Importance

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Abstract

An amplifier for amplifying a signal received on a telephone line and for providing the amplified signal to a telephone headset. The amplifier draws current from a battery. The current drawn is reduced in the absence of activity on the line. The amplifier includes a timer that generates a first control signal after a time-out time. The timer is reset by a second control signal. A threshold circuit generates the second control signal when the signal on the telephone line is above a threshold level. .[.Finally, a.]. .Iadd.A .Iaddend.circuit, responsive to the first control signal, reduces the current drawn from the power supply. The amplifier may additionally or alternatively include receive line muting. The amplifier includes an automatic level control circuit that receives the signal received on the telephone line and controls the level of the amplified signal provided to the headset to a set level in response to a second control signal. .[.Finally, a.]. .Iadd.A .Iaddend.control circuit generates the second control signal in response to the amplified signal provided to the headset and in response to the inverse of the first control signal. The inverse of the first control signal substantially reduces the set level. Finally, the amplifier includes a microphone amplifier with click-free muting.

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First Claim