PURPOSE: To simplify an operation and to make configuration compact and low-priced by housing a message register in the multifunction telephone set interface of an exchange and effectively utilizing the display function of the multifunction telephone set interface.

CONSTITUTION: The message register is housed in the multifunction telephone set interface of an exchange 10 and recognized as a normal multifunction telephone set from the exchange 10. When a call is incoming from an extension telephone set to the message register, display information concerning the extension number of a caller are sent from the exchange 10. Therefore, these information are analyzed by a control means 13 and even when the caller does not input an ID number, the extension number of the caller can be identified. Thus, it is not necessary to input the ID number at a conventional equipment and the configuration is made low-priced and compact. Further, the operation is simplified.