthrough came after 1924, the dog - "it was uncanny," he said. those days running at around one with what nowadays we call electron- The record he had put on the turntable shilling. ics. This had a dramatic effect on the was intended to accompany a film of the Phonographs were made in a variety recording industry. Technical "Down on the Farm" type. In haste, he of models, the cheaper ones being very know -how flourished at a healthy pace had mis -read the film code 'mark S.O.F. simple machines, driven by a and, combined with a widening (sound -on -film) for S.O.D. (sound -on- key -wound clockwork motor with a fan knowledge of acoustics, records were disc). The experience, he said, haunted governor rather like a musical box. produced of such quality that some still him for weeks although he did admit to These models had the unfortunate habit bear comparison with today's high the satisfaction -of having caused as big of slowing down during the run of the standard. 'a laugh as Laurel and Hardy. Only the record. "Melody in 'F' " couldwell finish cinema manager wasn't amused. up "Melody in 'E'," and if the machine The heavy gang This state of affairs was fortunately were not placed on a perfectly level In the late 20s, The H.M.V. Gramo- short -lived and ended with the table, the stylus was prone to jump a phone Company, as it was then, exclusive use of the "Photophone" groove now and then. presented a demonstration of electrical system. Thereafter, the sound to I remember my uncle's bitter com- recording at the premises of Rushworth accompany a film was recorded plaint that blank cylinders for making & Dreaper, a leading, long established photographically along the film itself. in Liverpool. The one's own records cost more than family music house As a result of we. éll directed propa- professionally -made ones but, of course, demonstration was arranged in the ganda, I became the proud owner of they could be used over and over again. large, ground floor showrooms, the my uncle's phonograph and what The record was simply placed on the handsome display of grand pianos and remained of his record collection. machine, and a special cutting tool cases of musical instruments being put Inspired by the demonstration I had would shave off a thin layer of wax, aside to make room for all the seen at Rushworth & Dreaper, I madé removing the previous recording. After paraphernalia necessary to make a an electrical recording head from an S. the application of wax polish and a record. This consisted of an amplifier G. Brown Type A earphone. The old finish -off with a soft duster, the cylinder rack, control panel, two recording machine was given a new lease of life. would gleam like new all ready to be lathes and a large supply of thick, Gone was the large horn and in its place re -used. About 20 or more recordings yellow, wax recording blanks. They was a hefty coil speaker, mounted on a could be made before the record became even brought along their own power large baffle board, driven by a push -pull too thin and had to be discarded. supply in the form of dozens of large amplifier. There was no end to my Cylinder records were fragile things, lead acid accumulators. I was surprised recordings, music and variety from the sold in flock -lined boxes to protect the to see that the record cutting lathes radio, piano duets with a friend and relatively soft wax surface. Apart from were powered not by an electric motor even the interval signals between. being dropped on to the floor an or even clockwork but by a huge iron programmes (who, I wonder, can untimely end could result simply by block suspended like a clock weight remember those ?). One day I found my forgetfully leaving a record on the under the cutting lathe. This, I suppose father, glass in eye, closely studying the machine overnight. In the morning, provided the smoothest possible source works of his watch. Its normally good there could be a gaping crack running of power but, amongst the other timekeeping had gone completely right across the face of the record! With sophisticated hardware, did look a bit crazy, he said. I remembered then I had the usual overnight fall in room primitive. made a record of the chimes of Big Ben temperature the record would shrink on The advent of electrical recording which was wont to come booming out to the machine cylinder so tightly that it gave voice to the silent films of the day. of my den at any time of day. Could the would simply burst. Sound accompanying some early films "old man" have been setting his watch Although he may have known a good was recorded on 16in discs, running on a to the recorded chimes? I often won- deal about music, my uncle knew a good turntable directly coupled to the film dered but never asked.

www.americanradiohistory.com }1î Wireless World, April 1977

Safe, tough, efficient and versatile that's Model X.25 is a general purpose soldering our new miniature CX iron. iron, also wi:h two shafts for toughness and perfect Insulation. Available for 220 -250 volts because it is virtually leak -free (leakage Safe or 100 -120 volts at 25 watts and priced at current less than 1µA). Earth it if you like £3.20 exclusive of VAT. three core lead. It is made to conform with B.S. 3456 and has a breakdown voltage of more than 4000V. Tough because the handle is almost unbreakable and the ceramic shaft is covered by a stainless steel shaft. Efficient because the element is situated right inside the soldering bit and the heat Stand model S.T.3 has a chromium plated generated by its 17 watts is not wasted. steel spring, two sponges for cleaning the bits and is priced at £1.40 exclusive of VAT. Versatile because the iron can be used for a wide variety of soldering jobs; with six easily interchangeable, slide-on bits, ranging from 4" right down to ;" (1mm). It's suitable for small, miniature and micro miniature joints.

Available for 220 -250 volts or 100 -120 volts. Weight 11oz (40 gram). Length 7,1" (19cm). Price £3.20 fitted with standard bit ;'f" (2.3mm). Spare bits £0.46; £0.72; £0.84 exclusive of VAT.

Stocked by most of the well -known wholesalers and many retailers. Or direct from us if are you desperate. Mayflower I -ouse, Plymouth. Send for colour catalogue from. Telephone (0752) 67377/8 Telex 45296 Antex Freepost, Plymouth PL1 1BR Giro 25810)0 Forget all you've ever read about miniaturised soldering irons. This is the NEW CX

WW - 107 FOR FURTHER DETAILS

www.americanradiohistory.com 98 Wireless World, April 1977 ELECTRONICS You will know about DEMA INTERNATIONAL ELECTRONIC COMPONENTS DISTRIBUTOR Blind Rivets FOR INDUSTRY AND HOBBYIST

MONTHLY SPECIALS

LIAARS MEMORIES 3113 K 99 or 3'215 LM 556 69 or 3/190 1103 1024 Ho Ram MOS 99 LM 550 50 or 3.125 1M 709 IB w 3150 7489 182251 64 At Ron TEL 1 3S LM 555 31 w 3, 85 1M 3900 79 or 3/ 80 1702 7048 Brr Hem 695 2048 B,1 U /veal.! PROMS 595 5203 Interesting data and application notes on Blind Rivets - CALCULATOR CHIPS CLOCK CHIPS CT 5007 Boo Own 5001 590.3/175 5311 28 Pin BCD Op MU% 260 yours for the asking CT 5005 12 D,pr 4 F u,K ../Harn 69 or 3/150 5312 24 Pin BCD Up MU% 725 5725 18 Paw6 D,9 MU0 175 0r3 /500 5316 40911224 95 24 Pm 365 5738 8 Dapl 5 Ponr Mem /Co.I 7001 4 o 6 Ott Alen" 350 Flowing Dec Ban Op 1 20 or 3/3 20 Blind Rivets, of course are for making TTL CMOS KY Ouenuly Dapntsw IS LLess 10% 74500 'floc 3/ 50 14522 25 or 3165 permanent joints in sheets, chassis, lane corntuna wnl 51 9 up Lew 15% 74503 20 or 3/ 50 14532 35 or 3/ 90 74508 78 or 3/ 80 74579 25 or 3/ 65 corners. What if you need a detach- TTL 7400 SERIES N W LOW PRICES able joint? Read on about Anchor 7400 £ 0g 7440 E 11 7485 L085 74155 £ 0 69 7401 0g 7441 7486 025 74156 0 69 Nuts, blind rivets with internal 7402 10 7442 7489 1 45 74157 0 69 7403 10 1443 48 7490 0 32 74158 0 69 1404 13 7444 60 7491 0 55 74160 0 89 threads. 7405 13 7445 70 7492 0 35 74162 0 89 1406 22 7446 80 7493 0 35 74163 0 89 22 1447 To fasten a lid or a panel that has got to come off, you need 7407 65 7494 o 40 74164 1 05 7406 13 7448 60 7495 0 45 74165 105 Anchor Nuts which are used with ordinary or 7409 13 screws 7450 12 7496 74166 1 05 7410 0 55 09 7451 12 74170 bolts. 7411 16 74100 0 89 1 65 7453 74175 7413 25 12 74107 0 23 085 1414 22 7454 17 74121 o 23 74180 080 1460 7416 22 11 74122 0 37 74181 2 00 7417 22 7470 24 74123 0 45 74182 0 80 7420 11 7472 21 74145 0 57 74192 095 7426 23 7473 25 74150 0 75 74193 095 7430 l 7474 25 74151 74194 0 85 7432 22 0 59 7475 35 74195 0 78 1437 25 74153 069 7476 14 74198 1 20 7438 19 74154 1 05 7483 69 74199 1 70 ÎI SCHOTTKY 74500 24 74504 29 74520 29 74074 29 Anchor Nuts System J, the high strength threaded insert 74502 29 74008 35 74522 29 for sheets and sections up to 0.270" 6.86mm. 74503 24 74010 29 74537 39 LOW POWER SCHOTTKY

741500 23 741.520 23 741590 1 25 7415193 1 75

14L502 23 741532 27 741593 1 25 7415197 1 65 741504 25 741540 33 74LS95 2 10

74L508 27 74LS42 1 30 74LS107 39

741.510 23 74L574 39 74LS164 1 80 CMOS 4000 SERIES 4010 E 036 4023 E 065 4050 L035 90006 E 0 14 Cr) 4011 0 14 4024 050 4066 0 46 LU 4001 014 4012 0 14 m 4025 0 14 4069 0 15 4013 036 4002 0 14 4027 0 36 4071 015 4014 0 Anchor Nuts Z 65 4028 0.59 System X, the threaded insert for sheets, 4006 0 75 4015 065 o 4030 0 36 plates, sections of unlimited thickness. 4007 0 14 4016 038 4035 0 75 4008 065 4020 0 75 4021 0 65 4042 055 4009 036 4022 o 14 4049 0 35 Anchor Nuts are L INEARS

LM300 7099 E 045 3401 1097 E 1 25 739 ADIP L065 301 V DIP 0 25 380 A DIP 0 80 741 V DIP 022 placed in seconds! 302 1099 040 381 A DIP 090 747 ADIP 044 10100 It's quick and easy, done on the job with tools similar to 304 0 50 550 A DIP 0 55 748 V DIP 024 w 305 1099 0 45 555 V DIP 035 5556114561 V DIP 0.95 riveters. You can buy a hand tool for around £10 or a 307 V DIP 0.38 556 B DIP 0 75 5558114581 V DIP 0 45 w 1099 0 45 560 B DIP 2 45 LM3900 A DIP 025 CC r 75450 308 A DIP 0 59 562 B DIP 2 45 V DIP 100 LL 1099 0 65 565 A DIP 1 40 75451 V DIP 0 23

309' TO3 1 10 566 V DIP 1 40 75452 V DIP 0 23

310 T pkg 0 59 567 V DIP 1 55 75453 V DIP 0 23 311 V DIP 075 709 A DIP 0 20 75491 A pkg 060 320K TO 3 NEG 710 A DIP 0 25 75492 A pkg 065 51 17 15 1 00 711 A DIP 0 18 ICL8038 Funcl Gen 280 324 A DIP 107 723 A DIP 0 38 Volt Contr 05cd1ator. Sme S9

339 A DIP 1 16 886422 Pin pkg 145

340K T03 1 50

12V 1 AMP

V Mini Dip A - 14L D,p 8 16L DIP 7099 8 Pin Header T0100 10 Pan Header kit in a carrying case with a tool and an assortment of Data sneers supplied on re5uest Add 20 ea excepted as Poled Anchor Nuts for about £22. Anchor Nuts cost around CALCULATORS & CLOCKS w /DATA MEMORIES w /DATA £2 -£6 a hundred. 5002 Cal Chap E 0.79 1101 256 Bo Ram Mos E 1 30 5005 Cal Chap 0.79 1103 1024 Bat Ram Mos 1.25 5725 Cal Chap 1 10 1489 182251 64 Bat Ram TTL 1 45 5311 Clock Chap 2.80 82523 Programmable ROM 2 15 5312 Clock Chap 250 5260 1024 Bet Ram Low Power 1 45 5314 Clock 5261 1024 eat Ram L Power 156 Chap 345 1702A 2048 8,t Ram 11.35 5316 Clock Chap 3.95 2102 1024 8/I Status Rem 2.75 CT7001 Clock Chap 385 LEDS Data only for any of above 050 Refundable Agaanst Purchase MV 5020 Jumbo Red or Clear £ 015 MAN I Red 7Sag. 270" 120 TRANSISTORS MAN 3A Red Sep 127 020 2N 22194 TO5 £ 0.42 2N 4124 1092 0.11 MAN 5 Green 7 Sap. 770 185 2N 2227 1018 0.17 2N 4126 1092 0.11 MAN6 6SoldSeg 2.60 2N 2369 T018 0.11 2N 4401 7092 0.11 9 Dglt Array Falrchrld 37 2N 2905A TOS 043 2N 5225 1092 0 17 warb clear magmfyrng lens 2.80 2N 3227 T018 037 2N 5226 1092 0.17

DISCOUNTS. MIN All Items New Branded 10% on orders over L 10 ORDER Guaranteed By DE MA ELECTRONICS 15% on orders over E 25 £ 2.00

PRICES LISTED ARE BRITISH POUNDS & PENCE. SEND CHEQUE WITH ORDER. ACCESS CARD, BANKAMERICARD, BARCLAY CARD ACCEPTED. There are kits for all regular thread systems, BA, Metric, (Card # and expiration date requested). TERMS Whitworth, UNC, UN F. OFFERED TO SCHOOLS & INSTITUTIONS. Data and prices on request. POSTAL AND HANDLING CHARGES SHIPMENT VIA AIR MAIL under 4.99 add .45 £ 10 and over 5.00 -9.99 add .35 No Charge HARMSWORTH HARMSWORTH, TOWNLEY & CO. LTD. DEMA ELECTRONICS INTERNATIONAL HAREHILL TODMORDEN LANCS OL14 5JY P.O. Box 407 San Ramon, Ca. 94583 USA Phone TODMORDEN 2601 (STD 070 681 1601) Cable DEMAELINTL WW-094 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 99 GEARED MOTORS SERVICE TRADING CO 100 R.P.M. 115 lbs. ins.!!

115 lb. ins . 110 volt. 5011z. 2 8 amp single phase Wide range of AC and DC relays VARIABLE VOLTAGE TRANSFORMERS split capacitor motor Immense power Continuously available from stock Phone or write Carriage extra INPUT 230 v. A.C. 50/60 rated. Totally enclosed. Fan cooled. In -line gearbox. RELAYS in your enquiries Length 250mm Dia 135mm Spindle Die 15 5mm OUTPUT VARIABLE 0/260v. A.C. Length 145mm, ex- equipment tested E12.00. Post BRAND NEW. All types. Et. 50 Suitable transformer 230/240 volt E8.00. 200W (1 Amp) fitted A/C Post 75p WHY PAY MORE ?! volt meter £11.50 15 R.P.M. 0.5 KVA (Max. 21/2 Amp) E14.00 Type SD48 15 r p m 80 Ib. ins. Input 100 /120 volt A C Length mot MULTI RANGE METER A C volts 2.5 -500 D.0 1 KVA (Max. 5 Amp) gearbox 270mm Height 735mm. Width 150mm Shaft drive I6mm volts 2.5500 (Sensitivity 20000 /V D C & A.C.) £18.00 Weight 8 5 Kilos BRAND NEW Price D.0 current 0/1/10/100 mA Ohms range 2 KVA (Max. 10 Amp) £30.00 £10.00, cary El 00 Suitable transformer for use on 220 240 volt A C Post 50p Sturdy compact moving coil instrument with 21 3 KVA (Max. 15 Amp) E38.00 E6.00. ranges. dimensions 120 x 80 x 44mm Weight 4 KVA (Max. 20 Amp) E60.00 0.32 kg SERVICE TRADING CO Price E5.50. Inc! leads and battery Post 50p (Total price inc LT TRANSFORMERS VAT & Post E6.48.1 0- 12v/24v at 1 amp E2.50 p&p 50p DRAYTON MOTOR 1 1 1 ) 0-15v at amp + 0.15v at amp (30v amp £2.50 p&p 50p Type ROR 230/2505 50c Continuously rated 1 25 -0.25v at 21/2 amp. E4.50 p&p 75p RPM 901b in Reversible motor Twin spindle TRIAC. Raytheon tag symmetrical Triac. Type Tag 250/500v 10 amp 0- 12v /24v 10 amp E12.35 p&p E1 50 size 100mm by 140mm by 125mm Shah 500 po. Glass passivated plastic mac Swiss precision product for long 0- 4v/6v/24v/32v at 12 amp. E13.00 p&p E150 50mm by Boner Weight 2 kilos New Price term reliability E1.25. P &P 1Op (inclusive of date and application 0-12v at 20 amp or 0.24v at 10 amp E72A0 p&p E1.50 E16.50. P &P E1 00. UnictwA4f sheet) Suitable Drac 20p. O- 6v /12v /t7v /18v/20v at 20 amp £14.00 p&p Et 50 0-6v/12v at 20 amp. £11.85 p&p E1 00 ' 4 ¢ 11111116 0 to 60 MINUTES CLOCKWORK TIMER. Other types in stock, phone in enquiries Double pole 15 amp 230AC Contacts no dial) £1.50. P &P 30p AUTO TRANSFORMERS Step up step down 0 115 200 220 -240V BODINE TYPE N.C.I. 75 wan £4.20 p &Lz Sop 1 50 watt E6.00 p&p 80P 300 watt £8.40. p &p GEARED MOTOR GALVANOMETER. 50 micro mirror giaci 95p 500 wan £12.80 p &p L 1 25 1000 wan £18.20 p &p L I SOp Calibrated 50050 and 0-100 Mfg by Griffin & George (Type 1) 71 r.p.m. torque 101b in Ltd Offered at hai of makers pore ii trig mal ministry Reversible 1/70th h p cycle 38 amp This U S A motor is offered in parking E12.00, p &p 60P 300 V.A. ISOLATING TRANSFORMER as new condition Input voltage of motor 115v A.C. Supplied complete 115/230 screened primary two separate or 115v for 115 or 230v with transformer for 230/240v A.C. input. Secondary two 115v at 150 V A for 115 or 230v output Can be used Price type Post 75p or less transformer Post 65p in series of parallel connections Fully tropicalised Length 13 E6.25. E3.75. 5cm r.p.m. 230 Vok A.C. HONEYWELL PUSH BUTTON PANEL MOUNTING MICRO width l lcm weight 15155 Special price E6.00, car, E1 00 SWITCH ASSEMBLY. Continuously3) 71y rated Non reversible E6.50 Post 75p

Each bank comprises of a change -over rated at 10 amp 250v A C Black knob 1 dia I x nil RODENE UNISET TYPE 71 6/9 VOLT D.C. GOVERNED 40mm e 40mm Spindle 10mm. Dia hole s/e" Price one hank 40p. Two hank 50p. mm E1.00 Post Paid Two for £1.65 Post Paid In, Three bank 60p. Min order 5 p eces P&P TIMER. n 60 SI, 230 AC npemion oto, lapsed n and p_ facilities A 50p rides 24 R.P.M. 230 volt A C. Continuously rated Mfg Mycalex Ex- equip. pro e s t rig phi motorised e e for m tography Fully tested E3.85 Post 75p weirlfig mixing etc Pr,r,. E6.00 p &p 60p 230 VOLT FAN ASSEMBLY (' 1 R.P.M. 230/240 VOLT A.C. SYNCHRONOUS!! Ex- equipment Continuously rated removable aluminium blades Thoroughly tested and guaranteed ONLY E1.50. Post 20p Price £1.25. Post 50p GENTS 4" ALARM BELL 5551111 D C Price P &P 50p VAT 121/2%. 3.41/2v E4.50. - 20 R.P.M. GEARED MOTOR. 230/240 volt 20 r p m motor E1 00 Post 20p

21 -WAY SELECTOR STROBE! STROBE! STROBE! HALF REV. PER HOUR. SWITCH with reset coil. HY -LIGHT STROBE Mk. IV Sync. Motor. 230/240v A C Mfg by Smiths E1. P &P 20p T lie ingenious eiectrn mechanical device i.an be * * Latest t xenon while li y In Jnlid slate my tnd ** ..itched up t0 21 positions and can be reset from y Pe T inggeriny ci c uii 130 240 von A Ct tie tauon 5 u oeil ad I ustabie , position Sy energising the reset coil REVERSIBLE 1 MOTOR 230V I A.C. * 2U p s Designed loi large rooms. Halls etc Liyhl output . ul is * 240v A C operation unit mounted on greater Ihan many su calleJS4 Juulel sir oves Price £18.00. Post General Electric 230v A C 1.600 r p m 0 25 amp Complete with çl chassis Complete with (APO, Price E5.50. y anti- vibration mounting Ty 75p Specially designed ca and tell edto, for Hy lght E8.25. bracket and capacitor 0 sue 110mm x 95mm Spindle die long p Post L i UU 5/16" 20mm Ea-equipment tested E3.00. . Post 50p PRECISION CENTRIFUGAL XENON FLASH -- REVERSIBLE BLOWERS -i 2401 AC1 G* UN TUBES MOTOR * I 12 hp AE, continuous rated reversible motor 100 1201 A C Mt i; PHostries Miniature model R .....iii able Iroin _'sk AfTj. * * 50 60 cycle 2850 r p m Flange fixing d a 4 length 4 '. shaft 1" Seves SF 200 Size 95mm x 82mm Apert re ) x 5 16' Price E3.25. P &P 75p 38mm x .31mm 12 c I m E2.75. Post 50p * * Other types available phone for details ' * * * * * * * * * * * * * * * * * * *. * Also available extremely powerful blower mfg by Fracmo * ULTRA VIOLET BLACK LIGHT * METERS NEW 90mm Diameter r Type: 65CS . O.C. MC. 1 b 10 lu SV amp E3.00. FRACMO 115/230v A C 2800 /3400 p.m fan type aperture 3" * FLUORESCENT TUBES 21/2r' VBL4 25/c Price £12.00. Post El 00 40 wan £7.00 irallers nnlyl 251. 20 wan E4 -60. Pnsr nnp Post 20p iUU amp E3.25. Post' lop Type: 62T2 *4H. use r6 staa bi -pin fittings) MINI 12ín.8 wan £1.75. Post A C M 1 20 50 amp (3.00 Post LUp O 300 volt A Bin. 6 wan 6in. 4 watt Post 25p and 350 Volt AC R M C E3.25 Post 30p *IFor £1.40. £1.40. T4 BLOWER UNIT tube 200/240V a c precision German built * £3.50 plus p &p 40p Also evadable for 112V D C opO E3.50 plus 1 BENDIX MAGNETIC CLUTCH Dynamically balanced quiet. con rated. p &p 4OP T reversible. Consumption 60mA Size * Superb example of electro-mecharacs Main body in two sections Coil section is fixed and has 34" 120mm dia o 60mm dep Price E3.50. * BIG BLACK LIGHT sleeve The drive section rotating on the outer Post 50p 400W Violet Lamp Powerful source of UV * Mercury Vapour Ultra * perimeter When engaged the transmission is Price \ P F ballast unit Is essential with this lamp of bulb and extremely powerful Diameter 11/2" Total width etched ballast unit Post E2 Spare bulb only E10. Post Jf in E28. 114" 24V D C op Price E3.60 plus p &p 45p UNISELECTOR SWITCH * 80p 4 bank 25 way I5 ohm roil 36-48v 0 C operation Ex new equipment £4.25, P&P TIME SWITCH price inc 75p Total VAT £5.40. Horsimann Type V Mk II Time Switch 200;750 volt A C Two on, two off every 24 hours. at any manually preset time 30 amp contacts 36 -hour spring reserve MINIATURE UNISELECTOR ":...:d SQUAD in case of power failure Day omitting device Fitted in 1 LIGHTi° heavy high impact case. with glass 12v. 11 way 4 bank (3 non -bridging homing) E2.50. P &P 35p observation A new conception in light i window Built to highest Electricity Board spec control Four channels each individually tested Price E7.75. Post 50p (Total inc MICRO SWITCHES capable of handling 750 watts of ' VAT Eß.91). micro Type V 15 FL 10 for Omron roller switch 22-IL E2.00 spotlights. floodlights or dozens of small mains lamps Seven post 50p 'Mtn order 101 programs all speed controlled plus flash modulation. effectively 4T 1 10 tar Sob. miniature Burgess type V £2.50. giving 14 different displays Makes sound-to-light obsolete 5V for £10.00, post paid Completely electrically and mechanically norsé free A.C. MAINS TIMER UNIT t Subminiature Honeywell roller M S Type 3 1 bM 90b r 1 U k with 25 s Price only E60.00 or E2.50, post paid flte wl hr a be preset toremany Post 75p S A E (Foolscap) for further details. LEVER OPERATED 20 amp c o Mfg by i sip l0 12 tirs ahead to switch on lei any Unimax USA 10 lot E4.00 plus 5Up P &P 'mm order 1 Iln of time from 10 minsmin to 6 his then off An additional 60 min audible tprier is Wide range of AC and DC relays available. also arc orporated Ideal for Tape Recorders NEW HEAVY DUTY from stock Phone or write in your rights Electric Blankets etc Attractive satin N *7 RELAYS enquiries copper finish Size 135 mm x 130 mm x 60 mm SOLENOID Price E2.25. Post 40p inn VAT & Post by Magnenr Oevvaa '.t(tv A C coo. (Total Mfg E2.87.1 operation appor. 2011, pull it 1 25" Pure E7.00. P &P 75p COLOUR WHEEL PROJECTOR TYPE P150 INTACHANGE 230 -250 VOLT A.C. SOLENOID it SUP, 15ÚW lamp compiete with POWER Similar in appearance to illustration m,ur wheel and motor plate Takes _ s Approximately I Vzlb pull Size of feel 1 V. "x 13/16" le and lull rani ye ul lenses Price £1.00. Post 25p E32.00. ' iisl 11 50(1 RHEOSTATS 24 VOLT D.C. SOLENOIDS INSULATION TESTERS New ceramic construction vitreous enamel 1 UNIT containing heavy duty solenoid approx. 25 Ib. pull at 1 in embedded winding. heavy duty brush assembly. travel 2 solenoids of approx I lb pull at 1/2 in travel 6 solenoids of (NEW) rated. approx 4 oz pull at 'h in travel Plus 1 24V D C. ABSOLUTE Test to 1E E Spec Rugged metal construction. 25 WATT 10. 25.100,continuously 150. 2$0 500. 1 k 1 5k ohm E1.80. Post 1 heavy duty 1 make relay Price E3.00. Post E1 00 BARGAIN or field work. c nstant suitable for bench speed 20p 50 WATT 25. 100. 500. lk ohm E2.40. Post 25p 100 clutch Size L 8 in W. 4 in H 6 in o weight 6 lb WATT 1 10/25/50/ 100/250/500/ 1k / 155 500 VOLTS 500 megohms £40.00 Post 80p /5/ 240 A.C. SOLENOID OPERATED 2 5k / 5k ohm E3.70. Post 35p 1000 VOLTS 1000 megohms £46.00 Post 80p Black Silver Skirted knob calibrated in Nos 1 -9. 11/2 in dia bra.. FLUID VALVE In, leaflet SAE bush Ideal for above Rheostats. 22p Rated 1 p s will handle up to 7 p s I. Forged brass body, w. stainless steel core and spring /i m b s p inlet outlet Precision made British mfg AT CURRENT RATE PRICE E2.75. Post 50p. NEW original packing PROGRAMME TIMERS MUST BE ADDED 230 Volt AC Operation 15 or 20 r p re Each cam operates a c/o micro switch. Ideal I: - 600 WATT DIMMER SWITCH TO ALL ORDERS etc Ex equip Easily fined Fully guaranteed by makers Will control up for lighting effects, displays. ' 1 gé VAT tested Simrliar to illustration /`a, to 600 wares of all lighting except fluorescent at mains THE TOTAL VALUE OF GOODS INCLUDING ?1,14 voltage. Complete with simple instructions £3.66. Post FOR 6 CAM model £5.00 25p 9 CAM model E6.50 UNLESS OTHERWISE STATED 1 1000 watt model £5.60. Post 25p POSTAGE 12 CAM model E7.50 ( 2000 wan model Post 40p Also A £9.75. C I UNT CUSTOMER MIN. ORDER £10.00 Post 5Up. available tor 50 volt C operation Prices as above

ALL MAIL ORDERS, ALSO CALLERS AT SERVICE TRADING CO. PERSONAL CALLERS ONLY 57 BRIDGMAN ROAD, CHISWICK, SHOWROOMS NOW OPEN 9 LITTLE NEWPORT STREET, LONDON, W4 5BB. Phone: 01 -995 1560 AMPLE PARKING LONDON, WC2H 7JJ. Closed Saturdays. Tel.: 01 -437 0576

www.americanradiohistory.com 100 Wireless World, April 1977 THE JAMES ¡COPE H SCOTT 4I6 INDUSTRIAL

RANGE OF EQUIPMENT The James Scott range of Microwave equipment offers industrial users a greater choice of alternative systems in robust, industrial, cast aluminium housings, for a wide variety of applications. The range is made up of standard sub-assemblies which can be permutated to suit individual application requirements. Here are some suggested applications for these units.

PROCESS CONTROL CONTROL SYSTEMS SYSTEMS SAFETY BARRIERS ROAD INDUSTRIAL INTRUDER VEHICLE ALARM ALARMS SENSING SYSTEMS SYSTEMS

PROXIMITY ALARMS

SMALL SINGLE BEAM OBJECT OSCILLOSCOPE COUNTERS 45.6 6MHz Bandwidth. POSITIONING 10mV /cm Sensitivity. SYSTEMS luS /cm- 100mS /cm Timebase (16 Calibrated ranges). Glarecheq Non - reflective graticule. LEVEL CONTROLLERS 45.6 LS ... ( £115) Designed for LOW SPEED Measurements. DOOR 101.15/cm-1 sec/cm Timebase. OPENING SYSTEMS

JCÓPEX Please SCOPEX Instruments Ltd, write or telephone Pixmore Industrial Estate, Pixmore Avenue, for further information and 298.00Letchworth,Herts SG61JJ (046 26)72771 technical literature to (ex VAT) ® Regtl Trade Mark

CARNTYNE INDUSTRIAL ESTATE GLASGOW G32 6AB Tel 041 778 4206 Telex 778286 WW - 064 FOR FURTHER DETAILS WW - 062 FOR FURTHER DETAILS

www.americanradiohistory.com Do not affix Postage Stamps if posted in Gt. Britain, Channel Islands or N. Ireland Postage will 'o obtain further details of any of be paid by le coded items mentioned in the Licensee ;ditorial or Advertisement pages f this issue, please complete one r more of the attached cards ntering the reference number(s). 'our enquiries will be passed on to BUSINESS REPLY SERVICE ie manufacturers concerned and Licence No. 12045 ou can expect to hear from them irect in due course. Cards posted WIRELESS WORLD, "om abroad require a stamp. READER ENQUIRY SERVICE, 'hese Service Cards are valid for ix months from the date of 429 BRIGHTON ROAD, ublication. CROYDON, 'lease Use Capital Letters SOUTH SURREY f you are way down on the CR2 9PS irculation list, you may not be vetting the information you -equire from the journal as IMM -CUT FIERE r. MEP IL. oon as you should. Why not Enquiry Service for Professional WIRELESS WORLD Wireless World, April 1977 -(ave your own copy? Readers Please arrange for me to receive further details of the products listed, the appropriate reference numbers of which have been entered in the 'o start a one year's subscription WW.... WW. space provided. ou may apply direct to us by WW.... WW. Name sing the card at the bottom of WW.... WW. Name of Company =his page. You may also apply to WW.... WW.... WW. he agent nearest to you, their Address WW.... WW. ddress is shown below. WW.... WW. OVERSEAS SUBSCRIPTION AGENTS WW.... WW. Telephone Number

ustralla: Gordon & Japan: Western Publica- WW.... WW. otch (Australasia) Ltd, tions Distribution Agency, PUBLISHERS A/E 90 Lonsdale Street, 170 Nishi -Okubo WW.... WW. USE ONLY lelbourne 3000, Victoria 4- chome, Shinjuku -Ku, Tokyo 160 WW . . WW . elgium: Agence et Position in Company lessageries de la Presse, Lebanon: Levant Distri- WW . . WW . Rue de la Petite -ILE butors Co., P.O. Box 1181, russels 7 Makdesi Street, Halim Nature of Company /Business Hanna Bldg, Beirut WW.. WW.

amide : Davis Circulation gency, 153 St. Clair Malaysia : Times WW.... WW. No. of employees at this establishment .venue West, Toronto 195, Distributors Sdn. Bhd., Inca rio Times House, WW. 390 Kim Seng Road, WW.... I wish to subscribe to Wireless World 9, Malaysia. '.yprus: General Press Singapore WW.... WW. gency Ltd, 131 Pro - VALID FOR SIX MONTHS ONLY : W. H. Smith P.O. Box Malta romou Street, Continental Ltd, 528, Nicosia 18a Scots Street, Valleta CUT HERE MIMI MN I MN=ttrt lenmark: Dansk New Zealand : Gordon & laddistribution, Gotch (New Zealand) Ltd, lovedvagtsgade8, 102 Adelaide Road, Ik.1103 Kobenhavn. Wellington 2

Inland : Rautakirja OY, Nigeria : Daily Times of .oivuvaarankuja 2, Nigeria Ltd, 3 Kakawa 1640 Vantaa 64, Finland. Street, P.O. Box 139, Lagos Wireless World: rance: Dawson- France .A., B.P.40, F- 91121, Norway: A/S Narvesens 'alaiseau Kioskompani, Bertrand Narvesens vei 2, Oslo 6 Aermany: W. E. Saarbach Subscription Order Form -3mbH, 5 Koln 1, Portugal: Livaria ollerstrasse 2 Bertrand s.a.r.l Apartado 37, Amadora 'àreece: Hellenic )istribution Agency, South Africa : Central To become a subscriber to Wireless World '.0. Box 315, 245 News Agency Ltd, P.O. iyngrou Avenue, Box 1033, Johannesburg ea Smyrni, Greece. please complete the reverse side of Spain: Comercial iolland: Van Ditmar N.V., Atheneum s.a. Consejo de this form and return it with your )ostelijke Handelskade 11, Ciento,130 -136 Barcelona Amsterdam 1004 15 remittance to: ndla : International Book Sweden: Wennegren louse, Indian Mercantile Williams A B. Fack S -104, Aansion Ext, Madame 25 Stockholm 30 lame Road, Bombay 1 Subscription Manager, Switzerland : Naville & ran: A.D.A.,151 Khiaban Cie SA, Rue Levrier 5 -7, I --oraya, Tehran CH -1211 Geneve 1 PC Business Press, Schmidt Agence AG, Savogelstrasse 34, srael : Stelmatzky's Oakfield House, Perrymount Road, Agency Ltd, Citrus House, 4002 Basle '.0. Box 628, Tel Aviv U.S.A.: John Barios, Haywards Heath, Sussex RH16 3DH, taly: Intercontinental IPC Business Press, .a.s. Via Veracini 9, 205 East 42nd Street, England t0124 Milano New York, N.Y. 10017 www.americanradiohistory.com Enquiry Service for Professional Readers WIRELESS WORLD Wireless World, April 1977

Please arrange for me to receive further details of the products listed, WW.... WW.... WW ADVERTISEMENT the appropriate reference numbers of which have been entered in the OVERSEAS AGENTS WW.... WW.... WW space provided. WW.... WW Name France M. D. Soubeyran, Compagnie WW.... WW.... WW Name of Company Francaise D'Editions, Division WW WW.... WW.... Internationale, 40 Rue du Colisee, Address WW.... WW.... WW I Paris 8e- Telephone : 225 -77 -50 -

WW.... WW ITelex : 280274 WW.... WW.... WW Telephone Number Hungexpo WW.... WW.... WW Hungary Mrs. Edit Bajusz, = Advertising Agency, Budapest XIV, WW PUBLISHERS A/E i WW.... WW.... USE ONLY iVarosliget- Telephone :225008-

WW.... WW.... WW Telex : Budapest 22 -4525 INTFOIRE WW.... WW.... WW Position in Company

WW.... WW.... WW Nature of Company /Business I Italy Sig. C. Epis, Etas - Kompass, S.p.a. - Servizio Estero, Via Mantegna 6, WW.... WW No. of employees at this establishment 20154 Milan - Telephone 347051 - WW.... WW.... WW I Telex : 37342 Kompass WW.... WW.... WW VALID FOR SIX MONTHS ONLY I Japan Mr. Inatsuki, Trade Media - IBPA 111111111 SCUT HERE (Japan), 8212 Azabu Heights, 1-5-10 Do not affix Postage Stamps if posted in IRoppongi, Minato -ku, Tokyo 106- Gt. Britain, Channel Islands or N. Ireland Telephone : (03) 585 -0581 Postage will 1 be paid by Licensee IUnited States of America Ray Barnes, I*IPC Business Press, 205 East 42nd Street, New York, NY 10017 -Telephone:

I(212) 689 5961 -Telex : 421710 Mr. Jack Farley Jnr., The Farley Co., I Suite 1548, 35 East Wacker Drive, BUSINESS REPLY SERVICE Chicago, Illinois 60601 -Telephone: Licence No. 12045 (312) 6 3074 Mr. Richard Sands, Scott, Marshall, WIRELESS WORLD, Sands & Latta Inc., 5th Floor, 85 Post Street, San Francisco, California 94104 -

READER ENQUIRY SERVICE, Telephone : (415) 421 7950 - Telegrams: Dascottco, San Francisco 429 BRIGHTON ROAD, Mr. William Marshall, Scott, Marshall, i i Sands & Latta Inc., 1830 West Eighth SOUTH CROYDON, Street, Los Angeles, California 90057 -

Telephone : (213) 382 6346 - SURREY Telegrams : Dascottco., Los Angeles CR2 9PS Mr. Jack Mentel, The Farley Co., Suite 605, Ranna Building, Cleveland, Ohio 4415 -

no CUT HERE IR.r Telephone : (216) 621 1919 Mr. Ray Rickles, Ray Rickles & Co., P.O. Box 2008, Miami Beach, Florida Wireless World Subscription Order Form Wireless World, April 1977 I 33140- Telephone : (305) 532 7301 I Mr. Jim Parks, Ray Rickles & Co., UK subscription rates USA & Canada subscription rates 3116 Maple Drive N.E., Atlanta, Georgia I 30305. Telephone : (404) 237 7432 1 year: £7.00 1 year: $18.20 I Mike Loughlin, IPC Business Press, 15055 Memorial, Ste 119, Houston, Texas 77079 -Telephone: (713) 7838673 Please enter my subscription to Wireless World for 1 year Canada Mr. Colin H. MacCulloch, International Advertising Consultants Ltd., I enclose remittance value made payable to 915 Carlton Tower, 2 Carlton Street, PRESS Ltd. IPC BUSINESS Toronto 2 - Telephone (416) 364 2269

Name I Also subscription agents

Address I I I

I WW -003 FOR FURTHER DETAILS www.americanradiohistory.com ITTON 22 ...the onlyspeaker that could successfully come between the famousl5 &33. The Celestion Ditton 22 has been delivering the sort of sound you would added to the popular Ditton series normally expect from a much larger F:nd this coupon for literature or ask your dealer for a especially for the discerning audiophile loudspeaker. demonstration. who demands large system performance, You don't have to take our word for but cannot accommodate a big it -why not audition the Ditton 22 at your Name loudspeaker. local dealer's showroom. We are sure that Utilising an 8 inch bass unit and you will hear what we mean. Address 5 inch mid -range, specially designed and built by Celestion, plus the impressive 0% mua HD 1000 dome tweeter, the Ditton 22 is a Celestion Rola Celestion Ltd., Ditton Works, Foxhall Rood, Ipswich, Suffolk IP3 8JP compact 3 way system capable of Ilr Telephone:Ipswich(0373)7 3131. Cables :Voicecoil,Ipswich.Telex:98365 - www.americanradiohistory.com

wer, `... S wor

n 1.r redtxtr>.

Wireless World Dolby noise reducer Trademark of Dolby Laboratories Inc. .011 We are proud to announce the latest addition to our range of matching high fidelity units.

Featuring switching for both encoding (low -level h.f. compression) and decoding Typical performance a switchable f.m. stereo multiplex and bias filter Noise reduction better than 9dB weighted (as in USA) provision for decoding Dolby f.m. radio transmissions Clipping level 16.5dB above Dolby level (measured at 1% third harmonic no equipment needed for alignment content)

suitability for both open -reel and cassette tape machines Harmonic distortion 0. 1 % at Dolby level typically 0.05% over most of band, check tape switch for encoded monitoring in three -head machines rising to a maximum of 0.12% Signal -to -noise ratio: 75dB (20Hz to 20kHz, signal at Dolby level) at The kit includes Monitor output -complete set of components for stereo processor Dynamic Range >90dB 30mV sensitivity. -regulated power supply components -board -mounted DIN sockets and pushbutton switches -fibreglass board designed for minimum wiring -solid mahogany cabinet, chassis, twin meters, front panel, knobs, mounting screws and nuts PRICE: £37.90 +VAT IAlso available ready built and tested Price £52.00 +VAT

Calibration tapes are available for open -reel use and for cassette (specify which) Price £2.00 +VAT

rM Single channel plug -in Dolby PROCESSOR BOARDS (92 x 87mm) with gold plated contacts are available with all components Price £7.20+ VAT

Single channel board with selected feet Price £2.20 +VAT

Gold Plated edge connector Price £1.40 +VAT*

Selected FETs 60p each +VAT, 100p +VAT for two, £1.90 +VAT for four

Please add VAT 121/2% unless marked thus ", then 8% applies -sales and servicing facilities on all our kits, have Aft We guarantee full after technical Iw, n wnh 4irn you checked that these services are available from other suppliers? EIIiOC qp

BARCLAYCARD Blaster charge

Please send SAE for complete lists and specifications Portwood Industrial Estate, Church Gresley, Burton -on- Trent, Staffs D E 11 9PT INTEGREX LTD. Burton -on -Trent (0283) 215432 Telex 377106

www.americanradiohistory.com INTEGREX S- 2020TA STEREO TUNER /AMPLIFIER KIT SOLID MAHOGANY CABINET 1014onno S- MCA NOMMINEMERES A high -quality push -button C)CCCCC ..., FM Varicap Stereo Tuner combined } i s with a 24W r.m.s. per channel Stereo Amplifier. Brief Spec. Amplifier Low field Toroidal transformer, Mag, input, Tape In /Out facility (for noise reduction unit, etc.), THD less than 0.1% at 20W into 8 ohms. Power on /off FET transient protection. All sockets, fuses, etc., are PC mounted for ease of assembly. Tuner section uses 3302 FET module requiring no RF alignment, ceramic IF, INTERSTATION MUTE, and phase -locked IC stereo decoder. LED tuning and stereo indicators. Tuning range 88- 104MHz. 30dB mono S/N La7 h.2..V. THD 0.3 %. Pre- decoder 'birdy' filter. PRICE: £53.95 +VAT NELSON -JONES STEREO FM TUNER KIT A very high performance tuner with dual gate MOSFET RF and Mixer front end, triple gang varicap tuning, and dual ceramic filter/ dual IC IF amp.

Brief Spec. Tuning range 88- 104MHz. 20dB mono quieting @ 9.75;N. Image rejection - 70dB. IF rejection Mono £29.15 +VAT - 85dB. THD typically 0.4 %. IC stabilized PSU and LED tuning indicators. Push -button With ICPL Decoder £33.42 +VAT tuning and AFC unit. Choice of either mono or stereo with a choice of stereo decoders. With Portus- Haywood Decoder Compare this spec. with tuners costing twice the price. £35.95 +VAT

STEREO MODULE TUNER KIT A low -cost Stereo Tuner based on the 3302 FET RF module requiring no alignment. The IF comprises a ceramic filter and high - performance IC Variable INTERSTATION MUTE.

Sens. 30dB S/N mono @ 1 .2µV PLL stereo decoder IC. Pre -decoder 'birdy' filter THD typically 0.3% Tuning range 88- 104MHz PRICE: Mono £26.85 +VAT LED sig. strength and stereo indicator Stereo £29.95 +VAT S -2020A AMPLIFIER KIT Developed in our laboratories from the highly successful "TEXAN" design. PC mounting potentiometers, switches, sockets and fuses are used for ease of assembly and to minimize wiring Power 'on /off' FET transient protection.

'Typ Spec. 24 +24W r.m.s. into 8 -ohm load at less than 0.1% THD. Mag. PU input S/N 60dB. Radio input S/N 72dB. Headphone output. Tape In /Out facility (for noise reduction unit, etc.). Toroidal mains transformer. PRICE: £31.95 +VAT

ALL THE ABOVE KITS ARE SUPPLIED COMPLETE WITH ALL METALWORK, SOCKETS, FUSES, NUTS AND BOLTS, KNOBS, FRONT PANELS, SOLID MAHOGANY CABINETS AND COMPREHENSIVE INSTRUCTIONS

BASIC NELSON -JONES TUNER KIT £14.28 +VAI PHASE -LOCKED IC DECODER KIT X4.47 +VAT BASIC MODULE TUNER KIT !stereo) £16.75 +VAT PUSH -BUTTON UNIT £4.50 +VAT

PORTUS- HAYWOOD PHASE -LOCKED STEREO DECODER KIT £8.00+VAi

www.americanradiohistory.com Wireless World, April 1977 HART ELECTRONICS The Only Firm for Quality Audio Kits J. L. Linsley -Hood High Quality Cassette Recorder

Master Board with one Replay Amp removed As these circuits in recent issues of "Wireless World" are capable of LENCO CRV CASSETTE MECHANISM High Quality, robust cassette transport for Linsley Hood Recorder. Features fast forward, such an excellent performance we feel that it is not sensible to sacrifice fast rewind, record. pause and automatic cassette ejection facilities. Fitted with this potential by designing a kit down to a price. We have therefore Record /Play and Erase Heads and supplied complete with Data and extra cassette ejection for spent a little more on professional hardware allowing us to design a spring above horizontal use Ex -stock E19.10 + E2.38 VAT. very advanced modular system. This enables a more satisfactory 71 x Complete set of parts for Master Board, includes Bias oscillator, electrical layout to be achieved, particularly around the very critical Relay, Controls, etc. £9.83 + £1 .23 VAT. input areas of the replay preamps. These are totally stable with this 72x Parts for Motor Speed and Solenoid Control for Lenco CRV Deck. layout and require no extra stabilising components. Many other £3.52 + 44p VAT. advantages also come from this system which has separate record and 73x Complete set of parts for stereo Replay Amps and VU Meter replay amps for each channel plugging in to a master board with gold Drive. £8.12 + £1.02 VAT. plated sockets. The most obvious is the reduction of crosstalk and 74x Complete set for Stereo Record Amps. £6.74 + 84p VAT. interaction which could cause trouble on a single plane board, with our 475x Complete set of parts for Stabilised Power Supply including modular system the layout is compact but there is no component special Low Hum field Mains Transformer. This unit is a separate crowding. Testing is very easy with separate identical modules and 3.5" x 5" PCB designed so that the motor control board fits above building with the aid of our component -by- component instructions is it to save space. £8.79 + £1.10 VAT. childishly simple, but the finished result is a unit designed not to 700M. VU Meters Individual high quality meters with excellent normal domestic standards but to the best professional practice. ballistics and built -in illumination. £8.48 + £1.06 VAT PER ALL PARTS ARE POST FREE PAIR. Please send 9 x 4 SAE for lists giving fuller details and Price breakdowns, A suitable Metalwork and Front Plate is now available Penylan Mill, Oswestry, Salop Personal callers are always welcome but please note we are closed all day Saturday

The Finest KEYBOARDS The "S.K.A. " Plastic Keyboard was developed by Kimber Allen Ltd in co- operation with a Swedish company and the manufacturers state that in their opinion it is the finest moulded plastic keyboard made and is not to be confused with cheaper keyboards available. The keys are moulded in Acrylic plastic, a material chosen for its hard wearing properties and ideal feel to the touch. They are moulded in two parts, the key face, which has to be perfect in appearance and finish, and the action, which has to be strong and carry the mechanism. The strong section of aluminium extrusion 0000 upon which they are mounted is specially designed to take all the & pressures of playing. Springs, felts, and contact actuators are CONTACTS supplied ready- fitted. The contact assemblies are constructed of laminated bakelite, thus giving smooth slot walls and completely free movement of the gold -clad contact wires. Types available as follows (Contact pairs normally open):

GJ -SPCO: 24p each GE -4 pairs : 45p each GB -2 pairs: 27p each GH -5 pairs : 57p each GC -3 pairs: 36p each 4PS -SPCO & 3 prs : 53p ea U.K. POST & HANDLING: 37 Note C -C Keyboard : We also stock kits and PCBs for the P.E. Synthesiser, P.E. Joanna Keyboards: £1.50 each £24.85 (electronic piano), P.E. Minisonic, and other sound synthesising Contacts: 49 Note C -C Keyboard : and modifying projects published in Practical Electronics. Send Orders under £15.00: 25p £29.50 SAE for full list (Overseas send 40p). Orders over £15.00: 50p 61 Note C -C Keyboard : £34.50

VAT: Add 12 '/2 % to final total on all U.K. orders EXPORT ORDERS ARE WELCOME but please see our price PHONOSONICS list for Export Postage Rates. N.B. EIRE, CHANNEL ISLES & DEPT. WW74, 22 HIGH STREET B.F.P.O. classify as Export. MAIL ORDER AND C.W.O. ONLY - SORRY BUT NO CALLERS PLEASE SIDCUP, KENT DA14 6EH Prices are correct at time of Press, E. & O.E. Delivery subject to availability

WW -018 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 105

4x4 STEREO 20 x 20 WATT STEREO AMPLIFIER r '". AMP KIT _._ -.. _ £2990 0.; £14.50 PflPf2OJ J.210

For the experienced constructor who wants to 35 -WATT DISCO design his own stereo. kit includes all necessa'y AMP components including constructors manual. Here's the mono unit you need to start off with. you watts rms, 70 Plus Pair of easy to build 4 watt speakers in kit Superb Viscount IV unit in teak-finished cabinet.Silverfascia with aluminum Gives a good solid 35 watts peak output. Big features include two form. with teak simulate fi, , .brnets rotary controls and pushbuttons, red mains indicator and stereo jack inputs, for tape 12 "x9 "x5 socket. Function switch for mic, magnetic and crystal pick -ups, tape, tuner. disc both ceramic cartridges, input microphone input. mixing .J and auxiliary.Rear panel features two mains outlets,DlN speaker and input and Level sockets, plus fuse. 20 + 20 watts rms, 40 + 40 watts peak. controls fitted with integral push -pull switches. inclMirl.0 20, Independent bass and treble L 50 controls and master volume. 27. pu p't so 20 WATTS STEREO AMPLI ER KIT HW YOU CAN AVE WITH PZ 20 POWER UNIT FANTASTIC YSTEM 18 For only £80, you get SYSTEM 2 Comprising our 20 +20 A build - it- yourself stereo power SAVING e 20+20 watt Viscount IV amplifier, watt Viscount IV amplifier: a pair of amplifier with latest integrated circuitry.l0 pair of our 12-watt-rms Duo Type our large Duo Type Ill matching RMS per channel output, full short-circuit b matched speakers; a BSR MP 60 speakers which handle 20 watts rms and overheat protection.C1X, £ ' Párc type deck complete with magnetic each, and a BSR MP 60 type deck to with PZ20 Power Supply cartidge, de luxe plinth £8000 with magnetic cartridge, £9200 and cover. PORTABLE DISCO CONSOLE , p S p rR oo de luxe plinth and cover. . pSpf10A0

