PURPOSE: To deenergize a safety circuit by means of a switching circuit constituted by photocoupling elements, etc. adapted to be actuated on the OFF side of an operating switch installed in an electric source switch whereby eliminating the effect of induced noise.

CONSTITUTION: The system comprises a safety circuit 6 adapted to be actuated when a malfunction occurs, a setting coil (a) adapted to be actuated by the output of the circuit 6, a contact 8 adapted to interrupt electric current flow through a combustion control circuit 9 by means of coil (a), and a resetting coil (b) to reset the contact 8. Further, connected with the OFF side of an operating switch 2 adapted to control the passage of electric current through the circuits 6 and 9 is a light emitting unit (c) of an optical coupling element 15 comprising the light emitter unit (c) and a light receiver unit (d), and the resetting coil (b) is connected with the light receiver unit (d) through a switching element 18. In brief, the single operating switch 2 installed in the electric source switch enables the operation and deenergization of the safety circuit to be made, and it is only necessary to provide three remote control wires "A", "B" and "C". Therefore, the effect of induced noise can be prevented and also the number of remote control wires can be reduced.