ECN Forum Forums General Topics of the Trade Voice - Data - Video Discussion Intermitant phone static

Possibly disconnect the inside wiring, unplug the phones/equipment and run an insulation test? If the damp isn't enough to cause static, it still could be enough to show nasty low resistance with 200+ volts from a tester.

It may not be a magic bullet but I have a second RJ11 just inside the house from the Dmark where I can test without going outside. The homeowner might be more likely to do that. I also homerun all of my phone wires to a 66 block with bridging clips for each run but that may be too much for most of your jobs.

Here in Britain we can dial a test number which runs an automatic routiner on the line, looking for basic faults such as low-resistance to ground etc. It doesn't always identify every fault, but in a large number of cases of noisy lines you can bet that the tester will come back with a result which indicates it's TelCo plant problems.

That can be done here too. Unless you are a TELCO tech you call repair (from another line) and they will run the test. Not always conclusive especially if the fault is close to the subscriber.

Possibly disconnect the inside wiring, unplug the phones/equipment and run an insulation test? If the damp isn't enough to cause static, it still could be enough to show nasty low resistance with 200+ volts from a tester.

Don't know that I would want 200+ volts on that wiring or the jacks!

It may not be a magic bullet but I have a second RJ11 just inside the house from the Dmark where I can test without going outside. The homeowner might be more likely to do that.

Only problem with that is it is after the demarc. Most current demarcs incorporate a function that disconnects the wiring after it when you insert a plug into its test jack. This eliminates all inside wiring problems as well as phones off hook from influencing your test. If you use the inside jack to test it's just another jack bridged across the line and will have the same problems as all the others.

I also homerun all of my phone wires to a 66 block with bridging clips for each run but that may be too much for most of your jobs.

Very good. That's the way they allways should be done.

-Hal

That IW quad or CAT3 is rated at 300 volts, and the actual breakdown voltage is much higher. The telco's test gear applies up to +/- 275 volts to probe the "signature" of various self-test devices in the loop plant, so 200 volts is no big deal, even with telephone sets connected.

None of which helps if the problem is on the telco side.

Having the test jack indoors is a nice touch, especially when it's raining. If it's an RJ31 "alarm" jack instead of an RJ11, it can also be wired to disconnect the rest of the premises when a test set is plugged in. It's still past the demarc, though, so it can't completely vindicate the IW.

This may be a long shot but where I am when we have a person complaining of static on their line it is a bad handset cord 99% of the time. This is in a PBX environment so it is a totally different animal than residential telephony, but it may be worth a shot.

First off, thanks for hearing my gripe!

As for test numbers/lines, SBC has them, but they keep them top secret. (Clean line, modulated tones, ring back, etc.) You have to find a real friendly phone guy to let you have one. They give them out in groups so they can track who has them, and change them every few months. Yesturday, I used a "borrowed" clean line number. (Still won't help, if not happening right then.)

"I also homerun all of my phone wires to a 66 block with bridging clips for each run but that may be too much for most of your jobs."

"Very good. That's the way they allways should be done."Depending on the install, it's 66, or 110. This one is a 110, and although it makes a great connection method, and in some cases is fantastic if your customer re-purposes lines on you, like many of mine do, it's great. But troublestooting can be a PITA!

As for higher voltages, that's essentially what a sidekick does with with a signal +/or capacitive charge in a leakage or stress test. Kind of like a megohmeter for phone lines.
http://www.calcentron.com/Pages/tempo/tempo_telco_instruments.htm

Anyway, I have other toys to spot faults, like TDR, but likewise, you can't spot it if its not there when you are. The big problem is that all of these trips cost mulla, and can't charge for them if nothing is found. (Well, I could, but the boss won't, and the 2 - 3 of these a year add up.) It's gonna come down that these need to be taken care of while it's happening, but that screws up schedules. Mine at least.

The telco's test gear applies up to +/- 275 volts to probe the "signature" of various self-test devices in the loop plant

Well, I do know that OUR secondary protectors clamp at 235 volts and have sneak current fuses. So if they were applying that kind of voltage both they and we would know about it.

I also think that that kind of voltage would pose a real danger to any tech since they would not expect anything higher than ring voltage or maybe an open carrier circuit voltage. So I kind of doubt this test method would be used except under strictly supervised conditions if you are correct.

-Hal

Hal,

As I recall, the current during the HV test is intentionally limited to a few mA, and the duration is less than one second, so it's much safer than ringer power.

(Surprisingly, IEC safety standard EN60950 allows essentially unlimited voltage for remote power feeding over telecom pairs as long as the current is limited to 60 mA. I still wouldn't want to brush against it!)

The voltage is also balanced, so it doesn't exceed +/- 137.5 on each side with respect to ground, which is well below the threshold of solid-state protectors.

John, interesting you should mention that standard. When I was in Ohio we had an interesting Digital multiplexer box on the house, providing 2 lines over one pair, when I measured the input voltage, I was amazed to find over 270 volts from the exchange pair
The reason we were 'fiddling' was to get the phone co to remove it so we could get ADSL, but that level of voltage scared me.

270 volts (+/- 135 volts line-to-ground) is very common in North America for repeaters and pair-gain devices like you mentioned, because no special current limiting is required when each line is under 140 volts. Above 140, a sort of "D.C. GFCI" is required that limits the current to 25 mA line-to-ground and 60 mA line-to-line.

I know you'll be pleased to know that those limits have been determined to be "...unlikely to cause organic damage or harmful physiological effects."

(I'm not gonna touch it -- let's get Mikey!)