Ceefax

Ceefax () was the world's first teletext information service and a forerunner to the current BBC Red Button service. Ceefax was started by the BBC in 1974 and ended at 23:32:19 BST (11:32:19 p.m.) on 23 October 2012 after 38 years of broadcasting, in line with the digital switchover completion in Northern Ireland. To receive a desired page of text on a teletext-capable receiver, the user entered a three-digit page number on the device. The selected page was displayed on the user's screen as it was transmitted, requiring a wait of several seconds. There were many pages to choose from, and they could be displayed either on a black background or superimposed over the broadcast programme picture. This latter feature made it technically possible for the first time for British broadcasters to transmit subtitles that could be turned on or off by the viewer, rather than as part of the broadcast image.