Today in 1971, the BBC filed for a patent on "The Transmission of Alphanumeric Data by Television."
The world's first teletext system, it was first publicly demonstrated on January 4, 1973. Originally conceived as a system for transmitting printable pages of text via dormant TV transmitters at night, the (renamed) CEEFAX system went live on September 23, 1974, with thirty pages of information.
CEEFAX was shut down on October 23, 2012, when the U.K. digital switchover was completed in Northern Ireland.