| 摘要 |
Apparatus for reproducing from a record disc a run length limited PCM audio signal comprises an optical transducer which reproduces the PCM audio signal from the record disc; a waveform shaping circuit for producing an output signal corresponding to the reproduced PCM audio signal and having portions of opposite polarities so that the output signal includes a plurality of transition intervals; a clock pulse generator for generating clock pulses having a constant frequency higher than the bit frequency of the output signal; a counter for detecting the period of each transition interval of the output signal by counting the number of clock pulses generated during each detected transition interval of the output signal; a NAND gate for determining, during each of at least one predetermined period selected to be longer than the period <IMAGE> if the number of the clock pulses counted by the counter during each detected transition interval in each longer predetermined period corresponds to a predetermined number of clock pulses included in the maximum transition interval which occurs when the record disc is rotating at a predetermined constant linear velocity, and for producing a velocity control signal in response thereto; and a drive circuit for controlling rotation of the record disc at the predetermined constant linear velocity in response to the velocity control signal.
|
