bizarre "surging" sounds on voip phones connected to 5412zl and 2910

[Lemmy Kilmister]

Hello,

We just finished a small setup of VOIP connected to a 2910 and 5412zl. Phones are Avaya 5610ip.

When you pick up the phone, you hear the dial tone, but hear a "surging". I can best describe it as a almost a cycling sound of the dial tone.

We've eliminated the POE (used an injector), checked the grounding, checked the cabling. Problem still there.

I'm pointing to something specific on HP switches because I get the same behavior on both the 5412 and the 2910.

any ideas?

[Gerhard Roets]

Hi Lemmy

Well the dial tone, is typically created by the phone. POE is DC and should not affect it in any way.

Try using a short fly lead next to the switch and see if the sound stays, it could be signal induced on the wire *skeptical*. The cable path might be something to investigate.

Are you using Shielded Twisted pair Cabling if so, is it properly earthed. Might be a good idea to get some one to measure the potential difference between shield, and the pc plugged into the phone. I am assuming you have a pc plugged into a phone. Can get kinda funky if you have a floating earth.

If you have Shielded twisted pair cable, are your patch panel and patch points rated for it, else you might end up having a huge antenna.

These are just thoughts off course. I am not really bothering with the config since this is in my opinion a more on the electrical side of things.

You might want to use that earth bonding connector at the back of the switch and do the whole earth spike thing.

HTH
Gerhard

[Lemmy Kilmister]

we figured it out..

pbx was using codec 29, we changed it to g-7-11, all good