sundance-communications.com/forum Forums General General Telephone & Systems Information Noisy CO Lines

Greetings, I'm chasing a problem with a Panasonis KSU that's driving the customer and I. It is what sounds like a 60hz hum on all CO lines. I've grounded all the equipment along with the cable shields. Even tried using my toner probe trying to find the noise. It's one of those intrmittent things. Kinda like a motor or a pump kicking in, running for a min. then kicking out. There is a pedestal adjacent a city water pump house that is a concern; but I'm clueless at this point. Any suggestions will be greatly appreciated. If it's any help; it's a Pan 1232 ksu (double cabinet) w/ a Pan TVS100 vm. Thanks in advance.

p.s...I've tried rf filters on the grounds; no help.

are you using a good ups with power conditioning ?

when the hum is there is it only co lines or does it exist on icm calls ?

Have you checked it from the DEMARC?

Just the CO lines. And no as far as the good UPS; it is actually pretty old. This just started happening out of the blue; i.e..nothing obvious has changed. So, my thought was that significance of UPS w2as minimal. My level of experience is 4 years; so needless to say I'm a novice tel. tech. Thank you!!

I haven't been able to catch it at the demarc. Every time I hook on the line is clear. Although I may just be missing it, as it is intermittent.

If you're hearing a 60hz hum and as you said there is a pedestal close to a pump you may have found the problem. Wire a straight line set ahead of the equipment and when the customer hears the hum have them pick up the SLT to see if it on it also. I really think from your description you've ID the source, good luck on getting it corrected.

Cant you buy some of the 60hz filters to tune it out? Might end up with kind of a dead spot but it's better then an annoying hum.

Greetings, I'm still chasin the "ghost", although I now think it's something other than 60hz noise. Higher pitched?? Anyway, I've got a slt hooked up to the exchange side of the demarc. Since I hooked up the slt the noise has not returned. We are in the area hit by the ice storm followed by snow. The noise is getting less frequent the more thawed we get.???

Again, Thanks to all. To recap a posting that I read earlier; this forum rocks!!

I would suspect an improper ground on a a piece of equipment like a refrigeration or HVAC system.
When it's wet, maybe the ground is shunting some current to the phone lines? Just a guess - but it could happen with Ice between two isolated grounds causing a ground loop.

Bluzman:

The SLT that is connected to the CO line may actually be conditioning the line. Since a 2500 set has a wound ringer coil and an isolation capacitor, this provides an excellent filtering means for transient AC interference.

If this ends up solving the problem, you may want to consider terminating the lines on Suttle 625-TD jacks. They are equipped with a built-in half ringer circuit that filters out line noise fairly well. We use these on paging circuits that involve a CO line for this very reason.