Audio signal quality indicating circuit

Claim 2

In a system for selecting one of a plurality of radio receivers arranged to receive a transmitted radio signal and connected to supply audio signals to a common utilization device, an improved circuit for indicating the quality of the audio signals, said circuit comprising: a. a logarithmic amplifier to which audio signals are applied; b. a detector connected to said logarithmic amplifier for producing an envelope signal from said audio signals; c. a circuit connected to said envelope detector for producing a unidirectional voltage having a magnitude proportional to the lowest voltage of said envelope signal and thus indicative of the quality of said audio signal; d. and output means connected to said unidirectional voltage producing circuit for utilizing said unidirectional voltage in a comparison circuit.

Claim 3

The improved circuit of claim 1 wherein said unidirectional voltage producing circuit has a time constant sufficiently long to maintain said unidirectional voltage between normal conversational audio signals.

Claim 4

In a system having a plurality of radio receivers at spaced locations for receiving a common transmitted radio signal and producing an audio signal in response thereto, and having means for selecting one of said radio receivers to provide audio signals for utilization, an improved circuit adapted to be used with each of said radio receivers for providing a signal whose amplitude is a measure of the quality of the audio signals produced by its respective receiver, said improved circuit comprising: a. an input for the audio signals from the respective receiver; b. a logarithmic amplifier coupled to said input for converting said audio signals to signals that vary in a substantially linear manner in response to the noise quieting of said radio receiver; c. an amplitude detector coupled to said logarithmic amplifier for producing an envelope voltage that varies as a function of the instantaneous peak voltages of said audio signals; d. a valley detector coupled to said amplitude detector for producing a voltage indicative of the minimum values of said amplitude detector voltage with respect to a reference voltage; and e. an output coupled to said valley detector for providing an output signal from said improved circuit for comparison with other output signals.

Claim 5

In a system having a plurality of radio receivers at spaced locations for receiving a common transmitted radio signal and producing an audio signal in response thereto, and having means for selecting one of said radio receivers to provide audio signals for utilization, an improved circuit adapted to be used with each of said radio receivers for providing a signal whose amplitude is a measure of the quality of the audio signals produced by its respective receiver, said improved circuit comprising: a. an input for the audio signals from the respective receiver; b. a logarithmic amplifier coupled to said input for converting said audio signals to signals that vary in a substantially linear manner in response to the noise quieting of said radio receiver; c. an amplitude detector coupled to said logarithmic amplifier for producing an envelope voltage that varies as a function of the instantaneous peak voltages of said audio signals; d. a valley detector coupled to said amplitude detector for producing a voltage indicative of the minimum values of said amplitude detector voltage with respect to a reference voltage; and e. an output coupled to said valley detector for providing an output signal from said improved circuit for comparison with other output signals.

Claim 6

The improved circuit of claim 3, and further comprising a constant current source connected to said output circuit for comparing the valley detector output signal with other valley detector output signals.