Capacitance Electronic Disc (CED) was an analogue video disc playback system developed by RCA, using a special stylus and high-density groove system similar to phonograph records. The name ‘SelectaVision’ was RCA’s brand name for the CED system. It was also used for some early RCA brand VCRs.
The 12-inch discs were crafted using PVC blended with carbon to allow the disc to be conductive, and a thin layer of silicone was applied to the disc as a lubricant. Discs were stored in a caddy from which the disc was extracted by the player. CEDs could store 60 minutes of video per side, so almost all films needed to be flipped over at some point.
A stylus with a titanium electrode layer rides in the grooves with extremely light tracking force (65 mg), and an electronic circuit is formed. The video and audio signals are encoded into vertical undulations in the bottom of the groove, that the stylus rides over; the varying amount of air pressure between the stylus tip and the undulations under it controls the capacitance between the stylus and disc. This varying capacitance is then decoded into video and audio signals by the player’s electronics.
CED players, because they have fewer precision parts than a VCR, cost about half as much to manufacture. The discs themselves could be inexpensively duplicated, stamped out on slightly-modified audio gramophone record presses. Since CEDs were a disc-based system, they did not require rewinding. Early discs were generally monaural, but later discs included stereo sound. Monaural CED disks were packaged in white protective caddies while stereo disks were packaged in blue protective caddies.
RCA estimated that the number of times a CED could be played back, under ideal conditions, was 500. Since the CED system used a stylus to read the discs, it was necessary to regularly change the stylus in the player to avoid damage to the disc. When a disc began to wear, video and audio quality would severely decline.
First conceived in 1964, by which time it was released in 1981 it was already outmoded by LaserDisc, and the emerging Betamax and VHS videocassette formats. Sales for the system were nowhere near projected estimates (although the discs themselves sold well), and in 1984, player production ended, with discs ending production in 1986. Over 270 titles were released in the UK.
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