PURPOSE: To obtain a system of high reliability with a low cost, by controlling directly a subloop controller by an upper computer when the subloop controller has a fault.

CONSTITUTION: An upper computer 1 stores the control contents (contents of a specification table) of (n) units of subloop controllers 3 (SLC-1WSLC-n). Therefore it is possible to operate directly an electropneumatic converter 7 via an analog memory 6 in place of an optional one of the controllers SLC-1WSLC-N. The memory 6 can also be controlled manually, and the operation mode of the controller 3 is switched by a selector station 11 between the computer control and the munual control. Furthermore a switch is possible between the SLC side and the MOM side (control by upper computer) for the computer control.