Television Electronic Disc
From Just Solve the File Format Problem
The Television Electronic Disc (TeD) was an early variety of videodisc. Unlike other videodisc varieties, it was not read optically by a laser, but actually used grooves, similar in theory to those of a gramophone record, though these were much narrower and tighter than record grooves, and read at a much faster rotation speed (1500 RPM). They were read using a pressure pick-up which used a piezo-electric crystal to translate the grooves to an electric signal. 8 and 12 inch discs were used; in the original design 8-inch discs held only 5 minutes of video and 12-inch discs 7 1/2 minutes, but this was doubled by the time the format was actually released. This still required multiple discs even for a TV episode, let alone a feature film.
