07.7

//Source(s): "Video on disc" By Tim Frost, http://prostudio.com/issues/viddisc.html// The TeD Video Disc was an 8" disc system produced by a collaboration between Telefunken, Teldec and Decca. The TeD disc was very much like old vinyl records, but with nearly 300 groves per mm. It ran at 1500 rpm. The FM modulated video and audio was picked up by a stylus system in much the same way as an LP, but it never really made it into the commercial world. By the start of the 1980s, no less than three entirely different video disc formats were being actively touted on both sides of the Atlantic. Philips had launched LaserVision, which had been seen and discussed as early as 1972, and was the first of four different Philips video disc formats. RCA was going strong with CED, and JVC brought up the rear with VHD/AHD. Several other companies were working on video disc formats. Some like TEAC, who produced a workable laser record/write system, kept the systems purely for industrial users, keeping themselves out of the major hustles of the domestic market. On the consumer side each of the systems had their own supporters, although as far as the consumer was concerned, there was little difference in quality or functionality. The RCA CED or SelectaVision Videodisc was the most high profile of the three systems. CED stood for Capacitance Electronic Disc. The information was recorded using FM techniques creating pits and bumps on the disc surface. On playback, a small diamond stylus attached to an electrode ran over the disc as it rotated. As the electrode rose and fell, the capacitance between the electrode and the carbon loaded PVC of the disc's surface varied. This was decoded into video and audio signals. Technical quality was up to VHS levels at least, and CED offered stereo sound. It also had good initial support with pre-recorded material. When the whole system came to grinding halt in 1984, there were a good 250 titles available. The discs played an hour each side, so that a full movie could be placed on a single disc. The technology for the JVC VHD/AHD system was a half- way house between CED and LaserDisc as we know it. The disk itself resembled a LaserDisc, with the data carrier imbedded beneath a clear flat plastic surface. The video and audio information was recorded more or less in the same way as CED, using an electrode in the player to sense different capacitances created by micropits in the substrate. Each disk side offered an hour of playing time with full colour and stereo sound. An audio-only version of the 10" disc held up to three channels of PCM encoded audio. Thorn/EMI entered a joint venture with JVC to press the VHD/AHD discs. Philips LaserVision was the progenitor of the current LaserDisc. From the start it was a 'silver disc' 12" in diameter, with pits recorded into it and read by a laser, using Philips CD technology. Offering an hour of play, stereo sound, and random access to any part of the disc, in practical terms it offered everything that LaserDisc and Video CD could offer, but a whole decade earlier. In a re-launch of the system, Philips and Sony introduced CD Video. This introduced the 5" CD, carrying 20 minutes of audio and 6 minutes of video. It was intended to capture a CD/Video singles market- another forlorn hope. But CD Video did accomplish the merging of CD and LaserVision, so a single 'combi-player' could play both. It also marked the end of LaserVision and the beginning of LaserDisc. In the US this meant only a formal name change, but in Europe the LaserDisc was redesigned to carry digital sound. The new LaserDiscs would not play on the old analog FM sound LaserVision players. After a pause in production, European LaserDiscs were re-launched, with growing success.
 * From: kadrey@well.com (Richard Kadrey)**