TRANSMITTING CIRCUIT OF VOICE SIGNAL

摘要

PURPOSE:To simplify the circuit constitution and to minimize the number of terminal pins when a circuit is converted into an IC, by giving a switching output with a low level of the mixture noise to either one of the two voice signals in preference to the other and transmitting these two signals after mixing them properly. CONSTITUTION:A muting switch circuit 18 mutes the output of the transmission system of the 1st voice signal (given from a microphone jack) when the 1st voice signal is not arrived. Then the impedance obtained when the circuit 18 is viewed at a variable resistor VR3 is set high in the muting active mode and low in the muting inactive mode respectively. As a result, only the 1st voice signal is preferably delivered through an output terminal 19 in the muting inactive mode of the circuit 18 regardless of the presence or absence of the input of the 2nd voice signal.