Abstract: Example embodiments include devices and systems that detect apnea events of a user. The device includes a first sensor configured beside the head of the user for capturing snoring sounds of the user, a second sensor configured on one finger of the user for capturing cardiovascular parameters of the user, a third sensor configured under the trunk of the user for capturing e breathing movements of the user, a data recorder that is connected with the first sensor, the second sensor and the third sensor for receiving recordings therefrom, and a clock for synchronizing the recordings in real time. The recordings include one or more breathing events including snoring events, heart rate and SPO2 conjunction spikes, and breathing movement cessations. The time periods that apnea events are impossible can be excluded according to a combination of the breathing events, and the apnea events can be detected thereafter.

Abstract: A load-insensitive power amplifier power detector that excludes the use of couplers is disclosed. The load-insensitive power amplifier power detector may include a voltage sampling circuit in electrical communication with a collector of a power amplifier and configured to sample a first voltage from the power amplifier. The load-insensitive power amplifier power detector may include a current sampling circuit in electrical communication with the collector of the power amplifier and configured to sample an output current from the power amplifier. Further, the load-insensitive power amplifier power detector may include a current-to-voltage converter connected between the voltage sampling circuit and an output of the load-insensitive power amplifier power detector. The current-to-voltage converter may be configured to convert the output current to obtain a second voltage.

Abstract: A radio receiver system configured to remove click noise from a demodulated signal is disclosed. The radio receiver system may employ digital demodulation or analog demodulation. The radio receiver system may be configured to determine measures of a statistical distribution of amplitudes of the demodulated signal, and thresholds for limiting the demodulated signal based on the measures of the statistical distribution of amplitudes. Portions of the demodulated signal exceeding the thresholds are either soft limited or hard limited.

Abstract: Aspects of the disclosure provide for a circuit including a squelch detector having a first input coupled to a first node and configured to receive a positive component of a differential signal with a floating center tap, a second input coupled to a second node and configured to receive a negative component of the differential signal, and an output coupled to a logic circuit, a first resistor coupled between the first node and a third node, a second resistor coupled between the third node and the second node, a third resistor coupled between the first node and a fourth node, a fourth resistor coupled between the fourth node and the second node, a capacitor coupled between the fourth node and a ground terminal, a comparator having a first input coupled to the third node, a second input coupled to a fifth node, and an output coupled to the logic circuit.

Abstract: A communication apparatus includes an NFC circuit, an FM receiver, a level detector, and an NFC control circuit. The NFC circuit is configured to make wireless communication with a communication apparatus of a communication partner using a specified communication frequency. The FM receiver is configured to adjust a radio reception range to a band including a multiplied frequency of the communication frequency. The level detector is configured to detect a reception level of the band when the FM receiver receives the band including the multiplied frequency. The NFC control circuit is configured to control the NFC circuit to reduce transmission power in the NFC circuit when the reception level is smaller than a predetermined threshold value.

Abstract: An audio system includes a channel (10) for processing signals. The channel (10) includes a processing module (50) that follows a chain of modules (40) wherein the chain (40) includes a preceding processing module (45). The following processing module (50) is coupled to the preceding processing module (45) in the chain of modules (40) for receiving the output signal (25). The channel (10) further includes a combiner (60). The combiner (60) has two inputs, a first input (65) receives the signal (30) to be processed in the channel (10), and a second input (70) receives a reference signal (75). The combiner (60) further includes an output (80) coupled to an input of the preceding processing module (45) in the chain (40).

Abstract: Several circuits and methods implemented to perform signal quality estimation and control are disclosed. In an embodiment, a method of signal quality estimation includes generating a demodulated signal associated with a radio signal. Information associated with a quality of the demodulated signal is accessed. Further, a value of radio frequency signal-to-noise ratio (RF-SNR) for the radio signal based on the information is estimated. Estimating the value of RF-SNR facilitates in signal quality estimation of the radio signal and control of the demodulated signal.

Abstract: A wireless device capable of reliably detecting a tone squelch signal in a short time is provided. The wireless device which detects a tone squelch signal contained in received baseband signals is provided with: a frequency shifting unit (quadrature demodulation unit (503)) which shifts the received baseband signal in the negative frequency direction by a preset frequency of a tone squelch signal; LPF (504-1, 504-2) for eliminating unnecessary frequency components from the output of the frequency shifting unit; and an assessment unit (510) which assesses presence/non-presence of the tone squelch signal on the basis of the output from the LPF (504-1,504-2).

