Teletext often carries important information, such as subtitles in various languages and for the hearing impaired viewers, as well as, in the future, coded sound commentary for the visual impaired viewers and similar ancillary programme-related services; teletext signals are inserted in the vertical interval of analogue television broadcast signals; future digital broadcasts will carry ancillary data information within special data packets of the transmitted digital programme multiplex signal; such ancillary data services thus provide important added value to television programmes,to the benefit of the television audience, and they are of great interest to broadcasters; television programmes received in the home are often recorded on consumer video cassettes;there is a large market for television programmes prerecorded on consumer video cassettes; up to now, only special versions of consumer video cassette recorders allow the recording and replay of ancillary data information; there will be new digital formats for consumer use in the future.