By Gary W. Stanton, Southern Satellite Systems
A teletext signal has been continuously transmitted on the vertical interval of Satcom I, transponder 6 since the NCTA show in 1980. The original purpose was the video dissemination of cable news services. Recently, the system has been modified to incorporate data transmission which emulates a standard telephone line, but with far higher data reliability. In addition, the modified teletext system for data transmission incorporates an addressability function with over five million addresses possible. A priority scheme for national, regional, local and individual addressing is described. A description of the system, including data from reliability tests is presented. This will also define several key technical requirements for successful teletext data reception.