Abstract: A communication device comprises logic and an input device coupled to the logic. The input device is adapted to permit a user to select a communication type. The logic receives a communication in a first communication type and permits a user to reply to the communication using any of a plurality of user-selectable communication types.

Abstract: An IR receiver having a decision logic circuit for activating or deactivating a squelch. Activation or deactivation of the squelch is effected in dependence on a mean value of the frequency, a variance of the receiver intermediate frequency, a mean value of the audio amplitude, a variance of the audio amplitude and/or a signal strength of the receiver intermediate circuit frequency.

Abstract: A squelch detector includes a first circuit, a second circuit, and a comparator. The first circuit is configured to receive a first pair of differential input signals and in response output a second pair of differential signals. The second pair of differential signals have higher voltages than the first pair of differential input signals. The second circuit is coupled to the first circuit and is configured to extract first and second voltage levels from the second pair of differential signals. The comparator is configured to output a squelch level signal based on a comparison of the first voltage level and a third voltage level. The third voltage level is based on the second voltage level and a reference voltage.

Abstract: The present invention provides a gain control circuit for an FM receiver that can reduce a reproduced audio output according to the magnitude of the noise component of an intended signal included in a received signal. The gain control circuit of the present invention is constituted by a noise level measurement circuit 26 and a preamplifier 25. The noise level measurement circuit 26 measures a noise level in an audio signal Sa1 output from an FM detector 4 and outputs a control signal Sc corresponding to the noise level. The preamplifier 25 reduces an output according a value of the control signal Sc. With the gain control circuit of the present invention, the volume of the speaker is reduced as the noise component in the audio signal Sa1 increases due to a decrease in received electric field strength, and therefore discomfort caused by unpleasant noise can be reduced.

Abstract: A channel scanning technique and apparatus provides audio hole suppression in two-way radio communications. Upon detecting the absence of a carrier signal on a priority channel during a priority scan mode of operation, a training waveform is constructed upon returning to the home-channel. The training waveform is applied to audio shaping filters within an audio lineup to suppress transients and minimize or eliminate the occurrence of audio pops at a speaker output thereby reducing the audio hole.

Abstract: A device for generating a crest factor reduced signal is disclosed. The device comprises an interface for receiving an input signal; a peak identifier for identifying one or more peak regions of the input signal; a squelch level determiner for determining a reduction of the input signal near the one or more peak regions; a squelcher for reducing the one or more peak regions of the input signal as indicated by the squelch level determiner; and an interface for outputting a crest factor reduced signal. The crest factor reduced signal has a reduced dynamic range due to the reduction of the one or more peak regions of the input signal. The crest factor reduced signal also has been filtered to reduce undesired frequency components by: calculating a difference between a squelched signal from the squelcher and the input signal, band-pass filtering the difference to generate a result, and summing the result with the input signal that has been delayed.

Abstract: In a radio receiving apparatus, an analog received signal is converted into a digital received signal. An unwanted wave in an adjacent channel band is rejected, that is adjacent to a passband for the digital received signal. The digital received signal with no unwanted wave is converted into a first demodulated signal. The first demodulated signal is converted into a second demodulated signal in analog form. A noise component is extracted from the first demodulated signal. The second demodulated signal is suppressed under squelch control when a squelch voltage that is a voltage of the noise component after rectification and smoothing becomes equal to or higher than a predetermined threshold level.

Abstract: A constant modulus indicator (CMI) measure is calculated for a received signal having a constant modulus component C and a noise component N. The CMI measure indicates a ratio of an energy of C to an energy of N. A determination of whether to attenuate a derived signal is made based on the CMI measure, wherein the derived signal is generated from the received signal. The derived signal is attenuated based on the determination.

Abstract: Apparatus (40) comprising a voltage input (49) for applying an unfiltered voltage (V_unfil) and a current input (48) for receiving a bias current (Ib) from a current source. The apparatus (40) further comprises a differential filtering resistive circuit with a first current mirror (44) and a second current mirror (43), being situated between a common output node (50) and said voltage input (49). A first mirror circuit (42) for mirroring the bias current (Ib) to said first current mirror (44), and a second mirror circuit (41) for mirroring a current (Ix) to said second current mirror (43) are employed. A filter capacitor (51) situated at the output side of the apparatus (40), said filter capacitor (51) being connected on one side to said common output node (50) and on the other side to ground. The apparatus (40) provides a filtered output voltage (V_fil) at said common output node (50).

