Abstract: A supervisory image communication system by an ISDN includes a parent station and a plurality of child stations connected to the parent station by way of an ISDN basic interface and an ISDN switched network. Any of the child stations transmits call originating information to originate a call to the parent station, and the parent station supervises, in response to the call originating information, the state of the child station in accordance with image information subsequently inputted thereto from the child station. When a child station detects an emergency condition and tries to notify this to the parent station, a call originating reason representative of information of the emergency condition is added as sub-address information to call originating information to be transmitted. Upon acceptance of such call originating information from the child station, the parent station detects the sub-address information thus transmitted thereto and identifies the call originating reason.