DSL works, but I can't get a dial tone. Why?

August 31, 2008 7:16 PM

No dial tone inside my house, but the DSL is working. When I plug a phone directly into the grey box (a.k.a. Network Interface Device) on the outside wall of the house, at the same time disconnecting the link from the phone company's incoming line to the wiring inside the house, I get a dial tone! It seems that the phone company is still providing service. The evidence is exactly what I'd expect if there were a phone off the hook inside the house... but there isn't. What else could be going on?

For those who enjoy a good troubleshooting puzzle, here's the rest of what I know.

There are two wall phone outlets inside the house. Service to both originates in the same Network Interface Device. I can get DSL to work from either outlet, but I can't pick up a dial tone with a phone at either outlet. Calling my home phone number from a cell, I get a busy signal, again as though there were a phone off the hook. This remains true when any or all appliances (phones, DSL hub, and filters) are disconnected from the wall outlets. That seems to indicate that there isn't a problem with any of those appliances. Also, as I said above the jump, the phones in question work just fine when I connect them to the Network Interface Device.

When I break the link at the Network Interface Device, cutting off all service downstream (i.e. along the wall and into the house), I can call my home phone number from a cell and not get a busy signal -- I get an endless series of rings instead. More evidence that the trouble is somewhere downstream.

We have had a problem with mice, so it's possible that a wire was gnawed through. But this doesn't explain why our DSL is still working -- from both wall jacks I know about.

I feel like my experiments have ruled out every reasonable explanation for what's going on. Kind linemen and -women of MetaFilter, what have I not tried?

posted by aws17576 to technology (22 comments total)

Did you set up the filters that came with your DSL modem?
posted by k8t at 7:18 PM on August 31, 2008

Did you set up the filters that came with your DSL modem?

I did, but just in case the filters were a problem, I tried disconnecting all DSL equipment (including the filters and hub/router) and just connecting a phone directly to the wall. Still no dial tone.

I should probably clarify that we had normal service until a couple of days ago, and I didn't do anything to the wiring recently. I would take this as more evidence that the mice were involved, if I could figure out what a mouse could even have done to cause the symptoms I'm seeing.
posted by aws17576 at 7:27 PM on August 31, 2008

and I didn't do anything to the wiring recently

... until I began conducting the troubleshooting described above, that is :)
posted by aws17576 at 7:28 PM on August 31, 2008

something to try would be to disconnect the wiring from the house, and then check an inside line while you re-connect it. if it is something off-hook (or a short or something), you'll at least hear the dialtone before that times out.

dsl isn't bothered by something being off-hook, or a fault that causes the same sort of condition.

we had a similar problem recently, and i think it was the cord connecting our cordless phone base station.
posted by jimw at 7:49 PM on August 31, 2008

Assuming you've absolutely eliminated the possibility of a phone off the hook, I'd say you have a partial short in the wiring somewhere in your house.

If it was a complete short (red and green wires connected), everything would stop working including DSL.

If it was a broken wire, everything would stop working including DSL.

So you have something in between. Two wires are barely touching, somewhere, and it's enough to appear "off hook" to the telco but not enough to stop your DSL from working.

Please follow up if you want some detailed troubleshooting instructions for the wiring. Depending on your experience, you might just want to call an electrician or the phone company.

Also, I'm assuming you have disconnected all phones? One of them could be causing the problem despite not actually being "off hook" if it has bad wiring inside or a bad cable.
posted by mmoncur at 7:49 PM on August 31, 2008

jimw: something to try would be to disconnect the wiring from the house, and then check an inside line while you re-connect it. if it is something off-hook (or a short or something), you'll at least hear the dialtone before that times out.

I just got a friend and tried this. He reports no dial tone, even for a second.

mmoncur: Also, I'm assuming you have disconnected all phones?

I did try that, but still got a busy signal when calling from a cell phone. I swear it's as though there's a phone in this house that I don't know about -- but that doesn't make any sense, because everything was working a few days ago...

