A desaturation circuit for an IGBT is disclosed. The disk recorder 2 prepares a block map for managing recording areas on the disks so that respective subblock data are recorded at such position that a rotational delay time of a head becomes minimum in accessing the subblock data recorded on the respective disks. Using weak radio waves usable without authorization, the transmitter transmits frequency data set therein as a frequency switching signal to a receiver. Additionally, this offset arrangement prevents the pins penetrating the secondary PCBs from penetrating the primary PCBs in the same manner.