Telephone wiring

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DorothyMacaw:
Hi

My landline phone is DOA. The phone company checked the line and said it is working up to the house, so there must be a short inside.

The house is 85 years old so there is a rat's nest of wires under the house where the spiders live.  only really need one phone hooked up, since I use my VOIP for all my calls. The landline is only used for a listing in the phone book. All calls to it go directly to the answering machine.

So ..... with my multi-meter in hand how many volts am I expecting to see on the incoming line ?

Then ....... how do I figure out which of the wired pairs go to the specific phone with the answering machine on it ?

 - Thank you - Dorothy

poppo:
Instead of trying to explain it all, you might want to read this.

http://www.wire-your-phones.com/

But typically the green/red lines are used for the primary line. When everything is working, you will typically measure 48V dc across the line. But that voltage will drop to about 6V if a phone is off hook. Sometimes it's best to just run a new line to the entry point. The picture below shows a modern enty point box. The part onthe left is where the phone company line comes in. The bare wires you see are the lines going into the house. So what the phone company does is unpug that phone jack at the top and plug in their head set. If they get a dial tone, they know thier lines are good. Note: this particular box is using cat 5 cable and a blue pair. Any pair of wires is ok as long as you use the same pair in the house.

brichter:
-48VDC (note that's negative).

Tip and Ring should be green and red, tip is the positive (ground) and ring is the negative (battery, or supply) from the CO.

poppo:
Quote from: brichter on December 28, 2010, 08:41:27 PM

-48VDC (note that's negative).


This is true, but polarity is not important for most modern phone equipment. The important thing is to actually have the voltage to know the line is working. But it never hurts to have it 'right'. 

Brianzz:
I would go back behind the phone company and make sure it's working at the box. There should be a test jack on the box outside your house.. plug a phone in it to see if you can get a dial tone, if not give them a call back and tell them you got nothing at the box, it's their problem.

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