processor 10 and the process processors 30 40 and 50 as shown in fig4 the processor state information table 13d is a table for storing information for identification of the states the states of control by the carrier controller 13 and the process controllers 33 43 and 53 of the process processors 10 30 40 and 50 the identification information holding means 13e stores a registration information signal given from the switching means 13g and a connection information signal given from a connection signal generating means which will be described later and holds these signals as information for identification as to whether the process processors 30 40 and 50 are validly connected to the carrier processor 10 on the basis of a logical judgment as shown in fig5 the communication means 13f has a bi directional communication function a csma cd communication system or a token ring communication system is used as the communication means 13f the communication means 13f communicates with the process controllers 33 43 and 53 through a communication medium 71 such as a stranded cable a coaxial cable etc the switching means 13g generates a registration information signal for registration as to whether predetermined one or ones of the process processors 30 40 and 50 to be connected to the carrier processor 10 are connected to signal lines respectively assigned thereto a dip switch operated by an operator or the like is used as the switching means 13g alternatively it is considered that the registration information may be stored in the switching means 13g for example an electrically erasable memory eeprom may be used as the switching means 13g to preliminarily store the registration information the process controllers 33 43 and 53.