Electret microphone circuit
AssigneeThe Post Office
InventorsEdward G. T. Johnson, Adrian J. Morgan
Life of this patent
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Abstract
An electroacoustic transducer for a microphone comprises an electret wherein an additional capacitance substantially greater than the capacitance normally inherent in the electret is connected in parallel with the electret. The additional capacitance may be of the order of 10 times greater than the capacitance normally inherent in the electret and may be produced inherently in the transducer or by a separate component connected to the transducer.
Claims11
An electroacoustic transducer for a microphone, the transducer comprising an electret and means for reducing the impedance of the transducer so that the input impedance requirements of an amplifier connected to the transducer are correspondingly reduced, the impedance reducing means consisting of an additional capacitance substantially greater than the capacitance normally inherent in the electret in parallel with the electret, there being substantially no resistance provided in the transducer in series with the electret.
A telephone incorporating a microphone comprising an electret wherein an additional capacitance substantially greater than the capacitance normally inherent in the electret is connected in parallel with the electret.
Dependencies are inferred from the claim text.