Carnage surcharge to Scotland System 1P . 2 5C with built -in pre -amplifiers DIY SPEAKER KITS Here's the big -value portable disco console SPEAKERS Two models- Duo Ilb, TURNTABLE Popular BSR from RT -VC! It features a pair of BSR MP 60 EASY -TO -BUILD teak veneer, 12 watts rms, 24 watts MP 60 type, complete with magnetic type auto -return, single-play professional series record decks. Plus all the controls and WITH ENCLOSURE peak, 18'/2" x 13'/2" r. 7'/!" approx. cartridge, diamond stylus, and L PER PAIR features fabulous de luxe plinth you need to give disco Specially designed by 34 p &p0-650 performances. Simply RT -VC for cost -conscious and cover. £6400 Duo Ill, 20 watts connects into your existing J hi -fi enthusiasts, these + mis, 40 watts peak, slave or external amplifier. p S p £6.50 kits incorporate two teak - £29°° 27" x" 13" x 111/2" pSp simulate enclosures, approx. fa twoEMI13 "x8" PER PAIR 50 £52 p8p f7 so (approx.) woofers, two tweeters and a pair of matching crossovers. Easily constructed, using a few basic 30 x 30 WATT tools. Supplied complete with an easy -to- follow circuit diagram, and crossover AMPLIFIER components. Input 15 watts KIT £ 50 Specially designed 70 &100 WATT DISCO AMPS rms. 30 watts peak, each unit. by RT -VC for the 25 experienced constructor, this kit Brilliantly styled for easy disco performance! Cabinet size 20"x11"x9v2" PER PAIR comes complete in every Sloping fascia, so that you can use the (approx). p 8 p £5.50 detail. Same facilities as Viscount IV amplifier. controls without fuss or bother. Brushed aluminium fascia rotary Five Chassis is ready punched; drilled and formed Cabinet is finished in teak and controls. £17.00 smoothacting,vertically mounted slide controls 15 -WATT KIT IN STEREO veneer. Black fascia and easy -to-handle aluminium knobs. £2900 - master volume, tape level, mic level, deck CHASSIS FORM E3.40 P b P PAIR Output 30 +30 watts rms, 60 +60 peak. + p S p f 2 10 level, PLUS INTER -DECK FADER for perfect When you are looking fora good graduated change from record deck No. 1 to speaker, why not build your own from No. 2, or vice versa. Pre -fade level control this kit. It's the and which we supply BSR T145 (PFL) lets YOU hear next disc 70 WATT with the above enclosures. Size 13" x 8" before fading it in. VU meter (approx.)woofer (EMI),tweeter, 8 -TRACK £4900 monitors output level 70 watts and matching crossover. Power CARTRIDGE rms, 140 - P 3pì3 00 handing capacity 15 watts rms. watts peak output. PLAYER MECHANISM All the big features as on the 30 watts peak. 100 WATT Requires some atten- £695 70-watt disco amplifier, but £6500 tion. Complete with built with a massive 100 watts rms. , 4 'COMPACT' FOR TOP VALUE in pre -amp, A.C. 240V - p S p E f 50 200 watts peak output power. - o o How about this for incredible bookshelf value from RT -VC! A pair of high efficiency STEREO CASSETTE DECK KIT units for only £7.50 - just what you need TOURIST IV PUSH BUTTON Again, is for low -power amplifiers. These infinite this kit specially designed for the experienced constructor mounting into his baffle enclosures come to you ready CAR RADIO KIT -for mitred and professionally finished. Each own cabinet. Features include solenoid- assisted cabinet measures 12"x9"x5" (approx.) - AUTO-STOP, 3- digitcounter, record/replay deep, and is in wood simulate PCboard,mains transformer ana input £3250 eir Complete with two 8" and output controls. AC BIAS AND ERASE. £ 50 +pap£1.50 (approx.) speakers for max. 7 Per parr power handling of 7 watts. - p a p £1 70 DELUXE ACCESSORY KIT Comprises of a matched pair of £395 MOTOR TOP 10 AWARD dynamic mics. and two replacement slider level controls. p g p £ 1.00 Complete with speaker, baffle and This item post POST FREE when purchased with Cassette Deck kit fixing strip The Tourist IV for the BSR experienced constructor only. The Weare unable to show alour ALL PRICES INC.VAT. AT 12 ° products. so please Tourist IV has five push buttons, four GOODS NOT DESPA7CHEDOUT5 /Df Ur o TURNTABLES Send Stampedaddressedenvelope medium band and one for long wave All items subject to availability . Price correct BSR MP60 TYPE at Ist February 1977. and subject to change tor our fully descnpbve catalogue and any band. The tuning scale is illuminated Single play record player uvuhout "ut , , further information. and attractive small aluminium control (Chassis form) less cartridge f15.95 knobs are used for manual tuning and Cartridges to suit above P ti P E2.00 volume control. Minimum order on ACOS MAGNETIC STEREO . . £4.95 The modern style fascia has been designed to blend C Access and R E15 with most car R Barclaycards CERAMIC STEREO . £1.95 Interiors and the finished radio will slot into a standard car radio aperture. Size BSR automatic record player deck DO NOT SEND approx 7" s ' u 4',' Power Supply 21E HIGH STREET, ACTON, LONDON W3 6NG (Chassis form) with cueing device Nominal 12 volts positive or negative £ 323 EDGWARE ROAD, LONDON, W2 CARD earth (altered O Just wnte your Order and stereo ceramic head E9.95 internally) Power t 5 p 50 Personal Shoppers EDGWARE ROAD 9am - 5 30p m., Had day Thurs giving your credit Ouptut 4 watts into 4 ohms. PhPE2.00 ACTON Mail Order only No Callers card number

www.americanradiohistory.com 106 Wireless World, April 1977 VALVE MAIL ORDER CO. Climax House, 159 Fallsbrook Rd , Streatham London SW16 6ED R Tel: 01 -677 2424 Telex: 946 708 ECH81 0.35 EY86 0.50 PCL85 0.80 613.16 0.80 12406 0.80 705A CV133 CV4002 L'F4I 0.75 6060 EN3l QA240 VALVES ECH83 050 EZ40 0.05 PC 1,86 0.50 UF89 0.50 6BQ7A 055 124E6 0.75 INDUSTRIAL 715A CV135 Cí'4003 6061 EN32 QA2403 AZ31 1.00 ECH84 15e EZ4I 0.75 PD500 3.00 U L41 0.75 6BR7 3.00 12AT6 0.45 715B CV136 CV4004 VALVES 6062 EN91 QA2404 AZ4I 0.70 ECL80 9.00 EZ80 93e PEN45DD ULM 0.50 BS7 4.00 12ÁT7 0.45 723A/B CV137 CV4005 ESU74 I B3GT 5B/255M QA2406 CBL3I 1.40 ECL82 0.42 EZBI 0.31 0.75 UY41 0.55 sews 3.00 12AÚ6 0.50 725A CV138 CV4006 ESU76 1B24 5B/256M 6067 QA2407 CL33 1.50 ECL86 035 EZ90 0.45 0-7( ÚY85 0.45 6BW7 1.12 I2AU7 6.38 CV140 CV4007 ESU77 1B35A 257M 6072 Q83/300 CY3I 1.00 EF37A 3.0 GY501 1 P1_36 0.M VP4B 1.25 6C4 0.40 I2AX7 038 50/ 801 CV 144 CV4008 1863A 5C22 6073 QB3-5750 DAF91 0.40 EF39 1.78 GZ30 P1.38 I VR7530 6CD6GA 2.50 12BA6 030 803 6074 CVIO CV4009 Fú057 1N21 5D21 84-1100 DAF96 0.0 EF41 0.75 ltZ32-"` 01 PL81 0.55 055 6DC6G 1.00 1213E6 0.09 805 CV 173 CV4010 IN21B 6080 F6060 F41 DCC90 1.35 EF55 1.50 t;Z34 P192 0.56 VR105B0 OCHE 3.85 12BH7 0.60 5R4GY 807 CV187 CV'4011 1N23B 6097C F6061 QF DF91 0.40 EF80 0.35 H63 03e PIB3 0.50 0.40 6E5GT 1.50 30C 15 1.00 5U4GB 808 CV188 CV4012 IN23CR 6130 F6063 QQV02-6 DF96 0.80 EF85 0.45 HLD4lDD P1.34 050 VR150/30 6F23 0.90 30C 17 1.00 5Z3 811 CV190 CV4013 IX2A 5Z4G 6136 QQV03-10 DK91 0.50 EF86 (Jap) 570 PL504 0.N 0.450 6E28 0.98 30C 18 128 81IA CV220 CV4014 FX2125 1X2B 6189 QQV03-20 DK92 1.00 0.90 HN309 1.50 PL508 112 YR3 125 635G 0.45 30F5 1.00 8124 6197 CV261 CV4015 FX227 QQV05-20A DK96 0.75 EF86(USSR; K r61 3.41 PL509 2.16 I05 030 6JSGT 0.55 30FLI 1.00 6AF4A 813 CV273 CV4016 2A3 6201 QQV04-15 D192 0.50 0.40 KT66 4.00 PI.801 1.00 155 0.M 6J7GT 0.45/ 30E12 1.00 6AK5 815 CV284 CV4017 GI 1371K 24515 6202 QQV06-40 DL94 0.85 EF86 (Mul KT81 (7C5) PI902 19e 1T4 e.40 O.BÓ 30FL14 128 6AM5 828 CV286 CV4018 G120/IB 2C26A 6203 QQV06-411A D196 0.55 lard) 2.94 2.00 PY32 0.63 304 0 ^6R7í,7 0-3 301.15 0.95 6AM6 8298 CV287 CV4019 G150/28 2C34 6205 QS70/20 DM70 0.70 EF89 0.35 K 88.118075 PY33 503 3V4 0.85 tt8B7'-F.50" 301.17 0.05 6AN5 8300 CV3I5 CV4020 G180/2M 2C39A 6AN8 6360 Q575/20 DY86/7 0.45 EF91 6.85 KTW61 131 PY81/800 5R4GY 120 6L6GC 1.20 30P12 1.0 860 CV329 CV4022 G 240/2D 2C43 6AR5 6442 Q575/40 DY802 0.47 EF92 6.75 KTW62 LSO 0.50 5U4G 1.25 6P25 3.00 30P19 0.95 866 6463 CV337 CV4023 G40/1K Q575/60 2D21 6AS6 EABC80 0.38 EF95 (USSR) N78 7.50 PY82 0.45 5V4G 0.65 OQ7GT 0.43 30PL1 0.15 666A CV342 CV4024 GN9 QS83/3 2021 W 6AU4GTA 6550 EAF42 0.70 0.45 082 0.45 PY83 0.50 5Y3GT 965 6SG7 0.50 30PL13 1.44 866E 6807 CV 345 CV4025 GT IC QS92/10 2E26 6A U5G T CV354 EAF801 0.75 EF95 (UK) OB2 0.45 PY500A 1.36 5Z4G 30PL14 1.80 872A 6923 CV4028 GTRI2OW Q595/10 2331 6AU6 EBC33 1.00 1.N OZ4 0.35 PYf101 0.55 6.3011 0 6SL7GT 0.551 35L6GT 0.80 881R CV359 CV4033 GTRIOMS QS105/45 2333 6AV5GTA 6939 CV4035 EBC4l 0.75 EF98 11.00 PC86 0.05 U25 1.00 6AK5 9N16F-YáV 35W4 0.00 891R CV360 GUIS QS150/40 0.40 2150 6AW8A CV4038 GU20/21 EBC8I 0E183 040 PC88 0.65 U26 0.85 (USSR)) 0.45 6U4GT 0.75 35Z3 0.00 7193 CV371 QS150/45 0.40 2354 6AX5GT CV372 CV4039 GU50 08E80 0E184 0.M PC900 0.55 U 191 0.75 64K5 (11K) -I.55 35Z4GT 0.70 954 7203 QS150/80 0.40 2J56A 68413 CV378 CV4040 GXUI 00E83 EH90 960 PCC84 0.45 U404 0.75 1. 6V6GT 0.60'I 5005 0.70 955 7360 QSI 200 EBF89 0.32 2K25 6BA8A CV391 CV4056 KT66 EL33 3.40 PCC89 0.55 1, is 6AL5 0 956 7566 QS1202 00131 2.0 6X5GTT/G64S 2K26 6BK4 CV395 CV4059 KT67 EL34 1.20 PCCI89 0.85 Ú BIC80 0.40 6AQ5 050 80 9.75 6BK7A 957 QS1203 0.55 2K28 CV397 CV4060 KT88 EL37 3.40 PCF80 0.40 UAF42 0.75 6AS7G 807 -l.N 6BL7GTA 6103 QS1205 2K45 CV428 CV4062 ECC81 0.45 126 PCF86 0.85 UBC41 0.60 (USSR) 1.00 786 0.80 81 1625 2X2A 6BN6 60254 CV434 CV4063 QU37 ECC82 0.38 L42 1.65 PCF801 0.88 UBF80 050 6AS7G(UK) 7137 0 M8079 6BR7 CV447 CV4064 QV03-12 ECC83 0.8 L84 0.35 PCF802 0.72 UBF89 0.541 4.50 7C5 M8080 A/107A 6057 2050 9001 CV449 CV4079 QV04-7 6:45 EL9I 2.011 PCF805 128 UCC85 0.58 '6AT6 0.60 7C6 2050W M8081 A/108A 6BX7GT 9002 CV466 CV450I QV05-25 ECC88 0.50 EL95 IAN PCF80 0.80 UCH42 0.80 6AU6 0.40 7117 0 80 2051 M8082 /108B 6BZ6 9003 CV469 CV4502 QV06-20 ECF80 0.45 E1160 1.75 PCF808 128 UCH81 0.50 6AV5 050 7R7 M8083 6146.10 A, 1090 6CB6 9004 CV488 CV4503 QY3-125A ECF82 0.45 EM80 0.55 PC152 0.45 UC1.82 0.40 6BA6 038 7S7 2 6146A 280 40034 M8091 A/110A 6CH6 9005 CV491 CV4504 QY4.250A ECH35 130 EM8I 1.M PC1.83 0.70 UCL83 1.25 60E6 0.45 7Y4 0 6I46B 4212E or H 9006 M8096 QY4-400A 3A/IIOB 601.6 CV492 C V4507 M8097 ECH42 6.80 EY51 0.45 PCI.14 0.50 6BH6 120 12AC6 0.80 3A/1463 6CW4 4242A CV493 CV4506 M8098 TUBES 3A/167M 6DK6 4313C 13201A RIO SN7406 0.42 SN74110 0.58 CV717 CV5060 M8100 0071 0.25 2N1304 0.45 2BP1 7.60 3A5 6DQ6B 43284 R17 TRANSISTORS & ICs 0.45 SN7407 0.42 5N74111 0.88 CV808 CV6004 M8136 0072 2N1305 545 313P1 0100 30/240M 60.48 4687 A 1834 R18 0.07 028 SN74118 0.90 CV1072 CVfi008 AA119 BFI81 0.30 OC76 0.45 2N1306 050 SN7408 3DPIA 4.00 36/241M 6F33 5544 A2087 M8137 AAZ13 0.18 BF199 01I0 SN7409 0.213 SN74119 1.68 CV 1076 CV6045 M8140 0077 0.75 2N1307 0.50 3EG1 0100 3024 6196 (metal) 5545 A2134 SIlE12 AAZ15 1.12 0F195 6.10 0.50 SN7410 0.10 SN74121 0.50 CV1092 M8141 0081 2N1308 0.541 3FP7 2.00 3028 6K7GT A2293 5130 AC107 0.75 0F197 0.12 SN741 I 0.25 SN74122 0.70 C V 1219 DÁ30 M8142 OC81 D 028 2N1309 5.50 3GP1 5.00 31329 6U8A 5642 42426 5130P AC126 625 BF200 012 SN7412 SN74123 1.00 CV1343 DA41 OC81 Z I.00 2N1613 0.21 030 5BP1 8.00 3C22 6V6GT 5644 A2521 M8144 STV280/40 AC127 025 5N74141 0.90 CV 1475 DA42 BFS61 0.25 0083 0.55 2N2147 1.211 SN7413 030 5CP1 5.00 3C23 5651 A2900 M8149 STV280/80 AC128 5.22 0.25 030 SN74145 1.20 CV 1476 DA10 BF598 OC140 ISO 2N2369A 025 SN7416 88D 1500 3C24/24G 11E3 5670 ACTE M8157 SU41 AC176 0.27 BF1V10 0.01 0.30 SN74150 1.75 CV 1477 DET22 OC170 0.50 2N2646 550 SN7417 CV429 27.50 3C45 11E13 5672 ACTS M8161 SU42 AC187 0.25 028 0.10 5N74151 1.00 CV1478 M8162 BFX29 050 2N2904 3025 SN 7420 DG7-5 18.0 3CX100A5 12AY7 5676 AC188 025 BFX88 023 1.00 0.25 SN74154 20 CV1794 ESSI M8163 OC00 2N2904A 0.25 SN 7422 vCR138 16.00 3E29 12844 5687 BIC IE TD03-10 ACY2I 053 0.21 OC201 1.75 SN74155 1.01 CV1480 E80CC M8I67 BFY50 2N2905 0.30 SN7423 037 VCR 139A 3J/121E 12BY7A 5696 BS90 TT15 ACY39 1.00 BEYS' 0.21 OC202 1.50 5147425 037 SN74156 1.00 C V 1481 EOFC M8179 2N2904 0.25 8.e 3J/100E 12E1 5702 135156 TT21 AD140 0.65 BFY52 0]3 OC203 ISO SN7427 0.37 SN74157 0J15 CV1482 E80F M8190 2N2906 0.22 33/170E 12E14 5718 BT5 M8196 TTR3IMR AD149 585 0.4e OC P71 1.25 SN7428 0.40 SN74170 2.52 CV1787 EtlOL BRI00 2N2926 0.1S 3Q/150E 13E1 5719 0735 TZ40 ADI61 5.45 ORP12 0.0 SN7430 0.16 SN74174 1.57 CV1832 E807 M8204 BY10 0.45 2N303 020 3Q/195E 2807 5725/ BT45 AD162 045 BY126 1.12 ORP60 0.85 SN7432 0.37 SN74175 1.10 CV 1833 E81CC M8212 U17 2N305 0.M 354 29C1 6AS6W BT79 M8214 AF115 025 BYI27 0.12 TIC44 0.30 SN7433 0.37 SN74176 1211 5726- CV1835 E81L U19 2N3525 0.0 3V /3408 53KU BT83 E82CC M8223 AF116 025 BFX61series TIC226D 1.40 1.00 SN7437 0.37 SN74190 2.4111 6A1.5W CV1994 U27 2N3614 3V/390A 7581 E83CC M8224 AF117 0.25 e,2e TIL209 0.22 2N3615 ISO 5N7438 0.37 SN74191 2.00 5727- CV2000 3V/390B 75C 1 CIC M8225 AF186 I00 BZY88serles ZTX107 0.10 0.1S 5N7440 0.22 SN74192 200 CV2131 E83F VLS631 2N3702 83A1 2D21 W CIK E88CC M8232 AF239 0.45 0.12 ZTX108 0.10 2N3703 0.13 SN7441AN 0.12 SN74193 2.M 5749 CV2154 4 -125A 8541 CV5 E9OCC M8237 ASY27 1.45 545 ZTX300 0.12 2N3704 SN7442 570 SN74194 119 5750 CV2155 Z300T CRSI-05 e.15 4.250A 6542 CV25 E9OL M8245 ASY28 11.25 ZTX301 0.13 SN7450 9.11 SN74195 1.1e CV2160 Z759 CRSI-40 ISO 2N3705 0.13 4-400A 90AG 5751 CV26 E9IH MEI400 BA102 0.25 ZTX302 0.17 SN7451 0.16 SN74196 1.241 5802 CV2179 Z803U CR53-05 0.45 2N370 0113 41332 90AV CV28 E92CC ME1401 BA115 0.15 ZTX304 0.22 SN7453 0.10 SN74197 1.25 CV2235 CR53-40 575 2N3707 513 4C35 9001 5814 CV31 E180CC BC107 514 ZTX500 0.12 SN7454 0.10 SN74198 2.77 CV2237 MJE340 0.42 2N3708 0.00 4CX250B 90CG 5823 CV32 CV2238 EA50 OA2 BC108 514 0.03 ZTX501 0.13 SN7460 0.10 SN74199 2.52 MJE370 2N370 512 4E27 90CV 5840 CV45 CV2253 EA52 0A3 BC109 0.15 ZTX503 0.16 SN7470 e10 MJE520 060 2N3710 6.13 4350 95A1 5963 CV53 CV228.9 EA76 OA4G BC113 0.15 MJE2955 1.25 ZTX531 0.25 SN7472 038 2N371 1 0.13 4352 10TH 5965 CV73 ECC 35 OB2 BCII7 0.22 MJE3055 0.75 ZTX550 0.18 SN7973 0.41 CV2520 2N3819 015557 4352A 150B2 6005/ CV74 CV 2522 ECF804 OB3 BC143 0.30 0.40 SN7474 0.42 MPF102 IN914 0.0 2N3820 4353 15083 6AQ5W CVOS CV2721 EF50 BC147 0.10 MPF103 0.40 0.07 2N3823 6.10 SN7475 0.59 IN401 4X150A I SOCI 6021 CV 118 CV201 BC148 0.08 MPF104 0.40 0.45 IN402 0.07 2N3903 0115 SN7476 4X1500 150C2 034 CV121 CV 3523 003 BC 169C 0.15 MPF10 0.40 IN4003 0.08 011S SN7480 0.0 2N3904 4X250B 15003 6035 CV124 CV 3929 EF54 UG3 BC182 0.12 NE555 0.42 IN4004 0.80 SN7482 0.87 2N390 0.17 150C4 ' 057 CV128 CV3986 EFS5 OZ4 BC182L 0.12 NKT404 1.25 0.09 0.17 SN7483 1.10 IN400 2N3906 5B/251M 250TH 058 CV3988 EE804 OZ4A BC1841. 0.13 0A5 0.75 0.10 2N4058 e.10 SN7484 1.00 5B/252M 328 059 CV3991 EFPO BCY32 1.00 OAIO 0.55 IN407 0.11 0.47 2N4059 0.12 5N7486 329 CV131 CV3998 EL91 PTI5 BCY33 0.70 0A79 0.12 IN409 0.08 SN7490 0.55 2N400 0.13 CV132 CV401 EN30 BCY34 0.75 0A81 0.15 1N4148 0.80 2N401 0.1S SN7491A`. 1.00 BCY70 0.18 0A91 1.07 15921 0.80 2N4062 514 SN7492 0.70 BCY7l 0.22 0A200 0.10 152033 0.20 2N4289 0.30 SN7493 0.70 AT to be added BCY72 5.17 0A202 0.11 IS2051A 0.20 3N141 0180 SN7494 0.0 THIS MONTH'S BCZII 1.25 OCIO 125 15210A 0.20 40360 0.40 SN7495 030 VALVES - 1.55 255 0.25 BD121 0C20 40361 0.45 SN7496 0.95 TRANSISTORS 121/2% OSCILLOSCOPE TUBES 130124 075 0C23 2.25 0.20 40362 0.40 5N7497 397 2N66996 0.17 BD131 0.40 0025 0.65 40430 0.85 SN74100 1.10 0.12 INTEGRATED TYPE VCR 139A, CV 1 526 BD132 0.45 OC28 0.75 211706 SN740 0116 SN74107 0.45 13E115 0.20 0C35 0.75 2N706Á 0.12 SN,7401 0.16 CIRCUITS 8% AND 13E167 0.20 2111131 0.23 8 pin 15p Price £8.00 P &P 50p add VAT 8% OC36 0.75- SN7402 0.10 DIL BF173 0.25 (SC42 0.50 2NI132 0.25 SN7403 0.10 14 pin 15p METAL CAN BF179 0.30 0C44 0.45 2NI302 030 SN7404 026 SOCKETS BFIO 030 0C45 0.45 2111303 0.40 SN7405 0.22 16 pin 17p TRANSISTORS 8% SPECIAL OFFER Terms of Bossiness: Mon. to Fri. Open for callers 9 a.m. to 5 p.m. Closed Sat Express postage 15p for 1st valve; 2p each additional valve. Express postage: 15p per order for transistors. Prices on application for any type not listed. Obsolete valves a speciality. Prices correct when going to press. This applies to the U.K.

COMPUTER APPRECIATION 86 High Street, Bletchingley, Redhill, Surrey RH1 4PA. Tel: Godstone (088 384) 3221

TELETYPE Model ASR 33 with 20 mA or RS 232 interface, E350. DATEK 40 c. p. s. Paper Tape Readers. Brand new, £28. NEW DATA DYNAMICS ASR 390 with RS 232 interface, £675. FLEXOWRITERS. Models SPD and F available from between £120 and ASR 35 Heavy duty TELETYPE, £350. £150 Model 2300 from £250. ALSO AVAILABLE: KSR 33, KSR 35, KSR 390. EKCO 6 -digit Counter -Timers. With useful variety of I /O. NEW. £48. TELETYPE Model ASR 28, £98. COUTANT 20V Power Suppliers, £15. TELETYPE Model RO 28, £45. HONEYWELL Model P112 Key -to -card punch. £50. OLIVETTI Model FT 300 ASCII terminal with upper /lower case. Under ELECTRONIC ASSOCIATES TRIO Analogue Computer with variety of 600 hours' use, £325. amplifiers, integrators etc.. £98. SAGEM Electronic RO TELEPRINTER. Modern (1969), compact units DATADISK Disc Drive with 3 cartridges. As new OEM version without operating on 5 -level code, £35. electronics, £55. GRI 909 16 bit MINICOMPUTER with 16K memory and some spare PDS 1020 COMPUTER with 4K x 16 memory. Tape Reader/ Punch, cards, £750. £45. PDP 81 with 12K memory, £750. BRPE High Speed Punch, £78. GENERAL AUTOMATION SPC -12 minicomputer with 4K memory. On 2 ELLIOTT 500 c.o.s. Reader, £78. cards without cabinet and P.S.U., £225. ORTHICON Tube, 3 inch, with low useage, £25. DIABLO Series 30 DISC unit. With 12 mega byte capacity. Between 2 and PLEASE NOTI: Prices are exclusive of VAT and carriage - Callers are 3 years old. £495. welcome, but by appointment please. PERTEC 1600 b.p.i., P.E., 9 -track Tape Unit, £475. WW -080 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 107

TRANSFORMERS ALL EX -STOCK - SAME -DAY DESPATCH MAINS ISOLATING VAT 8% 12 and /or 24-VOLT PRI 120/240V SEC I20/240V Separate 12v windings Centre Tapped and Screened Primary 220 -240 Volts Ref Amps £ P &P Ref. VA (Watts) E 12e 07 20 3.57 66 111 05 025 1.77 36 B -Lee 149 60 5.39 80 213 1.0 0.5 2.14 65 150 100 6.13 95 71 2 1 2.77 65 151 200 9.82 1 25 18 4 2 3.42 80 152 250 11.87 1 53 70 6 3 5.09 80

153 350 14.34 1 53 108 8 4 5.85 95 154 500 16.48 1 79 72 10 5 6.33 95 155 750 25.23 OA 116 12 6 6.67 110 156 1000 35.16 OA 17 16 8 8.60 110 157 1500 40.12 OA 115 20 10 12.55 1 73 158 2000 44.76 OA 187 30 15 16.33 1 73 159 3000 70.70 OA 226 60 30 20.32 OA *115 or 240 sec only 30 VOLT RANGE 50 VOLT RANGE Primary 220 -240V Primary 220 -240V SEC TAPS 0-12-15-20-25-30V SEC. TAPS 0- 19- 25- 33- 40 -50V Ref. Amps £ P &P Ref. Amps E P &P 112 0.5 2.27 65 102 0 5 3.12 65 79 1 0 2.90 80 Circuit 103 1 0 4.08 80 3 protection 4.34 80 20 104 2.0 5.69 95 20 3 0 5.41 95 105 3.0 7.02 110 21 4 0 6.39 95 106 4 0 9.18 1 25 51 5 0 7.74 1 10 107 6.0 14.62 1.37 117 60 8.65 1 25 118 15.56 1 80 73 88 8 0 11.73 1 37 and 119 . 10 0 20.41 indicators OA 1 89 100 11.91 53. 60 VOLT RANGE Primary 220-240V AUTO TRANSFORMERS SEC TAPS 0.24.30- 40- 48.60V Ref. VA (Watts) TAPS E P&P Ref. Amps £ P &P 113 20 0 -115- 210 -240L 2.01 124 0 5 2.85 80 59 64 75 0. 1 1 5- 210 -240V 3.51 80 126 1 0 4.23 BO 127 20 6.13 95 4 150 01 1 5. 210 -220 240V 4.98 80 66 300 7.03 95 125 30 9.09 1 10 67 500 10.76 L37 123 4.0 10.57 1 53 84 1000 16.51 1 73 40 50 11.78 1 37 93 1500 21.87 BRS 120 6 0 13.88 1 53 95 121 8 0 18.11 BRS 2000 29.22 BRS 73 122 10 0 22.31 BRS 3000 42.37 BRS 189 1 2 0 23.30 BRS SCREENED MINIATURES Primary 240V HIGH VOLTAGE Ref. mA Volts E P&P- MAINS ISOLATING 238 200 3 -0 -3 1.86 46 Pri 200 220 or 400,440 212 1A,1A 0 -6, 0 -6 2.22 65 Sec: 100 1 20 or 200 240 13 100 9 -0 -9 1.79 .32 VA Ref. E P &P 235 330,330 0 -9, 0 -9 1.89 32

60 243 5.03 1 10 207 500,500 0 -8 -9, 0 -8 -9 2.32 59

350 247 12.57 1 53 208 1A. 1A 0 -8 -9. 0 -8 -9 3.53 65 1000 250 30.26 BRS 236 200.200 0 -15, 0-15 1.79 32 2000 252 50.74 BRS 214 300,300 0-20 0 -20 2.33 65 221 700 (DC) '20-12-0-12-20 2.74 65

DECS SOLDERLESS - 206 1A1A 0- 15 -20, 0.15 -20 4.17 80 BREADBOARDING 203 500 500 0- 15 -27, 0 -15 -27 3.62 80 S Dec 70 contacts £1.98 204 1A IA 0- 15.27, 0.15 -27 4.76 80 T Dec 208 contacts £3.38 5112 500 0-12-15.20-24-30 2.27 65. U Dec A IC s etc £3.99 CASED AUTO. TRANSFORMERS U Dec B IC s etc £6.99 240V cable input USA 2 -pm outlets VAT 6'. P &P .'fid 20VA £3.78. P &P 80p Ref 113W 75VA £5.51. P &P 95p Ref 64W BRIDGE RECTIFIERS 150VA £7.33. P &P 95p Ref 4W .0 r, 2A 45p 300VA £10.81. P &P E1 15 Ref 66W 40Ov 20 55p 500VA £12.62. P &P E 1 37 Ref 67W 200v 4A 65p 750VA £16.80. P &P E1 53 Ref 83W 4000 4A 80p 1000VA £21.15. OA Ref 84W 400v LA E1.00 2000VA £33.02. OA Ref 95W 500, iUA £2.35 P&P rSl, vAT HIGH QUALITY MODULES VAT 1 VAT y watt RMS Amplifier E2.95 10 watt RMS Amplifier E3.25 25 watt RMS Amplifier E4.35 METERS Pre Amp for 3 -5- 10w £6.70 A total range of fuseholders, circuit AVO8 E61.09 Pre-Amp for 25 £13.75 AV071 £25.10 Power Supplies for 3 5 1 Uw E1.30 breakers and indicator lamps by the leaders AVOMMS E20.94 Power Supplies lie 25, E3.75 WEE MEGGER £51.05 T ransfoiin..1 for 5 '0w £ 2.30 in circuit protection technology. AVO TT169 £26.00 Transformer for 25, one modutei £2.90 04315 £ 13.00 Types P &P Amps Pm Amps Power Supplies 18p designed to comply with Includes steel carry case P &P Transformer, 58p In-circurts transistor tester European safety requirements and European Avo Cases and Accessories STEREO 30 Complete r , P &P E1 25. VAT 8" ,.-. mfrs pre low voltage directive. amp power ,,,hilly from panel kept, ineertk mains trans r E16.25. Maras vans £2.45 Teak Fuseholders TI MINI- MULTIMETER veneered cab £3.65. P &P 88p VAT 1 2' DC -1000V AC-1000V AC , DC. Panel mounting Printed -circuit board 1000 ' V POWER UNITS DC -100mA Res - 150K CC12 -05. 14 5 7 it 9 12s 500mA £4.08 Bargarn STABILISED Sealed and unsealed In -line at £5.30 3 6 7 5 9v at 400mA E5.95 VAT 8% P &P 45o 3300. r. , 9v at 300mA plugs deer nto 134 Circuit breakers socket E2.85 STEREO F.M. :LINER Thermal *Thermal magnetic 4 Pre -selected sl rims ANTES SOLDERING IRONS Switched AFC Indicators Supply 20 350 90Ma Man r E4.93 £20.45. P &P 25p VAT 1 2'v Stand for above E1.45. P Neon Filament lamp &P 32p VAT EC MAGNETIC TO CERAMIC PLEASE al .'AT Ar TER P &P Post Office and military approved types. CARTRIDGE CONVERTER ELECTROSIL AND SEMICONDUCTOR Operating Voltage 20 45v STOCKISTS AUDIO ACCESSORIES & BARGAIN PAKS CALLERS MON i Circle 108 for further information. ONLY £2.85 P &P -Bp WELCOME ,FRI OR VAT '-', SEND STAMP FOR LISTS PRICES CORRECT AT 9 2 T r Belling -Lee - Barrie Electronics Ltd. Belling a Lee Limited, Great Cambridge 3,THE MINORIES,LONDON EC 3N 1BJ Road, Enfield, Middlesex. TELEPHONE: KWPS/BL174 Telephone: 01 -363 5393 Telex: 263265 01 -488 3316/8 NEAREST TUBE STATIONS: ALDGATE & LIVERPOOL ST.

1VU"-075 FOR Fl R I FIER DF I-AILS

www.americanradiohistory.com Wireless World, April 1977 Zambia Gibraltar Chile Spain United Arab Emirates Singapore New Guinea Israel

=a POWERTRAN INCORPORATING hpluitNTAcOUSIILa

IELECTRONICS u- HI -FI NEWS 75W /CHANNEL AMPLIFIER

In Hi -Fi News there was published by Mr. Linsley -Hood a series of four. articles (November, 1 9 72-February, 1 9 73) and a subsequent follow -up article (April, 1974) on a design for an amplifier of exceptional performance which has as its principal feature an ability to supply from a direct coupled fully protected output stage, power in excess of 75 watts whilst maintaining distortion at less than 0.01% even at very low power levels- The power amplifier is complemented by a pre -amplifier ../,,..Gy based on a S discrete component operational amplifier referred to as the Liniac which is employed in the two most critical points of the system. namely the equalization stage and tone control stage. positions where most conventional designs run out of gain at the extremes of the frequency spectrum. Unusual features of the design are the variable transition frequencies of the tone controls and the variable slope of the scratch filter. There is a choice of four inputs, two equalized and two linear. By J. L. Linsley Hood each having independently adjustable signal level. The attractive sfimline unit pictured has been made practical by highly compact PCBs and a specially designed Pock Price Pea Priem Toroidal transformer. I. Fibreglass Flirted-circuit board for power amp £1.15 11. Fibreglass printed -circuit board for power supply 2. Sel of resistors. capacitors. pre-sets or power amp £0.85 £2.15 12. Set of resistors. capacitors. secondary fuses. power 3. Sul of semiconductors for amp E6.50 semiconductors for power supply £4.60 FREETEAK CASE WITH FULL KITS 4. Pair of 2 drilled. finned heal sinks £1.10 13. Set of miscellaneous parts including DIN skis. mains 5. Rbrepfau printed- circuit board for preamp £1.75 input skt. fuse holder. interconnecting cable. control 6 Set of low noise resistors. capacitors. pre -sets for knobs £5.35 pre -amp £3.40 14. Sel of metalwork parts including silk screen printed 7. Set of low noise. high gain semiconductors for fascia panel and all brackets. fixing pans. etc. £7.30 KIT PRICE ONLY pre-amp £2.40 15. Handbook £0.30 £73.90 8. Sel of potentiometers (Including mains switch) E3.15 16. reek cabinet 18.3" x 12.1" x 3.1" E9.85 9. Set of 4 push -button switches. rotary mode switch 2 each of packs 1.7 inclusive are required for complete 10. Toroidal transformer complete with magnetic stereo system. Total cost of individually purchased wen /bousingairinlary: 0 117 -234 V: secondaries: packs £83.75 WIRELESS WORLD FM TUNER 33433.V.- í5425V £10.95

Designed in response to demand for a tuner to complement the world -wide acclaimed Linsley Hood 75W Amplifier. this kit provides the perfect match. The Wireless World (Skingley and Thompson - April. May 1974) published original circuit has been 'developed further for inclusion into this outstanding slimline unit and features a pre -aligned front end module, excellent a.m. rejection and temperature compensated varicap tuning. which may be controlled either continuously or by push button pre -selection. Frequencies are indicated by a frequency meter and sliding LED indicators, attached to each channel selector pre -set. The PLL stereo decoder incorporates active filters for "birdy' suppression and power is supplied via a toroidal transformer and integrated regulator. For long term stability metal oxide resistors are used throughout. Ptak Price Pack Price I. lnlje a pistol bed ter trod mid á strip. I. toroidal transformer with electrostatic screen. IbmMdeter. AFC NO mob dreuita £2.15 Primary: 0-117V-234V E4.45 FREE TEAK CASE WITH FULL KITS 2. tot M metal ende resMen, thermister, capacitors. 12. Set of capacitors. rectifiers. voltage regulator for

core preset for mounting en pack 1 £4.30 power supply E2.95 3. set el transistors. diode:. LED. integrated circuits ter 13. Sel of miscellaneous parts. including sockets. fuse

Minting et pack 1 £5.25 holder. fuses. interconnecting wire. etc. E1.50 4. PE.Wgeed from end module, cell euemhly. three 14. metal KIT PRICE only Sel of work parts including silk screen printed 7 5 section ceramic filter 6 £8.50 lacia panel. acrylic printed £6 silk screen tuning 5. Rbreglau printed circuit beard for stereo decoder indicator panel insert. internal screen. fixing parts. £1.10 etc. ' £7.50 6. Set of metal oxide resistors. capacitors Carmel Ia. Construction notes (free with complete kill £0.25 pruet for decoder E2.60 16. Teak cabinet 18.3" a 12.7" x 3.1" E9.85 NEW KIT! 7. Set of tranaistora LED. integrated circuit for decoder £2.90 One each of packs 1.16 inclusive are required for complete B. Set of components for channel reflector switch stereo FM tuner. Total cost of individually purchased LINSLEY -HOOD CASSETTE DECK module including fibreglass printed circuit board. packs £76.85 gush -button switches. knobs. LEDs. 'preset adjuster: etc. £8.80 9. Function switch. IO turn tuning potentiometer. knobs £5.30 10. Frequency meter. meter drive components. fibreglass printed circuit board E9.45

Published in Wireless World (May, June, August 1 976) by Mr. Linsley-Hood, this design, although straightforward and relatively low cost nevertheless provides a very high standard of performance. To permit circuit optimization separate record and replay amplifiers are used, the latter using a discrete component front -end designed such that the noise level is below that of the tape background. Push button switches are used to provide a choice of Pack Price Pack Price equalization time constants, a choice of bias levels and also an option of using I. Stereo PER (accommodates 2 rep. amps. 2 rec. Ill. Sel of capacitors. rankers. I.G. voltage regulator an additional preamplifier for microphone use. The mechanism used is the amps. 2 meter amps. bias /erase osc. relayjE3.35 for power supply IPowertraa design) ... E2.80 Goldring -Lenco CRV, a unit distinguished in its robustness and ease of 2. Sterne sel of capitors. M.O. resistors. operation. Speed control and automatic cassette ejection are both 11. Set of miscellaneous pats. including sockets. fuse potentiometers for above £9.80 holder. lases. interconnecting wire. etc_ E2.50 implemented by electronic circuitry. This unit which is powered by a toroidal 3. Stereo set of semiconductors for above E8.90 12. of including facia transformer and uses metal oxide resistors throughout offers an excellent Set metalwork silk screened 4. Miniature relay with match for the Wireless World Tuner and the Linsley -Hood 75 Watt Amplifier. socket E2.45 panel. infernal screen. fixing parts. etc.. E7.10 5. PCB. all components for solenoid. speed control 13. Construction notes £0.25 PRICE STABILITY circuits E3.20 14. Teak cabinet 18.3" x 12.1" x 3.1" (9.85 6. Goldring Lenco mechanism as specified. E21.95 One each of packs 1 -14 inclusive are Order with confidence! Irrespective of any price changes we will honour all 7. Function switch. knobs £1.60 required for compete stereo cassette prices in this advertisement for two months from issue date provided that this 8. Dual VU meter with illuminating lamp £7.20 deck. Total cost of individually pur - advertisement is quoted with your order. E &OE VAT rate changes excluded. 9. Toroidal transformer with E.S. screen prim. chased picks £85.40 All components are brand new first grade full specification devices. All resistors 0-117Y. 234V. Sec. 15V E4.45 (except where stated) are low noise carbon film types. All printed circuit boards are fibre -glass, drilled, roller tinned and supplied with circuit diagrams and SPECIAL PRICE FOR construction layouts. COMPLETE KITS £81.35 FREE CATALOGUE U.K. customers just send name and address - Overseas customers. please send 5 International Reply Coupons and you will receive your catalogue by return Further details of above given in our FREE CATALOGUE AIRMAIL. PLEASE NOTE ALL PRICES VAT EXCLUSIVE - DEPT. WW4 EXPORT ORDERS. No VAT charged. Postage charged at actual cost plus 50p documentation and handling. Please make payn ant by Bank Draft, Postal Order. International Money Order in sterling.

SECURICOR DELIVERY -. For this optional service (U.K. Mainland only) add POWERTRAN ELECTRONICS ti2.50 (VAT INC.) per kit. U.K. ORDERS: Subject to 121/2Zv% yr surchargeh foror Carriagearriaga PORTWAY INDUSTRIAL ESTATE MAIL ORDER ONLY (for at current rate if changed) ANDOVER, HANTS SP10 3NN /ndonesia Brazil Switzerland Canada Saudi Arabia New Zealand Norway Iceland Sweden

www.americanradiohistory.com Wireless World, April 1977 109 Guernsey Cyprus Belgium Uganda Brunei Trinidad South West Africa Italy Java AUDIO KIT SUPPLIERS TO THE WORLD

T20 + 20 and our new T30+30 20W, 30W AMPLIFIERS

Designed by Texas engineers and described in Practical Wireless the Texan was an immediate success. Now developed further in our laboratories to include a Toroidal transformer and additional) improvements the slirnline 720 + 20 delivers 20W per channel of true Hi-Fi at exceptionally low cost The design is baser, on a single F /Glass PCB and features all the normal facilities found on quality I amplifiers, including scratch and rumble filters. adaptable input selector and held phones socket. In al follow up article in Practical Wireless further modifications were suggested and these have been. incorporated into the T30 + 30 These include OF interference filters and a tape monitor facility Power output of this new model is 30W per channel

Pack T20 T30 Pack 720 T30 SPECIAL PRICES 1. Sm of low noise resistors I.40 1.50 8. Toroidal transformer - 240V prim. 2. Set of small capacitors 2.20 2.80 Lt. screen 4 95 6.80 2.30 9. Alveglass PCB 3 20 3.60 FOR COMPLETE KITS! 3. Set of power supply capacitors 1.90 4. Set of miscellaneous pans 3.20 3.20 10. Set of metalwork. fixing parts 4.20 4.80 5 Sal of slide. mains. P.B. swfckss .. 1.20 1.20 Il. Set of cables. mains lead 0 40 0.40 T20 +20 8. Sel of pots. selector switch 2.80 2.80 12. Handbook [free with complete kill 0 25 0.25 7.75 7. Set of semiconductors. ICs, 'kb 7.25 13 Teak cabinet 15.4" a6.7" a 2.8" 4.50 4.50. KIT PRICE only £31.10 T30 +30 2 NEW TUNERS! KIT PRICE only £35.90 WW SFMT II Following the success of our Wireless World FM Tuner kit we are now pleased to introduce our new cost reduced model, designed to complement the 720 and T30 amplifiers. The frequency meter of rh, KIT PRICE more advanced model has beer, omitted and the mechanics simplified however the circuitry is identical and this new kit offers most exceptional value for money Facilities included are switchable aft. adjustable, switchable muting. channel selection by slider or readily adjustable pre -set push -button controls and LED tuning indication. Individual pack prices in £45.50 our free list.

POWERTRAN SFMT

This easy to construct tuner using our own circuit design includes a KIT PRICE pre-aligned front end module. PLL stereo decoder. adjustable. switchable muting, switchable afc and push-button channel selection As with all our, full kits. all components down to the last nut and holt are supplied together with full constructional details. £32.60 CONVERT NOW TO QUADRAPHONICS!

With 100s of titles now available no longer is there any problem over suitable software Nq problems with hardware either Our new unit the SQM 1 -30 simply plugs into the tape monitor socket. of your existing amplifier and drives two additional speakers at 30W per channel A full complement of controls including :volume, bass, treble and balance are provided as are comprehensive switching facilities enabling the unit to be used for either front or rear channels. by- passing the decoder for Special offer to T20 + 20 and Tear) stereo-only use and exchanging left and right channels. The SO owners! Owners of 120 o 20 and Texan amplifiers. matrix decoder is based upon a single integrated circuit and was which have no tape monitor outlet. SQM1 30 'designed by CBS whilst the power and tone control sections are 1 be - KIT PRICE £37.115 purchasing an SOM -30 will supplied identical to those used in our T30 + 30 amplifier which the on request. free conversion kit to fit a tape Moslem World Amplifier Designs. Full kits are not available for these projects but SQM1 -30 matches perfectly. Kit price includes CBS licence fee monrroerig facdrty to the existing amplifier. component packs and PCBs are stocked for the highly regarded Bailey and 20W class AB The makes simple the connection to the highly 1 -30 Linsley Hood designs, together with an efficient regulated power supply of our own adaptable SOM quadrophonic design Suitable for dying these amplifiers is the Bailey Burrows pre- empt/lief and Our decoder /rear channel amplifier. rcuit board, for the stereo version of n features 6 inputs. scratch and rumble filters and onde range tone controls which may be either rotary or slider operating For those intending to get the best out of their speakers. we also offer an avoue filter system. described by D. C. Read. which splits the output of each channel from the pre -amplifier into three channels each of which is fed to the appropriate speaker by its own power SQ QUADRAPHONIC DECODERS amplifier The Read /Texas 20W. or any of our other kits are suitable for these For tape Feed systems a set of three PCBs have been prepared for the integrated circuit based high 2 channels (200- 1000mV as obtainable from most pre -amplifiers or amplifier performance stereo Stuart design. Details of component packs are in our free list tape monitor outlets( into any one of our 3 decoders and take 4 channels out with no overall signal level reduction 30W Batley Amplifier On the logic enhanced decoders Volume. Front -Back. LF -RF balance. Lb -H8 balance and Dimension controls can all be implemented BAIL Pk 1 F /Glass PCB E1.00 by simple single gang potentiometers. BAIL Pk 2 Resistors. Capacitors. Potentiometer set E2.35 These state -of- the -art circuits used under licence from CBS are offered in kits of superior quality with close tolerance BAIL Pk. 3 Semiconductor set E4.70 capacitors. metal oxide resistors and fibre -glass PCBs designed for edge connector insertion. All kit prices include 20W Lmaley Hood Class AB CBS licence fee LHAB Pk. 1 F /Glass PCB £1.05 M1 Basic matrix decoder with fixed 10 -40 blend All components. PCB LHAB Pk 2 Resistor. Capacitor. Potentiometer set £3.20 £5.90 L1 Full logic LHAB Pk. 3 Semiconductor set ... £3.35 controlled decoder with "wave matching and 'front back logic'. for enhanced channel separation. All Regulator Power Sypply components PCB E17.20 60VS Pb 1 F /Glass PCB £0.85 L2A. More advanced full logic decoder with "variable blend" for increased front back separation. All components. Pb 2 Resistor. 60VS Capacitor set'. E2.20 PCB 60vá Pk. 3 Semiconductor set E3.10 £22.80 60VS Pk. 6A Toroidal transformer (for use with Bailey) £8.60 L3A. Decoder similar to L2A but with discreet component front end with high precision 6 -pole phase shift networks for boV5 Pk. 6B Toroidal transformer (for use with 20W LH) £7.25 increased frequency response. All components (carbon film resistors). PCB E25.90 Bailey Burrows Stereo Pre -Amp Also available with M.O. resistors, cermet pre -set - add £4.20 BBPA Pk I F /Glans PCB £2.80 BBPA Pk. 2 Resistor, capacitor semiconductor set E6.70 SEMICONDUCTORS as used in our range of quality audio equipment. BBPA Pk 3R Rotary Potentiometer set . - £2.85 BBPA Pk 35 Slider Potentiometer set with knobs £3.10 2N699 0t1.20 40361 00.40 BD530 £0.58 MJE521 E0.60 4ksctive Filter - TIP29C £0.55 E0.20 40362 80056 £1.50 FILT Pk..1 Fd Glass PCB E1.40 2N1613 £0.45 MESAU] 00.25 TIP30C E0.60 8C107 BF257 £0.40 FIIT Pk. 2 Resistor. Capacitor set (metal oxide 2 %. polystyrene 21/2%) £4.20 2N2926G £0.10 £0.10 MPSA12 £0.35 TiP41 A £0.70 BC108 £0.10 BF 259 £0.47 FILT Pk 3 Semiconductor set . £2.25 253055 E0.45 MPSA14 £0.30 TIP42A £0.80 BC109 BFR39 E0.30 2 off Pks 1. 2. 3 rqd for stereo arrive filter system 253442 E1.20 £0.10 MPSA55 £0.25 TIP41B £0.75 BFR79 £0.30 2N3711 £0.09 BC109C £0.12 MPSA65 £0.35 TIP42B £0.50 Read /Texas 20W Amp BC125 £0.20 253904 £0.17 £0.15 BFY51 MPSA66 £0.40 1N914 £0.07 READ Pk. 1 F /Glass PCB E1.00 BEY 52 2 N3906 £0.20 BC126 £0.15 £0.20 MPSUO5 £0.50 15916 £0.07 READ Pk. 2 Resistor. Capacitor set £ 1.20 254062 £0.11 BC182 £0.10 CA3046 £0.70 15920 E0.10 READ Pk. 3 Semiconductor set E2.30 SBA750A E1.90 254302 £0.60 BC212 £0.12 LP1186 E8.50 51301 6 off pks 1. 2. 3 required for stereo active filler system E2.30 £1.30 2N5087 £0.25 6CI82L £0.10 MC1310 E2.20 SL3045 E1.20 FILTERS I- Stuart Tape Recorder 255210 E0.25 BC 184L £0.11 MC1351 £1.05 SN72741P £0.40 FM4 E1.00 C TRRP Pk 1 Replay Amp F /Glass PCB E1.30 255457 £0.45 BC212L £0.12 MC1741CG E0.95 SN 72748P £0.40 5F.410 /MA E1.50 X TRRC Pk 1 Record Amp F /Glass PCB E1.70 2N5459 £0.45 BC214L £0.14 MFC4U1U £0.95 TI1209 £0.20 TROS Pk 1 Bias /Erase /Stalflizer F /Glass PCB .. £1.20 255461 £0.50 BCY72 £0.13 MJ481 t1.20 TIP29A £0.40 LD Further details of above and additional packs given in our FREE LIST 265830 E0.35 80529 £0.55 MJ491 E1.45 TIP30A £0.46 3 Our Export Department will be pleased to advise on postal costs to any country in o- EXPORT NO PROBLEM the world. Some of the countries to which we sent kits in 1976 are shown o surrounding this advertisement. Tunisia Germany Nauru Hong Kong Australia Eire Gambia Denmark France Muscat & Oman

www.americanradiohistory.com 110 Wireless World, April 1977 RETURN OF POST MAIL ORDER SERVICE

