Television Electronic Disc
History
Initially known as, "The Video Disc" or the Teldec Television Disc, TeD (Television Electronic Disc) was first announced at a press conference in Berlin on June 24, 1970. It was developed by a team from two German companies: AEG-Telefunken and Teldec. Program information was stored in the form of ridges in the surface of a thin, flexible foil disc, which was claimed to be sufficiently robust to withstand being played 1,000 times. The main technological breakthrough was the vertical recording method that reduced the track pitch to 0.007 mm, and increased the rotation speed to 1,500 rpm, making it possible to record 130–150 grooves per millimeter, compared with the typical 10–13 grooves on an audio disc. This increased the available bandwidth from around 15 kHz to 3 MHz. The tracks were read by a pressure pick-up, which translated the surface of the ridges, via a piezo-electric crystal, into an electrical signal.
Television Electronic Disc-2