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. The switch further includes a second signal-inserting circuit disposed between the signal-extracting circuit and the switching network, the second signal-inserting circuit inserting one-way signals transmitted from a switching network portion to the line circuit portions into the time slots assigned for control signals, in the other words into time slots into which supervisory signals extracted by the signal-extracting circuit are previously inserted.