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: An apparatus for controlling the magnitude of a metering signal used in a communication system includes a high pass filter and a threshold detector. The apparatus is preferably integrated on to a subscriber line audio-processing circuit (SLAC device) which is used on a line card. The device is operable with either 12 kHz of 16 kHz metering signals. The high pass filter preferably includes a shift register and an adder. The level detector preferably includes a shift register, an OR gate and an AND gate. The device preferably is utilized to reduce the echo or reflection caused by the variable impedance of subscriber lines in telephone communication systems.