Abstract: A method and an apparatus for squelch gating a receiving signal depending on the level of phase noise in said receiving signal determines sampled amplitudes and sampled phases of said receiving signal, determines sampled phase noise by differentiating subsequent sampled phases, determines a squelch signal by rectifying and averaging said sampled phase noise, determines a start point of gating after a rising of said squelch signal above a higher threshold delayed by a first delay time, determines a end point of gating after a dropping of said squelch signal below a lower threshold delayed by a second delay time and gates said sampled amplitudes from said start point of gating until said end point of gating.

Abstract: In an audio muting circuit, after a short delay from a first time at which a first mute signal generation circuit causes a first mute signal to fall from “H” level to “L” level, a second mute signal generation circuit causes a second mute signal to fall from “H” level to “L” level at a second time. A third mute signal generated by combining the first and second mute signals is caused to fall from “H” level to a predetermined level at the first time, and caused to fall from the predetermined level to “L” level at the second time. Thus, at the start of muting, the level of an audio signal is increased in stepwise manner. In this way, noise generated at the start of muting can be reduced.

Abstract: Apparatus, and an associated method, for companding communication data. Companding is provided for a two-way radio communication station operable pursuant to a coded squelch scheme, such as an MURS or FRS radio. A baseband processor invokes compression operations upon originating communication data that is originated at the communication station. And, the processor invokes operation of expansion operations when the communication data comprises terminating data.

Abstract: Embodiments of the present invention can be used to enhance signals in a peer-to-peer radio system, such as a two-way radio system. In one embodiment, the invention includes receiving a communications signal on a channel from a remote radio at a radio using a plurality of antenna elements, such as an antenna array. The received communications signal includes a squelch code. The radio detects the squelch code, and enhances the received communications signal using the squelch code.

Abstract: A squelch detector that differentially detects a presence of a communication signal on a communication channel. The squelch detector being coupled to outputs of a differential offset bias amplifier to receive differential offset biased signals and generate a differential direct current signal.

Abstract: A squelch circuit and a communication apparatus used with the same that are able to generate a squelch signal even if a squelch period is short and an operation of a squelch detecting circuit is insufficient, the circuit having: a squelch detecting circuit detecting the existence of a signal on a communication line in response to a transmission signal or a received signal and generating a first squelch signal; and a squelch control circuit generating a squelch mask signal in response to the first squelch signal and a transmission control signal and generating a second squelch signal based on the squelch mask signal and the control signal. The first squelch signal is controlled by the transmission signal to generate the second squelch signal in which the lacked portion of the first squelch signal is temporally restructured.

Abstract: A device for generating a crest factor reduced signal is disclosed. The device comprises an interface for receiving an input signal; a peak identifier for identifying one or more peak regions of the input signal; a squelch level determiner for determining a reduction of the input signal near the one or more peak regions; a squelcher for reducing the one or more peak regions of the input signal as indicated by the squelch level determiner; and an interface for outputting a crest factor reduced signal. The crest factor reduced signal has a reduced dynamic range due to the reduction of the one or more peak regions of the input signal. The crest factor reduced signal also has been filtered to reduce undesired frequency components by: calculating a difference between a squelched signal from the squelcher and the input signal, band-pass filtering the difference to generate a result, and summing the result with the input signal that has been delayed.

Abstract: A power clipping circuit and method of the clipping circuit is provided. A power clipping circuit comprises, a selector which receives a baseband signal, and selects one of the baseband signal or a feed back signal, and outputs a selected signal, and a square clipping circuit which receives the selected signal, and limits an amplitude of the selected signal, and outputs a clipped signal, and a phase rotation circuit which receives the clipped signal, and rotates a phase of the clipped signal, and outputs a phase rotated signal to the selector as the feed back signal, and an amplitude scaling circuit which receives the phase rotated signal, and adjust the phase rotated signal to compensate an amplitude difference between the phase rotated signal and the clipped signal, and sends amplitude scaled signal, and a controlling circuit which controls the selector, the square clipping circuit, the phase rotation circuit and the amplitude scaling circuit.

