Abstract: PCM 24 channel digital voice information received from an incoming trunk are sequentially stored in a speech data memory device for respective channels through an input buffer memory device. The addressed content of the speech data memory device is read out by a control signal which has been stored in a control memory device and adapted to designate an address of the speech data memory device from which information is to be read out, and the read out information is sent to an outgoing trunk through an output buffer memory device thereby operating channel translation. The channel assigned to the outgoing trunk is different from that assigned to the incoming trunk. The speech data memory device, the control memory device and the program memory device are constituted by one memory means and the exchange of signals between the memory means and the input/output buffer memory devices as well as an arithmetic operation unit is effected by a programmed control of a program memory device.