What Is Videotex?

Videotex is an interactive electronic information system that delivers alphanumeric and low-resolution graphic content to a user's display terminal through a two-way data communication channel, typically the public switched telephone network or a cable infrastructure. Users navigate hierarchical menus or submit queries to a central host computer, which returns pages of text and simple graphics formatted to fit the display capabilities of a television set or dedicated terminal. Videotex was developed independently in several countries during the 1970s, with the British Post Office's Prestel service, launched experimentally in 1976, and France Télécom's Minitel, introduced nationally in 1982, representing the two most technically and commercially significant deployments.

The technology occupies a historical position as one of the first mass-market online information services, predating the Internet's public adoption by roughly two decades. Its architectural pattern, in which a central database responds to terminal queries over a switched network, anticipated many characteristics of Web-based information retrieval.

Data Communication Architecture

Videotex systems communicate over standard telephone circuits using modems operating at rates between 1,200 and 9,600 bits per second, which was adequate for text and simple graphics but limited image complexity. The host computer stores a database of numbered pages, each containing a screenful of content; user terminals send page requests as short data packets and display received pages locally. The CCITT, predecessor to the ITU-T, defined the T.100 and T.101 recommendations that specified data formats and terminal profiles to allow interoperability across national videotex systems. These ITU recommendations also addressed the representation of characters from multiple language scripts, an important requirement for France's Minitel service, which operated until 2012 and carried some 25,000 services including banking, ticketing, and online directories. The ITU-R BT.653 teletext systems recommendation documents the related broadcast-side standard that governed how both teletext and videotex-linked services were identified and routed.

Teletext

Teletext is a closely related but technically distinct system that uses the vertical blanking interval (VBI) of an analog broadcast television signal to carry digital pages of text and graphics. Unlike videotex, teletext is one-way: the broadcaster cyclically transmits all available pages, and the user's decoder captures the requested page as it arrives in the cycle. The BBC's Ceefax service, launched in 1974, was the first operational teletext service; it reached millions of UK households and continued operating until the analog television switchoff in 2012. The World System Teletext standard, published as ITU-R BT.653, defined the transmission format for 625-line television systems. A historical overview of the teletext and videotex era documents how both systems competed with and complemented each other during the 1980s and 1990s, with teletext favored for broadcast news and weather while videotex handled transactional services requiring interactivity.

Decline and Legacy

Videotex adoption peaked in the late 1980s and declined through the 1990s as Internet access and the World Wide Web provided a superior platform for the same information services without the constraints of proprietary page formats or dedicated terminal hardware. The Sage Encyclopedia of Journalism's entry on videotex and teletext characterizes the transition as a shift from closed, operator-controlled information networks to open, user-published hypertext. Teletext survived longer in broadcast contexts because its delivery mechanism required no user hardware upgrade beyond a television with a built-in decoder.

Applications

Videotex had applications in several sectors during its active period, including:

• Electronic directory services replacing printed telephone directories
• Home banking and financial account inquiry
• Rail, airline, and event ticketing and reservation
• News, weather, and public information bulletin boards
• Remote database access for business and professional users