Telephone wiring

[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]

-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.

[jay]

Usually (not always) there is a RJ11 from the house plugged into the test jack.
And you need to unplug this to plug in a phone.
The reason for this is that when you remove the RJ11 and plug in your phone its just that one phone connected to the outside line.
This is the best test - if its dead its the phone company problem.

If the test jack is open this means that the wires are still connected to the house.
If the test jack is dead it may be indicitive that there may be a short.
if so you need to remove the wires going back to the house - this should be as simple as loosing two screws and taking off the wires.

If the jack is still dead its the phone company problem.
If it magically comes alive start disconnecting phones in the house as one of them has probably gone bad.

[poppo]

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.

It sounds like that is what they already did.

The phone company checked the line and said it is working up to the house

But it never hurts to double check.

[brichter]

-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'.  

Unlike many voltmeters that are still around... 

[Neonkiss]

-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.

But that becomes 90 volts during a ring.
I do remember and old story about that, so I searched the net and found it. Enjoy 



"An elderly lady phoned her telephone company to report that her telephone failed to ring ...

when her friends called - and that on the few occasions when it did ring, her pet dog always moaned right before the phone rang. The telephone repairman proceeded to the scene, curious to see this psychic dog or senile elderly lady.

He climbed a nearby telephone pole, hooked in his test set, and dialed the subscriber's house. The phone didn't ring right away, but then the dog moaned loudly and the telephone began to ring.

Climbing down from the pole, the telephone repairman found:

   1. The dog was tied to the telephone system's ground wire via a steel chain and collar.
   2. The wire connection to the ground rod was loose.
   3. The dog was receiving 90 volts of signaling current when the phone number was called.
   4. After a couple of such jolts, the dog would start moaning and then urinate on himself and the ground.
   5. The wet ground would complete the circuit, thus causing the phone to ring.

Which demonstrates that some problems CAN be fixed by pissing and moaning."

[brichter]

Actually, the -48VDC does not become 90 volts during a ring event, 90 VAC is added to the line. Some CO switches remove the -48VDC during the ring, many do not.

It's not very likely you'll ever see the ring voltage when you're measuring the battery voltage since the ring voltage is AC. Some of the more sensitive analog meters will give a little shake of the needle since the frequency standard for the US is 20Hz, but most won't even let you know it's there. Keep in mind, 90VAC is NOTHING to fool with, so the best thing to do when working on your phone line is to take one phone off the hook, the CO won't send ring voltage if there's an offhook phone on the line

[knagl]

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

See if you can beg, borrow, or steal a "Fox and Hound" (or "tone and probe") device.  It's a two-part device -- one sends out a tone signal, the other receives the tone signal.  You plug in the tone generator to the jack where your answering machine is plugged in, then you probe around the "rat's nest" with the probe until you hear the tone signal and can isolate it down to a specific pair of wires.

[brichter]

Most likely there's only 1 pair of wires connected to anything, as the house is so old. How many pairs do you see going into your house at the termination point (where the wires come from the pole or the ground to your house and are connected to the wiring in your house)?

[knagl]

Agreed, only one pair into the house, but she also wanted to know how to figure out which wires go to her answering machine once it reaches the block inside her house.

[brichter]

You misunderstood my question.

How many pairs go INTO THE HOUSE from the termination point? With a house that old, there's most likely only 1 pair, and that would have to be the pair going to the answering machine.

The terminal has only one pair coming from the CO (unless someone added another phone line), and if there's only one pair going into the house, that's the only pair the answering machine could have been connected to. Multiple devices are connected in parallel to the single pair.

[Jim]

Did they run a line test from their office or did someone come out and state that the line is good into the distribution box?  I would imagine that at some point along the way your home had some upgrades to the phone system. Meaning that the inside jacks would have been converted to plug in type modular jacks opposed to the hardwired rotary phone. Usually the phone co. would re wire during that process. If not , you would have, 1) a single pair twisted black wire going from the outside box to your inside  connection near the phone. 2) next upgrade was a four conductor cable, red/green,black/yellow. red/green was used for one line (number), black/yellow was used for a second line (number). which do you have?
 Its very easy to find out which wire is bad, but even if you find the bad wire, and its not at the begining  or end of the run, its not worth trying to find where it is  broke, its easier to run a new cable from the box to the jack near the phone. a second option is: if you have the 4 conductor wire and you suspect the red/ green is bad, if the black/yellow is not being used , swap the connections to that pair.

Jim

[DorothyMacaw]

Thanks for the input.

I still haven't do this yet. Can you tell I don't want to go wrasslin' with the spiders?

The phone repairman plugged in his phone into the jack in the box and got a dial tone. So I know it works up to the house. The wire enters the house at that point and 20 feet later I see it at the junction block. Only problem ALL the wires there look the same.

O.K. I fimd the wires with the voltage (+/- 40) and that is the line in.

Now the line to the answering machine jack. I don''t have a "Fox n Hound" (Though I would love to buy a tall Vision kit) so if I take the phone off the hook will I get a resistance reading? I know there should not be any voltage but with it off the hook it should do something at the wire end.

 - Dorothy

[brichter]

Can you take a picture of the "junction block"? All the wires in the house "should" go back to the junction block.

Do you have voltage at the "junction block"?

I don''t have a "Fox n Hound" (Though I would love to buy a tall Vision kit)

 

[channelmaniac]

Before you go too crazy looking at wiring... do something simple. Check the jacks for green corrosion. You might get lucky and just need to replace the jack.

Next, check all the jacks in the house. If you find some alive and some dead then you have a bad wire in between. There are many ways to wire a house for phones. One is to take a single pair of wires and daisy chain the jacks. Another is to run wires from each jack back to the junction box. And yet another is a combination of the two.

It's easy to check to see how they did it. Are there 2 wires going to the jack? If so they are daisy chained. If you take the cover off the jacks you can see the multiple wires going into them. It's a simple thing to see. Look for broken wires.

If it all looks good then maybe you had a critter chew a wire somewhere. That would be bad, but very likely if you aren't finding any corrosion issues.

Wires should NOT be spliced unless using filled Scotchlock connectors. Filled refers to a gel that is inside to keep moisture and oxygen out of the connection. Ma Bell uses these when splicing phone wires in attics or under houses.



Twisted wires, taped wires, etc, are just asking for phone troubles. Use the filled Scotchlock connectors and all will be well.