Abstract: A disk clamp for clamping a number of magnetic hard disks within a disk drive has a plurality of balance weight holes and a coined index mark for use as a reference in balancing the hard disks after assembly. The disk clamp also has a coined profile located adjacent or around the balance weight holes in order to provide uniform circumferential clamp force by the disk clamp. The disk clamp has a profile that places the inner region of the disk clamp in the plastic deformation region at a certain specified clamping force at the center of the disk clamp.

Abstract: A non-contact information processing device and a non-contact card medium issuing machine that can easily and quickly judge whether an electromagnetic radiation function of a non-contact communication antenna is working properly or not. Concretely to describe, provided is a card reader that includes non-contact information processing means for recording and/or reproducing information through electromagnetic induction without contacting a card medium; and a transfer path for transferring the card medium. The non-contact information processing means has a device-side non-contact communication antenna that is able to send and receive information to/from a medium-side non-contact communication antenna provided on the card medium. Provided is detection means for detecting if the device-side non-contact communication antenna is working normally.

Abstract: The present invention is to provide a card reader that can prevent the illegal acquisition of magnetic information recorded on a magnetic stripe, based on an output signal from a pre-head. More specifically described, in a card reader having a card insertion slot for guiding a magnetic card having a magnetic stripe to a transport passage and a pre-head arranged in the vicinity of the card insertion slot for detecting the presence of the magnetic stripe, the pre-head is equipped with a head portion having at least one pair of magnetic cores arranged to be opposite from each other having a magnetic gap between them and coils wound around a pair of the magnetic cores; and a signal different from that of the magnetic information recorded on the magnetic stripe is output from the pre-head.

Abstract: A device and a method for controlling a bit density of a magnetic card (2) are provided. Said control device comprises a stepper motor (1) providing power to drive the magnetic card (2) or a recording magnetic head (15), a transmission mechanism transferring power to the magnetic card (2) or the recording magnetic head (15), a CPU (10) sending magnetic recording information, a track data encoder (13) receiving a magnetic writing pulse signal (CLK1) and generating magnetic writing data in synchronization with the magnetic writing pulse signal (CLK1), and a magnetic head driving circuit (14) outputting a magnetic writing control signal based on the magnetic writing data. The frequency of the magnetic writing pulse signal (CLK1) and the frequency of a driving pulse signal (CLK0) of the stepper motor are in a linear relationship. Said control method is a method for controlling a bit density.