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60-655: 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 . 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

120-464: A Windows update was incompatible with the old Cyclone system. Since NOS Teletekst is still popular in the Netherlands (with 3.5 million people using it weekly on televisions and 1 million people using it weekly as app on other devices), NOS decided to build a new modern underlying system to replace Cyclone. To make Teletekst look visually the same as on the old Cyclone system, the developers of

180-479: A design and proposal for UK broadcasters. His configuration contained all the fundamental elements of classic teletext including pages of 24 rows with 40 characters each, page selection, sub-pages of information and vertical blanking interval data transmission. A major objective for Adams during the concept development stage was to make teletext affordable to the home user. In reality, there was no scope to make an economic teletext system with 1971 technology. However, as

240-454: A method not possible given the one-way nature of broadcast teletext. Unlike the Internet , teletext is broadcast , so it does not slow down further as the number of users increases, although the greater number of pages, the longer one is likely to wait for each to be found in the cycle. For this reason, some pages (e.g. common index pages) are broadcast more than once in each cycle. Teletext

300-406: A page is requested by the user it can be loaded directly from memory instead of having to wait for the page to be transmitted. When the page is transmitted again, the decoder updates the page in memory. The text can be displayed instead of the television image, or superimposed on it (a mode commonly called mix ). Some pages, such as subtitles ( closed captioning ), are in-vision , meaning that text

360-606: A palette of eight. The proposed higher resolution Level 2 (1981) was not adopted in Britain (in-vision services from Ceefax & ORACLE did use it at various times, however, though even this was ceased by the BBC in 1996), although transmission rates were doubled from two to four lines a frame. 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

420-455: A plug-in circuit board. It took another decade before the decoders became a standard feature on almost all sets with a screen size above 15 inches (Teletext is still usually only an option for smaller "portable" sets). From the mid-1980s, both Ceefax and ORACLE were broadcasting several hundred pages on every channel, slowly changing them throughout the day. In 1986, WST was formalised as an international standard as CCIR Teletext System B. It

480-569: A similar mix of text and graphics). The most common implementation is Level 1.5 , which supports languages other than English. Virtually any TV sold in Europe since the 1990s has support for this level. After 1994 some stations adopted Level 2.5 Teletext or Hi-Text , which allows for a larger color palette and higher resolution graphics. The proposed higher content levels included geometrically specified graphics (Level 4), and higher-resolution photographic-type images (Level 5), to be conveyed using

540-491: 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. The initial Broadcast Teletext Specification set out by the BBC, IBA, BREMA in September 1976: (Level 1

600-532: A slow data rate with a suitable memory, whole pages of information could be sent and stored on the TV for later recall. In the early 1970s, work was in progress in Britain to develop such a system. The goal was to provide UK rural homes with electronic hardware that could download pages of up-to-date news, reports, facts and figures targeting UK agriculture. The original idea was the brainchild of Philips (CAL) Laboratories in 1970. In 1971, CAL engineer John Adams created

660-511: A system for the delivery of information to a user in a computer-like format, typically displayed on a television or a dumb terminal , but that designation is usually reserved for systems that provide bi-directional communication, such as Prestel or Minitel . Teletext was created in the United Kingdom in the early 1970s by John Adams, Philips ' lead designer for video display units to provide closed captioning to television shows for

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720-558: A teletext decoder using mainly TTL devices; however, development was limited until the first TV sets with built-in decoders started appearing in 1977. The "Broadcast Teletext Specification" was published in September 1976 jointly by the IBA, the BBC and the British Radio Equipment Manufacturers' Association. The new standard also made the term "teletext" generic, describing any such system. The standard

780-566: A unique pattern of bits allows the decoder to identify which lines contain data. Unused lines must not be used for other services as it will prevent teletext transmission. Some teletext services use a great number of lines, others, for reasons of bandwidth and technical issues, use fewer. Teletext in the PAL B system can use the VBI lines 6–22 in first half image and 318–334 in the other to transmit 360 data bits including clock run-in and framing code during