BSR HI -FI AUTOCHANGER ELAC FI BAKER MAJOR 12" £14.95 STEREO AND MONO £11.95 Post 75p SPEAKERI ,t Post F1.00 Plays 12 ", 10" or 7" records. Auto or £3.45 A 30- 14,500 c's, 12in. double cone. ._ TYPE Post cone together Manual. A high quality unit backed by - - 59RM 35p ` woofer and tweeter This famous unn now magnet BSR reliability with 12 months , 7' available, 10 watts, 8 ohm. with 'a BAKER ceramic guarantee. A..0 200/250V. / x. assembly having a flux density of Size 13' -11%in. 3 speeds. ; R.C.S. LOW VOLTAGE STABILISED 14.000 gauss and a total flux of Above motor boar 3%in, POWER PACK KITS 145.000 Maxwells. Bass resonance 40 c /s. Rated 25W. NOTE: 4 or 8 or Below motor boar 21/2in. vl;l. r . All parts and instructions with Zener diode, must stated. with STEREO and MONO CARTRIDGE pinted circuit rectifiers and double wound mains £2.95 16 ohms be above with stereo Post 45p B.S.R. SINGLE PLAYER similar to transformer. Input 200/240V a.c. Output Module kit, 30-17.000 c/s with cartridge and cueing device. large turntable £13.50 voltages available, 6 or 7.5 or 9 or 12V d.c. up to 100mA or tweeter, crossover, 1 B.S.R. P128 with magnetic cartridge. Balanced arm cueing E $55. less. Size 3 x 21/2 x 1 %tin. Please state voltage required. baffle L .7J device £23.50. R.C.S. POWER PACK KIT and instructions. Post E1.60p each PORTABLE PLAYER CABINET Please state 3 or 8 or 15 ohms. modern design. Rexene covered. 12 VOLT, 750mA. Complete with printed £3.35 BAKER "BIG- SOUND" SPEAKERS. Post each Vynair front grille. Chrome fittings circuit board and assembly instructions. Post 30p E1.00 12 VOLT KIT, VOLT 1 AMP KIT, Size 17 x 15 x 8in. approx. £4.50 Post 75p 3 OmA £3.15. 9 £3.35. 'Group 25' 'Group 35' 'Group 50/15' -'Motor board cut for BSR or Garrard deck R.C.S. GENERAL PURPOSE TRANSISTOR 12ín 12in. 15in. PRE- AMPLIFIER - BRITISH MADE 30W £11.95 4ow £13.95 75W £24.95 HEAVY METAL PLINTHS Ideal for Mike, Tape, P.U., Guitar, etc Can be used with battery 4 or8or 16 ohm 4or8or 16 ohm 8or16 ohm With P.V.C. Cover. Cut out for most B.S.R. £6.50 9 -12V or H.T. line 200 -300V d.c. operation. Size 13/4 o or Garrard decks. Silver grey finish. Post El 50 in. Response 25 c/s to 25 kc /s. 26 dB gain. BAKER LOUDSPEAKER, 12 INCH. 60 WATT. Model "A" Size 121/2 x 143/4 x 71/2in. For use with valve or transistor equipment. £1.45 GROUP 50/12, 8 OR 15 OHM HIGH POWER. Model x x "B" Size 16 133/4 7in. £7.50. Full instructions supplied. Details S.A.E. Post 30p FULL RANGE AL QUALITY. Extra large plinth & cover. teak wood base. RESPONSE 3016,0001CPS £20.95 Size 20" x 17'/7" X 9" £19.50. Callers only. ELECTRO MAGNETIC MASSIVE CERAMIC MAGNET WITH Post £1.60 .7 PENDULUM MECHANISM ALUMINIUM PRESENCE CENTRE DOME. COMPLETE STEREO SYSTEM 1.5V d.c. operation over 300 hours continuous on SP2. battery, fully adjustable swing and speed. Ideal displays, Two full size loudspeakers 133/4 x 10 x 3'i in. Player unit TEAK VENEERED HI -FI SPEAKERS AND CABINETS clips to loudspeakers making it teaching electro magnetism or for Post extremely compact, overall For 12in or 10in. speaker 20x13x12in. £14.50 Post E2 size only 133/4 z 10 x 81/2in.. 3 watts per plays metronome, strobe, etc 9513 30p channel, all For 13x8in. or 8in. speaker £7.50 Post E1 records 33 r.p.m.. 45 r.p.m. Separate volume and tone ALL For 8x5in speaker t 2x8x6in, £5.80 Post 75p controls Attractive Teak finish MAINS TRANSFORMERS Tip 240V a.c. mains £22.50 250- 0 -250V 70mA, 6.5v 2A £3.45 FEW R.C.S. 100 watt ONLY El carnage 250 -0 -250 80mA, 6.3V 3.5A, 6.3V 1A or 5V 2A £4.60 350-0-350 80mA, 6.3V 3.5A, 6.3V 1A or 5V 2A £5.80 VALVE 300- 0-300V 120mA, 6.3V 4A C.T.: 6.3V 2A £7.00 AMPLIFIER FEW ONLY MIDGET 220V 45mA, 6.3V 2A £1.75 HEATED TRANS. 6.3V 'h amp £1; 3 amp E1.40 CHASSIS GENERAL PURPOSE LOW VOLTAGE. Tapped outputs at 2 Four inputs. Four way mixing, master volume, treble bass amp. 3, 4, 5, 6. 8, 9, 10, 12, 15, 18, 25 and 30V £4.60. and controls. Suits all speakers. This professional quality t amp. 6, 8, 10. 12, 16, 18, 20, 24. 30, 36. 40. 48, 60 amplifier chassis is suitable for all groups, disco. P.A., where high quality £4.60. 2 amp, 6, 8, 10, 12. 16, 18, 20, 24, 30. 36, 40, power is required. 5 speaker outputs. A/C mains operated. 48, 60 £7. 3 amp. 6, 8, 10, 12, 16, 18, 20, 24. 30. 36, Slave output socket. Produced by demand for a quality valve 40, 48, 60 £8.70. 5 amp. 6, 8, 10. 12, 16, 18. 20, 24, amplifier. 100V line output to order. Send for leaflet. SPECIAL OFFER! 30, 36, 40, 48, 60 £11.25. 6.06V 500mA £1, 9V 1 amp. Suitable carrying SMITH'S CLOCKWORK 15 AMP £1. 12V 300mA, £1, 12V 500mA, £1, 12V 750mA, £1, cab £14. Price £85 carr, E2.50 TIME SWITCH 10V, 30V, 40V, 2 amp £2.75, 20V. 3 amp.. £2.45, 40V. SPEAKER COVERING MATERIALS. Samples Large S.A.E. 0 -60 MINUTES £2.95 Posi 35p 2 amp.. £2.95, 30V 5A and 34V 2ACT £3.45, 16V, 2 LOUDSPEAKER CABINET WADDING 18in. wide 20p ft. Single pole two -way. Surface mounting amp., E2.20, 0, 5, 8, 10. 16V. '/z amp., E1.95, 20V '/: Horn Tweeters 2- 16kc /s, 10W 8 ohm or 15 ohm £3.60 amp.. £1.75, 20V, 1 amp., £2.20, 20V 3 amp., £2.50, De Luxe Horn Tweeters 3- 18kc /s, 30W, 8 ohm, £7.50. with fixing screws. Will replace existing ' wall switch to give light for return home, 20 -0 -20V 1 amp., £2.95, 30V 11/2 amp., £2.75; 20V, CROSSOVERS. TWO -WAY 3000 c/s 3 or 8 or 15 ohm garage, automatic anti -burglar lights. etc. 40V. 60V or 20- 0 -20V, 1 amp. £3.50. £1.90. 3 -way 950 cps /3000 cps, £2.20. Variable knob. Turn on or off at full or AUTO TRANSFORMERS. 115V to 230V or 230V to 115V LOUDSPEAKERS P.M. 3 OHM 7x4in. £1.50; 61/2in., £1.80; intermediate settings. Brand new and 150W £5; 250W £6; 400W £7; 500W £8. 8x5m., £1.90; Bin., £1.95. fully guaranteed. FULL WAVE BRIDGE CHARGER RECTIFIERS: SPECIAL OFFER: 80 ohm. 23/4in., 23/4in 35 ohm, 31n., 25 0.6 Hour version -£3.30 6 or 12V outputs, 11/2 amp 40p; 2 amp 55p; 4 amp 85p. ohm, 21/2in., 3in., 5x3in., 7x4in., 8 ohm. 21/2in., 3in., 31/2in., CHARGER TRANSFORMERS: 11/2 amp £2.75; 4 amp. E4.60. 5in., 15 ohm, 31/2in. dia, 6x4in., 7x4in., 5x3in., TEAKWOOD- LOUDSPEAKER GRILLES will easily fit to 4112V. 1 VeA HALF WAVE Selenium Rectifier. 25p. 3 ohm., 21/2in., 2 %in.. 3 1/2in., 5in. dia. £1.25 each. baffle board. Size 101/2 e 7V in -45p. PHILIPS LOUDSPEAKER, 8in.. 4 ohms, 4 watts, £1.95 R.C.S. RICHARD ALLAN TWIN CONE LOUDSPEAKERS R.C.S. "MINOR" 10 watt AMPLIFIER KIT BOOKSHELF 8in. diameter 4W E2.50. 10in diameter 5W £2.95; This kit is suitable for record players, guitars. tape playback, 12in. diameter 6W £3.50. 3/8/ 15 ohms, please state. electronic instruments or small P.A. systems. Two versions SPEAKERS PIEZO ELECTRIC HORN TWEETER. Handles up. to 100 watts. No crossover required. £10.95. available Mono, £11.25; Stereo. £18. Post 45p. Specification Size 141/2in. x 93/4in. z Stn. 10W per channel: input 100mV; size 9V, o 3 x tin. approx. 50 to 14.000 cps Tweeter Volume Control 15 ohms 10W with one inch long S A E details. Full instructions supplied. AC mains powered. 8 watts rms 8 or 4 ohms threaded bush for wood panel mounting. 'hen. spindle. 65p. VOLUME 80 Ohm Coax 8p yd. £16 pair Post El. 30 BAKER 150 WATT STANDARD TYPE VHF PROFESSIONAL CONTROLS FRINGE LOW LOSS 15p yd. KUBA- KOPENHA EN MIXER AMPLIFIER 5kO to 2M4. LOG or LIN. Ideal 625 and colour PLUGS All purpose transistorised G C O Ç7.. L/S 35p. D P bop. STEREO STEREO 10p. SOCKETS 10p. LINE Ideal for Groups. Disco L/S 85p. D P £1. Edge 5K. SOCKETS 18p. OUTLET and P.A. 4 inputs speech and music. 4 way mixing. S.P Transistor 30p. BOXES 50p. TUNER -AMPLIFIER CHASIS AM -FM 54:5 Output 4 8/15 ohms. a.c. Mains. Separate treble and This Continental 4 -band radiogram chassis uses first class quality bass controls. Master volume control. ELAC HI -FI SPEAKER components throughout. Features: Large facia panel with 7 push Guaranteed. Details S.A.E. £60 E1 50 carr. buttons for medium, long, short, VHF -FM, AFC, phono, mains NEW MODEL MAJOR -50 watt, 4 input. 8in. TWIN CONE on-off. 4- rotary controls. tuning, volume, tone. balance. Facia 2 vol T.eble and bacs taos .4,gx...,,.,..hr.- £49 Can r1 Dual cone plasticised roll surround. Large size 17 x 4'/ inches. Chassis size 17 x 41/2 x 51/2 inches ceramic magnet. 50- 16,000 c /s, Bass DIN-connector sockets for tape record /playback, loudspeakers, 100 WATT DISCO AMPLIFIER CHASSIS resonance 55 c /s. 8 ohm impedance, 10 phono pick -up, external FM -AM aerials. Automatic stereo volume, treble. bass controls. 500 M V. or 1 volt input. watts. music power. , Four loudspeaker 4 All £3.95 post 35p beacon light. Built -in ferrite rod aerial for medium longwave. outputs to 16 ohm transistor £52 A.C. 240V mains. Circuit supplied /^ BARGAIN 4 CHANNEL TRANSISTOR MONO MIXER bave speakers are suitable 5Sy Post C1 Fn 13'/2 x £33. Add musical highlights and sound effects to recordings. E.M.I. 8in. SPEAKER SALE! LOW VOLTAGE ELECTROLYTICS Will mix Microphone. records. tape and tuner 1. 2. 4, 5, 8. 16, 25, 30 50, 100, 200mF 15V 10p. With tweeter and Ditto with separate controls into single output. 9V. £5.95 crossover, 10 watt. 500mF 12V 15p; 25V 20p; 50V 30p. 15 watts, 1000mF 12V 17p; 25V 35p; 50V 47p; 100V 70p. TWO STEREO CHANNEL VERSION State 3 or 8 ohm. 8 or 15 ohm £7.50 As illustrated. 2000mF 6V 25p; 25V 42p; 50V 57p. BARGAIN 3 WATT AMPLIFIER. 4 Transistor£3.95 2500mF 50V 62p; 3000mF 25V 47p; 50V 65p. Push -Pull Ready Built, with volume. Treble £8.50 3900mF 100V £1.60. and bass controls. 18 volt d c. Mains Power Pack £3.45 £5.95 Post 65p 4700mF 63V £1.20. Post 45p 5000mF 6V 25p; 12V 42p; 25V 75p; 35V 85p. With tweeter and cross- SHORT WAVE 100pF air spaced gangable tuner. 95p. ALUMINIUM HEAT SINKS. Finned type Sizes 610" x 41/2" over. 20 watt. TRIMMERS 10pF, 30pF, 50pF, 5p. 100pF, 150pF. 15p. X 23/4" 95p. 61/2" x 2" x 21/2" 65p Bass res. 25 c.o.s. £9.50 CERAMIC, 1pF to 0.01mF, 5p. Silver Mica 2 to 5000pF, 5p. BALANCED TWIN RIBBON FEEDER 300 ohms. Sp yd. Flux =11,000 gauss. Post 75p PAPER 350V -0.1 7p; 0.5 13p; lmF 150V 15p; 2mF 150V JACK SOCKET Std. open-circuit 2Op, closed circuit 25p; 8 or 15 ohm. 20 to 20,000 c.o.s. 15p; 500V -0.001 to 0.05 5p; 0.1 10p; 0.25 13p; 0.47 25p. Chrome Lead -Socket 45p. Mono or Stereo. MICRO SWITCH SINGLE POLE CHANGEOVER 20p. Phono Plugs Sp. Phono Socket 8p. Bookshelf Cabinet £7.50 SUB -MIN MICRO SWITCH, 25p. Single pole change over JACK PLUGS Std. Chrome 30p; Plastic 25p; 3.5mm 15p. Teak finish. For EMI 13 x 8 speakers. Post E1 00 TWIN GANG, 385 + 385pF 50p; 5000 standard 75p; 365 STEREO JACK PLUG 30p. SOCKET 25p. + 365 + 25 + 25pF. Slow motion drive 65p. DIN SOCKETS Chassis 3 -pin 10p. 5 -pin 10p. THE "INSTANT'- BULK TAPE ERASER DIN SOCKETS FREE 3 -pin 25p; 5 -pin 25p. DIN 1 20pF TWIN GANG, 50p; 365pF TWIN GANG, 50p. PLUGS AND HEAD DEMAGNETISER. Suitable for NEON PANEL INDICATORS 250V. Amber or red 30p. 3-pin 25p; 5 -pin 25p. VALVE HOLDERS, 10p; CANS 10p. cassettes. and all sizes of tape reels. A C. RESISTORS. V.W. 1/2W. 1W, 20% 2p; 2W, 10p; 100 to 10M. Leaflet S.A.E. mains 200/250V. HIGH STABILITY. '/W 2% 10 ohms to 6 meg . 12p. Will also demagnetise small £4.50 Ditto 5 %. Preferred values 10 ohms to 10 meg., 5p. R.C.S. SOUND TO LIGHT KIT tools. Post 50p WIRE -WOUND RESISTORS 5 watt, 10 watt, 15 watt, Kit of parts to build a 3 channel sound to light unit. 10 ohms to 100K 12p each 1,000 watts per channel. £14. Post 35p. BLANK ALUMINIUM CHASSIS. 6 x 4 -70p; 8 x 6 -90p; TAG STRIP 28 -way 12p. Easy to build. Full instructions supplied. Cabinet £3. 10 x 7- E1.15; 12 x 8.- E1.35; 14 x 9- E1.50; 16 x TAPE OSCILLATOR COIL. Valve type, 35p. 6- E1.45; 16 x 10- £1.70. ANGLE ALI. 6 x 3/4 x 3/4in -15p. BRIDGE RECTIFIER 200V PIV Y amp 50p. E.M.I. TAPE MOTORS. 240V a.c. 1,200 r.p.m. 4 pole. Spindle ALUMINIUM PANELS. 6 x 4 -17p; 8 x 6 -24p; 14 e TOGGLE SWITCHES S.P. 20p. D.P.S. T 25p. D. P. D. T. 30p.. 0.187x0.75in. Size 3'/e a 21/2 x 21/4in. £2. Post 50p 3 -25p; 10 x 7 -35p ;, 12 x 8 -43p; 12 x 5 -30p; 16 x MANY OTHER TOGGLES IN STOCK Collaro gram motor 1 75p. 6 -43p; 14 x 9 -52p; 12 x 12 -68p; 16 x 10 -75p. PICK -UP CARTRIDGES ACOS GP91 £1.50. GP93 £2.50. 20V E.M.I. MANY ALI BOXES IN STOCK. MANY SIZES SONOTONE stereo E2.00- aram motor 240V £1.25. 337 WHITEHORSE ROAD, CROYDON RADIO COMPONENT SPECIALISTS Open 9-6. Wed. 9-1. Sat. 9R (Closed for lunch 1.15 -2.30) Radio Books and Components Lists 10p. (Minimum posting charge 30p.) All prices include VAT. (We accept Access or Barclaycard. Phone your Order) Tel. 01 -684 1665

www.americanradiohistory.com Wireless World, April 1977

HYBRID HIGH POWER POCKET IC AUDIO AMP. MODULES Features Push -Pull Output Freq. Response Flat to within 1/2 dB from 20Hz to 100 KHz 8 Ohm Output Harmonic Distortion ., ua,9 0.5% at full output -- Input Impedance The GR Electronics ., 40K -ohms T ¡' YPocket TTY offers the keyboard facilities Description of a teletype - at a fraction Made by the largest Hybrid Audio Amplifier Manufacturer in of the cost. the world - comes in 3 popular models. These are not kits, and a few external components, a heatsink and a power Outputs serial ASCII require supply. Build high quality sound systems using the economical code to any Teletype modular Sanken technique. Ideal for HI -FI systems, Stereo, -compatible device tape deck, FM tuners, record players, musical instruments, 20 mA loop or RS232 mode public address systems, A.C. servo and wide band amplifiers. 36 keys giving full 64 Each module has quasi -complementary class B output, character alphanumerics employing flip -chip transistors, etc., in rugged, compact and 9 digit LED display of lightweight packages. SANKEN = COMPACT POWER. characters entered All solid -state with SI1010G TEN Watts £4.76 ea. (ex VAT) TWENTY Watts £8.34 ea. (ex VAT) optical coupling for reliability SI1020G SI1050G FIFTY Watts £16.58 ea. (ex VAT) Pocket TTY can be used for microprocessor programming, All goods new, to full manufacturer's spec. No substandard parts sold. Callers production data entry, warehousing, mobile data collection, welcome. Colleges. Govt. and account orders welcomed training and education. TERMS: Non -Account Customers. Cash with Order Standard P &P 50p. Please For further add VAT to overall total details contact G.R. ELECTRONICS LTD. 80 Church Road. Newport NPT 7EH. Gwent, England. ALR8STR8 ELECTRONICS LTD. Telephone: Newport (0633) 67426 275 -281 King Street Hammersmith London W6 9NF Telex: Ref: 1796 28604 Tel. 01-748 3143/2960 Telex24443 WW - 066 FOR FURTHER DETAILS WW -105 FOR FURTHER DETAILS

TEAC® a TEAC Á3340 (S) REVOX A-700 SERIES ITA 10 4 The new big 4- CHANNEL Revox MODULAR deal for all MIXER studio re- RECORDER quirements Highly so- .n, phisticated design features dude servo ; i Z Q©re i - .tape tension. a ( e full deck ei, f itl _. ...`al logic. crystal led

spe, tape s IMMEDIATE DELIVERY footage ,counter.

,. TAhe7famhas A-77 SERIES Mk4 been consis- Ten balanced inputs; four output groups, 4 limiters; tently im- bass mid and treble EQ, modular construction, proved over q headphonep monitoring.g ExtremelyY high9 quality Me Ppast 8 construction only matched by mixers costing around ,'' years and £1,000. x the ' ,. is now avail- ' in the r latest Mk. 4 10-4 £690 version. The wide Industrial version upgraded to studio requirements. choice of 20-4 £1190 with increased signal to noise performance and specifications improved reliability. Four totally independent includes i ti n channels : X EIGHT OUTPUT £1360 each with sel sync, input mixing, switchable VU's and versions for tT I all the facilities for easy multitracking. This industrial duplicating model is in more studios than any other version and logging ,` ¡ IMMEDIATE DELIVERY applications Also available for hire Available only from /TA Backed by UK's latest Hire service. Check our prices (Semi-pro version also available) fastest ser- IMMEDIATE DELIVERY PRICES EXCLUSIVE OF V.A.T. IMMEDIATE DELIVERY aice. A 1 -7 Harewood Avenue, Marylebone Road, London NW1 Industrial Tape Applications Telephone: 01 -724 2497 Telex: 21879 W W - 100 FOR FURTHER DETAILS

www.americanradiohistory.com 112 Wireless World, April 1977

- TRANSISTORISED 3cm RADAR AMPLIFIER SWITCH: with 24v waveguide POWER UNIT TYPE 234: 200 -250v. a.c. input, 250- 0 -250v. d.c. at 100mA and 6 switch, .9 x .4 cm ins. with crystal CV.2355 and spark gap VX.1046. £16.20 + £1.00 3v at 4 amps output. £8.10, carr. £2.50. - post. REDIFON TELEPRINTER RELAY UNIT NO. 12: ZA -41196 and power supply TRANSISTORISED VIDEO INDICATOR (used with above amplifier): 11 200 -250v. a.c. Polarised relay type 3SEITR 80- 0 -80v. 25mA. Two stabilised valves - C.R.T. E10.80 + £1.00 post. CV -286 Centre Zero Meter 10 -0 -10. Size 8" x 8" x 8 ". New condition. £10.80, cary. IMO - IMP C RADAR RECEIVING ANTENNA TYPE X443 Mk. D: Suitable for detecting £2.50. signals on X, K, J and Q bands. 9gHz- 60gHz. Complete with waveguide horns, SOLARTRON PULSE GENERATOR TYPE G1101 -2: £81.00, carr. £2.50. associated crystals. Transistorised amplifier and geared motor, etc. £135.00, TELEPRINTER TYPE 7B: Pageprinter 24v. d.c. power supply, speed 50 bauds per - carr. approx. £5.00. min. S /hand cond. (excellent order), no parts broken £21.60, carriage £3.50 : DIODES: CD.384 - £2.00 per 100 + 20p post. AUTO TRANSFORMER: 230v. 50c /s, 1000 watts. Mounted in strong steel case 5' : VACUUM & PRESSURE SEAL TEST EQUIPMENT: Complete with 3 x 4" x 6' 2" x 7 ". Bitumen impregnated. E12.96, carr. E2.00. C gauges indicating 0 -20Ibs p.s.i., 0 -301bs vacuum. With stand, hand pump, etc., CRYSTAL TEST SET TYPE 193: Used for checking crystals in freq. range - £32.40 + £3.00 carr. 3,000- 10,000kHz. Mains 230v 50hz. Measures crystal current under oscillatory - ASHCROFT DEADWEIGHT GAUGE TEST SET TYPE 1300: 0 -25Ibs £64.80 + conditions and the equivalent resistance. Crystal freq. can be tested in : £3.00 carr. conjunction with a freq. meter. £27.00, carr. £2.00. E.A.L. ANALOGUE DIGITAL CONVERTER TYPE MPD. 120 -0: 7 -bit or 8 -bit CATHODE RAY TUBES: 5" screen, tupe CV -1536 E4.32 + £1.00 post. Type 95J20 mode. E70.00, carr. E2.00. square face 5" x 3" E8.10 + £1.00 post. C PAIGNTON dB SWITCH: High quality instrument stud switch, 20 -way, 2 -pole. POWER UNIT: 110,'230v. a.c. input. 28v. d.c. at 40 amps output E32.40 + E3.50. Dial marked,0 -60dB. As new. E3.78 + 60 ost. SMOOTHING UNIT (for the above Power Unit): £10.80 + £2.00 carr. UNISELECTORS: - r .ac on. win col s £4.90 CLASS 'D' WAVEMETER NO. I: Crystal controlled heterodyne frequency FAMo , meter covering 2 -8mHz. Power supply 6v. d.c. Good s /hand cond. £9.20 + C2.00 OUS 1 II carr. (col 0, RING TOROIDAL DUST CORES: Size 2'/2" outside, 13" 1 inside, 5/16" thick. Box z- I m - condition. £36 umg of two E1.10 + 30p post. c OTARY INVERTERS TYPE PE -2I8E: Input 24 -28v, d.c. 80 amps, 4,800rpm. CT.316 SOLARTRON OSCILLOSCOPE (CD -518): 3" tybe, d, O ut 115v. a.c. 13 amp 400 c /s. 1Ph. P.F.9 £21.60 + E3.00 carr. libration marker 1mHz and 100kHz. 230v a.c. single beam. E FR QUENCY METER BC -221: 125- 20,000kc /s complete with original m. dition. £35.00, carr. £2.50. call ation charts. Checked out, working order. £22.70 + £2.00 carr. : E SAFE 1 4 u u R: Max IOmA. Test pressure plete RE TIFIER UNIT: 200 -250v. a.c. input, 24v. d.c. at 26 amps output continuous in leather cas . 00, post £1,00. ing. E37.80, carr. £5.00. AVO TRANSISTOR ' .. R CT.446: E37.80, carr. £2.20. ADVANCE TCD.40 FREQUEN 0- 40mHzr -f Q,8)_-#.S4h90-rSo'st, BARGAIN MAPS - MARCONI FREQUENCY METER 1026/4: 200 - I000mHz 'as new' condition E32.40 or secondhand condition £24.30. Large stocks of unused U.S.A.F. surplus maps, weather charts, etc. including: 1026/2: 0- 100mHz £32.40 'as new' or s /hand £24.30. Carriage for all type £2.00. - + -0NC -E1 U.K. in full and part N.W. Europe. Scale 1:1,000,000! ANTENNA MAST 36ft: Aluminium, diameter at base 3 ", tapering to 2" at top, - - complete with red hazard lights, stays, guys, etc. Normally used with direction JNC -9N - N. Europe, U.K., Scandinavia. Scale 1:2,000,000. JN-2 1 N Europe (Mediterranean). Scale 1:2,000,000. C finding equipment. Approx. weight 3cwt. £106.90 (including 121/2% VAT), - SIZE: 58" x 42 ", colour. Many others. Please send S.A.E. for list. - carriage rates on request. WITH rotating Antenna suitable for 200- 400mHz Price each 70p (inc. p + p) £16.90 extra (including 121 /2% VAT). 25 x Maps (either same type OR assorted) E10.00 + £1.00 p+ p. BURGLAR ALARM BELL: 6 -8v. d.c. E3.24 + £1.00 post. - 10 x Maps (either type OR E6.00 (inc. p). C MEGGER (Record): 500 volts E21.60 £1.00 post. same assorted) p+ R -216 : RECEIVER MANUAL (Photostat copy): E1.50 inc. post. Above prices include VAT at 8 °° (except where stated) C MUIRHEAD ATTENUATORS: 75 ohms 0 -8Mc /s 3V MAK 3 ranges 0 -5, 0 -25, 0 -50dB. £3.24 + 75p post. Carriage quotes given are for 50 -mile radius of Hens. Visit our new shop in We High Street - (old A1O) opposite Church. 100s of - individual bargains for callers. If you wish IN to collect any of the above items please 3 & 3a BALDOCK STREET(, WARE, HERTS. SG12 9DT telephone prior to calling to avoid ásappointment. W . MILLS WARE 66312 (STD 0920)

J11N11111111111111111111111111111lI I1111111111.41 111 11 11 /111x11111111111111111111111111111111111111111111111111111111111-1111111a 1111 Ñ WEST HYDE Instrument cases WEST HYDE .Deulh CIO P P PRICES - 5 hui nut VAT MOD 3 (including cha.,. C 4 5 10., 65' 9.44 301 7.3 , 6.32 D 9 3, 6 5' 9.44 MOD 302 7.4 .. 6.78 E 9 10.45 303 7,6 .5'." 8.65 F 9 10, tì 5' 12.32 304 11,3 ,5'x" 7.78 5 13 3. s 5 10.45 9.18 H 13 7, 6 5" 12.32

306 11,6 ,5'. 10.95 I 13 I0x 65" 13.91 3 J 18 3x 65" 12.32 CONTIL TEXTURED K 18 7x 65' 16.97 " 8.77 L IB 10, 6 l and back panels grey PVC Alum mum - - - 5" 20.96 Offer á151" -) 8,7x,66" 10.42 M 4 5 3.13" 7.72 (Julep PVC steel sire ,gh I 075 9,5x7" 10.42 casing blue sleet or up to site L N 45 7.1'3 10.45 I a Also eia nn 12/7 a lab wood (Price as next ce s inountaig system u ad,' Ibn 120.7.. 12.01 w grain and black lot pr hlghe' le A removable PCB and SU O 45 10,13' 12/7 unpanrted 8.92 13.91 black, 301 price of 302. Bh 302 303, 6k 304 305 P 9 3.13" Block Is B i'lm) 16127 16,1x12" 16.55 10.45 O 9 7x13' 13.91 191010 19x10,10" 22 72 R 9 0.13' 16.97 ELF CASES 5my 6, s 13 3,í3- 13.91 Elf 6,4x4" 3.20 r 13 7.13 16.97 13 10x13" Bara Elf Mess II ch. ono 2.15 u 20.96 CONTIL Giant Ell 8.5':,5" 4.50 18 3,13" 16.97 Long Elf 9,4x3" 3.00 w 16 7x13 20.96 Jumbo Elf x 18 1U,í3" 24.62 5.40 Please check with us ELF CONTA 101Prilerat MOD -2 CASES prices an Cerr.et /including chassis/ Mod 2an Wuodg'auiof BI,,,, These tough little cases add very little to the cost of a lob Front panel 'V A 45x3,65.. 7.72 Potes m erses n -L 5 N 1. 45s 7. 65" 7.72 Prices 89 for one price up on ahinsuouris with p'otucl,vu coat Elf cases are avadablc ur4sites, all tlnugh Alin" .. 20p extra 612 only Mod. 2. e.g. Mod 2AW00dgra'n moulded ln grey glass polyester. all panels, feet and chassis included. or Black's as Mod 28

Ail We, Hyde cases ale available won substannaldiscounes tor yuaJi/' .'at Selland 25011 l ")0 on Prices inc/ ude P 5P and are less 10 " a collected. on first three pace breaks on cases only BUY A CASE FROM A SMALL RANGE, YOU GET A CASE -BUY A CASE FROM A BIG RANGE, YOU GET A SOLUTION Instrument cases BRIGHTCASE MARK II 'SAMOS 86212 I;f'," Fua nn, el 21.91 VI tolls 50.50,n,,, 1.36 13C222 13'.'- H.il Fl,a 115.84I S2 IOn.100,511'nu, 1.56 BC312t5'. Fan s124.04,S3 1110,150,50ir,n, 1.73 Rai, m 5C32215' "Ilan 17.72 54 125 50,76mn, 1.95 S5 125,100, /5 non 2.24 Nu, sea tiLnu.,s .rddL S6 17Ss15Os/Sn 2.62 SAMOS S7 125,200x75rran 2.91 A prestige anodised Case, black PVC steel top and but tom which can be MINOS Mlnlatwe also ument cases In blue and white PVC steel Assemble ln the M2 6S.100.51huu' .70 'HEAVY CASE louvred no Free or rack mounting, available DUTY lower hall clip nn feet, 2 screws allow the cover to hinge off eases. 2 more supplied at esta cost standing M3 100,130,50mm .89 8, 8,5 14.89 ln rack or hall -width assembled ln special polystyrene pack for-sale postage M2 B.ne .45 10,111,7' 16.54 to lis, PC feet are available to hold up la 4 PC boards honronGaly et case M3 saio .52 I12.1U,7 20.95

OVER 400 DIFFERENT CASES IN STOCK -SIZE BANGE MINOS OVER 5000!I IN VOLUME noes as January 77. Pt.a cheek waft us in o... of pnc. change Send for cataloue Smart miniature ARS cases ln tough rigid high gloss black Front panels Ava. a, steel, welded cornos either ah or PVC steel. Burls m slots for PC cards, dlvale,; el, Chassis or WEST HYDE ,n mind the door In Ihr base PC boards can be supported on 'P' clips from internal pillars 11, screws provided DEVELOPMENTS LIMITED Ryeteld Cos., Northwood Hills, Northwood, Middx.. HA6 INN Telephone' Northwood 24941/26732/27051 CASE SPECIALISTS i T.I.K: 923231 West Hyde Nthwd. El=1 WW -082 FOR FURTHER DETAILS www.americanradiohistory.com Wireless World, April 1977

Two books from Wireless World These books are of very special appeal to all concerned with designing, using and understanding electronic circuits. They comprise information previously included in Wireless World's highly successful Circards - regularly published cards giving selected and tested circuits, descriptions of circuit operation, component values and ranges, circuit limitations, modifications, performance data and graphs. Each of these magazine -size hard cover books contains ten sets of Circards plus additional circuits and explanatory introduction. circuit ,? designs Collected Circards

P Williams J Carruthers J H Evans J Kinsler P Williams J Carruthers. J H Evans J Kinsler

A WIRELESS WORLD PUBLICATION

BOOK 1 BOOK 2 Banc active filters Constant- current circuits Base logic gates C d as- signal process :ng Switching circuits Power amplifiers Wideband amplifiers C d.as - signal generation Waveform generators Astable circuits Alarm circuits C d as - measurement and AC measurements Optoelectronics Digital counters detection Audio circuits Micropower circuits Pulse modulators Monostable circuits Transistor pairs

ORDER FORM Name (please print)

To : General Sales Department, Address IPC Business Press Limited, Room 11, Dorset House, Stamford Street, London SE1 9LU. Please send me copy /copies of Circuit Designs -- Number 1 at £10.40 Circuit Designs - Number 2 at £1 2.50 Company registered in England and a subsidiary of Reed

each inclusive. I enclose remittance value £ International Limited Registered No. 677128 Regd. office SE1 (cheques payable to I PC Business Press Ltd.) Dorset House. Stamford Street, London 9LU. I

www.americanradiohistory.com 114 Wireless World, April 1977

The SECOND -USER R Systems , Peripheral Computer `VG Equipment & Components for Specialists Data Processing Mini- Computer Ke boards Exchange FRESH STOCKS PDP8M -ML 8K Processor. OF THE PDP11 /34 -MN 32K Processor with RX11 POPULAR 1 Twin Floppy Disk LA36 DECWriter, PC11 High CLARE -PENDAR ` b Speed Reader /Punch. ASCII KEYBOARD TYPE PDP8I 20K Processor with Extended Arithme- KB6 NOW TO HAND tic, Teletype Control, Clock, 2xTU55 DECtape 'ASCII -Coded ITL-c mpalible 4.bank drives, PCO8 Reader /Punch, 9 -track Incremental alphanumeric keyboards with ROM encoder chip. strobed output, two -key rollover Deck, RFO8 256K Disk. and debounce Standard 7 -bit ASCII code no panty) Supplied Nova 3/12 48K Processor with Teletype Con- complete With circuit diagrams and code chan trol, Clock. Memory Management. SPECIFICATIONS Power Supply a 5VDC o -5'h, 150mA -12VDC +: -10% Nova High Speed Paper Tape Reader. IOWA Output Logic Levels Data Brts 1 through 7 Ov O" 45V 2 6v Nova 1200 4K Processor with Teletype Control I 5 25V Fan Out One standard TTL load Strobe 2 to 1. 5 25V Ov "0 -' 46V Fan Our 10 standard TTL loads Strobe signal Clock. delay 10 milliseconds nominal to allow data to stabilise '111702 DEC Data Entry Term ñaI with single line KB6: 56- station standard Teletype layout AS RECOMMENDED FOR PRACTICAL WIRELESS VIDEO-WRITER PROJECT 32- character JUST RECEIVED SPECIAL PURCHASE OF DATA DYNA- Price E39.50 + display complete with control for - El P&P + 8% VAT (send 013 74) PDP8E. MICS MODEL 390 TELETYPE TERMINALS IN BRAND NEW ALSO CONDITION. AVAILABLE - SPECIAL LOW -COST KEYBOARD K85: 3-bank alphanumeric Baudot.coded TU60 DEC Dual Cassette Drive with control for TERMINALS - LARGE STOCKS AVAILABLE. A5533 Teletype 36- station keyboard TTL.compahble htrobed output Price P from E000.00. KSR33 Teletype Irom E325.00. ASR35 Teletype E20.00. plus El &P + 8% PDP11 series. VAT (send a 22 68) from E750.00_. IBM731 ; 0 Gollba0 Typewriter from £275.00_ Calcomp Digital Incremental Plotters. SPECIAL OFFER ÑFWARRIVALS FABULOUS NEW 95- STATION CRT DISPLAY KEYBOARDS. Model 563: 31" drum, Cossor DIDS 401 2A Visual Display Units. 13 Imes a 80 characters 300 steps per second. 8-bit ASCII code. upper and lower case output PLUS separate numeric (81/2x4Vt" screen) 64 character repertoire with detachable ASCII Model 565: 12" drum, pad TEL Logic. Delayed strobe signal two 300 steps per second. keyboard (Control device required) %enjoin Mee: E145.00 and -key rollover feature. Mounted on attractive Model 663: 31" drum, steps Also available box overall dimensions 201/2x 71/4x3)4" Price 300 per second. Como, DIDS 402.2A. as above but Incorpora)inp + control logic Price £295.00. E55.00 E3 carriage + 8% VAT (send E73.44). DF32 DEC 32K Disk Drive & Control (slave BCD-CODED 54-STATION KEYBOARD, brand new. upper and FOR IBM 360 USERS. Sanders 720 Data Dispisy System consisting. drives type DS32 also available). lower case outputs Mounted on double PCB andsét In attractive panel of six VDUs. control and unit communications buffer. Complete with incorporating 5 indicator lamps and on /oil switch Dimensions KKBE set of PDPSE series processor connecting cables and technical documentation. Prae £2,750.00. 151/2s51/2x21/2"Price E39.60 + E2 P &P + 8% VAT (send E44.82). modules. MINIATUREMATRIX PROGRAMME BOARDS: Brand new X.V Also available A few only of the above model WITHOUT ENCODING ' Matrix boards. with 3mm grating 3x10 posdlons I14a "x1 "I E4.00 OR PANEL Price E25.00 + E1 50 P &P + 8% VAT (send E28. 62). P&P 40p. OUR STOCKS ARE CONSTANTLY CHAN- 15-KEY CALCULATOR KEYSOARDS (0.9. CK + - .MAGNETIC TAPES. Manidacturen surplus stocks. brand new in. Make /break switches mounted on PCB Overall dimensions 150 x GING - please phone for latest availabilities. original sealed packing. 1/2"x2400' E4.00 per reel P &P extra 110 e 40mm. Psis* £4 plus 5op P &P + VAT (Send E4.86p).

Add S-. VAT to ail killers mE Monday ro Friday 9 11,m prices shown. ELECTRONIC BROKERS Sales&ServlcesDIvislon) to - LIMITED ( 5 pm Carriage extra 49 -53 Pancras Road, N 1 TeI:O1 details on request - London W 2QB. -837 7781

WW-112 FOR FURTHER DETAILS

LYNX ELECTRONICS REGULATORS OPTO ELECTRONICS (London) LTD. 723 0.45 CLOCK IC 7805 1.50 DISPLAYS LED SOCKETS 704 0.99 2 Red 0.13 CHIPS Pin 92 Broad Street, Cheatham, Bucks. 707 Tel (02405) 75154 7815 1.50 0.99 2 Green 0.20 MM5314 4.25 14 0.16 727 2 Clear 0.14 VAT 8% except * which are 121/2 Return 7818 1,65 MM5316 5.95 6 Pin 0.18 % Post Service 8 1.95 24 Pin 0.45 LM340-5 1.36 747 AAY- 51224A3.25 4007 40 Pin 0.80 P &P 30p. Overseas 90p. Matching 20p per pair New Price List 20p 750 1.SO AAV 5 D9 LM340 12 1.36 Prices correct at 28th Feb. '77. ACCESS WELCOME LM340 -18 1.35 TRANSISTORS THYRISTORS AC126 0.15 BC161 0.35 BD131 0.36 BF60W 0.39 OC72 0.22 2N3705 0.10' TTL 7400 SERIES AC127 0.1{ BC168 0.09' BD132 0.40 BFX29 0.26 0084 0.40 253706 0.10' Rh IA 0A a 4A M 88 IW 156 8C169 0.12' 50135 0.36' 11051 (Stud) IC1061 1102201 )10220) IT02201 )10481 ÁC728 0.11 BFX30 0.30 0L139 1.30 253707 0.10' 7400 0.16 7480 IT02201 BC169C 0.14' 0.55 200 0.35 0.50 0.45 0.40 0.60 OM ass 1.14 AC128K 0.26 80136 0.39' 8Fx84 0.23 0C140 1.30 253708 0.09' 7401 0.16 7482 AC141 8C1705 0.1r BD137 0.40' 0.75 400 0.40 860 0.50 0.45 OSI 0-M 0.98 1.40 0.22 BFX85 0.25 0C170 0.23 2N3709 0.09' 7402 0.16 7486 0.32 ACI41K 0.34 BD138 0.46' 600 065 0.65 0.70 109 1.19 1.2s 1.110 BC171 6.12' BFX86 0.25 TIP294 0.44' 253710 0.10' 7403 0.16 7489 2.92 8C1728 0.12' BD139 0.56' VIM 61107 67108 87109 61116 253525 AC142 0.15 BFx87 0.20 TIP30A 0.52 253711 0.10' 7404 0.18 7490AN AC142K 0.32 BC182 0.11' 80144 2.20 0.49 MOO LIAO Et.60 OM MOO E0.50 BFX88 0.20 7IP314 0.54 2N3715 1.70 7405 0.18 749IAN 0.65 AC176 0.16 BC182L 0.12 80157 0.40 BFX89 0.90 TIP324 0.64 253716 1.50 BC183 0.10' 7408 0.18 7492 057 ACI76K 0.32 BD181 0.86 BFY11 1.10 TIP414, 0.68 263771 1.60 7409 BC183L 0.10' 0.18 7493 0.45 AC187 0.18 BD182 0.92 BFyte 0.50 TIP42A 0.72 2N3772 1.90 7410 0.16 ACI87K 0.36 80184 0.11' 80183 0.97 2N404 0.40 7494 0.65 TRIACS Plastic TO-220 Package Isolated 8FY40 0.50 2N3773 2.10 7412 0.25 7495 6.67 - AC188 0.16 BC184L 0.12' B0184 1.20 BFV41 0.60 25696 0.20 253819 0.28' BC186 0.20' 7413 0.25 7496 0.82 Tab AC188K 0.32 013232 0.60 BFY50 0.20 2N697 0.20 2N3904 0.16' 7414 0.72 74100 1.07 4A AD149 0.46 BC187 0.24' 80233 0.48 BFV51 0.18 26706 0.15 6.SÁ 8.54 IM 1511 2N3906 0.1V 7417 0.43 74107 0.35 AD161 0.36 BC207B 0.12 BD237 0.55 13FY52 0.19 2N718 0.22 2N4123 0.14' 7420 NI I6l III P) 11) 16) 111 161 hl NI IBC212 0.1V 8D23e 0.60 0.16 74121 0.34 ÁD162 0.36 BFY53 0.25 25929 0.16 264124 0.14' 7425 0.30 74122 0.47 IDOL oM oso 0.70 0.70 078 0.76 0.53 053 Ill 1.Ot ÁF114 802121 0.12 80410 0.60 BFV64 251131 0.15 AL 0.61 0.64 0.75 0.20 0.35 254290 0.14' 7427 0.48 74123 0.40 0.75 0.67 O.t7 0.97 1.01 1.17 1.17 AF115 0.20 8C213 0.12' 80X32 2.30 81Y90 0.90 261132 0.16 264291 400o 0.77 0.78 0.80 0.83 0.97 1.01 0.14' 7430 0.15 74141 0.78 1.13 1.19 1.70 1.74 ÁF116 0.20 80213E 0.14' BDY10 i 50 8LY15A 261302 0.40 2N4292 600o 0.96 699 1.01 1,10 1.21 0.14' 7432 0.37 74145 0.88 1.26 1.42 1.50 2.11 2.17 AF117 0.20 BC214 0.14' BDY11 2.00 BSX19 0.16 2N1303 0.40 2N4347 1.10 N.B. Calms waksut interns) trigger will Muni logger 7437 0.35 74154 1.82 s) 161 AF118 0.50 8C214L 0.15' 80Y20 0.80 8SX20 0.15 261304 0.46 2N4348 1.20 7441ÁN AF124 0.25 BC237 0.16' 130Y38 0.60 0.76 74164 0.53 BSX21 0.20 251305 0.45 254870 0.35' 7442 0.65 74165 AF I25 0.25 80238 0.16' BDY60 1.70 85X76 0.30 043 2N1306 0.50 254871 0.36' 7445 1.50 74174 AF126 0.26 BC300 0.34 131)Y61 1.65 85577 0.30 1.00 * * * SPECIAL OFFER SECTION 2N1307 0.50 254918 0.60' 7447AN 0.81 74175 * * * AF139 0.35 BC301 0.32 BDY62 1.15 85578 0.35 2N4919 0.70' 0.94 251308 0.60 7448 0.81 74180 1.06 AF239 0.37 BC302 0.40 BDY95 2.14 8SY52 0.28 2N1309 0.80 2N4920 0.50' 7470 SG309x E1.25 rIL209 Red .12 71 E7.15 AL702 1.46 BC303 0.46 BDY96 4.96 85Y53 0.32 74181 3.20 0.39 251711 0.24 2N4922 0.68' 7472 0.28 NPN TO.3 POWER RECTIFIERS AL103 1.30 80307 0.16' BDY97 2.45 BSY54 0.33 254923 0.46' 74191 1.33 5-t2 DO-4 2N2102 0.44 7473 0.30 TRANSISTORS ITT BRANDED PACKAGE AU107 3.30' BC308 0.15' BF127 0.50 BSY55 0.74 74192 1.35 252217 0.30 ReriNora 7474 Fully tested but TRANSISTORS 10A AÚ110 1.76' BC309 0.18' BF157 0.50 13SY65 0.32 74193 1.35 50V 0.40. 0.30 2N2369 0.14 E24 Sedge 7475 unmarked Similar Medium Voltage Please AÚ113 1.60' BC310 0.20' BF177 0.25 0.47 74194 1.20 speedy BSY76 0.20 2N23694 0.14 10ohm -10meg 7476 to 263055 High Gain Type 10A BC107 0.09 BC317 0.l2' BF178 0.28 0.38 74196 1.4)t except 100V 0.45. BSY78 0.75 2N2483 0.20 4 wart 1.5 BVCED = 50+ BSY65 Polarity BC1O7B 0.09 BC319 0.13' BF179 0.30 BSY95A 0.18 252484 0.16 +.y watt 2,0p HFE'gaod = Similar to 10A BC108 0.09 BC320 0.16' 8£180 0.30 1.60' 20+ 200v 0.60. BU105 2N2646 0.50 at 3A. BC10718/9 BCIOBB 0.09 BC321 0.18' 8£181 0.30 BU105/02 1.90' 252711 0.20 VCE Stud Cathode or Camels. SAT<1 3V at 25 pcs E1.20 10A 400V BC109 0.09 8C323 1.60' 8£182 0.30 2N2712 3A 0.60. BU108 3.00' 0.15 e280sari. pcs 100pcs E3.50 Anode 8C109B 0.09 BC327 0.16' 8E183 0.30 BÚ109 LINEAR I.C.s 5 E1.00 Stud 2.50' 2N29044 0.20 DI Op 22 ep 25 pcs TO-3 HARDWARE Ideal for BC109C' 0.12 BC328 0.16' 8F184 BU126 E4.00 Power 0.20 1.80' 252905 0.15 301A 50 pcs Mica. Washers, Supplies, Inverters. BC117 0.19' BC337 0.17' 8£185 0.20 BU133 1.80' 2N2905A 0.22 0.40' MC1310E1.18' £7.50 015 4p 22 911 100 pcs Solder tag, Nuts, 80119 0.25 BC338 0.17' 1.60' 307 0.55' MC1351P0.75' E13.00 etc 8F194 0.10' BU204 2N2906 0.18 380 Bolts 8C125 0.18' BC407 0.22' BF196 0.12' BU205 1.90 262925 0.14' 0.90' MC1352P0.75' 022 4p 47 10p 381 1.80' 50 sets for 854 BC126 0.20' BC408 0.2r BF197 0.12' 8Ú206 2.40' 2529260 0.09' MC1353P0.75 * * * * * * 3900 0.70' MC1458P0.77 8C140 0.32 8CY30 0.55 8£200 0.40 BU208 2.60' 2N2926R 0.10' 033 4p 68 149 709 BC141 0.26 BCY31 0.55 8F218 0.30 MJ480 0.60 262926Y 0.09' 0.27 MC1496L0.82' BC142 0.23 5CY32 0.80 252926G 0.10' 047 741 0.35 7ÁA300 1.61 BF219 0.30 MJ481 1.05 1 0 17 5' 536- BZX83 Series 54002 0.05' BC143 0.23 BCY33 0.65 BF220 0.28 MJ490 0-90 263053 0.20 p 748 0.35 7ÁÁ310A 1.3t DIODES NE555 0.45 3000.12 0.11 54003 0.06' 80144 0.30 8CV34 0.55 744550 0.45' 600 0.15 BZY88 Series 068 Sp 1 5 25p NE565 2.00' TAA611812 64004 0.07' BC147 0.00' BCV38 0.50 8F244J 0.17' MJE340 0.40' 2N31133 0.30 85145 0.14' 9000.16 0.11 N4005 0.08' BC148 0.09' 8CY39 0.30 NE566 1.50' 1.25' B4148 0.13' 1.15 sp 22 29p NE567 1200 021 50149 0.09' BCY40 0.75 253137 .10 1 2.00' 144861 0.05 54155 0.13 BV538- BF257 0.35 MJE5207 0.55 C43045 oÁ50 040 64007 0.10' 8C152 0.25' BCY42 0.30 BF259 0.48 2N3440 0.56 15 0.55' 154530 1.55' BÁ157 0.12 0C43 0.95 4, CA3046 0.50' TBA53001.90' 3000.55 0495 0.12 N4148 0.04' 5C153 0.18' BCV54 1.60 8£336 0.35' 0C44 0.32 253442 1.20 BÁ157 0.22 6000.56 OÁ90 0.08 BCI57 0.09' BCY70 0.12 OC45 - CÁ3130 0.79 7BÁ560 2.80' BÁ158 BF337 0.32' 0.32 2N3570 3.60 ,í1í.o 0.22 9000.80 OÁ91 0.05 5C158 0.09' BCY71 0.15 0C46 0.20 2N3702 0.10' w,.ibbM MCI303L0.55' í8A570 0.98 BÁ759 0.25 8£338 0.45' p ulwvalvsa MC1304Pt.80' 1200 04200 0.09 80159 0.09' BCV72 0.12 OC 70 0.30 253703 0.10' °p 7CÁ27050 BY206 0.15 BFW30 1.25 Po1e"nonuners MC1307P0.85' 52561 Series IN914 0.04' BCI60 0.32 0.16 71 253704 1.86' 80115 BFW 59 0.30 OC 0.35 0.10' and eleclwiytic. BY207 0.20' 0.26 164001 0.04'

www.americanradiohistory.com 115 Wireless World, April 1977 low cost -top quality COMPONENTS

Distributors for Plessey .Siemens . A.E.G.Telefunken and Toshiba Components

Diodes Semi Conductors Semi Conductors Semi Conductors (p) Type Price (p) Type Price (p) Type Price (p) Type Price (p) Type Price (p) Type Price (p Type Price (p) Type Price 38 62 BA115 10 0A90 7 BC117 14 BC237 12 BF115 38 BFX88 25 9C72 TIP32A R2Q08B £2.10 TIP41A 70 BA145 18 0A95 6 BC1I8 15 BC238 12. BF123/ OFY50 20 30 R2010B E2.10 75 BA148, 18 0A202 11 BC119 27 BC301 301 T092 25 BFY51 TIP42A 20 RCA16334 80 BA154 12 IN60/0A91 7 BC125 174 BC303 30I BF152 20 BFY52 TIS91 27 BFY90 £1.10 RCA16335 80 2SC1172A £2.73 BA155 15 1N914 6 BC125B 18 BC327 13I 8E158 20 BR100 32 S.2802 2.99. 2SC643A £1.48 BAX13 6 1N4001 64 Ba26 16 BC328 13 BF160 35 BR101 38 £4.90 4.43MHZ BAX16 10 1N4002 7 BC132 15 BC337 12I BF167 28 5.6080A BRC4443 BO Crystal £1.10 BY126 101 1N4003 8 BC135 20 BC338 12 BF173 32 TIP31A/ BRY39 38 2N5298 52 BY127 12 IN4004 á BC136 16 BC546 13 BF178 33 30 0Y133 1/1 IN4005 9 BC137 25 BC547 12 BF179 38 BSY52 BT106 £1.20 BY199 25 1N4006 91 BC138 33 BC548 12 BF180 36 Integrated Circuits 17 IN4007 10 BC139 28 BC549 13 BF181 36 BT108 E1.50 BY206 MC 1349 £1.02 SN76660N 66 16 IN4148 44 Bt140 32 BC550 14 BF182 30 BT116 £1.25 BYX10 ML231B E4.20 SN76566N £1.10 8 BC141 28 BC557 13 BF183 30 BU105/02 E1.90 0A47 ML232B £4.20 TAA550 39 BC142 25 BC558 12 BF184 30 BU108 E2.10 SL414A £1.68 TAA570 £1.30 Semi Conductors BC143 28 BCY72 16 BF185 30 BÚ126 £1.49 SL415A £2.20 TAA661B 81 10 BD115 BÚ204, £1.80 Type Price (p) 8C147 39 BF186 32 Type Price (p SL1310 £1.54 TAA700 ! £2.56 BC147A 11 BD116 65 BF194 lo BU205 £1.67 AC107 25 AF115 27 SL1327 97 TBA120AS 69 BC1478 11 BD124 75 BF195 10 BU206 £2.10 AC126 20 AF116 27 SL3046 73 TBA120SQ £1.14 BC148 10 BD131/ BF196 10 8U208/02 £2.75 AC127 20 AF117 27 SL76544 £1.50 TBA440 . £3.00 BC149 10 BD233 43 BF197 11 BUY698 £2.50 AC128 15 AF118 65 SN7600IN £2.45 TBA4800 £1.40 BC153 20 BD132 45 BF197A/ BUY69A E2.65 AC128K 30 AF124 40 SN76013N £1.65 TBA5200 £2.06 BC154 20 BD133 5 BF597A 174 E1222 38 AC141 24 AF125 32 SN76013ND £1.40 TBA5300 E1.30 BC157 11 BD135 29 BF198 30 M1E340/ AC141K 34 AF126 38 SN76023N £1.65 TBA540Q £2.00 BC158 10 BD136 30 BF199 25 BF459 48 ÁC142 20 AF127 42 SN,6023ND £1.40 TBA5500 £2.56 BC159 11 BD137 30 BF200 30 M1E520 44 AC142K 36 AF139 45 SN76033N £2.45 TBA56000 £2.56 BC160 30 BD138 33 BF218 56 2N696 30 AC151 28 AF178 69 SN76110N E1.75 TBA750Q £1.43 BC161 33 37 8E224 , 20 2N706 15 AC154 18 AF180 69 BD139 TBA800 £1.10 BC171 10 2N3053 20 SN1622 N £2.20 AF181 69, BD140 39 BF240 18 £2.64 AC155 18 SN7622 N £1.65 TBA9200 BC172 10 BD144. £1.99 BF241 18 2N3054 65 AC156 24 AF239 45 TBA9900 £2.56 BC173 15 2N3055 60 N7653 N £1.60 BD160 £1.65 BF257 28 TCA270Q AC176 22 AF240 20 SN7653 N £1.60 £2.64 BC178 18 BD181 90 BF258 30 2N3702 12 AC176K 34 AL102 nA.40 £1.80 TCA800 £4.60 ßC1788 2Q BD182 90 BF259 30 2N3703 12 AC187 20 AL103 £1.30 SN7665 £1.50 TDA440 £3.00 BC179 24 BD183 80 BF336 17 2N3704 10 AC187K 36 AÚ107 £1.50 BC182 11 BF337 35 7,43705 10 AC188 25 AU110 £1.30 BD184 £1.10 BC182L 12 50 8F338 34 2N3706 10 Toshiba AC188K 38 AU113 E1.30 BD222 BC183L 17 BF355 50 2N3819 38 AC193K 36 BC107 14 130225 47 Type Equivalent Price BC184 13 BF457 37 2N5293 5Z AC194K 35 BC107B 16 00232 50 TA7050P CA3044 RCA £1.13 BC186 25 BF458 37 2N5294 52 AD140 69 BC108 14 BD233 43 TA7051P CA3042 RCA £1.45 BC187 25 BF459 48 2N5295 52. AD142 75 BC109 14 00234 49 TA7072P MC1351 Motorola £1.53 dC204 14 BFT42 36 2N5296 461 AD143 65 BC109C 14 BD235 49 TA7074P MC1352 Motorola £1.34 BC212 11 BFT43 35 2145297 52 AD149 70 BC113 15 BD236 53 TA7141AP MC1327 Motorola £1.40 BC212L 12 BFX29 29 2N5298/ AD161 50 BC114 15 OD237 49 TA7171P SAS560S Siemens £1.65 BC213 12 BFX84 29 TIP31A 52 ÁD161 /2 £1.00 BC115 171 BD238 55 TA7172P SAS570S Siemens £1.65 BC213L 11 BFX85 30 2N5496 53 AD162 50 BC116 174 BDX32 £2.75 TA7173P TCA270 Philips £2.2Ó BC214 13 80 BFX86 28 0071 29 AF114 27 BC116A 30 BDY20 TA7176P CA3065 RCA £1.30 BC214L 15

COMBINED PRECISION COMPONENTS LTD. Good people to deal with

C.P.C. Dept ERT 194200 North Road, Preston, Lancashire, PR1 1YP. England. Phone Preston (STD 0772) 55034. Telex 677122. Cables'Comprecom" Preston WORLD WIDE EXPORT SERVICE ask for ROBIN PRATT NEW PRICE LIST 1.377

WW - 106 FOR I LIIER DETAILS

www.americanradiohistory.com 116 Wireless World, April 1977 SEMICONDUCTORS - COMPONENTS TRACS CARBON POTE NTIOMETERS SINGLE GANG w,th vv end te s bine, SOmm plasuc shalt 1Umm bushes supplied won LINEAR PAKS ,hake prom To n 2 Amp TO5 Case 10 Amp. TO48 Caw washerl and nut le ra r:e i 20 nl n i,tanr:,' Manufacturers Fall Outs which include No Price Volts No Price Functional and part Functional Units These are 00 TRI2A 100 E0.31 100 TR1104 100 £0.77 LINEAR TRACK LOG TRACK classed as oul'ol. spec from the makers very 200 TR12A 200 E0.51 TR110A 200 200 £0.92 Value No. Price Velue No. Price aged specnccal,ons but are ideal for learning

