finding and removing screeching sound and static on our conference phone 1

[John in Texas]

We have a NEC UNIVERGE SV8100 PBX running WebPro 9.50 (North America) and DT300 Series phones with the exception of a Polycom SoundStation 2 in our conference room. We are using a PRI T1 consisting of 24 channels. Recently during conference calls, a screeching sound (like someone scraping their fingernails across a chalk board) and static can be heard on the Polycom. It is not always present, but when it is, the screeching sound in particular is very disruptive. I changed out the Polycom with another of the same model, including swapping out it's power supply. Unfortunately, the screeching and static are still there and has gotten worse. Is this likely a problem with cabling or the SV8100 digital station interface card (CD-DLCA) going out?

 

[OzzieGeorge]

First I would change the cable pairs. Telephone cabling as a minimum has 4 wires, only 2 are needed for an analogue service so the two spare wires may be good. You could try this back at the system first to prove the issue but it is hard to hold a conference in the rooms pabxs are usually consigned to. If you have a spare outlet nearby that would be even better.

 

[fizzywig2]

John in Texas,

Not sure this will help, but years ago I had an issue with something similar through the entire switch. Lots of static and screeching noise. Turned out to be poor grounding. Re-ran the isolated ground and the issue cleared. Maybe grounding gives a place to start.

 

[John in Texas]

OzzieGeorge - Thank you for the quick post suggesting I recheck the twisted pair wiring, beginning at the system. Our wiring setup has the phone set twisted pair terminating at a 66 punch down block. A jumper twisted pair from there goes to a second 66 punch down block which is used to connect to the PBX hardware. Per your suggestion, I rechecked these wires and found the jumper wires at the first block had a tiny wire hanging between posts. When removed, the screeching and static immediately went away. Upon inspection, the hanging wire, only about 1/4" long was likely from a wire be inserted and trimmed in a post above. I suspect that a technician that trimmed a wire must of not noticed that the trimmed piece fell where it did. Ugh. I'll re-post if the screeching and static returns, but for now, with your help, it appears to be fixed. Thank you!

 

[John in Texas]

fizzywig2 - Thank you for the suggestion on checking the grounding. Was the grounding issue you found on the PBX hardware itself?

 

[fizzywig2]

John,

It was. I had the installers come back in and run a new isolated ground for the system entirely , as it kept shocking me when ever I would get close to the switch as well and the static noise and screeching complaints throughout the site. I have also had water get in the buried conduit before that make odd noises. It has been a while back, so I am just throwing some ideas your way.

 

[John in Texas]

Thanks fizzywig2 for the explanation. I appreciate you reaching out and sharing the information.