Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. DTMF was first developed in the Bell System in the United States, and became known under the trademark Touch-Tone for use in push-button telephones supplied to telephone customers, starting in 1963. DTMF is standardized as ITU-T Recommendation Q.23. It is also known in the UK as MF4.
The symbol # is known variously in English-speaking regions as the number sign, hash, or pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare ℔.
Telidon was a videotex/teletext service developed by the Canadian Communications Research Centre (CRC) during the late 1970s and supported by commercial enterprises led by Infomart in the early 1980s. Most work on the system ended after 1985, having failed to build critical mass.
Videotex was one of the earliest implementations of an end-user information system. From the late 1970s to early 2010s, it was used to deliver information to a user in computer-like format, typically to be displayed on a television or a dumb terminal.
ISO/IEC 646 is a set of ISO/IEC standards, described as Information technology — ISO 7-bit coded character set for information interchange and developed in cooperation with ASCII at least since 1964. Since its first edition in 1967 it has specified a 7-bit character code from which several national standards are derived.
The Minitel was a videotex online service accessible through telephone lines, and was the world's most successful online service prior to the World Wide Web. It was invented in Cesson-Sévigné, near Rennes, Brittany, France.
Prestel, the brand name for the UK Post Office Telecommunications's Viewdata technology, was an interactive videotex system developed during the late 1970s and commercially launched in 1979. It achieved a maximum of 90,000 subscribers in the UK and was eventually sold by BT in 1994.
E.123 is an international standard by the standardization union (ITU-T), entitled Notation for national and international telephone numbers, e-mail addresses and web addresses. It provides guidelines for the presentation of telephone numbers, email addresses, and web addresses in print, on letterheads, and similar purposes.
Antiope was a French teletext standard in the 1980s. It also formed the basis for the display standard used in the French videotex service Minitel. The term allegedly stood for Acquisition Numérique et Télévisualisation d’Images Organisées en Pages d’Écriture, which could be loosely translated as Digital Acquisition and Remote Visualization of Images Organized into Written Pages.
ITU-T recommendation T.50 specifies the International Reference Alphabet (IRA), formerly International Alphabet No. 5 (IA5), a character encoding. ASCII is the U.S. variant of that character set.
Teletext, or broadcast teletext, 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, 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.
A code point, codepoint or code position is a unique position in a quantized n-dimensional space that has been assigned a semantic meaning.
T.51 / ISO/IEC 6937:2001, Information technology — Coded graphic character set for text communication — Latin alphabet, is a multibyte extension of ASCII, or more precisely ISO/IEC 646-IRV. It was developed in common with ITU-T for telematic services under the name of T.51, and first became an ISO standard in 1983. Certain byte codes are used as lead bytes for letters with diacritics (accents). The value of the lead byte often indicates which diacritic that the letter has, and the follow byte then has the ASCII-value for the letter that the diacritic is on.
Miscellaneous Technical is a Unicode block ranging from U+2300 to U+23FF, which contains various common symbols which are related to and used in the various technical, programming language, and academic professions. For example:
Unicode input is the insertion of a specific Unicode character on a computer by a user; it is a common way to input characters not directly supported by a physical keyboard. Unicode characters can be produced either by selecting them from a display or by typing a certain sequence of keys on a physical keyboard. In addition, a character produced by one of these methods in one web page or document can be copied into another. In contrast to ASCII's 96 element character set, Unicode encodes hundreds of thousands of graphemes (characters) from almost all of the world's written languages and many other signs and symbols besides.
E.161 is an ITU-T Recommendation that defines the arrangement of digits, letters, and symbols on telephone keypads and rotary dials. It also defines the recommended mapping between the basic Latin alphabet and digits. Uses for this mapping include:
A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by modulating one or more carrier wave signals to encode digital information, while the receiver demodulates the signal to recreate the original digital information. The goal is to produce a signal that can be transmitted easily and decoded reliably. Modems can be used with almost any means of transmitting analog signals, from light-emitting diodes to radio.
The Mullard SAA5050 was a character generator chip for implementing the Teletext character set.
ISO 2047 is a standard for graphical representation of the control characters for debugging purposes, such as may be found in the character generator of a computer terminal; it also establishes a two-letter abbreviation of each control character. The graphics and two-letter codes are essentially unchanged from the 1968 European standard ECMA-17 and the 1973 American standard ANSI X3.32-1973. It became an ISO standard in 1975. It is also standardized as GB/T 3911-1983 in China, as KS X 1010 in Korea, and was enacted in Japan as "graphical representation of information exchange capabilities for character" JIS X 0209:1976.
This article covers technical details of the character encoding system defined by ETS 300 706 of the ETSI, a standard for World System Teletext, and used for the Viewdata and Teletext variants of Videotex in Europe.