400 TR12A 400 TR110A I E0.71 400 400 E1.12 1K 1831 '£0.22 4K7 1842 '(0.22 about C s and experimental work 2K2 1832 '£0.22 10K 1843 U721 30 ASSORTED LINEAR TYPES 4K7 1833 'E0.22 '60.22 22K 1844 709 -741.747 748.710 5.68 Etc 6 Alp T066 Caw 10 Amp 70220 Caw 10K 1834 'E0.22 Volts No Price 10.22 47K 1845 ORDER No 16227 Price 1.60 Volts No Price 18±5 '£0.22 100 TR16A -100 £0.51 TR110A 400P 22K '£0.22 t00K 1846 'E0.22 400 E1.12 47K 1836 U76SD FM STEREO DECODER 200 TR16A 1200 £0.61 '60.22 220K 1847 ALS t00K '£0.22 5 IC s 76110 Eqv to MC1310P -MÁ767 Data 400 , R16A 400 £0.77 1837 '60.22 470K 1848 80 100 £0.23DI: 032 £0.23 220K '(0.22 supplied with pak 1838 '60.22 IM 1849 '£0.22 470K 1839 '60.22 2M2 1850 (0.22 1M 1840 '£0.22 BA AUDIO POWER °ulna..AMPkF- 2M2 1841 '(0.72 RS ss ned types SL403 76013 76003 Etc Oat °polled with pak SUPER UNTESTED PAKS DUAL GANG. , UV, qudhty pots hued w end Ierminnt n., timor S(.1ne, tans. , ROER No 15226 'Cl 00 PAK No. Order No. Price .a)ptied writ, shakepruol ,ewas, r and not r Track lulerare,. f 211 bui realehet/ to vv.rr.. L, ' le) Germ Gold bonded 044 7 diode 16130 £0.60 U51 150 Germ 0A70 81 diode 16131 £0.60 U52 100 &boon Orodes 200mA 0A200 16132 £0.60 LINEAR TRACK LOG TRACK U53 150 diodes 75mA 1N4148 16133 £0.60 Value No Pu Value No Prior. 74 SERIES PAKS U54 50 SII Rect Top Hat 750mA 16134 £0.60 185', 4K7 'E0 68 18ÖÚ '(0.68 Manufacturer s Fall Outs which mclude U55 20 SII Root Stud Type 3 Amp 16135 £0.60 t01K 1852 'EO 68 1861 E0.68 Functional and part Functional Unas These are U56 50 400mVV Zeners 007 Case 16136 £0.60 22K 1859 '£0 68 1862 '£0.68 classed as out'of.spec from the maker svery. rigid U57 30 NPN Trans 13C107 8 Plashc 16137 £0.60 47K 1854 'E0 68 1863 '60.68 specifications but a e ideal for learning about U58 30 PNP Trans BC1 77 178 Plastic t6138 £0.60' 100K 1855 '60.68 1864 'E0.68 I C s and experimental work U59 25 NPN 7039 2N697 2N1 1 1 sil 16139 E0.60 220K 1856 '60.68 '20K 1865 'E0.68 U60 25 PNP 1059 2N2905 snccon 16140 E0.60 74G 100 Gales assorted 7400.01 04 11150.60 470K 185/ 4 /0K '60.68 1866 'E0.68 c No 16224 U61: 30 NPN TO18 2N706 silicon 16141 60.60 IM 1858 Order E1.20 '60.68 1M 1867 'E0.68 74F 50 Flip Flops assorted U62 25 NPN BFY50 51 16142 £0.60 2M2 1859 '60.68 2M? 1868 'E0.68 063 30 NPN Plaste 2N3905 s,econ 16143 £0.60' 7470.7273.74.76.104.109 Etc U64 30 PNP Plasfrc 2N 3905 sa,con 16144 £0.60' Order No 16225 £1.20 U65 30 Germ 0071 PNP 16145 E0.60 74M 30 MSI assorted Types 7441 47 90.154 U66 15 Plastic Power 2N3055 NPN 16146 E1.20 SINGLE GANG SWITCHED. Fated with double pole on oft switches The swacn act.on es incorporated Etc Order No 16226 61.20 rotary U67 10 TO3 Metal 2N3055 NPN 16147 £1.20 wane, the acnon of the pot Switch rating 1 5 amps al 250V AC U68 20 Umfunction bans 11543 16148 £0.60 U69 10 1 amp SCR 1039 16149 E1.20 LINEAR TRACK LOG TRACK 1170 8 3 amp SCR 1066 case 16150 E1.20 Value No Price Valu. No. Price 4K7 r870 '60.48 4K7 1879 '(0 VEROBOARD PAKS No s rnentroned above are giver, a guide to the tope of device ,n 10K 1811 Code '60.48 10K 1880 £0.48 V61 Appros 30 ou rs vapor sips all 1 the pak The dev ces themselves are normally unmarked 22K 1812 '(0.48 22K 1881 'E0.48 mauix Order No 16199 E0.60 47K 1813 '£0.48 47K 1862 'E0.48 VB2 Appro. 30 sq varrnus sir P I 100K 1874 '60.48 1883 '£0.48 mal,. Order No 162005 £0.60 220K 1875 '60.48 1884 'E0.48 470K 1816 '£0.48 1885 '(0.48 1M '60.48 1886 'E0.48 COMPONENT PACKS '60.48 1887 'CO 48 Pack ELECTROLYTIC PAKS No. Qty. Order No Price A any' ul pak s e )y 18 5rs1 qualify red value miniature electrolyt,cs Cl 200 Resistor meted value appro. ICounl by weight) 16164 10.60 VEROBOARDS EC1 Values from 47-F0 to 10mFO C2 150 Capacitors m fed value appro. (Count Order No 16201 10.80 EC2 Values from 111th FO by weeght) 16165 10.60 DRILLED COPPER P.C.B to 110mF0 Order No 16202 'E0.60 C? . 50 Precision resstors Meted values 16166 1E0.60 1 Pa 15 each EC3 Values from 100 ,,10 to 680mF0 C4 80 retti' W Resistors meted preferred 2i5e No Rice Sexe No. Price values 16167 Order No 16203 '60.60 10.60 25 x5' £0.46 2209 61.13 C5 5 Pieces assorted ferrate rods 16168 10.60 7 5 a 3 75 £0.39 5 2210 £0.42 C6 2 Tuning gangs MW 1W VHF 16169 10.60 2 5 . 17 El .42 1 5 . 3 7 5 2211 £0.31 C7 1 Pack woe 50 metres assorted colours 375 .5 2204 £0.52 375 2212 61.51 C280 CAPACITOR PAK single strand 16170 (0.60 .17 3 75 . 3 75 2205 60.46 375 .5 2213 £0.57 75 Mullard C280capacrtors mixed C8 10 Reed switches 16171 10.60 Glues ranging from 01 uF to 3 75 x 1 7 2206 El .82 375 .375 2214 £0.42 C9 3 Macro switches 16172 10.60 2 2uF complete with .dentrb..at,on 475 179 2201 62.34 1 (pack of level 2216 £0 52 C10 15 Assorted 16173 '£0.50 shier Order No 16211.1 '1 I 20 pots 2 5 1 (pack ul rive, 2209 CO 57 C11 5 Metal lack sockets 3 r 3 5mm 2 a standard switch types 16174 '60.60 C12 30 Paper condensers preferred types i,ed values 16175 10.80 DRILLED PLAIN P.C.B. CARBON RESISTOR PAKS C13 20 Electrolybcs trans types 16176 10.60 :nose pales contain a range of Carbon Resistors C14 1 Pack assorted hardware - Nuts .15 Pitch assorted en o the following grnops Sere No. Si No PriCal bolts grommets a 16177 10.80 Price SI. R t 60 I muted 1/riw tohm s 820ohsm o 1/ , C15 5 Mains slide switches ass 16178 10.80 £1.18 , 17 1221 60.78 Order No 16213 'CO.60 /5 t 17 C16- 20 Assorted tag stops and panels 16179 60.60 .75 2218 E0.26 3 2222 61.00 R2 60 mired w IKuhn, 8 2Kohms C17 15 Assorted control knobs 16180 '60.60 , ) 15' 2219 £0.42 2 5 a 2223 60.26 Order No 16214 '60.60 2 5 x 3 15 2224 £0.21 C18 4 Rotary wave change switches 16181 '60.60 R3 60 m,aetl r ' OKehms- 82Kehms 5 a3 75 2225 £0.36 C19 2 Relays 6 - 24V operating 16182 '60.60 VERO SPOT -FACE CUTTER Order No 16215 10.60 C20 1 Pak copper laminate appro. 200 sq ,der No 2231 Price £0.68 ea 60 mixed '.w 11,10 hms- 820Kohms Order No 16216 '(0.60 16183 C0,60 l'IOohms C21 15 Assorted fuses 100mÁ5 amp 16184 E0.60 RS 40 mired w 820ohms C22 50 Metres PVC sleevmg assorted vie and Order No 16217 10.60 colour 16185 E0.60 PLUGS AND SOCKETS R6 40 mred w 1 r ohms 8 2KOhrrrs C23 60 /t watt resistors meted preferred values Order No 16218 '(0.60 16188 10.60 R7 40 mraed lllohms 82Kohms COO Presets PLUGS CHASSIS SOCKETS 25 assorted type and value 16186 '60.60 Order No 16219 10.60 C25 30 Metres straodeo wire assorted colours 16187 60.60 No Price No. Price RB 40 mixed r w 10. ohms 820Kohms P1 VIN . 1 pat speaker 1689 10.08 CSI VIN , I, n loudspeaker Order No 16220 '60.63 P2 DIN 3 pu' 1690 '60.12 1652 '£0.08 R9 60 mired e I Vey IOM c'I" P3 DIN : pt)' 1691 '60.16 C52 DIN 'i, 1653 10.10 wOrder No 16230 'CO 60 P4 DINS p 180 1692 10.14 C53 OIN I, 111 1654 '60.10 RIO 411 m..90 '.w I Meg 10M. PS DIN 5 pen 140 169:1 10.15 CS4 DIN 5' .''10 1655 '60.12 Orde, No 11, 'F0 60 SLIDER PAKS P6 DIN h I,, 1694 10.20 055 Jack anur 1656 10.06 P7 VIN u 1695 10.20 056 Jack r m 185/ '60.06 Pack P8 Jack 2 5mm.,,.,eened 1696 10.12 CSI Jack Mlnu switched 1658 10.15 Price No. Qty. Order No. P9 Jack Plug ! Sm m plastic 1697 10.10 CS8 Jack Stereo switched 1659 10.18 WORLD SCOOP! /10 Jack Plug 3 Sm.n screened 1698 10.15 059 Phono single 1660 10.08 JUMBO SI 6 Slider potentiometers meted values 16190 10.60 Jack Plug mono plaste 1899 '60.14 0010 Phono double 1661 '60.10 52 6 Slider porenhomeres all 4 /0 ohms 16191 10.60 Jack Plug mono screened 10100 10.28 0511 Coat surface 1662 10.21 SEMICONDUCTOR PACK 53 6 Slider potentiometers all 10k fen 16192 '60.60 Jack Plug stereo screened 16101 10.32 C512 Coax flush 1663 '60.25 Transistors - Germ and Rectifiers lee Srl,con 0,ode, S4 6 Slider outen),omelers all 22k 16193 10 60 1 Phono 16102 (0.10 C519 Jack switched Mono 1664 10.20 macs Thyristors 1 C s and Levers ALL NED'. S5 6 Slider potentiometers all 4 /k I,n 16194 C514 Jack socket OPOT switch 1665 10.60 Car aenal 16103 10.16 10.32 ANO COOED Appro. 100 Pieces Offering , S6 b Slider porentiomerers all 4 lk by 16195 16104 CS 1 5 Car aerial 1666 10.60 e IV £0.16 '(0.10 majeur A lamest, bargain PAK I J. R,ghl 15105 0516 AC mains US type 1667 '60.16 angle lack 10.12 awny Identi6calinn and data sheeenormous t er CS 1 I Phot) 4 way 1568 Jack 2 5mm plash 15106 'E0.12 10.16 every pak lack stereo pionce 161117 10.20 CS18 OC power 1669 10.18 0519 AC switched 1670 ORDER NO 167 ?2 £2.25 Phono free , r enep 16108 '(0.14 '(0.32 CS20 Phono 8 way 1671 '(0.32 CERAMIC PAKS OC 21 plug 16109 10.12 C 2 5 m plug 16110 '£0.12 teint 10 mm,a lure oe one, .ape Conra,mng a range ul dual . 2 per ACp'uqn LI 5 '01 Ibtit 'E0.18 Unrepeatable value 1 AM a ,al 15111 '£0.13 Just a selection Irom Order No. Price Cassetic none., ua.. 16113 10.15 our huge storks' MCI 24 miniature cerame ,.apace ors . , ea,t I6114 '£0.13 value - 22p1 27pl 3311 39p1 4701 68p1 SEE OUR 16160 pep 82p, '£O.60 MC2 24 n ,a tu e cira n r capa ', ruts _ of each '1977 CATALOGUE value' - 00p1 20p) 15001 18001 INLINE SOCKETS 13011 2 /011 16161 126 22011 & 39011 '£0.60 No Price pages packed with MC3 24 mrnrature ceramic capac.lors 3 of each valuable Information value 470p1 561)p1 680p1 820p1 DIN ? oo 'E0.18 100001 1500p1 2200p1 & 330011 16162 '60.60 Postage and Packing add 25p unless VIN Ill 1674 '(0.17 ORDER 24 min, at ore ce me capacnurs 3 0l each NOW otherwise Shown Add extra for I VIN' 11 1675 10.18 value 470pv1 ra `6011 68001 82001 Jack 5mm 1676 10.08 armad Minimum order E1 00 1ó00p1 150001 72110pí & 3300p0 1615.1 '£0.60 ONLY 50p Jack au ue 5mm ib7/ 10.08 plus 157) p &p Jack no plan,, 16/8 10.14 Jack mono Chrome 1619 60.28 Jock siereo plash, I680 10.20 Jackstereo Chrome inn) 'E8.42 - Plu,uunened 1682 10 12 ORDERING V.A.T. 158.1 '10.22 Add 1215%, to prices Coax teley,smr, 1684 '10.40 1 Please word your orders 1 Coo. 5a,:k back 1685 .. Add 81/2 1, to marked * e not 2 p, AC week 101 OS 1681, 10.21 exactly as printed ' others excepting those PhnPhone, m:r,n, 1e8/ 'E012 forgetting to include our Bne k h, ha, k 'Pump 1688 10.24 %P.4/ff marked these are part number. r P.O. BOX 6, WARE . HERTS Zero SHOP 18 BALDOCK ST , WARE, HERTS. AT OPEN Q 1t F 30 Mon /Sat. Tel 61593

www.americanradiohistory.com Wireless World, April 1977 117

High quality modules for stereo, mono and K other audio equipment. PUSH -BUTTON

11 STEREO

Enjoy the quality of a magnetic cartridge with OUR PRICE ONLY,. your existing ceramic equipment using the new FM TUNER enabling M.P.A. 30, a high quality pre -amplifier magnetic cartridges to be, used where facilities Fitted with Phase Lock -loop Decoder ;exist for the use of ceramic cartridges only £20.45 It is provided with a standard DIN * FET Input Stage input socket for ease of connection The 450 Tuner provides instant program selection at the touch * VARI -CAP diode tuning Full instructions supplied. of a button ensuring accurate tuning of 4 pre -selected stations, * Switched AFC any of which may be altered as often as you choose, by simply * Multi turn pre -sets changing the settings of the pre -set controls. * LED Stereo Indicator Used with your existing audio equipment or with the BI -KITS Specification: Alternatively the PS12 can Typical STEREO 30 or the MK60 Kit etc. 3µ volts is together with the Sensitivity be used if no suitable supply available, Stereo separation 30db Transformer T538. required 20 -30v at tested and aligned. The unit is Supply The S450 is supplied fully built, 90 Ma max. POSTAGE & easily installed using the simple instructions supplied. PACKING STEREO PRE -AMPLIFIER Postage & Packing add 25p unless otherwise PA100 shown. Add extra for OUR PRICE airmail. Min. £1.00 £13.75 Frequency Response + 1db 20Hz inputs A top quality stereo pre -amplifier 20KHz. Sensitivity of 1 Tape Input 100mV into 100K ohms STEREO 30 and tone The control unit. six 2. Radio Tuner 100mV into pushbutton selector switch pro- 100K ohms COMPLETE AUDIO vides a choice of inputs together 3. Magnetic P.U. 3mV into with two really effective filters for 50K ohms high and low frequencies, plus tape P.U. Input equalises to R1AA curve with, 7+7 WATTS output. 1dB from 2011z to 20KHz AL R.M.S. Supply - 20-35V at 20mA. MK. 60 AUDIO KIT: Comprising Dimensions 2 x AL60's. 1 x SPM80. 1 x; 299mm x 89mm x NM P & P 45p BTM80. 1 x PA100. 1 front panel 35mm. and knobs. 1 Kit of parts to include AUDIO 2 0 30 on /off switch, neon indicator, stereo headphone sockets plus AMPLIFIER MODULES instruction booklet. COMPLETE The AL20 and AL30 units are £16.25 PRICE £29.55 plus 85p postage. similar in their appearance and in The Stereo 30 comprises a complete stereo their general specification. How- TEAK 60 AUDIO KIT: pre -amplifier, power amplifiers and power supply. This, ever, careful selection of the plastic Comprising with only the addition of a transformer or overwind will Teak veneered cabinet power devices has resulted in a produce a high quality audio unit suitable for use with a size 163/4"x111/2"x33/4", other range of powers from 5 to output wide range of inputs i.e. high quality ceramic pick -up, parts include aluminium chassis, 10 watts R.M.S. stereo tuner, stereo tape deck etc. Simple to install, p:u heatsink and front panel The versatility of their design of producing really first class results, this unit is brackét plus back panel makes them ideal for use in record capable with full instructions, black front panel knobs, and appropriate sockets players, tape recorders. stereo supplied main switch, fuse and fuse holder and universal etc. KIT PRICE £10.70 and cassette and car - amplifiers it to be installed in a record plus 85p in the home. mounting brackets enabling ATION: tridge tape players or the cabinet postage. SPECIFIC plinth. cabinets of your own construction Harmonic Distort ion Po =3 watts f =1KHz 02.5% available. Ideal for the beginner or the advanced Load Impedance 8 -16ohm Size: 75mm x 63mm x 25mm constructor who requires Hi -Fi performance with a in 30 Frequency response ±3dB Po =2 watts 50Hz 25Hz minimum of installation difficulty (can be installed mins). Sensitivity for Rated 0/P - Vs =25v. RL =8ohm f =1KHz 75mV.RMS TRANSFORMER £2.45 plus 62p p &p TEAK CASE £5.25 plus 62p p & p. AL20 5w R.M.S. £2.95 AL30 10w R.M.S. £3.25 NEW PA12 Stereo Pre- Amplifier completely redesigned for use with AL 20/30 Amplifier 25 Watts (RMS) NEW Modules. Features include on /off volume. AL Complete 60 and Treble controls. Balance, Bass * Max Heat Sink temp 90C * Frequency response, output. Frequency Response 20Hz -20kHz with tape 20Hz to 100KHz Distortion better than 0.1 at 1 KHz * * (-3dB). Bass and Treble range Supply voltage 15 -50v * Thermal Feedback * Latest 12dB. Input lmpedence 1 meg ohm. Design Improvements * Load - 3,4,8, or 16 ohms * Input Sensitivity 300m V. Supply Signal to noise ratio 80db Overall size 63mm. 105mm. requirements 24V .5mA. Size 152mm * x 84mm x 33mm. 13mm. Especially designed to a strict specification. Only the finest components have been used and the latest. Power supply for AL20/30, solid -state circuitry incorporated in this powerful little PA12, SA450 etc. amplifier which should satisfy the most critical A.F. ,enthusiast E4.35 PSi OUR PRICE`;>:;:;<: Input voltage 15 -20v A.C. Output voltage 22 -30v D.0 Stabilised Power Supply Type SPM80 Output current 800 mA Max. Size 60mm x 43mm x 26mm. £ 1.30 Transformer T538 £2.30' SPM80 is especially designed to power 2 of the ALSO Amplifiers, With the up to 15 watts (R.M.S.) per channel simultaneously. P.O. BOX 6, addition of the Mains Transformer BMT80, the unit will provide outputs of up to 1.5A at 35V. Size: 63mm. 1 05mm. 30mm. WARE, Incorporating short circuit protection. Transformer BMT80 HERTS. £2.60 + 62p postage £3.15 SHOP 18 BALDOCK ST., WARE, HERTS AT OPEN 9 to 5.30 Mon. /Sat. Tel. 61593

www.americanradiohistory.com 118 Wireless World, April 1977

MARCONI NOISE GENERATOR WE ARE BREAKING COMPUTERS TF987/1. UNIVAC /HONEYWELL /ICL 1900 etc. 4 Ranges 0 -5: 0 -10: 0-15 0 -30. Due to large purchases now priced at £15 ea. Boards, Power Supplies, Core Stores are available CALL AND SEE

COMPRESSOR /VACUUM PUMP TEKTRONIX OSCILLOSCOPE Type 561A Twin Cylinder opposed with Integral 1/2H P Complete with 3B1 Time Base & 50HZ Single Phase Motor Tested & Checked 3A1 Dual Trace 110 Volts models only £15 ea. Amplifier 1/2 H.P. Motor 110V £10 ea. £375 each

MARCONI TF675F WIDE THE HONEYWELL KEYTAPE UNIT is a multi-channel RANGE Keyboard to Magnetic Tape System recording Keyboard entered data on '/z" tape in 80 or 120 character records in PULSE GENERATOR a form easily usable as a computer input /output and verifier. 240 Volt operation. + / - variable outputs up to 50V. Optional delay. Small compact unit £18 ea. From the simple to understand electro mechanical / vacuum system to the +15 -15 +5 Power Supply and hinged wire wrapped card frame. the flexibility and reliability are outstanding. this coupled with the ease of interfacing to a VDU, Mini /Microcomputer, etc., make all the Honeywell Keytapes on offer very fine value. SPOOLS OF 1/2" MAG Honeywell Keytape Unit, checked, tested with Manual, £215 ea. As above but less data boards. Tested forward / backward tape movement and control, etc. Data entry / exit via read / write boards. TAPE £105 ea. APPROX. 2000ft Exactly as above but less keyboard and table. £80 ea. All units carriage paid. 50p ea. P &P f 1 ea KEYBOARDS also available at £20 each. Carr £2 50.

AVO VALVE TESTER CT160 TEKTRONIX OSCILLOSCOPE Type 506 "THE SUITCASE" Complete with 3B1 Time Base & Size approx. 15" wide x 10" high e 11" deep

Limited quantity £25 each. - 9A1 Dual Trace Amplifier £450 each.

TEKTRONIX OSCILLOSCOPE Type 585A with type 82 plug -in. £500. S.E. Labs Oscilloscope type 102 E220. RHODE & SCHWARZ GENERATOR 8N41022 300- 1000MHZ £185. MARCONI UHF-SHF Signal Generator Type TF1058 £80. R &S DIAGRAPH & GENERATOR 3- 300MHZ. Very nice condition £475. TEKTRONIX 181 Time Marker Generator £40. RHODE & SCHWARZ ADMITTANCE METER BN3511. As new £65. TELONIC Sweeper 0- 200MHZ £80. POLARAD RECEIVER FIM 1 Model -82. Complete -10GHZ £425. HEWLETT PACKARD Oscilloscope type 175 DC -50MHZ Double Beam £180 with delay TELONIC SWEEPER 2000 -1 with LA -1 M 20HZ -20KHZ £120. Other freq. available. amplifier £220. MARCONI OSCILLATOR TF1101 20HZ- 20KHZ. Nice condition. Special price E50. GENERAL RADIO PULSE SWEEP & Time Delay Generator type 13918 £120. MARCONI Wide Range Oscillator TF1370.. Freq. range 10HZ 10MHZ. to Sine Wave, ROYAL INVERTORS manufactured USA. 28V DC Input Output 1 t 5V AC 400HZ up to 1 0HZ to t 00KHZ. Square Wave. High outputs up to 31.6V. Fantastic value at £90 ea. 2KVA. Brand new Crated £12.50 ea. MARCONI Generator TF867. 15KHZ to 30MHZ £60 ea. MARCONI ADAPTOR TM6113 for TF2700: TF1313. TF868B £20 ea. SPECTRUM ANALYSER by NELSON Rog m AIRMEC 4 trace scope Type 279. ROSS. /of IEKTRONIx 561 60e, Large screen £120. Osulloscones £225. MARCONI TF142F DISTORTION FACTOR METER giving percentage distortion on a directly calibrated dial and includes all spurious components up to 30KHZ £32.50 ea. AVO TRANSISTOR ANALYSER CT446 E30 ea SOI.ARTRON CD1212 SB 40 meg £85. B24meg twice £120. Many other types MARCONI PORTABLE FREQUENCY METER TF1026/ 11. 100 to 160MHZ. Very fine available. condition. £27.50 ea )1191T í OSCILLOSCOPE. ouble beam DC -6MHZ £95 each DECCA NAVIGATOR DISPLAY UNIT. Very impressive. £12.50 ea. *TELEPHONES. Post Office style 746. Black or two-tone.grey £S: ea. Modern style - 706 Black or COURTENAY MAJOR Mk. 2. 250 Joules. 5 outputs. Can be combined - 1250 joules. two -tone grey £4.50 ea. P &P 75p ea. Old black style £1.50 ea. P &P 75p. No heads. £40 ea. TELEPHONE EXCHANGES. eg 1 5 -wag automatic (exchange only) from £95. MODERN FANS. /a x 41/4 MARCONI SIGNAL GENERATORS. TF801B from £140; TF801D from £190. Usually 4t x 11/2". 240 Volts. Superbly quiet. 6 Blades £4.50 ea. P &P available ex stock 75p MARCONI DEVIATION METER. TF791D £75 ea. PAPST model 240V available at £7.50 ea. P &P 75p. RHODE & SCHWARZ POWER METER. BNRD- BN2412/50 £50. PHOTOMULTIPLIER Type 931A E4 ea. P &P 75p. Other types available. MARCONI RF POWER METER. TF1020A/1 50 ohmn £65. *POTENTIOMETERS - All 5p ea, P &P extra. Metal bodied AB Linear. PCB Mount. Brand HEWLETT PACKARD 11 Channel Numerical Printer £30. New 10K, 100K ganged; 250K ganged, 100K ganged, concentric shafts. *BEEHIVE MARCONI 20MHZ SWEEP GENERATOR. TF1099 £45. TRIMMERS 3/30pf. Brand, New 10 off 40p P &P 15p; 100 off £3.50 P &P MARCONI DOUBLE PULSE GENERATOR. TF14Q0S with TM6600 /S £20. 75p; 500 off E15 P &P E1 25, 1,000 off £25 P &P £1 50 MARCONI TRAVELLING WAVE TUBE AMPLIFIE 1278. £15. LARGE RANGE ELECTROSTATIC VOLTMETERS. From 0 -300V 2" E3, to 20KV Max. I.C. TESTER by SCHLUMBERGER. Model TCL232 test 741: 709 etc. Dual in lines: General guide 5KV 31/2" £5. Thereafter £1 per KV. P &P 75p. flat packs or TO -s £65 each. VARIACS 240V input 0 -240V output 8A £18 ea., 20A £30 ea. Carr. E2.50. AIRMEC Generator type 304A. 50KHZ to 100MHZ. £120. E.M.T. TRANSFORMERS 20KV 2KVA E70 ea. Many other EHT transformers and EHT AIRMEC MODULATION METER 210 £130. Capacitors available. DON'T FORGET YOUR MANUALS. S A.E. with requirements. TUBE type DB7 /36- Replacement for Telequipment S31 £11 ea. P &P El 50. TELEQUIPM OSCILLOSCOPE. Type 532. Very goo ondition. Small. compact size 7 n 9 4in approx. Ideal for colour TV servicing. Superbly reliable. FANTASTIC IFOR THE VDU BUILDER. New stock of Large Rectangular Screen 30 x 20cm VALUE tube £85 ea Type M38 at the ridiculous price of £4 ea. And also still available the CME1 220, 24 15cm at £9 ea. Base connections for both tubes supplies. HILGER & WATTS SPECTROMETER H11-(7-0 £350. RHODE & SCHWAR2; 1tl1Ott5W51-t rower Meter £120. SEMICONDUCTORS - All at 5p ea.*. P &P extra. Guaranteed all full spec. devices. RHODE & SCHWARZ Tunable Indicating Amplifier Manufacturer's markings. UBM £75. BC147,BC158 TEKTRONIX 180A Time Marker Generator £60. 2N3707,BC107:BF197,BC327. 2N4403.BC172B. BC261B:BC251B. BC348B, BC1 71A 8, 2N3055RCA 50p ea. P &P 8p. 2N5879 with 2N5881 Motorola 150 Watt Corny. pair £2 pr. P &P 15p. PRICES OUR TOO HIGH? THEN MAKE US AN OFFER WE CAN CONSIDER *Linear Amp 709 25p ea. P &P 8p.

CREED 5 -LEVEL COMBINED PRINTER AND PERFORATOR CRATED £35 each CREED 5 -LEVEL CREED 7B PAPER TAPE READER £25 each TELEPRINTER CRATED £40 each SPECIAL OFFER CREED 7B TELEPRINTER LATE MODEL WITH PERFORATOR, £60 ea. FREE WITH ALL PURCHASES PLESSEY READER

Minimum Mail Order £2 Excess postage refunded Unless stated - please add £2.50 carriage to all units VALUE ADDED TAX not included in prices - Goods marked with *121/2% VAT, otherwise 8% Official Orders Welcomed. Gov. /Educational Depts., Authorities, etc., otherwise Cash with Order .1 Open 9 a m. to 5.30 p m., Mon to Sat. ILr x with Anneals IULFWI- A LTD ;:--,ì 7/9 AK T HUR ROAD, READING, BERKS. (rear Tech. College, King's Road). Tel. Reading 582605

www.americanradiohistory.com Wireless World, April 1977 119 Strobes,Tachos, Meters, Generators and TelecommunicationsTest Equipment

E.B. import and distribute NEW WIDE -RANGE high -grade products from World- renowned British MULTIMETER UM -11 & Overseas Manu- Features 38- colour -coded ranges facturers. with high input impedance. r7 NEW FUNCTION GENERATORS!

d.c. Volts,

1 50mV to 1500V f.s.d. at 100kO /V. a.c. Volts, 1.5V to 1500V f.s.d. at 31 .6k0 /v. d.c. Current, 10µA to 15A. a.c. Current 15A. Other star features include mirror- scale, G430 provides Sine -wave NEW PULSE GENERATOR rugged taut band suspension, dB scale, (0- 1OVrms) and Square -wave diode and fuse protection. Model 70 (illustrated above) with test -leads and (0 -20V p -p) from 6000, conti- Supplied complete nuously variable, via 4- position Compact, low -cost pulse and square -wave genera -or, leather arrying 0 -60dB, pushbutton operated featuring

- free -running. step attenuator. Frequency range ' P.R.F. 4Hz to 400kHz, gated or 39.50 also synch. 0/P. 1 Hz to 1 MHz. 0/P 10v peak from 500, See inside back Pulse width 1 uSec to 100mSec. cover for details Send for ICE ' Delay 1 uSec to 100mSec. of Super details of our . Pulse mark /space inversion. range of multi - metenl £95 complete range ' TTLiCMOS HI LO gating facility. £89 welMome- Add 8 °° VAT to all Products Division) Callers prices shown. ELECTRONIC BROKERS LIMITED (New Monday to Friday Carriage extra 49 -53 Pancras Road, London N W1 2ÁB. TeI:O1-837 7781 9 a.m. to 5 p.m. details on request -

WW-I03 FOR FURTHER DETAILS *************************************** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ** * * * What rnra * from * could you I ew! sanwat ask for? * -* * THE MULTIMETER TO * * ;, * MAKE YOUR TESTER * * OBSOLETE! We are confident * * SUU The fabulous LCD900 - -- * 'it you can't do better * * than to incorporate ALPS Panel Meters in your next project * incorporates a liquid * whether it be Original Equipment Manufacture, Educational or * crystal display only of the * the Replacement of an Existing Instrument * * hich the meter saowa ` T°:-_ri * is * * * SUPERB QUALITY AND SCALE PRODUCTION * switched. * * ATTRACTIVE MODERN STYLING * 7 DC voltage ranges ±1 -1000V * 4c * EX STOCK DELIVERY FOR STANDARD RANGES * at 50K S) /V , * O * * RAPID PROTOTYPE SERVICE * 5 AC voltage ranges 10 -1000V 1 i * * * PRODUCTION FOR SPECIAL REQUIREMENTS * at 10K 0/V /' ± O I * REASONABLE DELIVERY OF PRODUCTION QUANTITIES * 4 DC current ranges 0.3 -300mÁ * PRICE * 1 AC current range 3A 9c available as:- True VU METERS £58.25 * * DC MICROAMMETERS AC & DC VOLTMETERS * 4 resistance ranges 1K-1000K movement 1 7.5uÁ * AC & DC MILLIAMMETERS AC & DC AMMETERS * Basic (exc.1VATP) * * SERVO AUTOTESTERS:-A range **** * * * * ** * * * * * * * * * * * * *** * **** * * * ** of four types of instrument * Also shortly available the VS -100 ultra -safe industrial * tester. * to measure auto /mobile currents and * * For full details on these and 24 other standard instruments in * 4c voltages dwell angle engine speed, etc. - A the range contact. * Details from:- sanwa * * SERVO AND ELECTRONIC SALES LTD. * QUALITY ELECTRONICS LTD. * * Tel. LYDD 20252 * 24 High Street, Lydd, Kent TN29 9AJ * * 24 HIGH STREET, LYDD, KENT TN29 9AJ TLX 965265 * Tel. Lydd (0679) 20252, TLX 965265 * * 4-04 * * * * * * * * ** * * * * * * * * * * * ** * * * * * * * * * * * * * *4- **** *-4044 * * * * * * * * ** WW - 090 FOR FURTHER DETAILS WW -091 FOR FURTHER DETAILS

www.americanradiohistory.com 120 Wireless World, April 1977

TRANSFORMERS LOGIC OP /AMP POWER OAVENSET AUTO 2KVA continuously rated Tapped for any voltage from SUPPLIES B Davis Electronics. Limited quantity only. 5 -260v. on steps of 5v With an isolated winding of '0.5.1Ov at 81/2 amps this transformer is an extremely Type BL CPS 40 SPS 5 SPS 7W SPS 9111 Supply Card Form tally Matted tally nand iaif mated S useful buy Push -on connections Sue 8" a 51/4" x 61/2" torr 1011c IEEW A really robust lob. Bargain at E23.50. Carr E3 00 bpic op'esp. ,K ELE]I!ilJ 0,p volts 750VA continuously rated Tapped as above with 4.5/5.513l 4.5/60131 12/18 4.5/6.0131 CI1fi1p11f7E(1TS ET 0.5 -10v isolated winding of 5 amps Same connections Mops Max. 1.25 Z.0 0.5121 100 Size 41/2" a 3 41/4" Also bargain at RIpple "." £12.50. Can 141 0.5 as 815 0.1 00 315, 317, 364 EDGWARE ROAD, LONDON W2 L2 Regulsdea °. 0.02 002 8005 0.02 GRESHAM Price £14.00 E26.00 £28.00 E51.00 Pr, 10.0,200.220.240v Sec tapped Carr/p. 8 p. 60p EI.20 [1.20 [120 TEL: 01 -723 5667 & 01 -402 5580 03'1711- 32.33.34 -35 at 10 amps to give 24 useful Notes 111 Programmable Shops and mail order dept (mad to 364) open 9 to 6 Mon to Sat. me voltages £5.00 cart Et 00 121 Each rad 131 Zero volts TORROIDAL protection 141 Pk -Pk M /V All have stability of 10.000.1 Prices include VAT. Carr. /p. & p. quoted U.K. only Pro 15.0.210.240v. Sec 140v at 35m,a 31v at 500 current firngmrt re.eniranr and output impedance of 0 251! at 1r 00 KHz ACCESS & BARCLAY accepted. Minimum order £5 otherwise C.W.O For credit on approved accounts moac t . 10v at 1 9 amps Scr Sue 31/2" Ma x 11/2" invoicing costs necessitate minimum order of £20 [3.95 p & p 30p MINIATURE MINIATURE LAMPS Po 240V Sec 6v. at '/ amp Size 1 "c" x 11/2" x 11/4" PAPST MOTORS WI RELAYS Ideal as power Supply base for models, radios. cassettes Noted for their advanced design and superb R -," Octal base 2 C/0 6 amp contacts Following etc £1.50 ea p & p 20p 6 off El 00 ea. p & p 45p construction Rotating drecast outer body voltages 12V a c 48V d c 110 d c 230 V flywheel acts as and eliminates wow and pp'' ( a c all £1.25 each plus base 1Sp postage flutter 50 Hz AC operation Capacitor start tCG.7/ and packing 15p 11 -pin 3 C/O 6 amp A B C D E F G MODEL HSKZ 32 80 -6 12 220V Dual speed tape deck contacts, following voltages 115 a c. 48 1 Size Size motor 500/1000 rpm 12 mm drive shalt gives tape d 24 d c. all at £1.50 each. base 15p I ype , Oa I Volt Curr Type Dia 1 Volt /Curt. of 9 05 sec 131/4 7., ins PRESS speeds 53/19 cm: /sect plus 15p p. & p STOP A 3MM 5-6V 60 MA D 3MM 2.5V 360 MA respectively. a plus 1'4" Size apptoa 51/4" dia. 31" B 4MM 4V 250 MA 5.6 60 MA spindle £18.504p &p E1 10. CROUZET MOTOR 5,1 60 MA E 4MM 6V 200 MA MODEL RO 32 65 -4 Dual voltage 125. 250c Size 2'/." I2V40 MA 63200 MA 1 SCOOP PURCHASE trame 1 r p m o 33/4" plus' /." long a 5,15" dia spindle E12.50, p &p Shaded pole Open 5 230V 50HZ 1425 1i I2V100 MA 14V40 MA E1 10 Sias 21/4" s 24." x tik" deep plus h" long o 5/32" Three very useful motors. 14V 75 MA F 4MM 2 7V 60 MA MODEL HSZ 20 25.2 42v A magnificent motor spindle E3.50 plus p & p 62p CITENCO F H P reversible geared motor 220 240v 50 small 28V40 MA 12V160 MA I1'r" 2%" long x spindle Hz Size plus 3" 5/32" £5.95. 5MM 28V 40 MA 14V 80 MA 1 Ph cap start Cunt rating 0 2 amps. Gearing 144 1. p &p 45p SYLVANIA SWITCH G final drive 10 rpm Torque 14 5 Kg cm 5! 16" dia Small telephone lack type 6 or 24V IamioNGerei 10 for £2.50 shaft Brand new Fantastic value at £18.50. p & p Price Types A -F c4.00 for 25. 50 and upwards 13p each ACADEX MOTOR 50 for £ 11.00 Lt 50 Type G 45p each p & p 20p per order 'Shaded pole Open frame 230V 50 He Double ended 100 for £18.00 '/s HPP reversible geared motor 220,240v 50 Hz 1 Ph '5/32" dia spindle, each fi4" long ideal for fans Complete with magnet normally cap stoat cons rating Gearing 5.1 Final drove approa BENDIX MAGNETIC CLUTCH Plus 50p p & p 280 rpm -s/." dia shaft Very robust New £23.95, cart models, etc Size 174" 216" s 13/4" deep plus spindles closed amp vacuum led Superb example of Dozens of uses any quantity E3 00 E1.50 p & p 45p 1,4 "a h"dia electro- mechanics Main body in in Home, Farm. 1 10 HP reversible motor 240v 50 He CROYDON 230. two sections, coil section fixed Workshops & Lab 1 Ph cap start Cont rating. 1500 rpm ilia shalt 240V A.C. NIXIE TUBES i" with Rim sleeve. drive section SOLENOIDS Brand new Very useful motor indeed E17.50, cart rotating on outer perimeter. ITT GN4 Red Standard numerals 0 -9 Complete with L3 00 MAGNETIC ceramic base for PCB mounting 1 08" dia 1 38" high Uniting plate has 'sin ID bearing DEVICES LTD No 11 121 FANS Single unit 240v 50Hz Shaded pole morel olus Vi" base depth Inc pins Operating voltage 170v. DC concentric with main section and has 2016 pull for 50'*: duty. 11/2" 61/2" four element blade Good through flow of air. new 18 -tooth cog wheel Extremely travel. push or pull Shackle both min Complete data and connections supplied Brand Hemember last Keep cool this year p & summer £3.95, powerful transmission 24V D/C ends Size 11/4" wide a 31" high £1.50. p &p 20p 10 off E100 each 100 or more 85p motors p 65p Dual unit in frame Two same as above but m. x 4" long plus 3" arm travel each. p & p 40p any quantity 240 a. £3.75 plus p & p with 61/2" five element blades Overall size 221/2" It 14" 40p E6.75 plus &p E100. 51/2" deep Extremely powerful air flow. Bargain at only (No 21 has 21b pull continuously PROGRAMME TIMERS £12.50, cart E2 50 rated ' travel Size 1' h" x PLESSEY 2 bank pole rotary stud JABSCO ROTARY PUMP Magnetic Ltd. motor :31 30 way single 1' "h x 21/4" plus travel £1.80. Devices Synchronous 230V 500, ITT Self priming and portable 1/4" shaft Powered / switch Contacts 1 amp 240v AC DC. 005.' res Break drive geared down to 1 rev per 8 hours. Drives shaft mounting 30pP &p before make for by a suitable electric drill or motor Normal " hose three cams. each of which actuates an on /off Stop infinitely adjustable allowing any desired a of travel Ideal for instrument and model fitting Capacity 2 3 galls per min at 2400 rpm motor PYE ETHER LTD. Thrust operates through spring loaded micro- switch with 10 amp Eonlacts Any switch can be set switching rc & 20p. 5 off Cl 95 ea. p & p speed Stainless steel shaft. Oil resistant impeller hinged lever going a 11b pull or push Complete with to remain on from 4 to 8 firs Push.on connections Overall £2.25 p p 40p Chemically resistant phenolic body Suitable for mild mounting bracket and push -on connections Size overall size 41/2" x 41/2" x 311" E4.75 plus 85p p & p ideal for 141 POST u chemicals cal water Ideal tit home for filling tanks ow bracket 21/2"w x 3'n a 3'1" long E2.25 p & p switchong on and off radios and lights OFFICE type -selector Split 30 way as burglar deterrent clearing sinks drains, washing machines. in industry for 45p in unoccupied premises. double bank contacts 240v n AC or DC coil Overall size appro. 2'4" dra. 2'/" deep. £4.50. p & p 65p drums. carboys. drain sumps and handling chemicals. on Smiths 200/250V. synchronous motor geared down to r transfer tat lertrlrsers. etc n boats for bilge 151 GOODYEAR 1KVa au transformer 40 r p m Sian 21/2" a 21/4" s 1'h" E2.25 each plus 25p clean-up balling dinghies and changing engine oil No ARROW SWITCH 0 -110- 115 -120- 200.220.240u to Fully shrouded p & p 4 or mom £1.50 each plus 70p p & p per pack piace should be without one It uses are endless and price Press on off Single hole I,.rng Terminal block connections Sue 5" 41/4" ' plus of 4 a giveaway E2.75 plus 20p p & p SP/ ST Size 11/4" 'n" Stud block cannot be bettered at £13.95, p & p El 50 Mrdgley Harmer Ltd 200/250V synchronous motor 161 REED SWITCHES glass encaps N o ontacis Glass extends 'z " Rated 1 amp at PCB EDGE CONNECTOR geared to 1 rev 71/2 per mins Ail dimensions 2'4" iengrh 1 V Ma , overall length 1'ßs " c 10 off L1 240v 2'hi amps al.125v Price ". ' ". 00, CINCH 15" pitch 27 way but designed with adjustable £1.50 each plus 25p p & p 4 or more E1.00 each plus p & p 25p 100 off E8.00, p & p free 1000 off in for 5 pen qty 1 E1.75 P & p fixing endplates enabling connector to be cut and used free 30p 10 or more 30p each p & p 48p p & p per pack of 4 £98.00, p & p any length desired 50p p & p 15p 10 all E4 00 p & p 40p WW - 101 FOR FURTHER DETAILS 30p

TF 8019/2. Spec as for 801D but minor circuit MARCONI dillerences Few only left £150 carriage E5 00 TF 867 PLEASE NOTE VIM SIGNAL FREQUENCY ANALYSER D-669 -A. Unless offered as as seen GENERATOR Frequency range 30c c-30kc s rn 6 ranges Range 15KM: to Amplitude stability n 1db over a period input 30MHz Output impedance 100k ohm shunted by BOpF ALL EQUIPMENT 0.4 V to 4V at 13 selectivity normally set for Q =50 '.variable from 1 ordered from us Is completely or 75 ohms rope to 1501 £120.00 carriage E 10 00 with terrain overhauled mechanically and elec- mon Isupplred SINGER PANORAMIC SPECTRUM ANALYSER TYPE trically in our own laboratories le, Built in ysiti SPA 10 Frequency range 10MHZ.6Ht Full i Aely heck l r with spec and pace on TF 995A/1 or A/2 or A /2M or A5 SIGNAL - handbook, £138 request _ GENERATORS. Very high class AM FM 1 5MHz to i clutling carriage TF 1041 B VALVE MULTIMETER. General purpose 220MO, Detailed spec and pace on applicator measuring DC voltage Iront 300mV to 1.000V AC PHILIPS AUDIO TF 801D /1 /S SIGNAL GENERATOR. Range GENERATOR TYPE OM 2308. voltage room 30OmV to 300V at up to 1 000MHe and 11 10-485MHz in 5 ranges R F output 0 1 V -1V l6kc s Attenuator 0 0001 O 0003. 0 001 ro 1 resistance up to 500Mohms Price £59 carriage BOONTON with output asym & sum and matching impedance 5 Source C M Dial calibrated on volts decibels and 1300 power relative to thermal noise Piston type attenuator 250 600 & 1 000 ohms Price £98.00 carriage TF 1370 R.C. OSCILLATOR FOR SQUARE A SINE AM /FM SIGNAL GENERATOR. impedance Internal modulation 1 1 00 50íI output at KHz at WAVE. Freq -316V rms 10H,- 1MHz square wave. TYPE 202E & 202H. 54- 216MHz up to 90 depth also external sine and pulse 0 73 2pp. 1OHz 100kHr Attenuator range -50dB to modulation Built in 5MHz crystal calibrator Separate in 2 ranges £275.00. E.H RESEARCH LABORATORIES n IOdB impedance 75 100 605)) £145 carnage RF and mod meters P O A INC. MODEL 15 00 SIGNAL GENERATOR TS. 133A PULSE GENERATOR. Features Ultralin- MUIRHEAD TF 6600 SECONDARY PULoe UNIT for testing 497 /URS 2 -SMz, 13MHz, r radatl nucleonics scopes counters filters. rise and fall independently variable PAMETRADA WAVE ANALYSER TYPE etc 30MHz, 78MHz, 180MHz, 50v ra output into 50 ohms. polarity TF 455E WAVE ANALYSER. Freq range 20 c s to either D- 489 -G. Freq range 19 c- s21 Kc s Automatic 16 kc: s double crystal filter yeses 4 c s pass band 400MHz. 0 .1 v -1 fiv carriage overload protection Synchronous conttnuously variable in nine ranges 19-90 c s £150 gating all solid state Full specification on request Envelope distortion test on I inputs up to 400 Mc s 79.150 co s, 13210 c s Ir 1 x 10 a 100, £3.00. £275.00 £98.00. packing & carriage Lb 00 Freq a acy a 1 and e 10 ranges ± 0 3'x. RADIOMETER TYPE MS111 SIGNAL Input voltage for full scale deflection of meter 1 CT439, CT478, CT479 UHF SIGNAL GENERA- MODEL 122 GENERATOR GENERATOR. High qualify Danish production mV minimum to 300V maximum Maximum TORS. For tuning various types of radar eiluipmenr Features Rep rates to 200MHz. Nanosecond 10kHa 110MHz E200 carriage E5 00 input is r m s P 0 A Switching times, synchronous gating Pulsetop permissible 300V REDIFON 559 TRANSISTORISED TRANS- ANCILLARY EQUIPMENT: D -825 -A LOW CT480 SIGNAL GENERATOR. 7 KMC S to 12 baseline inversion. plus offset all solid state Full CEIVER OR410. 2 -16 c s 200 250V 4 channels FREQ. MODULATOR. Freq range 2 c1/4-20 KMC S mod C W F M Pulse E180 carriage 15 00 specification on request £295.00 100W p c p s :down to t c when analyser is used in TRIGGERED VACUUM SPARK GAP TYPE ZR c High 0 I Freq accuracy ' 0 1 co s :providing TEKTRONIX OSCILLOSCOPES MAIN 7512. Capable of swnchlny 15 000 joules at 45KV RHODE & SCHWARZ supply Ireq is first measuredi Specification on FRAME ONLY 535A. Bandwidth DC to IhMHz [50.00 carriage 12 00 Z-g DIAGRAPH TYPE ZDU 30- 420MHz. 5012 request Price £275.00, packing and carriage at 3.113 depending on plug -in unit Specification LOW RESISTANCE HEADPHONES TYPE CLR Directly measures multrtermmal networks phrase E4 00 and price on request E1.50. 40p postage VAT 12- -

shift . phrase angle with complimentary POWER DECADE OSCILLATOR D- 890 -A. This 545A. Bandwidth DC to 30MHz 13dB down at ARSE D A LF SPARES. We ni,d p.e largest stock n SIGNAL GENERATOR TYPE SMLM high Ireq oscillator which has been adapted for use by 30MHz. ± '::d8 depending on plugm unit UK write for list resolution. internal external mod up to 3v out NATO has the same frequency range Specification and price on request RF METERS. 0 to 8 amps 21/4" USA, brand mW FREQUENCY SYNTHESIZER TYPE XUA. ß,1c s -110kc sr as the widely known D.650-B 551. 27MHa DUAL BEAM OSCILLOSCOPE. E1.50 P &P 25p 300, -30MHz with FREQUENCY INDICATOR oscillator which it supersedes Frequency Accepts multi -Irate differential Sampling and TELEPHONE TYPE "J" tropcalrsed TYPE FKM 15- 30MHZ. 30.100MHz accuracy without crystal check facility. X1. range spectrum analyser plug -in units Specification and 10 LINE MAGNETO SWITCHBOARDS n 0 2, or in 0 2c s whichever is greater. X10 price on request 50 LINE AUTOMATIC PRIVATE TELEPHONE ± HEWLETT -PACKARD range 0.4e, (above 10kc. so Maximum output PLUG -IN UNIT TYPE CA. For smote or SWITCHBOARDS BK ohms load. 126V 12 watts, 20c s -SOkc s. LAYING APPARATUS No 11. New AUDIO MODEL 208 -A. dial -trace operation each channel has its own CABLE GENERATOR 90V -1 Watt, 20c s- 110kc -s input selector attenuator, gain polarity Price Production P 0 A load ',1 1 Freq. 20c to 20,000c. matching 600 ohm 25V warn 300c, s- 10k s £65.00. packing & carriage Em 1 . impedance 50. 150. 600 ohms. Price 17V 10 5 wato at 200 c s decreasrny to 5V FOR EXPORT ONLY WAYNE KERR NOISE GENERATOR CT 410 140mW, at 60 c s Full spec un request RCA ET4336, 2 Mc s -20Mr s 350W o1/40 £85.00 carriage £4 00 A instrument form e mg noise £249.00 carriage LTO 00 portable the factor of wd,lied version of increased output to 700W radio receiving equipment metric radar receivers and 4 KAHN SSE ADAPTOR TYPE 5588 62 18. H.F. Made b Collins 231D 5 kW. 3 MHz -24 MHz 10 SIGNAL GENERATOR TYPE 201. radar r I mplil ers the band - - wrdeband channel Auto u manual tuning for IF at - - Designed recewers with 455 500KHz 100mV Airmen Constant output revel within 0 5 dB 15kH t 60MHz Output impedance 50 or 75 ohms A max, input Features 53 Transmitter electronic AFC carrier Ireq over entire frequency range Freq 30kHz to 30MHz in built rr audio power meter lias e switched input circuit diversity to combat fading 20 sce R C memory to 7bands 62 Transceivers Stability better than 0 005 amplitude giving m 15 impedances of 10. 6.000 and 20.000 olrrns Mallard C11. high power installation 1000N/r maintain tuning during severe fading Individual carrier modulation continuously v cable 0-100 Maximum and has a basic range of 115W / 1W -20db tu meters. vishers. IOW ptoducimn IR4F high output is ai r m s Pore PAC distortion approx9V £65 -k 30db lu 1 WI Price E85 carriag.. _5 00 Technical details est demodulator £65 courage E5 00 VIBRATION /DISPLACEMENT METER TYPE B HR 23 TRIPLE DIVERSITY SSE RECEIVERS. Freq MODULATION METER TYPE 210. AM FM Fro 731 A with lour prober Full spec un request 3- 275MHz V F O at 6 Xtal positions Recephon of range 3MHz- 300MHz In 7 ranges Pocc E75. P &C 114 E195.00. independent single or double side band transceivers LEVEL OSCILLATORS made by SIEMENS. 3 types COLOMOR (ELECTRONICS ITD.) Full spec on application E350 carriage L35 00 available 1 0 3 to t 200kHz. 2 1 OkHz tu 1 /MHz. 3 SOLARTRON RACAL RECEIVER MODEL RA1l7. In full working 0 3 to 1600kH, Prices on requesi DIGITAL VOLTMETER. LM 1426 LM 1420 2BA. 170 Gm k Rd.. London. W.12 order and restored condition P 0 A TF 9M DEVIATION METER. 250MHz £55 carriage LM1420 LM14403 RA98A Adaptor lui above £85 1300 Tel. 01 -743 0899 VAT FOR TEST EQUIPMENT PLEASE SEND STAMP WITH 1_500/250 MEDIUM WAVE BROADCAST Open Monday to Friday 'TRANSMITTERS. Export 01 'IV Pc, P tai Id (letali, 8% PLEASE ADD 8% J ENQUIRIES on application 9- 12.30. 1.30 -5.30 p.m.

www.americanradiohistory.com Wireless World, April 1977 121

SINTEL for PCBs - KITS - CASES - MPUs - BOOKS - MEMORIES Ieadingnlanulacturersonly by return with details of HIGH QUALITY A FREE CATALOGUE requested by post or phone will be sent our range of CASES BOOKS DISPLAYS MPUs MPU KITS MEMORIES and CCK KITS other components not listed here with same day despatch for goods in stock CRYSTAL CONTROLLED 6 DIGIT CAR CLOCK WITH INDEPENDENT JOURNEY- TIMER. Shows ,me for Start -Stop -Reset or elapsed time in hrs mans s Runs off car 12v supply Nine push buttons MEMORIES M.l erring rtislilay U, show time ore elapsed time All controls functional irrespective of display mode Kit compele with case Order as CCK. E38.00 TTL COMPATIBLE STATIC RAMS ACK 6 digit Alarm Clock with touch switch snooze. Order as ACK E26.80 4K STATIC RAM Crystal control and battery back -up can be added later, or if bought with the kit 9131

