Teletext (or broadcast teletext) is a television information retrieval
service created in the
United Kingdom in the early 1970s by the
Philips Lead Designer for VDUs, John Adams.
Teletext is a means of
sending pages of text and simple geometric shapes from mosaic blocks
VBI decoder equipped television screen by use of a number of
reserved vertical blanking interval lines that together form the dark
band dividing pictures horizontally on the television screen. It
offers a range of text-based information, typically including news,
weather and TV schedules. Paged subtitle (or closed captioning)
information is also transmitted within the television signal.
It is closely linked to the
PAL broadcast system used in Europe. Other
teletext systems have been developed to work with the
SECAM and NTSC
systems, but teletext failed to gain widespread acceptance in North
America and other areas where
NTSC is used. In contrast, teletext is
nearly ubiquitous across
Europe as well as some other regions, with
most major broadcasters providing a teletext service. Common teletext
services include TV schedules, regularly updated current affairs and
sport news, simple games (such as quizzes) and subtitles (or closed
Teletext is broadcast 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 sequence. There will typically be a
delay of a few seconds from requesting the page and it being broadcast
and displayed, the time being entirely dependent in the number of
pages being broadcast. More sophisticated receivers use a buffer
memory to store some or all of the teletext pages as they are
broadcast, allowing instant display from the buffer.
This basic architecture separates from other digital information
systems, such as the internet, whereby pages are 'requested' and then
'sent' to the user – 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 increase,
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.
It has proved to be a reliable text news service during events such as
the September 11 terrorist attacks, during which the webpages of major
news sites became inaccessible because of the high demand. Teletext
is also used for carrying special packets interpreted by TVs and video
recorders, containing information about channels, programming, etc.
(see Later developments).
Although the term "teletext" tends to be used to refer to the
PAL-based system, or variants, 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
3 North America
3.1 North American Broadcast
3.2 World System Teletext
4 Other systems
5.1 Data transmission
6 Later developments
Video Program System
6.2 Interactive teletext
6.3 Digital teletext
6.4 Cessation of informational service
7 See also
9 External links
Teletext 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 a slow data rate with a suitable
memory, whole pages of information could be sent and stored in 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 U.K. agriculture. The original idea was the
Philips (CAL) Laboratories in 1970.
In 1971, CAL engineer John Adams created a design and proposal for UK
broadcasters. His configuration contained all the fundamental elements
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
Teletext affordable to the home user. In reality, there was no
scope to make an economic
Teletext system with 1971 technology.
However, as low cost was essential to the project's long term success,
this obstacle had to be overcome.
General Post Office
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 which
was a one-way service carried in the existing TV signal,
a two-way system using telephones. Since 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 their system, now known as
facts", the departmental stationery used the "Cx" logo), on various
news shows. The Independent
Television Authority (ITA) announced their
own service in 1973, known as ORACLE (Optional Reception of
Announcements by Coded Line Electronics). Not to be outdone, the GPO
immediately announced a 1200/75 baud videotext service under the name
The first teletext test transmissions were made by
Ceefax in 1973.
After proliferation of the
BBC system in the UK, it was adopted in
Europe and standardised as
World System Teletext
World System Teletext (WST). The World Wide
Web began to take over some of the functions of teletext from the late
1990s and many broadcasters have ceased broadcast of teletext—CNN in
2006 and the
BBC in 2012. In the UK the decline of teletext has been
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 teletext services have been syndicated to web viewers,
which mimic the look and feel of broadcast teletext.
RSS feeds of news
and information from the
BBC are presented in
Ceefax format in the web
viewer at PagesFromCeefax.net.
In 2016, the Teefax teletext service was launched in the United
Kingdom to coverage by the BBC, ITV and others. Using a
Raspberry Pi computer card as a set-top box, it feeds its service to
standard televisions. Teefax content is a mix of crowdsourcing,
syndication and contributions from media professionals who contributed
heavily to broadcast teletext services. Teefax is also syndicated to a
The 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 the services agreed 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 point in time was quite expensive).
Following test transmissions in 1973–74, towards 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. It was
followed quickly by ORACLE and Prestel.
