FXO Port Testing

[Phil Bradley]

Hello All. I am testing a 2911 router with a VIC2-4FXO module and have ran into issues with the THL Tone Sweep test method. When it gets to the 900R ohm setting it fails with ERL very low. I then use the test voice port 0/1/0 inject-tone local sweep 200 0 0 manual method and my ERL results stay close to the same no matter what impedance value that I choose. I am using CUCM 8.6 with the 2911 as my gateway. I go into the FXO port in CUCM and change the impedance value and the issue the apply command on each value change. Am I doing something wrong? I would expect when I set the impedance to 900 real my ERL values would be low with the manual method like it was with the tone sweep method but there not. Suggestions?

[paolo bevilacqua]

Leave the default cptone setting for the country, and worry again only if there is a demosntrated problem.

[Phil Bradley]

Hello Paolo. This has nothing to do with the cptone setting for the port. What I am trying to do is match the impedance of the TELCO provider on the FXO PORT using the impedance command under the port. The first step I was trying to accomplish was issuing the the command test voice port 0/1/0 thl-sweep verbose. This produced an error that ERL was to low and stopped the sweep at the 900 Real ohm setting. I then proceeded to use the command test voice port 0/1/0 inject-tone local sweep 200 0 0 to do a manual tone injection with the port impedance set to 900 real ohms and this produced an ERL of over 50 on average. The thl-sweep failed with ERL to low at an average of 5 so why isn't the ERL on the thl-sweep method around 5 also instead of over 50?

[tonypearce1]

I'm having this same problem with my 2901.

[christopher.ryan.fpfg]

I have found the same when doing testing and not bouncing the FXO port between different impedance manual tests. I also found documenation from Cisco (Source Below) that states the FXO port you are testing should be bounced between every impedance test. Go ahead and try that, for anyone having the same issue. The document has lots of great tips and explanations.

"Original Tone Sweep Method

Cisco IOS Software Release 12.3(11)T introduced the Original Tone Sweep method of determination of the best match impedance. The method is also available in Cisco IOS Software Releases 12.3(14)T, 12.4(1), and later.  The method requires some manual work by the tester to complete the suite of tone tests.  Specifically, you must manually change the impedance setting under the voice port for each new battery of tone tests. You administratively issue the shutdown command and the no shutdown command on the voice port to have the change take effect. Then, you place a new test call from the FXO/FXS/DID voice port and execute the battery of tone tests again.  You repeat the process for each different impedance setting that the voice port allows."

Source: https://www.cisco.com/c/en/us/support/docs/voice/ip-telephony-voice-over-ip-voip/64282-impedance-choice.html