Calls dropping on fxo ports

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Sep 23rd, 2009
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I have a UC500 setup with four fxo lines which are forwarded direct to extension 201, occasionally incoming calls are dropped. It happens when the user answers the call, it connects but is then immediately dropped before they have a chance to speak. I have tried replacing the phone itself and the problem is still occuring so I don't think it's a problem with the phone hardware.


This problem is very intermittent maybe 1 in 50 calls, so i'm finding it difficult to gather debugging information. Has anyone had a similar problem before, or can anyone give me any ideas what this might be?

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Marcos Hernandez Wed, 09/23/2009 - 08:32
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A problem so infrequent is hard to troubleshoot. Nevertheless, you can verify the following:


1) Make sure wiring is correct for all four ports


2) Verify FXO port configuration and make sure it matches your Telco's (things like battery reversal, for example)


3) When you get a call drop report, take note of the dialed number and try to map it to the FXO port that handled the call (it could be that you have a bad port).


4) Check if you have any type of FXO disconnection mechanism configured. It could be that one of these is kicking in for some calls.


http://www.cisco.com/en/US/tech/tk652/tk653/technologies_tech_note09186a00800ae2d1.shtml


Thanks,


Marcos

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