From: EEC@PORTIA.UMDS.LON.AC.UK (Steve P eec@portia.umds.lon.ac.uk)
Newsgroups: rec.arts.drwho
Subject: 405/625/Colour changes on British TV
Date: 28 Sep 1992 05:22:45 -0500
Organization: UTexas Mail-to-News Gateway
NNTP-Posting-Host: cs.utexas.edu

I originally wrote this in answer to some questions from Frank Durda,
but since there's been some discussion about such things, I am posting
it to the net......

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|  Steve P                    (..)  |
|  eec@portia.umds.lon.ac.uk   ()   |
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As you say, the change from the old 405 line transmissions to the new 625 line
did not occur overnight.  The BBC had been broadcasting in b/w on 405 lines
since about 1936 on the VHF band. In 1956 ITV started using the same system
and mostly sharing the same transmitters used by the BBC.

On 20th April 1964 BBC2 opened.  This new service was transmitted in b/w on
625 lines UHF. This meant that, in order to get all 3 services, viewers had to
have receivers capable of picking-up both 405 line on VHF and 625 line on UHF.
Such "dual standard" TVs became common but they were quite unreliable and also
rather heavy! I must emphasise that despite being on 625 line UHF, the BBC2
service was not yet in colour.

Meanwhile, various colour tests had been going on from Alexandra Palace - the
first having been on the NTSC coding system back in 1956. Eventually colour TV
was officially launched on 1st July 1967 on BBC2.  The first official colour
programme was 7 hours of tennis !  The colour system chosen was PAL because of
its superior stability to the US NTSC coding system.

Of course, now plans went ahead to convert BBC1 and ITV to 625 line and
ultimately into colour.  BBC1 started converting its equipment around 1965 and
increasingly more programmes were made in 625 line instead of 405 line. For
"Doctor Who" the change came in 1967 with "Enemy Of The World". Rather than
send out both 405 and 625 line signals to the converted sites, the new UHF
transmitters were fixed with line converters to convert 625 line signals into
405 line signals. Programmes still being made in 405 line were thus only
transmitted on VHF.  Viewers who had dual standard TV sets could (if they
could be bothered) re-tune to UHF for programmes thus designated in order to
have better resolution.

In 1969 everything was being made in 625 line and on 15th November 1969, BBC1
and ITV became official colour services, although a large number of programmes
were still being made in black and white. Lime Grove was about the last
studios to get colour equipment and they were still making black and white
material for BBC1 as late as 1973, but these were mainly news and children's
programmes. Also the various regional studios kept black and white equipment
into the seventies, as witnessed by programmes such as "Nationwide", with the
main national section of the programme being in colour but the regional opt-
outs being in b/w.

The process of bringing 625 line colour UHF to the whole country was complete
by the end of the 70s with 625 line colour signals being fed to the
transmitters and converted to 405 line b/w signals for the decreasing amount
of viewers who still had VHF TV sets.

The 405 line converters were then taken out of service with the last one at
Sutton Coldfield being turned off in 1982 although a few back up ones remained
until 1984.  After this date anyone who STILL had a VHF TV would have had to
buy a new UHF one.

I must say that transmission sites do not have and have never had the
facilities to play tapes or films.  A lot of the relays are unmanned and the
main sites only have simple caption generators for breakdown messages etc. So
your idea that recordings were actually transported around the country for
transmission is incorrect.

Telerecordings were taken for two main reasons.  The first and by far the most
important was for overseas purposes.  It meant that countries whose TV
technology was behind Britain didn't have to worry about video standards
conversion or anything. Film could be played anywhere regardless of the
standards used.  The second reason was that during the time the new UHF
transmitters on BBC1 were converting source 625 signals into 405, this would
mean that material made on 405 VT would only go out on VHF. A telerecording of
such a tape could be scanned at 625 lines and thus go out on both VHF and UHF
courtesy of the line converters at the transmitters. Tapes were also more
prone to dropouts etc and thus more difficult to store in the long run. So it
seemed logical to the archives to keep most stuff on film. Also film was much
easier to preview than VT for researchers etc.

In fact the BBC now hold almost no 405 line programmes on their original
videotape, since a great deal of this old material was returned from the BBC
Enterprise archive which (as explained above) dealt mostly with
telerecordings.  One programme I have seen transmitted off its original 405
line tape was an old 1965 "Top Of The Pops" and the quality of the picture
compared with telerecordings was remarkable.  So the surviving films of these
early "Doctor Who"s should be regarded as very much the "poor cousins" of
their videotape originals.