Abstract: A sign-based decorrelation detection and adaptive control arrangement includes structure for detecting cross-correlation between a far-end signal and an echo residual following a balance filter. During the adaptive process, if the detected correlation value is below a certain threshold, indicating that the two signals are decorrelated, the adaptation of the balancing filter is stopped. At such a point, proper echo cancellation has been achieved. Conversely, when the detected correlation value exceeds a threshold, the adaptation is ,continued until the correlation value falls below the threshold again. In any event, such decorrelation controllers are able to detect signal decorrelation and to control adaptation even in the presence of a double-talker condition.

Abstract: The preferred embodiment of the apparatus comprises a first signal level detector which receives the communications signal as an input and generates a detection signal as an output, a second signal level detector which receives the detection signal as an input and generates a noise detection signal as an output, and a comparing circuit which compares the detection signal and the noise detection signal and produces a speech burst detection signal. Each of the signal level detectors comprises a digital low pass filter having an input and an output which employs a comparator for comparing current samples of signals at the input with previous samples of signals at the output and generating a representative comparator output. Each low pass filter includes circuitry for establishing an attack time and a decay time, in response to the comparator output.

Abstract: An apparatus for effecting echo suppression facilitating communications between an analog device and a digital device comprising a transmit circuit for processing outgoing signals, a receive circuit for processing incoming signals, and a control circuit for controlling the transmit circuit and the receive circuit. The transmit circuit includes transmit attenuators for attenuating the outgoing signals as they pass through the transmit circuit, and an analog-to-digital conversion circuit for converting analog signals to digital signals. The receive circuit includes receive attenuators for attenuating the incoming signals as they pass through the receive circuit and a digital-to-analog conversion circuit for converting digital signals to analog signals. Each of the transmit attenuators and the receive attenuators is digitally adjustable by the control circuit.

Abstract: A method for operating an apparatus for facilitating communications between an analog device and a digital device, which apparatus includes a plurality of signal processing circuits and a control circuit for controlling the signal processing circuits. Each of the signal processing circuits includes signal attenuators and signal burst discrimination circuitry. The apparatus is operable in a plurality of stable states, preferably in an idle stable state, a transmit stable state, and a receive stable state. The apparatus also is operable in a plurality of transitional states, including up-transition states and down-transition states.