Abstract: A radio receiver, optionally used in conjunction with a handheld audio system, includes a radio stage for processing a received radio signal into an audio signal. An audio stage produces an audio output, based on the audio signal. An overload monitor detects an overload condition in the radio stage and generates an overload signal in response to the detected overload condition. A controller controls the audio output in response to the overload signal.

Abstract: A stereo demultiplexer is proposed which can be calculation power efficiently implemented in a DSP. Modern digital FM receivers exploit the information content in the in quadrature component of the modulated difference signal for a noise reduction. The proposed stereo demultiplexer derives the in phase component and the in quadrature component of the difference signal with a minimized number of sinus and cosinus calculations by first downconverting the modulated difference signal to a not synchronized complex baseband signal on basis of a fixed frequency, thereafter a complex sampling rate decimation unit sampling rate decimates the not synchronized complex baseband signal with a factor N and a second complex mixer synchronizes and coherent demodulates the sampling rate decimated not synchronized baseband signal on basis of a first complex carrier signal derived on basis of the pilot carrier signal and the fixed frequency.

Abstract: A system and method used for controlling an attenuator in a two-way communication device (100, 200) includes the steps of measuring (211) a relative signal strength indication (RSSI) at the input of the two-way communications device. The RSSI measurement is then compared (213, 217, 223) to both at least one predetermined interference threshold value (T1, T2, T3) and a selective squelch state (219, 225) for determining whether to switch an in-line attenuator to the input of the two-way communications device. The invention provides a method by which an attenuator may be used only when interference is present without it being continually switched in-line to cause signal degradation.

Abstract: Systems and methods for reducing interference in an enhanced radio receiver from a transmitter when both are located in the same aircraft are provided. The enhanced radio receiver detects and attenuates a signal from the transmitter, without attenuation or interference with other desired signals. An enhanced radio transmitter may inform the enhanced radio receiver of the frequency of transmission via a data communication path such that the enhanced radio receiver attenuates the transmitted frequency for the duration of transmission.

Abstract: Embodiments of the present invention can be used to enhance signals in a peer-to-peer radio system, such as a two-way radio system. In one embodiment, the invention includes receiving a communications signal on a channel from a remote radio at a radio using a plurality of antenna elements, such as an antenna array. The received communications signal includes a squelch code. The radio detects the squelch code, and enhances the received communications signal using the squelch code.

Abstract: Herein disclosed a communications system according to the present invention comprises, a wireless microphone transmission apparatus for transmitting a radio microphone signal on a predetermined wireless microphone frequency channel carrying a voice signal and a tone signal; and a wireless receiving apparatus for receiving the radio microphone signal on the predetermined wireless microphone frequency channel carrying the voice signal and the tone signal transmitted by the wireless microphone transmission apparatus. The wireless receiving apparatus includes an integral computing unit for sequentially computing integrals of the signal levels of the tones of the tone signal at first predetermined time intervals and a data information computing unit for sequentially computing differences between two respective integrals of the signal levels of the tones of the tone signal, at respective second predetermined time intervals to acquire data information.

Abstract: Herein disclosed a communications system according to the present invention comprising: a wireless microphone transmission apparatus for transmitting a radio microphone signal on a predetermined wireless microphone frequency channel carrying a voice signal and a tone signal; and a wireless receiving apparatus for receiving the radio microphone signal on the predetermined wireless microphone frequency channel carrying the voice signal and the tone signal transmitted by the wireless microphone transmission apparatus. The wireless microphone transmission apparatus according to the present invention includes a data generating section for judging the type of data information, and generating a data string in response to the type of, and on the basis of the data information, and a tone signal generating section for generating a tone signal on the basis of the data string generated by the data generating section 22, thereby increasing the efficiency of the communications system.

Abstract: Provided is a device for improving voice signal in quality by discriminating a radio environment of a signal transmission path and detecting a click noise. The device for improving voice signal in quality calculates an average value for a short interval of a received ADPCM code, identifies from such average value the nature of a radio environment of a signal transmission path, and considers that a click noise is occurred when the average value exceeds a threshold value assigned radio environment. The present invention comprises a click noise detector (22) for outputting a click noise detecting signal, and a click noise suppressing circuit for suppressing the click noise by setting the velocity coefficient of an ADPCM decoder (21) as “0” for a frame in which a frame error detecting signal, which represents the detection of a frame error of the received ADPCM code, and a click noise detecting signal are both detected.

