PURPOSE: To attain the communication with various terminal equipments on the condition of called party charging by detecting and registering caller number information element in a setup message received from a line, confirming the restoration of a caller and using the registered caller number to make loopback calling.

CONSTITUTION: A network 3 connects a telephone set 2 to an ISDN line 6 designated by a called party number in a setup message sent from the telephone set 2. A control section 10 of an exchange 8 searches the information element in the arrived setup message from a memory 11 and when the information is coincident with a stored password, the caller identification number in the memory 11 is checked, and when it is coincident, a call message is sent. A caller receives the message and restores itself once for waiting, then the exchange sends a loopback setup signal to the caller. When the telephone set 2 replies the call, the exchange calls the ISDN line 6 and the called telephone set 12 to make the talking between the telephone sets 2, 12 available. Thus, the charging is imposed onto the extension terminal equipment 12 being the apparent caller.