Videodiscs for home TV sets

Press, Volume CX, Issue 32460, 21 November 1970, Page 13

Videodiscs for home TV sets

A new invention lets you watch a television programme of. your own choice at your own time. You can buy it on something like an ordinary long-playing disc, and play it on a relatively inexpensive machine, coupled to your own television set. This is the latest development from Teldec, a research organisation jointly owned by Germany’s Telefunken electronics firm and British Decca whose interests cover gramophone records to navigationradar. A If you know how a gramophone record works you may think this sort of television recording is impossible. Even . ordinary stereo music uses up something near the full potential of disc-recording techniques. A television pictures requires about 250 times more “information,” so an ordinary long playing record would not have the capacity. The solution lies in a completely new principle in playing the Videodisc, as Richard Oliver outlined in a 8.8. C. science broadcast. On a stereo long playing record, the stylus rests in the grooves and is moved from side to

side and up and down by. "wiggles” in the grooves. If the grooves were made finer to give more capacity they could not accept a reasonably cheap stylus. But on a Videodisc, picture and sound are recorded as a vertical movement of the groove, a “hill and dale” effect. And instead of the stylus following this 1 complete up and down movement it touches only the tops of the “hills.” The disc is made of soft but springy plastic, so the hill-tops bend over under the stylus and spring back upright as they emerge again. Each hill-top spring back sends a little shock wave up the stylus, to be coverted into and electronic signal for the television set. Videodiscs are thinner than music records but otherwise appear very similar and will sell at much the same prices. At present they play for about five minutes, but Teldec hopes to market a 12minute disc within two years. The players, which incorporate an autochange mechanism, are expected to cost about 60 for black-and-white television, and £l2O for colour. And, of course, you need a television set too.