PURPOSE: To eliminate the need for the revision of network configuration when a conventional network is replaced with a packet switching network.

CONSTITUTION: A data format on a line 5 is defined as a synchronization pattern and (n) cells of an optional length and sequential numbers from 1 to (n) are imparted to cells starting from a cell just after the synchronization pattern. The sequential numbers from 1 to (n) are given to data processors 11-1n accommodated by the cell multiplexer 3 and data sent from the data processing units 11-1n are sent to a line while being set on a cell having the same number as that of the data processing unit. The cell received from the line 5 is sent to the data processing unit of the same number as that of the cell. The cell multiplexers 31, 32,...3n impart sequential numbers from 1 to (n) to terminal equipments and transfer the cell of the same number as that of the terminal equipment.