Showing results for 
Search instead for 
Did you mean: 

Welcome to the Cisco Small Business Community

Have a question? Click on a topic board below to get started in the community.


FXO issue

Hi, I installed some weeks ago a UC320 system with 6 cisco IP phones (5 SPA303 and 1 SPA504G), 1 FXS, 3 FXO lines, 1 SIP line. Everything works fine, except the FXO line 1 that sometimes "freezes": on all phones it is showed like in use, the status of the line on the UC320 webpage is "in use" just nobody is using it, and it stays like this untill the UC320 is rebooted.

I finally convinced the client to pay attention about when it happens and it looks like it happens when there is an outgoing call from the SPA504G: all in a sudden the call drops and the line 1 stays "in use" even after the user of SPA504G hangs up. Client says there is no problem nor with incoming calls nor when the SPA303 phones are used.

Anybody had similar issue or has any idea?




Hi Stefano,

You may want to run impedance testing on the FXO lines to assure that they are set properly.  This should clear up any issues you are seeing on the disconnect issue.

Thank you,

Jason Nickle

Thank you Jason, I also thought it could be an impedance issue, even if i did the impedance test and set up it accordingly, but then the client told me it happens just with the SPA504G phone so I thought it couldnt be an FXO impedance-related issue otherwise it would happen also with other phones...

In any case, when i will go back to the client i will update the firmware to the new version relased today and redo the impedance test+settings and keep u informed!

Thanks for now


I promised to keep updated on this issue: it came out the problem was the power supply of the SPA504G. The universal power pack the client used for the SPA504G didnt have enough Amperes for the phone and when a 2nd or 3rd call arrived, the phone was rebooting and the line in use was staying busy because of a disconnection tone issue for which i opened another topic