| 摘要 |
PURPOSE:To decide modulation classification applied to each recording medium without providing a modulation classification information area on a track of the recording medium by obtaining pulse intervals peculiar to the modulation classification and collating them with pulse intervals appearing the reproduced output in the initial part and following parts. CONSTITUTION:Pulse interval data T/2, 3T/2, and 2T are obtained based on an obtained clock period T by operation. A control circuit waits for the rise of a reproduced output signal S2 while waiting for the rise of a read window signal S6; and when the rise of the reproduced output signal S2 is detected, pulse interval data is read from a pulse interval counter 14 and this counter 14 is reset, and an FM flag is set in case of the pulse interval T/2 but an MFM flag is set in case of the pulse interval 3T/2 or 2T. That is, a medium of FM modulation is decided in case the pulse interval T/2 is detected, and a recording medium of MFM modulation is decided in case the pulse interval 3T/2 or 2T is detected.
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