[Asterisk-Users] Echo Canceling

[Andrew Kohlsmith]

On Wednesday 05 October 2005 12:22, Rich Adamson wrote:
> Identifying why a echo cancel tone is occurring on a normal voice call
> is reasonable, but why would a _local_ echo canceller be needed on a
> four-wire full-duplex digital link?

It's to cancel far-end echo which is occuring on the terminating side of the 
call (since my end is PRI in and 4-wire right up to the KSU).

Admittedly it's not an ideal situation but the normal echo you'd receive is 
exacerbated because of the delays introduced by bringing the call in to a PC.  
Ideally the echo canceller should be wherever the call is converted from 
4-wire to 2-wire (i.e. at the terminating telco's FXO rack, if my terminology 
is correct.)

-A.