Wireless World magazine ran a
series of articles between November 1975 and June 1976 describing the
design and construction of a teletext decoder using mainly TTL
devices; however, development was limited until the first TV sets with
built-in decoders started appearing in 1977.
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 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.
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 was
World System Teletext
World System Teletext (WST), formalised as an
international standard by CCIR in 1986 as CCIR
Teletext System B.
Comparison between teletext Level 1.0 and teletext Level 2.5.
Main article: World_System_
Teletext § 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 most common implementation is Level 1.5, that supports languages
other than English. Virtually any TV sold in
Europe since the 1990s
has support for this level. Around the year 2000 some station adopted
Level 2.5 teletext / Hi-Text, that allowed 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 the same underlying mechanism at the
transport layer. No TV sets currently implement the two most
Main article: Mullard SAA5050
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
The type of decoder circuitry is sometimes marked on televisions as
CCT (Computer-Controlled Teletext), or ECCT (Enhanced
Besides the hardware implementations, it's also possible to decode
teletext using a PC and video capture or DVB board.
Screenshot of an Electra teletext page.
Adoption in the United States was hampered due to a lack of a single
teletext standard and consumer resistance to the high initial price of
teletext decoders. Throughout the period of analogue broadcasting,
teletext or other similar technologies in the US were practically
non-existent, with the only technologies resembling such existing in
the country being closed captioning, TV Guide On Screen, and Extended
Data Services (XDS).
North American Broadcast
Main article: NABTS
NABTS was originally developed as a protocol by the Canadian
Department of Communications, with their industry partner Norpak, for
Telidon system. It was similar to the European World System
Teletext (WST, aka CCIR
Teletext System B), but differences between
the European and North American television standards and the greater
flexibility of the
Telidon standard led to the creation of a new
delivery mechanism that was tuned for speed.
First demonstrated in the United States in 1978,
NABTS was the
standard used for both CBS's
ExtraVision and NBC's very short-lived
Teletext services in the mid-1980s.
World System Teletext
Main article: World System Teletext
Station KSL in
Salt Lake City, Utah
Salt Lake City, Utah premiered a teletext service using
Ceefax. They were followed by television network CBS, which carried
out preliminary tests on both the British
Teletext and the rival
French Antiope system.
One of the most prominent providers was the Electra teletext service,
World System Teletext
World System Teletext (WST), broadcast from the early 1980s on
American cable channel WTBS. Electra also carried another teletext
service on its higher-numbered pages, a service called Tempo. Tempo
mainly carried sports (and other miscellaneous) information on its
pages. At the time of Electra's closing in 1993, it was the only
existing teletext service in the USA.
A few other services were offered by some large-market TV stations in
the US throughout the 1980s, such as Metrotext from
KTTV in Los
Angeles and KeyFax from
WFLD in Chicago. Despite this, the system
never caught on in the USA partly due to
EIA-608 being deployed for
Teletext was introduced and the higher cost of
Main article: Telidon
In the 1980s a similar system called
Telidon was developed in Canada
by the Department of Communications. It used a simple graphics
language that would allow a more complex circuit in the TV to decode
not only characters, but graphics as well. To do this, the graphic was
encoded as a series of instructions (graphics primitives) like
"polyline" which was represented as the characters PL followed by a
string of digits for the X and Y values of the points on the line.
This system was referred to as PDI (Picture Description Instructions).
Later improved versions of
Telidon were developed into NAPLPS.
Although there were numerous attempts to introduce
NAPLPS services in
North America, none of these was successful and eventually shut down.
A number of special-purpose systems lived on for some time, similar to
Prestel's lingering death, but the widespread rollout of internet
access in the 1990s ended these efforts.
Main article: List of
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.
Main article: Antiope (teletext)
In France, where 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 standard teletext in 1991.
BBC Micro's default graphics mode (mode 7) was based on
Teletext display, and 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
homecomputer's video logic was also based on a chip designed to
provide teletext services in TVs.
Main article: Prestel
Prestel was a British information-retrieval system based on teletext
protocols. However, it was essentially a different system, using a
modem and the phone system to transmit and receive the data,
comparable to systems such as France's Minitel. The modem was
asymmetric, with data sent at 75-bit/s, and received at 1200-bit/s.
