Teletext Signal Generation Equipment and Systems

Various systems for utilising the spare time in the vertical blanking interval of a normal television waveform have been proposed as a means of transmitting additional information for engineering tests and for other purposes. Broadly speaking, none of these systems have been viable for home use because of the cost of decoding the information. The advent of large scale integrated circuits (LSI) has changed this situation. In 1972 broadcasting authorities in the United Kingdom proposed systems for transmitting information in diqitally coded forms during the vertical blanking period for display on the home t.v. receiver. Initially these systems had slightly different technical parameters but as the result of development activity involvinq the broadcasting authorities and various receiver manufacturers a unified system was evolved and has been used by both authorities since 1974 (Reference 1.)