840-576: A very short time by NBC for their NBC Teletext service 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). 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

900-427: Is a means of sending text and simple geometric shapes to a properly equipped television screen by use of one of the " vertical blanking interval " lines that together form the dark band dividing pictures horizontally on the television screen. Transmitting and displaying subtitles was relatively easy. It requires limited bandwidth ; at a rate of perhaps a few words per second. However, it was found that by combining even

960-466: Is a standard for displaying text and rudimentary graphics on suitably equipped television sets. Teletext sends data in the broadcast signal, hidden in the invisible vertical blanking interval area at the top and bottom of the screen. The teletext decoder in the television buffers this information as a series of "pages", each given a number. The user can display chosen pages using their remote control . In broad terms, it can be considered as Videotex ,

1020-406: Is also used for carrying special packets interpreted by TVs and video recorders, containing information about subjects such as channels and programming. Teletext allows up to eight 'magazines' to be broadcast, identified by the first digit of the three-digit page number (1–8). Within each magazine there may theoretically be up to 256 pages at a given time, numbered in hexadecimal and prefixed with

1080-439: Is broadcast in the vertical blanking interval between image frames in a broadcast television signal, in numbered "pages". For example, a list of news headlines might appear on page 110; a teletext user would type "110" into the TV's remote control to view this page. The broadcaster constantly sends out pages in a sequence. There will typically be a delay of a few seconds from requesting the page and it being broadcast and displayed,

1140-447: Is digitally coded as 45-byte packets, so the resulting rate is 7,175 bits per second per line (41 7-bit 'bytes' per line, on each of 25 frames per second). A teletext page comprises one or more frames , each containing a screen-full of text. The pages are sent out one after the other in a continual loop. When the user requests a particular page the decoder simply waits for it to be sent, and then captures it for display. In order to keep

1200-405: Is displayed in a block on the screen covering part of the television image. The original standard provides a monospaced 40×24 character grid. Characters are sent using a 7-bit codec, with an 8th bit employed for error detection. The standard was improved in 1976 ( World System Teletext Level 1 ) to allow for improved appearance and the ability to individually select the color of each character from

1260-451: 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: 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: By late 2021, SWR Fernsehen stopped using

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1320-419: Is sometimes marked on televisions as CCT ( Computer-Controlled Teletext ), or ECCT ( Enhanced Computer-Controlled Teletext ). Besides the hardware implementations, it is also possible to decode teletext using a PC and video capture or DVB board, as well as recover historical teletext from self-recorded VHS tapes. The Acorn BBC Micro 's default graphics mode (mode 7) was based on teletext display, and

1380-506: The Dutch public broadcasting organization NOS replaced the original underlying system for teletext that had been in use since the 1980s with a new system. The reason behind the replacement was that the original Cyclone system became harder to maintain over the years and the NOS even had to consult sometimes retired British teletext experts to deal with issues. For example, a recent issue was that

1440-637: The SECAM standard is used in television broadcasting, a teletext system was developed in the late 1970s under the name Antiope . It had a higher data rate and was capable of dynamic page sizes, allowing more sophisticated graphics. It was phased out in favour of World System Teletext in 1991. In North America, NABTS , the North American Broadcast Teletext Specification, was developed to encoding NAPLPS teletext pages, as well as other types of digital data. NABTS

1500-413: The active video period at a rate of 6.9375 Mbit/s ±25 bit/s using binary NRZ line coding. The amplitude for a "0" is black level ±2% and a "1" is 66±6% of the difference between black and peak white level. The clock run in consist of 8 times of "10" and the framing code is "11100100". The two last bits of the clock-run in shall start within 12 +0.4 −1.0  μs from the negative flank of

