CADET was a transistorised computer built at the Atomic Energy Research Laboratory, Harwell, Oxfordshire from about 1953 onwards. The driving force behind it was E.H Cooke-Yarborough. A description of it can be found in the Proc. IEE for January 1956 and subsequent reprint, as well as a paper on operating experience in Proc. IEE in April 1958. One can also surmise that the machine used the circuit techniques described in Cooke-Yarborough's book, "Introduction to Transistor Circuits", Oliver and Boyd, 1957. The following image is a Harwell photograph of the machine, apparently set out for display to visitors:

CADET photo You can see that CADET stood for "computer automatic digital electronic transistor" which should be read backwards! The cylindrical object in the perspex box on the bench top on the left is the magnetic drum memory, which was the subject of a separate IEE paper in February 1956 by J.H.Stephen and Cooke-Yarborough because of its innovative circuitry. The main circuit boards were laid out in flat planes, unlike later machines which used card cages. This was probably because of the experimental nature of the machine.

CADET was one of the few computers that used point-contact transistors, the very earliest type available. Most of the devices used were made by the UK company Standard Telephones and Cables. The machine was obsolete within a few years, due to the rapid evolution of both transistor and computer technology at that time.

I possess no parts of CADET, but I was fortunate to visit Harwell in April 1984 and met Jim Stephen shortly before his retirement. He showed me a box of loose point-contact transistors of various types, and a few boxes of documents, all that remained of that era. He had donated some materials to the London Science Museum for the 25th anniversary of the invention of the transistor, when the Museum had mounted an exhibition.