| 摘要 |
When a photoelectric detector in a record player is moved under the control of a signal supplied by a control circuitry in order to detect a required unmodulated space on a surface of a record disk to be played, a pickup arm is moved according to an output of a servo-amplifier so as to assume a position with respect to the record disk corresponding to a position assumed by the photoelectric detector. The servo-amplifier is inputted with two voltages related to the positions of the pickup arm and the photoelectric detector both relative to the record disk. After a required unmodulated space is detected, the pickup arm is switched over to be controlled of its movement in accordance with a signal delivered from the control circuitry, and will trace the record groove of the disk, while the movement of the photoelectric detector is controlled by an output of the servo-amplifier. Switching over from a former control mode to latter is carried out by the control circuitry in response to the output of the photoelectric detector.
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