Videoplus

[owner2]

Is there someone out there whose job it is to choose the videoplus numbers? There must be some sort of system but it looks random in the tv listings!

[Hippy]

There is no-one who does this, the numbers are generated by a arithmetical algorithm that combines the date, channel info, start and finish times into a long string of digits that the Video Plus+ decoder can reverse translate. It is a bit like the barcodes at the shops. The cash till readers understand what the product is from the string of numbers, although I will admit that humans have chosen the numbers in this case rather than generated them automatically.

http://www.domtools.com/unix/vcrplus.shtml is one chap's take on the algorithm, which of course is the copyright of Gemstar-TV, the nice people that invented the system.

I think that the broadcasters have a clever method of triggering your VCR by sending pulses in the video signal to tell Video Plus+ recorders that the particular programme is here, so catering for delays or badly set VCR clocks.