Capacitance Electronic Disc

CEDs are conductive vinyl platters that are 30.0 cm (11.8 in) in diameter. To avoid using the metric system to name their discs, they were called "12 inch discs" even though they were actually slightly smaller. Each side of the disc has grooves that are about 19 miles long and are 37 times smaller than the grooves on a regular phonograph record. When the disc is playing, it spins at about 450 times per minute and each rotation of the disc contained several frames of audio and visual information. To read the disc, a titanium needle was placed very lightly on the outer edge of the disc. A small electric current was then passed thru the center of the needle, where it would touch the bottom of the groove and read the audio information, which was stored in small holes. The needle would read these by detecting how much air was between the needle and the pit and then the electronics of the player would convert these into audio. The visual information was stored in the grooves and were read like a regular phonograph record. As the needle passed over the grooves, it would vibrate and the player would convert the vibrations into the pictures.