Intermittent Static across idle phone's speakers

[1234567sk]

NEC SV9100 CP20 phone system has been installed for a year. Replaced a Toshiba that had no issues but was old. The phones are all digital and the lines are analog from Comcast. The customer has complained from day one about intermittent static coming across the phones intermittently. It could be a day or a week but there is a burst of static across an idle phone’s speaker. It appears to be all the phones. It happens any time of day and has happened after hours when only the customer contact was there.
Power was isolated on a dual conversion battery backup and the system was grounded as it previously was not. All parts have been replaced 1 by 1 including the 19” chassis and main cpu. None of this has fixed the issue. All the original parts are back in. NEC thinks it is noise coming in on the cables. I have eliminated 5 of the 20+ phones but the issue continues. I would hate to have to rewire and find out that isn’t the problem.
Any ideas?

 

[flaphat]

You can try replacing the power cord/pack and power strip if any that are connected to the phone system. If there are any broadcasting station or antenna/large dish in the area, this can cause the issue also. Maybe a company in the area that uses CB radio?

 

[1234567sk]

Any possible power issue was eliminated with the double conversion battery backup. There is that new Comcast wireless backup coming off the modem within 8 ft but this is typical for many of our sites. CB is always unknown. I'm thinking of putting on my tin hat and building a Faraday cage.

 

[CoralTech]

Have you checked to see if the phone's background music is on?

 

[1234567sk]

Checked Extension information in PcPro and all extension's BGM are disabled. Yes, I have heard of that issue with BGM before. Thank You

 

[vitld]

NEC SV9100 CP20 phone system has been installed for a year. Replaced a Toshiba that had no issues but was old. The phones are all digital and the lines are analog from Comcast. The customer has complained from day one about intermittent static coming across the phones intermittently. It could be a day or a week but there is a burst of static across an idle phone’s speaker. It appears to be all the phones. It happens any time of day and has happened after hours when only the customer contact was there.
Power was isolated on a dual conversion battery backup and the system was grounded as it previously was not. All parts have been replaced 1 by 1 including the 19” chassis and main cpu. None of this has fixed the issue. All the original parts are back in. NEC thinks it is noise coming in on the cables. I have eliminated 5 of the 20+ phones but the issue continues. I would hate to have to rewire and find out that isn’t the problem.
Any ideas?

Had this problem several years ago, only one phone affected. Replaced phone, cabling and changed ports. The problem turned out to be a defective lap top power supply, I would say your problem is external to the system, something being turned on or coming on automatically. Refrig, HVAC, electric motor.

 

[1234567sk]

Yes, that is likely the case, but the sad part is this is a retail lighting company and as intermittent as it is I do not know how I would ever find it.

 

[DoubleDriveLine]

Do they have a microwave and how old is it. We had a customer that had ancient microwaves in their site. We had installed new wireless access points after doing an extensive wireless survey. Right away they started having issues with devices dropping off the network. This went on for awhile and one of our techs went out to do the wireless survey again. While doing it the laptop went nuts for a few minutes. He was not far from a micorwave and noticed someone was using it. Turns out all of their microwaves in the plant were really old. They also generated a tone of electronic interference that would kill the Wifi signal causing all of the Spectrum wifi phones to need to reconnect.

There is a chance old microwaves could do this with desk phones as well.

Back in the day old cell phones Nextel or Sprint phones if they were too close to a digital phone would make the dTerm phones generate noise out the speaker. We saw that a lot.

 

[mitchell70]

I had this same type of thing happen some years ago after replacing an old Toshiba electronic 4 wire system with a SV8100 in a school. After replacing all the equipment, we began investigating the infrastructure cabling which consisted of an array of 25 pr.cables and Cat3 and 5 cables. Using a Toner wand we began looking for similar sounds and found that the sites fire alarm system was emitting a frequency that the system picked up across the cables that caused the phones to pass this static type sound from the phone speakers. When the Fire system was in transmission mode the static came across the phones. It was a daily thing for up to a minute or so. We had to locate the source where the cables were meeting and found that a couple pairs of a 25pr was tapped to a fire cable. Once corrected it never happened again.

Maybe this helps. Good luck