History

This was not a core route in the Post Office/BT network but used for televison distribution. The pre-history began with the award of a contract to Southern Television in 1958. The region to be served covered from Dorset to Kent. The company established studios in Southampton with a transmitter at Chillerton Down on the Isle of Wight and the Post Office provided a link from London. To cover Kent a further transmitter was built near Dover, entering service in 1960. This required a vision circuit from Southampton which was provided as a return channel on the link from London, connected to one "tube" in the existing London - Dover/St Margaret's Bay trunk cable.

Southern also established a studio at Dover in 1961. To allow this to feed the Chillerton Down transmitter (or elsewhere) required a further link towards London, also provided on the trunk cable. These arrangements were satisfactory for VHF 405-line television - it was not unusual for trunk cable to be used for vision circuits.

The introduction of 625-line colour televison in the late 1960s required higher bandwidth vision circuits - this was more difficult to provide over "long" cable sections and was a factor in the expansion of the microwave network nationally. The needs of Southern Television were to be met through the replacement London - Southampton system and the planned SHF link between London and Tolsford Hill, retaining a short cable section to Dover. Various factors delayed the completion of both sections however the Dover UHF transmitter entered service for ITV in December 1969. The BBC had its own arrangements, sometimes using an off-air feed, sometimes "borrowing" the vision circuit between London and Tolsford Hill which formed part of the UK link to the European Broadcasting Union (EBU - "Eurovision").

The permanent Dover link for ITV ran from the London Television Network Switching Centre (TVNSC) at the Post Office Tower, via Fairseat and Flimwell to Tolsford Hill where a TVNSC had been established for the EBU link. A network diagram from mid-1977 shows the vision circuits for Southern were extended over coaxial cable to Dover, via Folkestone and three other repeater stations. From Dover (exchange) cables ran to the transmitter at West Hougham and to a local studio in Dover. Switching allowed the transmitter to be fed directly from the incoming vision circuit or via the studio. The studio output was also sent to London and normally routed onwards to Southampton. Another option allowed the studio output to be sent to London/Southampton while the transmitter carried a separate programme received on the incoming line. It's likely a similar arrangement was in place since 1961 - this configuration remained until the Dover studio closed in 1983.

The launch of Channel 4 in 1981 required a further vision circuit from London. As far as we are aware this went directly to the transmitter. In the early years of C4 the regional ITV contractor was responsible for advertising and their regional studio would recieve the incoming C4 network and "play out" the advertisements to their local transmitters. For Southern we understand this was done in Southampton for the whole region.

A 1984 revision to the Tolsford Hill TVNSC network diagram shows there were then two inbound vision circuits: one from London, the other from Maidstone. This reflects the addition of a link for Channel 4 (on-air November 1982) and the ITV franchise transfer to TVS which estabished studios at Maidstone (operational mid-1983). The cable link to the transmitter was reconfigured since there was no longer a need to go via Dover exchange. The return link towards London remained, unconnected, and is labelled as terminating at Fairseat. The 1984 arrangement was to be relatively short-lived: Channel 4 moved to a new distribution network on 1 January 1993 and the ITV franchise transferred to Meridian on he same date. Meridian appears to have been an early adopter of digital/fibre links. The Eurovision circuits appear to have been unchanged as of 1984: one link in each direction but with access to the protection circuits on the other systems. This allowed additional capacity for major events.

The BBC was permitted to make its own arrangements for the Dover transmitter: for many years this involved off-air reception from London (Crystal Palace) followed by microwave links via other BBC sites.

During the TVS era a remote-controlled TVNSC was added at Fairseat (operated from Tolsford Hill). This was presumably intended to simplify switching since the company operated three studios in Kent at various times: Dover, Gillingham and Maidstone. Before mid-1983 it would have been necessary to route Dover or Gillingham to London (for Southampton). Gillingham was retained once Maidstone had opened and most likely the two were connected "directly". Maidstone could be connected "permanently" to both London and the Dover transmitter - however the arrangements for TV-am (1983-1992) required BT to provide direct links from London to the transmitters, bypassing the regional ITV studios. It's possible the remote switching at Fairseat was retained to bypass Maidstone during TV-am hours.

A network diagram for the London TVNSC, dated November 1984, shows several vision circuits to and from Maidstone "RTSC" - possibly Remote Television Switching Centre - suggesting there were three inbound circuits and two outbound. Both outbound circuits appear to have been cross-connected to Southampton, as was one inbound circuit. The other two inbound circuits were connected to the main switching matrix. No direct route to the Dover transmitter is shown at the London end - it appears all circuits went via Maidstone and it seems likely the TV-am switching was ultimately carried out there. The TVS studios were within two miles of the Maidstone exchange.