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

Wed Jun 6 14:39:25 EDT 2007

The DSP ware in 12.4.6.XE2 is 9.2.0.   XE2 is highest in this X train also. I'm not sure all what is special in this XE train they may be using feature wise or not offhand (need to look into that). 

----- Original Message ----
From: Jason Aarons (US) <jason.aarons at us.didata.com>
To: "Linsemier, Matthew" <MLinsemier at apcapital.com>; Erick Bergquist <erickbe at yahoo.com>; ciscovoip <cisco-voip at puck.nether.net>
Sent: Saturday, June 2, 2007 5:30:26 PM
Subject: RE: [cisco-voip] Echo on IP Phone with PRI (CME)

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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