SERVO SYSTEM FOR VIDEO RECORDER

摘要

A video recorder has multiple rotating heads, the speed and phase of rotation of which must be accurately synchronized with the transmitted video signal or with a prerecorded control signal. This is accomplished by means of a servo which utilizes two fixedly positioned pick-up devices adjacent the rotating heads for detecting the passing of certain fixed points on a disk carrying the heads. The period of time for a point to pass between two detectors is compared with the reference to control the speed of the driving motor. The phase of the driving motor is controlled by developing a positional error signal as a result of any difference in time between the detection of a given point on the disk with the occurrence of either the video sync or a prerecorded control signal. Means are also provided for assuring the proper sequence of operation of the heads.