[cisco-voip] Echo Cancellation and 7911 Phone Loads

[Jeff Ruttman]

Thanks Wes.  
 
Well I've expanded echo cancellation on the gateway.  (PRI with MGCP,
CCM6.1)  So your first paragraph is saying that most likely echo is
generated too "far away" (too much delay) from my GW to cancel the tail
end echo coming into our system--even with my expanded echo cancellation
in place.  So only the telco might have a chance of cancelling that echo
"closer to" the echo source.
 
As I understand it, I might also change phone loads (hence my question
about 7911s).  And I might try some gain/attenuation settings on the GW
as well--or so I've read.
 
So in a VOIP system that has echo, I can:
 
1. Bug the telco
2. Expand echo cancellation on the GW
3. Attenuation/gain statements on GW
4. Change phone load
 
At least so far that's all I've found I can tinker with.  Is that about
it?
 
Anyone use attenuation or gain statements on their GWs?  I know the
statements, but I don't know what their function really is, whether I
would use one or the other or both, or what I would set them to.
 
Thanks
jeff
 
 

________________________________

From: Wes Sisk [mailto:wsisk at cisco.com] 
Sent: Tuesday, August 31, 2010 2:00 PM
To: Jeff Ruttman
Cc: Cisco VOIP
Subject: Re: [cisco-voip] Echo Cancellation and 7911 Phone Loads


Talker echo is usually caused by echo at far end tail circuit.  With
VOIP that delay is going to be too long for the talker's phone to
cancel.  It will have to canceled closer to the source of the echo.

Otherwise, AFAIK, all cisco phones (except soft) have local ecan to
prevent speaker audio from going back into mic.


http://www.voiptroubleshooter.com/problems/echo.html
http://www.cisco.com/en/US/partner/docs/ios/solutions_docs/voip_solution
s/EA_ISD.html
http://www.cisco.com/en/US/partner/tech/tk652/tk698/technologies_tech_no
te09186a0080149a1f.shtml

/Wes

Jeff Ruttman wrote: 

	Greetings,
	 
	Can someone confirm or deny my memory?  I recall reading that
phone loads for 7911 phones don't really contain echo cancellation
programming.  In looking now, I can't find much info on echo
cancellation in relation to different phone models/loads in general and
nothing on 7911s.
	 
	We have an office mostly full of 7911s recently complaining of
talker echo.  There are loads out on cisco.com newer than the ones we're
using, and while it's not hard to change phone loads, it would be
pointless to do it if the phone loads don't contain echo cancellation.
	 
	Any insight?
	 
	Thanks
	jeff
	
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