Abstract: Disclosed is a communication system which improves the system flexibility and serviceability by efficiently controlling presence information. A presence inquiring section makes an inquiry about a presence state of a communicating party. A presence information receiving section receives presence information. A presence information display section displays the received presence information. A presence determining section determines the presence state. A presence information generating section generates the presence information. A presence information sending section sends the presence information upon reception of the inquiry.

Abstract: Disclosed is a communication system which improves the system flexibility and serviceability by efficiently controlling presence information. A presence inquiring section makes an inquiry about a presence state of a communicating party. A presence information receiving section receives presence information. A presence information display section displays the received presence information. A presence determining section determines the presence state. A presence information generating section generates the presence information. A presence information sending section sends the presence information upon reception of the inquiry.

Abstract: A digital time-divison switch comprising a multiplexer which multiplexes digitalized voice signals, supervisory signals transmitted from line circuit portions, and so forth, and which inserts these signals into predetermined time slots. The digital switch also includes a signal-extracting circuit which extracts the supervisory signals from the time slots assigned for control signals and which transmits the extracted supervisory signals to a common control unit through the supervisory signal receiver, a switching network which switches data time slots, a signal inserting circuit for transmitting control signals to the line circuit portions, and a distributor circuit for distributing the voice signals and so on to each line circuit.