Original Broadcast Network
This was the original Distribution Network installed by the University in the late 1960s and early 1970s to provide comprehensive video links around the campus. It was designed and installed by the Rediffusion company, whose main business was in distributing paid TV and radio services to householders over wired networks. The university network used much of the same technology as a small urban area commercial system, but with a greater provision for sending video back from the various parts of the campus to be broadcast. The system allowed up to 4 channels to be conveyed around campus on a multi-pair pair cable, with each pair dedicated to a separate channel. Further pairs in the cable allowed for up to 9 channels, 5 of them video and the other four audio-only. Video channels carried both the audio and video signals on a single pair in the cable.
An equipment room in LTC (adjacent to Central Hall until it's demolition in summer 2007) acted as the transmission hub. For transmission, the video from contribution cables or tuners receiving the BBC and ITV channels was modulated onto a carrier at 4.5MHz (405-line B+W channels) or 10.7MHz (625-line colour-capable channels) and the audio (at baseband) amplified. Audio-only channels were fed via power amplifiers so that outlets could use passive loudspeakers without further amplification, on the same basis as 100V-line PA systems. The transmission equipment and televisions were supplied by Rediffusion VisionUnverified or incomplete information. This method of cable based AV distribution was used in a number of towns in the UK, however it had reached the end of it's technological lifetime by the end of the 1980's. The system installed at the University of York was originally black and white (with a mixture of 405-line (BBC1) and 625-line (BBC2) channels) and was upgraded to support colour in the 1980s.
Rediffusion racks in LTC
Cable entry and exit in LTC
Video modulators in LTC
Installed alongside the distribution network was an AV Contribution Network. The contribution/distribution system was quite advanced in it's day since it would have been possible to do point to multi-point lectures and video conference across campus. However, it is not known if it every was ever utilised beyond retransmission of BBC1/BBC2/ITV and contribution/distribution of YSTV.
The distribution system suffered from having to use live chassis televisions that could receive the (non-standard) Rediffusion signal. This made replacing them difficult, since the Rediffusion company had pretty much disappeared by the early 1990's and the transmission system was technologically obsolete.