History

Channel 4 was the first UK television network to adopt digital links for distribution to transmitters. In part this seems to have been related to a change in the channel's legal status and relationship with the ITV companies. From launch in November 1982 to 31 December 1992 advertisments had been played out in each region, requiring links from to and from the relevant ITV studios. From 1993 Channel 4 arranged its own advertising, operating six "macro regions" each carrying the same programme content except for advertisments. Play out was from London, requring separate circuits for each region. This was provided as (compressed) 34 Mbit/s digital links, largely over fibre but with some use of digital SHF links. In general the circuits were arranged as a bi-directional ring with each transmitter having two feeds.

One exception was the Belmont transmitter which was connected as a spur from Nottingham. A new link was provided from the roof of the main "Bowman" exchange, via Carlton Scroop. This used Fujitsu DM1000 series equipment (BT designation RS10/89) using 64-QAM modulation on L6 GHz allocations. The equipment provided up to three 34 Mbit/s channels plus a shared protection channel in each direction - this seems excessive unless there was an expectation other networks would be carried over the same path. The reverse route from Belmont to Nottingham might have been intended for outside broadcast use.

We understand the equipment at Carlton Scroop was taken out of service in December 2004.