A diagnosis circuit 1 monitors a watchdog timer 2 and supplies a diagnosis result signal 1 indicating whether a monitoring result is normal or not to a diagnosis circuit 2. The power manager is connected to control several intelligent power modules each able to independently control the power onoff status of several network appliances. The disc spring extends in a direction of being inclined to the direction of the axis line from a first end portion toward a second end portion in a centrifugal direction. Other bus addresses are allocated as sequential reading mode bus addresses for addressing the ROM in sequential ROM address order for reading data.