| 摘要 |
<p>A servo system for use with apparatus for reproducing a disc on which PCM signals have been modulated by a run length limited code and which are recorded at a constant linear velocity. The servo circuit detects the length of a period during which a playback signal is inverted and produces an output corresponding to the detected length. The servo circuit has a peak value hold circuit (8) for maintaining a peak value of the output and a bottom value hold circuit (12) downstream of a peak value hold circuit (8) which has a time constant which is larger than the charging time constant of the peak value hold circuit (8) so as to produce an output which follows the output of the peak value hold circuit (12) with a reference value (Es) so as to produce a signal for controlling a disc drive motor (10) such that a maximum or minimum length during which the playback signal is inverted equals the length when the linear velocity is a reference value so that the linear velocity will be maintained constant during playback.</p> |
