Everyone used to book their summer holidays from Teletext. The Peter Kay sketch about this is quite amusing.
I thought, though I might be wrong, back in the UK we broadcast on 650 lines, and the top or bottom 25 lines were reserved for teletext and also IIRC timing signals, that could start/stop VCRs automatically but was never used in the UK. The teletext signal was tiny in modern terms, it was extremely similar to the BBC Micro 'Mode 7' in size.
The article mentions that VHS 'compressed' the signal. I don't think that was the case, I think it filtered the analogue signal and chopped off the teletext info, but some of it used to leak through, hence the opportunity to recover it.
Then there was Macrovision that fiddled with those not-quite filtered lines to add bursts of colour that would leak through to stop tape-to-tape piracy.
Fun fact: a magazine published a circuit that would remove Macrovision that was then widely photocopied and distributed in the UK. You could order the parts from Tandy or RadioShack, and we took it to school and had (a lot) of help from the teacher putting them together as part of our CDT/tech classes. The rest, is as they say, history.
I thought, though I might be wrong, back in the UK we broadcast on 650 lines, and the top or bottom 25 lines were reserved for teletext and also IIRC timing signals, that could start/stop VCRs automatically but was never used in the UK. The teletext signal was tiny in modern terms, it was extremely similar to the BBC Micro 'Mode 7' in size.
The article mentions that VHS 'compressed' the signal. I don't think that was the case, I think it filtered the analogue signal and chopped off the teletext info, but some of it used to leak through, hence the opportunity to recover it.
Then there was Macrovision that fiddled with those not-quite filtered lines to add bursts of colour that would leak through to stop tape-to-tape piracy.
Fun fact: a magazine published a circuit that would remove Macrovision that was then widely photocopied and distributed in the UK. You could order the parts from Tandy or RadioShack, and we took it to school and had (a lot) of help from the teacher putting them together as part of our CDT/tech classes. The rest, is as they say, history.