ExtraVision was a short-lived teletext service created and operated by the American television networkCBS in the early 1980s. It was carried in the VBI 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 British/European teletext and American closed captioning). ExtraVision could also have its pages customized by the local affiliate station carrying it, for such things as program schedules, community announcements, and station promotions. A BBC Ceefax page from the 10th September 1999 Teletext is an information retrieval service provided by television broadcast companies. ... A television network is a distribution network for television content whereby a central operation provides programming for many television stations. ... CBS (Columbia Broadcasting System) is a major television network and radio broadcaster in the United States. ... The vertical blanking interval (VBI) is an interval in a television or VDU signal that temporarily suspends transmission of the signal for the electron gun to move back up to the first line of the television screen to trace the next screen field. ... A commonly-used symbol indicating that a program or movie is closed-captioned Closed captioning (CC) allows deaf and hard of hearing / hearing-impaired people, people learning English as an additional language, people first learning how to read, and others to read a transcript or dialogue of the audio portion...
ExtraVision ws discontinued by CBS towards the end of the 80s, due to the service using the NABTS protocol, which required a quite expensive decoder to receive the service. Also, most of the local CBS affiliates carrying the ExtraVision service didn't bother to invest in the computer equipment required to create and/or modify pages on the service. NABTS (North American Broadcast Teletext Specification) is a protocol utilized for the encoding of digital data within the VBI (vertical blanking interval) of an analog video signal. ...
ExtraVision was a short-lived teletext service created and operated by the American television network CBS in the early 1980s.
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 80s, due to the service using the NABTS protocol, which required a quite expensive decoder to receive the service.
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