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.

Abstract: Key information from an attendant console is transferred to a telephone exchange in a bit serial manner, and line status information from the telephone exchange is also transferred in a bit serial manner and in a time-shared manner. At the request of the attendant console, the line status information is transferred from the telephone exchange to the attendant console in a bit serial manner, and subjected to serial-parallel conversion to obtain parallel signals for driving lamp indicator portions so as to provide an indication of the line status information. The number of signal lines connected to the attendant console is markedly reduced and, in the case of telephone number modification or the like, proper steps can be taken immediately.