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 ℔.
NAPLPS 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 Corporation. The basics of NAPLPS were later used as the basis for several other microcomputer-based graphics systems.
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.
A telephone keypad is a keypad installed on a push-button telephone or similar telecommunication device for dialing a telephone number. It was standardized when the dual-tone multi-frequency signaling (DTMF) system was developed in the Bell System in the United States in the 1960s – this replaced rotary dialing, that had been developed for electromechanical telephone switching systems. Because of the abundance of rotary dial equipment still on use well into the 1990s, many telephone keypads were also designed to be backwards-compatible: as well as producing DTMF pulses, they could optionally be switched to produce loop-disconnect pulses electronically.
Prestel was the brand name of a videotex service launched in the UK in 1979 by Post Office Telecommunications, a division of the British Post Office. It had around 90,000 subscribers at its peak, and was a forerunner of the internet-based online services developed in the late 20th and early 21st centuries. Prestel was discontinued in 1994.
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.
NABTS, the North American Broadcast Teletext Specification, is a protocol used for encoding NAPLPS-encoded teletext pages, as well as other types of digital data, within the vertical blanking interval (VBI) of an analog video signal. It is standardized under standard EIA-516, and has a rate of 15.6 kbit/s per line of video. It was adopted into the international standard CCIR 653 of 1986 as CCIR Teletext System C.
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 particular position in a table, where the position has been assigned a meaning. The table may be one dimensional, two dimensional, three dimensional, etc... in any number of dimensions.
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. 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. It contains various common symbols which are related to and used in the various technical, programming language, and academic professions. For example:
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, commonly referred to as a 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.
Text-based semigraphics, pseudographics, or character graphics 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.
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.
