Teletext Tutorial (2)
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Teletext Tutorial (2) |
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In the early 1970's British broadcasters investigated extending the use of the existing UHF TV channels to carry a variety of information. Initially this was used to monitor transmitters and track network signals, but it soon became clear that sufficient data could be carried in the interval between individual TV picture fields to have wider application. After discussions with industry a common teletext standard was agreed and following extensive trials a pilot teletext service was started in 1974. Standards for both viewdata and teletext were developed which resulted in common semi-conductor technology being applicable. Both teletext and viewdata were introduced into the UK on a full commercial basis in 1976 and 1979 respectively. The relatively low cost of the equipment, its ease of usage and the use of colour and graphics in the display led to its ready acceptance by the public. Fastext, a means of reducing wait times for pages, was introduced in 1987 and helped to spread consumer acceptance. Teletext is now included as a standard feature on may European TV sets.
Variations on the original concept have been introduced by a number of countries in order to cater for linguistic or technical differences between services. The extent to which World System has been accepted throughout the world is reflected in its current use in over 30 countries, with over 40 million teletext chip sets having been shipped for set manufacture. The WST is a major step forward in the teletext system. It opens up the possibility for a truly international specification which is capable of transmitting text in nearly every language. In the United Kingdom the number of UK teletext equipped TV sets exceeds 9 million(Aug. 1992). Over 800,000 viewers now use teletext daily for business purposes, with finance pages (covering currency rates, shares, commodities, unit trusts and company news) proving very popular.
Many broadcasters are now exploiting unused capacity in the TV signal for transmission of private data as data broadcast information. Data broadcast represents a cost-effective means of transmitting private data from a central point to multiple reception sites simultaneously.
Teletext and data broadcast techniques also may be used in a variety of ways where transmission is via satellite or cable distribution systems. Teletext is particularly effective for satellite channels to distribute programme schedules to their customers. Conventional means of distributing this information e.g. newspapers, magazines etc. are costly where programmes are transmitted to many countries.
Large organisations use their own private teletext networks for in-house distribution of information. Examples include information systems for factories, hotels, shops and airports. Teletext services can often be introduced into existing broadband cable systems thereby saving installation costs. Private networks can use full field teletext systems in which the whole TV channel is used for data information, giving either a much wider range of information or a very fast access time. | |||
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