. . Mitanasaa Order as ACK +BBK +XTK .. .. E33.58 1024.4 bit 500nsec Access time Single 5v supply 1 20imA rte. cuirem cunsumynun pin OIL package OCK Attractive 4 digit clock with green displays. Order as OCK E14.40 wires berwe,,i wiring up a 1024 x 8 bast memory board. using the 9131 reduces the no,o her ul Also available with Crystal control and Battery back'' -up. Order as When ICs about 100 to about 18 OCK +OBBK +XTK E19.65 memory from E19.50 Order as 9131 THE SINTEL CAR CLOCK KIT. Order as AUT-CK .. E17.85 Also available less case. Order as AUT- MODULE KIT E16.45 2102A-6 21 1 6505 1 4 1024 111111111111111111 5014: CRYSTAL TIMEBASE KIT. Provides accurate and stable 50 pulses per 1024 x bit 256.2A4 dit CMOS sec for clocks and other timing applications Order as XTK ... E6.28 65Unsec 650nsec bOOnsec Order as Oidet as Order a s 2102A-6 E351 2112A-4 E4.76 6508 E8.05 CMOS AND OTHER COMPONENTS CD4036 3.65 CD4076 1.61 CLOCK CHIPS MPU. C04000 0.17 IM6100CCD1 45.36 CD4001 0.18 CD4037 1.09 CD4077 0.60 AY51202 2.89 CD4038 1.24 CD4078 0.24 AY5t224 3.50 8080 12:5) 32.25 L04007 0.17 33.87 USEFUL PRINTED CIRCUIT BOARDS r'D4006 1.35 CD4039 3.55 CD4081 0.24 MK50253 5.60 MC6800 SC /MP '.-:D4007 0.18 C04040 1.23 004082 0.24 FLAT CABLE Ader as Description !SPA/ 500 18.75 COUNTER PCB SETS L 1.11 CD4041 0.96 CD4085 0.82 20w 1m 1.00 0400 and ICs loi building a b digit. 4 digit or 2 digit C04009 0.64 CD4042 0.96 CD4086 0.82 10m for 8.00 2650 E27.50 Sets of PCBs to hold displays all the COUNTER MODULE WITH LATCH USING TTL The PCBs hold one each per digit of r 04010 0.64 C04043 1.16 CD4089 1.78 VEROCASES KITS MPU TI1321. 7447. 7475 and 7490 as well as Rs and Cs Each set consists of one vertical PCB C04011 0.20 CD4044 1.07 CD4093 0.92 751410J 3.36 MEK6800DI 137.00 751411D 3.77 which holds the displays and is fastened to a horizontal board which holds the remaining CD4012 0.19 C04045 1.61 CD4094 2.15 INTRO KIT from us order these 751237J 2.15 components (of these components. only the TIL321s are available - th CD4013 0.64 C04046 1.53 CD4095 1.20 ISPBK /200E 93.55 751238D 3.00 CD4014 1.16 C0404 7 1.04 CD4096 1.20 MCS 80 176.65 6 Site h 30mm w 173mm d 109mm E5.50 CD4015 1.16 C04048 0.64 CD4097 4.28 751239K 3.58 610 -950 digit Sel 4 h.30mm w 126mm d 109mm E3.95 CD4016 0.64 CD4049 0.64 CD4098 1.26 DISPLAYS TRANSFORMERS 246 -950 digit Set Size 2 digit Set Size h 30mm w 80mm d 109mm ' E2.30 CD4017 1.16 CD4050 0.64 CD4099 2.11 FND500 1.02 I.EDTRF 1.95 915 -950 111.321 1.30 CD4018 1.16 CD4051 1.07 CD4502 1.43 SLTRF 1.95 610 -950 C04052 1.07 CD4510 1.57 T11322 1.20 CD4019 0.84 HOLDING PCB. NON -MULTIPLEXED CD4020 1.28 CD4053 1.07 CD4511 1.80 XAN652 2.45 CRYSTALS DISPLAY XAN654 2.45 876 -001 6 digit counter format for FND500: TIL321 11L322 £0.75 CD4021 1.16 CD4054 1.33 CD4514 3.15 32 768kHz 4.50 FND500 TIL321 TIL322 E0.55 5LT01 5.80 675-001 4 digit counter format for CD4022 1.11 CD4055 1.51 CD4515 3.60 5 12MHe 3.60 472 -001 2 digit counter format for F5D500. TIL321 : TIL322 E0.29 Atir 1.51 C04516 1.56 SOLDERCON CD4023 0.24 CD4056 246 -950 C04024 0.89 C04059 5.48 CD4518 1.25 IC PINS SUNDRIES DISPLAY PCB. WIRED FOR MULTIPLEXING 0.50 CD4025 0.24 CD4060 1.28 CD4520 1.43 100 CA3130 1.14 D500 -6 6 digit clock format for FN0500 /TIL32 t I TIL322 E1.35 074026 1.98 C04063 1.26 C04527 1.82 1000 4.00 µ4741 I8 DILL 0.35 06526 6 digit clock format for XAN652/ %4N654 E1.35 1.65 10.000 34.00 78L12WC D 500-4 4 digit clock format for FND500/ TIL321 / TIL322 £0.90 C04077 0.64 CD4066 0.71 CD4532 0.77 forinar for FND500 /TIL321 ! T11322 E1.35 1.04 O 6004 8 digit counter CD4028 1.03 CD4067 4.28 CD4555 915 -950 CD4029 1.31 CD4068 0.24 CD4556 1.04 1.22 NEW DATA FROM SINTEL CD4030 0.64 CD4069 0.24 MC14528 Motorola MIMOS Databook CD4070 0.67 MC14553 4.88 CD4031 2.55 Nol 5 Ser les COUNTER KIT CD4032 1.23 CD4071 0.24 IM6508 8.05 TMS 8080 Microprocessor Detasheet 0.75 142 -269 A complete kit for building a 2 digit. single PCB. CMOS COUNTER MODULE WITH LATCH 1 x CD4033 1.60 CD4072 0.24 Includes PCB 912 -950. 2 n TIL322 or F50500. 2 a 5 4511. R's. 4518. socket TMS5501 (Multifunction I/O Eá.60 CD4034 2.19 CD4073 0.24 Controller for 8080) Datesheet 0.75 Ins. etc Size h 67mm w 71mm d 18mm 61.05 CD4035 1.35 CD4075 0.24 - 912 -950 Single PCB only as used in 142.269 COUNTER KIT above

ORDERS Add VAT at 8% + 25p p &p. Phone orders see 'FAST SERVICE.' Export Property, 209 Cowley Road, Oxford, but please do not use this as Our offices are at Link orders welcome. No VAT but add 10% (Europe). 15% (Overseas) for Air Mail p &p. For a postal address. export postage rates on heavy Items - contact us first. m 4.15 p.m (Mon. -Fri.) will be FAST SERVICE We guarantee that Telephone Orders for goods stock, received by SINTEL despatched the same day by 1st Class Post (some heavy items by parcel post). and our stocking is good. Private SEND YOUR customers should telephone and pay by giving their Access or Barclaycard number. with a minimum order value of E5. ORDER TO P.O. BOX 75C, OXFORD v Official orders, no minimum Tel. 0865 49791 SINTEL

A. Marshall (London) Ltd Dept: WW 40 -42 Cricklewood Broadway, London NW2 3ET 9aeatdeaoteug Tel: 01 -452 0161/2 Telex: 21492 94'a & 85 West Regent St Glasgow G2 2QD Tel: 041 -332 4133 & 1 Straits Parade Fishponds Bristol BS16 2LX Tel: 0272 654201/2 Call in and see us 9 -5.30 Mon -Fri 9 -5.00 Sat Trade and export enquiries welcome. Please enquire for types not listed NEW 168 PAGE CATALOGUE WITH 500 NEW LINES 55p Marshall's post paid (40p to callers)

POPULAR SEMICONDUCTORS (A very small selection from Our range covers over 7,000 items. The largest selection our vast stocks, please enquire about devices not listed.) in Britain. Top 200 ICs. TTL, CMOS & Linears .3696 0.35 253053 0.30 254058 0.20 AC126 M37 BC149 0.13 i4JÉ3055 0.85 25697 0.30 253054 0.50 254060 0.20 AC127 0.44 BC153 0.27 MPF111 0.35 CA30204 2.29 iM38:'N 1.25 NE 556 1.05 IAAS5U 1.60 TCA280A 1.30 THYRISTORS 25698 0.62 253055 0.70 254061 0.17 AC128 0.37 BC157 0.12 MPT8111 0.35 CA3028A 1.01 LM3845 1.45 NE565 1.30 TAA570 2.30 TCA290A 3.13 Plastic '2N699 0.55 253390 025 254062 0.18 AC151 035 BC158 0.11 MP5U56 0.60 CA30286 1.29 1M396N 0.80 NE566 1.65 744611B 1.85 TC44204 1.84 54 100V 0.35 2N706 0.24 253391 025 254126 0.17 AC 152 0.50 BC159 0.11 TIP29A 0.45 CA3030 1.24 LM387N 1.05 NE567 1.80 TAA621 2.15 TCA730 3.22 6A 200V 040 257064 0.12 '2533916 0.25 254289 0.20 AC153 0.49 BC160 0.50 ITIP42C 0.95 CA3036 0.97 LM388N 1.00 SAS560 TAA6618 1.32 TCA740 2.76 .54 400V 0.49 25708 0.21 253392 0.16 254919 0.55 AC53K 0.56 BC16t 0.50 TIP2955 0.65 CA3045 1.40 LM3895 1.00 SAS570 TAA700 3.91 TC4750 130 84 100V 0.43 25718 0.27 2N3393 0.15 254921 0.50 AC170 0.40 BC167 0.12 TIP3055 0.85 CA3046 0.89 LM702C 0.75 5042P TAA9304 150 TCA760 1.38 OR 200V 0.49 2N718A 0.50 253394 0.15 254922 0.56 AC176K 0.60 BC168 0.12 TIS43 0.40 CA3048 2.23 tM709C 0.65 760015 1.57 1A493013 1.06 TC4800 3.13 BA 400V 0.62 25914 0.35 253439 0.88 254923 0.70 AC187K 0.55 BC169 0.12 CA3049 156 LM709N 0.45 76003N 2.55 TAD100 1.95 U44170 2.00 BRIDGE 25916 0.30 253440 0.64 255191 0.70 AC188K 0.55 BC170 0.16 CA3052 1.62 LM Sub Miniature 710C 0.60 76008K 2.50 TB4120 0.65 U44180 2.00 RECTIFIERS 25918 0.38 253441 0.85 255195 0.90 ÁD161 0.85 BC171 0.14 CA3053 0.60 LM710N Toggle. 060 760135 1.70 784400 1.50 CD4000 0.20 05005 0.30 25929 0.25 253442 1.35 255245 0.35 ÁD162 085 BC172 0.12 CA3080 0.68 LM723C 0.56 76013ND 1.57 TBA500 2.21 1PON 0.80 C04001 0.20 Vv01 0.33 25930 0.28 253638 0.16 255294 0.40 ÁF106 0.55 BC177 0.20 CA30804 158 LM723N 0.75 76018(C 150 TBA5000 2.30 CD4002 0.20 251131 0.60 2N36384 0.16 255295 0.40 ÁF109 0.75 BC178 0.20 SPDT 066 WO2 0.34 PPDT CA3086 0.51 LM741C 0.65 76023N 1.70 784510 2.21 CD4006 1.10 W04 040 251132 0.60 2N3641 0.20 2N5296 0.40 ÁF124 0.65 BC179 0.23 CA3088 1.59 LM741N 0.50 76023ND 1.57 TBA5100 2.30 CD4007 0.20 251613 0.35 253702 0.17 255298 0.40 ÁF125 0.65 BC182 0.11 C /OF1 0.50 2.52 W06 0.50 CA3089 LM741 -8 0.40 760335 2.55 784520 2.21 CD4008 0.97 BY164 0.57 251711 0.37 253703 016 255447 0.15 ÁF126 0.65 BC183 0.11 CA3090 3.80 LM747N 0.90 761105 1.46 TBA520Q 2.30 CD4009 0.57 84001500 048 251893 0.30 253704 015 255448 0.15 ÁP127 065 BC184 0.12 CA3130 094 1M748-8 0.50 76115N 1.87 TBA530 1.98 CD4010 0.67 134003200 252102 0.60 253705 0.15 255449 0.19 ÁF139 0.69. 13C1841 0.14 LM3014 1.10 P11(1) to 255 0.65 LM7485 0.90 76116N 106 TBA5300 2.07 CD4011 0.20 68001500 0.76 252218 0.33 253706 0.18 255457 0.22 ÁF200 0.70 BC207 0.12 LM30113 0.44 1.76 76131N 1.30 TBA540 2.21 (E3) Linear or .M1800 CD4012 0.20 88003200 1.16 2522184 0.37 253707 0.18 255458 033 ÁF239 0.74 BC208 0.11 LM304 2.45 LM1808 1.92 76226N 1.94 TBA540Q 2.30 CD4013 0.57 252219 0.30 253708 0.16 255459 0.26 ÁF240 0.98 8C212 0.14 Log LM3075 0.65 LM1828 1.75 762275 1.51 TBA550 3.13 CD4014 1.01 OPTO -ELEC- 2522194 0.32 253709 018 255484 0.34 ÁF279 0.80 BC213 0.14 LM3085 1.17 LM3301N 0.85 762285 1.75 TBA5500 3.22 CD4015 1.01 TRONICS 252220 0.35 2133710 0.16 255486 0.38 AF280 0.85 13C2131 0.16 Rotary LM309K 110 LM3302N 1.40 76530N 0.91 1845600 3.22 CD4016 0.56 LEDs 252221 0.22 253711 0.18 256027 0.53 BC107 0.15 BC214 0.18 Single 25p LM317K 3.00 1M34015 0.70 76532N 1.50 TBA570 1.29 CD4017 1.01 3mm Red 0.18 2522214 0.26 2N3713 2.30 256101 065 BC168 0.15 BC214L 0.17 . Double 7Sp LM318N 2.25 LM3900 0.75 765335 1.30 TBA570Q 1.38 DIL 5mm Red 0.20 252222 0.25 253714 2.45 256107 0.42 BC109 0.15 60237 0.14 Switched LM323K 6.40 LM3905 1.60 76544N 1.44 TBA641Q 2.50 SOCKETS 3mm Grn 0.25 2N2222A 0.25 253715 2.55 256109 0.42 BC113 0.17' BC238 0.12 Single 66p LM339N 1.75 I M3909 0.68 76545N 2.09 TBA651 1.80 8 Pun 0.15 5mm Grn 0.26 252368 0.25 253716 2.80 256121 0.38 BC115 0.19 60239 0.15 Single LM34813 1.91 MC1035 1.75 76546N 1.44 TBA700 1.52 14 Pin 0.16 3mm gel 0.25 252369 0.25 253771 1.55 256122 041 BC116 0.19 BC251 0.15 Slider -45p LM3605 2.75 MC1303 1.47 76550N 0.41 TBA7000 1.61 16 Pin 0.18 berm Yel 0.26 2523694 0.25 253772 2.00 256123 0.43 BC117 0.22 8C253 0.22 Double LM370N 100 MC1305 1.85 765525 0.65 TBA7200 2.30 22 Pin 0.30 0.75 256126 0.45 BC11B 0.16 BC257A 0.17 Slider 76p SC /MP 252646 253773 2.90 LM371N 2.25 MC1306 1.00 765705 2.08 T8A750 1.98 24 Pin 0.35 252904 0.36 40361 0.45 BC121 0.45 BC25913 0.18. Irmo Kit 6851 253789 2.90 LM372N 2.15 MC1310 1.91 76620N 1.10 TBA750Q 2.07 28 Pin 0.45 2529044 0.37 253790 3.10 40362 0.48 BC132 0.30 BD131 0.51 LM3735 225 MC1312 1.98 76650N 1.10 TBA800 1.20 40 Pin 0.55 KEYBOARD 252905 0.37 253791 3.10 40363 1.20 BC134 0.15 BD135 0.37 A comprehensive LM374N 2.25 MC1327 1.54 76660N 0.60 T84810 1.16 TRIACS KIT E65.84 2N29054 0.28 253794 0.20 40406 0.58 BC135 0.15 BD139 0.40 range of Capaci LM3775 1.75 MC1330 0.92 76666N 0.92 TBA820 1.03 Plastic 2101.2 4.14 252906 0.28 253819 0.36 40407 045 BC136 0.19 BO140 0.40 tors and Resis LM3785 2.25 MC1350 0.75 TM3104 1.50 784920 1.79 44 400V 0.70 2102.2 2.90 2N2906A 0.25 253820 0.38 40408 0.65 BC140 0.40 BD529 0.42 tors always LM379S 3.95 MC1351 1.20 TAA3204 1.15 T849200 2.99 6A 400V 0.75 21112 4.14 252907 0.21 253823 0.75 40409 0.65 BC141 0.45 8E160 0.30 stock plus man., LM380.8 0.90 MC1352 0.97 TAA3504 2.48 184940 1.62 84 400V 0.80 2112-2 4.14 2N2907A 0.22 253904 0.21 40410 0.65 BC 142 0.30 BF184 038. other compor LM380N 0.98 MC1357 1.45 TAA521 1.00 TC4160C 1.85 10A 400V 0.90 2513 8.00 252924 0.15 253906 022 40411 2.85 BC143 0.30 8E459 045 tits I.M1814 2.45 MC1458 091 T4A522 1.90 TC41606 1.61 124 400V1.10 MM5204 32.30 252926 0.12 254036 0.67 40595 0.56 BCt47 0.12 80105 1.50 Over 8.000 tin, - ,L13(1 IN 1.60 NE555 0.53 TM550 0-60 TC4270 2.25 16A 400V 1.60 MM5214 2665 N3019 0.55 254037 0.651 40673 0.73 50148 0.12 ME0402 0.20 items SEND FOR OUR NEW 168 PAGE CATALOGUE WITH 500 Prices correct at 8th February 1977, but please add V.A.T. Post 5. Packing 30p NEW LINES SEE US AT THE ALL ELECTRONIC SHOW - 55p post paid or 40p to callers GROSVENOR HOUSE 19 -21 APRIL

www.americanradiohistory.com 122 Wireless World, April 1977

SIGNAL SOURCES Electronic Brokers Ltd. are one of the ADVANCE leading electronic instrumentation companies V H F Square Generator SG 21 10 in KH,-100MHz Max oap 2V £35 the UK, providing a full range of services to H1 Audio Signal Generator. 1 5Hz -5OKHz Universities, Industry, Colleges and Sine and Square £35.00 E2 R Signal Generator 10KH:- 100MH2 £75.00 Governments both at home and overseas. We have the largest stocks of secondhand H1 E Audio Signal Generator. Sine & test equipment in Europe as well as a selected Square Wave 15H7- 5OKHz, 200.. Vto range of new products. These are on display 20V (Sine) Distortion 1 %n 1.4mV to at 140V 'square). Brand new condition our London showrooms where customers can

- .... £70.00 examine the equipment of their choice and see it working. AIRMEC Electronic Brokers Ltd. have fully equipped Signal Generator Type 701 30 KW-30 MW 12 only) £75.00 workshops on the premises to test and report GENERAL RADIO on the majority Unit Oscillator 1209C Freq 250- 920MHr Accuracy of equipment we sell. 1% Drift 02', O pin to 50ohms =150mW supplied with Power Supply Type 1201-CO £145 HEWLETT PACKARD 10515A Frequency Doubler Extends the useable frequency range of signal generators Operating on input frequencies 0 5MHe to 500MHe it provides a doubled output in the range of 1MHz to 1GHe The WR/TE frequency response of this 50 ohm device rs very lini 1, c 2dB typically) over the entire frequency range and undesired harmonics are well suppressed Brand 211A Square Wave Generator 1Hz -t MHZ E75.00 i s F M A M NOWM Signal Generator 202H FM AM CW a pulse coverage 54 to 216 MHz R F o p 0 1. V -0 21 50ohms Impedance £450 for a FREE copy Audio Signal Generator 206A 20W-20KHz - 2"- accuracy Distortion . lib. E90 of our latest Test 612A -U H F Signet Generator 450- 1230MHr 0 1 vV -O 5V (50 ohms) A M Internal & external Pulse Equipment mod facilities. SUPERB CONDITION £1250.00 MARCONI INSTRUMENTS Catalogue. Please TF1060 U H F Signal Generator 450- 1250MHz Sine apply on headed wave and pulse a m £350.00 TF867 Signal Generator 15KHr -30MHr 0 p volts' paper. o 4W-4V £155.00 TF2005R Two Tone Source The instrument comprises two identical lowdrstonron a f oscillators and a monitored attenuator unit to form a compact test set installation and service R F output signal Switchable for the measurement of inter.modulation distortion VHF Band Ill and UHF Band IV 1 KW tone for sound using the methods recommended S by M P T E and performance checks (sine wave/ - £155.00 C C I F Frequency range 20He to 20KHa in six bands 50MHz Pulse Generator PM 5712 (435.00 leach oscillator can be adjusted and used rndepen.i Pulse Generator PM5775 £800.00 dently) Harmonic distortion Less than 0 05' %, between, Pulse Generator PM5776 £900.00 631-Ir and 6KHz when using unbalanced output PHILIPS PM5324 HF Signet Generator. Freq Generally less than O 1'%. under other conditions range 100K H -110M Hz. Crystal calrbretion. Intermodulation Below -BOdB with respect to the Special band spread ranges. High f req wanted signal Amplitude Reference Level Up to stability. Electronically stabilised max a tOdBm from ach oscillator Output attenuator output SomV(R MS f in 75 ohms 100mV open 111dB in O 1doo steps Output impedance 600:) 170713 Transistorised 75MHz - unbalanced Calibrated output an neat r. Feci ond'tron £1350.00. or 6001) 1500 or 750 balanced and Mies centre -tapped for internal and teme! AMu & FM. PHILIPS £485.00 Wobbuleting with sweep S H F width contro! 1 OMHz Portable double scope PM3226 Signal Generator 618C 2 87 6GHa 1A 50 Simultaneous A.M. FM. £380.00 ohms £500 & Superb condition SOLARTRON E295 FM /AM Signal Generator TF 995A '35 Ministry Portable Scope DC 6M1-1, Double Beam CT436 E95 SANDERS Portable type No CT402 1 SMHZ- 220MHr R F o p Scope CD 1400c- 15MHr Plug ins a vailabie 2.N-200mV Internal & External Mod Feciloies V CT478 Microwave Signal Generates 5X1441 1443 1448 1571 E180 1 good condition E385 501-12-4 5GHr £285.00 p DCC -40MHr Scope CT484 Dual Trace Displays RADIOMETER Sensitivity FM AM Signal Generator TF995A 5 1 5.220MHz 50mV cm Collection from our premises Stereo signal generator 1 in 5 bands 0 1 .V -200mV F M up to -12OKHr from SMG C Full spec on request only 90-day Warranty £150.00 50Hr-15KHe A M up to 50"0 from 100He -10KHz Superb condition E350 TEKTRONIX o p (1) 2.V-200mV (21 with terminating unit RHODES SCHWARTZ Sampling Scope 661 c w plug ins E450 F 1 .V-1OOmV S H generator Scope Camera C.12 Superb Int mod lregs 400Hz !KHz & 1 SKHz SMCBBN 41042 coed. & complete 1 700.5000MHe Distortion (1) on internal F M ' 25Hr (21 on internal P.O.A. £lSb.00 r WAYNE KERR A M 6 at 30' %, mod E300 to £450 50MHe Model 546 c/w 1A1 plug-in £935.00 A Video Oscillator O 222 ranges Spectrum 1 M Signal Generator TF8010 1 Freq ronge ?KW-8KHr in 6 £75 Analyser plug -in 1L5 50Hr- MHz £875.00 WANDEL 10.470MHz R F output 0 1 . -1V Piston Attenuator & GOLTERMAN 50MHz Model 547 c/w 1A1 plug -in £695.00 U H F Power Oscillator e 50ohms Impedance Modulation Int A M 1 KHr Per LMS -68 w plug In TV Waveform Monitor 525 Freq response Fiat- - A Oscillators M 30He.20KHe Low spurious F M & drift within 1 "i. between 60Hr & 5MHe Low Pass - Passes S 1.0 -4 4 41 V W R 12 or less E400 -E500 ,woe MW stair steps eliminates H F High Pass Passes H F Type - A M Signal GenerefOr TF80113 ' 1S Military versioni 50,40 40.108MHz eliminates stair steps IRE -- meets IRE standards for Type 10- 485MHe £450 -£800 LO- 170 1 70- 330MHr level measurements Sensitivity - Deflection factor of Type 50.610 R C Oscillator TF13704 10Hr -1OMHr Square Wave 610.960MHz The vertical amplifier is 0 015V cm Vert Atten -1 -e up to 10OKHz High Outputs up to 31 6V E285 7 x 5 -x Keyed Clamp type DC Restorer Gain stability Phase A M Signal Generator TF 2003 within 1, E125 0 4,12MHz £1501 Differential Unit 10A1 Used on 647 Series 6300. AM Signal Generator TP 8018 35 12485M Ht MULTIMETERS 585 c w Type 82 Plug -in Duet Trace 80MHz 0 1 N. 1 V £195 AVO B width Sweep Delay £675. Other plug -ins available R C Oscillator TF1101 Frequency range. Test Leads £4.00 30 and 86 20)Z-200KHz Transistor Output Direct into 6000020V Mutt imi no, M4 4 r or ra yang last & leads £13.50 Curve Tracer 575 Displays curves of NPN & AIRMEC variable Attenuator 0 6dB in Ode steps Impedance PNP transistors and dynamic characteristics of a wide lime Interval Meter 369 Mains operated transistorised 6005) Distortion Via't KM, Filter less than 0 1 range of semiconductor devices P.O.A. una Time Intervals 10Onsecs to 30msecs Superb Direct or via Attenuator Less than O 5% 50Hr -20KHz Dual Beam Scope 551 2 vertical deflection systems.. condition £95.00 Less than 1%, 20W- 200KHr £120-E18O Accepts Amp Speer analyser Sampling and special B ECKMAN FM TAM OSCILLOSCOPES Signal Generator TF937 1 CT320 CoSSOR rurpo e P g -i s DC -27MHz Price dependent on Transfer Oscillator 7580H 02 -t5GHz with counter 35KHe -18 3MHr As seen -. 'ug -in required condition E50 35ti +,, .. Scope Tyne 00 5mV r P.O.A' 7 5MHZ 15GHr without counter Sensitivity 100roV Srgnaj Generator TF144H' 4 Late models in super sew, .,i ,,i/, antl sweep itei., ,,aced Tripper 531A DC 15MHz Ose noscope c w K Plug -in Single IR M S I SPECIAL OFFER £250 condition Br, £500 to £580 10cm display BRAND NEW CONDITION £355 Trace 50mV cm 6195.00 B &K TF995B 2 F M 'A M Signal Generator Freq range ',31A 15MHr Oscilloscope r w CA Ping. in Deviation Bridge 1504 200KHz22OMHz Dual P.O.A. Output 200mV to 0 1.V F M Trace 50mV cm £210.00 SIND normal deviation Continuously v s able in 2 ranges DC 544 50MHz Oscilloscope e w 144 Plug -in 14 Coaxial Resistor 8053 1 OW RF coaxial load resistor - 2500e & - 75K1-1, up to 50 a Pet AM & F M cep £800.00 £20.00 available ií44 £585.01 DC-50MHz Oscilloscope c is CA Plug '11 Dual Wattmeter Termalrne 6835 3 anges 0.120/ 0 -600 /O- MARCONI- SANDERS (race 24MO, 5OmV um £375.00 1200W 30- 500MHz £425.00 Microwave 549 Sweep Generator type 6600A c: w 6619 i4 eC4 4 Storage Oscilloscope (Mainframe. £810.00 attmeter iermalme 67 3 langes plug in 1 7Ghz -4 206e £2900.00 TELEDUIPMENT 025 (1100 O-500W 305COMH0 £265.00 .MUIRHEAD 5 F Decade Oscillator 0880A 2.phase c4 COSSOr 075 50MHz Solid State Portable 5mV -20V :Div 0 01 HZ -11 2KHz E295 E515 Component Comparator CZ45n Decade G RUEL Oscillator D890D 1 Hz t 1 2KHz £280 WANDEL & GOLTERMANN & KJAER NEUWIRTH (WEST Automatic Vibration Exerter 1018 GERMANY) BLS 218 Storage 050 illoscnpe c ve Power Control £395.00 VHF Signal Generator MS4 U Freq Range 9 6MHZ to supply £325.00 DECCA 230MHz Turret for DYNAMCO Power Supply for Noise Osc each band Accuracy 1 -2%, PROSES (Now) Source MW 61 P.O.A. o'p 3OmV1.V Freq Dev 1KHe. f00KHt Amp Type 7200 15MHe Dual Channel Penable c w Plug X1 Part No 90 ELDORADO Mod £8.50 0100N. £175.00 Ins 7201 & 7212 Solid State 10mV Idly to 5V /div X10 Part No 91 E8.50 t OnS Trme meter 784 £478.00 )(10 1 PHILIPS on channel permits 1mV /div to 12 5V. div S1 & X10 (switehablel Part No 95 £10.50 FLUKE re PM 5167 Function Generator Sine triangle square Calibrated Sweep Delay c r w ban pack £310.00 positive pulse negative Industrial Counter Totaliser pulse and ramp 9 7 and 1 9 GREENPAR 1941A Frog Measure- 0 001 He to 10MHz (sawtooth and pulse up to max Probe Kits GE8t 60071 - New £25.00 ment 5e -40MHz 40mV nsitwily Totalise 1 MHO Output 40V(P -P) Impedance 50 ohms HEWLETT PACKARD ADMISCELLANEOUS measurements 999999 unirs e P resetta hie display Variable DC Offset RPM measurement External sweep Single shot set 75MHz Model 1707A £875.00 Frequency Counter TCt6 £110.00 £150.00 phase Hold function Overange warning light Superb HEWLETT PACKARD 1 (5A 50MHr Oscilloscope e Plugins 1 MC20 w 7508 Dual Recorder Calibrator £15 igital condition £815.00 Trace Vert D Recorder 560A E110 Amp horny cm 17BOA Auxiliary %Ay Plotter LR t 00 - Further details on request .PM5501 Colour bar generator Extremely light and 11858n1000 Digital Recorder 561 B £140 compact instrument for mobile £325.00 Directional detector 787D 19.4 1Gh, E90 maintenance 5 MHz Oscilloscope Sampling c'w Plug-in Digital Panel Meter DPM302 different test patterns for newt E45.00 Directional detector 788C 3 7.8 3Ghr £95 colour and black 'white TV 188A or Plug -In 187C Digital Panel Meter DPM301 £395.00 mewl £50.00 UHF Attenuator 355C E90 -70 ELECTRONIC 49 -53 Pancras Road London NW1 2QB Tel: 01 -837 7781 ADD 8& VAT TOALL PRICES

WW - 110 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 123

eve ' etc, ' easurements + to m u I On these pages you will find just the Spec on Request , 400.00 range we A.F. TRANSMISSION MEASURING SET. Model, briefest selection from the vast which TF2332 Frequency Range 20Hz to 20KHz Accuracy at least +15 dBm hold in stock at any one time. 21 %. _O 2Hz Mao output If you are seeking a specific item and it is RADIOMETER Wave Analyser FRA 2 T3 Special version of FRA 2 not listed, it will pay you to ring us first - we with facilities for intermodulation measurements and and the best selective measurements of frequency responses Freq believe we offer the best prices range 30Hz to 16KHa Incremental freq OH: to Service. 60Hz Selectivity 3 curves with following I dB points WORLD WIDE EXPORT y 1 2510, y12 5Hz, 1-63Hz and 60d8 points y 40H:. . 130 H, . 350 Hz Enquiries and tenders welcome from any - 150 450 part of the world. 'Voltage range 100uV - 1RV Aueilrady Oscillator Range 0Hz to 1 6 KHz and 1 5 to I SKHZ o/p - 10V HOW TO REACH US (EMF) continuously variable Impedance I Kohms ... 16uF £375.00 We are easy to reach, no matter where you WANDEL S GOLTERMAN live. Minutes away from Kings Cross or St. Level Transmitter TFPS 42, 10 KHz -14MHz Generator 0/p level 0 8n1V -2 5V FSD Lowest adjustable 50uV Pancras main -line stations, and a bus ride from Synchronous tuning of generator and level meter posslbte. Output impedance 150. 75. 70, 60. 50 and Euston; only just over half an hour from ohms 25KH: Fine Tuning range £250.00 Heathrow Airport. Level Meter TFPM - 43 10KHz -14MH: 3dB Bandwidth (600Hz and 4KHe) Selective measuring range 8V to 40uV (lowest readable 2 uVO. Swstcheble bandwidth - 15KHz fine tuning High sensitivity Full specification for the above on request £250.00 ee Distortion Meter VZM 83 52 / 304 / 556 kHz This unit comprises a generator and receive portion and operates according to the intermodulation method This distortion measuring set is mainly used to measure transmission distortions occurring on FM radio link systems £190.00 VZM2 Distortion measuring set for phase and amplitude mod For multichannel FM Radio Systems up to 12MHz base bands E350 DIGITAL VOLTMETERS AND MULTIMETERS DYNAMCO D V M DM 20225 lOuV-2KV Max reeding 39999 Accuracy 0.02% Resolution 1 in 40,000 Input impedance 25KMohms £265.00 Digital Voltmeter DM 2023 C/w DC Ranging unit Cl Scale 99999 0 001% F S D DC Accuracy 10uV -1 Kv DC £460.00 D V M DM 2004 P.O.A. J. FLUKE Digital Multimeter 8120A Measures AC and DC volts to 1200 volts AC and DC current to 1 2A Resistance to 12Mohm. 4 digit plus 20% overange Compact and lightweight £235.00 HEWLETT PACKARD 14 5.. 0 ectronic oitmeter DVM type 3430A 3 digit. 5 ranges 100mV to 100V No 3 CT 208 TF 958, AC tOOmV150V. Voltmeter F S Input resistance 10Mohms Overload protection multiplier extends AC range to 1 5KV. DC £145.00 5OmV -100V Freq Range 200,- 100MHZ E55 Valve Voltmeter TF2600 E175 PHILIPS Digital Multimeter 34702A with Display H F MiIlivoltmeter GM 6014 Measuring Ranges 34740A 4 digit display. 4 rangea both AC & l mV -300mV in 6 ranges Accuracy at T:OKHz at 3% of DC plus 6 ranges of ohms AC function FSD - Amplitude Char 1 KHz -30KHz fat within 25% sri 45Hz to 100KHz. Ohms ranges E55 100ohms to lOMohma F.S. LED drplay New DC Microvdtmeter GM6020 10 uv-1 KV current condition A much sought cher device still in 10pA -10uA Accuracy 5% (FSD) 0- 100uV. 3% (FSD) currant production E400 AU other ranges Recorder o/p facility E6 PHILIPS TELEPHONE D.M.M. TYPE PM2423 3'h digit, DC Volts 2V -1 KV AC VOLTS 2V -350V. R -200 ohms - 200 Mobms. Accuracy 0.1% of reading Automaticiange switching TEST EQUIPMENT for all functions. Automatic polarity indicator £140.00 SIEMENS TYPE PM2522. 3'h digit DC Volts 0.2.1 KV, Level Meter 3D 332 0 31200KHz £250 D.M.M. AC Volts V. AC /DC Current 0.2mA -2A. R Level Meter 3D 335 10KHz -17MHz C300 0.2.600 POWER 200 ohms 20 M ohms. Accuracy 0.1% ± 0.1% of SUPPLIES Level Oscillator 3W29 0 31200KHz E250 - range DC Volts. Full circuit LED display APT ELECTRONICS Level Oscillator 3W518. £300 protection. .... (Er ICI Computers) 240V i. P ...... £150.00 SION/ ROGERS Type 10459/11 - 210V 7.5A.... £19.00 A F Voltmeter AM324 £50.00 Type 10459/8 - r20V 5A . £12.00 BRIDGES Type 10459/13 - 224V 5A £12.00 MARCONI INST. SOLARTRON C LM 1219 30mV -300V mean reading Type 10459/12 .- '10V 3A E15.00 TF936 Impedance Bridge E125.00 A Convener _Freq range IOHe -10KHz P.O.A. I.S.M. Universal Bride TF 1313A £828 D C Digital Voltmeter LM 14201. 2.5 uV -1 Kv in 6 Ex Computer Load regulation of 1% or better Low L C R Bridge TF 8688 £115.00 0 05% DC accuracy £235.00 ripple. fast response time 220 /240V v P TF1245 CCT Magn Meter c/v OscIllator ranges Type 1420 280 DC. true R M S and mean 3V 4V £12.00 TF1246 £685.00 D V M LM - Accurate m ent irrespective of BA WAYNE KERR A C sensing z N 3V - £15.00 Freq 3v 16A E20.00 Radio Freq Bridge 8601 hat' c distortion accuracy2025% - E325 XY Omngrapmc Recorder type 6520 P.O.A 6V 6A £15.00 R F Admittance Bridge B701 40Hz- 20Kee - DC in 5 rangier XY & XYY Ommgraph4 Recorder type 6452 P.O.A 112/115N/1/P COMPONENT BRIDGE 1521 (CT 375) DVM Type LM 1449 2 10uV -2KV Oven controlled zenerdlode Accuracy 20.033% FSD MARCONI INSTS. 6V 12A £15.00 Self-contained portable mains operated equipment' - 005% reading P.O.A. Ahenuator TF 1073A/2ß E55 20V 15A £20.00 designed to provide accurate measurements over an 0 - V M LM 1480 3 Autoranging version of LM Quantization Distortion Tester TF2343 P.O.A. wideide a ge of resistance capacitance, D Also stabiiised but unregulated 48V -- 2 7A, 7 25V'- Max reading 39999 5uV -2KV DC. Full Kit TM8120/ 1st for use with valve voltmeter inductance and impedance values Reverence 10 14403 Pmbe 4 BA £5.50 TF2600. Brand new E20 ranges from 1m ohm to 1000 M ohm Capacitance 10 request ICI Power Supplies (ex-computer) 1604 DC only 1 uV sensitivity 0 OIA, A F'Power Meter TF893A 20Hr 20KHz 1,0W to 10 ranges from 50k uF to 500pF Inductaree 10 ranges DV M n1M 6V -25A (variable from 4 5V to 8V) accuracy Max reading 19999 1uV -1KV Remote F 2 5 ohms to 20Kohms in 4B Steps from 1 uF to 500 KH Capable of measuring Watts S Z = -20A (variable from 25 -30V) No E110.00 28V components in situ £105.00 and Autorenging 110dB series mode reject on common Mode error P.O.A. '0" Meter TF 329G E200 TF 2404 / 2MI Checks 0 M M 7050 lautoranging) £245.00 Out of Limits Indicator VOLTMETERS VIDAR readings from electronic counters and other digit, ADVANCE TRANSMISSION Integrating DVM 520 6 ranges IOmV -1KV costs. Local and remote visual and electrical Indication, AC Mdlrvoltmeter £50.00 VM770 Guarded can be floated to it 500V High measurement suitable for use by unskilled personnel and with GENERAL RADIO TEST EQUIPMENT speed with ultimate C M R No filters Up to X6 faster A T E P.O.A. Electronic Voltmeter 1806A. AC. DC & OHMS y 2'k. than most integrating D V. M's Built -in calibrator Myer TF 2908 E90 Accuracy Wide Freq Range up to 1500 MHaE200.00 AIRMEC /RACAL Blank & Sync to £300 Manual. automatic and remote operation Wideband HEWLETT PACKARD Wave Analyser 248A 5- 300MHz 250 PYE 248 Freq range freg and period measurements ere standard. 10mV Thermocouple ins, set 7556 E95 DC Vacuum Tube Voltmeter 412A IMV1000V 1% Wave Analyser £145.00 F S range burltin eliminates ext pre-amp no loss of RHODE I. SCHWARTZ Accuracy Can also be used as Ohmmeter and Ammeter 5MHz- 300MH: Modulation Meter 409 P.O.A. C M R Freq range 10Hz -2MHz £525.00 Polystop Swob II E1000 E75 Type 210 Modulation Meter (earlier version of 210A) i VTVM. 400D 1mV to 300V FSD 12 ranges 10Hz to Selektomat USWV .. ... , ... AMC.1. REMEMBER ... We also buy Frequency Indicator FKNBN 47051 £479 4MHz 2% accuracy Input Impedance 1 OMohms £55 E66 -Eí00 TEKTRONIX VTVM 400L Logarithmic version of 400D Reads RMS Type 210A Modulation Meter 2.5 -3w MHz. A.M. We ere interested in providing quotations Range %. F.M. Range s. 100 in 4 Programmer 262 P.O.A: value of sine wave Log voltage scale 0 3 to 1 & 0.8 to 0.100 0 to KHz for the purchase of good quality used and ranges Sri Wave Gen 105 Risetime -- 13m secs Freq 3 Linear dB scale Input Impedance lOMohms £90 ..... £155 -£245 unused Test Equipment. range -- 25H: 1MHz continuously variable Freq Vacuum Tube Voltmeter 400H Freq Range HEWLETT PACKARD Meter -- Direct reading O/P Amplitude 0 -100V 10Hz-4MHz Volts 1 OmV -300V F S (12 ranges)' Sweeping Local Oscillator 3595A Plug- n for use with mar £90 Accuracy 21 % (5OHe- 500KHz) '- 2% 3590A Wave Analyser Freq range 20H: tw TELONIC (20H0- I MHz) P.O.A. 62010Hz £650.00 Band Pass Filter TBA 140- 60 -5CC1 5Section TNC to AC Voltmeter 400F & 400E £155 MARCONI INSTS. INC connectors 1/4" tubular 60MHz bandwidth MARCONI Distortion Factor Meter TF 142F Fundamental Freq 140MHz centre lreq Brand new £20 Sensitive Valve Voltmeter TF 1100 100.V -300V AC Range 100Hz --BKH: Dist measuring ranges 0.5% :::ewsntoewnk.satliirnesePlePa ó% bare Sweep Generator Sm2000 0/w plug-ins 8 -3M and S.6 Freq coverage 10H, 10MHz Meter has dB scale 0-50% Measures all sputious companents up to the and S4MM P.O.A. facility E66 30KHe Es0.00- £60.00 t hem You WAYNE KERR Valve Voltmeter TF 10418 General Spec 0300V Ac Anenuator 70dB in 1008 & 1dB steps 0/p Z 75. require is Current Ratio Transformer T102C P.O.A. 0.1 KV DC Resistance u to 500Mohms C80 / E66 150 & 600 ohms balanced or unbalanced Distortion Please wit BROKERS LTD give Carriage and packing Please note: All instruments offered are charge extra on all items secondhand and tested and guaranteed 12 unless otherwise stated months unless otherwise stated

WW - Ill FOR FURTHER DETAILS

www.americanradiohistory.com 124 Wireless World, April 1977

; EL 1 3 1 58.60 GROVE RD. I1i1 -Il' I i.,

OR AS CURRENTYT l\ 1 I FGI>I 11 IO\

SEND (.\ 1 O ( I:X( 1 I r WINOSOR,BERKS. COV I DEPT ) TRffT1PlJ5 ]OST & PACKING 201 FOR THE U.K. BARCLAYCARD 4 ACCESS BY POST 11111111M SL4 ills. OR E:5 1115 ON T1iI.1:PII05I Oltur.I1S. == ILMIE NEW CATALOGUE I IS'r FREE 5.1.11. pr:' EIECTNI11(11CS1T1 TEL. 5425 13:\CK IF '( . i TOP DISCOUNTS. NEW LOW PR /CES. Full spec devices INTEGRATED CIRCUITS TRANSISTORS AND DIODES NORMALLY 1.14 HOURS 555 TIMER 34p* LM3801,'G'4;J LI 77S ,r: E\ STOCK ITEMS BUSH SET Lp eq' TIP31 /32 50p* 55G 2 x 555 90p* I.\1381 Preamp C'? MATCHISO ^Op Pr" TIP:i1c32cG8p* 703 RF /IF :IMP 29p LM3900 4xOPA 53p* AC127/8 176 15p* TIP41 /42ea 60p* 709 TO99 or DIL2Gp* MC'1:303 2xPre C2 ÁD1611 /IO2 ea30p* TIP41c12c "[1.50* pen 710 DIL11 :35p* \1C1310 stereoE'2 00107 8p* TIP2965 69p* 75p 723 Regulator lip* MC1312P SQ 11.70 ßC1070 1:3p* TIP305 5 Gyp* PEI; ETCH KIT G ITEMS [.. 711 DIL Spin 21p* MC1:3:10 75p ßC108 8p* TIS43 UJT 26p ETCH RESIST PEN 2TIPS 75r

711 DIT. 11pin 31p. VC1:3:39 PrcampL2 0C 10811 or C 13p* 1N911/4148 4p EEC ETCH PAK 1'1113 1100gm E I

711 jlt' T099 :33p* 4FC4`000I3 72p 00109 9p* 154001/2 4p* 6ix I " SR13P 4 Sp "SYLON F /G: I 717 D11AT. 711 69p* MFC60:30 t] 0('110)3 or C 12p* 151001 5p* 718 IIIL 8 pin :12p* 5I.5:38 FETOPA C2. 50117/8/5 8p 151007 7p* SCR AND TRIACS 11RIn0 25p 7805 5VIA +regt1.:15' NE540 or 550 C2* 00.157/8/0 Ilp 257066/8 14p* TAG 1Á400V 50p.1A600v G;p 1,1.501 375 * .0106)0 15410 R 7812 R 7815ea£1.40* 5E555 'l'IM]':R :31p" ß('167 /8 /2 12p 202616 ELT 105* 'F11IAC'S: SF116D 10A1001 7601:3 GW AF (1.50 51`.556 2x55:5 90p* (Cl77/8/1) 1Op 2 \2901/ 5pnp29p* C1 DISCO TRIAC 12:1-101)1 C2* ... E SEGMENT LED DISPLAYS AY51224 CLOCK L4 * NE560/1/2/5/5/7L:3 B('182/3/.17G;1op 2 52926 oro 7p* IGISF DT.707 COM ANODE S C.A3016 54p* S572711 as 741 130212/3/47/ 11Sp 253052 17p* AUDIBLE EARNING BLEEPER 1.701 Croa C.ATH. 0.5.. CI* ICL8038 SEgen Cl S5766610 IF 71p ISCY70 /I/2 15p* 253050 9011' 33p* 12V:33mA (1.20 110 off ('1* 717 0,6"4TUMRO ('1 LM30011 L'1 SS71i6I1 IF Cl ßD131 /132ea 36p* 253055 115w45p* CAPACITORS 22pí - ,r11 LM301A Dil 8 33p" 'rI3A800 5W AF 81 p 1FY50/51 15p" 253614 11); Cl. I(IIT:A1. CLOCK IC ... ELECTROLYTIC IN In LM309K 5V reg C2 'I0A810 71S AF 91p BFY52 /5:3 16p" 253702/3/4 lop ,:I:NON STROBE THEE 172/10/50/tno 7p 500 1 L }130911 TO5 can Cl* 55111 Radio C1.19 BSS 19/20/211 :4" 253705/6/7 9p 200 /500 101).1000/2.5 205 L11318 7OVUSOPA E3* NEW 1466/619 (1 I32188 TI. NI:R 10p 253708/9 9p REO LEdS SOP. CIOGD SCR 54p* 253710/11 15p POTENTIOMETERS Ai) etc20p MJ2955 '(1)3 59p* 253819 &23e17p PRl:SIi'1'S Gp (:.liI.SISTORS III 1) . 1 G. CFT1S jR. MJE29S5 99p* 253820 PFET4Op HKATSINKS TOG or 15 7p OR G.-" .IP 1+Ip' IJE3055 65p* 253901/5/6 15p 'r1):) 16p,T0:3 1-finned 50p 1000 14p* 7400 12p* 7190 59p* DIN:PLUGS TIL209 RED 1.1:1) g CLIP 12p* 0581 /01 5p 255457 FI:T 32p all 1Sp,Sock lop 4001 15p* 7.101 13p* 7191 75p* SWITCHES 0,2" LED 14p* TIP29 :c 30 10p* IRIDGl:1A50 20p* SPST 20p Opdt 29p I3IG RED k" 1002 16p" 7102 15p* 7492/93 40p* 29p* GREEN OR ORANGE 1.I.OS 4007 16p* 7401 19p* 7495/06 72p* GAS DETECTOR TGS :30Rctct4* 34p* OHP12 5lp*255777/OCP71 1009 50p* 7408/10 18p* 71100 (1.25* BARGAIN PAKS FULL SPEC (lea, 1011 16p* 7113 29p* 71107 52p* P.AK A: II 111':D LEDS full spec C1* TRAMPJS 4012 1 7p* 7740 16p* 74121 29p* PAK I3:5 711C 8 PIN OP AMP C1* 69p* vero 4049 50p* 7141 71p 71123 PAK C:4 2\3055 Cl. Il THE GREAT 12 13C109 Cl* VERO 0,1" PITCH MPPLIIC51h BRITISH 4069 20p* 71 -12 72p* 71111 71p" PAK E: 11 13C'182 L1 F 11 253701 C1 .. 79p* 85p* 10p 4501 26p* 7417 71145 PAK G: 7 I3FY51 (1* II 8 2\:3819 C1 DISTRIBUTOR 2i' x3r3C,p 4511(1.65* 7470/72 27p* 71117 ,2.50* PAK 1: 6 253155 Cl. K 10x15011 C1 74151 75p* 37:17- .,) 1105 1 : 4528 (1* 7473/71 31p" PAK 4' :3 T009 3055 ( i*\ 25 01(1(1 OS.AL, TH.ADE 35p* 01.10* DTI. BREADBOARD :1-x1 L1 -- I NDUSTRI AL, ED1C: \TI 1543 C2* 7475/36 71151 PAK P: 20 PLASTIC I3C109 l'YPlinpnL1 (2.V1:R0 PISS :1r3 & EXPORT SUPPLIED, SEND FOR 4553 (5* 7486 35p* 74196 (1.50* :1r1p1 OUR FREE CATALOGUE LIST SAE BLACK PLASTIC CASES 12mmx DIL SOCKETS PROFICSSIONAT. QUALITY 10 -365PF 'l'UNER,SINGLE GANG FOR MANUFACTURERS EXCESS STOCKS MED /SHORT It.AVE,STAL SET etc Cl. 80x00 :50p*110x72 niip*r OFF 8pin,14pin S 16pin ALL 12p ea PURCHASED. DISCOUNTS 10F SETS /IF CANS 155/170KHZ TOKO Cl* 120 7Op.D1CSOLIIER 100 up. 15'7 OFF 1000 up.... SOLDERCONS 100 49p* 1000 13,95*

