Wikipedia
ExtraVision was a short-lived teletext service created and operated by the American television network CBS in the early to mid-1980s. It was carried in the vertical blanking interval 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). 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. 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 1983 on CBS affiliate WBTV in Charlotte, NC, and went nationwide in 1984. It was cancelled in 1986, a year after teletext had also been abandoned by NBC.