Please follow up if you want some detailed troubleshooting instructions for the wiring. Depending on your experience, you might just want to call an electrician or the phone company.

Thank you -- I would be very grateful for any (safe) troubleshooting suggestions. So far, I've basically just experimented with different configurations of appliances, but I think I've exhausted that line of attack.
posted by aws17576 at 8:21 PM on August 31, 2008

Shot in the dark, but we lost our land lines recently and it turned out to be some problem with our home security system- a short (or some other issue with it) was screwing up the phone lines (the alarm had a phone line- we never set it up but the physical connection was still extant, compliments of our house's last owners) and was also playing havoc with our satellite (I guess because the co-ax outlet for one receiver shared a plate with a phone jack). We disconnected the alarm line and all our problems disappeared. Since we never activated the alarm in the first place, it was win-win for us.
posted by ethnomethodologist at 8:39 PM on August 31, 2008

Have you called the number while the internal wiring is hooked up to see if it gives you a ring or a busy/voicemail? This probably won't tell you anything new unless you actually get ringing (heard from the perspective of the incoming call).
posted by RikiTikiTavi at 8:42 PM on August 31, 2008

RTT, scroll up.

AWS, since you say that the two inside extensions are wired directly to the NID, I'm assuming that you have physical access to where they are connected. So, disconnect one extension at a time, at the NID, and see if one of them keeps working. If you can isolate the problem to one extension, that's half the solution right there.

All the red wires get joined together, and all the green wires get joined together. Take a couple pictures of the wiring before you take anything apart, just in case you can't remember how it goes back together.

In the process of fiddling with the wires, you may find a third extension line that you didn't know about. That could be where your short is.
posted by intermod at 9:06 PM on August 31, 2008

I think the mice left their new phone off the hook. Your interface has plugs that run the phone line into the house here. If you unplug those, (they are the wire(s) going into the house) you can test the line from the phone co. by plugging in a phone right there. If you get a dial tone, your interior wires are bad.
posted by lee at 9:08 PM on August 31, 2008

Uh, duh, I skipped the first paragraph when I opened. Your wires are bad, you need to replace them.
posted by lee at 9:46 PM on August 31, 2008

I had these symptoms a couple of months ago. There was a short in one of my phone jacks (but it could've been anywhere else in my wiring just as easily, not just a jack.) Surprisingly, DSL can still work (I found other anecdotal evidence on the web of people with the same experience.)
posted by Zed_Lopez at 10:06 PM on August 31, 2008

Your phone co. has diagnostic equipment that can tell you exactly whats wrong (e.g. broken wire and where it's broken without tearing apart your walls. Call them.
posted by docmccoy at 10:46 PM on August 31, 2008

The phone company will charge you for any problem-solving on your side of the demarc, though, so if you get them to do some work be sure you know how much they're going to charge for it.

A high-resistance short seems like it could lead to exactly what you describe. I'd think a dead short would kill the DSL also, but if it's only drawing enough current to make the telco think your phone is off the hook, that shouldn't bother the DSL.

I recommend what intermod said: start trying to find the fault by a process of elimination. Maybe visually inspect your phone jacks to see if some conductive crud has gotten wedged into one of them?
posted by hattifattener at 11:42 PM on August 31, 2008

I did try that, but still got a busy signal when calling from a cell phone. I swear it's as though there's a phone in this house that I don't know about -- but that doesn't make any sense, because everything was working a few days ago...

Just an anecdote: this actually happened to us. There was a phone in the basement of our (rented) house we didn't know about. We only have cell phones. One day, it rang and totally freaked us out... turns out the phone company had activated a previously dead line by mistake.

Troubleshooting advice:

First, if both of your extensions are wired directly to the NID:

NID===E1
|=====E2

...intermod has it covered. Once you've isolated the problem to one of the extensions, there's not much you can do besides running a new wire.

