CME Hum on Line and buzz when talking.

Rick Morris · ‎05-01-2008

CME Config with FXO

when grabbing a line, 9.1 if you turn the volume up you get hum on the line.

on one of the FXO's you get a crackle and a buzz when talking.

Had a tech check all the lines before they tie into the router and everything works ok. Also, replaced the FXO card too.

any settings I can check to correct this issue?

paolo bevilacqua · ‎05-01-2008

Hi, please follow accurately the "THL sweep" method described in the following link, to find the most appropriate impedance settings for your lines:

http://www.cisco.com/en/US/tech/tk652/tk701/technologies_tech_note09186a0080477a06.shtml

Hope this helps, please rate post if it does!

Rick Morris · ‎05-02-2008

Thank you for the link.

I did the sweeps, little time consuming but went through each impedence level. Nothing helped.

I did the verberose sweep and it kept failing at the first test. I saw a note at the bottom of the link that discusses HC mode, but do not understand what that meant.

Does anyone know of a filter that is inline that can be used to clean up the line before it enters in the FXO?

paolo bevilacqua · ‎05-02-2008

If you tried all the values, even if manually, and no change, that's bad obviously.

There are no filters that you can use. Try placing a quality phone on the line and if you can hear the noise with that, call the telco back.

On the other hand if you want pindrop quality without possibility of any trouble, get ISDN BRI.

Charles Hill · ‎05-10-2008

Has your problem been resolved? If so what was the resolution?

If not, I would determine which trunk/fxo port has the buzz or if it is isolated to one port. Then move telephone line to a different fxo port and see if the trouble follows the line or stays with the fxo port.

Rick Morris · ‎05-12-2008

the issue has not been resolved.

Trouble stays on the FXO port and not the phone line. No matter what line is in there the trouble remains the same. I have been able to changes some settings, output and input but it has not really made a difference. We have changed the FXO card, but nothing has solved the issue. I am now looking at a ISDN BRI

gglynn · ‎05-15-2008

Since you've swapped out the FXO card entirely and have tried multiple lines you know are not noisy, then it sounds to me like it could be a bad DSP on a PVDM module in the ISR.