 CCITT T.101

ISO-IR registered character sets for Videotex use include variants of T.51, semigraphic mosaic sets, specialised C0 control codes, and four sets of specialised C1 control codes.Prestel was somewhat popular for a time, but never gained anywhere near the popularity of Ceefax.This may have been due primarily to the relatively low penetration of suitable hardware in British homes, requiring the user to pay for the terminal (today referred to as a set-top box), a monthly charge for the service, and phone bills on top of that (unlike the US, local calls were paid for in most of Europe at that time).