International Captioning Project
History of Teletext
Teletext is a system of transmitting digitally coded data in the vertical blanking interval without disturbing the normal visual and audio information. The teletext service itself consists of "pages" of information accessible by selecting special numbers from a television's remote-control unit. Information of all types is literally available at the touch of a button or two, including news, sports, weather, finance, travel, TV/radio listings and games. If the viewer wanted to view the weathercast, for example, s/he would select a specific page number to see a written, or even graphic, display of the weather for the next few days.
Teletext was developed in the early 1970s by engineers at the British Broadcasting Company (BBC) and ITC (then known as IBA), the regulating body of commercial networks in the United Kingdom. Initially, the BBC had been researching ways to subtitle programs for the deaf and hard-of-hearing community, an idea which, at first, was not considered economically feasible. However, newly developed technology made it possible to expand the subtitling idea to include many pages of information in addition to subtitles, which would make it useful to all viewers. This proposed system was dubbed Ceefax, and in 1974 it was put into experimental use on the BBC. At nearly the same time, ITC was developing its own system to include information in the VBI. Named Oracle (Optical Reception of Announcements by Coded Line Electronics), this system was put into experimental use in 1974. Both systems provided viewers with access to news, sports, weather, business reports, etc.
In 1974, the original teletext specification was published. An essential feature of the specification was that future television receivers would be able to offer teletext at a progressively lower cost to consumers. This would ensure that decoders would eventually be incorporated into all receivers, and thus teletext would gain general public acceptance. Character sets other than English would eventually have to be incorporated to make the system useful to as many countries as possible, and the signal itself would have to be robust so that satisfactory reception could be achieved in hard-to-reach areas. Finally, the specification made provisions for the transmission of subtitles, as well. In 1976, these features, as well as others designed to improve the display of information, (including double- height characters and the use of colored backgrounds), were published in a revised teletext specification. The same year, the world's first public teletext service was put into general use in England.
However, these specifications were drawn up before the advent of home video and home video recording. Although an excellent system for broadcast, it has not been modified over the years to accommodate the many new and changing ways that viewers worldwide watch television.
While teletext was undergoing development in England, France was proposing its own system, known as Antiope. This system, first used in 1977, was designed to transmit data over telephone lines, but failed to make use of many of the characteristics of the television signal. In Canada, the Telidon system was being developed and tested. Telidon was designed to produce very high-quality graphics, which required a complex decoder in order to be made visibleÑ something not available to the consumer market at that time.
By 1984, as a result of continued development and use by countries other than the UK, the teletext system originated in England evolved into what is now known as World System Teletext (WST). An enhanced version of WST is now used by more than 30 countries worldwide, utilizing decoders installed in television receivers which add little, if anything, to the cost of the sets. The service is available in five "levels", with each level showing an increasing array of enhancements and graphics sophistication. The higher levels require more complex decoding devices with progressively larger memories capable of storing great numbers of teletext pages; thus, receivers capable of decoding levels three, four and five may cost somewhat more than their less-sophisticated counterparts.
The teletext information itself is digitally encoded in the vertical blanking interval on lines 17 thru 20, and is broadcast along with the normal video signal. Statistics on its use began to be compiled in 1979. In 1983 there were ten countries offering the service: Germany, Austria, Belgium, France, Italy, Norway, the Netherlands, the United Kingdom, Spain and Sweden. The total audience at that time was approximately five million households. In 1992, the last year for which statistics are available, a total of 20 organizations, representing 18 countries, reported an audience of more than 30 million people with access to over 9,000 total pages of information.
