is grounded and the other terminal is pulled up by a pull up resistor 36 when the tact switch 35 is u201c closed u201d a u201c low u201d signal is output to the removable hard disk cartridge 1 and when the tact switch 35 is u201c open u201d a u201c high u201d signal is output 0045 fig6 is a view showing the arrangement of the removable hard disk cartridge 1 according to the second embodiment as is apparent from fig6 a signal switch signal from the tact switch 35 is connected to the input port of a control circuit 10 similar to an eject signal the switch signal is not defined by ivdr hard disk drive hardware standards and is assigned to an unused pin this embodiment adopts 45 pins of the connector 4 in ivdr hard disk drive hardware standards the tact switch 35 can be arranged not in the main body apparatus as shown in fig5 but in the removable hard disk cartridge 1 for example as shown in fig7 the tact switch 35 may be arranged on a surface of the housing of the removable hard disk cartridge 1 that is opposite to the connector 4 operation concerning an eject signal is the same as that described in the first embodiment with reference to fig3 and 4 and the operation of the eject mechanism is the same as that in the first embodiment in the second embodiment operation concerning the tact switch 35 which designates eject is added operation concerning the tact switch 35 which designates eject will be explained in detail with reference to the flow.