Highgate Wood Telephone Exchange

The Highgate Wood Telephone Exchange was the first all-electronic telephone exchange in Britain. It was built in the London suburb of Highgate Wood by members from Joint Electronic Research Council (JERC).

On Wednesday 12 December 1962, the 800 line Highgate Wood exchange was accepted by the Postmaster General, Mr. Reginald Bevins, MP, on behalf of the Post Office, from the five manufacturers who had helped to build it, the first all-electronic telephone exchange in Britain and one of the first in the world to go into public service. It had already carried public traffic experimentally for brief periods during the previous few weeks. He also announced on that day the building of three more advanced electronic exchanges to be installed and in operation within the next two years at Goring-on-Thames (high speed TDM 100 channel), Pembury (Low speed TDM 30 channel), and at Leighton Buzzard. The only one that was completed was the TXE1 at Leighton Buzzard, the other two being quickly abandoned.

The Highgate Wood Electronic Exchange had been the result of six years co-operative research and development between the Post Office and five principal British manufacturers of exchange equipment. This was coordinated through the Joint Electronic Research Committee(JERC). Although different contractors had been responsible for the system design, installation and manufacturing of various sections of the exchange, the commissioning had been the work of teams drawn from each of the parties to the Agreement. The Highgate Wood Exchange was not entirely typical of the systems which were to follow it. Each of the three new exchanges, all of which were to operate completely on their own, with no stand-by exchange as was the case at Highgate Wood, were to be designed to try out actual service conditions. Two of them were based on slightly different applications of the time-division pulse-amplitude modulation (TDM) principle, and the third, at Leighton Buzzard, on space-division switching. All three were to be fully transistorised so that they were going be more compact than Highgate Wood (which had about 5000 transistors and 500 valves) and would have needed less power. They were also expected to show a significant improvement in reliability that had been a problem at Highgate Wood. The model of Highgate Wood had worked "reasonably satisfactorily" [see Harris 2001] in the laboratory but the analogue transmission was too noisy on the long cable runs in an actual exchange. The problem was thought to be the earthing arrangements. TDM exchange operation in the UK did not become possible until pulse code modulation (PCM) was developed, providing a digital transmission solution which led to System X.

...
Wikipedia