PURPOSE: To secure the decision for the control propriety of the controlled unit at the control center, by using the control inhibition and permission signals in addition to the selection and control signals.

CONSTITUTION: In addition to selection switches S1∼Sn and control switches CL and OP, control inhibition switch LK and control permission switch LO are provided. Memory circuit 14 memorizes both the control inhibition and permission of each controlled unit based on the setting signal of both control inhibition and control permission plus the selection signal of coding circuit 11. The output of circuit 14 is given to AND circuit 13'. Then three signals, the selection, control and control inhibition/permission signals, are sent to receiving circuit 28 of controlled unit 20 from circuit 13' through transmitting circuit 18. These three signals received are composed, and the control inhibition and permission signals are memorized in memory circuit 24. These memorized signals are then compounded to be applied to the controlled unit through output circuit 27.