ExtraVision was a short-lived
teletext
A British Ceefax football index page from October 2009, showing the three-digit page numbers for a variety of football news stories
Teletext, or broadcast teletext, is a standard for displaying text and rudimentary graphics on suitably equipp ...
service created and operated by the American
television network
A television network or television broadcaster is a telecommunications network for distribution of television program content, where a central operation provides programming to many television stations or pay television providers. Until the mid- ...
CBS
CBS Broadcasting Inc., commonly shortened to CBS, the abbreviation of its former legal name Columbia Broadcasting System, is an American commercial broadcast television and radio network serving as the flagship property of the CBS Entertainm ...
in the early to mid-1980s. It was carried in the
vertical blanking interval
In a raster scan display, the vertical blanking interval (VBI), also known as the vertical interval or VBLANK, is the time between the end of the final visible line of a frame or field and the beginning of the first visible line of the next fra ...
of the video from local affiliate stations of the CBS network. It featured CBS program information, news, sports, weather, even subtitling
for CBS programming (much like page 888 in British/European teletext, and American
closed captioning
Closed captioning (CC) and subtitling are both processes of displaying text on a television, video screen, or other visual display to provide additional or interpretive information. Both are typically used as a transcription of the audio po ...
). ExtraVision could also have its pages customized by the local affiliate station carrying it, for such things as program schedules, local community announcements, and station promotions.
ExtraVision was discontinued by CBS towards the end of the 1980s, due to the service using the
NABTS
NABTS, the North American Broadcast Teletext Specification, is a protocol used for encoding NAPLPS-encoded teletext pages, as well as other types of digital data, within the vertical blanking interval (VBI) of an analog video signal. It is standar ...
protocol, which required a quite expensive decoder to receive the service. Also, most of the local CBS affiliates carrying the ExtraVision service did not bother to invest in the computer equipment required to customize pages to carry locally oriented information on the service.
CBS had begun tests in 1979 using the French
Antiope system,
and again in 1981 in the Los Angeles area. The full ExtraVision service began in April 1983
on CBS affiliate
WBTV
WBTV (channel 3) is a television station in Charlotte, North Carolina, United States, affiliated with CBS and owned by Gray Television. The station's studios are located off Morehead Street, just west of Uptown Charlotte, and its transmitter i ...
in Charlotte, NC, and went nationwide in 1984. It was cancelled in 1988,
three years after
NBC Teletext
NBC Teletext was a teletext service provided by the NBC, based on the NABTS standard.
Initial trials started in Los Angeles in 1981. Transmissions started as a regular service on May 16, 1983 after FCC approval, in parallel with CBS similar '' Ex ...
had also been abandoned by
NBC
The National Broadcasting Company (NBC) is an American English-language commercial broadcast television and radio network. The flagship property of the NBC Entertainment division of NBCUniversal, a division of Comcast, its headquarters are l ...
.
References
External links
Print advertisement for Extravision* Ed Ellers
Teletext in the United States of America
{{Teletext
CBS Television Network
Teletext