PURPOSE: To offer an excellent decentralized type exchange system by separating a system having a terminal interface and a system having other network interface and installing decentralizingly the system having the terminal interface to a district.

CONSTITUTION: The above system consists of plural pre exchange systems (FESS) 5 accommodating terminal equipments and a post exchange system (BESS) 7 connecting to other network, and the pre exchange systems 5 are interconnected by relay lines 500 and each preexchange system 5 and the post exchange system 7 are interconnected by relay lines 510 respectively. The pre exchange systems 5 accommodate plural terminal equipments such as audio terminal equipments or data terminal equipments via a subscriber line 300 and they are arranged decentralizingly in the unit of terminal groups or of districts. The post exchange system 7 is installed to a specific district centralizingly and connects to a communication network such as a relay network 9. Thus, the line number attended with the utilizing efficiency improvement of the line is saved and the system copes flexibly with the addition or revision in the interfaces.