Teletext 电视资讯

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 to a 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. The first test transmissions were made by the BBC in 1973, known as Ceefax ("see facts"). After adoption in the UK the standards became international as the European Teletext standards and as the 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. The decline of teletext has been hastened by the introduction of digital television, though an aspect of teletext continues in closed captioning.