| 摘要 |
PURPOSE:To prevent generation of ringing tone while preventing deterioration of talking quality by designing the titled amplifier that a gain of an automatic gain variable amplifier circuit at no talking side is lowered by an erasure deficient quantity from the existing gain at one-way talking and the gain of the automatic gain variable amplifier circuit at each talking side is lowered by a half of the erasure deficiency than the existing gain at two-way talking. CONSTITUTION:In case of one-way talking state (a state that a voice signal is detected from an incoming or outgoing voice detection circuit 11 is detected while an outgoing or incoming voice detection circuit 11 has not voice signal), the gain obtained from the automatic gain variable amplifier circuit 10 of the talking line of the voice detection side is given as it is, while the gain of the automatic gain variable amplifier circuit 10 of a channel of no voice side is changed into a gain lowered by the erasure deficiency Lx than the existing gain. In two-way talking state (a state that a voice signal is detected from the voice detection circuit 11 of both the incoming and outgoing directions), the gain of the automatic gain variable amplifier circuit 10 in any direction is changed into a gain lowered than the existing gain by 1/2 of the erasure deficiency Lx.
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