Abstract: An acoustic delay measurement apparatus measures an audio delay introduced by an audio system. A programmable delay buffer, which introduces a programmable delay into the audio stream, receives an audio stream from an audio source and outputs a reference signal representing the audio stream. An adaptive filter is responsive to the reference signal to generate an estimate signal to match on convergence of the adaptive filter an audio signal output by the audio system, which is the audio stream delayed by an amount representative of the audio delay introduced by the audio system. A processor including a coefficient analysis block reads coefficients in the adaptive filter after convergence, computes a delay introduced into said estimate signal by the adaptive filter, and adds the computed delay to the programmable delay buffer to provide a measurement of the audio delay.

Abstract: A method for canceling acoustic far-end audio echo content includes high-pass filtering audio content received from a far end and playing the high-pass filtered audio content through a speaker, examining audio content captured by a microphone to detect the presence of audio content in a low-frequency sub band after subtracting high-pass filtered audio content from the audio content captured by the microphone using a least mean square (LMS) adaptive filter. If audio content in a low-frequency sub band is detected in the audio content captured by the microphone, freezing adaptation of the LMS filter and sending to the far end the audio content captured by the microphone after subtracting, and if audio content in a low-frequency sub band is not detected in the audio content captured by the microphone, enabling adaptation of the LMS filter and sending to the far end the audio content captured by the microphone after subtracting.

Abstract: A reference circuit constituted of: a voltage/current bias circuitry; a first transistor coupled between a common voltage and an first bias circuitry output; a second transistor coupled between the common voltage and a second bias circuitry output; a third transistor coupled between the common voltage and an output providing a temperature and supply invariant current; a resistor coupled between the second transistor and the second output of the bias circuitry; and an output providing a temperature and supply invariant voltage coupled between the resistor and the second transistor, the voltage output terminal further coupled to a gate of the third transistor, wherein the bias circuitry is arranged, in cooperation with the first transistor, to generate a first current at the first output thereof, and, in cooperation with the second transistor, to generate a second current at the second output thereof, the current magnitudes exhibiting a ratio of a predetermined value.

Abstract: A reference circuit constituted of: a voltage/current bias circuitry; a first transistor coupled between a common voltage and an first bias circuitry output; a second transistor coupled between the common voltage and a second bias circuitry output; a third transistor coupled between the common voltage and an output providing a temperature and supply invariant current; a resistor coupled between the second transistor and the second output of the bias circuitry; and an output providing a temperature and supply invariant voltage coupled between the resistor and the second transistor, the voltage output terminal further coupled to a gate of the third transistor, wherein the bias circuitry is arranged, in cooperation with the first transistor, to generate a first current at the first output thereof, and, in cooperation with the second transistor, to generate a second current at the second output thereof, the current magnitudes exhibiting a ratio of a predetermined value.

Abstract: An acoustic delay measurement apparatus measures an audio delay introduced by an audio system. A programmable delay buffer, which introduces a programmable delay into the audio stream, receives an audio stream from an audio source and outputs a reference signal representing the audio stream. An adaptive filter is responsive to the reference signal to generate an estimate signal to match on convergence of the adaptive filter an audio signal output by the audio system, which is the audio stream delayed by an amount representative of the audio delay introduced by the audio system. A processor including a coefficient analysis block reads coefficients in the adaptive filter after convergence, computes a delay introduced into said estimate signal by the adaptive filter, and adds the computed delay to the programmable delay buffer to provide a measurement of the audio delay.

Abstract: A full duplex voice communication method constituted of: estimating an acoustic echo within a near-end signal; cancelling the estimated acoustic echo; detecting whether, or not, a change has occurred in a near-end acoustic echo path, the received near-end signal represents speech and the received far-end signal represents silence, wherein, responsive to the results thereof, the method is further constituted of: alternately attenuating frequency components of the echo cancelled near-end signal by a first frequency domain attenuation value and by a second greater frequency domain attenuation value; alternately attenuating a first function of the frequency component attenuated echo cancelled near-end signal by a first switchable attenuation value and by a second greater switchable attenuation value; and alternately attenuating a second function of the received far-end signal by a third switchable attenuation value and by a fourth greater switchable attenuation value.

Abstract: A comfort noise generation apparatus constituted of: near and far end speech detectors arranged to detect speech activity in near-end and far-end signals and a comfort noise generator, wherein responsive to an indication from the near-end speech detector that speech activity is absent on the near-end signal and an indication from the far-end silence detector that speech activity is absent on the far-end signal, the comfort noise generator is arranged to initiate a determination of an estimation of near-end background noise, wherein responsive to an indication from the near-end speech detector that speech activity is present on the near-end signal or an indication from the far-end silence detector that speech activity is present on the far-end signal, the comfort noise generator is arranged to terminate the estimation determination of near-end background noise, and wherein the comfort noise generator is arranged to output a function of the near-end background noise estimation.

Abstract: An acoustic echo path change detection apparatus constituted of: a time domain path change detection functionality arranged to: detect a change in a near-end acoustic echo path responsive to a time domain analysis of a near-end signal and a signal output by an acoustic echo canceller; and output an indication of the detected change, a frequency domain path change detection functionality arranged to: detect a change in the near-end acoustic echo path responsive to a frequency domain analysis of a far-end signal and the signal output by the acoustic echo canceller; and output an indication of the detected change, and a combination path change detection functionality arranged to: determine a first function of the output indication of the time domain path change detection functionality and the output indication of the frequency domain path change detection functionality; and output the determined first function.

