Why does my landline go nuts when I pick up the phone?

August 25, 2010 9:02 AM

Why does my landline go nuts when I pick up the phone?

I recently moved my home office into a different room. This room has a bunch of phone jacks which were all dead. So, I opened one of the jacks up and found which wire pair it was utilizing (green & green/white). The phone service in my house uses the blue & blue/white pair -- I know this because I opened the service box outside.

Apart from this office, I only have three phone jacks in the house, all of which are already wired to this blue & blue/white pair, and they all work. I have a DSL modem on one of those jacks, and the rest of them have DSL filters installed.

I just wanted to get a dial tone on one of the phone jacks in the new office.

So, since the wiring in this house is hard to follow, I figured I'd just go outside to the service box and wire both the blue and green wires to the terminals for my active phone line. Just to be clear: I didn't move the blue wire pair -- I just patched in the green wire pair on the same terminals.

After doing this, I verified that I still had a dial tone on all of the house phones and the DSL still worked. Then I verified that the phone jack I wanted to activate also had a dial tone. Awesome -- problem solved!

Except since then I've noticed that if I use the newly activated phone jack in the office the entire phone system in the house goes bonkers. Sometimes, the DSL modem will lose signal, sometimes the dial tone will disappear, and sometimes both of these things happen.

Oh yeah, I do have the DSL filter on the new jack if that matters.

So, what the heck is going on? Is there some property of the phone system I'm not considering?

posted by MustardTent to grab bag (12 answers total)

Did you get the polarity reversed on the green / green&white wire pair?
posted by brain at 9:36 AM on August 25, 2010

Is the other end of the green/white wire connected to the same place as the end of the blue/white wire? My first suspicion is always "grounding problem."
posted by muddgirl at 9:47 AM on August 25, 2010

The DSL filter could be bad. Try switching two of the filters to rule out the filter as the source of the interference.
posted by COD at 9:54 AM on August 25, 2010

I had the problem with a bad DSL filter. Replacing the cheap non-names ones I had from my ISP with better ones from a local computer dealer solved the problem.
posted by bonehead at 10:07 AM on August 25, 2010

I'm with muddgirl. You mention what you did with the solid green wire, but not the other half (green/white). If you didn't connect it to anything, right now it's what we'd in Electrical Engineering call a "floating connection". Basically, that green/white wire is acting as an antenna and picking up all sorts of electromagnetic interference. When you pickup the phone, the green/white wire is then connected to the rest of your phone system, and voila! Noise on the line.
posted by sbutler at 10:20 AM on August 25, 2010

I once had a similar problem, whenever I answered the phone the internet cut out. It turned out that the phone, which was wireless, interfered with the WiFi signal. To be honest, it was a long time ago and I don't remember the details, but it all went away after changing phones.

Anyway, the grounding issue sounds likelier, but if that isn't the case, then this is another possibility.
posted by Kattullus at 10:55 AM on August 25, 2010

brain:
I swapped the green & green/white wires. Seems to be working! I didn't even consider the polarity issue. I'll keep it like this for a while and see if that was the problem.

muddgirl:
That doesn't seem to be the case, but there is so much patching and wizardy in the phone lines here that I really couldn't tell without opening the walls. I'll keep this in mind in case brain's solution doesn't work out.

COD/bonehead:
I'll also keep the DSL filters in mind.

sbutler:
I apologize if I wasn't clear enough. I did actually patch in both the green & green/white wires. As a side note: I often wish I got an EE degree instead of a CS degree so I could understand electrical issues & properties better.

Kattullus:
Yeah, I've experienced that as well. I once had a wireless phone that unfortunately operated on 2.4 GHz, right where all my Wifi channels are. I'm not using it anymore.

Thank you all so much!
posted by MustardTent at 11:23 AM on August 25, 2010

Actually, I should be able to test the lines using a meter to check on muddgirl's concern. I'll make sure to get that done.
posted by MustardTent at 11:26 AM on August 25, 2010

If the system was wired properly, the green and blue wires should both be the negative polarity or receiving lines, while the green/white and blue/white wires should be positive polarity or transmitting lines.
posted by muddgirl at 11:30 AM on August 25, 2010

So does that mean that I should check the phone jack in the office? Since that is the only phone using the green pair maybe that is the source of my problems?

If so, then I can swap the lines back at the box too.
posted by MustardTent at 11:37 AM on August 25, 2010

I mean, it's not a big deal, as long as the positive on one side is hooked up to the positive on the other, and same with the negative. I don't know enough about telephones to say whether this is the real source of your problems.
posted by muddgirl at 12:41 PM on August 25, 2010

There is a correct polarity for phone lines, but reversed polarity is so common that lots (most?) phone equipment is designed to deal with it. But maybe the phone in your office doesn't deal well and loads down the circuit when you pick it up.

Anyway, the two wires in a phone connection are called tip and ring for historical reasons (dating back to manual plugboard operators). Tip should be the more-positive wire. If you are looking into the jack, the middle two of the 4 or 6 conductors are tip and ring; if the part where the springy clip bit goes is at the bottom, then the ring should be on the left, tip on the right; the ring wire also usually has the more-solid coloring if you are using solid-and-stripe color coding for the wire pairs.
posted by hattifattener at 10:59 PM on August 25, 2010