JPS6315776B

PURPOSE:To prevent transient noise with no countermeasures at the receiving side by replacing a voice data part with a specific transient code for a prescribed time, at the PCM system switching. CONSTITUTION:A time width set device 23 outputs a signal representing a prescribed time width in synchronizing with a frame timing signal from a terminal 19, when a discriminating code inputted to a terminal 17 is changed. A code replacing device 24 replaces the PCM voice data part of each frame inputted from a terminal 21 by a specific transient code during the time width and supplies its output to a terminal 25. In a figure, the prescribed time width is equivalent to a portion of 5 frame, and no noise is generated at the receiving side even if the PCM demodulation system is changed over at any frame boundary in this 5 frame.