Baird Phonovision disc, c 1928.

One of only six Phonovision discs known to exist, representing the first time television pictures were recorded. Phonovision discs contain the original experimental television recordings of John Logie Baird (1888-1946), recorded from 1927-1928, les than two years after his first demonstration of television. With only 30 lines per picture (per television frame), the highest frequency present was low enough to be audible - the video signal could therefore be recorded as an audio signal onto disc.