Abstract: A walkie-talkie device applies a continuous tone-coded squelch system (CTCSS) to control signal transmission. The walkie-talkie device has an analog-to-digital converter, a digital signal processor, and a digital-to-analog converter. The signal processing method includes using the analog-to-digital converter to convert a first analog signal into a first digital signal, using the digital signal processor to handle a CTCSS tone related to the first digital signal for generating a second digital signal, and using the digital-to-analog converter to convert the second digital signal into a second analog signal. The walkie-talkie device uses the CTCSS tone to discriminate a required speech signal from other speech signals transmitted by the same physical channel.

Abstract: A squelch circuit with an adjustable reference level, having an input level comparator with a first, a second, a third and a fourth current input terminal, a first and a second input terminal, and an output terminal. A first current source is coupled between the first current input terminal and an operation voltage. A second current source is coupled between the second current input terminal and the operation voltage. A third current source is coupled between the third current input terminal and a ground terminal. A fourth current source is coupled between the fourth current input terminal and the ground terminal. A bias generator is coupled to the first, second, third and fourth current sources to generate current control signals thereto according to a reference current and control bits, such that the first, second, third and fourth current sources generate the same current, which adjusts the reference level.

Abstract: A system, apparatus and method for inhibiting the ringer of a cellular telephone within a noise sensitive area includes a transmitter for generating a control signal within the area. A receiver within the cellular telephone generates a mute signal during reception of the control signal which inhibits operation of the telephone ringer circuit while the telephone is in the noise sensitive area. In an alternate embodiment, a transmitter of limited range is placed at each entrance to the noise sensitive area and the ringer circuit is inhibited upon momentarily receiving the control signal entering the area, and activated upon momentarily receiving the control signal exiting the area.

Abstract: There is provided an improved receiver unit for wireless microphone system. The receiver unit accomplishes desirable mute control in accordance with state transmitting conditions of electric wave from a wireless microphone.

Abstract: A radio carrier signal is detected (20) after being converted to digital form and is filtered (22). A noise estimator (24) generates a noise estimate signal by estimating the noise in the detected signal due to atmospheric conditions and the noise due to the gain in noise figure properties of the circuitry. The output of the noise estimator is used to calculate a threshold signal (50) and another detection operation (52) determines whether the power of a signal derived from the detected signal exceeds the threshold. If the threshold is exceeded, the detected signal is passed through a signal conditioner, such as a switch (54) to an output path (56).

Abstract: An improved squelch system (10) is provided in accordance with the present invention. The system includes a high-deviation subsystem (20) to detect a carrier with modulation, and a low-deviation subsystem (30) to detect the carrier with minimal modulation. If either the high-deviation system (20) or the low-deviation system (30) indicate a signal of sufficient strength, an output for the squelch system is set to un-mute, otherwise the output (70) is set to mute.

Abstract: A method for noise reduction during FM reception and a receiver executing the method. A detected audiosignal is being attenuated. A field strength indicative muting control signal is derived from an IF signal which is used to control an attenuation of the audiosignal, when the field strength decreases below a certain threshold level. To prevent false mute responses from distorting the audiosignal, a time constant in the mute control signal is increased with an increasing deviation of the momentary frequency of the received FM signal from the FM carrier frequency and vice versa.

Abstract: The Vehicle Sound and Alerting System is generally comprised of a conventional automobile stereo system that has police radar detection capabilities. When police radar is detected, the stereo's volume is immediately muted. An audible alert is then outputted through the vehicle's speaker system or a built-in speaker on the control panel, or a combination of both, depending on how the driver has it configured. A visual alert is also produced on the control panel, which displays the band of radar that was encountered, and its relative signal strength. The radar detector receives signals from the vehicle's antenna and an auxiliary antenna. The auxiliary antenna is attached to the vehicle's grille. This improves the signal reception ability.

