- published: 28 Nov 2012
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Ceefax (phonetic for "See Facts") is the BBC's teletext information service transmitted via the analogue signal, started in 1974. It still runs regularly filling BBC2's overnight schedule as Pages from Ceefax, while the interactive service will run until 24 October 2012, in line with the digital switchover.
During the late 1960s, engineer Geoff Larkby and technician Barry Pyatt were working at the Designs Department (Television Group) of the BBC on a text transmission system. Its object was to transmit a printable page of text during the nocturnal "close-down" period of normal television transmission. Sir Hugh Carleton Green, then Director General of the BBC, was interested in making farming and stock-market prices available as hard copy via the dormant TV transmitters. The remit received by BBC Designs Department was "the equivalent of one page of The Times newspaper to be transmitted during shut-down".
The first system employed a modified Muirhead drum facsimile transmitter, and hard-copy printer using pressure-sensitive "till-roll" paper passing over a drum with a raised helix of steel wire. This drum was synchronised with the transmission drum by means of the "frame" pulse inherent in the Muirhead system. Printing was effected by a hardened steel blade driven initially by loudspeaker moving coil, then by a printed-circuit coil, and finally by a special ceramic piezo element from Brush-Clevite. The combination of rotating helix and linearly moving blade, with the moving till-roll between them, enabled a raster to be drawn on the paper, without the smoke and smell of the Muirhead "sparking" system.