Geek Wiring

Our phones went dead yesterday. Unfortunately, that's becoming a common occurrence, and it has caused us to be very ticked off at Comcast because we've been without service a lot.

Turns out maybe it's not their fault.

Oh, it was their fault originally. I know that because they had techs out here three times fixing things. But this particular outage isn't their problem because I can plug a phone right into their modem jack and it works fine. It's distributing to the rest of the house that's the problem.

It's not my problem. This is a new house; it's all under warranty, so I just called Customer Service (for the community, not Comcast service) and the usual guys showed up to take a look. I demonstrated the immediate symptoms and they shook their heads and left, saying they'd be back later with tone injectors and so on to trace it all down.

The Comcast modem sits in my closet. That may sound strange, but that was the only place where a cable connection and a phone jack were close together. It also keeps it out of sight and keeps it separate from my other Comcast modem for Internet. This makes me happy and also will let me switch to Verizon FIOS without confusion if I want to.

So anyway: a line runs from the phone jack on the modem to the wall jack, and that distributes phone service to every other wall jack. Except right now it doesn't. I suppose I could wait for the CS guys to come back, but I wanted to know myself, which should be an easy enough thing to do consider the tools I have in my trunk for testing network cables etc.

Well, yeah, except for "in my trunk". My wife has gone off to medical appointments and will be gone all day. No car, no trunk, no tools.

No... not exactly no tools. I poked around in unpacked boxes and came up with a voltmeter. The cable leads for it were a little harder to find but a bit of rummaging turned those up. An AA battery from the closet and a quick check - yes, the continuity test works. OK, good so far. But the test leads were way too short to reach from one phone jack to another. Hmmm..

More rummaging turned up a mostly empty spool of telephone wire. Not much left on it, maybe 15 feet, but it just might be enough. I couldn't find a wire stripper, but careful use of scissors can strip the outer jacket and you can strip the inner stuff with your fingernails. I found a screwdriver, took out the phone jack in the closet and wired one end of my spool to it.

That brought me tantalizingly close to the other phone jack, but not quite close enough. I could reach the wire and the jack with the voltmeter cables, but I couldn't easily hold everything in place and see the meter. I went back out to the garage and started digging again.

Ahh, here's just the thing: Molly bolts. A nice screw head to sock down the wires with, and a tight place to jam the voltmeter leads. Perfect. A bit geekish, but it works.

I could now comfortably work at the other phone jack and quickly found that while the green and red had continuity, yellow and black were open. But wait: it's the green and red that have milliamp voltage when the modem is plugged in, so they must be carrying the line. And there's something else wrong: green and red are shorted: I can read continuity right across them (with everything unplugged everywhere). That doesn't seem right..I made sure my Molly's weren't touching.. nope. This puppy is shorted in the wall somewhere.

While ruminating over that, the CS guys showed up. I showed them what I had and they looked confused. "It's not supposed to be wired like that. Solid blue should be on the red."

Ok, that's fine with me - I didn't wire it. But it still shouldn't be shorted. He agreed. We pulled all the wall plates (there are only three, fortunately) and rewired as he wanted it. Still shorted, and still no distribution of dial tone.

We then totally disconnected all wall plates, leaving bare wires hanging. Still shorted.

I asked him why my yellow and black had no connectivity. "We don't wire them in". Oh. Good to know, I guess.

We did observe some minor damage to the wire at one jack. There was enough extra length to cut it back. Bingo, short gone. Momentary jubilation as we hooked the plates back up. However, though the short was gone, we still had no dial tone. It's strange because I now have connectivity on each wire and no shorts. I keep double checking myself because it makes no sense..

That's where it sits now. I can connect a phone directly to the Comcast modem in the closet, but that's it. That's a bit inconvenient but at least we do have a phone for emergencies. CS guys will be back tomorrow or next week to hack at it more. I can live with it.


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© Anthony Lawrence







Fri Jun 9 20:46:39 2006: 2096   TonyLawrence

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Just now I rechecked everything and hooked it back up. Plugged everything in and.. dial tone.

I do not know what is going on.



Sat Jun 10 00:55:32 2006: 2097   bruceg2004


How does the 911 service work with Comcast? Do you keep a POTS phone around for power outages?

That FIOS service looks nice. Based on the timee it took Comcast to finally bring broadband to our area, we should have fiber in another 10 years :-) How fast is that fiber connection? Man, that would be real nice!

- Bruce






Sat Jun 10 01:21:44 2006: 2098   TonyLawrence

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I never thought about 911.

FIOS comes in various speeds: 6/2 (Mb) is $34.95 a month. They say they expect to be able to offer TV over it within a year or so. That's good: Comcast needs more competition.



Sat Jun 10 11:47:59 2006: 2099   bruceg2004


That is good that they will offer TV over FIOS. The more competition, the better.

- Bruce



Sat Jun 10 15:40:16 2006: 2102   BigDumbDinosaur


I demonstrated the immediate symptoms and they shook their heads and left, saying they'd be back later with tone injectors and so on to trace it all down.

Why didn't these bozos show up with the correct test gear to start with? I never go to a client's location without tools and test equipment, even if there are supposedly no hardware problems to be solved.

But the test leads were way too short to reach from one phone jack to another. Hmmm..

In a situation like that I would make a "shorting loop" -- split out the tip and ring (red and green) leads and twist 'em together. Go to the far jack and check for a dead short between tip and ring at that location. You have tested both leads at the same time. Remove the shorting loop and verify that you have an open circuit. Repeat the process for the other pair, if present (although it is seldom used on a single line system).

I carry a made-up shorting loop with an RJ-12 plug attached just for that purpose, although I do have an adapter that allows me to connect my LAN cable meter to a standard station D phone line.

I can read continuity right across them (with everything unplugged everywhere). That doesn't seem right..I made sure my Molly's weren't touching.. nope. This puppy is shorted in the wall somewhere.

This is a common problem in new construction, usually caused by sheet rock installers driving overly-long drywall screws at an angle and hitting phone and coax cables that are attached to the sides of wall studs. Back when I used to do a lot of network cable installation, I was constantly running into this crap. It was what motivated me to get out of the cable business. The client wasn't going to pay for the repairs, of course, and the drywall hangers were long gone, so who was going to cover the cost? BTW, these types of faults can be intermittent and in some cases, only reveal themselves when the ringing voltage (90 VAC at 20 Hz) is applied.

"It's not supposed to be wired like that. Solid blue should be on the red."

If the building cable is multiple twisted pair and is being wired to a USOC (Universal Service Ordering Code, see
(link) for more info if you're curious) RJ-11x scheme (most common in residential work), the first line would (should) appear on the blue pair -- the blue/white lead goes to tip (positive), which would be green on a standard RJ-11 jack, and the solid blue on ring (negative), which would be red on the same jack. Technically speaking, a polarity reversal (i.e., a swap of tip and ring) should result in an inoperate touchtone keypad. However, some phones have small bridges to make the phone polarity-agnostic. In a single line installation, the yellow and black connections on the jack would not be used, unless the phone is one of those with a lighted keypad that requires a low voltage AC source (haven't seen one of those in a quite a while).

However, though the short was gone, we still had no dial tone.

Perhaps the ATA (analog telephone adaptor) itself is defective and can't handle whatever line loading is present.

All of what Tony describes reminds me of why I didn't switch my business phone service to VoIP, and why I don't plan to do so any time soon. Also, since 911 service with VoIP is problematic (inoperative in our area, I found out a few days ago), what do you do if someone at your place has a medical emergency? Run out into the street screaming "Help me! Help me!"?



Sat Jun 10 15:47:50 2006: 2103   TonyLawrence

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Why didn't these bozos show up with the correct test gear to start with?

Because they got the call while out in the community doing other stuff. It makes sense for them to swing by - it might be something simple and stupid. Because they do everything from plumbing to sawing trees, they don't always have every tool they need with them.. they really are a quick, efficient bunch and very responsive.






Sun Jun 11 01:20:22 2006: 2105   BigDumbDinosaur


If one is going to fix phone problems a tone injector, receiver probe and handset are
de riguer . However, I think I slightly misunderstood what I was reading, since I thought you were referring to Comcast. If these guys are building maintenance people, than I guess I was being unfair about the tools thing. In fact, I'm a bit surprised that they would tackle phone problems. Sounds like you may have a better than average bunch there.

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