| 摘要 |
In an apparatus for reproducing, from a record disc, audio information recorded in the form of a pulse code modulation (PCM) in a run length limited code, a reproduced signal derived from the rotated record disc, for example, by a pick-up in the form of photo detector in the case of optical recording and reproducing, is compared with a first reference level or signal to provide an output signal corresponding to the reproduced signal and having portions of opposite polarities, the interval between transitions from one to the other of the opposite polarity portions of the output signal is detected for providing a corresponding detecting signal, a velocity servo circuit compares the detecting signal with a second reference signal which corresponds, for example, to a maximum transition interval when the record disc is driven at a predetermined linear velocity at the location scanned by the pick-up, so as to produce a corresponding velocity control signal for maintaining the record medium at such predetermined linear velocity, a first time constant circuit is included in the velocity servo circuit for determining the rate of response thereof to any deviation from the predetermined linear velocity, a phase servo circuit has a phase locked loop for producing a phase signal from the reproduced signal which is compared with a reference phase signal so as to produce a corresponding phase control signal for maintaining a predetermined phase of the reproduced signal when the record disc is driven at the predetermined linear velocity, and a second time constant circuit is included in the phase servo circuit for determining the rate of response thereof to any deviation from the predetermined phase and has a time constant smaller than that of the first time constant circuit so that the phase control signal can be composed with the velocity control signal for simultaneously influencing the drive of the record disc. |
