GEC
HIGHGATE WOOD EXCHANGE

A meeting was held on the 17th April 1957 to consider a proposal for a 2000 line all electronic exchange. It would be designed to include sufficient code capacity to cater for STD. Tudor exchange, in Muswell Hill, was suggested as this had a low calling rate compared to most London exchanges and the new exchange would be a duplicate, so there was an electromechnical backup if required. Costs were considered and it was thought that most costs would be covered by an agreement with Joint Electronic Research Committee (JERC) and that the Post Offices costs would be around £5000.

It was originally planned to go live in March 1960, but nobody was really sure of the building requirements. After investigation it was found that additional space for ventilation equipment (4 tons), standby power with diesel storage, batteries (22 tons) and auxiliary equipment would require a building extension to Tudor Exchange. The Eastern Electric Board also requested the provision of a new electric sub-station.

On the 12th December 1962 the first electronic public exchange in the UK went live at Tudor Exchange at Highgate Wood in London. Designed by PO engineers at the Dollis Hill research Station, the exchange was produced by five different companies.

It was experimental and built next to an existing exchange which would be the backup in the event of a major failure. The exchange used a mix of transistors and valves, but already better quality transistors were coming onto the market and there was a new mark two model being designed.

Due to technical problems the exchange was short lived.

An article from GEC Telecommunications Magazine
An article form Telecommunications Journal Volume 12
An article from the POEEJ Volume 55, Part 4, Spring 1963

An extract from Post Office Telecommunications Journal Volume 12 No. 2

Electronic Exchange?
By Lionel H. Harris

The Postmaster General demonstrated the all-electronic exchange at Dollis Hill last November. Lionel H. Harris, then Engineer-in-Chief, presiding, discussed the reasons for this new exchange.

The war accelerated the development of "Electronics" and the post war period has seen the application of these techniques in many fields. The ingredients are always much the same; magnetic storage, pulse techniques, cold cathode tubes, and printed circuitry, miniaturisation and semiconductor devices.

Automatic computers, data processing machines and a host of industrial aids have already emerged from the laboratories. Even before the war it was
foreseen that telephone switching could be done without the use of moving mechanisms, at a price. Now the technical realization is much nearer and economic manufacture appears possible.

It may be asked why should we bother about electronic switching when electromagnetic systems throughout the world are giving satisfactory service.

I think the answer is that telecommunications engineers feel that the present mechanical systems have reached the stages of near perfection within their own limitations which prohibits any further major advancement and that although a difficult development and transition period must be faced, electronic methods are necessary if progress is to be unfettered and our sights raised to a new level of objectives otherwise unattainable.

It is probable too that we are influenced by general trends towards higher frequencies and quicker operation; towards microseconds rather than milliseconds and the realization that stability and accuracy are not sacrificed in so doing.

Even so, this higher level of objectives is not very easily defined-we should certainly save space by using electronic equipment and, in due course, reduce maintenance costs but, in the long run, I believe the ultimate advantage will be in the greater flexibility between the transmission system connecting our exchanges and the switching equipment; that is, dispersal of the latter and intermixture with the former. This would be in keeping with other tendencies which are leading to high frequency cables in the local networks; for example, for closed circuit television, for data transmission and, perhaps, even for economy.

It is not an easy task. The switching equipment is bound to have most of the complexities of computers and data processing equipment but in addition it must carry speech and tones, ring bells and operate meters and have other facilities all without noise and crosstalk. It must also provide a 24-hour-a-day 7-day-a-week service at a price fixed at a low figure by the requirements of a public telephone service.

The arrangements we have made with our five switching contractors for joint research and development have worked well. Apart from avoiding duplication, men of adequate calibre are in short supply. Moreover the essential requirements of the Post Office for our large exchanges are a single proven system with all the advantages of standardization in regard to maintenance, spare parts, engineering, training, drawings, and so on, which mean so much for plant which must have a life of upwards of 25 years to be economic.

We are, then, in an experimental phase but at the same time electronic equipment is already penetrating into the Post Office telephone service in several ways. Successful director equipments have long been working at Richmond and more recently at Lee Green. GRACE, which provides the electronic control of Subscriber Trunk Dialling at Bristol, has also been successful, and a notable example of the co-operation which continues to prove so valuable.

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