Patent ID: 6961551

Claim:
A squelch circuit comprising: an audio-removal filter coupled to receive an audio signal, the passband of the audio-removal filter being selected sufficiently high relative to frequency components of the audio signal; an absolute value detector coupled to the audio-removal filter to supply an output signal having a positive polarity regardless of the polarity of the signal supplied by the audio-removal filter; an integrating digital filter coupled to receive the output signal from the absolute value detector and supply a first integrated signal during a first mode of operation of the squelch circuit, and a second integrated signal during a second mode of operation of the squelch circuit, the integrating filter responsive to at least one selectable filter coefficient for selectively changing an integration response time of the integrating filter; and a control module configured to select a first numerical value for the selectable filter coefficient so that during the first mode of operation of the squelch circuit a first integration response time of the integrating filter is sufficiently fast to determine the power level of the first integrated signal over a predefined time interval relative to respective squelch thresholds, the control module further configured to select a second numerical value for the selectable filter coefficient so that during the second mode of operation subsequent to the first mode of operation a second integration response time of the integrating filter is sufficiently slow relative to the first integration response time of the integrating filter to smooth out power level variations, if any, in the second integrated signal.