By the end of 1956, the ITA television service included just four transmitters, linked together by an already elaborate network of Post Office sound and vision circuits and repeater stations. Richard Elen describes the structure of the network, as it was a year after the start of Independent Television.
Many years before communications satellites and the modern paraphernalia of broadcasting had come into being, the General Post Office (GPO) was the organisation responsible for linking the different parts of the fledgling ITA network together. By the end of 1956, its first year in operation, the Independent Television Authority was operating transmitters at London (Croydon), the Midlands (Lichfield), Lancashire and its environs (Winter Hill) and Yorkshire (Emley Moor). They were linked to the various programme contractors via the main GPO repeater stations.
In London, vision and sound circuits centred upon the General Post Office Television Control at the Museum telephone exchange, situated not far from Tottenham Court Road. Two balanced cables, providing ten vision circuits, linked Associated-Rediffusion's Master Control which also handled ITN to the television control centre, while eight vision circuits similarly linked Associated TeleVision's Master Control in Foley Street to the Museum Exchange.
A one-way cable link connected the Museum to the ITA Croydon transmitter, while there was also a one-way circuit from ABC Television's facility in Wardour Street into the Museum Exchange. Several sound and vision links were installed from London studios such as Wembley and a number of theatres, while lines were also provided to sites on high ground in the London area, such as Highgate and Kensington, to provide reception points for longer-distance outside broadcasts.
The introduction of the independent television service to the Midlands area required a somewhat less complex Post Office control centre to be set up at Telephone House in Birmingham. Here, a two-way radio circuit linked London with Birmingham Television Control, going on to feed signals to the Lichfield ITA transmitter. A second, northbound only, radio circuit with three intermediate relay stations had been added to the original London-Birmingham link by the end of 1956. Meanwhile, the joint Master Control for the two television companies serving the region, Associated TeleVision and ABC Television, was situated in the Astoria Cinema in Aston and provided programmes to Television Control via five cable circuits.
Extending the network to Lancashire once again required an additional Post Office Television Control centre, this time at Telephone House in Manchester. A two-way vision link, with amplification every six miles, connected it to Birmingham. The two Manchester programme contractors, Granada Television Network on weekdays, and ABC Television at weekends, established independent Master Controls at Quay Street and the Capitol Cinema, Didsbury respectively, with five cable circuits linking each to the Post Office Television Control centre. Extension of service into Yorkshire was handled via a two-way radio circuit carrying sound and vision signals to the Emley Moor transmitter, which opened in November 1956.