Teletext was developed in the UK and launched there on 23 September 1974. Well over half the television sets sold were fitted with Teletext decoders and it was often the first source of choice for up-to-the-minute news, sport and lottery results, especially as there were no charges for phone calls or online usage (unlike the earlier Prestel service operated by the UK’s Post Office and later BT).
The analogue Teletext system was transmitted as a series of 45-byte packets, one per TV scan line. It was possible for every line of the TV signal to carry Teletext, but to avoid the appearance of snow on a video picture, the lines used were limited to those which were not visible because they occured during the TV vertical blanking interval (lines 6 to 22 and 318 to 335).
With a maximum of but seven colours and chunky text, the system looked dated, especially when compared to later digital offerings.
Around the world the system wents by different names with each service offering similar free on-screen information:
- Canada: Telidon
- France: Antiope
- USA: Elektra, Wave Top, Guide+, Star Sight