| 摘要 |
PURPOSE:To detect an index signal accurately at all times, by comparing the integration output of a rectangular pulse corresponding to a control signal in which the duty forming the index signal is changed and an opposing polarity pulse, respectively. CONSTITUTION:A playback control signal forming an index signal with the change in the duty via an amplifier 2 is processed at positive/negative polarity pulse separating circuits 3, 4, a missing signal correcting circuit 6, and an FF5. Then, a rectangular pulse (f) and an opposite polarity rectangular pulse (f') according to the duty are generated from the FF5 and they are respectively integrated at integration circuits 7, 9. When the integration outputs (g), (g') are compared at a comparison circuit 10 by taking the output (g') as a reference, the effects such as change in playback speed and ambient temperature are canceled with a section output (h) where the output (g) is smaller than the (g'), allowing to detect index signals accurately at all times. |