1560-463: The line synchronization pulse . The 6.9375 Mbit/s rate is 444 × nominal fH , i.e. the TV line frequency. Thus 625 × 25 × 444 = 6,937,500 Hz. Each bit will then be 144 ns long. The bandwidth amplitude is 50% at 3.5 MHz and 0% at 6 MHz. If the horizontal sync pulse during the vertical synchronization starts in the middle of the horizontal scan line. Then first interlace frame will be sent, otherwise, if vertical synchronization let

1620-632: The 1980s, with almost all televisions sets including a decoder. Other standards were developed around the world, notably NABTS (CCIR Teletext System C) in the United States , Antiope (CCIR Teletext System A) in France and JTES (CCIR Teletext System D) in Japan , but these were never as popular as their European counterpart and most closed by the early 1990s. Most European teletext services continued to exist in one form or another until well into

1680-536: The 1980s. Also, Dick Smith Electronics 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 service and for

1740-436: The 2000s when the expansion of the Internet precipitated a closure of some of them. However, many European television stations continue to provide teletext services and even make teletext content available via web and dedicated apps. The recent availability of digital television has led to more advanced systems being provided that perform the same task, such as MHEG-5 in the UK, and Multimedia Home Platform . Teletext

1800-726: The BBC in 2012. In the UK the decline of Teletext was hastened by the introduction of digital television , though an aspect of teletext continues in closed captioning . In other countries the system is still widely used on standard-definition DVB broadcasts. A number of broadcast authorities have ceased the transmission of teletext services. Subtitling still continues to use teletext in Australia, New Zealand, and Singapore with some providers switching to using image-based DVB subtitling for HD broadcasts. New Zealand solely uses DVB subtitling on terrestrial transmissions despite teletext still being used on internal SDI links. Teletext information

1860-630: 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 ). Almost all television sets sold in Europe since

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1920-620: The European continent. 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 Digital System 3 line throughout

1980-518: The GPO immediately announced a 1200/75 baud videotext service under the name Prestel (this system was based on teletext protocols, but telephone-based). The TV-broadcast based systems were originally incompatible; Ceefax displayed pages of 24 lines with 32 characters each, while ORACLE offered pages of 22 lines with 40 characters each. In other ways the standards overlapped; for instance, both used 7-bit ASCII characters and other basic details. In 1974, all

2040-521: The Post Office owned the telephones, this was considered to be an excellent way to drive more customers to use the phones. In 1972, the BBC demonstrated its system, now known as Ceefax ("seeing facts", the departmental stationery used the "Cx" logo), on various news shows. The Independent Television Authority (ITA) announced its own service in 1973, known as ORACLE (Optional Reception of Announcements by Coded Line Electronics). Not to be outdone,

2100-539: The UK's General Post Office introduced the Prestel system using the same display standards but run over telephone lines using bi-directional modems rather than the send-only system used with televisions. Teletext formed the basis for the World System Teletext standard (CCIR Teletext System B), an extended version of the original system. This standard saw widespread use across Europe starting in

2160-427: The bits used. The commonly used standard B uses a fixed PAL subtitling bandwidth of 8,600 (7,680 without page/packet header) bits/s per field for a maximum of 32 characters per line per caption (maximum three captions – lines 19 – 21) for a 25 frame broadcast. While the bandwidth is greater than EIA-608 , so is the error rate with more bits encoded per field. Subtitling packets use a lot of non-boxed spacing to control

2220-456: The computer could be used to create and serve teletext-style pages over a modem connection. With a suitable adapter , the computer could receive and display teletext pages, as well as software over the BBC's Ceefax service, for a time. The Philips P2000 home computer's video logic was also based on a chip designed to provide teletext services on television sets. Some TV channels offer a service called interactive teletext to remedy some of

2280-460: The delays reasonably short, services typically only transmit a few hundred frames in total. Even with this limited number, waits can be up to 30 seconds, although teletext broadcasters can control the speed and priority with which various pages are broadcast. Modern television sets, however, usually have built-in memory, often for a few thousand different pages. This way, the teletext decoder captures every page sent out and stores it in memory, so when

2340-590: 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 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

