PURPOSE: To improve the operability by providing a function displaying the arrival of a call even during system setup, storing the system setting content and restoring the state to the communication state to the processing unit.

CONSTITUTION: When a call comes from an ISDN 6 in the system setting state, the information is sent from a communication control section 1 to a state monitor section 5. The monitor section 5 displays incoming call information on a display section 4. Then the user confirms the arrival of an incoming call. The user discriminates whether or not the call is to be received and implements key operation for the reception when the user desires the reception. The monitor section 5 stores the current state and the setting value set so far and restores the state to the communication enable state to make communication with an opposite party making a call. The monitor section 5 transits the state to the system setting state again in the state of end of communication to continue the system setting. When the user does not desire the reception, the monitor section 5 receiving the key operation of continuity of system setting allows the control section 1 to send a signal of incoming call rejection to the ISDN and transits the system setting state automatically.