| 摘要 |
PURPOSE:To prevent runaway of a servo system by detecting not only track deviation of an information reading point but also drop-out of a frame synchronizing signal to stop the operation of one of a tracking servo system and a disc rotative speed servo system at least. CONSTITUTION:The tracking error signal indicating deviation between relative positions in the radial direction of a disc of the information reading point on the recording disc and a track on the disc is supplied to a track deviation detecting circuit 9 and a loop switch 10. The circuit 9 detects that the information reading point transverses a prescribed number of tracks on the disc. Meanwhile, a synchronous detecting circuit 2 detects that a prescribed number of frame synchronizing signals included in an RF signal cannot be read continuously. Outputs of circuits 2 and 9 are inputted to a discriminating circuit 11 to control the switch 10, a PLL circuit 3, and a spindle servo circuit 8. Thus, runaway of a spindle motor 6, a carriage motor 15, and a tracking actuator 14 is prevented.
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