PURPOSE: To eliminate the need for a long time for program load by dividing a program to be loaded, assigning a lead wire or a channel to each of each part and performing it in parallel with the program load.

CONSTITUTION: A main controller 2-1 is connected to plural slave controllers 2-2, 2-3 via a time division multiplex highway outgoing line 2-4 and an incoming line 2-5. One channel is assigned among the controllers 2-1, 2-2 and 2-3 and other plural channels (not shown) are assigned to general terminal devices. A program of a memory 2-7 is divided into N (in the figure N=4) by a microcomputer 2-6 as No.0∼No.3, four highways are occupied via a highway interface 2-8, transmitted in parallel with the slave controllers 2-2, 2-3 and stored in the memory section 2-7 via each highway interface 2-8. Thus, the time required for the program load is decreased to 1/4.