PURPOSE: To prevent a latch-up by using a first relay drive circuit to operate responding instantly to a variation of an input signal and to restore after delaying a specific time, and a second relay drive circuit to operate after delaying a specific time from a variation of the input signal and to restore responding instantly.

CONSTITUTION: A first relay drive circuit 10 which consists of a delay circuit consisting of inverters 2 and 6, a diode 3, a resistance 4, and a condensor 5; a buffer 7; a transistor 8 to drive the relay; and a relay 9 to apply or cut off the power source voltage of an IC and an LSI is provided. And a second relay drive circuit 20 which consists of a delay circuit consisting of inverters 12 and 16, a diode 13, a resistance 14, and a condensor 15; a buffer 17; a transistor 18 to drive the relay; and a relay 19 to apply or cut off the power source voltage of the IC and the LSI; and an input terminal 1 are provided. Consequently, a latch-up of the IC can be prevented.