PURPOSE: To eliminate a failure of one control table from affecting on the other control table, by connecting an occupancy request line and an occpancy permission line to a common priority circuit through a microprocessor respectively provided to a plurality of control tables.

CONSTITUTION: A microprocessor MPU is built in control tables 21W2n and they are connected to a device to be controlled 1 via a data bus 6 with the MPU for the giving/receiving of data. Each control table is connected to the priority circuit 5 with occpancy request lines 71W7n and occupancy permission lines 81W8n mutually. The circuit 5 discriminates the priority with the occupancy request signal from each MPU through the use of the software for the interlocking of operation information and when the device 1 is occupied with a specific control table for a prescribed time or more, an alarm is generated. The MPUs are decentrarizingly located for each control table and the interlocking is constituted witb the software, allowing to avoid a failure of a control table from being affected on the other control tables.