This two-way nature allowed pages to be served on request, in contrast
to the TV-based systems' sequential rolling method. It also meant that
a limited number of extra services were available such as booking
event or train tickets and a limited amount of online banking.
Teletext information is broadcast in the vertical blanking interval
between image frames in a broadcast television signal, in numbered
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 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
VBI lines amongst 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 being entirely dependent in 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.
More sophisticated systems use a buffer memory to store some or all of
the teletext pages as they are broadcast, allowing instant display
from the buffer.
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.
PAL signal contains 625 lines of video data per screen,
broken into two "fields" containing half 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. CEPT1[clarification needed] hides the data
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; a unique pattern of bits allows the
decoder to identify which lines contain data. 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 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
−1.0 μs from the negative flank of the line synchronization
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 horizontal scan line.
Then first interlace frame will be sent, otherwise if vertical
synchronization let the full video line complete the second interlace
frame is sent.
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 digital 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 the bits used.
The commonly used standard B uses a fixed
PAL subtitling bandwidth of
8600 (7680 without page/packet header) bits/s per field for a maximum
of 32 characters per line per caption (maximum 3 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 the
horizontal positioning of a caption and to pad out the fixed packet.
The vertical caption position is determined by the packet address.
Teletext binary NRZ encodings
Bits per line
(per page row)
squared Sine wave
Symmetrical about 1/2 bit rate
Symmetrical about 1/2 bit rate
Raised cosine 100% roll-off
Controlled cosine roll-off of 0.6
100% cosine roll-off
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
analogue TV signal but concealed from view in the Vertical Blanking
Interval (VBI) television lines which do not carry picture
information. The teletext signal is digitally coded as 45-byte
packets, so the resulting rate is 7,175 bits per second per used lines
(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 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 a 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 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 television checks if the page in memory is
still up-to-date and updates it if necessary.
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 is
displayed in a block on the screen covering part of the television
The original standard provides a mono spaced 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 to allow for
improved appearance and the ability to individually select the color
of each character from a palette of 8. 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.
While the basic teletext format has remained unchanged in more than 30
years, a number of improvements and additions have been made.
Standard Electronic Programme Guides (EPG), like NexTView, are based
on teletext, using a compact binary format instead of preformatted
Various other kinds of information are sent over the teletext
protocol. For instance,
Programme Delivery Control
Programme Delivery Control signals—used by
video recorders for starting/stopping recording at the correct time
even during changes in programming—are sent as teletext packets. A
similar, but different, standard
Video Programming System
Video Programming System is also used
for this purpose.
Teletext pages may contain special packages allowing VCRs to interpret
their contents. This is used in relation to the
Video Programming by
Teletext (also known as startext) system which allows users to program
their videos for recording by simply selecting the program on a
teletext page with a listing of programs.
Other standards define how special teletext packets may contain
information about the name of the channel and the program currently
Video Program System
Video Program System
A closely related service is the
Video Program System
Video Program System (VPS),
introduced in Germany in 1985. Like teletext, this signal is also
broadcast in the vertical blanking interval. It consists only of 32
bits of data, primarily the date and time for which the broadcast of
the currently running TV programme was originally scheduled. Video
recorders can use this information (instead of a simple timer) in
order to automatically record a scheduled programme, even if the
broadcast time changes after the user programmes the VCR. VPS also
provides a PAUSE code; broadcasters can use it to mark interruptions
and pause the recorders, however advertisement-financed broadcasters
tend not to use it during their ad breaks. VPS (line 16) definition is
now included in the PDC standard from ETSI.
Some TV channels offer a service called interactive teletext to remedy
some of the shortcomings of standard teletext. To use interactive
teletext, the user calls a special telephone number with a regular
telephone. A computer then instructs the user to go to a certain
teletext page which has been assigned to the customer for that
session. Usually the page initially contains a menu with options and
the user chooses among the options using the buttons on the telephone.
