So I did a little more checking around. Every phone in the house has the same background hum. This includes direct wired phones as well as the cordless. When I took an old direct wired phone and connected it to the NID, there was still a minimal hum, but much less than in the house, and honestly it is so faint it may have been there forever. So I think the problem is with the in house wiring. About two weeks before the problem surfaced I did change the wiring of one jack, as I canceled one of our two phone numbers, but the problem started several weeks after that, so I doubt it is related. How do I troubleshoot this problem? One other fact is that when I disconnected all the phones for 20 minutes the problem went away for several hours then returned.
Many phone services offer free or low cost inside wire repair plans. If your provider offers one, you can sign up, wait a few weeks, then report a problem.
It could be something like a weak connection in a jack or worn phone cord causing the noise. It takes some fairly pricey tools to pin down a subtle noise problem quickly. You can do things like unplug each phone for a day or two and see if it goes away. If one phone proves to be the culprit, you could then try rewiring the jack, replacing the cord, or replacing the phone to try and correct the problem.
If its none of those you have a wiring problem inside the walls or out at the box.
I had this problem once - it turned out to be a bad ground connection outside of my apartment. Was fixed very quickly.
A 60 cycle hum can also be induced into telco wiring if that wiring runs parallel and in close proximity to house wiring for any appreciable length.
Pay no attention to it, and certainly don’t say, “Attorney General Gonzales, is that you?” And if you hear a started gasp at the other end if you do say that, don’t be surprized if the black helicopters show up shortly thereafter.
Have you tried disconnecting all the phones and then plugging in one at a time? If it is one of the instruments this will isolate it to the defective unit.
Humbusting 101
You’ve already done step one - Unplug the inside wire at the NID (aka demarc) and check if the problem exists there. In a perfect world, there would be no hum or static at all at the demarc. World’s not perfect, so a little hum or hiss might be unavoidable. If it’s bad enough at the demarc to bother you, call the repair service as it’s their problem to fix.
Step two: Plug the house wiring back into the demarc. Go around the house and unplug EVERYTHING. Unplug every phone, fax, anwering machine, cordless phone base, modem, satellite / cable TV box, alarm panel, DSL modem, etc. Using the same phone that you used to verify line quality at the demarc, plug it in a a regular jack and listen.
No problem? The fault lies with one of the things that was plugged in. Plug things back in one at a time, and listen after each one’s back in. When the problem returns, the last-connected thing is the culprit, or rarely, the jack it’s plugged into has a problem.
Still a problem? The wiring has a fault. This is harder to sort out. If your home is wired up with “home run” wiring where every jack has its own wire running to the demarc, it’s relatively simple, but still a pain - start disconnecting, one by one. When the problem goes away, the last-disconnected line is the bad one. If your house is wired with multi-pair cable and you’ve only got one phone number, try using a different pair in that cable. If that doesn’t fix it, then the cable’s been mortally wounded (gnawed on by rodents, someone drove a nail through when hanging a picture, etc.) and will need to be replaced.
If the house is set up with one cable leaving the demarc and daisy-chaining from one jack to the next, the job is a lot tougher. About all you can do is try to figure out the path the wire takes from the demarc, jack to jack. Then, starting at the second-to-last jack, disconnect the last jack and its wire. Problem gone? (You lucky SOB!) If not, re-connect the wires and go to the next jack and disconnect. Lather, Rinse, Repeat until you find the problem. Most likely, you’ll need to run new cable for that section, or use a different pair of wires in the existing cable, on the hope that you’ve got multi-pair cable installed.
Quite frankly, if your home is daisy-chain wired and has more than two or three jacks, this is the time to ask yourself what your time is worth, and if it’s better to fix the problem with your checkbook. Either start paying for the inside wire protection, or pay whatever their hourly rate is for a service call.
On the nature of problems - hum that’s been there forever is most often caused by wiring that was run poorly, and too close to AC power wiring. The old “quad” wire (straight red/green/yellow/black wires) was notorious for picking up AC hum. The newer twisted pair (Cat 5 - same stuff you’d use for LAN cabling and identified by blue/white, orange/white, green/white and brown/white pairs) is much more resistant to picking up noise.
New hums are usually from one side or the other of the line being grounded. A “mild” gounding will cause a hum, but a full-on hard short to ground will probably make the line completely unusable.
Hiss is probably a phone company problem - something like a bad repeater amplifier in the line or a nearby AM radio station’s getting picked up by the wires acting as an antenna.
Pops, crackles and static are usually bad connections. Dirty jacks, loose screws, bad splices or bad cords are the usual suspects.