Bildschirmtext

Bildschirmtext (German "screen text", abbrev. Btx or BTX) was a V.23 online service (an interactive videotex system) launched in West Germany in 1983 by the Deutsche Bundespost, the (West) German postal service. Btx originally required special hardware, which had to be bought or rented from the post office. The data was transmitted through the telephone network and the content was displayed on a television set.