PURPOSE: To reduce a noise to be transmitted at silent time by providing a transmission system voice signal processing part with a circuit which detects the voice signal of a caller, and mutes the voice signal at the silent time.
CONSTITUTION: The voice signal inputted to an input terminal A is compared with a reference level by a voice signal detection circuit 28 and if it is higher (or lower) than the reference level, a switch circuit 27 is closed so that transmission becomes possible. Next, when no signal is inputted to the input terminal A, the switching circuit 27 is opened, and is operated so that the voice signal, that is, the noise, generated in the transmission system voice signal processing circuit 2 is not outputted to an output terminal 13. Thus, since the noise generated in the transmission system voice signal processing part 2 comes not to be transmitted at the silent time, the receiver of other party is never given an unpleasant feeling.
AKITAKE ISAO
HANABUSA HIRONORI
HITACHI VIDEO ENG