[Asterisk-Users] Echo on a PRI

[George Pajari]

> I am getting an occasional noticeable echo on some of the phone lines
> (random inbound and outbound).  Everyone I ask keeps telling me that I
> can't be having echo since I am on a PRI, which is a digital circuit.
> Ok, so I can't be having echo, but I am!
> Does anyone have any ideas of what might be
> causing the echo in this situation?

There are many far more knowledgeable than I about echo but in the interim I
will contribute from my limited understanding.

While echo will not be generated at the interface between your Asterisk
server and the PRI trunk, echo still can be generated elsewhere in the
network (i.e. at the other end of the call where your "digital" call is
converted into analog to interface with the two copper wires running to the
POTS phone).

Normally end-to-end latency for local calls is so short that the echo
appears (if it appears at all) as reverb rather than echo. The problem is
that if you are running VoIP calls through your Asterisk box you can
introduce enough latency so that the echo already present in the system
becomes noticeable.

Hence the need to enable echo cancelling.

Read the wiki and play with the parameters and #defines in the echo can
code.

Good luck!

George Pajari
netVOICE communications