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STC Semiconductors

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STC logo Standard Telephones and Cables Ltd. (STC) was yet another great British electrical manufacturer with a long and distinguished history that could not make the transition to the world of modern electronics and vanished in the early 1990's. Although it was, to all intents and purposes, a British company, it was in fact founded as part of Western Electric, and owned by ITT for most of its life.

STC logo In the 1950's and 1960's STC played a major role in British semiconductor research and development, which was not far behind the Americans. However, information about this period of their industrial history is scarce. As with Mullard, much more information can be found about STC's valves/tubes (usually branded "Brimar" , although this was sold to Thorn in 1960) than about their transistors. Their research laboratory and manufacturing plant was based in Footscray, Kent. If you know anything about this, or have other information about STC's early semiconductors, please

STC's main semiconductor product lines were the TK, ACY and ASY series of germanium transistors. They made very few power transistors. Their devices usually bear the STC logo, the type number in capitals e.g. ACY34, and often a two-letter code which I do not know how to decode , or even whether it is a date code or something else. If you can help, please contact me.

I do not possess all the transistors below, in fact I am seeking many of them. It is noted in the text where I am seeking examples of any particular type: if you have some for sale or exchange, please Conversely, I am happy to help anyone looking for information on these devices. I have an extensive collection of original data sheets and books, and can provide characteristic data on almost all STC types.
3X/100N and 3X/101N transistors Probably the first transistors made by STC were the 3X/100N and 3X/101N point-contact switching prototypes, for which I have data sheets dated 1953. Coblenz and Owens book from 1955, one of the very first publications on transistors, shows an unidentified STC device, probably one of these two, that the authors state was made in 1949. These transistors are characteristic of early point-contact types in that the base lead emerges from the opposite end of the cylindrical can from the emitter and collector. This is because the base wire is attached to one side of the germanium die, and the collector and emitter point-contacts press upon the other. Both types use a long cylindrical steel can, with a serial number crudely etched into the metal. The 3X/100N has its part number hand-painted in white, the 3X101N has no other identification on the body, but the part number can be determined by the colour of the short sleeves on the emitter and collector leads: black+black for 3X/100N and black+brown for 3X/101N.
These are some of the rarest British transistors and I would like to obtain more of them.
TP2 transistor Two point-contact transistors were sold commercially by STC, the TP1 and TP2 from 1955. The image shows a TP2 in its original box, using STC's "Brimar" branding. A small label on the box indicates that this device was sold at Lasky's shop in Tottenham Court Road, London. These transistors are identified in STC's data book, the "Brimar Valve Manual", although unfortunately this annual publication rarely bore a printed date.
It seems probable that the TP1 and TP2 were commercial versions of the 3X/100N and 3X/101N, but I have no proof of this. If you know anything about it, please
I am seeking examples of both TP1 and TP2. I also wish to buy original data sheets for both of these devices.
LS737 transistor This point-contact transistor is a bit of a puzzle. It bears a paper label printed "LS737 STC CRYSTAL TRIODE" plus a handwritten serial number. I have a number of these, as do other collectors I know, and the label may have the wording either along or around the body. This transistor appears to be the commonest STC point-contact type, but strangely, it is not mentioned in any contemporary publication that I know. I do have a very basic data sheet that I obtained from Harwell Laboratory, otherwise I would know nothing about it.
If you know anything about it, please
3X/300N transistor The types 3X/300N to 3X/302N were STC's first prototype germanium junction transistors, low-power AF types in a 1-inch aluminium cylindrical can. I can only find one reference to these, dated 1956, but I am sure that they are several years older than that. If you know anything about them, please
3X/300N transistor section This image shows a 3X/300N transistor that has been cut in half and mounted in acrylic (which has gone rather yellow with age). The germanium die is the tiny black rectangle to which the wires attach. It is also evident that device was prevented from shorting out on the aluminium can by the use of an internal glass tube, sealed at one end.
TJ1 transistor These devices, types TJ1 to TJ3, are STC's first commercial junction transistors, and are presumably production versions of the 3X/300 types above. They date from 1956 and are described in the "Brimar Valve Manual". These types can sometimes be found in Brimar boxes such as that shown for the TP2 above.
TS1 transistor The types TJ1 to TJ3 did not last long, they were almost immediately replaced by TS1 to TS3, which used an improved and smaller metal can, albeit with lower power dissipation of 50 milliWatts compared with 200 mW for the TJ types. The series went on to TS18: early examples have green or red printing on bare metal, later ones are painted black with white lettering. These types can rarely be found in Brimar boxes such as that shown for the TP2 above. Unmarked examples from this series, presumably out-of-spec devices, were sometimes sold cheaply to the amateur electronics market as 'white-spot' transistors.
TK20B transistor The TK series from about 1959 was STC's first serious production range of transistors, covering all kinds of applications from AF to RF and switching. A number of the devices in the series had multiple suffixes, such as A, B, C (presumably gain selection) and even CA. The series used a metal can that STC denominated as KO-5, although other data books sometimes call it SO-2. It usually had a circular flange (joint?) around the middle, but as the TK20B in the image shows, this was not always the case. Often the transistors were painted black, but again this was not always the case.
TK201A transistors STC appear to have made very few power transistors at all. In fact, the TK201A shown is the only STC power transistor that I have ever come across. If anyone knows why this should be, please
ACY transistors STC changed from using their proprietary TK series, and went on to produce germanium transistors using the standard prefixes ACY and ASY. The image shows the different appearances possible: black painted, copper-coloured, or silver metallic.
set transistors During one period STC produced sets of devices just marked MIXER, IF, OP, DR for driver etc for manufacturers of superhet LONG/MW transistor radios.
ITT transistor Because STC was in fact owned by ITT, it is possible to find devices from their series marked as ITT. The image shows an ASY55.
Brimar diodes STC manufactured a small range of low-power germanium diodes with the prefix GD, under the Brimar brand. They also made a few other diodes in various shapes, for example medium-power rectifier diodes in the FST range.
TED517 transistor This device is a puzzle to me. STC made a small number of devices in this TED series, for which I have very little data. I know some date from 1959, and this example is certainly in the early TS-series style of packaging. If you know anything about this series, please

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