iZTX504 25 2N1671 1 50 12636354 6 1,264304 44 7 (ZTX510 16 2616714 1 60 1263641 12N4410 50 (ZTX530 23 21416718 1 80 (2043642 2N4416 70 (ZTX531 23 2N1711 30 12043643 7 12N4416E 40 (111X537 20 2N1889 34 12043644 8 12N4871 50 }ZTX538 18 261890 14 12043645 8 0265126 18 }ZTX541 20 2N1893 28 T2043646 7 1265127 19 261990 ORCHARD WORKS, CHURCH LANE,WALLINGTON, SURREY SM6 7NF }ZTX542 25 58 12043691 6 0265128 16 1ZTX550 20 2042102 50 1253692 5 12N5129 17 MAIL ORDER DIVISION OF SEMICONDUCTOR SUPPLIES (CROYDON) LTD.. TZTX551 21 2042160 90 12043693 1255131 17 N914 06 2N2192 40 }1043694 }2N5132 i7 For Semiconductors Capacitors Resistors I/C Sockets LE.D's and N916 07 2N2192A 44 120437(12 (2N5133 7 4C125 8C1088 12 15 N4001 07 2N 2193 35 1263703 4 20 (BC173 BF 257 20 í8U 133 195 TIP31A 57 12N5135 18 13 N4002 2621934 40 1263704 ÁC125 20 ß0106C }ß0173q 16 Hi-Fi Accessories ßF258 40 tß0205 200 TIP310 64 07 4 0265116 18 ÁC127 20 ßC109 13 }801738 16 N4003 07 262194 35 3263705 4 t2N5117 18 ß0212L 15 ß0307A 16 BCY58 22 ßF259 42 }ßU206 2.30 TIP 310 79 AC127K 30 8C1098 13 t6 45 44004 08 2621944 40 12043706 12N5139 (8C173C 1ßC212 LA 13 }ßC3070 16 80V70 17 BF271 40 10U 208 2 TIP32 60 17 AC128 18 BC109C 14 }ßC174 16 ßV(26 16 N4005 09 2N 2218 30 1263707 4 16 13 18C307C 16 8CY71 18 30 TIP32A 67 AC128K 26 780113 12 ßC177 17 í8021218 16 N4006 10 2622184 33 (2043708 12 18C308 12 8C572 14 10274 34 ßV127 TIP328 76 16 ÁC132 35 }ßC114 15 8C177Á 17 180213 N4007 11 2N2219 30 }20437(19 }802134 12 0ß0308A 14 60115 60 ß336 32 TIP32( 94 34 30422194 1 AC 141 20 7ßC115 15 ß0t770 18 9Yí64 40 84 N4009 06 31 12043710 16 7ß0213B 12 }ßC3088 14 BD1 T1 90 33 TIP33 15 17 N4148 06 2N2220 20 0263711 1 4C1a1K 30 íß6íió ßC176 14 15 34 eY %10 14 TIP33A 94 SI1 (81121311 í80308C 60123 90 262221 20 2 00 15 18 1 N4149 08 763771 ACta2 20 TBC n 6A 8C178A 14 18C309 14 t8FR39 26 MJE2955 40 TI P33ß 05 50 (802131 B0124 86 2622214 21 2 10 AC142K 25 íßC117 18 ßC1788 18 MJE3055 90 TIP33C 31 N5400 13 263772 50 T8C213LA 14 1ß0909A 16 80131 42 IBFR40 30 20 AC151 10 8C178C 18 OAS 71 N5401 14 2N2222 263771 3 10 52 24 18C118 1ßC21318 14 7ßC3090 16 80132 42 1ßF841- 32 TIP 34 00 8C119 28 BC179 18 N5402 16 262224 21 263789 3(10 40 601516 34 15 t6C309C 18 65 (ßF879 26 OÁ70 62 TIP 344 13 }BC 125 16 19 18C213LC 80(33 N5403 lg 262368 20 263/90 3 30 ÁC153 27 ß01798 11 32 OÁ47 74 TIP 34B 26 40 }ßC214 (5 íßC317 (ßD135 37 7ßF880 20 25 3 AC153K 20 ß0179C )9 30 TIP N5404 2N2369 1N1791 10 42 37 180116 14 tBC317A 12 (BD736 39 (80881 26 OÁ70 340 59 25 11 TBC2748 30 N5405 24 2623694 26 2043797 180 AC176 22 tBC128 }ßC182 20 3t 78 12 BFW 10 68 TIP35 65 14 12 7ß0214C ie (ßD137 44 pq N 5406 28 262646 50 12043793 36 AC176K 28 7ß0t31 }BC í82A 0318 10 68 79 30 TIP35A 2 67 68 7ß0215l 18 T (ßD138 a7 N5407 35 JN2647 85 12613794 14 AC187 22 1BC134 14 }8C1828 12 24 OÁ81 30 TIP35B 2 80 65 15 i8D318A 71 (8D1;í9 54 30 38 11 18C214LA N5408 40 262904 (2N3919 60 AC1871( 27 7ßC135 14 (80182L (BC214L8 16 íßC3188 11 }ßO140 58 11 S44 O6 2N79n4A 33 1263819E 31 . (ßC136 16 }BC182LA !!'1111291 OÁ90 UB 7IP36C 61 AC188 20 20 TBC318C 12 80144 200 55 302 25 48 11 }BC2I4LC S920 07 262905 12638211 . 74 AC188K 27 }80137 16 tBC182Le 75 BFX29 TIP36A 331 }BC 183 10 í8C237 15 18C319ß 7ßD155 5921 08 2N29054 28 2N3821 73 ÁD149 70 ßC738 28 12 8Fx 30 25 OÁ95 08 T1P368 363 90 10 1BC237A 16 1 }80165 43 5922 09 262906 25 263872 64 ÁD161 BCt39 35 }ß0103A 12 BFx38 25 OÁ200 09 7IP36C 4 10 50 92 1ßC2378 16 1ß0319C }80232 1 00' 10 2N2906A 2N?fl2? 5R (801838 f0 OÁ202 09 TIP41 S923 50 ÁD162 BC140 30 14 180320 13 180X32 2 25 BF %39 25 60 10 180238 2N404 1 10 2N290J 1;7'1 12N3A23E 26 ÁF114 24 ßL141 32 1ß0183K0 114 }80183L 10 í802384 15 800)20 80 2N456 80 2629074 26 263874 52 142 } 14 0025 2 98 TIP41A 65 260 4015 24 BC 22 15 1ß0320B ßF115 22 BFx48 36 27 95 (BC183LA 10 18C2388 94 2N456A 90 (262923 2043866 1112 AF116 24 80143 28 15 20 13 10 1ß0238C (ßF152 2N457 1 20 1262924 23 }2N3903 70 ÁF117 24 7ßC147 10 7ß0183Lß íß0321A 14 SFX84 22 0C25 1 10 TIP42C 18C239 12 ief 153 24 1 12041904 14 í80183L0 10 2N457A 30 1262925 24 2(1 ÁF118 70 1ßC 1474 il (8C3218 14 (ßF154 20 Bf X85 28 0035 96 TIP42A 80 18C239ß 13 1 f2042926 71 12639(15 1, 96 T1P420 2N4$8 30 8rn 20 ÁF124 30 íe01478 11 18C184 13 í80321C 15 ßF156 25 0C36 90 1 Red 12 12 7ß0239C 2N458A 40 1262926 1263906 1 90 AF 125 30 í8C 148 08 ( ß0t848 }ßC322 14 of 157 26 BfXe6 21 OC41 80 TIP42C 1 10 13 1 ßC257 20 2N525 1 10 12042926 Orr; 2114030 20 ÁF126 28 TBC148A 09 1101ß4C 20 98D3228 15 1ßF158 20 BFxe7 24 OC42 90 0)1P2955 97 í8C258 2N595 30 17 2N40-. 1 (18 í8C1488 09 1ßC 184E 11 15 BFX88 22 0043 230 TIP3054 50 ÁF127 28 }ßC259 20 180322C }ßF159 26 2N697 30 (2N2926 YeI 14 204, 4009 80 ÁF139 }ß0í48C 09 }BC 1ß4L8 12 20 }ßF160 20 BFY 50 28 62 48 34 BC 261 17 1ßC327 2N706 20 Grn 2N4r,1, .'. 13 OC45 60 ÚC7345 60 1262926 4(110 80 1 10 ISC164LC 18 BFY52 28 ÁF178 20 (ßC149 ßC2618 18 í8C328 ßF166 38 2N7064 15 2N4036 an 4011 20 12 8C186 25 18 BFV 52 58 OC 71 56 }ZT %107 14 ÁF179 1 20 (8C1498 5C2610 18 78C337 ßF167 21 2N708 22 263053 30 2\4037 34 4012 20 12 ßC187 26 DC?? 60 1117x108 12 ÁF180 1 }BC 1490 t8 16 ßF173 20 BFV53 20 20 802610 (ßC338 26 71 1 75 263054 60 12N4058 16 4017 15 t 55 18 15C204 ßC461 35 24 BFV 56 26 0073 00 127 %109 l4 AF181 1 20 }ßC153 ßC262 17 ßF177 267114 77 2143055 80 i7N4059 10 4014 195 }BC 2044 16 14 8F178 BF064 27 0074 62 (21X300 15 ÁF186 120 }5C154 te BC262A 17 }5C547 24 26718 22 263440 55 12044060 4015 1 O(1 1ßC2048 16 15 STA 67 1117 %301 16 AF239 37 1ßC157 1, ßC2628 17 1SC547A ßF179 75 BFY72 27 267184 27 2\3441 96 12Na061 12 41)11) 55 14 0076 56 (117x302 18 410)26 40 (BC157A 12 í8C205 802620 17 TBC 5478 15 ßF100 30 26743 20 2113442 35 2N.1062 14 4(117 11)0 1 20 15 12 SF181 30 SF075 17 0077 }ZT%303 20 AS127 45 18C1578 12 BC205A ßC255 17 (8C548 26744 20 7143525 91, N1174 '0 4018 1 40 8C2058 15 13 17 OC81 701 lZTx304 23 461128 40 9ßC758 10 ß0266A 18 f8C5486 ßF182 34 BF076 26753 22 20 4014 rill 15 0082 67 (117x310 14 12\3563 ASY29 45 }BC 75ßA It 1ßC205 ß0266B 18 }ßC5486 13 ßF183 34 BSW66 65 - 2N910 72 \3564 20 4020 In 15 OC 83 67 f719ill 15 12 ASY67 140 }ßC1588 11 fSC206A ßC267 17 1ßC549 14 ßF184 25 BSW67 70 2N914 24 1263565 48 18 4(171 100 7ßC2068 15 BC2674 15 í117x3í7 17 48721 200 }80159 12 17 (8C5498 8F185 28 SSW 68 BS 0870 26916 28 f2043566 49 20 4022 100 10 67 (117X313 19 }gÁ145 15 18C159ß 13 (ßC207 ßC2678 17 7ßC557 11(ßF194 10 85x79 23 26918 33 }263567 1)250 22 11 00171 6a ¿rx314 24 }8A14ß 15 )SC159C 13 1SC207A ßC268 17 98C558 11 íß0t95 10 BSx20 ¿3 1 2N929 12N3568 1.12S6 4124 B1 1 22 34 }ß0207B 11 12 OCP70 68 ( ¿7x320 19 äA164 10 }ß0t67 13 BC268A 17 (ßC559 T8F196 12 85 %21 26 26930 27 }263569 24 4025 0 10 OCP71 1 75 (Zrx321 t8 ßA155 t2 }ßC168 12 100208 ßC2688 17 815030 90 (ßF197 12 BS %27 27 261131 30 263576 77 4026 1 90 13 }ßC169 14 7ßC2088 ß0268C 17 BCY31 98 BF200 3A BS %29 23 }0P292 263611 4027 6 (1 ßA156 a2 IZT%íi0 261132 30 98 25 ( 11 BCY32 1 }0 1 22 91) 84X12 II }ßC170 tt BC269 17 (ßF244 32 85X66 23 261302 36 263612 41) 1299 27 4(128 }8C208C JTIP29A d7 5218337 17 54X13 07 }8C171 14 11 8C287 28 8CV33 80 (BF244A 37 85X67 30 261303 36 763613 490 24 4029 1 10 }ßC209 JTIP29H 53 }117x336 15 t8C171A 14 12 ßC300 27 SCY34 90 }Bí2448 37 85595 24 261304 50 263614 60 `.1291 27 4030 65 BAX16 07 }8C2098 (TIP29C 57 }117x341 15 13 ßC301 26 BC538 100 (BF244C 37 SSY95A 24 20 2N1305 45 2613615 7( ,a?92 78 4031 2 411 00107 12 í8C1718 (BC209C (TIP30 50 (117X342 13 815Y39 22 1 12 í8C172 14 ßC302 26 3,H/ 78F245 42 ISU105 200 261306 54 263616 90 i1 00 BC107A }TIP3OA 56 (21x500 17 (ßC212 13 BCV40 1 15 )8C 1724 15 ßC303 30 15 }ß0245A 40 í6U105 -02 261307 54 263617 1 60 BC 7078 ITIP308 63 (111x501 18 15 TBC 2124 13 ßC304 27 BCY42 28 7602458 40 2 25 261308 2043618 20 500 5C108 11 í8C1720 TTIP30C 78 60 15 }ßC2128 13 (ßC307 15 8CY43 25 }ß0245C 2 50 }117X502 20 ß0108A It (801720 1ßU108 2N1309 6,0 2143632 ' higher rare for issue 3 catalogue TIP31 51 1ZTXSQ3 21 ALL PRICES EXCLUDE VAT Items marked Inds t carry of V A T otherwise 8% Please send SAE new _21111613 ao 12 \3638

www.americanradiohistory.com Wireless World, April 1977 125

SAME DAY DISPATCH ELECTRONIC DIGITAL CLOCK ORDERS RECEIVED BEFORE 2 p.m. are posted on the same day. A professional product for the home constructor It has been designed modern techniques and components It From this . . . KIT - to this by engineers using the most will appeal both to the confirmed hobbyist and to the man who simply wants to 'have a go'. The kit contains everything except a mains lead The only tools required are a small soldering iron. solder, screwdriver Electronic and wire cutters Digital * LARGE BRIGHT GREEN DISPLAY Timepiece * ATTRACTIVE ACRYLIC CASE in * 12 /24-HOUR READOUT LESS THAN L9.60 + 76 Pence VAT ONE Electronics & Time HOUR METAC - Centre 67 HIGH ST., DAVENTRY, NORTHANTS TEL. DAVENTRY !032 721 76545 OR 3 THE NEW ARCADE, UXBRIDGE, MIDDX. TEL. UXBRIDGE (0895) 56961 Cash, Cheques or Postal Orders, Barclay & Access Size 10 5 x 5 7 x 8 cms welcome. Just send Credit Card number WW -104 FOR FURTHER DETAILS

THE REAL THING B.P'O. TYPE 3000 PPM2 DRIVE CIRCUIT UNDER LICENCE FROM THE BBC WITH HIGH DUALITY Ernest Tuner SPECIAL BALLISTICS PEAK PROGRAMME METER MOVEMENT RELAYS AND 600 !14'i/kinsons requirements T ^e PPM. ,ed un the ME12 9 u utwu, an ec .. -. tali, voltages nicattons and of on the .,mal Unes Il meets 8S4297 the prove, ...i . rope 1 melee rest known or an ays with a large var ety coma' spec...61,h.. and Willis the requirements ul the IBA LEK., and BPU Revieweu Studio Sound September 1976 arrangements Known throughout the world Comore!, Meter movements 642 643 and TWIN from stock The TWIN is a hush mounting Iype and (lush mounting banks of contacts made to order and component pa'., adaptors which allow illuminai on are a.anabie for the 642 and 643 NEW Illumination kirs for 642 and 643 sipptied Highest quality at competitive prices wan :, and mouldings to support a 38 i...... ,. i.. ,11 quick delivery service Quotations by return home with overseas Taon relays Latching Relays and Relays ugh voltage contacts made to order We are supplier, P Relays and Of mountings to house B 0 Type 3000 and Relay `elmpo grinds R Relay ?non and 40011 i ii. and Relay -

APPARATUS RACKS. POST OFFICE STANDARD 7FT HIGH WITH U- CHANNEL SIDES DRILLED E25 FOR 19 INCH PANELS HEAVY ANGLE BASE P 0 STANDARD LIGHT STRAW COLOUR EACH. HIGH SPEED COUNTER 10 counts per and with four digits sue 3'. . I t" mailable in the following DC voltages 6c12 24 50 or 100 volts £1.75 PEAK DEVIATION METER ;J each, also available with five digits E2.75 each. duct 200,150 volts or 100; 125 volts E t 5 For monitoring mono or stereo FM stations eahe oil air ui at the Iransnet lei this is a rack mounting unit BLOWER UNIT with glass fibre air filter and directional calibrated in KHI percent and decibels including a 7 5KHz deviation standard with 4006, and 53KH, each. mirror scalee E 20 each. modulating frequencies and a high impedance probe head lu, use with a murmur receiver Donny programme ELLIOTT Test Set reading absolute DC vunit with monitoring the true peak multiplex deviation with a vein lust attack time meter gives much more insight in to BRIDGE Power Factor and wattage unit Ee0 oath. E95 s 1 bo each. levels limiter overshoots than spectrumspec analysert displays or standard programme meters MEGGER 000 volts with modulatiuri and 1 BRIDGE HOUSE, LONGLEY ROAD, showing the decoded stereo signals Chart rP .order addition in June L. (CROYDON) LTD., LONGLEY WILKINSON Grams: WILCO CROYDON SURREY ELECTRONICS CROYDON, CRO 3LH Phone: 01- 6840236. The Forge, Lucks Surrey 7BG )STD 04866) Green, Crenle,gh, GU6 5997 t. 41111111111. ANEW 'IOW 41111111111110. -a -WW-I09 FOR FURTHER DETAILS-

NEW IMPROVED NEW( AMERICAN STYLE CRADLE TELEPHONE AMPLIFIER MAINS INTERCOM NO BATTERIES BI- PRE -PAK NO WIRES COMPONENT BARGAIN SALE ONLY £29.99 PRICES INCLUDE V.A.T.. POSTAGE IN U.K. NO EXTRAS £13.95 POSTAGE DEDUCTED FOR PERSONAL SHOPPERS +VAT L1 12 per pair transistorised Telephone Amplifier + V A T. E3. 75 Latest TRANSISTORS mix- ACTIVATED S.C.Rs is automatic with detachable to and Telecommunica- i nn 2 LIGHT completely Made British Safety ed types PNP geran- 1 Type With full data plug -in speaker. Placing the receiver on tions Standards The modern way of instant 50v 6A LF9 ium PNP and NPN and 14 protect details to the cradle activates a switch for 2 -way communications. Supplied with sibcon AF and RF £1.35 immediate two-way conversation with- 3 -core wire Just plug into power socket L - types Unmarked and out holding the hand-set. Many people Ready for use Crystal clear communications untested Good yield £1.35 BUTTON TUNE can listen at a time. Increase efficiency from office to office Operates Aver 1/2-mile PUSH in office. shop. workshop. Perfect for range on the same mains phase. On off I.Cs mixed type's. ASSEMBLIES "conference" calls: leaves the user's switch Volume control Useful as office 00 marked Ideal for Irr, TM TV. and Radio vancap tuners hands free to make notes. consult files. intercom, surgery and homes. between experimenters. etc Li. Bland new by famous maker long waiting. On'Off switch, volume office and warehouse No GPO licence No mxed supplies £1.35 4- button assemblies £1.9 control. Model with tape- recording required Full price refund if returned in 10 facility (16.95 + VAT E1 36. P. & P. 75p days Six months' service guarantee. P 40 WIRE WOUND 7 -button assemblies C W O 10 -day price refund guarantee & P 90p RESISTORS mixed salues and wattages 85p WEST LONDON DIRECT SUPPLIES (W/W) EX- G.P.O. POTENTIOMETERS INSTRUMENT CASES 169 Kensington High Street, London W.8 40 iyreyt arious values and H yarn ie ellea Infernale ing and pane, types. some switched, aluminium heatsinks, etc h Ideal fur P A pre etc usable as -set. £1.35 power supplies. oscilloscopes. instruments etc 100 DIODES silicon. equal BRAND NEW, BOXED to 1N914, IN4148, etc. unsorted. untested 75p SIZE 'A' - 14 x lb x b dery , 12' buy, lease SIZE'9' - v ". ,b "c deep or rent: DIODES, germanium, 100 glass and metal Teletype 33 and DD390 (locos) printer terminals t m -- 50 ONLY SIGNAL GENERATORS DECWRITER LA36 and DD303 (3ocps) printer terminals EHT RECTIFIER Med Wave S I F I pocket size STICKS for colour TV £5.25 12 KV work- OKIDATA 1101661pí1) and Teletype 40 (300lpmI high -speed printers niplers ing Type CSD11 8XP 65p POCKCT SIGNAL INJECTOR Lear Siegler ADM 1,2 and 3A video keyboard display ZENER DIODES to trace fault, in AF RF TV etc £2.75 Teletype 40 (non baud) asynchronous and synchronous displays rayes Untested 75p DD Paper tape punch range (up to 110 cps) WHEN ORDERING PCBPrimed vt,,d !;u.htt plain capper laminate. for prompt delivery npprox 250 sq ans in ADC FUR POS telephone London(01) 848 9761 about 7 pieces £1.35 accordingly Abn Ednlxrgh (031) 226 6201 cred.,,d to you Data lot as wily as stocks last Dynamics Manchester (061) 224 3306 dd WEST telex 935429 220 -224 ROAD WESTCLIFF -ON -SEA, ESSEX SSO 9DF PRE -PAK Telephone Southend 46344 BI- 107021 WW - 052 FOR FURTHER DETAILS LTD. Personal shoppers welcome

www.americanradiohistory.com C 126 Wireless World, April 1977

EL83 0.70 P61 3.60 PY88 0.40 U18/20 1.80 Z145 0,67 AFI02 1.04 CG 12E /.73 0C42 1.73 PABC80 0.45 ELM 0.34 PY301 0.50 J19 4.00 Z152 029 AF106 058 CG64H 1.23 0C43 1.37 PC86 0.62 B ENT LEY AC OU STIC ELM 4.q PY500 110 U22 0.85 Z329 0.70 AFI14 030 FSYIIA 424 0C44 0.12 PC88 0.62 EL90 0. PY500A 1.20 U25 0.71 Z7I9 020 AF115 03/ FSY4IA 1.25 0C45 1.13 PC92 0.55 EL95 0.07 PY800 040 U26 0.60 Z729 5.45 AF117 0.23 GD4 0.38 OC40 5.18 EL360 190 PC95 0.70 COR PORATI ON L TD s PY801 0.40 U31 0.50 Z749 CM AF121 435 GD5 532 OC85 1.31 PC97 EL506 120 075 PZ30 0.50 U33 1.75 Z759 5.65 AF124 036 GD6 032 0070 1.14 PC900 0.40 7A GLO UCESTER ROAD, LITTLEHA MPTON, SU SSEX. Te I. 6743 EM80 055 QP21 1.10 U35 1.75 AF125 054 GD8 1.23 OC71 0.13 0.é0 PCC84 039 ALL PRICE N E EM8I QQV03/10 U37 2.00 Transistors AF139 0.76 GD9 023 0072 1.13 INCLUD V.A.T. A T 12 t/2 % PCC85 0.47 EM83 0.00 2.00 U45 1.20 and Diodes AFI78 0.79 GD1I 023 0074 026 0A2 0.85 6138G 0.35 8L6GC 0.70 2AT7 0719 0.39 EBL21 2.00 PCC88 0.81 034 30PL12 0:10 EM84 0.45 Q575/20 1.00 047 0.71 1N1124A0/1 AF180 1.K GD12 0.23 0075 5.13 OB2 0.40 6BA6 0.40 . 6.54 30PL13 1.00 0729 0.79 EC52 1.00 PCC89 0.49 2AU6 EMS 120 QS95/10 1.00 U49 0.60 1 N9744A 5.14 AF186 014 GDI4 0.58 OC78 5.18 0Z4 055 613C8 0.90 6L12 0.39 EC53 LOS PCCI89 12AU7 034 30PL14 129 BL63 2.00 EM87 110 052 Q5150/15 190 U50 0.55 1N4952 058 AF239 1.44 GD15 0.47 0077 432 IA3 0.60 6BE6 0.40 6L18 0.110 EC54 1.00 PCC805 12AV6 OM 30PLI5 1.110 eL33 1.75 EMM803 230 075 QV03/121.65 U52 0.60 2N404 021 ASY27 454 GD16 023 OC78 0.18 1A5GT 0.55 6BG6G 1.00 6L19 2.00 35A3 ECM 0.84 PCC806 0.70 12AX7 034 0.75 cv6 090 EY51 0.45 QV01/7 3.00 U76 0.70 2N966 0.61 ASY28 0.38 GETI13 0.23 OC78D 0.18 1A7GT 0.10 6BH6 0.70 6LD12 0.44 EC88 0.84 PCF80 12AY7 1.00 35C5 1.80 0.63 1.00 EY81 0.45 0.40 QV06/20 3.50 U78 0.45 2N1756 0.58 ASY29 0.58 GET118 023 OC79 547 IB3GT 055 68J6 0.65 6LD20 090 EC92 0.55 PCF82 128A6 4.54 35135 050 Cv988 0.25 EY83 4.N 0.45 RII 1.49 U81 0.80 2N2147 0.80 BAI02 5.53 GET1l9 030 OC81 0.13 IC2 1.00 6BK7A 0.85 6N7GT 0.70 1211E6 35L8GT ECC32 1.00 PCF84 070 435 OIS CYIC 1.00 EY84 1.211 R16 2.00 U150 052 2N2297 026 BA118 0.14 GET573 5.44 OC81 D 11.13 IDS 0.75 613Q5 0.34 6PL12 0.40 35W4 ECC33 200 PCF88 0.57 12: 0.55 CY31 0.70 EY86/7 037 R17 1.00 U153 0.40 2N2369 0.16 BA116 0.21 GET587 050 OC82 513 IG6 100 6BQ7A 0.60 6P15 0.34 :Y7 5Z3 DI 0.50 ECC35 2.00 PCF87 0.77 090 EY88 650 R18 1.20 U191 0.50 2N2613 0.45 BA129 514 GET872 1.11 OC82D 0.13 IH5GT OM I6BR7 1.00 6Q7G 0 D63 0.30 ECC40 0.90 PCF200 120 12E1 330 Z4GT 070 EY91 11.511 R19 0.75 U192 0.40 2N3053 038 BA130 0.13 GET873 018 OC83 0.23 IL4 025 6BR8 1.25 '6Q7GT 0 I2JSGT OM Z5GT 090 DAC32 0.80 ECCBI 0.34 EZ35 0.45 PCF201 1.00 R20 0.60 U193 0.40 2N3121 290 BA153 1.18 GET882 838 OC84 028 !LDS 0.70 6BS7 1.70 6Q7M ECC82 0. 2J7GT 0. 2 150 DAf91 0.35 0.34 EZ40 0.52 PCF800 077 R52 0.48 U251 1.00 2N3703 0.23 BCY10 1.53 GET867 026 OC123 0.26 ILNS 0.70 6BW6 1.70 6R7G 0.70 ECC83 5085 0.95 DAF96 0.60 0.34 EZ9I 0.52 PCF801 0.49 55(34 1.00 11281 0.75 2N3709 0.23 BCY12 0.58 GET889 426 OC139 0.50 1N5GT 0.75 6BW7 0.65 6R7(M) 1.00 0.70 ECC84 0.35 PCF802 I2K7GT 1.58 5005 070 DC90 EZ80 0.32 054 SP4 1.50 U282 0.70 2N3866 1.16 BCY33 1.23 GET896 0.28 OC140 1.11 1R5 010 6BX6 0.29 6SA7 055 0134 ECC85 039 PCF806 12K8 1.73 50CD6G 120 090 EZ81 0.40 1.53 SP13C 075 U291 0.50 2N3980 1.58 BCY34 0.26 GET897 0.28 OCHS 0.50 IS4 0.M 6BY7 036 6SC7cT 0.75 ECC86 1.25 I2Q7GT 459 50EH5 095 DF33 0.75 EZ90 0.45 PCH200 1.00 TH/4B 1.00 U301 055 25323 0.58 BCY38 424 GET898 1.24 OC 17I 0.40 155 0.35 6BZ6 0.60 65G7 0.50 DF91 ECCOB 0.51 i2SA7GT 1.73 50L6GT 1.00 0.30 FC4 1.01 PCL82 0.40 TH233 1.00 U329 1.00 AA119 0.18 BC 107 0.14 GEX113 0.21 OC 172 0.41 IT4 0.30, 5C4 0.40 6SH7 ECC91 055 12SC7 6156 66KU 0.52 DF96 0.60 0.35 FW4/500 186 PCL83 0.49 TP2620 1.00 U339 0.50 AA120 0.18 BC108 0.14 GEX36 058 0C200 0.55 1114 0.70 6C5G 0.60 65.17 1.1111 ECC 189 12SG7 055 72 0.70 DH63 0.50 090 FW4/BW LM PCL84 0.41 TP22 1.00 0381 0.35 AA129 0.18 BC109 514 GEX45 0.38 OC201 0.53 IU5 035 .6C6 0.45 6SK7GT 0.55 ECC804 0.79 12SH7 030 77 0.45 DH76 0.50 GY501 495 PCL86 054 TP25 1.00 U403 0.90 AAZl3 021 BC113 0.30 GEX55 0.87 OC204 0.50 2021 0.55 6C9 2.00 0.1111 ECC807 65Q7 12517 OM 810.2 0.75 DH77 0.50 290 GZ30 0.48 PCI98 129 UABC80 0.45 U404 0.75 AC107 0.18 BC115 0.18 GT3 030 OC205 0.50 2GK5 075 6C10 0.71 6U4GT 0.80 ECF80 050 12SK7 /.M 05A3 0.75 DH81 GZ32 0.00 PC1900 1.00 UAF42 0.70 0709 0.40 ACI13 0.30 BC116 0.30 MI 0.18 OC206 1.05 2X2 0.70, 6CB6A 0.50 ECF82 0.50 a' 12SN7GT 0.75 90CV 3.80 DK32 060 PCL805/85 UBC41 050 U801 0.80 AC114 0.47 BC118 026 MAT1O0 0.45 ORPI2 0.61 3A4 0.55 6C12 18- O56 47 D1C40 0.70 ECF86 0.80( 0. 11.114 108C1 0.41 0134 0.75 060 UBC81 0.55 04020 0.75 AC126 0.14 6E154 0.30 MATIOI 0.541 SFT237 0.50 3B7 0.55 '6CD6G 1 6V6G 030 ECH21 >s IM 15082 1.00 DK91 0.50 2.00 PEN4DD 2.116 UBF80 050 VIS492 9.50 AC127 020 13E158 021 MAT120 0.45 SM1036 0.58 3D6 0.40 O. i 6V6GT 0.6/ 1.60 6CG8A +R7 0.75 I50C2 0.85 01(92 1.00 ECH35 HABC90 /80 PEN25 110 UBF89 039 VP2 1.50 AC128 0.23 8E159 024 OA9 0.14 5T1276 058 3Q4 091 6CL6 0.7 0.70 ECH42 0.71 PEN45 X 4H7 1.75 215SG 0.00 DK96 HL13C 0.64 1.00 UBL21 2.00 VP4(5) 2.00 AC132 0.23 8E163 0.23 0A47 0.12 5X1/6 0.21 3Q5GT 0.70' S6CLSA 0.95 T 0.45 0.40 ' 1457 110 302 120 DL63 0.70 ECH8I HL23 0.70 PEN45DD IIO UC92 0.50 VpI3C 0.60 AC154 0.30 8E173 044 0A70 0.18 U14706 0.30 t 3S4 0.45 6CM7 6Y6G 1.00 0.95 18 125 303 1.20 01.82 0.80 ECH83 0.50 HL23DD 6.68 PEN46 0.50 UCC84 0.90 Vp23 0.65 AC156 0.23 8E180 0.35 0A73 0.18 XZ30 0.30 3V4 0.80 6CS6 0.45 6Y7G 1.25 0.45 ECHO4 0.50 19AQ5 016 305 120 D192 HL41 IJIO PEN453DD UCC85 0.45 VP41 0.90 AC157 0.30 8E181 0.47 0A79 0.11 Y543 0.21 4CB6 075 6CU5 0.90 7A7 1.00 ECL80 0.45 191366G 110 807.-- 1.10 D194 0.80 HL41DD LEO 2.011 UCF80 0.80 VR105 0.50 AC165 0.30 13E185 0.47 0A81 0.11 Y728 0.21 5CG8 0.75 6133 0.75 786 ECL82 0.80 19G6 010 956 050 D1.96 0.60 0.50 HIA2DD 1130 PENA4 LOS UCH21 2.00 VT61A 0.75 AC166 0.30 BFY50 0.24 OA85 0.11 5R4GY 1.00 , 6DE7 0.90 7B7 090 19H1 4.N 1625 250 DM70 0.80 ECL83 0.74 HN309 1.70 P EN DD / UCH42 0.71 VÚ111 1.00 AC167 0.69 BFY51 1.23 0A86 0.23 5T4 1.110 6DT6A 095 706 2.00 19Y3 1.40 1821 1.00 DM71 1.75' ECL84 0.65 HVR2 1.50 4020 1.05 UCH81 0.45 VUI20 1.00 AC168 0.44 BFY52 023 OA90 0.14 5U4G 0.N 6EW6 0.85 7F8 2.00 OCIAS 0.70 20D1 4.71 5702 120 DW4/350 1.15 HVR2A 1.00 PFL200 0.70 UCL82 0.45 VU120A 1.00 AC169 0.38 BTX34/400 0A91 0.11 ALL 5V4G 0.p 6E5 LOO 0.80 ECL86 0.64 7F17 20D4 254 5763 195 DY87/6 0.35 KT2 090 P133 UM UCL83 0.57 V0133 1.00 AC176 0.64 2.31 OA95 011 5Y3GT 0.55 6F1 7R7 EF22 1.00 080 2.00 20F2 013 6057 1.011 DY802 0.45 K 3.00 PL36 0.811 UF41 0.70 W76 0.50 AC177 0.32 BY100 021 OA200 0.11 PRICES 5Z3 1.11 6F6G 0.60 7V7 2.00 20L1 1.21 6060 110 ESOCC 2.50 EF40 0.78 KT41 1.00 P191 0.49 UF42 090 W81M 1.20 ACY17 0.30 BYI01 018 0A202 0.12 5Z4G 0.48 6F12 0.50 7Y4 EF41 0.75 INCLUDE 0.80 20P1 LOS E80CF 5.00 KT44 1.00 PL81A 053 UF80 040 W107 0.75 ACYIO 0.23 BY005 1121 OC19 1.46 5Z4GT 0.55 6F13 090 7Z9 0.80 20P3 1.10 E80F 2.20 EF42 0.90 KT63 010 P192 0.37 UF85 0.50 W719 0.36 ACY19 0.23 BY114 021 0C22 0.44 V.A.T. 6/30L2 0.71 6F14 0.90 802 0.50 20P4 1111 E83F 1.60 EF73 1.75 KT66 3.60 P193 545 UF89 0.45 W729 1.20 ACY20 021 BY126 038 0C23 0.44 6A8G 1.40 0.20 NOTHING 6F15 095 8E18 0.45 20P5 1.50 7025 150 E88CC 1.20 EF80 KT71 1.0/ P194 050 UL41 0.70 WD709 0.40 ACY21 0.23 BY127 0.21 0C24 044 6AC7 0.55 6F16 0.75 9BW6 0.90 25A6G 0.70 7193 0.110 E92CC 0.70 EF83 1.25 KT81 2.611 P1302 0./0 UL46 0.70 XE3 0.60 ACY22 0.18 BYY23 1.16 0C25 0.44 6AG5 0.33 EXTRA 6F18 0.60 9D7 0.70 25L6G 070 7475 1.20 E180CC 0.80 EF85 034 KTSB 0.75 P1.504/500 0194 0.54 XFY12 0.60 ACY28 0.21 BYZIO 030 0C28 0.69 6AG7 0.60 6F23 0.65 0.45 9U8 0.45 25Y5 010 9002 0.55 E 180 1.15 EF86 KTW61 110 0111 UM80 0.60 XH15 0.60 AD140 0.42 BYZII 0.30 0C29 073 TO 6AH6 0.70 6F24 EF89 0.42 080 10C2 0.70 2514G 454 9006 /.45 E182CC 2 KTW62 1.50 P1.505 2.00 URIC 1.00 XSG15 1.20 AD149 0.58 BYZI2 030 0C36 4.50 6AJ5 0.70 PAY 6F25 1.00 10C14 0.45 25Z5 1,75 A1834 1.00 E188CC 2 EF91 0.50 KTW63 120 P1.508 1.10 UU5 1.15 X41 1.00 ADI61 0.63 BYZI3 530 0C38 5.50 6AJ8 0.40 6F26 0.36 IODI 0.85 EF92 0.50 PL509 2.011 25Z6G 0.80 A2134 3./0 E280F 00 L63 050 UU9 0.52 X61 1.60 AD162 6.53 BYZI5 3,03 0C41 11.58 0.45 6AK5 6F28 0.74 100E7 090 28D7 2.00 A3042 6.1111 E1148 .60 EF93 0.40 LN119 0.45 P1901 0.74 UUI2 0.40 x63 1.40 6AK6 MATCHED TRANSISTOR 0.70 6F32 0.70 10F1 0.67 30A5 0.75 AC2PEN IM EA50 0.40 EF94 0.40 LN152 0.45 PM84 0.75 UY41 0.50 X65 1.60 SETS LP15 (AC I13, ACI54, 6AK8 0.40 6G6G 0.60 10F9 0.65 30C1 0.40 AC2PENDD EA76 EF95 0.45 LN309 049 PY31 0.50 UY42 0.50 X66 1.60 AC157 AA120), Olp per pack. 1 /OCSID 6A1.5 0.20 6GH8A 090 10F18 0.65 30C15 0.77 1.00 EABC80 040 EF97 0.90 LZ319 0.44 PY33/2 050 UY85 0.35 X76M 0.75 and 2/OC81, 54p. 6AM6 0.50 6GK5 0.75 10L14 0.45 30c17 0.77 AC6/PFN 1.04 EAC91 0.55 EF98 0.90 LZ329 0.4/ PY80 O50 1 /0044 and 2/0045, 38p. U10 1.00 X119 0.45 /OC82D 6AM8A 0.70 6GU7 090 IOLDII 0.75 30F5 0.70 AC/P4 1.51 .EAF42 070 EF183 042 M8162 110 PY81 11.441 U12/14 1.15 X142 0.71 I and 2/0082, SOp Set of 3/0083. 76p. 1 watt Zenners, 2.4v, 6AN8 0.70 6H6GT 0.30 IOLD12 0.45 30L1 0.39 AC/PEN(7) EAF801 0.75 EF184 042 MHL4 110 PY82 0.40 U16 1.00 X150 0.71 2.7v, 3v, 3.6v, 4.3v, 4.7v. 5.1v, 13v, 15v, I6v, 10v. 20v, 24v, 30v, 12p 6AQ5 0.68 635GT 056 10PL12 0.45 30L15 0.75 121 EB34 0.30 EF804 1.75 MHLD6 4.99 PY83 0.44 U17 1.00 x719 0.40 each. 6AQ8 0.39 435 .10913 0.80 301,17 0.70 AC/TH1 LM E891 0.20 EH90 045 MKT4 121 6AR5 6.17G 035 10119 2.50 30P40.111 8.118 ALSO 5.20 EBC41 0.75 EK90 0.40 MU12/14 L15 All goods a e unused and subject to the manufacturers' guarantee. Terms Cash 6AS7 1.00 10P18 0.54 .30112 0.74 ARP3 ON EBC8I 0.45 EL32 0.60 MX40 LAO of business. or cheque with order. Despatch charges: - Orders below £15 in value, add 6AT6 050 I2A6 0.65 30P19/ ATP4 0.50 EBC90 0.50 EL34 1.00 NI50 157 25p for post and packing. Orders over £15 post and packing free of charge. All orders cleared same day. Any parcel insured against 6AU6 O. _:7 12AC6 090 30P4 0.M AZ1 /.il EBC91 0.50 EL35 3.00 14308 018 damage in transit for 5p extra per parcel. Conditions of sale available on 6AV6 050 'rj éT'w I2AD6 0.80 30P18 0.57 AZ3I /.N EBF80 0.40 EL37 3.00 N339 123 request. Many others in stock too numerous to list. Please enclose S.A.E. for reply to any enquiries. 6AW8A 0.84 6K8GT 1.53 12AE6 090 30018 0.50 AZ41 0.51 EBF83 0.45 EL4I 0.57 N379 0.50 Special offer of valves, 6AX4 0.75 6L1 2.50 12AT6 045 30PL1 IM B36 /.75 EBF89 0.40 EL01 0.65 N709 0.34 EF50 soiled but new and tested, f1 each.

FAST RESPONSE STRIP CHART RECORDERS Made in USSR Series H3020 Series H327

Basic error 2.5% Polarized moving iron movements Sensitivity: 8mA F.S.D. with syphon pens directly attached. Response: 0.2 sec. Built -in solid state amplifier (one Width of each channel: per channel) provides 8 calibrated Single and three -pen sensitivity steps. Two marker pens recorders: 80mm are provided. Five-pen recorders: 50mm Basic error 4 %. Frequency response from DC to 100Hz 2dB.

Chart speeds, selected by push buttons: 0.1-0.2-0.5-1.0 - 2.5-5.0- 12.5 -25 mm /sec. Chart drive: 200 -250V 50Hz Recording: Syphon pen directly attached to moving coil frames. Sensitivity: 0.02 - 0.05 - 0.1 - 0.2 - 0.5 - 1 - 2 - 5 volts /cm Curvilinear co- ordinates. Width of each recording channel: 40mm Equipment: Marker pen, timer pen, paper footage indicator, 10 Chart drive: 220 -250V 50Hz rolls of paper, connectors, etc. Chart speeds 1- 2- 5- 10 -50- 125 -250mm /sec.

H3020 -1 (Single pen): 285mm wide x 384mm deep x 165mm Type H3271 -1. Single pen: Dimensions: 259 x 384 x 165mm high PRICE £108.00 Weight 15 kilos PRICE £265.00 H3020 -3 (Three pen): 475mm wide x 384mm deep x 165mm Type H327 -3. Three pen: Dimensions 335 x 384 x 165mm high PRICE £160.00 Weight 20 kilos PRICE £520.00 H3020 -5 (Five pen): 475mm wide x 384mm deep x 185mm Type H327 -5. Five pen. Dimensions: 425 x 385 x 165mm high PRICE £295.00 Weight 25 kilos PRICE £770.00. Note Prices are exclusive of VAT Available for immediate delivery Z ác I AERO SERVICES LTD. 44A WESTBOURNE GROVE, LONDON W2 5SF Tel. 01 -727 5641 Telex: 261306 WW - 061 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 127

SPECIAL LOW PRICE ARRANGEMENTS FOR VISITING OVERSEAS TRADE FAIRS Zur iem

I PC Electrical - Electronic Press Ltd., the world's largest publishers of computer, electrical and electronic journals, have made special arrangements for readers wishing to visit important overseas trade fairs. The cost, in most cases, is little more than the normal air fare but includes - travel by scheduled airline from Heathrow and Manchester * first -class hotel accommodation * arrival and departure transfers * admission to the trade fair * services of an experienced tour manager. The current programme comprises the following tours.

To obtain a brochure and booking form, tick the box against the tours in which you are interested, complete the coupon and post to the exclusively appointed travel agent, Commercial Trade Travel Ltd., Carlisle House, 8 Southampton Row, London WC1 . Telephone 01 - 405 -8666 or 01 - 405 -5469.

International Exhibition of Paris March 31- Computer. Systems & Brussels May 10 -12 1977 Electronics Components j April 6 1977 Peripheral Exhibition & Conference - COMPEC EUROPE ]

International Radio & TV Berlin August 26- Hanover Fair E Hanover April 20 28 1977 Exhibition [ September 4 1977

International Exhibition of Munich October 17 -21 International Electric Chicago April 26 -29 1977 Computers and Peripheral 1977 Exhibition and Vehicle equipment - SYSTEMS [ j Conference H

International Exhibition for Munich November 22 -26 Electronic Production - 1977 PRODUCTRONICA

Please send details of the tours indicated above.

NAME COMPANY

ADDRESS Telephone

www.americanradiohistory.com Wireless World, April 1977

The All- Electronics Show 1977 Grosvenor House, Park Lane, London

April 1 9 -21 , 1977

E .E r wireless work! Visit our combined stand at the All- Electronics Show, and prove your skill as a driver - *Enter and play the all -new racing game 'Le Mans', a challenge of speed and skill, with prizes for the winners, donated by Light Soldering Developments, C.B.M. Ltd., Siliconix Ltd. and National Semiconductor Ltd. companies exhibiting at the show.

ELECTRON /WIRELESS WORLD published by IPC Electrical & Electronic Press Ltd. Proceeds will be forwarded to EE IBA

www.americanradiohistory.com 129 Wireless World, April 1977

OUR PURCHASE FROM THE DYNAMCO FACTORY CLEARANCE SALE

DATA LOGGER :. by DYNAMCO +3999 1435 SURPLUS - y NEW These are BRAND NEW 416.141/ w BRAND - - mi ' si s REPLACEMENT TUBES FOR not finished - DATA sir,A "s.. ° LOGGERS BY DYNAMCO DYNAMCO 7100 SERIES OSCILLOSCOPES TYPE They are compeleted but for the in boards. a se wngedith hi lid BRIMAR 013 -5IGH is quite superb and extremely adaptable. It contaThe as well as th e mother board an equally superb Power Supply with the following voltages +28V; +15V; +5V (2.5A) - this supply is crowbar Mesh P.D.A. Transistor Scan. Wide Bandwidth 6OMHZ +. 6 x 10 protected; -5V; -14V; -20V; -24V; -48V and other supplies cm-1KV EHT. X Sensitivity 1 5V /CM. Y Sensitivity 6V /CM. Standard including auto 110V. This unit supplied in its original cardboard box heaters. complete with original manual must be of serious interest to the THIS IS A MUST AS A SPARE FOR THE DYNAMCO 7100 SCOPE OR professional constructor and any one considering the construction of a IDEAL FOR THE HIGH QUALITY TRANSISTOR SCOPE BUILDER. micro processor system. Unit size 71/2" high x 19" wide x 23" deep. At £65 each. Carriage £2.50 Numetal Shields available at £2.50 Price £45 each. Carriage £2.50

ALSO AVAILABLE TUBE TYPE BRIMAR D10- 210GH/32 BRAND NEW at £70 ea. Carriage £2.50

SUPERB PROFESSIONAL VDU CASES, size 23" x 16" x 27" on stands. Hammer grey. BRAND NEW SCHLUMBERGER Surplus £40 each. Carriage £2.50

C.D.C. DISK DRIVES complete with electronics, LINE PRINTERS - VARIOUS MODELS power supply, etc. Fine condition with Disk Pack. £100 £100 each. Carriage £15 each. Carriage £15

MINIATURE - OXLEY PATCH PANELS - BRAND NEW EX DYNAMCO 10 x 10 complete with pins. £10 each. P &P 50p

EDWARDS HIGH VACUUM PUMPS

Type 1 SC30 @ £55 each. Type ES35 @ 45 each Carriage £2.50

Quantity of CABINETS - Approximately 5ft. 6in. an'd smaller. Computer types - very smart. Prices from £4 to £20 dependent on size. Carr. £2.50

VARIOUS MODELS OF PUNCHES /READERS available for your inspection PRICES FROM £15. Carriage £2.50 FRY'S ELECTROVERT WAVESOLDERING APOLLO SCRIBEMASTER MACHINE PRINTED CIRCUIT BOARD MAKER Type WASL 12 - Complete with Ultrasonic cleaner, Fluxwave £475 applicator, jet blower, etc. £1,250 LARGE QUANTITY DYNAMCO TEST UNITS, OSCILLOSCOPE TUBES, RESISTORS, CAPACITORS, TRANSISTORS, PUNCHES, READERS, PATCH PANELS, PATCH PANEL PLUGS, ASSEMBLIES; FERRITE CORES, KNOBS, FREQUENCY COUNTERS, DVM's, SCHLUMBERGER BATTERY PACKS, 74 HUNDRED IC BOARDS, COMPUTER PANELS, FIBREGLASS BOARD, TRANSFORMER C CORES, CITENCO REDUCTION GEARED MOTORS, AB POTENTIOMETERS VARIOUS VALUES, KEYBOARDS, TUNING CAPACITORS, TRIMMERS, SMOOTHING CAPACITORS and VARIOUS TEST EQUIPMENT including SOME UNFINISHED OSCILLOSCOPES and other ITEMS. Available for your inspection NOW. CALL - SEE AND BE TEMPTED VALUE ADDED TAX not included in prices - VAT at 8% Official Orders Welcomed. Gov. /Educational Depts., Authorities, etc., otherwise Cash with Order Open 9 a.m. to 5.30 p.m., Mon. to Sat.

MIL'FIIE* LTD ' s 7/9 ARTHUR ROAD, READING, BERKS (rear Tech. College, King's Road). Tel. Reading 582605

www.americanradiohistory.com 130 Wireless World, April 1977 Why settle for yesterday news?

News Reviews Technical Developments Production Methods New Products Design Finance Share Index Management Marketing Appointments Vacancies Exhibitions Electronics Weekly THE TECHNICAL AND BUSINESS NEWSPAPER OF ELECTRONICS AND COMMUNICATIONS

r ,

Order your copy by using this form Electronics Weekly, c/o Room 218, Dorset House Stamford Street, London SE1 9LU

I wish to take out a one year subscription to Electronics Weekly Remittance enclosed for £6.00 (U.S.A. /Canada $15.60)

NAME Please um* ADDRESS

Registered in England No. 677128 Regd Officer, Dorset House. Stamford Street, London SE1 9LU

www.americanradiohistory.com Wireless World, April 1977 131

TEXAS TTLs by C-MOS I.Cs OP. AMPS TRANSISTORS DIODES 7400 16p 74109 89p CD4000AE 20p AC125 25p 8FY90 1209 *253702 12p 1458 Dual Op Amp Inl Comp 8 pon DIL 70p 20p 74H00 28p 74110 55p AC126 BRY39 45p *253703 12p *SIGNAL CD4001AE 20p 301A Ext Comp 8 pin DIL 36p AC127 20p 74S00 63p 74111 90p CD4002AE 20p BSX19 2op *253704 12p 0447 9p 3130 COSMOS/Eh-Polar MosFel 8 pm DIL 100p AC128 18p *253705 12p 0470 9p 74LS00 30p 74112 96p AC141 20p BSX20 20p CD4006AE 95p 3900 Quad Op Amp 14 pin DIL 70p *8U105 140p *253706 12p 0481 15p 7401 18p 74116 200p CD4007AE 20p AC142 20p *253707 12p 0485 15p 536T FET Op Amp 10.99 275p AC176 20p BU 108 250p 7402 18p 74118 84p 61p *2N3708 12p 0490 7p CD4009AE 709 Ext Comp 8/14 pm DIL Sop AC187 20p *MJE340 45p 7403 18p 74120 120p 120p *253709 12p 0491 7p CD4011AE 20p 741 Int Comp 8/14 pin OIL 22p AC187K 25p MJ2955 7404 23p 74121 32p CD4012AE 20p MJE2955 130p 253773 25Op 0495 7p 747 Dual 741 14 pin DIL 70p AC188 20p 253866 90p 04200 Bp 74H04 36p 74122 54p AC188K 25p MJE3055 70p CD4013AE 55p 748 Ext Comp 8/14 pon OIL 36p *MPSA06 30p *253903 18p 04202 10p 7405 25p 74123 76p CD4015AE 90p AD149 49p *2N3904 169 15914 776 Programable Op Amp TO -5 140p AD161 36p *MPSA12 50p 4p 7406 43p 74125 73p *253905 20p 11,4916 9p CD4016AE 50p 36p *MPSA56 32p 7407 43p 74126 70p AD162 *MPSU06 *253906 lep 154148 4p CD4017AE 100p LINEAR I.C.s AF114 20p 62p 7408 25p 74128 75p CD4018AE 110p *MPSU56 7e9 *254058 15p *AY.1 .0212 Tone Generator 16 pm DIL 600p AF116 20p *254059 10p 7409 27p 74132 70p 52p AF116 20p 0028 75p CD4019AE *CA3028A Difl Cascade Amp T05 95p *254060 13p RECTIFIER 7410 18p AF117 20p OC35 75p 74136 75p CD4020AE 120p 'ICA3046 5 Trans,stor Array 14 pm DIL 80p 0C36 75p *254123 22p 81100 25p 74H10 28p 74141 75p CD4022AE 10op *C43O48 Quad Low Noise Amp 16 pm OIL 200p AF127 25p *254124 22p *60126 12p AF139 43p *3C71 20p 7411 24p 74142 320p CD4023AE 22p *CA3053 Doff Cascade Amp T05 70p *R2008B 200p *254125 22p *8Y127 10p AF239 4ßpp N4001 5p 7412 25p CD4024AE 80p CA3080E Op Transcond Amp. 8 pon DIL 90p *R1010B 200p *254126 22p 74145 90p BC107 B 9 *254289 N4002 5p 7413 36p 74147 190p CD4025AF 22p *CA3089E FM IF System 16 pm DIL 225p *TIP29A 4op 20p *CA3090 FM stereo Multi Dec 16 pon OIL 400p BC108,B 9p *2N4401 27p N4004 6p 7414 75p CD4026AE 170p BC109/B lop *TIP29C 55p 74148 160p ICL8O38CC VCO Fun Gen 14 pm DIL 340p *TIP30A 48p *254403 27p N4005 6p 7416 33p 74150 140p CD4027AE 65p *LM 380 2W Audio Amp 14 pm DIL 99p BC109C 12p *TIP30C 60p 254427 90p N4007 7p *8C117 22p 7417 36p 74151 72p CD4028AE 98p *LM 381 Stereo Preamp 14 pm DIL 1759 TIP31A 52p *255089 27p 55401 13p *6C147 9p 7420 18p CD4029AE 120p *LM389N Aud Amp +3 Trs Array 18 pm OIL 160p TIP31C 52p 2N5296 55p N5404 18p 74153 85p *BC148 9p *255401 N5407 23p 7421 40p CD4030AE 55p *M252 Rhythm Generator 16 pin DIL 800p TIP32A 58p Sop 74154 150p *NiC1310P FM Stereo Dec 14 pm DIL 190p *BC149C 10p 256034 160p 7422 22p 74155 90p CD4040AE 120p TIP32C 82p *MC1351P Lim /Del. Aud Preamp 14 pm DIL 97p *BC157 119 .TIP33A 90p 256107 65p 10p 7423 37p 74156 90p CD4042AE 90p MC1495 Mulupher 14 pm DIL 300p *BC158 TIP33C 115p 2N6247 190p ZENER 14 pin 100p *BC159 Imp (Comp to 2530551 2 7V to 335 7425 30p 74157 90p CD4043AE 100p *MC1496L Bal Mod Demod OIL *BC169C 12p TIP34A 115p *MC1596 Mod / Demond TO OIL 300p 2N6254 130p *400mW Op 7427 37p 74158 140p CD4046AE 140p Bal *BC172 11p TIP34C 160p *MC3340P Electronic Almenualor 8 pin OIL í60p 2N6292 65p 1W 18p 7428 36p 74159 190p CD4047AE 100p BC177 18p TIP35A 225p *MFC40008 1 /4W Audio Amp PCB 90p 40360 40p 7430 18p BC178 17p TIP35C 290p 74160 120p CD4049AE 63p *NE540L Audio Pwr driver T099 140p TIP36A 270p 40361 45p 7432 36p 74161 120p CD4050AE 57p 40p BC179 1ßp 40362 45p NOISE NE555 Timer 8 pm DIL *8C182 12p TIP36C 340p 7437 36p 74162 120p CD4054AE 120p NE556 Dual 555 14 pm DIL í00p TIP41A 65p 40364 120p 110p NE561 PLL wnh AM Demod 16 pm DIL 425p *BC183 12p 40409 65p 7438 36p 74163 120p CD4055AE 140p 9C184 13p TIP41B 70p 7440 19p 74164 120p NE562 PLL wnh VCO 16 pin DIL 425p TIP41C 78p 40410 65p CD4056AE 135p NE565 PLL 14 pm OIL 200p BC187 Sop 40411 300p *BC212 1 TIP42A 70p 7441 75p 74165 220p CD4060AE 130p NE566 PLL Fun Gen 8 pin DIL 200p Ip 40594 8Bp *BC213 10p TIP428 78p 7442 70p 74166 160p CD4069AE 27p NE567 PLL Tone Dec 6 pm OIL 200p 40/V 97p *BC214 TIP42C 82p BRIDGE 7443 140p 74167 340p CD4071AE 27p 2567 Dual 567 16 pm DIL 370p BC478 g: TIP2955 78p 7444 140p 74170 250p CD4072AE 27p SN72710 Draft Comparator 14 pon OIL SOp BCY70 18p *T1593 30p RECTIFIERS *SN72733 V,deo Amp 14 pm DIL 12Op 7445 120p 74173 160p BCY7 1 22p *ZTX108 10p CD4073AE 30p *SN76003N Pwr Aud Amp wnh in! H5 16 pm DIL 245p BD124 130p *770300 13p *14 50V 22p 7446 100p 74174 120p CD4081AE 21p *SN76008 10W Amp m 4 ohms 5 pet Plasrc 250p FET. BD131 36p *ZTX500 15p 100V 24p 7447 85p 74175 85p Pwr woth nit HS 16 DIL 140p 244 25p lA CD4082AE 27p *SN76013N Aud Amp pin BD132 40p *ZTX502 18p *Elf *14 200V 28p 106/ Amp in 8 5 pin Resto 25Op *MPF 102 4op 7448 SOp 74176 120p CD4093AE 95p *SN76018 ohms *60135 48p 254574 190p *14 400V 30p Pwr Aud Amp with ml HS 16 pin DIL 140p *MPF 103 40p 7450 18p 74177 100p CD4510AE 130p *SN 76023N *80136 50p 25697 22p *1A 600V 36p *SN76033N Pwr Sud Amp with int HS 16 pm DIL 230p *M PF 104 40p 7451 20p 74179 160p *00139 52p 25698 45p *2A 50V 30p CD4511AE 160p *TAA621A Aud Amp for TV OIL 225p *MPF105 40p *80140 58p 25706 20p *2A 100V 35p 7453 20p 74180 110p CD4516AE 112p *TAA661B FM IF Amp-Limiter /Del GIL 120p *253819 25p BDY20 125p 2N708 20p *2A 200V 4Op 7454 18p 74181 298p OIL 253820 CD4518AE 130p *TBA641B Audio Amp 250p BDY56 200p 25918 40p 50p *2A 400V 45p 7460 18p 74182 S2p CD4528AE 120p *T8A651 Tuner & IF Amp 16 pm OIL 200p 8E115 22p 25930 18p 2N3823 57p *3A 200V *TBA800 Audo Amp 90p *25545/ 40p 60p 7470 36p 74185 150p MC14553 525p 5W OIL 8F167 23p 251131 1Bp 600V 72p *TBA810 7W Audio Amp OIL 100p *2N5458 40p 3A 1 251132 18p *4A 100V 7472 30p 74186 920p BF 70 23p *255459 40p (14p *TBA820 2W Audio Amp OIL 80p 8F173 25p 251304 45p *4A 400V 90p 7473 34p 74190 160p TEXAS 75 SERIES *7042020 20W Audio Amp OIL/DIL 325p 2N5485 40p 7474 34p 74191 160p BF177 26p 201305 45p 6A 50V 9op 75107 160p 602240 Prog Timer. Counter 16 pm DIL 370p 6E178 28p 201306 45p 6A 100V 96p 7475 45p 74192 120p *Z5414 TRF Radio Receiver TO-18 110p 75450 120p 0E179 33p 251307 45p 6A 200V 108p 7476 36p 74193 160p BF180 33p 251308 40p 6A 400V 120p 75451 72p Basic dala sheets on above a1 20p each +S A E 7480 50p 74194 120p 13E184 22p 251309 40p 104 400V 2709 75452 MOSFET. 7481 95p 74195 95p 72p *BF194 10p 251613 25p 254 400V 400p 75453 72p OPTO- ELECTRONICS *BF195 9p 201711 25p 3N127 96p 7482 90p 74196 120p 3514(1 95p 75454 Phototransistors L D. Ro *BF196 14p 251893 30p 7483 90p 72p 35141 95p 74197 120p OCP70 75p ORP12 70p *BF197 15p 252102 55p 7484 110p 252219 2Op 3N187 180p 74198 250p OCP71 75p 13f 200 32p 4060.7 63p 74199 250p TEXAS DTLs 120p ORP60 329 202222 20p 7485 120p 2N5777 45p BF257 40673 63p 7486 34p 74221 160p 9:50 36p ORP61 75p Elf 258 2N2369 140 936 *BFR39 30p 202484 30p 7489 '320p 74251 140p 40p LEDS o 2" Red 18p *8FR40 30p 252904/A 25p TRIACS 7490 40p 74265 90p 946 40p TIL209 Red 16p Green 36p *BFR41 30p 252905-A 25p Plafbc An,p 7491 85p 74278 290p 955 60p 'TIL211 Green 36p Yellow 36p *BFR79 30p 2N2906 -A 24p Volts 30p *2529268 7p UJT. 3 400 85p 7492 55p 74279 140p 962 36p TIL32 Infrared 75p Tri-state Red *BFR80 400 /Green *BFR88 30p *2529260 7p *TIS43 34p 6 99p 7493 40p 74283 190p 963 40p 5 500 107p Off 160p BFX30 34p *2029260 10p 2N21611 95p 10 400 120p 7494 90p 74290 150p BFX84 30p *2929260 12p 252640 45p 10 500 140p 7495 70p 74293 150p MEMORIES SEVEN SEGMENT DISPLAYS BFX85 30p *2N2926G 12p *254871 54p 7496 84p 74298 200p BFX86 30p 253053 18p ' 400 160p 2102 RAM 250p 3015F O.3" 160p '5 500 18op 7497 340p 74365 150p Xciton: BFX87 30p 253054 SOp 2107 RAM 1000p DL704 O 3" Red 140p O 3" Green 160p BFX88 30p 203055 5Op 40430 130p 74100 120p 74366 150p 411669 130p 2112 RAM 450p DL707 O 3" Red 140p O.3" Green 160p BFY50 lap 253439 67p OIAC 74104 65p 74390 200p BFY5 1 15p 253442 14Op PUJT 2513 ROM 850p DL747 0.3" Red 225p O 6'" Green 225p 74105 65p 74393 225p 2602 RAM 250p BFY52 16p *2N3565 30p 256027 68100 30p 74107 36p X887 ROM 1600p Driven: 75491 84p. 75492 96p VOLTAGE REGULATORS - FIXED - PLASTIC BT106 PROGRAMMABLE SHUNT SCR -THYRISTORS 1A /700V Stud 110p NEW ADJUSTABLE VOLTAGE 1 Amp Positive 1 Amp Negative REGULATOR REGULATOR. Positive 5V 7805 140p 5V 7905 200p Features excellent stability over LM317 1A 50V TO5 40P 8101 Plastic 63p T0220 3 pin Plastic Current In 12V 7812 140p 12V 7912 200p 1A100V TO5 429 temp., wide operating current *MCR101 excess of 1 Amp. Output voltage 15V 7815 140p 15V 7915 200p 1A400V 105 45p range and low o/ p noise. The o / p O 5A/15V TO-92 range 2V to 37V Requires only 2 18V 7818 140p 18V 7918 200p 1A600V T05 7op 25p voltage Is set by 2 R's between 3 2N3525 R s to set the O/P voltage Line & 24V 7824 140p 24V 7924 200p 3A100V Stud to 30 volts. TL430 can replace 65p TO-66120p Load regulation better than flied LM309K 1 Amp 5V TO3 140p Zener Diodes In many applications LM323K 3A 5V 700p 3A400V Stud 759 2N4444OV regulators LM309H 100mA 5V TO5 75p providing Improved performance. 7A100V TO5 +HS 84p 8A /600V Plastic 185p Price £3.25. Data O 20 + SAE. TBA6258 12V O 5A TO5 120p 7A400V TO5 +HS 90p *2N5060 TL430 -- 3 Terminals -- T092. 85p. VARIABLE VOLTAGE REGULATOR 8A 50V Plastic 1309 O 8A /30V TO-92 34p 723 2V to 37V 150mA 14 pm DIL 45p 12A400V Plastic 1609 *2N5062 16A100V Plastic 1609 DUAL VOLTAGE REGULATOR 0.8A /100V TO -92 37p VAT RATES: All items at 8% EXCEPT where 1468 ± 15V 100mA 16 pm DIL 300p. 16A400V Plastic 1809 *2N5064 (Adjustable by resistors from ± 8V to ± 2OVI 16A600V Plastic 220p 0.8A/200V TO -92 40 marked* which are at 1212'v LOW PROFILE OIL SOCKETS BY TEXAS Meumunl Order f2 Mail Order Only LTD. 8 pIn 13p, 14 pin 14p, 16 pm 15p, 18 pin 36p, 22 P &P 209 TECHNOMATIC pm 40p, 24 pm 50p, 28 pm bop, 40 pm 75p. Govt., Colleges, etc. orders accepted. 54 SANDHURST ROAD, LONDON, NW9 Please add VAT to total TN: 01 -204 4333. Telex 922800 THE O - EN DOOR TO QUALITY ISSUE NO. 4 NOW READY - WITH NEW SECTION ON METERS Catalogue No. 8 (Issue 4, up- dated) offers This catalogue - Electrovalue 144 pages items from advancedopto- electronic components to humble (but essential) washers. Many things listed are very difficult to obtain elsewhere. The company's own computer is programmed to expedite delivery and 40p maintain customer satisfaction. Attractive discounts continue on many Post paid purchases; Access and Barclaycard orders are accepted. inc. refund voucher worth i' 40p + FREE POSTAGE on all C.W.O. mail orders over £2.00 list value

