Voice Port Echo

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On a Cisco 2851 router / Call Manager Express, we have our T1 Voice
line set as follows:

 In Gain is Set to 0 dB
 Out Attenuation is Set to 0 dB
 Echo Cancellation is enabled
 Echo Cancellation NLP mute is disabled
 Echo Cancellation NLP threshold is -21 dB
 Echo Cancel Coverage is set to 64 ms
 Echo Cancel worst case ERL is set to 6 dB

We are getting a lot of echo on calls to external analog phones.

We have tried different settings on the ERL, Echo Cancel Coverage,
Input Gain and Output Attenuation. So far nothing works to diminish the
echo. Cisco IOS version is 12.3(11).

Please advise. Thank you.


Re: Voice Port Echo
Read up on how echo is formed. Its either feedback from the handset,
where gain adjustments help minimise the 'applitude' of the echo - and
the echo problem is therefore at how the remote end is setup (ie echo
on one end ?) -  the router can only do so much, but maybe you tweaking
the end where the echo is ? instead of remote end ?

The real killer is analog to digital points in the network. Like where
you may have an E&M card to PABX ?


Re: Voice Port Echo

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This is your problem.

You need 6 dB of separation.

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Try this:

Output-gain -3 dB
Input Attenuation 3dB
Echo Cancel Coverage 64



Jonathan


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