Dial Tone in back ground of a live call

[Anonymous]

We have a customer that is reporting that they are randomly hearing background dial tone noise on live call.  Both parties can hear it and the caller ID shows up as the out bound caller ID.  Some time the call drops as well.  Any idea?  I thought it might be a look but this has turned nothing up.

[Anonymous]

Valtech,

Thanks for posting.  I'm going to work on the assumption that this unit is doing SIP, as opposed to MGCP, and delivering FXS lines to the customer PBX.  Please let me know if your situation is different.

This type of problem is often the result of wiring issues at the customer site or a problem on the PBX.  The problem may be on either side of the 66 block, or possibly be between the PBX and phones.  I would check the following first.

• Verify that the amphenol connection is firmly seated on the Adtran unit.
• Check the 66 block for any wiring issues such as the ends of wires getting close to neighboring contacts or bridge clips.
• Check for tightly bundled or low quality wiring at the site.
• Verify that the gain on the FXS interfaces is not excessively high.  Default setting is "rx-gain -3.0".

If none of these items reveal a problem, we are going to need to determine how to reproduce or isolate the issue.  If the customer can give you lines that had the problem, then we can attempt to duplicate the issue with a buttset connected to the 66 block.  If they are unable to give you the specific lines where the problem occurred, you may need to run a persistent debug on the unit and ask the customer to report when the problem occurs and any phone numbers involved in the call.  The following debug commands will allow us to see FXS port state changes and when dial tone is being provided on a line.

debug voice summary

debug interface fxs

debug voice toneservices

You'll want to make sure the time of day is properly synchronized on the unit so that when the customer reports a problem, our debug output will match up properly.  If decide to troubleshoot on site, feel free to call us at 888-423-8726 so that we can assist you.

Thanks!

David

[Anonymous]

Thanks David.  Yes, I should have been more specific.  It is SIP and we are handing off PRI to the customer not FXS. 

[Anonymous · Accepted solution]

Valtech,

In a SIP to PRI scenario, it is unlikely this type of problem is caused by the Adtran unit.  This is because the Adtran unit is in a purely digital mode, i.e., the audio coming in one interface and out the other interface is digital throughout.  The type of problem this customer is experiencing is often labeled as crosstalk, which I would describe as electromagnetic interference between analog pairs of wires.

The problem is most likely between the PBX and the phones, so I would look for problems with wiring between those devices.  Again, attempting to determine which lines are on the phone and which lines draw dial tone at the time of the problem will help you isolate the issue.

It is unlikely that the audio coming from the carrier has dial tone being sent in-band.  However, if you find a way to duplicate the issue, you can use our DSP audio capture feature, or get a packet capture, to determine if the inbound audio includes the dial tone.  Instructions for getting a DSP capture our shown in How to Perform a DSP Capture.

Thanks!

David

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[Anonymous]

Valtech,

I went ahead and flagged this post as "Assumed Answered".  If any of the responses on this thread assisted you, please mark them as Correct or Helpful as the case may be with the applicable buttons.  This will make them visible and help other members of the community find solutions more easily.  If you still need assistance, I would be more than happy to continue working with you on this - just let me know in a reply.

Thanks!

David

[Anonymous]

Valtech,

I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post and unmark it and select another in its place with the applicable buttons.  If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.

Thanks,

David