CEEFAX: A Proposed New Broadcasting Service

Field trials are being completed of a BBC system which can transmit a “magazine” of 32 “pages” of text for display on a home TV screen. The information is conveyed in digital form using the ASCII 7-bit code. In the 625-line 50-field television system the data signal is inserted on lines 17 and 18 together with the corresponding lines (330 and 331) in the alternate field and the bit rate of 4.5 Mb/s during the transmission of the signal leads to an average bit rate of 23.4 kb/s. The complete magazine is sent in 15.36 s. Special CEEFAX TV receivers or adapters for use will ordinary sets decode the signals and store the data for the page selected by the user: the store is read every field via character-generating circuits which provide the video signals to form the alphanumeric display. Weather forecasts, news items, and subtitles are among the subjects suitable for CEEFAX which could also be adapted to take library reference material, bank statements, etc. from the telephone line or a shelf-full of books from a single video disc. A Technical Study Group is examining this system, a comparable one developed by the Independent Broadcasting Authority, and proposals from British industry, and will recommend characteristics for a single data broadcasting service.

Print ISSN

0361-4573

Published

1974-01

Content type

Original Research

DOI

10.5594/J07617