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Comparing the pre-1976 teletext control codes with the post-76, Level 1 codes - here's a page in Level 1 and the same page as viewed in a pre-1976 decoder. Pre 1976 there is no double height, no conceal/reveal and the alphanumeric colour codes are in a different place. grim_fandango photo

Finally, here's another page I was able to recover (there aren't many) - about the Channel Islands. Mentions of Burtons and Woolworths, but no Benest's of Millbrook @ChannelArchive (1976) (tape h/t Rory Clark) grim_fandango photo

Back to 1976 again, and here's a schematic of the ORACLE system. Who knows what any of it means, there is no key. Note the header row - there is a 'p' before the page number and the time format is (thanks to Rory Clark for the tape) grim_fandango photo

Some great news: the oldest recovery so far is a partial 1976 ORACLE service. I've shared it before, but the attribute codes were different in those days so I didn't know what colours etc. things should be. Well, I found the pre-1976 codes! Here's P100 in its proper colours! grim_fandango photo

This is what the teletext data stream looks like when broadcast over D-MAC, an early satellite broadcasting format. It’s the dots just above the picture parts.
grim_fandango photo
Philip Heron @fsphil
@grim_fandango @ZXGuesser It's sent in the sound/data burst and/or lines in the blanking interval. They're both using duobinary coding and don't get passed to the TV, it's decoded by an onboard chip. I'm using the field blanking lines here: