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Help, what color wires do I use from a CAT5E cable for a regular phone

Last response: in Networking
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August 22, 2012 8:47:44 PM

Hi all,
I have a CAT5e cable coming into my new Atp. from ATT, the phone jack was cut off and I need to install a new one, but the wire coming into my Apt. is a Cat5e cable, just a standard 4-wire phone line.

Can you tell me what colored wires are suppose to be used in the regular Phone jack that only hold Red/Green and Yellow/Black out of the 16 wires the CAT5e cable has?

My DSL modem only has a standard phone jack input so I have no choice as far as jacks are concerned.


I can not get into the ATT box to find out which are being used... and when I call ATT they want $100 for a chump to come out and look for me. yeahhhhhhh thats not happening.


Thanks again all!
August 22, 2012 11:54:37 PM

I do not believe there is a standard for that, so either try one part at a time and test with a phone, or check each pair with a volt-meter to see which one has AC voltage on it.
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August 23, 2012 4:22:56 AM

Because I just have Data and no actual "phone" service... there is no Dial tone. I had the same setup at my other place.
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August 23, 2012 11:49:19 AM

Are you sure you cannot get into the ATT box. It is common for them to allow you into part of the box. All you will find basically is a jack that your inbuilding wiring plugs into. The theory is if you plug a phone into that jack and it works it proves it is not the phone companies issue. Of course apartments may be different.

When you say you have 16 wires. Do you have 2 cables with 8 wires each or a single cable with 16. If it is 2 cables then it is more than likely only one of these goes back to the demarc and the other is cabled to another jack in your apartment.

If it is one large cable then this cable more than likely feeds multiple apartments....so you can tap your neighbors phone.

Still with only 8 pair you should be able to just keep testing until you get it to work. I would try the blue/bluewhite pair first. This is the middle pair in a rj45 jack and is commonly used for voice application.

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August 23, 2012 1:57:59 PM

bill001g said:

When you say you have 16 wires. Do you have 2 cables with 8 wires each or a single cable with 16. If it is 2 cables then it is more than likely only one of these goes back to the demarc and the other is cabled to another jack in your apartment.


The OP said it's cat5e.

bill001g said:
If it is one large cable then this cable more than likely feeds multiple apartments....so you can tap your neighbors phone.

Still with only 8 pair you should be able to just keep testing until you get it to work. I would try the blue/bluewhite pair first. This is the middle pair in a rj45 jack and is commonly used for voice application.


Cat5e is 4 pair (8 wires).

@OP, the use of cat5 for phone systems tends to be arbitrary. As stated, use a multitester to see which wires have voltage on them. There should be at least two. Connect these to the inner pair of pins on the jack or if splicing to the phone wire, use red/green. If that doesn't work, use yellow/black..
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August 23, 2012 6:42:22 PM

bill001g said:
Cat5e only refers to the characteristics of the wire. We use cables like this all the time when building patch panels, there is no way to infer the number of pairs.

http://www.alibaba.com/product-gs/218705908/200_pairs_c...


Learn something new every day. Thanks for the information and apologies to the OP for the disinformation.
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August 23, 2012 8:48:44 PM

Thanks all for the info, i'll start testing with my voltmeter.... any idea how much voltage I should be looking for? 1-5V? Reading AC seems to have a little fluctuation even when the wires are not even connected... always a little bit of noise.
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August 23, 2012 9:14:26 PM

integraoligist said:
Thanks all for the info, i'll start testing with my voltmeter.... any idea how much voltage I should be looking for? 1-5V? Reading AC seems to have a little fluctuation even when the wires are not even connected... always a little bit of noise.


A lot more than 1-5 volts. 48volts is the norm but I forget if that is onhook or offhook. You should see more than 5-10 volts.



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