FXO to PSTN calls - users hear noise

Unanswered Question
Jul 9th, 2009

Users hear a noise, like a machine hum (I verified) on calls via FXO to the PSTN.

I've tried the following on the voice-port

no vad

no caller-id enable (a bug a long time age :)

input gain manipulation

output attenuation manipulation

comfort noise

echo-cancel coverage manipulation

I have noted that the Router (2821) is not grounded and am having the customer take care of this. Could this be a possible cause?

Using an analog test set straight into the circuit, I do not hear the noise.

Possible dsp issue? sho dsp error shows no errors.


I have this problem too.
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