2400-524: The end of 1974 the BBC news department put together an editorial team of nine, including and led by editor Colin McIntyre, to develop a news and information service. Initially limited to 30 pages, the Ceefax service was later expanded to 100 pages and was launched formally in 1976. Wireless World magazine ran a series of articles between November 1975 and June 1976 describing the design and construction of

2460-577: The full video line complete the second interlace frame is sent. Like EIA-608 , bits are transmitted in the order of LSB to MSB with odd parity coding of 7-bit character codes. However unlike EIA-608 , the DVB version is transmitted the same way. For single bit error recovery during transmission, the packet address (page row and magazine numbers) and header bytes (page number, subtitle flag, etc.) use hamming code 8/4 with extended packets (header extensions) using hamming 24/18, which basically doubles

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2520-403: The hearing impaired. Public teletext information services were introduced by major broadcasters in the UK, starting with the BBC 's Ceefax service in 1974. It offered a range of text-based information, typically including news, weather and TV schedules. Similar systems were subsequently introduced by other television broadcasters in the UK and mainland Europe in the following years. Meanwhile,

2580-516: The horizontal positioning of a caption and to pad out the fixed packet. The vertical caption position is determined by the packet address. In the case of the Ceefax and ORACLE systems and their successors in the UK, the teletext signal is transmitted as part of the ordinary analog TV signal but concealed from view in the Vertical Blanking Interval (VBI) television lines which do not carry picture information. The teletext signal

2640-465: The lines of the whole image, divided as every odd line, then every even line number. Lines near the top of the screen are used to synchronize the display to the signal and are not seen on-screen. Data formatted in accordance with CEPT presentation layer protocol and data syntax standard is stored in these lines, where they are not visible, using lines 6–22 on the first field and 318–335 on the second field. The system does not have to use all of these lines;

2700-489: The low cost was essential to the project's long-term success, this obstacle had to be overcome. Meanwhile, the General Post Office (GPO), whose telecommunications division later became British Telecom , had been researching a similar concept since the late 1960s, known as Viewdata . Unlike Teledata , a one-way service carried in the existing TV signal, Viewdata was a two-way system using telephones. Since

2760-528: The magazine number – for example, magazine 2 may contain pages numbered 200-2FF. In practice, however, non-decimal page numbers are rarely used as domestic teletext receivers will not have options to select hex values A-F, with such numbered pages only occasionally used for 'special' pages of interest to the broadcaster and not intended for public view. The broadcaster constantly sends out pages in sequence in one of two modes: Serial mode broadcasts every page sequentially whilst parallel mode divides VBI lines amongst

2820-546: The magazines, enabling one page from each magazine to be broadcast simultaneously. There will typically be a delay of a few seconds from requesting the page and it being broadcast and displayed, the time is entirely dependent on the number of pages being broadcast in the magazine (parallel mode) or in total (serial mode) and the number of VBI lines allocated. In parallel mode, therefore, some magazines will load faster than others. A standard PAL signal contains 625 lines of video data per screen, broken into two "fields" containing half

2880-449: The main commercial broadcaster, launched its Mediavideo Teletext in 1993. La7Video in 2001, heir to TMCvideo, the teletext of TMC Telemontecarlo born in the mids 90s. Always in the 90s, Rete A and Rete Mia teletexts arrived. Retemia's teletext has not been functional since 2000, Rete A's since 2006, La7Video since 2014 and Mediavideo since 2022. These developments are covered by the different World System Teletext Levels . In France, where

2940-533: The new system made use of reverse engineering . The World Wide Web began to take over some of the functions of teletext from the late 1990s. However, due to its broadcast nature, Teletext remained a reliable source of information during times of crisis, for example during the September 11 attacks when webpages of major news sites became inaccessible because of the high demand. As the web matured, many broadcasters ceased broadcast of Teletext — CNN in 2006 and

