First demo-ed in 1964 (see mafioso's thread on cartridge weight , steerpike take for the rCS product). Quote from Wikipedia:
"CEDs are conductive vinyl platters that are 30.0 cm (11.8 in) in diameter. To avoid metric names they are usually called "12 inch discs". A CED has a spiral groove on both sides. The groove is 657 nm wide and has a length of up to 12 miles (19 km). The discs rotate at a constant speed during playback (450 rpm for NTSC, 500 rpm for PAL) and each rotation contains several full frames (four frames for NTSC, three for PAL). A keel-shaped needle with a titanium electrode layer rides in the groove with extremely light tracking force (65 mg), and an electronic circuit is formed through the disc and stylus. Like a turn table, the stylus reads the disc, going towards the center. The video and audio signals are stored on the Videodiscs in a composite analog signal which is encoded into vertical undulations in the bottom of the groove, somewhat like pits. These undulations have a shorter wavelength than the length of the stylus tip in the groove, and the stylus rides over them; the varying amount of air pressure between the stylus tip and the undulations in the groove under it directly controls the capacitance between the stylus and the conductive carbon-loaded PVC disc. This varying capacitance in turn alters the frequency of a resonant circuit, producing an FM electrical signal which is then decoded into video and audio signals by the player's electronics."
Holy cow, there's always something new to learn!
"CEDs are conductive vinyl platters that are 30.0 cm (11.8 in) in diameter. To avoid metric names they are usually called "12 inch discs". A CED has a spiral groove on both sides. The groove is 657 nm wide and has a length of up to 12 miles (19 km). The discs rotate at a constant speed during playback (450 rpm for NTSC, 500 rpm for PAL) and each rotation contains several full frames (four frames for NTSC, three for PAL). A keel-shaped needle with a titanium electrode layer rides in the groove with extremely light tracking force (65 mg), and an electronic circuit is formed through the disc and stylus. Like a turn table, the stylus reads the disc, going towards the center. The video and audio signals are stored on the Videodiscs in a composite analog signal which is encoded into vertical undulations in the bottom of the groove, somewhat like pits. These undulations have a shorter wavelength than the length of the stylus tip in the groove, and the stylus rides over them; the varying amount of air pressure between the stylus tip and the undulations in the groove under it directly controls the capacitance between the stylus and the conductive carbon-loaded PVC disc. This varying capacitance in turn alters the frequency of a resonant circuit, producing an FM electrical signal which is then decoded into video and audio signals by the player's electronics."
Holy cow, there's always something new to learn!
