PURPOSE: To ensure a smooth transmission of the exchanging data in the multiple address communication or the like, by displaying occasionally the state of the terminal at the relaying destination and thus limiting the circuit connection to the specified terminal.

CONSTITUTION: The data exchange units 1 and 2 possess terminals 31∼33 and 41∼44 each to carry out the data exchange between the terminals of the self-station as well as the data exchange between the terminals within the remote device via the trunk line 5. The unit 1 possesses the device to transmit the state of the terminal of the self-station to the unit 2, the display unit 7 to display the state of the terminal within the unit 2, and the device 8 to accumulate the exchanging data respectively. At the same time, the unit 2 also possesses the devices having the similar functions. And the units 6 and 9 are connected to each other via the transmission line 11. Accordingly, the present state of the terminal in the remote device is displayed on the display unit of the self-station via the line 11 e.g. under blocking, and the corresponding terminal is excluded when the accumulated data are transmitted each. And the transfer is carried out later on.