Automatic gain control device for a single-sideband receiver

Claim 1

An automatic gain control device for a single-sideband receiver, comprising: at least one variable-gain amplifier having an output for producing an output signal, a discriminator circuit for delivering one of a first or a second signal according to whether or not speech is present in a signal received by said receiver, detecting means coupled to said amplifier for producing one of a third or a fourth signal according to whether the level of said output signal is above a value V a , V a being a predetermined value corresponding to a predetermined correct listening level of said receiver, or below a value V b , V b being a predetermined value corresponding to a hearing threshold level of said receiver, and a control circuit, coupled to said discriminator circuit and to said detection means, said control circuit comprising controlling means for bringing the output level of said variable-gain amplifier to said value V a with a first time constant value when said third signal is present, to said value V a with a second time constant value when said third and fourth signals are absent and said first signal is present simultaneously, to said value V b with a third time constant value when said third and fourth signals are absent and said second signal is present simultaneously, and to said value V b with a fourth time constant value whenever said fourth signal is present.