[Asterisk-Users] Question on echo's for Canadian Asterisk users ...

[Andrew Kohlsmith]

On Saturday 04 September 2004 16:57, paul at freestylenetworks.com wrote:
> Has anyone has issues with echo using a Wildcard with a PRI from a
> major Canadian Telco? (Bell, Telus, AllStream, Sprint, Group Telecom).

I have a PRI with Bell Canada in Listowel, ON  (519-291-XXXX).

I have echo on some calls but not all -- it doesn't seem to have anything to 
do with what switch it's terminating on.  Calling anywhere in Fordwich echos 
rather badly as do some Toronto numbers.  The echo occurs on incoming and 
outgoing calls.  (we only call out on the PRI for local, 800 and fax 
numbers).

> We are using a T1 from GT that is giving use annoying echos whenever a
> SIP/IAX2 client calls a
> local analog line. Calling cells phones is no issue since its digital.
> Regardless, there should
> be no issue with echo on a PRI at all.

All that PRI gives you is one less hybrid in the circuit.  That's it.

> NOC at GT is telling us that there is no echo cancellation enabled on
> this PRI. 'Talk to your rep' was the response I got ....
> To me that’s crap, because they shouldn’t be selling PRI's without
> this essential feature.

Depending on who you talk to you will hear responses like
1. "I have no idea what you're talking about."
2. "We don't have echo cancellation hardware available on any PRI."
3. "You must specifically provision the PRI with echo cancellation."

I've found acceptable echo cancellation on the PRI with Asterisk's echo 
cancellation software on the TE405P with the following:

- agressive cancellation
echocancel=yes
echocancelwhenbridged=yes
echotraining=500

No need to worry about the echo canceller killing fax/data connections since 
just like the real echo cancellation hardware, asterisk will disable the echo 
cancel routines when it hears the correct disable tone on the line.  You'll 
see something like "zaptel Disabled echo canceller because of tone (tx) on 
channel 13".

We were really having a lot of echo troubles but 20040831 CVS HEAD seems to 
have really helped, although it was certainly acceptable with 20040806 CVS 
HEAD.

I haven't been able to locate a good hardware echo canceller on ebay yet (I 
keep missing the auctions).  :-)

-A.