| 摘要 |
PURPOSE:To make the disturbance of time base control attended by a track jump the minimum, by resetting a reference signal immediately after the track jump and making the lock drawing-in time of a reproduced horizontal synchronizing signal to the reference signal extremely shorter. CONSTITUTION:The output (h) of a phase changing means R-SFF 24 is inputted to a monostable multivibrator 25, whose semi-stable period is a half of a horizontal scanning period H and the trailing of the output (i) of the multivibrator 25 is detected by a detecting circuit 26. The detecting output (j) of the circuit 26 resets another phase changing means R-SFF 23 and the output (k) of the means R-SFF 23 clears a reference signal producing counter 5. Therefore, no reference signal is outputted while the output (k) is high in level. Since the counter 5 outputs a reference horizontal synchronizing signal at the sane time when it is cleared, the counter 5 continues counting and outputs the reference horizontal synchronizing signal at every fixed count. Therefore, the period, during which a motor error signal (c) and tangential error signal (f) are disturbed, after a track jump is short and, when the disturbance is short to such degree, the disturbance of time base control hardly occurs.
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