Abstract: A wireless communication system comprises a filter and amplifier for filtering/amplifying only a necessary band frequency from a receive information signal induced by an antenna and passing a duplexer portion; a mixer for mixing the band frequency with a phase synchronizing signal from a local oscillating portion; a demodulating portion for demodulating a signal from the mixer and supplying the demodulated signal to a speaker; a receive tone squelch circuit for separating a sound signal from the demodulated signal; a transmit modulating portion for combining a transmit signal input with a transmit tone squelch frequency from a transmit tone squelch circuit and demodulating the combined signal; a controller for converting a code previously inputted into a code inputting portion into a frequency and tone squelch code; a memory for storing data, which is coded corresponding to a frequency channel data and a tone squelch code selected by the controller, at a predetermined address region; and a display for represe

Abstract: A two-way radio (1) that has a radio frequency receiver (2) having a modulated radio frequency signal output and a variable bandwidth filter (3) with an input coupled to the modulated radio frequency signal output. The radio (1) also has demodulator circuitry (4), a speaker (6) and processing circuitry (5). In use when the radio (1) is operating in squelch mode, the processing circuitry (5) controls the variable bandwidth filter (3) to have a first bandwidth and when in unsquelch mode the processing circuitry (5) controls the variable bandwidth filter (3) to have a second bandwidth which has a smaller frequency range and the first bandwidth.

Abstract: A squelch circuit for a radio receiver that detects the presence of speech by utilizing a filter bank for filtering an intermediate frequency or baseband signal from the radio receiver into band-pass signals, detecting the magnitude of the band-pass signals, and separating the signal magnitudes into a speech and noise detector. The speech detector determines if speech is present by determining if syllabic variations are present in the speech detector signals and selects a voice band average signal with a maximum difference in syllabic variations, and generates a speech detector decision when speech is present. The noise detector makes a noise detector decision when speech is present by obtaining a minimum noise detector signal and comparing the minimum noise detector signal to a threshold scaled voice band average signal associated with the maximum difference in syllabic variations.

Abstract: A mobile communication receiver generates an audio signal from a radio signal received on a communication channel, detects conditions on the communication channel, mutes the audio signal according to a first rule when the channel conditions are bad, and un-mutes the audio signal according to a second rule when the channel conditions are good. The first rule is more stringent than the second rule; as a result, sporadic muting and choppy muting are avoided.

Abstract: In a receiver, either an FM/AM signal to be used for a keyless entry system or a high frequency signal to be used for an automobile audio system for FM broadcast is applied to a first converter. An IF limiter amplifier amplifies the output signal of the converter and subsequently limits the amplitude of the output signal to a predetermined level. An FM detector circuit FM-detects the output signal of the IF limiter amplifier. A stereophonic demodulation circuit demodulates the output signal of the detector circuit. A high frequency signal for AM broadcast is fed to an IF amplifier by way of a second converter. Either the output signal of the IF limiter amplifier or that of the IF amplifier is applied to an AM detector circuit.

Abstract: Squelch circuitry for narrow band audio receivers which uses a sub-audible tone or coded signal to modulate the intermediate frequency in accordance with the presence of a desired broadcast signal and then detects the sub-audible tone frequency or coded signal in the modulated IF frequency to control the audio output of the receiver to an off condition when there is excessive noise.

Abstract: A multi-channel system is provided for both wide-band and narrow band low frequency transmission/reception of digital telemetry. The multi-channel system uses coherent detection having a high selectivity, and a quadrature detector having a high sensitivity. A filter is provided to average out noise. The multi-channel system oscillator is software controlled for scanning/multiplexing. The multi-channel system is used for data transmission over inductive, infrared, sonic and cable links.

Abstract: The system and method for calibrating a signal detection threshold circuit is used in a radio frequency (RF) receiver, such as a in an early warning radar (EWR) system, in which a signal detection threshold circuit rejects signals below a predetermined threshold setting and prevents noise signals from causing false alarms. The system and method include setting an initial threshold setting and receiving noise signals in one or more channels. A threshold comparison circuit rejects noise signals below the threshold setting, and a pulse repetition frequency (PRF) detection circuit detects noise pulses above the threshold setting and determines the PRF. An automatic threshold determiner and setter determines whether the PRF has reached a predetermined frequency (e.g., 400 kHz) and lowers the threshold setting until the predetermined frequency is reached. When the predetermined frequency is reached the threshold setting is stored as a noise measurement.

Abstract: A technique is used by a squelch circuit (200) that generates a fast squelch. The technique involves generating a noise signal (211) from a demodulated signal (105), generating a squelch check request (405) of one of two types, performing a release (410) of a reset control (107) in response to the squelch check request, generating an integrated noise signal (106) having essentially no decay rate from the noise signal starting at the release of the reset control, generating a result of a comparison (815, 860) of the integrated noise signal to one of two values corresponding to the one of two types of squelch check requests at an expiration of a predetermined delay started at the release of the reset control, and controlling a muting (845, 870) of a speaker (128) in response to the comparison.