[cisco-voip] Echo on IP Phone with PRI (CME)

[Jason Aarons (US)]

In the past the problem is typically the phone device load, handset
volume level, or the DSP/IOS version, not a 2-wire to 4-wire conversion
as CCO might lead you to believe...

Input gain/output attenuation apply to PRIs, 7940/7960 phones have a
tone generator built in and you can measure Echo Return Loss (ERL) to
adjust the gain/attenuation.

I would open a TAC case and check the IOS/DSP firmware version first,
there have been a lot of bugs overall.

You can request your telco bring out a T-Berd or similar test tool and
prove there is no echo at the Smartjack eliminating them.

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Linsemier,
Matthew
Sent: Saturday, June 02, 2007 12:43 PM
To: Erick Bergquist; ciscovoip
Subject: Re: [cisco-voip] Echo on IP Phone with PRI (CME)

In the past any time I had issues with echo such as you describe here,
it was handled by adjusting the echo cancel coverage parameters.  From
what I understand, input gain and output attenuation commands have no
effect on a PRI circuit because it's digital (and those commands are for
analog POTS lines). 
 
I would suspect you are running into an IOS bug, a DSP resource that is
intermittently failing, or receiving echo outside of the maximum
coverage area or a telco side issue.  I would start with IOS and work up
the list from there.  You may also want to verify if the echo is lasting
the whole conversation, or just the first few seconds.  Remember that
sometimes it takes a second for the echo cancel coverage to kick in and
it can be noticable to the humar ear.  It's gotten much better since
12.4 was released. 
 
Matt

________________________________

From: cisco-voip-bounces at puck.nether.net on behalf of Erick Bergquist
Sent: Fri 6/1/2007 11:47 AM
To: ciscovoip
Subject: [cisco-voip] Echo on IP Phone with PRI (CME)



Hi,



I am having issue where users report echo on the IP phones
every now and then that lasts the whole call. The echo they hear is
their voice back on the IP Phone. The outside party does not hear echo.



The T1 PRI controller is clean, no errors and the router
network-clock is set to use the PRI.

CME is on a 2811 with IOS 12.4(6)XE2
, c2800nm-ipvoicek9-mz.124-6.XE2.bin


Have tried different echo cancel coverage settings and input/output gain
adjustments. They had no echo for almost a week then had it frequently
for 1-2 days and now it is good again for past 2 days.

voice-port 0/0/0:23

 input gain -3

 output attenuation 3

 music-threshold -45



The phones are 7941s and firmware 8.0(4)SR2 -- is it safe to try latest
firmware version on CME without IOS update?


Any ideas?



      
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