PURPOSE: To identify the originating subscriber of an incoming call even when the call arrives from unknown terminal equipment by previously registering displaying information corresponding to incoming sub-addresses contained in incoming call numbers.

CONSTITUTION: When a subscriber makes an outgoing call, the terminal number of the communication equipment on the calling side arrives at the called side terminal equipment as an incoming call signal in addition to the called subscriber's number and incoming sub-address information. The incoming sub- address information and its corresponding displaying information are registered in an incoming sub-address collating information storing section 6 after a key input section 5 is set to the registering mode. Thus a calling signal sent from arbitrary communication equipment connected with an ISDN 1 is analyzed by means of a network interface section 2 and transmitted to a main control section 9 through a control bus 8 as incoming call signal information containing the information element of a call setting message. The main control section 9 discriminates whether or not an incoming sub-address is contained in the incoming call signal.