3000-670: The number of daily viewers reached a record of 1.17 million. In 2004, that number reached 1.3 million a day. Until 2015, SWISS TXT was responsible for the development, operation and commercialization of the Teletext service on television channels operated by the Swiss Broadcasting Corporation . Between 2005 and 2008, the Teletext editorial department was integrated into Swiss Broadcasting Corporation television channels SRF 1 , SRF zwei , RTS Un , RTS Deux , RSI La 1 , RSI La 2 operations. The multimedia sector

3060-571: The same underlying mechanism at the transport layer. No TV sets currently implement the two most sophisticated levels. The Mullard SAA5050 was a character generator chip used in the UK teletext-equipped television sets. In addition to the UK version, several variants of the chip existed with slightly different character sets for particular localizations and/or languages. These had part numbers SAA5051 (German), SAA5052 (Swedish), SAA5053 (Italian), SAA5054 (Belgian), SAA5055 (U.S. ASCII), SAA5056 (Hebrew) and SAA5057 (Cyrillic). The type of decoder circuitry

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3120-477: The services agreed on a standard for displaying the information. The display would be a simple 24 × 40 grid of text, with some graphics characters for constructing simple graphics. The standard did not define the delivery system, so both Viewdata -like and Teledata -like services could at least share the TV-side hardware (which at that time was quite expensive). Following test transmissions in 1973–74, towards

3180-579: The shortcomings of standard teletext. To use interactive teletext, the user calls a special telephone number with a push-button telephone . A computer then instructs them to go to a teletext page which is assigned to them for that session. SWISS TXT The company was founded on 23 December 1983 with a licence granted by the Swiss Federal Council Teletext Licence. The Teletext service started operations on SF DRS in 1984, on TSR in 1985 and on TSI in 1986. In 2001,

3240-422: 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. New features: (Level 3

3300-460: The time being entirely dependent on the number of pages being broadcast. More sophisticated receivers use a memory buffer to store some or all of the teletext pages as they are broadcast, allowing almost instant display from the buffer. This basic architecture separates teletext from other digital information systems, such as the Internet, whereby pages are 'requested' and then 'sent' to the user –

3360-463: Was also adopted in many other European countries. Besides the US and UK developments, a number of similar teletext services were developed in other countries, some of which attempted to address the limitations of the initial British-developed system, by adding extended character sets or improving graphic abilities. For example, state-owned RAI launched its teletext service, called Televideo , in 1984, with support for Latin character set . Mediaset ,

3420-668: Was internationalised as World System Teletext (WST) by CCIR . Other systems entered commercial service, like ORACLE (first broadcast on the ITV network in 1978) and Prestel (in 1979). Teletext became popular in the United Kingdom when Ceefax, Oracle and the British government promoted teletext through a massive campaign in 1981. By 1982, there were two million such sets, and by the mid-1980s they were available as an option for almost every European TV set, typically by means of

3480-455: Was replaced by level 1.5) An extended version of level 1, with support for 13 extended character sets and other ASCII -like characters. This is the most common system and still used by most TV channels as of 2021. World System Teletext Level 2 was introduced in 1988. New features were: (Level 2 was replaced by level 2.5) Level 2.5 or HiText . was first broadcast in 1994 by the bilingual French-German channel ARTE . With Level 2.5 it

3540-451: Was replaced by level 3.5) Level 3.5 extends the number of re-definable characters and their complexity and introduces different font styles and proportional spacing . New features: Level 4 was proposed in 1981 and tested by IBA . No TV set implements this level. Level 5 allows full-definition still pictures with better quality than video cameras. No TV set implements this level. Teletext Teletext , or broadcast teletext ,

3600-474: Was the standard used for both CBS's ExtraVision and NBC's NBC Teletext services in the mid-1980s. Japan developed its own JTES teletext system with support for Chinese, Katakana and Hiragana characters. Broadcasts started in 1983 by NHK . In 1986, the four existing teletext systems were adopted into the international standard CCIR 653 (now ITU-R BT.653) as CCIR Teletext System A (Antiope), B (World System Teletext), C (NABTS) and D (JTES). In 2023,

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