The BID170 was a radio cryptosystem specific to the four channel PCM equipment  may have never have entered service. Everything that is known so far is posted below. Can anyone collaborate? Contact:

Chris Jones provides this base of knowledge."In 1960, SRDE in the UK, trialled a four channel PCM audio multiplexer that provided four 2-way speech circuits with signalling over a common bearer. The illustrations in the trials edition user handbook clearly indicate that it was intended for use using the B70 SHF link as a bearer link, but for whatever reason the PCM equipment seems to have never entered service and the B70 seems to have had little use as well;

The PCM equipment had a (6 way?) Mk 4 Plessey connector on it, clearly labelled “BID170”, and the text stated that the equipment could be used in conjunction with it to provide encrypted circuits. In the absence of encryption device, a dummy connector had to be inserted to maintain signal paths. With the limited number of contacts available, it is reasonable to assume that encryption was applied to the final bit stream rather than to the individual speech circuits. There is no mention of any “name” for the BID170

As stated above there is some reason to believe that the PCM equipment never entered service, and given that the BID may only have been used in conjunction with it and nothing else, then the BID170 may never have actually been put into service."

Credits and References:

1) Chris Jones <chrisjones12(at)>

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Jan 26/11