TURNTABLE

in sound reproduction, rotating platform that carries a phonograph record. Turntables commonly revolve at 16 2/3, 33 1/3, 45, or 78 revolutions per minute; many record players have gearing that allows the user to choose among these speeds. For best sound reproduction, constant turning speed is crucial; transcription turntables used by radio stations are weighted to minimize speed variations and are driven by synchronous motors. Though several different types of driving mechanism were tried in early phonographs, the electric motor, cushion-mounted to minimize vibration, became the most widely employed.