PURPOSE: To increase the power generating efficiency as well as the response property, by providing the fixed magnet in addition to the mobile magnet and then inducing the voltage to the coil with the magnetic flux flowing between the both magnets.

CONSTITUTION: When the cantilever 2 is at the neutral position, the mobile magnet 3 is positioned on the same plane to the fixed magnet 8L. As a result, the opposing pole faces have the same pole, and thus no magnetic flux flows between the opposing pole faces. And accordingly, no power is generated to coil 7L. Then when the needle 1 of the cantilever 2 falls into the hollow part on the wall surface of the L channel side of the record disk, the lever 2 tilts to the lower part in the direction of L. And thus the magnet 3 tilts to the magnet 8L, and accordingly the S pole of the magnet 3 comes close to the N pole of the magnet 8L. As a result, the magnetic flux flows between the S and N poles, and thus the voltage of a certain polarity is induced to the coil 7L and in proportion to the tilt of the lever 2. And the voltage of the opposite polarity is induced to the coil 7L in case the needle 1 rides onto the convex part on the wall surface of the L channel side of the record disk.