Patent ID: 8923508

Claim:
A speakerphone comprising: a transmit path having variable gain; a receive path having variable gain; a first level detector coupled to the transmit path for generating a level of the signals in the transmit path; a second level detector coupled to the receive path for generating a level of the signals in the receive path; a first differentiator coupled to the first level detector for determining a rate of change in the level of the signals in the transmit path; a second differentiator coupled to the second level detector for determining a rate of change in the level of the signals in the receive path; an adaptive echo canceler coupled to the transmit path for at least partially removing from the transmit path acoustically-coupled signals from the receive path; and a controller, responsive to the first and second level detectors and the first and second differentiators, is adapted to increase the gain of the transmit path and decrease the gain of the receive path when the level of the signals in the transmit path exceed the level of the signals in the receive path, and is adapted to decrease the gain of the transmit path and increase the gain of the receive path when the level of the signals in the receive path exceed the level of the signals in the transmit path; wherein the controller is further adapted to enable adaptation by the adaptive echo canceler when the rate of change in the level of the signals in the transmit path exceeds the rate of change in the level of the signals in the receive path by a hysteresis amount, and the controller is further adapted to disable adaptation by the adaptive echo canceler when the rate of change in the level of the signals in the transmit path exceeds the rate of change in the level of the signals in the receive path by the hysteresis amount.