World System Teletext (WST) is the name of a standard for encoding and displaying
teletext information, which is used as the standard for teletext throughout
Europe today. It was adopted into the international standard
CCIR 653 (now
ITU-R BT.653) of 1986 as CCIR Teletext System B.
Development
WST originally stems from the UK standard developed by the
BBC and the UK
Independent Broadcasting Authority in 1974 for teletext transmission, extended in 1976 as the Broadcast Teletext Specification. With some tweaks to allow for alternative
national character sets, and adaptations to the
NTSC 525-line system as necessary, this was then promoted internationally as "World System Teletext". It was accepted by
CCIR in 1986 under international standard CCIR 653 (now
ITU-R BT.653) as one of four recognised standards for teletext worldwide (most commonly referred to as CCIR Teletext System B).
WST 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 ''
Ceefax'' from the
BBC and services from
''Teletext'' on
ITV
ITV or iTV may refer to:
ITV
*Independent Television (ITV), a British television network, consisting of:
** ITV (TV network), a free-to-air national commercial television network covering the United Kingdom, the Isle of Man, and the Channel Islan ...
in the
United Kingdom, ''ZDFtext'' from
ZDF and ''ARDText'' from
ARD in
Germany, and ''Tekst-TV'' from
NRK in
Norway, among many other teletext services offered by other television networks throughout the European continent.
WST in the United States
WST saw some use in the
United States in the 1980s, for the
''Electra'' service, which was carried on SuperStation WTBS (now
TBS). It was also used for other teletext services on other television stations and networks in the US.
Zenith in the US also included built-in WST teletext decoders in their higher-end models of TV sets, such as their line throughout the 1980s. Also,
Dick Smith Electronics
Dick Smith Holdings Limited (formerly Dick Smith, Dick Smith Electronics or DSE) was an Australian chain of retail stores that sold consumer electronics goods, hobbyist electronic components, and electronic project kits. The chain expanded succ ...
offered through their American distributors a WST teletext decoder in the form of a set-top box, which was sold as a kit.
This was all in competition to another teletext standard developed exclusively in North America,
NABTS (North American Broadcast Teletext Standard). It was developed in Canada by
Norpak, and was used by
CBS for their ''
ExtraVision
ExtraVision was a short-lived teletext service created and operated by the American television network CBS in the early to mid-1980s. It was carried in the vertical blanking interval of the video from local affiliate stations of the CBS network. ...
'' service and for a very short time by
NBC for their
''NBC Teletext'' in the mid-1980s. However, NABTS never became as successful as WST in the American continent, since NABTS was a more advanced technology, which required a much more complicated and expensive decoder (even though it had improved graphics capability over WST).
Levels
In the early 1980s a number of higher extension levels were envisaged for the specification, based on ideas then being promoted for worldwide
videotex standards (telephone dial-up services offering a similar mix of text and graphics). The proposed higher content levels included geometrically-specified graphics (Level 4), and higher-resolution photographic-type images (Level 5), to be conveyed using the same underlying mechanism at the transport layer. No TV sets currently implement the two most sophisticated levels.
Level 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 the
TRS-80 character set)
* spacing attributes
* fixed colour palette (red, green, yellow, blue, magenta, cyan, white over a black background)
* support for double height or flash effect
* 40 columns × 24 rows character grid
Level 1.5 (1981)

An extended version of level 1, with support for 13 extended
character sets and other
ASCII-like characters.
*Czech and Slovak
*English
*Estonian
*French
*German
*Italian
*Latvian and Lithuanian
*Polish
*Portuguese and Spanish
*Romanian
*Serbian, Croatian and Slovenian
*Danish, Swedish and Finnish
*Turkish
This is the most common system and still used by most TV channels as of 2021.
Level 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 channel
ARTE. With Level 2.5 it is possible to set a background colour and have higher resolution text and images. The system was adopted initially by ARTE, ARD, ZDF,
Bayern 3 and
SwissTXT.
