Abstract: The invention discloses radio frequency zero crossing signal generators for optical disc drives, comprising a controllable low pass filter, a comparator, and a control circuit. The controllable low pass filter evaluates an average level of the magnitude of a radio frequency ripple from an optical disc drive. The comparator compares the radio frequency ripple to the average level evaluated by the controllable low pass filter to generate a radio frequency zero crossing signal. When the optical disc drive reads a fingerprint defect on an optical disc, the control circuit adjusts a cut-off frequency of the controllable low pass filter to adjust the speed at which the controllable low pass filter evaluates the average level.

Abstract: Four positioning holes or grooves of the first to the fourth positioning portions are formed on a shell as positioning portions to a disk drive apparatus. When two directions perpendicular to the thickness direction of a disk-shaped recording medium are designated as an X direction and a Y direction, the first and the second positioning portions are formed at the same position in the X direction, and the third and the fourth positioning portions are formed at the same position in the X direction, and further the first and the third positioning portions are formed at the same position in the Y direction, and still further the second and the fourth positioning portions are formed at the same position in the Y direction. When the disk cartridge is located to the disk drive apparatus at the insertion of the disk cartridge from an insertion opening, at least two of the four positioning portions are used.

Abstract: A MD loading mechanism for a multidisk MD reproducing apparatus capable of storing a plurality of MDs and of reproducing information recorded on the plurality of MDs successively comprises: a plurality of cartridge holders for holding MD cartridges therein, respectively; a MD cartridge storage unit for storing the plurality of cartridge holders therein in a stack so that the back end surfaces of the MD cartridges held within the cartridge holders can be seen from outside, provided with a plurality of insertion slots through which the MD cartridges are inserted in the cartridge holders and cartridge holder locking means for locking the cartridge holders within the MD cartridge storage unit; and a cartridge holder transfer means for transferring the cartridge holder holding a desired MD cartridge from the MD cartridge storage unit to the MD reproducing apparatus.