Cordless interphone

Abstract

PURPOSE: To make the squelch sensitivity constant independently of the temperature change by connecting a circuit element having a temperature characteristic changing reversely a bias point of a noise amplifier agains its fluctuating direction. CONSTITUTION: A thermister Th 1 representing a negative temperature characteristic is connected across a variable resistor VR 1 connected to an output of the noise amplifier NA. Since the resistance value of the thermister Th 1 is decreased as the temperature rises, the bias point of an output of the noise amplifier NA decreased and a reference value of a detection section is lowered, then the sensitivity of a squelch circuit 7 is increased as the temperature rises and the change in the squelch sensitivity against temperature is prevented. Further, when the output of the noise amplifier NA is increased at a high temperature, the thermister having a positive temperature characteristic is used. COPYRIGHT: (C)1987,JPO&Japio

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