Patent ID: 6665401
Filing Date: 2003-12-16
Classification: H04M

Abstract:
A method for canceling echo, comprising:setting a threshold value signal to a preset value, wherein the threshold value signal and a medium value signal are kept at a level of the preset value; diagnosing whether a difference between an echo signal (I) and the medium value signal (I-1) is more than a positive threshold value and whether the difference between the echo signal (I) and the medium value signal (I-1) is less than a negative threshold value; and increasing a level of the medium value signal (I) when a difference between an echo signal (I) and the medium value signal (I-1) is more than the positive threshold value by a upraise speed and increasing the level of the threshold value signal (I) by a first speed faster than the upraise speed; determining the level of the threshold value signal (I) when a difference between the echo signal (I) and the medium value signal (I-1) is less than the negative threshold value, decreasing the level of the medium value signal (I) by a drop speed and decreasing the level of the threshold value signal (I) by a second speed faster than the drop speed; wherein the difference between the echo signal (I) and the medium value signal (I-1) is not more than the positive threshold value and the difference between the echo signal (I) and the medium value signal (I-1) is not less than the negative threshold value, which represents the level of the echo signal (I) in an normal range without adjusting the threshold value; and wherein the symbol (I) represents a present condition of a corresponding signal and the symbol (I-1) represents a previous condition of a corresponding signal.