| 摘要 |
PURPOSE:To detect the rotating condition of a rotary recording body with simple constitution, by counting the cycle of a timing signal and generating a signal indicating that servo lock is established when a phenomenon that the counted value remains in a prescribed range occurs prescribed times. CONSTITUTION:A magnetic head 26 is positioned onto a track by means of a step motor 30 and detects video signals and a control device 60 detects PG signals from a phase generator 22 produced at every one vertical scanning period. On the other hand, the control device 60 counts reference clocks from a reference generator 62 and decides whether or not the interval of the PG signals is equal to the one vertical scanning period. When it is detected that the interval is equal for prescribed times, the device 60 generates a servo lock signal. Therefore, the rotating condition of a disk 10 is detected with simple constituion.
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