PURPOSE: To decrease the power consumption by fetching the output of a specific channel selected by a strobe signal by a recirculate memory and transmitting repetitively the signal to a common transmission bus line.

CONSTITUTION: The strobe signal is supplied from a multiple address control section 60 to an IC1 for coding/decoding of a channel 1. A voice 8-bit code word of the channel 1 is fetched into a serial input/serial output shift register 72 through a data shift-in/recirculate changeover switch 71. When the time slot of the channel 1 is finished and transits to a time slot of a channel 2, the voice 8- bit code word of the channel 1 is transmitted to a common transmission bus line 40 from the serial input/serial output shift register 72. Further, the voice 8-bit code word of the channel 1 is fetched again into the shift register 72. These operations are repeated until the time slot of all channels is finished.