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tesandco761 posts since 28 Sep 2001
Granada North West Today
Well if you ever wonder how people used to shout about their strange TV fantasies to the world before TV Forum existed, then wonder no more...

*


Almost makes you curious now if the postbag back in the day may have been filled with fantasy TV schedules and people drawing really badly squashed mock idents on A4 paper!
TV Whirl - Still covering UK idents, presentation, teletext and programmes after 16 years
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Steve in Pudsey7,878 posts since 4 Jan 2003
Yorkshire Look North (Yorkshire)
I remember the "clock cracker" page that was part of the 600s on ITV, don't have the slightest clue what it was for though!


It was a stress-test for receivers, that particular pattern was quite processor intensive so if it could be displayed without causing issues all was good. Processors used to be known as the clock.

Some of them also had identification built in, such as the C4 one which identified where playout was coming from (HFR - Horseferry Road - I believe this changed when they used their disaster recovery facility) and the macro-region (eg NORTH).
Write that down in your copybook now.
Orry Verducci1,544 posts since 1 Feb 2005
Granada North West Today
I remember the "clock cracker" page that was part of the 600s on ITV, don't have the slightest clue what it was for though!


It was a stress-test for receivers, that particular pattern was quite processor intensive so if it could be displayed without causing issues all was good. Processors used to be known as the clock.

They were also a test for the teletext inserters which added the teletext signal to the VBI, which is why you'll find a clock cracker of some form on every service.


For teletext to work correctly the 'dots' in the signal which represent the bits of data needed to be in exactly the right place, or the TV would interpret the bits to be at different places in the data, resulting in incorrectly displayed services.

Each inserter had a clock, which had to be in sync with the video signal and switching bits at exactly the right time in order to keep everything functioning. The block and divide symbols together, in bits, represented all 1's with a single 0 at the end. This combination essentially continually stress tested the inserter clocks, as the continuous stream of 1's made it easier for the clock to loose time (they weren't as precise back then as they are now, and easily lost sync if the data wasn't always changing). It also made it easy for engineers to see if the data stream was out of time with the video sync pulse, as all the characters would change, and what they changed allowed them work out exactly how much it was out of sync.
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Inspector Sands10,527 posts since 25 Aug 2004
Aha, found it:
http://al.robotfuzz.com/~al/teletext/itv/1996-01-03-0021.4/379.html

The list on the right are the transmitters that Teletext was inserted. Where there were more than one version in a region the transmitter name and region name is used, so Yorkshire has YOR and BEL - Emley Moor and Belmont for example . FUL is Fulham - Teletext's HQ. The numbers show the queues of pages to each

I think there's a few characters wrong in there. TZN should be TYN, BOT should be BOR and YOU should be YOR, MET = MER, GUM is GRM etc
There's another from another archive that has different mistakes: http://archive.teletextart.co.uk/cen-19941210/379.html
Last edited by Inspector Sands on 29 December 2016 7:49pm - 3 times in total
MY83103 posts since 16 Nov 2016
I seem to remember discovering the clock cracker as the page number was actually listed on Yorkshire's ancialliary pages (the 600s), and I think possible 4-tel as well. Though I can't understand why really, it isn't something for the regular viewer.


4-Tel's was 399 wasn't it?
Neil Jones3,413 posts since 23 Dec 2001
Central (West) Midlands Today
Sudden thought or random observation (whatever floats your boat), I don't think TV-AM ever did anything themselves with a teletext service of sorts, however http://teletext.mb21.co.uk/gallery/oracle/main1.shtml suggests they had a page all to themselves on page 175 of ORACLE, though I can't remember this ever being promoted on the channel itself.

After 1993 and GMTV, they did have IIRC their own branded magazine in the 600s that replaced the regions between 6am and 9:25am. The above page suggests it was not possible to do the regional teletext during TV-AM's hours, presumably because it was a national service.