Echo-Canceller Protocol Within a Digital Telephone Network
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
A (caller party) dials the LA tie line through the SW (A) PBX, and then dials the B extension number. The processor K(A) transmits the dialed digits, through the CH (A) - CH (B) link, to the K(B) processor. When K(A) has received the last digit, information is sent from K(A) to selected voice terminal processor equipment (VUA) which compresses the voice signal. When receiving this information, the VUA sends a training sequence to party A, then gets back the filtered sequences, and derives the echo canceller (A) initial tap values therefrom. During this initialization, which takes between 100 and 200 milliseconds (depending on the echo path maximum duration 16 to 32 ms), neither the analysis nor the synthesis is activated within the voice processor's VUAs.