| 摘要 |
PURPOSE:To remove interposed foreign matter and to decrease the number of force increasing circuits by holding a stylus force in a force increase state for a longer time between a time corresponding to a signal absence part and a constant time when a reproducing signal decreases below a prescribed value. CONSTITUTION:An RF output Vin after DC conversion is compared 11 with a V1 generated by the attenuating circuit composed of a CR circuit and resistance divisions on the basis of the Vin; when Vin<V1, the mixing of foreign matter is detected and a positive voltage V2 is outputted. The V2 is inputted to a constant-time holding circuit (e.g. monostable multivibrator) 13 composed of a CMOS NOR circuit, etc., to generate an output which becomes '0' a specific time later, and the output is added to the V2 by an OR circuit 19 to select a longer time; and addition 14 to a stationary stylus force is performed and the force is returned to a constant force a specific time later. This holding time should be longer than the time (a minimum number of tracks) required to pass a stylus through a foreign matter interposition point completely. This constitution decreases the number of force increasing circuits to remove the interposed foreign matter completely while reducing the damage to a disk.
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