| 摘要 |
PURPOSE:To stabilize the rotation of a disk motor and to obtain rapid random accessing with high reliability by eliminating a sampling pulse by a phase error detecting circuit at external synchronization, and holding an error signal value before accessing. CONSTITUTION:An external synchronous signal 1 enters a sampling and hold circuit 4 detecting a phase error through frequency dividing circuits 11, 3 and a rotating synchronous signal 9 and a reproducing vertical synchronous signal 10 are changed over by an external synchronous signal 8. This signal 8 changes over a switch 7 in case of a disk being not recorded and even during an external synchronization, and selects the signal 9. Further, the output of the switch 7 passes through a switch 6 opened and closed by a random access on/off signal 2 and enters the circuit 4 and the output is impressed to a phase compensating circuit 5. Thereby, when carrying out the random access during the external synchronization, the circuit 4 eliminates the sampling pulse and holds a rotating phase error signal before random accessing.
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