PURPOSE: To hold a relay contact in cutoff state in a simple connection by a method wherein the oscillation of an oscillation circuit is stopped by the conduction of a short-circuit detection transistor and the open state of the relay contact is held by the conduction of a self-holding transistor.

CONSTITUTION: When a short-circuit current flows through a resistance 201, a transisor 202 is ON and the detected signal is supplied through a diode 211 to the point between the resistance 106 of the oscillation circuit means 100 and the plus terminal of a capacitor 109 to turn OFF transistors 101 and 102 and as a result a relay coil 10 is disenergized to open the relay contact to cutoff the short-circuit current. When the short-circuit current is cutoff, the current flows in turn through the transistor 202, resistances 207 and 208 and a diode 210 to turn ON a transistor 206. Under the condition as described above, the transistor 202 remains to be ON after the cutoff of the short-circuit current and continues to supply the short-circuit current detected signal. On the other hand, the oscillation circuit means 100 holds the short-circuit current in cutoff state during the time that the signal is being supplied.