1 CTRp W. (excluding V.A.T.) in U.K. If under, add 1 5p handling charge. E1.E : Postal commumcabons to Dept WW4, 28 ST. JUDES ROAD, ENGLEFIELD 1. GREEN, EGHAM, BURREYTW20 OHE. Phone Egham 3603 Telex 264475 Shop hours 9 -5 30. 1 pm Soro., both branches Catalogue NORTHERN BRANCH: 680 aumage tan*. Bumege. M.ncha.ter M19 INA. P,,ii 10fi1 4'4? 494',

www.americanradiohistory.com 132 Wireless World, April 1977 RELAYS- UNISELECTORS- SWITCHES MINIATURE PLUG -IN RELAYS (Siemans /Varley) with perspex dust cover and base. 6 -1 2- 24 -48v D C In Stock 2 c/o 50p: 6 make 60p 4c /o 75p: P & P 10p MINIATURE (P.C. Mounting) Wilmslow S.T.C. with dust cover 2 c / o (18 / 24v) 45p P. P. 10p 4c /o(24 /36v)50p P. P 10p 6 c/o (36 / 48v) 75p P. P 10p CLARE -ELLIOTT MINIATURE RELAYS (Hermaucally sealed) 2 c/o 675 ohm Audio 24v D.C. Coils (22 x 22 e 10 mm) 76p I.T.T. 240v A.C. Plug-In RELAYS (with perspex covpr) 10 amp contacts 2c /o65p3 c/o 75pPP. 10p THE firm for speakers! REED RELAY 3 MAKE (50 x 20 x 20 mm) 3500 ohm coil 24v D C 50p Baker Group 25, 3, 8 or 15 ohm . £13.00 Goodmans 12P 8 or 15 ohm .... £16.50 REED SWITCHES (1 MAKE) Baker Group 35, 3, 8 or 15 ohm . £14.50 Goodmans 12P -D 8 or 15 ohm £ 18.75 Type 1 (18 x 3 mm) 12 for £1 ... Type 2 (48 x 5 mm) 8 for E1 Baker Deluxe 8 or 15 ohm £17.50 Goodmans 12P -G 8 or 15 ohm ... £17.75 G.E.C. RATCHET RELAYS Baker Major. 3. 8 or 15 ohm £15.00 Goodmans Audiom 200 8 ohm £ 14.95 910 ohm Red or Blue Cam. E1 P.P. 20p ... UNISELECTORS 25 WAY Baker Regent. 8 or 15 ohm £12.50 Goodmans Axent 100 8 ohm £8.50 5 Full Wipe P P Bank 75 ohm £5.50 50p Baker Superb. 8 or 15 ohm £22.50 Goodmans Axiom 402 8 or 15 ohm £22.00 6 Bank Full Wipe 75 ohm £6.25 P P. 50p Celestion HF1300 8 or 15 ohm 8 Bank Full Wipe 75 ohm E7.50 P P 50p ... £7.50 Goodmans Twinaxiom 8" 8 or 15 ohm 12 Bank Half Wipe 68 ohm £6.50 P.P. 60p Celestion MH 1000 horn. 8 or 15 ohm SMALL 12V UNISELECTORS 4 Bank 11 may £2.50 P P £10.60 50p £13.50 Kef 127 £8.50 D.C. SOLENOIDS 24v (Cont Rated) Coles 400 1 G super tweeter 10Ib Pull 20 mm Stroke. Size 50 e 48 e 42 mm .... £5.90 Kef 115 £10.75 75p P P. 15p Coles 400 1 K super tweeter .... £5.90 Kef 8110 £10.95 FOOT SWITCH "SQUARE -D" H.D. Decca London and X over £38.45 20 A Make / 10A Break at 240v A C Kef B200 £11.95 600v A.0 /D. C. Max £4 P P. 75p Decca DK30 and X over £25.25 Kef B139 £24.95 BURGESS MICRO SWITCHES (VCSP) EMI 5" Mid range £3.50 Single Pole c/o 8 for E7 P P. 10p Kef DN8 £2.75 2 EMI 61/2" d /cone roll surr. 8 ohm £3.95 H.D. HONEYWELL MICRO- SWITCH (contacts 2 N 0 Kef DN12 £7.25 N C '/x turn action complete with roller actuator 20 amp) EMI 8 x 5. 10 watt. d /c. roll /s 8 ohm £3.95 £2 P P 35p Kef DN13 £4.95 DECADE (THUMBWHEEL) SWITCHES EMI 14" x 9" Bass 8 ohm £12.50 6mm Digits. 50p each. Bank of 8 with mounting brackets E3 Richard Allan HP8B 8" 45 watt .. £12.50 Elac 59RM 109 15 ohm. 5911M 1148 ohm P P 20p Richard Allan CG8T 8" d/c roll /s £7.95 DECADE INDICATOR SWITCHES with plus & minus £3.50 Push Buttons. 6 mm digits 75p each P P. 10p Baker Major Module, each £18.00 Elac 6!/2" d/c roll /s 8 ohm £3.95 Also m BCD Goodmans Mezzo Twinkit. pair £51.95 KEY SWITCHES '1000' TYPE Fane Pop 15 watt 12" £5.75 4 c/o each way locking 60p P. P 10p Goodmans DIN 20, 4 ohm, each £ 15.75 6 make each way locking 60p P. P 10p Fane Pop 33T 33 watt 12" £9.95 P P way. 1 £1.25 15p Helme XLK35, pair £26.75 Bank of 4 4 c/o each biased Fane Pop 50 watt. 12" £12.50 Helme XLK40, pair £38.50 MULTICORE CABLES Fane Pop 55. 12" 60 watt £16.95 CABLE 8 CORE RIBBON (RAINBOW) Fane Pop 60 watt, 15" £19.95 Helme XLK30, pair £21.95 B x 14/76 Forming 1/2m wide strip 10m- £1.50: 50m- E6.50: 100m- £12.00 P P. 1p per Fane Pop 70 watt 15" £21.75 Kefkit 1, pair £59.50 metre Fane Pop 100 watt. 18" £33.95 Kefkit Ill, each £56.00 5 CORE H.D. CABLE 5 x 70/76 P V C Black Outer PVC 0 . 1/2 in Fane Crescendo 12A or B, 8 or 15 ohm Richard Allan Twinkit, each £13.95 t0m- E2.50: 5Om -£12: í00m- £22.50 P P 2p per metre £42.95 Richard Allan Triple 8. each £20.75 P C INS 6 CORE ARMOURED 6 x 40/ 76 V Fane Crescendo 15. 8 or 15 ohm £54.95 Richard Allan Triple 12, each . £25.95 Tubing 0 D % in Outer Sheath -Flexible Galvanised Richard Allan Super Triple. each £29.50 t0m --E3: 50m -£14: 100m -E25. P P 2p per metre Fane Crescendo 18. 8 or 15 ohm £75.95 6 x 7/76 ODD 6mm. 6 CORE SCREENED Fane 8071 8" d /c, rolls /s, 8 or 15 ohm Richard Allan RA8 kit, pair £37.80 t0m- E1.50: 50m-- E6.50: 100m- £12.00 P.P. 2p per metre £5.40 Richard Allan RA82 kit. pair £59.40 O D 36 x 7/ 76 (36 colours) 36 CORE SCREENED Fane 801T 8" d/c roll /s 8 ohm £9.50 Wharfedale Denton 2XP, pair £23.25 11m m P 2p per metre lOm -E3: 50m -£14: 100m -£25 P Goodmans 8P 8 or 15 ohm £6.50 Wharfedale Linton 3XP. pair £34.25 VARIOUS Goodmans 10P 8 or 15 ohm £6.95 Wharfedale Glendale 3XP kit. pair £49.50 E.H.T. MODULES. Input 190 -260v 50 HZ Output 13 7Kv, All Radford, Gauss, Castle, Watts, Eagle, Lowther, Peerless Tannoy PK @ 0.50 m /a. (150 x 95 x 70mm) E12. P.P. El Jordan AIR PRESSURE SWITCH 0-10 lb Variable units in stock Switch Contacts 15 amp. Change -Over E1.50 P.P. 25p Prices correct at 12/1/77 MYRIA MEGOHMMETER TYPE 35A. 20 -200K MEG /OHMS 50Ov test. Excellent condition. E45, cari £2 50 ALL PRICES INCLUDE VAT EQUIPMENT COLLING FANS (System Papst) Precision Cabinets wadding, Vynair, Crossovers etc. made. Silent running, 110v 50 Hz. 12Omm e 1 20mm. £5. P P 50p. Send stamp for free 38 -page booklet

"BLEEPTONE" AUDIO ALARMS " "Choosing a Speaker" 12v DC 50p P.P. 10p FREE with all orders over £10 - GEARED MOTORS 230v A.C. (Int. Rating) 110 r.p m. £2.25 P.P. 75p Hi-Fi Loudspeaker Enclosures Book MAGNETIC COUNTERS All units are guaranteed new and perfect 6 digit 48v D C (Non - Reset) 92 x 32 x 22 m New /Boxed E1 ea P P. 15p Prompt despatch

3 DIGIT RESET COUNTERS (240v A C I Veeder -root £1.75 P P 25o Carriage: Speakers up to 12" 60p; 12" £1; 15" £1.75; 18" £2.50 D.C. POWER SUPPLIES Input 240v A C Kits £1 each (£2 per pair). Tweeters & Crossovers 33p each. TYPE 1 20v D.C. at 1 amp. Fully regulated 1 55 x 1 55 x 75 TITI totally enclosed £5 P.P. 75p TYPE 2 20v D C at 500 m /a stabilised on open chassis t 70 e 100 mm £2.50 P.P. 75p AUDIO P.S.U. WILMSLOW PHILIPS MOBILE RADIO Input 240V A C Output 32V at 1 5Amp D C E5.25 P P Dept. WW 75p TELEPHONE HANDSET with Press to Speak switch Loudspeakers & Export Dept: Swan Works, Bank Square, £1.50 P P 25p 2000 W. AUTO TRANSFORMERS. Tapped Wilmslow, Cheshire SK9 1HF. Discount Hi -Fi, PA, etc.: 10 Swan 100, 125 200. 225/250v New in wooden boxes E15 Street, Wilmslow, Radio, Hi -Fi, TV; Swift of Wilmslow, 5 Swan P P £1.50 29599 (Hi -Fi, PLEASE ADD 8% V. A T Street, Wilmslow. Tel. (Loudspeakers), Wilmslow etc.), Wilmslow 26213. J. B. PATTRICK 191/193 LONDON ROAD Access and Barclaycard orders accepted by phone ROMFORD, ESSEX RM7 9DJ ROMFORD 44473 WW -013 FOR FURTHER DETAILS

www.americanradiohistory.com Wireless World, April 1977 133 Appointments

DISPLAYED APPOINTMENTS VACANT: £7.50 per single col. centimetre (min. 3cm). Advertisements accepted up LINE advertisements (run on): £1.10 per line, minimum three lines. April 4, to 12 noon Monday, sox NUMBERS: Sop extra. (Replies should be addressed to the Box Number in to the for the May issue, subject advertisement, c/o Wireless World, Dorset House, Stamford Street, London SE1 9LU.) space being available. PHONE: Eddie Farrell on 01 -261 8508 Classified Advertisement Rates are currently zero rated for the purpose of V.A.T. In I Careers in Professional Electronics

Your experience could open the door to a range of interesting and rewarding opportunities in the Design, Production or Service departments of a Company whose products complement thé most advanced modern electronic techniques. For more information apply in confidence to :- John Prodger, MARCONI INSTRUMENTS LIMITED Longacres, St. Albans, Herts. Tel : St. Albans 59292 A GEC Marconi Electronics Company

UNIVERSITY REA H E ALT(TH UNIVERSITY XI0rdShirej1AUTHORITY EACHING) OF SOUTHAMPTON OF ABERDEEN Department of Chemistry INSTRUMENT ELECTRONICS Churchill Hospital TECHNICIAN TECHNICIAN required for Department of Medical Physics required to join a section carrying out for duties concerned mainly the maintenance and repair of Medical Physics Technician with the development of digital and scientific, electronic and optical analogue circuitry for prototype instruments. equipment used in clinical /research projects and the maintenance/repair Applicants should have a technical Grade III (Electronics) qualification of HNC or ONC or of medical electronic equipment equivalent with several years' rele- £2961.0043834.00 + £312.00 Applicants should hold ONC or equi- vant experience in electronics and /or valent qualification scientific instruments. and have had previous experience in electronics. The appointment will be made at To work in the Department of Radiotherapy and Oncology on the grade 5 on salary scale design and building of new circuits and the maintenance and For suitably qualified candidate £2889 -E3367 (which includes two updating of existing radiotherapy equipment. HNC or equivalent salary on scale £2455 -E2788 linclu- supplements under Government pay in electronics necessary. sive of supplements under Stages 1 A policy). 2 of incomes policy). Applications giving details of age. qualifications and experience and the Applications giving details of age names and addresses of two referees, Enquiries to Mr. R. J. Thorne, Chief Technician, Department of qualifications and experience should should be sent to Mr. D. A. S. Radiotherapy & Oncology, Churchill Hospital, Oxford OX3 7LJ. reach the Secretary. University Office Copland, The University. Southamp- Regent Closing date 25th February, 1977. Walk, Aberdeen AB9 1 FX. by ton S09 SNH, quoting reference 31st March and quote Ref. No - 1 1 i MW 36/77, 170951

www.americanradiohistory.com Appointments 134 Wireless World, April 1977

WANTED RADIO- TELEPHONE BENCH ENGINEERS AND FIELD SERVICE CALIBRATION ENGINEERS TOP SALARIES FOR TOP ABILITY

We need people who have experience in ENGINEERS V.H.F. Mobile Radio-Telephone. We are a young, friendly, independent company, who are currently the busiest and MEASURE YOUR SUCCESS BY OURS fastest expanding radio- telephone firm in London - we reward hard work with high EMI's commitment to excellence in its electronic products is incentives. achieving best ever sales and creating many new opportunities for Ring now, with details of past experience expansion and development. ask for Mike Rawlings or Bill Clarke We depend upon very high standards of quality assurance, so we 30 Boundary Road, London NW8 Telephone: 01 -328 5344 are looking for professionals who work to these standards and who have the ability to extend them still further. The work is varied and involves the calibration and maintenance London of electronic and electro- mechanical test equipment, covering a wide range of test and measuring techniques such as optical, Communications thermal, digital and computer. (Equipment) Ltd Qualified to City 8 Guilds (full certificate), ONC or equivalent in electronics, candidates should have experience of fault diagnosis and current measuring techniques. Knowledge of micro -wave techniques, and /or the utilisation of automatic test equipment would be an advantage. APPOINTMENTS To appreciate the satisfaction of working to EMI standards, come and see for yourself. You can also be sure that the salaries and IN benefits we offer- including the security of working for a highly ELECTRONICS successful organisation - reflect our awareness of the importance of your skills. Take your pick of the permanent posts in: For further details and an application form, please MEDICAL telephone or write to : Barry Page, Personnel Department, MISSILES - EMI Limited, 135 Blyth Road, Hayes, Middlesex. COMPUTERS - COMMS MICROWAVE - MARINE Tel : 01 -573 3888 ext. 639 or Record -a -Call anytime on HARDWARE - SOFTWARE 01 -573 5524. For expert advice and immediate action on career improve ment, 'phone, or write to. EMI Mike Gernat BSc TTechnoma& The international music. electronics and leisure Group. (70811

11 Westbourne Grove London W2 01 229 9239. 7098

Re -ad vertisemen r LONDON COLLEGE UNIVERSITY COLLEGE OF PRINTING ITN OF NORTH WALES Faculty of BANGOR Visual School of Physical and Communications Molecular Sciences Department of Photography Film and Television SENIOR ENGINEER ELECTRONICS TELEVISION - INSTALLATION PROJECTS TECHNICIAN £5,712 p.a. GRADE 5 TECHNICIAN/ Applications are invited for the An engineer is required to work as part of a newly post of Electronics Technician Grade 5 in the above mentioned School. ENGINEER formed team responsible for installation projects. The successful applicant would be Applications are invited for the above The work will be varied and will involve a wide concerned with the development, post in the expanding Television range of broadcast equipment. The successful construction and maintenance of Department of Photography, Film specialised electronic equipment for a and Television. applicant will have a good knowledge of broadcast wide range of research work and teaching in the School. Candidates should be conversant and sound equipment and techniques. Current Applicants should have had sever- with '/z ", 3/4" and 1" black and white projects include the replacement of major studio al years' relevant practical experience and colour equipment and be capable sound desks, telecine sound followers, multi track coupled with theoretical knowledge, of electronic maintenance. Exper- preferably to H.N.C. standard or ience in professional broadcasting recording and communication systems. equivalent. would as well an be an advantage, as gained either with a Salary at an appropriate point on interest in experimental video work A broad base of experience, scale: £2,889- £3,367 per annum. The successful applicant will be broadcaster or a manufacturer is essential. Pension Scheme. expected to assist in running studio Applications (two copies), giving productions, and video tape editing. In addition to practical experience, academic details of age, education and exper- Salary scale £3190 -£4702 inclusive achievements will be taken into account. ience, together with the names and (ST1 / 2). addresses of two referees should be Candidates should telephone the Personnel Assistant Registrar Application forms. returnable within submitted to the (Personnel), University College of 14 days, obtainable from the Senior Department of Independent Television News Ltd. North Wales, Bangor, Gwynedd LL57 Administrative Officer at the college. 3217. on 01 -637 3144 quoting reference 2DG. I70bO (70881 (70531

www.americanradiohistory.com Wireless World, April 1977 135 Appointments

ELECTRONIC DESIGN/ DEVELOPMENT ENGINEERS FERRANTI OFFERS YOU FREEDOM

freedom to create. Over the years leading design and development engineers have been attracted to Ferranti by our reputation for truly innovative engineering and together they have formed specialised teams involved on a variety of sophisticated projects related to the Tornado, Sea Harrier, Jaguar, Nimrod 2 and other front line aircraft.

We now require additional engineers to join these teams engaged on the creative work of designing and developing airborne radar, laser and inertial navigation systems and their associated test equipment.

Engineers are required in the following technical fields: - Digital and analogue electronic circuitry design. Design and application of small digital computers. Microwave and laser techniques. Advanced instrument design including gyroscopes of inertial quality. Design of small mechanical structures and analysis of stress.

In addition to the above we have vacancies for production engineers with either electrical or mechanical backgrounds in these fields.

Applicants should have some design /development experience to offer in avionics and a desire to expand their experience to project leader level.

Edinburgh, with its outstanding facilities for education, housing, sport and entertainment, is one of the ideal cities in Europe in which to live, work and bring up a family. And to make moving here easier, we pay realistic relocation expenses. Salaries are negotiable and the Company operates a contributory pension and life assurance scheme.

Apply in writing, with full details of experience and qualifications to Staff Appointments Officer, Ferranti Limited, Ferry Road, EDINBURGH, EH5 2XS. Please quote Ref. WW/ 1.

(7000)

www.americanradiohistory.com Appointments 136 Wireless World, April 1977 Thai rElectronicTest Tech nicians- Rollytted Inc School of Ma erials Science and Physics put your skills to the test! Electronics Technician Here at Havant where we currently manu- . As well as a wide range of fringe benefits facture large systems we're looking for Technicians, we also offer generous relocation expenses to (Grade 4) male or female, with experience of sophisticated this attractive part of the south coast which Applications are invited for a techni- electronics, and the ability to diagnose and rectify provides outstanding social and recreational cian for the electronics workshop who malfunctions on a complex computer system. facilities. will be required to construct, maintain and repair a You're probably an experienced Technician If you feel this opportunity is suited to your variety of electronic equipment for teaching and research. with ONC/HNC in electronics or relevant Service ability and experience phone or write for an A good understanding and a flair for experience in digital equipment. application form to: Marjorie Menereau, electronics is needed., Candidates should Starting salaries are very competitive, Personnel Officer, IBM United Kingdom Limited, have an ONC or OND or equivalent qualification and at least together with first -class working conditions. Langstone Rod, Havant, seven years relevant experience. You may be expected to work on a double shift Hants. Tel: Haavaa nt 6363. Salary scale: E2835-£3216 including London basis for which an attractive premium will be paid. Quoting ref: WW/92838 IBM weighting plus personal allowance e. 5% of gross pay: min. £2.50 max. £4.00). uuunmn1n111111111111i10=1.11J118,.. !11Pn" r r!ë . . Further particulars and form of . ,uu 1 ,.. '7:. r. ." :-- :: application may be obtained from 'I'T qlq II ;;° I r the o- Staffing Officer, Thames i li -_ I1' 1 1 Polytechnic, Wellington Street, I N : London, SE18 6PF, to whom I l !' ;ir of l 1. ' / e ;1 - %:, completed 1 lIElti1llllli 11 i ,I applications should be ^ ,..r I ú t returned by 22 March, 1977. I ilr''IIi 'ilPnitl Ii llllil i 1 ip1,,,ml4pmgnt iaielill "'i'l, II II IIPPI °'fPi111IN mvp mtt I II '" II 11 1 I .

Join the leaders in Development Telecine Development Rank Cintel - a division of Rank Precision Industries - has Engineers developed the world's most sophisticated telecine machine, and is currently engaged in a vast export programme. These Consumer Electronics achievements result from concentration on technical superiority Hastings and excellence of quality, and demand the highest standards of engineering at all levels. In order to maintain and develop our Accepting that good Development technical advantages, we now have a number of progressive Engineers are in universal demand, we positions for the following specialists: nevertheless believe that our vacancies here at Hastings, open to both men and women, R & D Electronic Engineers offer attractions second to none. Such as .. . To apply their expertise to circuit design, using analogue and * Technically challenging, professionally digital techniques in audio, video and servos. Candidates, men or rewarding, personally satisfying work on : women, should have good practical experience and be qualified to Advanced colour television and audio- at least HNC level. product design, incorporating the latest concepts in digital and integrated Engineers circuitry, microprocessors, and L.S.I. Then Test there's the development of Teletext, (Broadcast Equipment) Viewdata - the list is almost endless. test specifications * Opportunity to become involved with a To test and fault -find sub -units and PCB's using successful company, which intends to and a traditional range of test equipment. Candidates, men or will have accelerate its growth and build on its women, should be qualified to T4 level, and preferably already high reputation for quality and some work experience in electronics testing. innovation. * The probability of overseas travel. The Mechanical Design certainty of a good salary, generous holidays, "big company" fringe benefits, Draughtsman Pension and Life Assurance schemes, subsidised sporting and social facilities. To design and develop film and tape transports and associated instruments. Candidates, men or women, should be qualified to at * Assistance, where appropriate, in moving least HNC Mech Eng., and have a number of years' experience in to this pleasant, socially attractive, designing precise and dynamic devices. healthy coastal area, where housing is available and more reasonably priced, yet All positions carry good starting salaries - with excellent prospects conditions and benefits are the amenities of the "big city" are for career development. Working within easy reach. first -rate. 4 if you a please contact Sounds good? Then, have degree To apply or HNC, plus experience in a relevant Ian Waterhouse speciality, write giving brief personal and Personnel Manager career details (or phone for Application Rank Cintel Form) to George Greaves, Personnel Watton Road 9 t s :- ref OUEEN Officer, ITT Consumer Prociucts (UK) Ltd., Ware, Herts. AWARD TO Theaklen Drive, Hastings, E. Sussex. Tel. 0920 3939 :NDUSTRY 7080 Tel : Hastings (0424) 437061. RANK CINTEL TV Radio Stereo ITT

www.americanradiohistory.com Wireless World, April 1977 137 Appointments

INDEPENDENCE &WORLD Applicants will need professional qualifications of at least HNC level and a good knowledge of TRAVEL IN A CHALLENGING semi -conductor circuitry and ideally have FIELD FOR EXPERIENCED experience of equipment such as high power radar systems. They will also need personal qualities which will enable them to deal with Service & Installation various senior members of organisations and Engineers act as "ambassadors" for our company. We offer excellent progressive salaries with full The MEL Equipment Company Limited, the expenses and allowances, an annual bonus, professional electronic division of the Pension and Life Assurance schemes and at least International Philips Group produce the 4 weeks and 3 days annual holiday entitlement. advanced linear accelerators used in many of Where candidates do not live in the Crawley the major hospitals throughout the world for the area relocation will be necessary. Assistance treatment of cancer. will be given, including nomination for rented The equipment is highly sophisticated and accommodation from offers those involved with installation and field Crawley New Town support the opportunity to develop skills in this Commission. Crawley is an innovative area. , established New Town situated on the Surrey/ Sussex borders offering excellent educational and recreational facilities, including a local sports centre and swimming pool. if If you would like to take this %, ef/I; opportunity to work I on vital, highly sophisticated equipment please write or telephone for an application form to Barbara Newman, Personnel Officer, M.E.L. Equipment At present we are looking for self reliant, Company Limited, Manor Royal, Crawley, Sussex. : adaptable engineers who would appreciate the Tel 0293 28787. challenge and rewards of working on advanced medical equipment. Spending periods of up to 4 months duration overseas they would work in important medical centres installing and servicing the equipment. 000

www.americanradiohistory.com Appointments 138 Wireless World, April 1977

Electronic Research OXFORD INSTRUMENTS & Design DEVELOPMENT W. London To £4,600 Our client is the Development Division of a major and highly successful international company. To ENGINEER ensure continued leadership in the field of Special Application Control Systems, 5 additional Applicants should be practical, engineers are needed to strengthen small teams developing new and advanced products.

innovatory electronics engineers Applicants (male or female), aged 21- , should in have a Degree or HNC and experience of Analogue/ with experience r.f., and pre- Digital Circuit Design. A knowledge of Micro - cision analogue circuit design. A processors, Hydraulic Systems or Scientific Programming would be an advantage. knowledge of digital techniques, The posts' carry a good basic salary and other "big company" benefits. In addition, there are would be useful, but is not a prime excellent opportunities for promotion on merit requirement. within an expanding organisation. For further information, please contact Mike Gernat. The successful applicant will be a key member of a small new group chnomark, TEngineering and Technical Recruitrnenr with multidisciplinary interests. He 5 -11 Westbourne Grove, London W2. or she will primarily supply the Telephone 01 -229 9239 7'70 electronics expertise required for the development of sophisticated new instruments, but will also be ELECTRONIC DESIGN expected to become involved in ENGINEERS other aspects of innovation. The DO YOU want to earn a better than average salary? DO YOU want to join a go -ahead company? ability to work with minimal super- DO YOU have experience in the design of audio to UHF circuitry or vision and to be self- motivated is Assembly level programming of mini or micro processors? DO YOU like working with the minimum of supervision? essential. YOU DO? Then apply to.

Salary negotiable according to age The Technical Director Burndept Electronics (ER) Ltd and experience. St. Fidelis Road Erith, Kent Contact Dr. Peter Hanley, tele- Erith 39121 170621. phone Oxford 41456 or write to The Oxford Instrument Co., Osney Mead, Oxford 0X2 ODX, to arrange an interview. (7064)

TOWN CLERK & CHIEF EXECUTIVES DEPARTMENT

CAB LE SYSTEMS CANADIAN LIMITED Administrative Officer SYSTEMS ENGINEER (Telecommunications) CANADA £4836 -£5142 We have an opening in our London, Ontario, Engineering Office, for a shirt To provide and maintain an effective integrated telecommuni- sleeves professional engineer who has a strong background in Video Engineering. A working knowledge of R.F. Transmission, preferred in C.A.T.V. cations service for all Council establishments and to ensure would be an asset. You would be a highly results orientated individual who will that the service fully meets the Council's current and enjoy the challenge of making your place in a small team of engineers. anticipated requirements. Canadian Cablesystems is a company with ten C.A.T.V. Systems in Ontario with Applicants must have a wide knowledge of Post Office and over 400,000 Subscribers. commercial communication installations. Salary will be in the range of S20.000 per annum. If you wish to pursue this position within our organisation please send your Application form, returnable by 1st April, and detailed résumé in confidence to: job description from Chief Personnel Officer, Town Hall, Catford, London SE6 4RU, or telephone 01 -690 7666 G. F. Stone (24 -hour Ansafone service) quoting reference CE 78 and 9 Great Lawn Ongar Essex job title. held Interviews will be in London. England. (71131 Uos21

www.americanradiohistory.com Wireless World, April 1977 139 Appointments

. . ;t:-;.,;: .:>;:x::iÿti;',.';i::¡.:';;;s{;;v Radio Officers -now you can enjoy the comforts of home. Working for the Post Office Maritime Services really p.a. is payable. You'll also receive an allowance for makes sense. You still do the work that interests you, shift duties which at the maximum of the scale but with all the advantages of a shore -based job: more averages £900 a year and there are opportunities to time to enjoy home life, job security and good money. earn overtime. There's a good pension scheme, sick To qualify, you need a United Kingdom Maritime pay benefits and prospects of promotion to senior Radiocommunication Operator's General Certificate management. or First Class Certificate of competence in Right now we have a few vacancies at some of Radiotelegraphy, or an equivalent certificate issued our coastal radio stations, so if you're 19 or over, by a Commonwealth Administration or the Irish preferably with'sea -going experience, write to: Republic. ETE Maritime Radio Services Division ( L690), Starting salaries, at 25 or over, are £2905 rising ET 17.1.1.2., Room 643, Unión House, to £3704 after three years service. Between 19 and St. Martins -le -Grand, London EC1A lAR. 24, the starting salary varies from £2234 to £2627

according to age. In addition, a supplement of £312 Post Office TeIIeComlfl 1f1 un LII o01n5

SOUTH COAST Several of our clients require the following THE OPEN personnel urgently, offering excellent UNIVERSITY salaries and relocation expenses where Applications and Production Faculty of necessary. PROJECT ENGINEERS Technology ELECTRONIC ENGINEERS Engineers ELECTRONIC TEST ENGINEERS AND TECHNICIANS TECHNICIAN QUALITY ASSURANCE ENGINEERS Dolby Laboratories manufacture and market professional audio TECHNICAL AUTHORS An Electronic Technician (Calibration) is SYSTEMS PROGRAMMERS noise reduction equipment which is widely used by major recording required to join the general electronic DRAUGHTSMEN /WOMEN, Electro- companies, recording studios and broadcasting authorities facilities of the Open University. Mechanical Main duties of the post are to provide a 95% and BUYERS throughout the world. Established in London, the Company has in -house calibration and maintenance Please write or ring.,. service for all measuring equipment using CBS APPOINTMENTS enjoyed successful growth since incorporation in 1968. mainly electronic techniques. Rd.. Bournemouth. Bournemouth 224 OW Christchurch To assist all O.U. staff (academic. research,

1 70841 292155 or Wimhorne 4891 alter 7 p.m. technicians and maintenance) with Applications Engineer c.£5,000 Production Engineer c.£4,000 electronic problems and the use of their Reporting to and working closely The person appointed will join a equipment. To set up and maintain the necessary record PI PCO with the International Marketing small team which provides the system to operate such a service. Manager the person appointed technical support to the Experience: Ten years in electronics, five (S & W SERVICES) years of which should be relevant to the will be involved in all aspects of production department. Working For Electronic Engineers, Technicians above duties sales, eg providing technical under the Production Technical Qualifications: HNC or C and G in an & TV Service Engineers. appropriate subject. 26e High Street information to distributors and Manager this section is Salary: Technician Grade 5 E2889 -£3367 Hounslow, Middx. customers, giving demonstrations responsible for establishing per annum Holidays: working days. plus 6 Tel: 01 -572 7363 and training courses, testing procedures, 20 Telex Pipco Hounslow 935413 and visiting assembly and university closed days plus 7 national days. (6552) recording studios and broad- quality control and interfacing The post is within the New City of Milton Keynes. casting organisations in the UK with sales and design engineers There is a university office to assist with and abroad. on product improvements and housing. The applicant may be eligible for new product introductions. development housing and part removal CAPITAL expenses from the Open University. The successful applicant will be Application forms and further particulars are APPOINTMENTS LTD. available. by postcard request please. from an electronics engineer who. The successful applicant will be the Personnel Manager (ET2) The Open enjoys dealing with people and an electro- mechanical engineer University, P.O. Box 75. Walton Hall, Milton Keynes, MK7 Telephone Milton FREE JOBS LIST problems. Aged between 25 and who enjoys using his specialist 6A1. for Keynes 63868. 35 he, or she, will probably have knowledge to resolve day -to -day Closing date for applications: 31st March FIELD SERVICE ENGINEERS 1977 a degree and may well have problems as much as the more BASIC SALARIES TO 17065) £5,000 + CAR experience of recording studio theoretical aspect of the job. He, 70831 or broadcasting practice. or she, will probably have a 34 Percy Street, London, W.1 European languages would be a degree and experience in elec- TRAINEE ELECTRONICS 01.636 9659 (dey) or distinct advantage. tronic equipment manufacturing. EXPORT SALESMAN 550 0836 (evening) Good basic knowledge and German Write or telephone: Language required by active Compa- ny Interesting position with variety ELECTRONICS ENGINEER wanted. Gary Holt, General Manager Dolby EMPEXION LTD. With experience in modern ampli- DO Laboratories Inc 233/243 Wimbledon Park Road fication and electronic keyboards. Dolby 346 Clapham Road, Lonoon SW9 s.W.18 Hiring IYe¡rrtment, Maurice Dolby Laboratories Telephone 01- 7201111 Tel: Abott 01 -874 4362 Palcquet. Tel. 01 -749 3232. (7107 ) (7094)

www.americanradiohistory.com Appointments 140 Wireless World, April 1977 Transmitter Engineering SENIOR may DEVELOPMENT ENGINEER rim Service II. DEVELOPMENT I. Engineer al ( *4190 Saudi Riyals per month) ENGINEER for the Pye TVT Limited are among the world's leaders in the King Faisal Specialist Hospital and Research Centre, field of professional broadcast equipment. Expanding Riyadh, Saudi Arabia. activities in our transmitter engineering department now create the need for more personnel to join a team working If you are an experienced Service Engineer, fully of TV and broadcast on the design and development conversant with the most modern therapeutic and greater transmitters. The more senior position involves diagnostic radiology equipment, here is a unique responsibility and some supervision activities. opportunity to make a break for two years and practise The successful candidates are likely to have a degree or your skills in one of the most modern hospital and equivalent, but more importantly should have had research complexes in the world. several years of development experience on We urgently need an experienced Service Engineer, transmitting equipment - broadcast or radar. who will be responsible to the Chief Bio- Medical Relocation expenses to this pleasant part of East Engineer, to service and maintain a range of Anglia will ba given in approved cases. Other benefits predominantly Philips' radiology equipment. include a pleasant working Newly- built, air -conditioned accommodation is environment, a good salary (with provided, together with wide facilities for sport and recently implemented supplement), recreation. and cafeteria service, restaurant Two year contracts will be offered to suitably qualified sports staff shop and an active applicants. Passages and accommodation will be and social club. provided for up to three dependants and there are Please telephone or write to : generous leave periods. Mr. D. Barnicoat, At this time no income tax is payable in Saudi Arabia. Personnel Officer, going to press Pye TVT Limited, Sterling exchange rate at the time of £. P.O. Box 41, 5.97 riyals to the Coldhams Lane, Cambridge CB1 3JU. 7074 Please apply in writing or telephone: Tel : Cambridge 451 15 Peter Coles, Director of Human Resource Management (UK) II L Pye TVT Limited HOSPITAL CORPORATION The Broadcast Company of Philips INTERNATIONAL LTD., 33 Cavendish Square, London W1 M OAA. Tel :(01) -491 3211 HOSPITAL SALOP AREA HEALTH AUTHORITY CORPORATION 7079 Electronic and Bio -medical Engineering Department

TECHNICIAN IV ® CRP/r41 'OPTS. COURSES required for the Area Works Department based initially at Copthorne Hospital South FREE LISTS s RADIO and Radar M.P.T: and C Courses. Write: Principal, 01 Design / Development 11, Nautical College. Fleetwood, FY7 Qualifications O N C 'H N C Electronics and Test Jobs. PIl SJ Z. (25 46 P ermanent and Contract Responsible to Area Engineer To £6,000 M 70931 Salary scale 12.346- E3.267 p a + £31 2 p a supplement 6.17.1.1.$71110 55. oa3ere BOOKS "VINTAGE CRYSTAL SETS, 1922- TECHNICIAN ((Grade 1927". Just published by Wireless A is required for the above department to be responsible for thr+ ELECTRONICS technician by Physinlngy Dept. for World. contains 125 pages. Chap- maintenance of medical, mechanical and electronic apparatus used in the Area 6) required the design and construction of ters on the first days of broadcast- biophysical instrumentation to be ing. The Crystal Set. Vintage Wire- used in muscle research. Ex- less Trademarks. Also catalogue The Technician will loin a team who carry out a continuous servicing and perience in .analog, digital and sections listing and describing overhauling programme to ensure that the equipment in their charge will run at computer interfacing circuitry crystal sets together with their the peak of its available efficiency at all times. desirable. This is a three -year original prices in 1:s:d. A book for grant supported post. Salary to the collector or those interested in range £3.802- £4.435 inc. of London nostalgia. Available from main form from er direct from us. Please form and lob description to ne obtained from the Area Eng neer Weighting. Application hekshops Application Officer (Technical Stall send £2.50 inclusive to IPC Busi- Shrewsbury Hospal, Copthorne South Mytton Oak Road Shrewsbury. Salop Personnel FF51 University College London. ness Press Ltd.. Room 11 Dorset Ext appl coon forms to be returned Tel Shrewsbury 52244 3273 Competed Gower Street London WC1E 6ßT House. Stamford Street, London. by 14 days after insertion date (7106) SEl 9LU. (6125) 711 '

www.americanradiohistory.com Wireless World, April 1977 141 Appointments LINK There's only one person BROADCAST TELEVISION who can get

We have several vacancies for top electronic engineers to be involved in various aspects of our organisation, which covers the design you and manufacture of a full range good of studio television a equipment, including colour cameras and complete studio - /O. B. systems. We are a young successful company supplying sophisticated equipment world wide to major broadcasting job... organisations.

All positions require engineers with at least two or three years' experience in an industrial / broadcasting environment and offer the chance to make your individual ability felt within an expanding company. ...and that's Systems Engineer you. To be involved in all stages of project management on the But we've already made the right contacts. design and the building of studio and mobile TV systems. Occasional world wide travel. The appointment requires They're yours - and we doñ't need to someone with a knowledge of the operational side of interview or to see you first. television engineering and the ability to take charge of people and deal with problems in the field. All you have to do is to complete our special - highly confidential - application form. Development Engineer Then we'll simply pass on your particulars to those - and only those - companies really For this position we need someone with a thorough keen to meet a man or woman with your knowledge of the latest circuit techniques plus the ability to credentials and, aged between 20 and 45 years. put theory into practice in the design of sophisticated professional electronic equipment. You should be of And they'll approach you direct. HND /Degree level although relevant experience could We outweigh formal qualifications. guarantee to safeguard all your correspondence and never to get in touch with any company you specify -from among our list Test Engineers of clients. Like all good ideas - ours is very simple. It's This position again requires somebody with a good simply the best way to find a new job. knowledge of current analogue and digital circuit techniques plus recent experience with broadcast television or similar Try it and see ... equipment sufficient to enable you to integrate quickly into the team engaged in the testing of colour and monochrome Phone us today for an.application form or, clip cameras. the coupon for our comprehensive and confidential information pack. Experience solely of domestic television is insufficient and we regret that at the moment we are unable to cqnsider further Lansdowne Appointments Register, applications from newly qualified engineers. Design House, The Mall, London W5 5LS. We can offer satisfying work in a congenial environment. Our Tel: 01 -579 6585 modern factory is in a pleasant part of rural Hampshire with (24 hour answering service) easy access to London and major towns. There is a good choice of housing and special arrangements exist for those moving from the G.L.C. area.

Salary offered depends on age and experience but will be above average for the right people. Fringe benefits include a Tear out this pension scheme, free life and health insurance, generous confidential coupon holidays, staff restaurant and assistance with relocation. Name Please phone for an application form or write with sufficient Address detail of your qualifications and experience to make this unnecessary. Contact: Mic Comber - Personnel Manager - Andover W W 15/3 (0264) 61345 a n sdowne,

Walvtotth Industrial Essale, influence in high places LINK Andover, Hampshire, England Telephone Andover 10264) 61346 ELECTRONICS (7078) 40" ' ;70991

www.americanradiohistory.com Appointments 142 Wireless World, April 1977

We are looking for Lecturers to teach the practicalities of computer servicing. You will be based at our Engineering Training Centre in Letchworth, Herts - the largest of its kind in Europe. Here you will be given a comprehensive grounding in computer technology in general and ICL equipment in particular. You will be thoroughly prepared to train engineers to the point where they will he capable of maintaining computers at the optimum operational specification. Interested Ideally, you will have an HNC or Forces' training in a technical subject. Any experience of digital electronics, computers or instructing on these subjects, while not essential, will be useful. Fluency in written and spoken in computer? French or German would be a distinct advantage but is not essential. We'll start you as an Assistant Lecturer on a salary of not less than £3800 a year.You'll he encouraged and Lecture on expected to progress to the position of Senior Lecturer which carries a salary in excess of £5000. Relocation expenses will be considered where Computer 3ervicinq appropriate For an application form, phone David Reeves on 01 -788 7272 extension 4150, or write to him at ICL, 85/91 Upper Richmond Road, Putney, London SW15 2TE. Please quote reference. WW 1134 ICL International Computers think computers -think ICL (7ixil)

UNIVERSITY OF MANCHESTER UNIVERSITY OF SURREY Herter Adrian Research Centre DEPARTMENT OF ELECTRONIC AND ELECTRICAL ENGINEERING Anson House Pre -School Project for Mentally Handicapped Children VIDEO & AN ELECTRONICS ENGINEER /TECHNICIAN A vacancy exists immediately for a ELECTRONICS to on the Industrial Electronics Group working on a wide range of TECHNICIAN is required (Grade 3) advanced electronic design and construction projects. The post entails working ENGINEER quality in the above project. The successful with the minimum of supervision on the construction and testing of high applicant will work in the pre -school facility prototypes and presents an opportunity for career development in which is one mile from the University. but required with experience of instrumentation, computers and communications. will have access to 'electronic and servicing and installation of in the University mechanical workshops Video and Hifi equipment for a A second post exists in the Departments Electronics Workshop where an itself A major requirement will be that the ELECTRONICS ENGINEER is required to join a team designing, building and technician will be responsible for the responsible position in a new servicing a wide range of specialised electronic equipment. The successful operation of an extensive CCTV system are I organisation in the centre of candidate will be expected to work with a minimum of supervision and be will undertake the editing of tapes Bath. This is a challenging job capable of taking projects from outline design to final product. Experience with CCTV is therefore impor tant. Subsidiary functions will involve some for the right man, with excellent The successful candidates will be appointed in one of the Technician Grades 2 electronic and mechanical work. ONC s salary and promotion prospects to 5, depending on qualifications and experience. For the higher grades a essential and HNC (Electronics or Physics/ minimum of 3 years' relevant experience and qualifications equivalent to ONC for equivalent qualification) is desirable Apply in writing to: Video Salary Scale £2325 -£2655 p.a. plus are expected. Opportunities are provided for further study leading to higher earnings supplement of E130 p a South, 101 Eden Vale Road, professional qualifications. There are promotion prospects to higher grades. Applications with full details of age Westbury, Wilts, or telephone qualifications and previous experience Salaries Technican Grade Westbury (Wilts) 823140. should be addressed to Dr. J Hogg, Hester (7038) Adrian Research Centre. The University 2A £2152 - £2452 4 £2689 - £3087 Manchester M13 9P1 (7015) 3 £2455 - £2788 5 £2889 - £3367 6 £3314 - £3950 Application forms may be obtained from the Staff Officer, University of Surrey, Guildford, Surrey GU2 5XH, or Tel Guildford 71281, Ext. 452, and should be returned as soon as possible. (7056i Aural and Visual Aids Technician £3963 -£4299 per annum

An experienced technician is required by the Croydon SERVICE ENGINEER Education Service to maintain and repair a range of Audio and Video equipment including T.V. Receivers in schools. L.K.B. Instruments require an additional engineer to service their range of clinical and nuclear products installed in customers' Commencing salary in the scale will be according to premises throughout the West Country and South Wales. The qualification and experience. applicant should live or be prepared to move to this area. In an appropriate case consideration will be given towards Experience with nuclear counting equipment would be an assistance with removal and lodging expenses. advantage but a good general knowledge of digital electronics and a mechanical aptitude is considered essential. The company offers a salary commensurate with experience, bonus CROYDON and assisted B.U.P.A. membership. scheme, company car, Apply in writing giving details of age, qualifications, Please contact for application form - present post and relevant work experience to The The Service Manager Superintendent, Education Service Centre, Princess L.K.B. Instruments Limited Road, Croydon CRO 2QZ or telephone the Superin- 232 Addington Road tendent, Mr. A. Bevan (tel: 01 -684 9:93) for further South Croydon, Surrey details. (7037) Tel: 01 -657 8822 17059)

www.americanradiohistory.com Wireless World, April 1977 143 Classified APPOINTMENTS ARTICLES FOR SALE HF RADIO EXCLUSIVE OFFER WORLD -WIDE RANGE SYSTEMS ENGINEER NEVER BEFORE OFFERED PHII.CO HC -150 POINT -TO -POINT STRIP RADIO HF RECEIVERS 2 30 n, cs. Ten fully tuneable channels to 0.5 kcs with synthesisers. £5,000 to £6,000 per annum Single and diversity reception on ISB. DSB. SOB with 4 sub -bands to each channel 'Full details and peces on application. The Cable and Wireless Group, a leader in global telecommunications, career opening at its Central London Head Office for a has an interesting HIGHEST radio operating below 30 MHz. QUALITY 19" design engineer (male /female) of systems RACK MOUNTING CABINETS Duties will include responsibility for provision of HF prediction services, & RACKS propagation studies, advice on technical characteristics of antennae and ENQUIRIES INVITED FOR NEW STOCKS modulation methods. NOW AVAILABLE Applicants should preferably have an acquaintance with working AUDIO AND INSTRUMENTATION- systems, knowledge of the ionosphere and some computer programming TAPE RECORDER-REPRODUCERS

experience. A suitable degree in electrical engineering, professional Plessey 1033 Digital Units.. . Plessey M5500 Digital Unit.. (r.,. engineering qualification or HNC would be an advantage. Ampex FR -1100, 6 speeds. stereo Ampex FR600, 4 speeds. 7 tracks Excellent conditions of service are offered with commencing salary of D.R.I. RMI, 4 speeds, 4 tracks', EMI TR90 2 speeds. I track '2' between initially £5,000 and £6,000 per annum, depending on EMI BTRI, I speed. I track 's rising to over * EMI R301G, 2 speeds. 2 tracks experience and qualifications, on progressive career scales EMI RE321 ' ", 711" I track Sports Ficord IA 4í ", li. ", 71/2''. I track £7,000 per annum. Generous leave and pension arrangements, Mincom CMPI00, 6 speeds. 7 tracks i,. ra, I' and Social Club, and other benefits. Leevers Rich DA-2P. 2 speeds. 2 tracks I'.. * Leevers Rich Console 2 track r, ". 2 speeds Prices of above £70 to £500 Application forms may be obtained from: - Also Transport Decks only available Recruitment Manager, Cable and Wireless Limited, Dept. A.443a/643 We have a large quantity of "bits and pieces" we cannot list - please send us your requirements, we Theobalds Road, London WC1 X 8RX. can probably help - all enquiries answered. (01 -242 4433 ext. 211) 7066) ui,,,11 arria

D r ua 1

* Oscilloscopes Gen. purpose 3" E35.00 Solartron CD 711,52 D /L'Oscilloscopes E110.00 Cable 702 Cren. * Airmec Sig 30 /300KCS ... C15.00 lof! Lightweight Mast sections.secta sides C14.00 Oscilloscope Trolleys from C12.00 I.B.M. Video Display Units 4 col 018.00 Venner 5336 Counters £40.00

* Autophon VHF Receivers 20, 120mcs .... . £140.00 Solartron CD 524 Oscilloscopes 090.00 100 amp Belling Lee Interference Filters .. 075.00 Marconi TF2331 Distortion Meters 6160.00 AVO VT Voltmeters CT -471A 075.00 Solartron Digital Voltmeters LM 1420/2 0120.00 Racal MAI97 Pre -Selectors C65.00 Marconi TF -888 Receiver resters £60.00 Electronics Engineers Collins 500 watt 2/18 mcs. Transmitters £1000.00 Collins KWT6 SSB 500w Transceivers . . 61250.00 Collins KWT6 200 m,w AM transceivers C750.00 STC Rx5 2/25 mcs Receivers Diversity £140.00 Rack Mounting Operator Tables £10.00 Cheltenham Gaumo Kalee 564 s Flutter Meters C75.00 Hewlett Packard 6188 Sig. Gen. 3.8.7.2 GHz 0120.00 The Scanner Division of Linotype -Paul is world renowned for Rohn 95ft masts lattice 12" sides P.U.R. 30ft Lattice Masts, 14' sides C55.00 the design and production of sophisticated systems used in the * 15ft Lattice Mast sections. 12' sides 035.00 12Oft Lattice Masts, 15" sides P.U.R. colour printing industry. 75/90ft Sky Towers, self- supporting Eí75.60 Heavy Aerial Rotators P.U.R. The Division now requires top -class electronics engineers to Racal SA 594 Voltage converters 025.00 Elliot Recording M, A Meters 075.00 carry out complex testing operations during sub -assembly and final 75ít Aluminium Lattice Masts, 20ft sides £400.00 Plessey peak distortion meters 035.00 test stages. Polarad Microwave power meters 055.00 Rhode & Schwarz SBR sig gen, 1.6/2.4 gmc [70.00 Applicants, male or female, must have wide experience of S.E. 4000 System Units P.U.R. Large Aerial Turning Units P.U.R. analogue and digital circuitry, preferably gained in a test * 45 feet Uniradio 4 Co -ax 50 ohms £2.00 Baluns Professional Exterior 600,75 ohms .. £6.00 environment, and should be educated to ONC. An understanding of 25ft Telescopic Aerial Masts 024.00 Addo 518 Track Tape Punches E4Á.00 precision mechanical engineering and associated materials, as well * Digital Cassette Recorders '+' 1000 bps 0250.00 * Quality Weather Vanes 8 contacts (unused) C25.00 as the principal processes in colour photography, would be Racal RAI7 Front Panels (new) C15.00 Racal MA -1751. S.B. Modulators (new( 045.00 advantageous. Imslide Cabinet Shelf Sliders ... C3.00 * DG -7,32 or DG7.5 C.R.T.'s 03.00 We can offer top salaries and excellent conditions of Tally 5/8 Track Tape Readers 60 cps 048.00 in cases. Tally 5/8 Track Tape Readers Track Spooling C65.00 employment. Assistance with relocation will be provided appropriate * Cawkell FU 4 Rand Pass Filter Testers 060.00 Please write with career details to: * Avo Geiger Counters (new) 014.00

We have a quantity of Power I ranstormers 250 Barrie Witt, Personnel Officer watts to 15KVA at voltages up to 40K V. Best Linotype -Paul Limited quality at low prices. Lists available. Block 22, Lansdown Industrial Estate Glos. Racal RA -63 SSB Adaptors, new 070.00 Cheltenham, (7103) Racal RA -237 L -W Converters, new 070.00 1974 * Portable Mains Battery Hospital Lights E24.00 400 Channel Pulse Height Spectrum Analysers £000,M

We have a varied assortment of industrial and professional Cathode Ray rubes available. List on ARTICLES FOR SALE request.

