Abstract: A receiver incorporating a phase-locked loop to demodulate a signal comprising a plurality of distinct baseband components is disclosed. The loop filter circuit includes an adjustable resistive element for varying the loop damping factor, thereby providing optimum separation of the baseband components. In addition, the loop filter circuit provides a bandpass high-frequency noise output to a noise-activated muting circuit.

Abstract: In a signal receiver having a potential source and an amplifier stage connected to a loudspeaker, a loudspeaker and amplifier protection circuit includes a normally closed switch coupling the potential source to the amplifier stage and a protection circuit coupled to the output of the amplifier stage and responsive to positive or negative polarity DC potentials for activating the switch to disconnect the power supply from the amplifier stage.

Abstract: A power amplifier and loudspeaker protection circuit for a receiver having an AC potential source with a center-tap transformer shunted by a full-wave bridge rectifier and a power amplifier directly coupled to a loudspeaker connected to a potential reference level includes a thermal relay means coupling the bridge rectifier through normally closed contacts to a power amplifier stage and an impedance coupling the transformer center-tap to a potential reference level to activate the thermal relay means and disconnect the potential source in response to increased current flow in a loudspeaker.