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

[Linsemier, Matthew]

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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