[Asterisk-Users] Echo and crackle

[M.Hockings]

We are running asterisk with a single POTS line for local calls and a 
voip line for long distance.  Whenever we receive a call on the POTS 
line it is more than likely, but not always, going to have significant 
distracting echo.  In addition to that there is occasional heavy crackle 
or static.  I have tried to follow the guidelines at :
http://www.voip-info.org/wiki/view/Asterisk+echo+cancellation
but it does not seem to have made much difference.

Currently we are using a X101P for the POTS line and a TDM401B (TDM400P 
with one FXS port) for the conventional telephones.  From what I have 
read, it may help to use an FXO port on the TDM400P rather than the 
X101P for the POTS line.

What is the "conventional wisdom" about the echo in this configuration 
and what causes the crackle and how should I tackle that?  I have tried 
rebooting/power-cycling the machine to reset the hardware but it really 
hasn't noticeably helped.

Is there anything else that I can try?

Thanks,  Mike