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Call Quality Issues FXO Loop Test Fails

Tom Lademann

Hello.  I want to see if anyone else is experienceing this issue. UC320W

This device is the second one I have had that has after a month or so of service begins to experience line quality issues. Users report

- line echo, crackling, call break up and most frequently degrading VOLUME issues.  This is all on the MAIN number which was tied to FXO4. 1-3 are much better.

1. I switched the incoming lines FXO4 and FXO1 - now the main number is clear, but the line moved to 4 is poor. Tells me something is up with the device.

2. The most recent firmware 2.3.2 has support diagnostics. THE FXO-FXS test passes on 1-3, but fails on Transmit Loss Front End (17.10!) for FXO4.  All the others test out about 5.xx for this same paramater.

I have had the TELCO out and they claim the lines are all operating fine.

Another piece of information is that I have had CISCO provide a PFM to suppress the a component of 2.3.2 which was causing my calls to come up "declined". Apparently this firmware is detecting line quality issues ... and sometimes its overagressive about it.

Overall the system is working fine ... just this line quality issue keeps coming up - customer is getting frustrated as am I. Should I be looking at a 500 series? Do they deal with these quality issues better?

3 Replies 3


Hi Tom,

It seems that you have a FXO4 hardware issue, you may want to contact small business support center to RMA the box. Did you always connect the FXO4 phone line to both UC32W boxes which had line quality issue?

Did the FXO_Overload_disable PMF fix the call declined issue? This PMF has nothing to do with line quality. It just turns off the flag in the system to not disconnect the call if overload is detected (most of the time this overload detction is a false alarm, we have a defect about it).

Best regards,


I know this is an old post but I just installed a UC320W and installed firmware 2.3.2.  I'm randomly getting a "declined" message after a call comes in and trying to pick up the call.  Is this related to the PMF issue?

If so, how should I go about fixing it?

Thank you!

Hi Jason,

Yes, we currently have a bug about it. Please install the PMF FXO_Overload_disable.pmf at Status->Devices->Alter PMFs in Configure Utility. Please remember to apply the configuration afterwards.

You can download this PMF at

Best regards,


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