ABSTRACT
In contrast to turntable rotational speed, this is a measure of the linear velocity of the record surface as it moves beneath the pickup stylus with an LP recording or laser beam with a digital-disc recording. With the LP record, although the angular, rotational velocity remains constant, the linear velocity will obviously decrease as the groove diameter becomes smaller toward the center of the record. This reduction in linear speed can seriously compromise sound quality in the inner-groove area, even if the record/playback system is designed to compensate for the change in linear speed. It was this factor that influenced Thomas Edison to hold to the cylinder record, where surface speed would be constant. Charles Tainter applied for a patent on a device that maintained uniform surface speed on discs in 1887, but he did not follow it with commercial production. Discs issued in the U.K. in 1922-1924, by the World Record Co., did play at constant linear speed. This was achieved by a record controller device, one that was made available for standard Gramophones by Noel Pemberton Billing. Modern digital-disc playback systems of all kinds utilize a variable rotational speed, in order to keep the linear speed constant. (British patents #195,673 and 204,728).
