How to troubleshoot the phones in my house.
November 16, 2013 3:21 PM   Subscribe

I'm looking for pointers for troubleshooting the phones in our house. They seem to have been installed by Cheech and Chong and appear to be wired in series: one to the next. However, some work and some do not.

Each phone receptacle box in our house has two CAT5 cables coming into it. Both of them are wired to the phone jack screws as follows:

blue > green
blue/white > red


That is, both blue wires are tied to the green screw and both blue/white wires are tied to red. The other pairs are not used at all. All of the jacks are like this, except for one, which I'm assuming to be the end of the line.

I'm struggling to figure out why some of the jacks produce a dial tone, and others don't, to wit:

All of the functional ones are on one side of the house, but not all of the jacks on that side of the house are working.

A small cluster might work, but a jack in between them won't.

One one side of the house, none of the jacks work. All of the them are wired according to the scheme above and I just got done checking to make sure they were all screwed down well.

My question is: when phones are wired this way, do they work like Christmas lights? That is, does a fault in one receptacle hose all of the other ones downstream? Any suggestions for troubleshooting? (this article supports the Christmas light theory).

Additional info: this house has no phone dmarc outside. As far as I can tell, it's only ever had phone service as provided by the cable company, so we followed suit. We have the cable modem in the single bedroom where the cable and phone jacks happen to be on the same wall. So there is no punchdown block or other terminus for all of the connections.
posted by jquinby to Home & Garden (4 answers total) 1 user marked this as a favorite
 
Best answer: In a phone jack, red & green are line 1. If you are using a one-line phone, that's all that matters. You should get a dial tone no matter how many other phones are hooked up the same way (until you reach some insane point of circuit loading that won't happen in reality). The other two wires in the jack are for second phone lines (normally. there are all sorts of strange ways telephone wires get used: security systems and so on).

As long as the CAT5 is consistent, it should work fine. This is not the preferred way to wire this (the "star" topology with a home run for every jack has better failure modes and is easier to trouble shoot), but it will work fine.

The most likely thing is some sort of short or wiring fault in between the jacks. As to the Christmas lights question, it depends. If the fault was just a cut wire, then no. Only the jacks downstream of that wire should stop working (I think). If the fault is a short, then yes. Everything should stop working.

The way I would troubleshoot this is go to the topmost jack that actually connects back to whatever cable box provides the service. Unhook the outbound cat5. Make sure the inbound cat5's blue and blue/white pair is connected to the red and green of the phone jack. Plug in a phone and test. If it works, add in the outbound cat5. Trace that along to the next jack. Unhook the outbound cat5 again. Check the inbound. Test. And then I would repeat this procedure all the way down the line until I found the short, cut wires, or until I just got bored.
posted by jeb at 3:47 PM on November 16, 2013


Best answer: Something like this would make checking all the jacks simple.

However you do it, I'd first check the continuity between all the jacks to make sure the connections are as you suspect. You can do this with a multi-meter or a tester like the one above. Once you've established that the wiring between jacks is all good, then start reconnecting them and checking A-B, then A-C, etc. Hopefully, you'll find that all the wires are good.

         A              B              C           
JACK --------- JACK --------- JACK --------- JACK
After that, if a particular jack doesn't work, I'd swap that jack with a working one, to see if the jack is the problem.

If it still doesn't work, maybe punt and start looking into something like this.
posted by chazlarson at 4:31 PM on November 16, 2013


Response by poster: So, we discovered the culprits!

First - a set of Cat5 cables had been dropped into a cable receptacle. Just hanging in there, loose. This break effectively cut off half the house. I jumped them quickly an lo, suddenly there was dialtone. How did we discover them? I dug up all of the Cat5 criss-crossing the attic under the cellulose insulation and found a pair dropping into a place where we knew there was no phone jack.

Second - double-checking (with mrs jq as another set of eyes) found two mis-wired jacks.

So all the jacks are now working, and we have net new phone availability in at least one place where there was none before.

Like I said...Cheech and Chong. Thanks for the guidance.

chazlarson: "If it still doesn't work, maybe punt and start looking into something like this."

Ha! Most of the house is already covered with wireless phones, but I need the hard lines because I want to move the cable modem (and main wifi AP) out of our son's room and into someplace more central. The magic combo is cable jack (for telco in) and phone jack (to interface it to the house) and now we have 2 other possible locations to put them.
posted by jquinby at 5:36 PM on November 16, 2013 [1 favorite]


Just to elaborate on what chazlarson said, telephone technicians use a diagnostic tool called a "toner and probe". You plug the toner into a convenient phone jack, and it generates a tone. You use the probe to follow the tone - that tells you which wires are connected to the jack, where they go, where they get interrupted, and so on. Fluke has the reputation for making the highest-quality, most expensive equipment of this type, but a number of other manufacturers make them as well.
posted by Multicellular Exothermic at 6:56 PM on November 16, 2013


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