Muting circuit

Claim 2

In a receiver including carrier selection means for tuning to a selected signal and further including an information signal demodulator coupled to said carrier selection means, having a baseband output for supplying a demodulated signal to load means and having a logic output for providing a logic output signal, said logic output signal being of a first type when said information signal is present and being of a second type when said information signal is absent, a signal processing arrangement comprising: low-pass filter means coupled to said logic output for providing a low-pass filtered logic signal corresponding to said logic output signal, said low-pass filter means including filter capacitance means for storing charge, wherein first and second levels of stored charge correspond to said filtered logic signal being of said first and second types, respectively; resistance means having a first end coupled to said filter capacitance means and having a second end; first and second control means respectively coupled to said second end of said resistance means for respectively selectively setting said stored charge to said second level; and signal gate means having a control input coupled to one of said first and second ends of said resistance means, and being coupled between said baseband output and said load means for coupling said baseband signal to said load means when said filtered logic signal is of said first type and not coupling said baseband signal therebetween when said low-pass filtered logic signal is of said second type.

Claim 3

The arrangement recited in claim 1 wherein said control input of said signal gate means is coupled to said second end of said resistance means.

Claim 4

The arrangement recited in claim 2 wherein said first control means is coupled to said carrier selection means for setting said stored charge to said second level when said carrier selection means is being tuned from a previously selected signal to a newly selected signal.

Claim 5

The arrangement recited in claim 3 wherein said filter capacitance means comprises a shunt capacitance and said first and second control means respectively comprise potential clamp means for selectively and controllably discharging said shunt capacitance to said second level of charge.

Claim 6

The arrangement recited in claim 4 further including indicator means coupled to said low-pass filter means for indicating when said low-pass filtered logic signal is of a selected one of said first and second types.

Claim 7

In a receiver including carrier selection means for tuning to a selected signal and further including a frequency modulation (FM) demodulator coupled to said carrier selection means and having a demodulated output for supplying an audio signal to controllable audio signal processing means, said controllable audio signal processing means including inhibiting means with a control input for selectively inhibiting audio signal processing by said audio signal processing means, said demodulator further having a logic output for providing a logic output signal, said logic output signal being of a first type when the amplitude of said selected signal exceeds a first predetermined threshold amplitude and being of a second type when the amplitude of said selected signal is less than a second predetermined threshold amplitude, said second threshold amplitude being no greater than said first threshold amplitude, a signal processing arrangement comprising: shunt capacitance means coupled to said logic output for filtering said logic output signal, said capacitance means exhibiting first and second states of stored charge respectively corresponding to said logic signal being of said first and second types; resistance means coupled between said control input of said inhibiting means and said capacitance means for causing said inhibiting means to respectively inhibit and not inhibit the audio processing of said audio signal processing means when said capacitance means exhibits said second and said first states of stored charge; and first and second control means, respectively coupled to said control input of said audio signal processing means for setting said stored charge to said second state when said carrier selection means is being tuned away from a previously selected signal to a newly selected signal.

Claim 8

In a receiver including carrier selection means for tuning to a selected signal and further including a frequency modulation (FM) demodulator coupled to said carrier selection means and having a demodulated output for supplying an audio signal to controllable audio signal processing means, said controllable audio signal processing means including inhibiting means with a control input for selectively inhibiting audio signal processing by said audio signal processing means, said demodulator further having a logic output for providing a logic output signal, said logic output signal being of a first type when the amplitude of said selected signal exceeds a first predetermined threshold amplitude and being of a second type when the amplitude of said selected signal is less than a second predetermined threshold amplitude, said second threshold amplitude being no greater than said first threshold amplitude, a signal processing arrangement comprising: shunt capacitance means coupled to said logic output for filtering said logic output signal, said capacitance means exhibiting first and second states of stored charge respectively corresponding to said logic signal being of said first and second types; resistance means coupled between said control input of said inhibiting means and said capacitance means for causing said inhibiting means to respectively inhibit and not inhibit the audio processing of said audio signal processing means when said capacitance means exhibits said second and said first states of stored charge; and first and second control means, respectively coupled to said control input of said audio signal processing means for setting said stored charge to said second state when said carrier selection means is being tuned away from a previously selected signal to a newly selected signal.

Claim 9

In a receiver including carrier selection means for tuning to a selected signal and further including an information signal demodulator coupled to said carrier selection means and having a baseband output for supplying a demodulated signal to load means and having a logic output for providing a logic output signal, said logic output signal being of a first type when said information signal is present and being of a second type when said information signal is absent, a signal processing arrangement comprising: capacitive filter means coupled to said logic output for low-pass filtering said logic signal; signal gate means having a control point and being coupled between said baseband output and said load means for selectively coupling said baseband signal to said load means when a logic control signal at said control point is of said first type and not coupling said baseband signal therebetween when said logic control signal is of said second type; first and second control means respectively coupled to said control point for respectively selectively setting said logic control signal at said control point to be of said second type; and resistance means coupled between said capacitive filter means and said control point for providing a resistive coupling between said capacitive filter and each of said first and second control means.

Claim 10

In a receiver including carrier selection means for tuning to a selected signal and further including an information signal demodulator coupled to said carrier selection means and having a baseband output for supplying a demodulated signal to load means and having a logic output for providing a logic output signal, said logic output signal being of a first type when said information signal is present and being of a second type when said information signal is absent, a signal processing arrangement comprising: capacitive filter means coupled to said logic output for low-pass filtering said logic signal; signal gate means having a control point and being coupled between said baseband output and said load means for selectively coupling said baseband signal to said load means when a logic control signal at said control point is of said first type and not coupling said baseband signal therebetween when said logic control signal is of said second type; first and second control means respectively coupled to said control point for respectively selectively setting said logic control signal at said control point to be of said second type; and resistance means coupled between said capacitive filter means and said control point for providing a resistive coupling between said capacitive filter and each of said first and second control means.

Claim 11

The arrangment recited in claim 7 wherein said first control means is coupled to said carrier selection means for automatically setting said logic control signal at said second level when said carrier selection means is being tuned away from a previously selected signal to a newly selected signal.

Claim 12

The arrangement recited in claim 8 wherein said receiver is a television receiver, said demodulator is an frequency modulation demodulator and said demodulated signal is a secondary audio program signal.