Abstract: A glass breakage detection method, constituted of: receiving a plurality of audio samples; estimating low frequency power values of the received plurality of audio samples; estimating wide band power values of the received plurality of audio samples; responsive to the estimated wide band power values, determining an amplification value; responsive to the estimated low frequency power being greater than a predetermined threshold, amplifying a function of the received plurality of audio samples by the determined amplification value; comparing the amplified function with a predetermined function of sound of breaking glass; and outputting an indication of the comparison.

Abstract: An audible alarm detector constituted of: a microphone generating an electronic signal from an audible signal; a phase locked loop locking onto a frequency component present in the generated electronic signal to output a demodulated signal; and a pattern detector for comparing the demodulated signal against each template of a known set of templates, each template representing a standard pulse stream, wherein upon detection that the demodulated signal matches one of the known templates, the audible alarm detector is arranged to output an alarm detected signal indicating a presence of one of the standard pulse streams.

Abstract: A voltage regulator includes a switch coupled between an input voltage terminal and an energy storage element, a first output capacitor coupled to a first node defined between the switch and the energy storage element, the first capacitor being coupled to a first output voltage terminal, a charge pump circuit coupled to the first node and comprising a second output capacitor coupled between a second output voltage terminal and the first output voltage terminal, and a controller operable to selectively enable the switch to control voltages generated at the first and second output terminals.

Abstract: A device includes a plurality of subscriber line interface circuits and a shared protection device. Each subscriber line interface circuit has a voltage input terminal and first and second interface line terminals. The shared protection device is coupled to the interface line terminals and operable to sense a negative reference voltage representing a most negative one of the voltages present on the voltage input terminals and to provide overvoltage protection responsive to a voltage on at least one of the interface line terminals exceeding the negative reference voltage.

Abstract: A gateway includes at least one network interface, at least one analog telephony interface, and a processing unit operable to receive a bandwidth signal over the at least one analog telephony interface from a telephony device and configure an audio bandwidth of a telephony connection for the telephony device over the at least one network interface based on the bandwidth signal.

Abstract: A line card includes a plurality of subscriber line interface circuits, a plurality of interface lines, and a first overvoltage protector. The subscriber line interface circuits each have a first input terminal operable to receive power at a first positive reference voltage. The interface lines are each coupled to one of the subscriber line interface circuits for interfacing with subscriber lines external to the line card. The first overvoltage protector is coupled to the interface lines and referenced to the first positive reference voltage to provide overvoltage protection responsive to a voltage on at least one of the interface lines exceeding the first positive reference voltage.

Abstract: A line card includes a subscriber line interface circuit, an interface line, and a first overvoltage protector. The subscriber line interface circuit has a first input terminal operable to receive power at a first reference voltage. The interface line is coupled to the subscriber line interface circuit for interfacing with a subscriber line external to the line card. The first overvoltage protector is coupled to the interface line and referenced to the first reference voltage to provide overvoltage protection responsive to a voltage on the interface line exceeding the first reference voltage by a first predetermined threshold.

Abstract: A method for scheduling ringing signals for a plurality of subscriber lines includes maintaining a schedule of ringing signals for the plurality of subscriber lines. A plurality of ringing counts is determined. Each ringing count specifies a number of subscriber lines ringing at a selected point in the schedule. A ringing request for a particular subscriber line is received. A position in the schedule for the ringing request is identified based on the ringing counts that does not exceed a maximum ringing limit. The ringing request is scheduled in the schedule responsive to identifying the position. A ringing signal is generated for the particular subscriber line in accordance with the schedule.

Abstract: A method for controlling power dissipated in a subscriber line interface circuit includes measuring a power parameter of the subscriber line interface circuit during a ringing cycle, comparing the measured power parameter to a target power parameter and adjusting at least one ringing parameter of a ringing signal generated by the subscriber line interface circuit based on the comparison. A line card includes a subscriber line interface circuit operable to generate a ringing signal, and a subscriber line audio-processing circuit operable to measure a power parameter of the subscriber line interface circuit during a ringing cycle, compare the measured power parameter to a target power parameter, and adjust at least one ringing parameter of the ringing signal based on the comparison.

Abstract: A method and apparatus is provided for ring-trip detection in a line card having an analog-to-digital converter for processing voice signals. The method includes receiving a ringing control signal, transmitting a ringing signal to a subscriber line in response to the ringing control signal, and receiving a portion of the ringing signal from the subscriber line. The method includes converting the portion of the ringing signal to a digital signal using the analog-to-digital converter, and providing a ring-trip indication in response to the digital signal. The apparatus includes first circuitry capable of processing a voice signal, the circuitry including a analog-to-digital converter for processing the voice signal. The apparatus includes a ringing generator, second circuitry, and ring-trip detection logic. The generator is capable providing a ringing signal to a subscriber line in response to receiving a ringing control signal.

Abstract: A method for providing a ringing signal includes providing a plurality of batteries coupled to a subscriber line interface circuit operable to generate the ringing signal during a ringing cycle and switching selected batteries during the ringing cycle based on values of the ringing signal during the ringing cycle. A line card includes a subscriber line audio-processing circuit operable to generate values for a ringing signal during a ringing cycle, a subscriber line interface circuit coupled to the subscriber line audio-processing circuit and operable to drive the ringing signal on a subscriber line based on the generated values, a plurality of batteries coupled to a subscriber line interface circuit and a control unit operable to switch selected batteries during the ringing cycle based on the generated values of the ringing signal.

Abstract: A method for controlling a ringing signal includes generating a ringing signal on a subscriber line, detecting a condition indicative of the subscriber line going off-hook and reducing an amplitude of the ringing signal responsive to detecting the condition. A line card includes a subscriber line interface circuit operable to generate a ringing signal on a subscriber line and a subscriber line audio-processing circuit operable to detect a condition indicative of the subscriber line going off-hook and reducing an amplitude of the ringing signal responsive to detecting the condition.