HIGH POWER TRANSISTOR 60KHz NSF Rugby Receiver. BCD MAGNETIC MICROPHONE PLEASE ADD CARRIAGE AND 160 Volt. 30 Amp TIME OF' DAY OUTPUT. High per- SPEAKERS V.A.T. formance, phase locked loop radio 41 Inserts, ideal lo. ., ....d speaking and Very royged ?N 3773 El 30 each in 100's. receiver. 5V operation with 1 listening applications DC res 20 second LED indication. Kit com- ohms 20 each in 1000's VAT extra. Sise: 1'/e" tlia °h" deep P. HARRIS plete with tuned ferrite rod aerial 40p ea ± 10p P &P J.A.T.A.Electronics Ltd. £14.118 (including postage and 6 for E2.20 + 20p P &P ORGANFORD-DORSET VAT). Assembled circuit and cased - 12 for £4.10. P &P free. BH16 6BR 9 Heaton Road, Bradford up version also available. Send S A E for list Many other -items. Trade enquiries BD9 5EU welcome BOURNEMOUTH (0202) West Yorkshire for details Toolex, Sherborne I.I. SUPPLIES, 741 Shalnerford Sr+t 765051 Phone 10274) 45712 (4359), Dorset. (21) Nr. CANTERIURY, Kent CT4 70Z los /1 (6 1921

www.americanradiohistory.com Classified 144 Wireless World, April 1977 APPOINTMENTS ARTICLES FOR SALE

We are a major force in the business of nuclear instrumentation and wish to appoint a CHIEF OF TEST

to head a team of Test Engineers working on fault finding and testing of both analogue and digital circuits and systems for a 1lftit #fil lIT tit +ü4#1 wide variety of electronic equipment. © m lîia ma Applicants must have a proven administrative record to MOD standard and possess an inquisitive and logical attitude to problem solving. A minimum qualification of HNC is desirable but academic qualifications are less important than sound test REW are proud co present the Soundcraftsmen Graphic Equalizer-undoubtedly a background of Industrial Relations. experience and the fin st unit of its kind for both Hi -Fi and professional use. Each of the stereo channels is divided into 10 frequency bands, from 20 Hz to 20,480 Hz. Boost An attractive salary is offered together with excellent career and cut of 12 dB is provided on each band and a gain control adjusts the output a front panel. prospects. Please write or telephone for further details to: to match any amplifier. The unit has champagne gold anodised enclosed in an attractive wood- grained cabinet. The Soundcraftsmen can be used as a sophisticated tone control enabling you to highlight individual instruments. Alternatively it can be used to produce a near -perfect flat frequency response in any domestic conditions by compensating for either poor room Mr. D. Moy, Q.A. Manager acoustics or various deficiencies in Loudspeakers. Also perfect for equalizing Nuclear controls Division tape recordings. Send for full literature. -ELLIOTT PROCESS .98C GEC Full range of Equalizers by other leading manufacturers also in stock including INSTRUMENTS LIMITED Altec, JVC, BSR, MXR, Technics. Century Works, Conington Road Lewisham, London SE1 3 7LN Tel: 01 -692 1271 ext 393 REW Centrepoint 20 -21 St Giles High Street, London WC2 Tel 01 -240 3066/ 7 146 Charing Cross Road. London WC2 Tel 01 -240 3064 Mail orders to REW House (dept. WW), 10 -1 2 High Street. Colliers Wood, London SW19 Tel. 01 -540 9684/5/6 .70591

ARTICLES FOR SALE SOWTER TRANSFORMERS SPOTWELDERS new from £85. Ring 01- FOR SOUND RECORDING AND Sameside from £229. - REPRODUCING EQUIPMENT 540 7337/8. Rentweld's, 14 Claren- -we are suppliers t any well -known companies ) studios and don Road, London S.W.19. ( 6518 broadcasting awhonties and wre SOFTWARE C.R.T. REGUNNING PLANT. New established in 1941 Early del,veesn Competiti ve and secondhand reconditioned pricesp Large or small quantities Let us quote FOR or SOWTER TYPE pp678 DESIGN training. demonstration, colour A recent release B /W. Barretts, Mayo Road, Croy- MULTITAP MICROPHONE TRANSFORMER 9917. ELECTRONIC INSTRUMENTATION. MICROPROCESSORS don, Surey. CRO 2QP. 01 -684 If you are interested in the buying Primary windings for 600 ohm. 200 ohm and 60 by J. G. Webster used ohm with Secondary loadings from 2K ohm to 10 K or selling of good quality ohm Frequent? response plus/minus 1/2d8 20 H: Price £12.70 Electronic Test Instruments. ring to 25 KH: Contained in well finished Mumetal box INTRODUCTION TO DIGI- 16mm BELL HOWELL 631 750/100 Reading 51074. Martin Associates 33mm diameter by 22mm high. with colour coded W lamp, separate speaker and converse with our Sheila and leads. low distortion DELIVERY (small TAL FILTERING by R. E. and quantities) EX -STOCK HIGHLY COMPETITIVE transformer. £150 I- VAT. Hilton's Hatch who will deal promptly Price- PRICE FULL DETAILS ON REQUEST Bogner. £8.50 9 West Hill. Dartford. Kent. Tel: with your enquiry. E. A. 6758) SOWTER LTD. ACTIVE- FILTER COOKBOOK 20009. (W W 15 ) Transformer Manufacturers and Designers 7 Dedham Piece, Fore Street by D. Lancaster. Price £10.00 Ipewlch IPA 1JP Tel 0473 52794 THE CATHODE -RAY OSCIL, VALVES RADIO - T.V.- Industrial- LOSCOPE & ITS USE by G. Transmitting. We dispatch valves 4100. return OSCILLOSCOPE 100Mhz Cossor N. Patchett. Price £3.85 to all parts of the world by Almost brand new. with manual. or sea mail. 2,700 types PRINCIPLES OF TRANSIS- of post, air *Nearest offer to £495. - Teleradio. in stock. 1930 to 1976. Obsolete St, London N9. 01 -807 ARMATURE & COIL WINDING 325 Fore ENAMELLED TOR CIRCUITS by S. W. types a speciality. List 20p. Quota- 3719. (7063) COPPER WIRE to Monday Only too yf,i.tlrly materials supplied Ail Amos. Price: £4.65 tion S.A.E. Open callers I)s) to Saturday 9.30 to 5.00. Closed ii, deli d,n.v,. wdn!n 24 hours ELECTRONIC ALARM s. w g l,h r el LIb reel 110 Wednesday 1.00. We wish to pur- PROJECTS FOR THE HOME new and boxed 10 to 1 9 £2.95 £1.60 chase all types of SIGNAL GEN- to (Sussex) Ltd.. SCHLUMBERGER 20 29 £3.15 £1.80 CONSTRUCTOR by R. M valves. Cox Radio ERATOR D.O. 1001 o /25mhz ADt- 30 to 34 £3.45 £1.90 East Wit - Marston. Price £3.25 Dept WW. The Parade. FM. offers over £750. Drake R5 35 to 40 £3.65 £2.10 SBN. West Wit - tering. Sussex P020 same as DSR2 Am- All prices inclusive of P &P in U K IC OP-AMP COOKBOOK by Code 024366). digital receiver tering 2023 (STD CW-SSB. 0 /30mhz, £400 or neat COPPER SUPPLIES ( 5392) W. G. Jung. Price: £9.00 offer. Pye on freq. repeater. 450, 102 Parrswood Road HI FI YEAR BOOK 1977. 470 mhz, £220. Pye T470/1(470 Withington. Manchester 20 utters. (7077) Tel 061 -445 8753 Price £3.60 VACUUM is our speciality, new U.H.F. link, unused. VIDEOTAPE RECORDING by and secondhand rotary pumps. dif- coolers. J. F. Robinson. Price £7.00 fusion outfits, accessories. etc. Silicone rubber or varnish out - FREQUENCY SYNTHE- gassing equipment from £40. V. N. SILICON SOLAR CELLS: \tti lt.\ SIZERS THEORY & DESIGN Barrett (Sales) Ltd., 1 Mayo Road. IOM.W £5.96 MST 12 2501nw £9.55. ATTENTION by V. Mannassewitsch. Price Croydon. 01-684 9917. (24 Price includes data postage and MANUFACTURERS W. Edencnmbe Ltd. £20.00 VAT. - Dept LARGE STOCKS OF ROTARY POTS P.O. Box 276. 67 Gloice:aer Street. NICAD BAT- 10K LOG PC type TTL DATA BOOK by National. RECHARGEABLE London SW1V 4DZ. 170561 £1.26. 'Sub 51( UN PC type Price £3.10 TERIES. 'AA' (HP7) C' £1.29. 'C' (HP111 £2.35. 'D' 509K 106 PC type Otters around 10p * PRICES INCLUDE POSTAGE * £4.98. Matching 5006 LIN STD type each dependent on ( HP2) £2.92. PP3 chargers respectively £4.48. £4.45. TELEPHONE ANSWERING Machines 25K LIN STD type quantity. include 5K UN STO type THE MODERN BOOK CO. £5.24, £5 24. £3.98. all prices for Sale. New £170. Answers and A package. SAE 1m LOG STD type VAT. Add 10;; post Records. Plus 2 -wav Conversations for full list. plus if wanted 50p for Free Accessories and ALSO LARGE STOCKS OF SLIDER POTS i BOOKa and Dictation. d t(,hNILAL Cadmium Power' booklet. ION LOG) Over, Nickel guaranteed 1 year. Callsaver. around ISp 19 PRAED STREET Power Ltd., 1 Den - 50K LOG - -21 Sandwell Plant C.R.V. Electronics Ltd. 111 -249 0416. dependent on quantity Coldfield. West I OOK L06 ) LONDON W2 1NP holm Road. Sutton 01 -551 1500. 30 G(or)e Street. Lon- SPP. Tel No. (121-354 kilns Road, Hamworthy, Poole, Dorset PM,ne 72J 4 I db Midlands. 1173 don tf1. 9744. Poole 102013) 78989 I /USR, Closed Sat .1 p rn 1Telephone

www.americanradiohistory.com Wireless World, April 1977 145 Classified ARTICLES FOR SALE

Giro Access and S.rcl.Yc.rd W.kome. CMOS WITH DISCOUNTS. Any m.. 1 n I In, 75' 2'I S In, Inn I, II1011. Official Orden accepted from Educational and Government 4000 0.20 4028 1.00 415 1.04 4086 0.50 14163 1.15 14526 2.16 14566 1.67 Oaparo enta 4001 0.20 4029 1.27 4054 1.29 4089 1.74 14174 1.08 14527 1.75 14568 3.15 SHOP HOURS 9 "12.30. 1.30 "5.00 4002 0.20 4030 0.60 4055 1.48 4093 0.59 14175 1.04 14528 1.22 14569 3.72 PRECISION 5 do. CLOSED WEDNESDAY. 4006 1.31 4031 2.46 4056 1.48 4094 14194 2.05 1.17 14529 1.72 14577 0.27 POLYCARBONATE 4007 0.20 4032 1.19 4057 29.81 4095 1.16 14419 2.67 14530 0.95 1 "4580 5.35 CAPACITORS B . COMPONENT FACTORS LTD 1.07 4059 8.20 4008 4033 1.55 4096 1.16 14490 11.51 14531 1.74 14581 4.30 All High Stability - extremely Low Leakage 4009 0.60 4034 2.11 4060 1.24 4097 4.13 14501 0.20 14532 1.39 14582 1.64 1977 ISSUE 66 PAGES - 3000 ITEMS 4010 0.50 4035 1.31 4061 25.80 4098 1.22 14502 1.38 14534 5.15 14583 0.54 4011 0.20 4036 3.09 4062 10.10 4099 2.03 14503 0.76 14536 4.00 14585 1.10 440V A.C. RANGE 63V D.C. RANGE 4012 0.20 4037 1.06 4063 1.22 40101 1.76 14537 13.17 Omen- Value 1u0 TN. VOUCHERS 14505 4.38 74C00 0.26 Value Price 4013 0.60 4038 1.20 4066 0.89 40102 2.16 14506 0.67 14539 1.24 74CO2 0.26 . Mt RENT 1,F9 sions(mml each -1.4 -r -5x SATISFACTION 4014 1.12 4039 3.09 4067 4.13 40103 2.15 14507 0.60 14541 1.62 74C04 0.26 SATISfACT10x 4015 1.12 0.01 8 GUARANTEEDGU COUNT SR 4040 1.19 4068 0.24 401041 226 14508 3.06 14543 1.82 74008 0.25 E1.28 75p 50p 0.1 27 0.1 DISCOUNTS 4016 0.60 4041 0.63 4069 0.24 40107 0.65 14510 1.61 14549 4.10 74010 0.26 12.7 68p .400 NEW PRICE 1137 -SAE 4017 1.12 4042 0.93 4070 0.85 40108 6.15 14511 1.74 14552 10.60 74C20 0.25 0.15 27 121 80p 0.22 £1.32 77p 5Ip ., 4018 1.12 4043 1.12 4071 0.24 40109 2.21 14512 1.03 14553 4.65 74030 0.25 0.22 33 16 86p 0.33 0.32 17p 51p TRANSFORMERS 4019 0.60 4044 4072 0.24 °4r 1.04 40181 4.30 14514 3.47 14554 1.67 74032 0.25 0.25 33 16 92p 0.47 f1.32 17p 51 SEMICONDUCTORS 4020 1.24 4045 1.55 4073 0.24 40182 1.73 14515 14555 1.01 74C42 1.84 3.47 0.33 33 It 99p 0.68 £1.44 84p 56p MODULES - AUDIO 4021 1.12 4046 1.48 4075 0.24 40194 2.26 14516 1.51 14556 1.01. 74C48 2.26 HEATSINKS -S "DEC 4022 1.07 4047 1.01 4076 1.71 40257 2.26 1451714.02 14557 4.65 74C73 0.87 0.47 33 I9 £1.10 1.0 £1.56 9Ip 60p AUDIO ACCESSORIES 4023 0.20 4048 0.60 4077 0.85 4700 1.75 14518 1.39 14558 1.26 74C74 0.80 0.5 33 19 EI.16 1.5 £1.74 f1.16 67p TOOLS - TEST METERS 4024 0.87 4049 0.60 4078 0.24 7083 4.25 14559 4.10 74C90 0.88 0.68 50.8 19 22 £1.98 £1.32 75p CALCULATORS AUDIO 14519 0.57 £1.25 - 4025 0.20 4050 0.60 4081 0.24 14160 1.15 14520 1.39 14560 2.17 74C93 0.66 LEADS- ENS -SITS 1.0 50.8 19 EI.37 3.3 E2.40 E1.60 99p 4026 1.92 4051 1.04 4082 0.24 14161 1.16 14521 2.77 14561 0.70 74C95 1.25 RESISTORS - CAPACITORS 1.5 50.8 25.4 E1.64 4.7 12.82 EI.88 0.23 4027 0.50 4052 1.04 4085 0.80 14162 1.15 14522 2.15 14562 5.59 74C926 7.55 CASES - COILS - NOOKS 2.0 50.8 25.4 £1.95 6.8 £3.48 E3.32 £1.41 CONNECTORS TERMS: Add VAT to all prices at 8 %. Postage etc. UK 25p ( +2p =27p) per order,' - VEROSOARD IO £4.98 £3.32 PC Q.01 MATERIALS - HARDWARE ex ..0 £2.00 no VA Orders rocessed same da . .7068 OXES - SCREWS - SNOBS 15 £7.14 £4.76 Q.88 OIS STORAGE UNITS. . ETC.. ETC GREENBANK ELECTRONICS (Dept W4W) 22 £9.66 £6.44 £3.90, 94 New Chester Road. New Ferry. viral. Merseyside L62 566. England. Tel 051 -645 3391 4ANIALIIM BENI CAPACITORS-YEIEE wai156M: 0.1. 0.22. 0.33. 0.41. OAR 1.0. 2.2. 3.3. 4.7. 6.8 J at 155/256 a 35V: 10.0.4 1l 1611/209 25E 22.0a al SP/ 10V or 14E. 33.0.4.109e IOV: 47.0,4 al 39 a 6V: 5f No,d, Sn.... L.g.ton auEE.,d LU7 7E0 103.0,F *l 31/. All *l 12p sack ID la CI.16. 5015r 25. IN Ia Tel LmpITIon aua..N231IS,dC.Meata)i/t.e:. O

Venner TSA 3336 Timer Counters 1 MHz TaAßBTOS I.C.' £40 UHF AND TV SPARES. COLOUR, Or with 15MHz convenors £50 ICI07/9/9 9p 8012/2121. IN 2I0056 SOp NEW Mk 3 ICI 14 12p 9C2I3/2131 lop ORIR colour bar generator kit Crystal Solanron CA51 2 Voltage standing IZ 1C147/ /9 IOp 8011/2141 I 15155 TMr 69p, aerial input type, R -Y, B -Y etc. ratio Indicator £40 cross wave 1C153 16p °BF191/5 12p 741 yIE R 7S (adds on to Manor Supplies i Marconi TF1041A Vacuum Tube Voltmeter 10151/7/9/9 I2p 8F150/1 20p 264N £1.13 hatch units) £25' pp 85p. Also RELIABLE E35 Wilt/1M Ilp 11118 Hp 501801315 21.50 Mit 4 combined colour bar genera. %4' E IC183/1831 Ilp AF/39 86180211110 2150 Philips GM6014 Valve Voltmeter 3 5 16114/1140 14 253702/4 TSBlals tor and cross hatch kit £35', Siemens 3D332K Level Meter E125 Ilp 21.42 pp 85p "Wireless World" TV Tuner Siemens 3W29K Level Oscillator E 125 and FM Tuner Projects by D. C. Marconi TF455E Wave Analyser E60 of POPULAR 0160(5-169)4 Sp. 45p. 18 111916 Read. Kits parts available. Boonton 202B Signal Generator £100 nar Mr 90p: . 6 13p in 45p. 14 W Nit 1544 4. 11 fa 241Er £1.012 114148 Sp. Cross Hatch kit, Aerial Input Private enquiries send stamps lot brochure Ribber - Desjardins Type 41 1 B 54 61Er 24.12 Mr 45p: 114001 514: 002 003 type. No other connections. Signal Analyser E200 Sp: 6Kp: 004 7p: 005 7'4: Sweep Maw 007 S14p. Battery operated, portable. Incl. HE QUARTZ CRYSTAL CO. LTD.

Sync & UHF Modulator units Q C C WORKS. WELLINGTON CRESCENT, LTD. MIMIC( 2EIIE110100ESJWRW. TR. - 5%0 S01. 311: 363:308: £11'. Add -on Grey Scale kit, NF W MAL. DEN. SURREY. C" 942 0314 /Y.x HAWK SECURITY 45p. CRT Reactivator IY7:S41:516:692:DIE 71S:842: 9VI: IOW. IIV:12V:131:13.51:ISY: £2.90 p/p 190 SPODE STREET, COVENTRY 16V: IBV: 20V: 224,2411,27V: 3311. 041117p RICO. 515r 31p. 10 Nr kit for colour and mono, £17.48' WEST MIDLANDS, CV1 388 Rp. 50 Mr £3.12. SPECIAL OfRO. 100 laaaa 14a M Mall hr p/p 80p. Signal Strength Meter kit (0203) 20609 £18. p/p 70p. 625 TV IF Unit, for 70901 IREKT011S-Vial NW Hi-Fi amps or tape recording £6.80 *lability. aia [Gam 1115".I1141140. C. hW p/p 65p. Decca Colour TV Thyris- PM C. E 12 aaia ah-haa 2.20152250. ML *l Ip mob. Sp. la QUARTZ CRYSTAL ION ay a a1a. 70p la 100 RI my ow rala. SPECIAL PACI: 10 I tor Power Supply Unit, incl. H.T., Bob Mu 2.2i1 15 2201730 mp151al 25 L.T., etc. Incl. ci'rcui'ts £3.80 p/p UNITS from 95p. Bush CTV 25 Power Supply SUCON MARC RECTIFIERS-I.5 uP. WirvaN1 0027: 100' PI V 7p O4 for Unit, incl. H.T., L.T., etc. £3.20 10-$00 M61 241.400 P.I.V. Sp 11 fer 31p1. p/p £1.20. Bush CTV 25 Conver- MST DELIVERY *MANUFACTURERS* B RIDGE RECTIFIERS gence panel plus blue -2`, amp: 20111405 350V 45p: 11009 55p. yoke, lateral 111614 STARIIM 13.60 p/p SOp. Philips single stand TO 04052716 *WHOLESALERS* SUBMINIATURE VERTICAL PRESETS-0.1W air: MI CI N. melt convergence units complete, incl 16 50:100.220.470:6804M:il. £3.75 75p. 2(2: 407. 5KB: 106 15K: 22K: 478:47(: controls, p/p Colour WE STOCK A COMPREHENSIVE 1008220K. 6800: 1M: 255, 55. Scan Coils, Mullard or Plessey E6 80p, AT1023/05 or RANGE OF ELECTRICAL AND p/p Mullard WRITE FOR PLEASE ADO 20p POST AND PACKING ON ALL ORDERS. (50007-010 COST Plessey Yoke £2.50 p/p OF SEA, 695141. VAT 15 AN 115.8 HIM Converg. LEAFLET AT 1 ELECTRONIC COMPONENTS. All 8', SEapl e marled 55p, Mullard or Plessey Blue Lat- 01IC1 Ara 121,'. erals 75p p/p 30p. BRC 3000 type McKNIGHT INCLUDING CABLES AND FLEXES. 5eE4 S.A.E. la NlltNal *lot NS15. scan coils £2 p/p 80p. Hush CTV CRYSTAL Co. Ltd. 25 n Coils £2.50 p/p 80p. AT VERY COMPETITIVE PRICES WMMa1 Kim ML milatH 15 Mu INN ampules. 5*5011Y INDUSTRIAL Phone or wolte for quotations MARCO TRADING (Dept P5) ESTATE. NOISE, TIa O6 ScMH. EataloA Wu. kgpIM. elay TEL HYTHE 848961 EQUIPMENT CO. TM- WME111 464/465 PTO 0948721 50p p/p 3) Bush /Murphy SOUTHAMPTON 554 eV ELECTRONIC STD CODE 0701 IPraprt MiNtwl Tradml TN I CTV 25 37174 EHT quadrupler (6044)' Springfield House £8.50 p/p 75p. Special offer colour' tripiers, ITT TH25 1TH £2 GEC 2040 Tyssen Street 11.75 p/p 50p. Philips G8 Panels, part complete, surplus /salvaged: London E8 2ND Decoder £2.50. IF incl. 5 modules 01 -249 5217 £2.25, T. Base £1 p/p 70p. CRT WE INVITE ENQUIRIES from any- SOLARTRON D.V.M. LM 11420 -2 rack Base 75p p/p SOp. GEC 2040 De- where in the world. We have in mounting, perfect working order coder panel for spares £3.50 p/p stock several million carbon resis- with manual. £100, needs meter 70p. VARICAP TUNERS. UHF: tors *th, }, 4, and 1 watt. } million lead only. ELC 1043 £4.00, ELC 1043/05 14.50. wire wound resistors 5 and 10 watt VHF; ELC 1042 £4.40, VHF 1 SURPLUS STOCKS. High Stab Wel- Philips - 1 million capacitors - million £3.30. Salvaged UHF & VHF Vari- electrolytic condensers - } million wyn. Electrosil Resistors. Also. caps £1.50 p/p 35p. SPECIAL transistors and diodes. thousands Quantities Potentiometers, Wire- RECEIVERS AND AMPLIFIERS OFFER: RBM 6 psn. Varioap con- of potentiometers, and hosts of Wo-und and Carbon. Pre -sets. Plus trol unit El p/p 35p. UHF Tuners other components. Write phone or E.H.V. Water Cooled Capacitors. R.S.P. 53 Barton transd. indl. slow motion drive call at our warehouse. - Broad - - Electronics, £3.80. 4 Psn. and 6 Psn. push but- fields and Mayco Disposals Ltd., Street 'Gloucester, GU LPY. Tel. HRO R3t5s, etc., ARM. CR100, ton transd. £4.20 p/p 70p. Philips, 21 Lodge Lane, North Finchley. 0452 23607. (7082) BRT400, G209, S640, etc.. etc., in Bush Decca integrated UHF/VHF London. N.12. 01 -445 0749, 445 2713. stock. R. T. & I. Electronics, Ltd., transd. tuners £4.50 p/p 80p. Thorn (5907) Ashville Old Hall, Ashville Rd., 850 dual stand, time base panels London, Ell. Ley'4986. (65 50p. Philips 625 IF panel incl. cet. 50p. p/p 65p. VHF Turret tuners OSCILLOSCOPE AT 7850 for KB Featherllght, SIGNAL Generators, Oscilloscopes, Philips 19TG170, GEC 2010, etc. PROFESSIONAL TV TUBE RE- (Remsco r fui cludi circuit Diagram Output Meters, Wave Voltmeters, E2 50. Pve miniature incremental BUILDING PLANT designed and Frequency Meters, Multi -range tuners £1. Fireball tuners, Fergu- manufactured with 20 years' con ' ion. £80 heno. - Ring exper- Meters etc., etc. in stock. T. son. HMV, 80p (N th London). R. Marconi p/p all tun- ience of tube rebuilding. Also all & I. Electronics Ltd. Ashville Old ers 70p. Mullard Mono scan coils associated supplies including Hall, Ashville Rd., London E.11. for Philips. Stella, Pye, Ekco, Electron guns. Regular training Ley 4986. (64 Ferranti. Invicta £2 p/p 70p. Large courses. Western -Whybrow Engin- selection LOPTs, FOPTs available eering, WECO Works, 'Penzance, LINSLEY -HOOD 75 watt amplifiers for most popular makes MANOR TR20 9QT (073676) 2265. (6542) constructed and repaired. Brand SUPPLIES, 172 West End Lane. new guaranteed spares by return. TAPE RECORDING ETC. London, N.W.B. Shop premises. Cal- BDY56 E1.85, 'BD'529 55p, BD530 welcome. (No's. 28, 159 buses 55p. lers 2N5457 35p BFR39 25p BFR79 25p, or West Hampstead -Bakerloo Line 'MPSA12 45p. Interference suppres- YOUR TAPES TO DISC. Mono or and British Rail). Mail Order: 64 KERABOARD PCB 18 x 12 covered sion kit (also Golders Manor Drive. London. reduces preamp Stereo Cutting. Vinylite Pressings, with Ultraviolet negative photo noise) with 'instructions £1.35. Sleeves/labels. N.W.11. Tel: 01 -794 8751. V.A.T. In- Top professional resist. Packs of five. Single sided clusive prices. P&P 15p. SAE quality. S.A.E. photo Please ADD 12 }7 TO ALL PRICES for for leaflet. £11, double sided £13. per pack. list. - I. G. Bowman (Dept WW), DEROY Records, " Eastwood," (EXCEPT WHERE MARKED VAT Including postage. Hal-pum, 52 59 Fowey Avenue, 87). (80) Torquay. S. Cove Dunbartonshire, Scotland. Shrubeote, Tenterden. Kent. Devon. (7102) (82)

www.americanradiohistory.com Classified 146 Wireless World, April 1977 CAPACITY AVAILABLE ARTICLES WANTED

ENAMELLED COPPER WIRE WANTED: TEST AND PRINTED CIRCUIT BOARDS * MINICOMPUTERS swg 1 lb 4oz. 2oz. prices,- COMMUNICATION 14 -19 2.40 .69 .50 Quick deliveries, competitive quotations on request, roller tin- * PERIPHERALS 20 -29 2.45 .82 .59 nings, drilling, etc., speciality small COMEQUIPMENT 30 -34 2.60 .89 .64 INSTRUMENTATION batches, larger quantities available single items or quan- * 35 -40 2.85 1.04 .75 Jamiesons Automatics Ltd, 1 -5 tities. also RF plugs. inclusive of p &p and VAT Westgate, Bridlington. N. Humber- sockets and connectors. SAE brings Catalogue of copper and side, for the attention of Mr J. Call or phone. COMPUTER APPRECIATION resistance wires in all coverings Harrison. Tel: (0262) 4738/77877. (18 170 Goldhawj Road. London. W.12 Godstone (088 384) 3221 THE SCIENTIFIC WIRE COMPANY 01 -743 0899 (7006) .PO Box 30, London E4 9BW (6243) DESIGN AND DEVELOPMENT. Our Electronics Laboratory work In WE PURCHASE ALL FORMS AIRTRONICS LTD., for Coil Wind- most fields for customers through - rout the world-. Including Telecom- TOP CASH AVAILABLE OF ELECTRONIC ing large or small production TX runs.- Also PC Boards Assemblies. munications, 11F, TV Links. for EQUIPMENT AND and RXS from 1 'MHz to 1 GHz all Suppliers to P.O., M.O.D., etc. Ex- NEW SURPLUS COMPONENTS port enquiries welcomed, 3a types of logic, digital and analogue COMPONENTS, ETC. Walerand Road, London SE13 7PE. systems, counters microprocessors SPOT CASH Tel: 01 -852 1706. (61 R.P.Vs, control. telemetery and D.F. Production facilities also All details to: CHILTMEAD LTD. available. Write or phone Mr. SKYWAVE ELECTRONICS 7, 9, 11 Arthur Road Falkner, R.C.S. Electronics, 6 Wol- 01 -560 3046 Reading, Berks. BATCH Production Wiring and As- sey Road, Ashford, Middlesex. Tel. (0734) 582 605 sembly to sample or drawings. Ashford 53661. (7021 McDeane Electricals, 19B Station Parade, Ealing Common, London, ALL SURPLUS or used equipment W.5. Tel: 01 -992 8976. PARTS spa- wanted. Radio telephones - com- PRECISION TURNED - * MINICOMPUTERS plete systems purchased. Ships cers, pillars, shafts, etc. Large/ and small boat radio's small batches. Quotations by re- * PERIPHERALS equipment /service cap- components, partly assembled turn. Send for plant chassis- etc, etc. Established 20 acity specials, no problem. Drury * INSTRUMENTATION contact SMALL BATCH PRODUCTION Bros., Unit 6, Medley Road, St years. For prompt attention wiring, assembly to sample or Phone: 65094.(6548) For fastest, best CASH offer, Mr Grout at Worthing 34897. GWM drawings. Specialists in printed Albans, Herts. Radio Limited 40/42 Portland Road, circuit assembly. Rock Electronics, phone. Worthing, Sussex. (6594) 41 Silver Street, Stansted, Essex. LTD. 33018/814006. CHILTMEAD Tel. Stansted (0279) !0734) 586419 ELECTRONIC INSTRUMENTATION. (19 PCB ARTWORK DESIGN SERVICE. Reading If you are interested in the buying Component screens, solder resist or selling of good quality used and assembly masters. Pads Elec- electronic test instruments, ring trical Ltd., 01- 850 -6516, 45 South- WANTED, all types of communica- Reading 51074. Martin Associates wood Road, New Eltham SE9. tions receivers and test equipment. and converse with our Sheila PRINTED Circuits. Ultra fast turn- (7055) Details to R. T. Sr 1. Electronics latch, who will deal promptly with around. Very competitive prices. Ltd., Ashville Old Hall, Ashville enquiry.nquiry. (6757) Also prototypes, artwork, photo- E.11. Ley 4986. (63 graphy, and drilling service. Kib- Rd., London, more Circuits, 120 Garlands Road, WILL BUY ANYTHING, any quan- PCB's Gun Wire if price is right ring Stan Redhill. Surrey. Phone 68850. CABLEFORMS Wir- Equip- tity 167391 Wrappings. Panel and Chassis SURPLUS COMPONENTS Willetts, West Bromwich, 021 553 ing from drawings /maps supplied, ment and Computer panels wanted 0156. (6615) parts supplied faster turnaround for cash. Ring Southampton 772501) Electronic- Assembly, Unit (16) - B.M.A. Tel: B -D ELECTRONICS offer prompt 6, Fen Road, Chesterton. (Cam- settlement for your surplus corn - East bridge 861305. main field of interest P.C.B. ARTWORK DESIGN - WE BUY new valves, transistors ponents. Our Anglia. Fast precise work at com- is consumer electronics. Please and clean new components, large Peter - petitive prices. Also instrument or small quantities all details, telephone our Miss Hughes, panel designs, etc. Contact tangent by Walton's, borough (0733) 265219. (22 136 Whitehall Road, "PROTOTYPE AND PRODUCTION quotations return. - Electronics, or 55 Worcester St., Wolverhampton. Norwich, Norfolk. Tel (0603) ASSEMBLY from your drawings (62 WESTREX IDA pickup cartridge, 28015. sample. Peter Everard Ltd., Goodmans Axion 80 speakers. PX -4, 77309. S ÓT6 (Glos) PX -25. STC 4300B valves. Wanted WANTED; AUGUST, SEPTEMBER, urgently. - Box WW7049. OCTOBER BACK ISSUES OF WW DESIGN, ARTWORK, development 1976. Write Nevile Cresdee, 30 R. F. INDUCTION HEATER about and production of electrical - test EQUIPMENT WANTED Stoke Road, Gosport. Hants with 1.5KW. - Barrett, 1 Mayo Road, equipment. Powerline Electronics, price offer. (7069) Croydon, CRO 2QP. (6038) High Street Bognor Regis. Sussex P021 lEZ. Telephone B.R. 25689. 17062 BROADFIELDS AND ( MAYCO DISPOSALS SERVICES 21 Lodge lane, N. Finchley London, N12 8J6 FOR Telephone: 01-445 2713 01-445 0749 01 -958 7624 SPEECH -PLUS WE ARE INTERESTED IN CLASSIFIED RECORDINGS LTD KINDS OF Specialists In Recording for Education PURCHASING ALL Commerce, Industry A/V Programmes/ RADIO, T.V. AND ELEC- Pulsing for Training and Sales Cassette TRONIC COMPONENTS AND and Open -reel Duplicating EQUIPMENT IN BULK ADVERTISING 32 PAGES WALK. LONDON SEI QUANTITIES. Telephone. 01 -231 0961/2 (6250) WE PAY PROMPT CASH AND CLEAR MATERIAL BY RETURN. (46) RING EURO CIRCUITS ALaster BUSINESS FOR SALE I.r(out - l'h. y{i I, tend punting - Rodler tinning - Gold SMALL EAST LONDON BUSINESS plating - Flexible films - Cum en lion- FOR SALE as a going concern. EDDIE al Fibre glass - No order too large or too Specialising in Public Address and small - Fast iurnround on prototypes. NOW ... similar Sound Installations direct All or part service available to user. Certain amount of manu- EURO CIRCUITS TO. facturing. Old established and FARRELL Hightield House highly regarded. Staff, few in num- West Kingsdown ber, but loyal and efficient. Excel- Nr. Sevenoaks. Kent. WK2344 lent potential. Sale through ill health of owner. Principals only. Box W/W 7059. ON LABELS, NAMEPLATES, FASCIAS on aluminium or plastic. Speeds EXPORTER require; high qualify delivery G.S.M. Graphic- Art:: turntables, pickup :u nl. cart - and amplifiers Inc own Ltd., 1 -5 Rectory Lane, Guss ridges 01 -261 8508 borough (02873-4443), Yorks, U.K trademark. I:ome and export dis- (131 tribution. Box Ni. WiW 6774.

www.americanradiohistory.com Wireless World, April 1977 147

ALL THINGS ARE POSSIBLE

E. R. Laithwaite

All Things are Possible

In this, Professor Laithwaite's seventh book, he again offers us a rich mixture of controversial and always thought provoking articles. In the manner that we have learned to expect, he conveys through his writings and experiments the excitement of engineering and invention, and the ways in which man in his laboured progress has so often merely mimicked nature's own engineering achievements.

The author, famous in the academic world and for numerous television appearances, presents us with two series of articles, 44 it all, which will appeal to the engineer, scientist and all interested readers equally. The price of the book is £2.85.

www.americanradiohistory.com 148 Wireless World, April 1977

Available from Selected Slocieta. Write or phone INCREDIBLE VALUE IN PRECISION TEST METERS for Mn. MICROTEST 80 - I.C.E. SUPERTESTER 680R - I.C.E. 20,000 OHMS /VOLT 40 RANGES 20.000 OHMS /VOLT 90 RANGES 20 000 ohms, Volt. 4 000 ohms Volt 1AC1 2% accuracy 1 2 A C V DC 100mV to Ranges) VAC V DC 100mV to 1 KV (6 Ranges) I DC 50-A to 5A I6 Ranges) 20 000 ohms Von DC, 2KV 113

2 to 2KV 11 Hangesi I OC 50 -A to 10A 112 Ranges) 1 AC 250 .A to 5A 110 V AC 1 5V to 1KV (5 Ranges) I AC 250. .A to 2 5A /5 Ranges) Ranges) R rt s100 and Low ohms Detector Reactance Ohms Low ohms ohms x 1 ohms x 10 ohms K 100 1000 +1(7000 Measurements t Ranges) 010 M ohms Ereg Measurement 0 -5000 Fir f2 Rangesl Power Output /tF Power Output 5V to 1000V /5 - + 70 dB + 6dB to 52d13 (5 Ranges) 102000V /9 Ranges) Decibels 24 I10 Ranges) Capacitance .f. 0.500 000 pF 12 Ranges using mans supply) 0.20 000 -F 14 Ranges using Capacitance 25 -F to 25 000 -F 14 Ranges) \ internal 3 Volt battery) 1000 times overload protection on ohms ranges and 1ono ltmos overload protection ion OHM ranges) Q.~ . 10 Fields Measurement ranges Meter movement diode protection meter movement diode protection of and 80 Sire 128 x 95 n 32 m m Non parallas n cale Unbreakable carrying Sae (without case) 90 x 70 x 18 m m case supplied which contains mains t lead crocodile clips and shorting Electronic xero non.parallar minor scale Unbreakable carrying case and probes shioHied probes link ...... !:...--- ., Full After Sales Service available nere..«,w

Price £14.95.Post & Packin 60p VAT id 8 E 124 SEND TOTAL E 16 79

The I.C.E. Measurement Systems includes a comprehensive range of accessories: shunts, transformers, specialised probes, transistor tester, etc. Send for full details. ranges. from ' "Amperclamp' enables a multimeter to measure a.c. currents, in 6 2.5A to 500AI Ideal for use where breaking the circuit to insen an ammeter is impracticable, or where high initial currents are encountered. Versions available for use with other 513mA / I OumV multimeters n Price E13.50. P &P 60p. VAT£1.13. Total E15.23. Price £25.25 Post & Packing 85p 49-53 Pancrel: London NW1 2QB VAT 8% E2.09 Sole Importers SEND TOTAL E28 19 and Oistrlbubrn ELECTRONIC BROKERS LTD. 778 WW - 102 FOR FURTHER DETAILS

INDEX TO ADVERTISERS

Appointments Vacant Advertisements appear on pages 133 -146

PAGE PAGE PAGE AEI Transformers Ltd. 86 Genrad Ltd. 22 Q. Max Electronics Ltd. 15 AEL Ltd. 14 Gould Advance 64 Quality Electronics 119 AEL Crystals Ltd. 25 Greenwood Electronics Ltd. 9 Alex Lawrie Factors Ltd. 63 G.R. Electronics 111 All Electric Show 29 Radio Component Specialists 110 Amateur Components 124 Video Ltd. 30 Rastra Electronics Ltd. 111 19 Hampton Systems Ambit International & Co. Ltd. 98 R.C.S. Electronics 24 97 Harmsworth Townley Antex Harris Electronics (London) Ltd. 12, 17 Rola Celestion Ltd. 101 Ltd. 5 Arrow -Hart (Europe) Hart Electronics 104 R.S.T. Valves Ltd. 106 Ltd 19 Aspen Electronics Hepworth Electronics 16 RTVC 105 Audio Fair 21 Ltd. 25 13 Herbert Controls Audix Ltd. Heyco Mfg. Co. Ltd. 20 Scopex Instruments Ltd. 100 Barrie Electronics Ltd. 107 Scott, James (Elec. Eng.) Ltd. 100 Bayliss, A. D. & Sons Ltd. 10 Icon Designs 6 Service Trading Co. 99 Belling & Lee 107 ILP Electronics Ltd. 23 Servo & Electronics Sales Ltd. 119 Bentley Acoustic Corp. Ltd. 126 Industrial Tape Applications 111 Shure Electronics Ltd. 34 Beyer Dynamics (G.B.) Ltd. 8 Integrex Ltd. 102,103 Sintel 121 Bi -Pak Semiconductors Ltd. 116,117 Interface Quartz Devices Ltd. 31 Soundex Ltd. 29 Bi- Pre -Pak 125 ITF -Lets 7 Special Products Ltd. 16 Boss Industrial Mouldings Ltd. 14 ITT Electronic Services 72 Storno Ltd. 30 Bradley, G. & E. Ltd. Cover iii International Rectifier " 85 Stringer Clark Antennas 18 Bywood Electronics 30 Strumech Engineering Ltd. 12 JPS Associates 26 Sugden, J. E. & Co. Ltd. 11 Cambridge Learning 9 Surrey Electronics Ltd. 125 Catronics 29 Swanley Electronics Ltd. 28 CEC Corporation 17 Leevers -Rich Equipment Ltd. 12 Swift of Wilmslow 24 Chiltmead Ltd. 118, 129 Levell Electronics Ltd. 1 Circuit Designs 113 Lynx (Electronics) London Ltd. 114 28 Click Shelving Ltd. Tamba Electronics 28 Ltd. 13 Cliffpalm Maclnnes Laboratories Ltd. 6 Technomatic Ltd. 131 Ltd. 17 Coles Electroacoustics Servo Supplies Ltd. 18 Tektronix Ltd. 49 Ltd. 120 McLennan Colomor (Electronics) Maplin Electronic Supplies 52 Teleprinter Equipment Ltd. 24 Combined Precision Components Ltd. 115 Marconi Instruments Ltd. Cover ii Telequipment Ltd. 32 Commercial Trade Travel 127 Marshall, A. & Sons (London) Ltd. 121 Teleradio Hi Fi 31 Ltd 18 Compcor Electronics 16 Television 31 106 Medelec Computer Appreciation 125 Tempus 28 19 Metac Electronics & Time Centre Crimson Elektrik 27 All 29 29 Microprocessor The Electric Show Crofton Electronics Ltd. Mills, W. 112 Thomson CSF 89 Ltd. 25 Time Electronics 26 125 Monolith Electronics Co. Data Dynamics Mullard Ltd. 50, 51 Trampus Electronics 124 98 Dema Electronics International Multitore Solders Ltd. Cover iv Drake Transformers Ltd. 10 Vero Electronics Ltd. 18 Eddystone Radio Ltd. 4 Nombrex (1969) Ltd. 14 Edicron Ltd. 15 114, 119, 122, 123, 148 Electronic Brokers Ltd. Otani Corp. 2 Electro -Tech Components Ltd. 120 West Hyde Developments Ltd. 112 Electron /W. World 128 West London Supplies 125 20 Electronic Services & Products Ltd. 11 Pattrick, J. B. 132 Widney Dorlec Wilkinson, L. (Croydon) Ltd. 125 Electrovalue Ltd. - . ' 131 PB Electronics (Scotland) Ltd. 25 \Vilr,,ot Breeden Electronics Ltd. 3 Erie Electronics Ltd. , 15, 20, 30 PBRA Ltd. 3l 132 ES Electronics 29 Phonosonics 104 Wilmslow Audio Pinnacle Electronic Comps. Ltd. 90 Farnell Instruments Ltd. 71 Powertran Electronics 108, 109 Flight Link Controls Ltd. 31 Precision Petite Ltd. 26 Z. & I. Acro Services Ltd. 8, 19; 126 Future Film Developments 26 Purnell Loose imrrt Zettler (UK) Division 26

PRESS i. I D.. D,rroe: H,,ri.,., SL,,rrllurd St.. Printed ip Great Britain by QB Ltd, Sheepen Road, Colchester and Published by the Proprietors IPC ELECTHICALTLEC IRON lc \L): G,rrdun & ( ,otch Lid INDIA- .\ FI. Landon. SEI 9LU. telephone 01 -261 5000. Wireless World can he obtained abroad from the following: AUSTRALIA and NEW L1.ALA & Sons (S.A.) Ltd. Wheeler & Co. CANADA: The Wm. Dawson Subscription Service Ltd. Gordon & Gntch Ltd. SOUTH AFRICA: Central News Agency Ltd: William Dawson UNITED STATES: Eastern News Distributors Inc.. 14th Floor. Ill Eighth Avenue. New York. N.Y. 10011.

www.americanradiohistory.com Wireless World, April 1977

Even if we didn't make it, we'll make it work.

Bradley Services have the expertise and after -sales engineering support, from the manufacturing capability necessary. to provision of technical literature to the Bradley Electronics make the most sophisticated electronic upgrading of complete systems. systems and electro- mechanical devices. These facilities all approved to MOD G Et E Bradley Limited Lane However, equally important are the Def. Stan. 05 -21, have been developed Electra' House, Neasden facilities we have for repair and over more than 20 years and during that London NW101R R calibration. We can handle virtually any time we've handled practically every Telephone : 01-450 7811 type of instrument within the frequency type of instrument in use. So, if you've Telex : 25583 range DC to 36 GHz - irrespective of got a problem with some equipment, the manufacturer. chances are that, even if we didn't make We also have a Post Design Services it, we can still make it work. Group which provides every type of

WW-001 FOR FURTHER DETAILS www.americanradiohistory.com Wireless World, April 1977 Ersin Multicore- the international solder Ersin Multicore 5 -Core use less solder and obtain greater Savbit Solder reliability. Solder One of our most Our Quality Control at all popular The proved superiority of special ERSIN Multicore Solder stages of manufacture is ERSIN Multicore Solder for over alloys is SAVBIT alloy. Compared guaganteed and recorded by the thirty years is due to many with ordinary tin /lead batch number on every solders it factors. We have specialised reel. dramatically reduces the erosion throughout this period in the Needle fine gauges of soldering iron bits, copper manufacture of cored solders. wires and printed circuit Consequently our research and conductors. It also saves costs manufacturing staff have been and increases reliability. SAVBIT able to devote all their energies to alloy containing 5 -Cores ERSIN the development of Multicore 362 flux has received special Solders. All alloys are of highest Ministry approval -under DTD. purity, carefully formulated 900/4535 for Military applications. and checked. Our unsurpassed ERSIN flux is rigorously tested before and after In addition to our standard it is incorporated in the solder range of wire diameters (10 -22 wire. Our five separate cores of swg: 3.2 -0.7 mm) supplied on flux ensure flux continuity, leave 2+ kg and } kg reels we also mass - only an ultra -thin layer of solder produce needle -fine gauges (24 -34 separating flux from work for swg: 0.56 -0.23 mm) on 250 g reels instant wetting and provide for microminiature soldering a more accurate ratio of flux to applications -still with 5 Cores solder. It is therefore possible to of flux. Sectioned iron -plated bit, after 40,000 ALLOY simulated operations using 60/40 Solder. Melting Temperature Composition Grade Solidus Liquidus Specification (nominal major elements) o °C 50/33/17 Sn/Pb/Cd TLC 145 145 DIN 1707 62/36/2 Sn/Pb/Ag LMP 179 179 DIN 1707 62/35.7/2/0.3 Sn/Pb/Ag/Sb Sn62 179 179 QQ-S-57 1 E 63/36,7/0,4 Sr1Jb/Sb Sn63 183 183 - . QQ-S-57 1E 60J40 Sn/Pb -- 183 188 B.S. 219 -6111.39:7t0.35n/Pb/5tr.__. Sn6u T83- 188 QQ-S-57 lE 50/50 Sn/Pb F 183 212 B.S.219 50 49.7 0.3 Sn Pb Sb Sn50 183 QQ-S-57 lE 50/48 5/Sn]-Pb/Cu DTD 900/4535 DIN 1707 Sectioned 45/55 Sn/Pb iron -plated bit, after 40,000 24 B.S.219 simulated operations using 40/60 Sn/Pb 234 B.S.219 SAVBIT Solder. 40/59.7/0.3 Sn/Pb/Sb 234 QQ-S-57 1E 30/70 Sn/Pb 255 B.S.219 20/80 Sn/Pb 275 B.S.219 15/85 Sn/Pb 290- -Pure Tin 232 B.S.3252 95/5 Sn/Sb 243 B.S.219 5/93.5/1.5 Sn/Pb/Ag 301 B. S.219

For full information on these and a Selector Guide to other MULTICORE products please write on your Company's letterhead direct to: ulïcafe Multicore Solders Limited, Maylands Avenue, Hemel Hempstead, Hertfordshire HP2 7EP.

Tel : Hemel Hempstead 3636 Telex : 82363

www.americanradiohistory.com Wireless World, April 1977

Even if we didn't make it, well make it work Bradley Services have the expertise and after -sales engineering support, from the manufacturing capability necessary.to provision of technical literature to the Bradley Electronics make the most sophisticated electronic upgrading of complete systems. systems and electro- mechanical devices. These facilities all approved to MOD G Er E Bradley Limited Lane However, equally important are the Def. Stan. 05 -21, have been developed Electral House, Neasden facilities we have for repair and over more than 20 years and during that London NW101 RR calibration. We can handle virtually any time we've handled practically every Telephone : 01-450 7811 type of instrument within the frequency type of instrument in use. So, if you've Telex : 25583 range DC to 36 G Hz - irrespective of got a problem with some equipment, the manufacturer. chances are that, even if we didn't make We also have a Post Design Services it, we can still make it work. Group which provides every type of

WW-402 FOR FURTHER DETAILS www.americanradiohistory.com Wireless World, April 1977 Ersin Multicore- the international solder Ersin Multicore 5 -Core use less solder and obtain greater Savbit Solder reliability. Solder One of our most Our Quality Control at all popular The proved superiority of special ERSIN Multicore Solder stages of manufacture is ERSIN Multicore Solder for alloys is over guatlanteed and recorded SAVBIT alloy. Compared thirty years is due to many by the with ordinary tin /lead batch number on every reel. solders it factors. We have specialised dramatically reduces the erosion throughout this period in the Needle fine gauges of soldering iron bits, copper, manufacture of cored solders. wires and printed circuit Consequently our research and conductors. It also saves costs manufacturing staff have been and increases reliability. SAVBIT able to devote all their energies to alloy containing 5 -Cores ERSIN the development of Multicore 362 flux has received special Solders. All alloys are of highest Ministry approval -under DTD. purity, carefully formulated 900/4535 for Military applications. and checked. Our unsurpassed ERSIN flux is rigorously tested before and after In addition to our standard it is incorporated in the solder range of wire diameters (10 -22 wire. Our five separate cores of swg: 3.2 -0.7 mm) supplied on. flux ensure flux continuity, leave 24 kg and # kg reels we also mass - only an ultra -thin layer of solder produce needle-fine gauges (24 -34 separating flux from work for swg: 0.56 -0.23 mm) on 250 g reels instant wetting and provide for microminiature soldering a more accurate ratio of flux to applications -still with 5 Cores solder. It is therefore possible to of flux. Sectioned iron-plated bit, after 40,000 ALLOY simulated operations using 60/40 Solder. Melting Temperature Composition Grade Solidus Liquidus Specification (nominal major elements) °C oC 50/33/17 Sn /Pb /Cd TLC 145 145 DIN 1707 82/36/2 Sn /Pb /Ag LMP 179 179 DIN 1707 62/35.7/2/0.3 Sn /Pb /Ag /Sb Sn62 179 179 QQ-S-571 E 63 38 i Sn/Pb /Sb Sn63 183 183 QQ-S-57 1E 60/40 Sn /Pb K 183 188 B.S. 219 1 3 188 QQ-S-57 1E 50/50 Sn/Pb F 183 212 B.S.219 50/49.7/0.3 Sn/Pb/Sb Sn50 183 217 QQ-S-571E 50/48.5/1.5 iu+, Savbit 1 183 215 DTD 900/4535 _ DIN 1707 Sectioned iron -plated bit, after 40,000 45 55 Sn/Pb R 183 24 B.S.219 40/60 Sn/Pb simulated operations using G 183 234 B.S.219 SAVBIT Solder. 40/59.7/0.3 Sn/Pb/Sb Sn40 183 234 QQ-S-57 lE 30/70 Sn/Pb 183 255 B.S.219 20/80 Sn/Pb 183 275 B.S.219 15/85 Sn/Pb 225 290- 'Vure Tin P.T. 232 232 B.S.3252 95/5' Sn/Sb 95A 236 243 B.S.219 5/93.5/1.5 Sn/Pb/Ag H.M.P. 296 301 B.S.219

For full information on these and a Selector Guide to other MULTICORE products please write on your Afaéri Company's letterhead direct to: Multicore Solders Limited, Maylands Avenue, Hemel Hempstead, Hertfordshire HP2 7EP. Tel : Hemel Hempstead 3636 Telex : 82363