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Events in telecommunications history


The first 'relay' automatic exchange for the public telephone service in this country was provided for the Post Office at Fleetwood, Lancashire by the Relay Automatic Company (originally set up as the Betulander Automatic Telephone Company by Marconi's Wireless Telegraph Co Ltd in 1913). It was opened for service on 15 July.

The relay system was developed from that devised by Gotthief Angarius Betulander, an engineer in the Swedish Post Office and, as the name 'relay' suggests, was dependent on electro magnetic relays for performing the switching function. There was thus no frictional wear and the system was an entirely different concept from electro-mechanical type such as Strowger which involved the moving of a brush on a wiper over a number of contacts. In principle, the relay system, with its use of markers and relay crosspoint matrix and link trunking, foreshadowed the later crossbar and reed-electronic exchanges (although the crossbar switch itself had already been invented).

However, it was the Strowger system which was finally adopted by the Post Office (see below), and the relay system was considered better suited for small Private Automatic Branch Exchanges (PABXs). The first installed for the Post Office was brought into service at Debenhams in Wigmore Street, London, on 8 December 1923. After a series of full scale experiments in which different automatic telephone systems had been tried (including the Lorimer system in Hereford, Strowger system in Leeds, Western Electric rotary system at Darlington, Siemens system at Grimsby, and the relay system at Fleetwood), the Post Office decided to adopt the Strowger system as its standard. By the spring of 1924, Britain had nearly 265,000 lines working on 23 automatic exchanges, from a capacity of 25 line to 15,000, and by seven different manufacturers. Strowger exchanges became the backbone of the UK telephone network and remained a key component for over 50 years. The last Strowger exchange, Crawford in Scotland, was not removed from service until 23 June 1995 .

It had been thought that there might be difficulties using the Strowger system in very large cities such as London where numbers of large exchanges, and consequently a great number of inter-exchange calls, created a highly complex interconnected network. A number of solutions were put forward, but the problem was solved when the Automatic Telephone Manufacturing Co Ltd of Liverpool, working in conjunction with the Post Office, developed the 'Director'. This was a Strowger system with a number storage and translation facility which could 'direct' telephone calls through the complex network of circuits linking exchanges in large cities. This was achieved by the translation of the digits dialled by a calling subscriber to other numbers in order to direct the call over the most convenient route to the required exchange. The Director system also included the facility for calls to be dialled from automatic to manual exchanges where the required numbers appeared visually before the operator handling the incoming call, who then completed the connection manually. This Coded-Call Indicator (CCI) facility meant that a subscriber connected to a London automatic exchange dialling the number of a subscriber on a London manual exchange would be unaware that the call was not completed automatically. In addition, there would be no change of procedure for the subscriber once the manual exchange had been converted to automatic working. This was an important advantage, as the transition from manual to complete automatic working would not be concluded for very many years.

One feature of the decision to adopt the Strowger system was the many thorough economic planning studies made by the Post Office to determine the conditions justifying the adoption of automatic working. These studies demonstrated the need to be able to extend an exchange over a ten-year period and hence the requirements for uniformity of design, constructional and circuit practices. Another essential feature was pooling of patents amongst the British manufacturers of automatic exchange equipment to standardise all Strowger equipment construction. This co-operation between the Post Office and the manufacturers led to the first Bulk Supply Agreement the following year.

The telephone system in Southern Ireland was transferred to the Eireann Administration (then the Irish Free State); 194 telephone exchanges with 19,037 lines and 553 call offices passed into the control of the new administration.

The first automatic exchange in Hull was opened in Queen's Road.

A telephone service was established with the Netherlands (Holland) on 15 August.

The first trials with teleprinters were staged.

Experimental transmitters were not uncommon at this time and in this year the Marconi Wireless Telegraph Company began public broadcasting.

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