| 摘要 |
PURPOSE:To discriminate immediately a pseudo stable point independently of the tracking phase and to bring the circuit to a stable point when the circuit falls into the pseudo stable position by allowing a filter means extracting a modulation output outputted at the pseudo stable point to control the relative phase of sequence after the modulation output is obtained. CONSTITUTION:If a head A or B falls into a pseudo stable point, a signal in frequency 4fH and 2fH is obtaind as a modulation output of a pilot signal P from a main track. A band pass filter BPF30 extracts either modulation output according to the set center frequency. After the extracted output is aplied with level detection by a level detector 31, the result is subject to waveform shaping by a Schmitt trigger circuit 32 and fed to a sequence conversion circuit 33. The said sequence converting circuit 33 outputs a reference signal R with the same sequence as that of a reproduced pilot signal and has a function changing the sequency of f1-f2-f3-f4- by 180 deg. when the waveform shaping output reaches a prescribed level or over. Thus, even if the head A or B falls in the pseudo stable point, both the sequences are synchronized immediately.
|
