| 摘要 |
<p>PURPOSE:To execute a stable tracking control by deciding a real synchronizing signal or not in accordance with the number of synchronizing signals which are detected within a prescribed period, and controlling the hold of a pilot signal, in an area division automatic track follow-up (ATF) controller. CONSTITUTION:When a synchronizing signal recorded together with a pilot signal for an ATF is detected by a BPF12 and a comparator 13, a pulse is outputted from a synchronizing pattern detecting circuit. It is applied to an SPL forming circuit 21, and also, supplied to a synchronizing signal counter 17. Unless the counting value of this counter 17 reaches a set threshold level, it is not decided to be the real synchronizing signal by a comparator 18, the circuit 21 is reset, and the hold of the pilot signal detected by an envelope detector 3 through a switching circuit 5 is not executed. Accordingly, the pilot signal is not held by a synchronizing signal detected erroneously, and the tracking control can be executed stably and exactly.</p> |
