PURPOSE: To realize the composite exchange having ease of functional extension, by connecting a plurality of decentralized processors to an upper rank of centralized controller via a common bus and giving a common control function to the centralized controller.

CONSTITUTION: A telephone system terminal T, data system terminal D and special service terminal S are contained in independent channels 11, 21, 31, and they are controlled with entirely independent decentralized processors 12, 22, 32. The terminal attribute such as a signal system is entirely absorbed and the processor 32 makes the processing for storage service. The decentralized processors are connected to a upper rank centralized processor via a bus B unificationally for common management. Thus, the processor has hierarchy in the construction, and the composite exchange having easeness of functional extension is realized, by absorbing the attribute of different types of signals and functions to the decentralized processors.