New features of Level 2.5 teletext:
* Multi-language support
* Wider colour palette with re-definable colours (4,016 colour palette
)
* Non-spacing attributes
* Allows re-definable characters
* Provides side panels for additional text or graphics in
16:9 TVs
*
nexTView EPG
The system has not been widely implemented, with only a handful of European state broadcasters supporting it.
Television stations which are known to transmit Level 2.5 teletext in the late 2010s include:
* Netherlands: public broadcaster
NOS (background colour on all pages, and a test page with hi-res graphics),
* France:
France 3
* Germany:
**
ZDF (some pages),
**
3sat
In logic and computer science, the Boolean satisfiability problem (sometimes called propositional satisfiability problem and abbreviated SATISFIABILITY, SAT or B-SAT) is the problem of determining if there exists an interpretation that satisfie ...
(some pages)
**
Bayerisches Fernsehen (and formerly also now-renamed
BR-alpha) (in the past on almost all pages, now only on some pages),
**
phoenix (on some pages),
** Bürgerfernsehen Gera (background-colour on all pages, test pages 460 to 485) and
**
SWR Fernsehen
SWR Fernsehen is a German regional television channel targeting the states of Baden-Württemberg and Rhineland-Palatinate. It is produced by Südwestrundfunk (SWR) and is one of eight regional "third channels" broadcast by the ARD members.
Hist ...
(included completely backwards-compatible Level 2.5 teletext, with higher quality text and graphics on nearly all pages).
By late 2021, SWR Fernsehen stopped using the system, but ZDF, 3sat, Bayerisches Fernsehen and Phoenix has at least some Level 2.5 enhanced pages.
One of the problems with Level 2.5 is that it often takes several transmission cycles before the higher resolution items show on the screen. In order to watch Level 2.5 teletext, a rather recent television set with a special decoder chip is required. If not, Level 1.5 text will be shown.
Level 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 and
proportional spacing.
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
* Different font styles
* Proportional spacing.
Level 4 (1981)
Level 4 was proposed in 1981 and tested by
IBA. No TV set implements this level.
*
Vector graphics in resolutions of 320×256
* Needs computing power to generate the display from a sequence of drawing instructions
* 250,000 colours palette
Level 5
Level 5 allows full-definition still pictures with better quality than video cameras.
No TV set implements this level.
*
Modulated onto a
carrier
Carrier may refer to:
Entertainment
* ''Carrier'' (album), a 2013 album by The Dodos
* ''Carrier'' (board game), a South Pacific World War II board game
* ''Carrier'' (TV series), a ten-part documentary miniseries that aired on PBS in April 20 ...
* No noise added to the picture during transmission
*
Image compression
Image compression is a type of data compression applied to digital images, to reduce their cost for storage or transmission. Algorithms may take advantage of visual perception and the statistical properties of image data to provide superior r ...
used
See also
*
Antiope - French teletext standard (CCIR Teletext System A)
*
NABTS – North American Teletext Specification (CCIR Teletext System C)
*
JTES - Japanese Teletext Specification (CCIR Teletext System D)
*
NAPLPS
NAPLPS (North American Presentation Level Protocol Syntax) is a graphics language for use originally with videotex and teletext services. NAPLPS was developed from the Telidon system developed in Canada, with a small number of additions from AT&T ...
– North American Presentation Level Protocol Syntax
*
Mullard SAA5050
The Mullard SAA5050 was a character generator chip for implementing the Teletext character set. The SAA5050 was used in teletext-equipped television sets, viewdata terminals, and microcomputers, most notably on computers like the Philips P2000 ...
a popular teletext decoder chip
*
List of teletext services
*
Teletext character set
*
Text semigraphics
Text-based semigraphics or pseudographics is a primitive method used in early text mode video hardware to emulate raster graphics without having to implement the logic for such a display mode.
There are two different ways to accomplish the em ...
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 (now
ITU-R BT.653) set of four standards for teletext systems worldwide. Adopted 1986. Revisions 2 and 3 were published in 1993 and 1998. WST was formalised by this standard as CCIR Teletext System B.
Enhanced Teletext specification ETS 300 706 (ETSI, 1997)Version 1.2.1, April 2003 Current European standard for CCIR Teletext System B.
References
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Teletext