BBC Micro depth, resolution and memory economy. In the first models, the OS and applications were left with the RAM left over from the display mode. Mode 7 was a Teletext mode, extremely economical on memory and an original requirement due to the BBC's own use of broadcast teletext (Ceefax). It also made the computer useful as a Prestel terminal. The teletext characters were generated on board, for use with monitors and TV sets without a Teletext receiver. Train time displays at UK stations were driven by BBC Master computers in this mode until around the late 1990s. Mode 7 used only
Teletext Services (XDS). NABTS was originally developed as a protocol by the Canadian Department of Communications, with their industry partner Norpak, for the Telidon system. It was similar to the European World System Teletext (WST, aka CCIR Teletext System B), but differences between the European and North American television standards and the greater flexibility of the Telidon standard led to the creation of a new delivery mechanism that was tuned for speed. First demonstrated in the United States in 1978, NABTS was the standard used for both CBS's ExtraVision and NBC's very short-lived NBC Teletext services in the mid-1980s. Station KSL-TV