Patent ID: 6222928
Filing Date: 2001-04-24
Classification: H04R

Abstract:
An impedance matching circuit for coupling a microphone's output to a radio's microphone input wherein an input impedance for said microphone input is within a prescribed range, comprising:a tap circuit coupled to a microphone's output for extracting an audio signal therefrom, said audio signal having an AC component and a DC component;an amplifier circuit having DC blocking circuitry, said amplifier circuit coupled to said tap circuit for passing said AC component and blocking said DC component;an audio transformer having a primary winding and a secondary winding wherein a turns ratio of approximately 1:1 is defined, said primary winding having a characteristic DC resistance that is less than approximately 100 ohms and said secondary winding having an impedance that is within said prescribed range of said input impedance for said microphone input; anda driver circuit coupled between said amplifier circuit and said audio transformer for continuously driving said audio transformer with said AC component.