Development
WST originally stems from the UK standard developed by theWST in Europe
Almost all television sets sold in Europe since the early '80s have built-in WST-standard teletext decoders as a feature. WST is used for all teletext services in Europe & Scandinavia, including ''WST in the United States
WST saw some use in theLevels
In the early 1980s a number of higher extension levels were envisaged for the specification, based on ideas then being promoted for worldwideLevel 1 (1976)
The initial Broadcast Teletext Specification set out by the BBC, IBA, BREMA in September 1976: * ''Alpha-mosaic characters'' (drawn using a 2×3 block matrix) characters (similar to some characters of theLevel 1.5 (1981)
An extended version of level 1, with support for 13 extendedLevel 2 (1988)
World System Teletext Level 2 was introduced in 1988. New features were: * Multi-language support * 32 colour mode. * Non-spacing attributes * Allows re-definable characters (Level 2 was replaced by level 2.5)Level 2.5 teletext / Hi-Text (1995)
Level 2.5 or ''HiText''. was first broadcast in 1994 by the bilingual French-German channelLevel 3
New features: * Dynamically Redefined Character Set (DRCS) allowing the display of non- Roman characters (e.g. Arabic and Chinese) * Pictorial graphic characters can also be defined (Level 3 was replaced by level 3.5)Level 3.5 (1997)
Extends the number of re-definable characters and their complexity and introduces different font styles andLevel 4 (1981)
Level 4 was proposed in 1981 and tested by IBA. No TV set implements this level. *Level 5
Level 5 allows full-definition still pictures with better quality than video cameras. No TV set implements this level. *See also
* Antiope - French teletext standard (CCIR Teletext System A) *Further reading
* ''World System Teletext Technical Specification'', UK Department of Trade and Industry, 1985. Also retitled as ''World System Teletext and Data Broadcasting System Technical Specification'', various revisions until 1989. * CCIR 653 (nowReferences
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