videotext
Videotext is a term applied to a family of information services that embed textual and simple graphical data within a television broadcast signal. The earliest implementations emerged in the late 1960s and early 1970s, predominantly in Europe, and they used the spare time slots of analogue television broadcasting to transmit page-based information to compatible set‑top receivers. The most well‑known of these services is the British Teletext system introduced by the BBC in 1974, which became a model for similar services across continental Europe and in other countries, including the German Das Fernsehen, the French Teletext, and the Latvian Videotext. In North America, a analogous service called Information Cable Service (ICS) appeared in the United States during the 1980s.
The core technology relied on a form of line‑repeating modulation. Textual characters were encoded as 7‑bit
Because the signal was inaccessible to the consumer’s regular television, dedicated decoders or integrated receivers were