PURPOSE: To simplify a control circuit by outputting a digital control signal to an output port at bits in a prescribed number, and using a serial signal converted by means of an output control means for the energizing control of output equipment.

CONSTITUTION: A parallel/serial converting means 110 is connected to the output port of a digital control means 100. The converting means 110 has a means to convert the serial signal into a parallel signal and a latch means 120. The digital control means 100 generates a pulse at a constant cycle by a timing control circuit 130 in synchronization with the serial signal emerging at the time of outputting the signal to the output port. The pulses at the constant cycle are automatically generated by a prescribed number whenever the synchronizing signal outputted by the control means 100 emerges, and they are impressed to the converter 110 and the control means 100 by a signal generating means 130. Since a bit signal is used for the energizing control, when the number of pieces of the output equipment is large, the large number can be coped with only by increasing the number of the bits of the control means 100, and a circuit constitution can be simplified.