A less than secure (LTFS) system used on landline speech circuits. It was really speech privacy equipment which has a limited capability and was not to be used for information which might have a long term intelligence value. The device used Time Division Scrambling. This was the first time such a system was authorized for use in an operational area when it was deployed to Northern Ireland in the mid 1970's.
Another contributor adds "BID270 Goliath (or "Gollys" as we called them) were not speech compression machines but used Time Division Scrambling (TDS). Not only were they used on land lines but also with commercial 2 way radios (usually radios made by Pye) and normally fitted in staff cars and RMP vehicles. Because of the TDS, there would be a delay from when the operator started speaking till the scrambled stream was transmitted. This caused problems with press-to-talk radio systems, as the operator would release the PTT switch too soon and the end of the message would be cut off. I believe the radios were modified in early 1977 to stop this.
During the Ulster tanker drivers strike, the army was intended to drive the tankers. We had a mad two weeks of fitting Gollys and radios to the tankers only to have the strike called off on the end of the fitting operation".
The system's service life spanned from the early 1970's until the late 1980's.
Credits and References:
1) BID 160 placard at the UK Royal Signals Museum in Blandford Forum, UK.