When a choice has been made, the selected page is immediately
broadcast and can be viewed by the user. This is in contrast with
usual teletext where the customer has to wait for the selected page to
be broadcast, because the pages are broadcast sequentially. This
technology enables teletext to be used for games, chat, access to
databases etc. It allows one to overcome the limitations on the number
of available pages. On the other hand, only a limited number of users
can use the service at the same time, since one page is allocated per
user. Some channels solve this by taking into account where the user
is geographically calling from and by broadcasting different teletext
pages in different geographical regions. In that way, two different
users can be assigned the same page number at the same time as long as
they do not receive the TV signals from the same source. Another
drawback to the technology is the privacy concerns in that many users
can see what a user is doing because the interactive pages are
received by all viewers. Also, the user usually has to pay for the
telephone call to the TV station. For these reasons, these services
have since been superseded by the World Wide Web.
NRK digital teletext
With the advent of digital television some countries adopted the
misnomer "digital teletext" which, despite the previous teletext
standard's digital nature, uses an interpreted binary language, such
Multimedia Home Platform (MHP).
Others use the same teletext streams as before on DVB transmissions,
due to the
DVB-TXT and DVB-
VBI sub-standards. Those allow the
emulation of analogue teletext on digital TV platforms, directly on
the TV or set-top box, or via analog output, reproducing the vertical
blanking interval data in which
Teletext is carried.
Cessation of informational service
A number of broadcast authorities have recently ceased the
transmission of teletext services.
International broadcasters: A live teletext is also no longer
available on CNN International. Although many pages are still
available, they have not been updated since 31 October 2006.
United Kingdom: the founder of the world's first teletext service, the
BBC which closed its
Ceefax service in 2012 when Britain adopted a
fully digital television broadcast system. Elsewhere in the country
the full service is no longer carried on any digital television
services, although many channels on Sky still broadcast teletext
subtitles and may still have a small number of active pages.
Teletext ended in each region after analogue broadcasts finished. See
Digital switchover dates in the United Kingdom.
Seven Network shut down the
Austext service on 30
September 2009. They claimed that the technology has come to the end
of its useful service life and is not commercially viable to replace.
TVNZ Access Services announced the discontinuation of the
service on April 2, 2013. A claim about equipment failures and that
web sites have been used instead has been given as the reason.
MediaCorp announced that they will discontinue its
eponymously titled service Teletext, with effect from 30 September
(Subtitling still continues to use
Teletext in these three countries
with some providers switching to using image based DVB subtitling for
New Zealand solely uses DVB subtitling on terrestrial
Teletext still being used on internal SDI
List of teletext services
Digital terrestrial television
Digitiser – video games magazine
Electronic program guide
Electronic program guide (EPG)
Multimedia Home Platform (MHP) – open middleware system standard
designed by the DVB project
NAPLPS – graphics language
NABTS – protocol used for encoding NAPLPS-encoded teletext pages
Park Avenue – teletext based soap opera
Programme Delivery Control
Programme Delivery Control (PDC) – indicating when transmission of a
programme starts and finishes
SubRip – optical character recognition of subtitles superimposed on
video (or in DVDs)
Text semigraphics – primitive form of raster graphics
Videotex – interactive service using teletext graphics
Radio Data System
Radio Data System (RDS) – 1 kbit/s data transmission over FM
This article needs additional citations for verification. Please help
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Look up teletext in Wiktionary, the free dictionary.
Teletext Specification, September 1976 (HTML)
Teletext Specification, September 1976 (scanned copy of
original document, MS-Word and Postscript files)
Teletext specification ETS 300 706 (ETSI, 1997); Version
1.2.1, April 2003
History of Teletext
History of Ceefax
Teletext Trial (1980) sample screens
Teletext online – Spain and South America
Teletext in Sweden & Norway
Teletext Then and Now
Teletext Then and Now Gallery – pictures of teletext services in the
UK, Ireland and around the world
Timeline of Telecommunications, with some entries on teletext
The page for the now-defunct Star Sight service
A page on teletext in the USA
Teletext Decoder Certification
Finnish Yle Teletext
Broadcast video formats
System L (SECAM-L)
MPEG-4 AVC standards
MPEG-1 Audio Layer II
Digital cinema (DCI)
Display motion blur
Moving image formats
MPEG transport stream
Reverse Standards Conversion
Video on demand
Templates (Analogue TV Topics)