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Standard User BatBoy
(sensei) Fri 28-Oct-16 10:33:15
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Re: How do OR know which white wire is which?


[re: Eeeps] [link to this post]
 
In reply to a post by Eeeps:
I can understand how a tone generator might confirm a particular wire end to end but can't see how it can be used to confirm the pairing.
Because you put it across a pair
Standard User Zarjaz
(eat-sleep-adslguide) Fri 28-Oct-16 10:41:35
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Re: How do OR know which white wire is which?


[re: TheEulerID] [link to this post]
 
Any telephone technician getting it wrong would have to do so at both ends in the same way.

The definition of a rectified split pair. Also colloquially known as 'leg and leg'.
I'd never say it could never happen, but I would think it rather rare.

I've come across it maybe three times in 20 years.

Standard User Zarjaz
(eat-sleep-adslguide) Fri 28-Oct-16 10:47:04
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Re: How do OR know which white wire is which?


[re: BatBoy] [link to this post]
 
In reply to a post by Eeeps:
I can understand how a tone generator might confirm a particular wire end to end but can't see how it can be used to confirm the pairing.
Because you put it across a pair

But he's right, just using a tone doesn't ensure the two legs are a pair.

Is there any field equipment that can measure crosstalk between pairs?

Not as such, you have to have a live circuit down the pair and see how that circuit 'looks'.

The 'pair quality' tests Openreach runs check for A/C balance, if this is low it may be an indicator of a split pair .... but can be other things as well, an HR, a non twisted (but still a) pair.


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Standard User BatBoy
(sensei) Fri 28-Oct-16 10:53:16
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Re: How do OR know which white wire is which?


[re: Zarjaz] [link to this post]
 
It does if it's a known pair at one end. As already posted by someone, you short them together at the other end and the tone stops.
Standard User Zarjaz
(eat-sleep-adslguide) Fri 28-Oct-16 11:54:05
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Re: How do OR know which white wire is which?


[re: BatBoy] [link to this post]
 
It does if it's a known pair at one end.

IF

In the OP's link That's not how the pairs look in the real world, he has added those 'cat5' twists himself.

Even then he may have made a mistake and split the legs as he has stripped the cable back and twisted the pairs. (Which he should not have been tampering with.)

As already posted by someone, you short them together at the other end and the tone stops.

Yes, I know.

Standard User BatBoy
(sensei) Fri 28-Oct-16 12:02:04
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Re: How do OR know which white wire is which?


[re: Zarjaz] [link to this post]
 
In reply to a post by Zarjaz:
In the OP's link That's not how the pairs look in the real world, he has added those 'cat5' twists himself.
Yes. I was hoping the other end has known pairs
Standard User partial
(experienced) Fri 28-Oct-16 17:12:46
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Re: How do OR know which white wire is which?


[re: Zarjaz] [link to this post]
 
>> And all impossible to measure.

If you know what you are looking for, a mole will pick them up.
Standard User Icaras
(experienced) Fri 28-Oct-16 18:20:29
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Re: How do OR know which white wire is which?


[re: Eeeps] [link to this post]
 
In reply to a post by Eeeps:
In reply to a post by MrSaffron:
Tone generators and failing that seeing which other wire it was twisted with.


Hopefully this link will work..

Five Pair Twists

I can understand how a tone generator might confirm a particular wire end to end but can't see how it can be used to confirm the pairing.

Is there any field equipment that can measure crosstalk between pairs?


Well because you'd hope that at one end the pair would be intact. Bear in mind that as Zarjaz mentioned if you cut the outer back and grab a white you should find its corresponding colour will come out with it as they'll still be twisted together.
Standard User Zarjaz
(eat-sleep-adslguide) Fri 28-Oct-16 18:52:05
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Re: How do OR know which white wire is which?


[re: partial] [link to this post]
 
If you know what you are looking for, a mole will pick them up.

Still tricky though, and worse still using the TDR function on the JDSU/Exfo ..... you need a proper 'old one'. wink

Standard User eckiedoo
(fountain of knowledge) Fri 28-Oct-16 18:53:04
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Re: How do OR know which white wire is which?


[re: Eeeps] [link to this post]
 
In the case of both the tone generator and my Christmas Card system, if they are not connected to the paired colour and white at the "near" end, the signal level at the far end would generally be obviously low, to anyone experienced in using such systems.

Almost absolute confirmation can then be obtained by twisting the "pair's" bared copper at one end; and going to the far end with a continuity tester, preferably one of the older, analogue meter variety such as an (ancient) AVO 8, as they actually rely upon a significant current flowing through the wires.

Additionally as others have said, if the outer-most sheath/insulation is removed at the remote ends, the twisting of the paired colour and white can be seen.

Edited by eckiedoo (Fri 28-Oct-16 18:55:42)

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