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Philips-MCA has taken a different approach. Its aluminum-coated, plastic record, stamped from a master disc that has been etched by a laser beam, is covered with billions of microscopic pits. Variations in pit size encode the video and sound messages. For playback, a sharply focused beam from a low-power (one-thousandth of a watt) helium-neon laser scans the disc as it whirls around at 1,800 r.p.m. The laser beam flickers as it is reflected from the record's pocked surface, and the flickering is detected by a photosensitive cell, like that used in photographic exposure meters, which in turn converts it into electrical impulses that are changed into image and sound.
With its simpler turntable, RCA hopes to keep costs down to $400 for its player, v. a projected price of $500 for the Philips-MCA machine. Moreover, the RCA records will be usable on both sides for a full hour's playing time, whereas the Philips-MCA disc plays on only one. On the other hand, the Philips-MCA system needs no stylus; its disc, scanned only by light, should have an indefinite lifetime. RCA's stylus wears as it makes contact with the discs and must be replaced every 300 hours (estimated cartridge cost: $10); the discs also wear out after some 300 plays.
Philips-MCA's laser system has an added attraction. By letting the laser beam circle over the same portion of track, the player can freeze a single frame (it takes one revolution to make one picture). It can also run the images in slow motion and even go backward with only the push of a button—all potentially valuable features for educational programs. Each competitor is convinced that its approach is superior. But about one point there is no disagreement: either system could signal a major change in home entertainment habits.
* A ten-minute disc system is already being sold in Europe by Teldec, a joint venture of West Germany's Telefunken and Britain's Decca companies. There are no plans to sell it in the U.S.