Computers & Electronics

Diagnosing dead short in home phone wiring.

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  • Jan 5th, 2022 12:23 pm
Deal Guru
Jul 7, 2017
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SW corner of the cou…

Diagnosing dead short in home phone wiring.

Found out today that there's a dead short in the home phone line.

Diagnosis steps:
  • A single phone plugged directly into the POTS outlet of the FO modem works (dial tone and light).
  • Once I plug in the line that goes to the rest of the house, nothing. No light, no dial tone.
  • Using a splitter the directly-plugged in phone works as long as the other line is not plugged in (tried switching around cables on the splitter so that isn't the problem).
  • Tried unplugging all the phones and devices connected into the home phone plugs (all at once) with no success.
  • Nothing changed since it as last used yesterday afternoon (answering an incoming call). Nothing plugged in or unplugged for months.
What are the next steps? Wondering if I should buy a tool to diagnose sockets? Which pairs are actually live in the RJ-11 sockets?

Before you say anything about land lines, we have one as cellular reception is poor at our location and can be non-existent in inclement weather (service provider is Rogers, not that the other large incumbent Telus is much better, Bell and the other minor players are non-existent). We have to tell guests to turn off roaming otherwise they could end up with a huge bill.
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7 replies
Deal Fanatic
Jan 5, 2003
5068 posts
5010 upvotes
Toronto
How is the line split within the house? Does it have various splitters or a punch down block similar to this? Image
Deal Guru
Jul 7, 2017
10217 posts
5530 upvotes
SW corner of the cou…
jm1 wrote: How is the line split within the house? Does it have various splitters or a punch down block similar to this? Image
I was wondering about that so traced where the feed line goes, and found it goes to the outside of the house where the punch down block (assuming that's the technical name) is (and where the copper presumably used to run to). Will have to open it up tomorrow and see what's inside.

Thanks
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Deal Addict
Dec 6, 2020
1406 posts
1688 upvotes
Generally speaking, POTS should use the red and green wires, but there's no technical requirement that prohibits installers from using yellow/black, or using wire that has a completely different color scheme.

The only way to diagnose this is by a process of elimination -- isolate one jack at a time until you find the culprit.
Deal Expert
Aug 2, 2004
38395 posts
12020 upvotes
East Gwillimbury
The grey box outside is where the line gets connected. The demarcation point is usually from that box into the basement near the fuse panel. That is where you will find the block where the line is split.
Deal Guru
Jul 7, 2017
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SW corner of the cou…
I went out to the box today. Proverbial rat's nest of wiring (but no evidence of literal rats or other rodents). Maybe have been Telus copper wire that was converted to Shaw Cable phone, reconverted to Telus FTTH. Block (the ones with the push-down tabs) is just loose. Looked inside, wiggled around. Works. Too much work to connect it right especially if one has old eyes.
I smile when I see container ships sailing past my house laden with stuff made in China
Deal Expert
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Apr 16, 2001
16514 posts
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So you're now using the home phone service from a fiber ISP, correct? Is the outside block disconnected from the old incoming POTS line coming from the pole or underground?
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Deal Guru
Jul 7, 2017
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Yes/no. I am guessing the original telco copper line went to the external demarc box. When the previous owner used cable phone, the line from the cable modem came out of the basement into the demarc box via copper wire. FTTH replaced cable but uses the same copper wire. FWIW, the local telco has been replacing copper all over the place so even telco land line service is FTTH (even in the most unlikely, extremely-low population density areas). I believe they take the old copper line when they installed FTTH.

What doesn't help is that the box is some 8' off the ground and it's more than uneven/unlevel enough (in 2 planes at that) that one can't get a ladder securely to work up there for long. All phone receptacle wiring in the house go to this block.
I smile when I see container ships sailing past my house laden with stuff made in China

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