PURPOSE: To prevent electric shock when an electric appliance has fallen into the water by splitting a solenoid for driving an automatic power source breaker arranged between a power source and a load into two sections and connecting a water immersion detector in series between them.

CONSTITUTION: A relay R is arranged between a power source S and a load L where the contact Po of the relay R is normally closed. One ends of solenoids S1, S2 are connected respectively with joints P1, P6, and a water immersion detector WS is connected with the other ends of the solenoids S1, S2. The detector WS is provided with a member H which is made conductive upon intrusion of water between tongues Pa, Pb, and the detector WS is arranged closely to the opening M of the case W. When an electric appliance, e.g., a hair drier, incorporating such circuitry falls erroneously into the water, the solenoids S1, S2 are connected and the relay R is driven to open the contact Po. By such arrangement, electric shock can be prevented.