To operate a relay for warning process which stops electric operation after the preset time has passed, by providing a structure to output a warning tone, light a warning lamp and simultaneously start operation of a timer immediately after irregular heat generation is detected.

When a temperature sensor 7 detects irregular heat generation, a contact r1-1 of a first relay 21 turns ON with an output ON signal via overheat detecting section 1 from a signal line 8 of the temperature sensor 7. Thereby, a warning buzzer 3 to which power supply is supplied from the power supply line 9 sounds, a warning lamp 4 lights and simultaneously a timer relay 5 starts its operation. A contact d1 of the timer relay 5 turns ON after the preset time has passed. When the contact d1 turns ON, a contact r1-2 of a second relay 22 turns OFF, thereby shutting off the power being supplied from the power supply line 10 to an electric device. After the process for the cause of irregular heat generation, operation can also be started.