| 摘要 |
PURPOSE:To keep a noise level to be applied to a listener after switching a voice switch circuit constant in level and to prevent the listener from feeling of physical disorder,by providing said circuit with a noise level detecting circuit, a variable attenuation circuit, etc. CONSTITUTION:An input signal including a voice signal and a background noise is applied to an input amplifier circuit 1 and a noise level detecting circuit 5 in the voice switch circuit and the input signal amplified by the circuit 1 is applied to a variable gain circuit 2. A channel switching controlling signal (a) is inputted to the circuit 2, the detecting circuit 5 and alpha variable attenuation circuit 6 to control the switch circuit in accordance with the state of the gain of the circuit 2. When the gain of the circuit is high under talking state, a noise signal generated in a noise generating circuit 7 is attenuated by the circuit 6 so as to be equalized with the noise level detected by the circuit 5 and the attenuated noise signal is added to the output of the circuit 2 by an adder and outputted. When the gain of the circuit 2 is low, the noise level detected by the circuit 5 is equalized with the noise level from the circuit 7 by the circuit 6 to remove the feeling of physical disorder to be applied to a listener. |
