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<DIV dir=ltr align=left><SPAN class=300011515-01092010><FONT face=Arial
color=#0000ff size=2>Thanks again, Wes.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=300011515-01092010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=300011515-01092010><FONT face=Arial
color=#0000ff size=2>I see you mentioned SLIPS, and I had seen that as a
possible cause, but there are zero, so I had ruled that out. Should have
had that in my little list, though.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=300011515-01092010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=300011515-01092010><FONT face=Arial
color=#0000ff size=2>I've certainly got more to go on now, and I can see
this last doc you referenced. (I'm not a Partner, so I was "forbidden"
some of the other docs you linked me to.) Crappy part is the echo is
intermittent--of course--so all I can really do is make a change then wait and
see. I've sent a number of calls out that circuit to test myself, and I've
not heard any echo.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=300011515-01092010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=300011515-01092010><FONT face=Arial
color=#0000ff size=2>jeff</FONT></SPAN></DIV><BR>
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<FONT face=Tahoma size=2><B>From:</B> Wes Sisk [mailto:wsisk@cisco.com]
<BR><B>Sent:</B> Wednesday, September 01, 2010 9:54 AM<BR><B>To:</B> Jeff
Ruttman<BR><B>Cc:</B> Cisco VOIP<BR><B>Subject:</B> Re: [cisco-voip] Echo
Cancellation and 7911 Phone Loads<BR></FONT><BR></DIV>
<DIV></DIV>Hi Jeff,<BR><BR>Inline, ws.<BR><BR>Jeff Ruttman wrote:
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<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>Thanks Wes. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>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.</FONT></SPAN></DIV></BLOCKQUOTE>ws: echo is generated too far from the
ipphone, like at the the other endpoint. If you call me and hear your own voice
then most likely the echo is being generated in my phone. Your gateway is
closest to me so will have the best chance of canceling the echo as the original
signal and echo signal are closest in time in your network at the gateway.
But, in the end, it really is a problem with my customer premise equipment
(CPE). I should be canceling the echo. The best place to fix it is in my
network. Next best is in the carrier, next is in your CPE.<BR>
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<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>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.</FONT></SPAN></DIV></BLOCKQUOTE>ws:
Yes, there is tuning on the gateway to get the most out of the available ecans.
If the echo is coming back within the cancellation coverage then you just need
to get levels and ERL in line so the ecans can do their jobs.<BR>
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<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>So in a VOIP system that has echo, I
can:</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>1. Bug the telco</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>2. Expand echo cancellation on the GW</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>3. Attenuation/gain statements on
GW</FONT></SPAN></DIV></BLOCKQUOTE>There are several parameters on gateways for
possible tuning. These include:<BR>ecan coverage<BR>NLP - non linear
processor<BR>ERL - echo return loss - primarily affected by Input Gain and
Output Attenuation<BR>Noise - any noise introduced on the circuit causes the
echo signal to not match the original signal. This prevents echo from being
detected and canceled. Examples of noise include any slips or errors on
T1's and electrical cables (60Hz, fluorescent lights especially) located too
close to analog (FXS/FXO) connections. I believe the parameters are
covered pretty well here:<BR><A class=moz-txt-link-freetext
href="http://www.cisco.com/en/US/customer/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml">http://www.cisco.com/en/US/customer/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml</A><BR>
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<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>4. Change phone load</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>At least so far that's all I've found I can tinker
with. Is that about it?</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>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.</FONT></SPAN></DIV></BLOCKQUOTE>ws: see the article above. Use IG and
OA to get ERL that works for ECAN.<BR>
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<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>Thanks</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010><FONT face=Arial
color=#0000ff size=2>jeff</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=263310719-31082010></SPAN> </DIV><BR>
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<FONT face=Tahoma size=2><B>From:</B> Wes Sisk [<A class=moz-txt-link-freetext
href="mailto:wsisk@cisco.com">mailto:wsisk@cisco.com</A>] <BR><B>Sent:</B>
Tuesday, August 31, 2010 2:00 PM<BR><B>To:</B> Jeff Ruttman<BR><B>Cc:</B>
Cisco VOIP<BR><B>Subject:</B> Re: [cisco-voip] Echo Cancellation and 7911
Phone Loads<BR></FONT><BR></DIV>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.<BR><BR>Otherwise, AFAIK, all cisco phones (except soft) have
local ecan to prevent speaker audio from going back into mic.<BR><BR><BR><A
class=moz-txt-link-freetext
href="http://www.voiptroubleshooter.com/problems/echo.html"
moz-do-not-send="true">http://www.voiptroubleshooter.com/problems/echo.html</A><BR><A
class=moz-txt-link-freetext
href="http://www.cisco.com/en/US/partner/docs/ios/solutions_docs/voip_solutions/EA_ISD.html"
moz-do-not-send="true">http://www.cisco.com/en/US/partner/docs/ios/solutions_docs/voip_solutions/EA_ISD.html</A><BR><A
class=moz-txt-link-freetext
href="http://www.cisco.com/en/US/partner/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml"
moz-do-not-send="true">http://www.cisco.com/en/US/partner/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml</A><BR><BR>/Wes<BR><BR>Jeff
Ruttman wrote:
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<DIV><SPAN class=997510914-31082010><FONT face=Arial
size=2>Greetings,</FONT></SPAN></DIV>
<DIV><SPAN class=997510914-31082010></SPAN> </DIV>
<DIV><SPAN class=997510914-31082010><FONT face=Arial size=2>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.</FONT></SPAN></DIV>
<DIV><SPAN class=997510914-31082010></SPAN> </DIV>
<DIV><SPAN class=997510914-31082010><FONT face=Arial size=2>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.</FONT></SPAN></DIV>
<DIV><SPAN class=997510914-31082010></SPAN> </DIV>
<DIV><SPAN class=997510914-31082010><FONT face=Arial size=2>Any
insight?</FONT></SPAN></DIV>
<DIV><SPAN class=997510914-31082010></SPAN> </DIV>
<DIV><SPAN class=997510914-31082010><FONT face=Arial
size=2>Thanks</FONT></SPAN></DIV>
<DIV><SPAN class=997510914-31082010><FONT face=Arial
size=2>jeff</FONT></SPAN></DIV><PRE wrap=""><HR width="90%" SIZE=4>
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