PURPOSE: To individually and independently control output circuits by regulating a time for oscillating a frequency corresponding to an output circuit when any of the circuits is varied, and regulating power amount to be supplied to a secondary side of a transformer.

CONSTITUTION: An oscillator 1 has a Wien's bridge oscillator which receives power from an astable DC power source. In a transformer 2, a current having the same frequency as an oscillation frequency to be supplied to its primary side, flows, and the transformer 2 supplies power to an output circuit 4 through a band pass filter (special frequency transmitter) 3 for passing the frequency. When the output of the circuit 4 is varied, a microcomputer 5 senses the variation in the output of the circuit 4 from a predetermined value, judges whether a time for generating the frequency to be passed through the transmitter 3, corresponding to the circuit 4 for the oscillator 1 is lengthen or not, and varies an output to be sent to photocouplers 6a, 6b.