On the other hand, every house I've seen has had the extensions wired in series:

NID=======E1=======E2

The NID is connected to extension 1, and extension 2 is wired from extension 1, and so on. If this is the case, you can take the covers off your phone jacks and look at the wiring - one of them should have some extra red-green wires connected, those go to the other extension. Disconnect them and if extension 1 starts working, #2 is the problem. If nothing changes, #1 is probably the problem.
posted by mmoncur at 12:56 AM on September 1, 2008

Oh, one more tip:

Assuming your wiring is typical, the signal is carried on the red and green wires. There might be a second pair of wires (yellow and black?) that are unused, unless there's a second phone line or apartment. You might be able to disconnect the red and green wires of the bad section of wiring and attach the black and yellow ones instead to avoid running an entirely new wire.

I only recommend doing that to replace interior wiring, say the wire from E1 to E2 in my diagram. Don't mess with the telco's equipment because you might end up needing their help.

And a couple more things:

- The (partial) short might be in one of your phone jacks. You might try replacing or testing them before you bother with new wiring. Also, it might be a phone jack you're not using.
- Ethnomethodologist already mentioned security systems might be hooked to a phone line. You might also look for any other device that might be hooked up - a modem, FAX, or a TiVO for example.
posted by mmoncur at 1:06 AM on September 1, 2008 [1 favorite has favorites]

There's some great advice here, so I just want to add one thing: as you follow mmoncur's advice and arrive at jack #2, which should be the last jack in your wiring, pay attention to those red/green wires. If they continue downstream from jack #2, you've just confirmed your suspision that there's another jack (or alarm interface, or something) downstream from there.

Having dealt with this kind of nonsense myself (a nail driven into a wall had nicked a wire…haven't hung any pictures lately, have you?) I know how aggravating it can be. If it was me, I'd replace the jacks first. They're cheap, and you can't always tell with a cursory glance if anythings wrong with them. If it's not the jacks, swapping red/green for yellow/black should do the trick.

Good luck, and please let us know what the final outcome was. We all enjoy a good troubleshooting puzzle.
posted by dinger at 4:45 AM on September 1, 2008

Thanks for all the advice! To add to the mystery, I woke up this morning and had dial tone throughout the house. If there is a short somewhere, then it seems to be intermittent. (Or, per lee, the mice installed their own phone and noticed overnight that it was off the hook...) I'm completely bewildered, but as long as the system's working, I can hardly continue troubleshooting (though I will follow the wires when I get home today, just to see where they lead). I promise to post a follow-up if I ever figure out what went wrong.
posted by aws17576 at 8:46 AM on September 1, 2008

Cordless phone? Any lightning recently? The same thing happened to me and it turned out that was the cause. Had to buy a new phone.
posted by Zambrano at 10:34 AM on September 1, 2008

Ah, the plot thickens. An intermittent short sometimes means water. Somewhere, somehow, a connection gets wet, causing a short. As the water dries, the short goes away.

The good news is, this can mean the wires are intact; in the case of water, a short can only occur between bare metal components, e.g., the connections in your boxes. Is it possible water got inside your outside network interface box, possibly shorting the wires going into the house but leaving your phone company connection intact?
posted by dinger at 1:58 PM on September 1, 2008

In my case, the problem actually went away after unplugging and plugging a phone into the problem jack -- loose wires in the jack had shorted, and just the little bit of jiggling knocked them apart. I bet you've done a lot of plugging and unplugging of phones while troubleshooting this.
posted by Zed_Lopez at 4:59 PM on September 1, 2008

I second Zed_Lopez: in the process of fiddling with all of the connections, you've accidentally fixed it.

A more distant possibility is water, as dinger said, or even humidity - if two wires are barely touching, the humidity in the air around them can affect the connection.

At any rate, don't touch anything and maybe it will work for a few years...
posted by mmoncur at 10:01 PM on September 1, 2008