| 摘要 |
PURPOSE:To restore quickly a disc to the normal operating state, by detecting a dropout of a reading signal of a disc record and operating the synchronizing clock reproducing circuit so that its output signal is made almost equal to the normal reproducing state in response to the detected output. CONSTITUTION:If a dropout takes place, an output signal of a frequency divider 24 is supplied to an input terminal of a phase comparator 19 of a synchronizing clock reproducing circuit 18 via a switching circuit 31 and the reproducing circuit 18 supplies a signal which has equal frequency to an output signal of the frequency divider 24 and is synchronized with the output signal to a demodulating circuit 17 and a phase comparator 22. Thus, the normal operation is kept to the demodulation circuit 17 even if the dropout takes place and the control system of a motor 12 comprising the phase comparator 22 controls the motor 12 at a rotating speed almost unchanged from the state before the dropout is produced. Thus, when the dropout is finished, the disc is restored quickly to the normal reproducing state. |
