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Which cable goes where?
adrian wyatt Oct-02-00 11:43 AM
Hi I've just installed two computers into a building which has category 5 cable going to RJ45 sockets all over the building - brilliant! Except when the last people moved out they just cut off the connectors at the hub end and there are no labels on the wires. So I have about 30 cables in a bunch and 30 sockets and I want to use 5 or 6 for the new network. Is there an easy way to test which one goes where?

1. RE: Which cable goes where?
lbyard Oct-02-00 03:24 PM
In response to message 0
Good grief! Now, how would I do it… If I didn’t have a tester, which I do have… Ok, first I would disconnect one of the wall plates see how one of the jacks is wired. They should be wired to the 568A or 568B EIA/TIA standards (http://duxcw.com/digest/Howto/network/cable/cable5.htm), probably the 568B standard (the same as the ATA&T 258A standard, which is very common in the US). If you are lucky the jacks will be color-coded and easily deciphered. You are going to need this info anyway to put plugs on the other end of the lines. I would then cut a short length of CAT 5 cable, put a plug on the end to correspond to the color code used by the jacks, short-out a pair, and plug it into a jack to be traced. I would then go to the cut-off ends, strip enough of the outer jacket to get at the wires and strip a little bit of insulation off the same pair, and perform a continuity check. That is, determine which of the 30 wires has the pair shorted. A multimeter (use ohms) or a cheap continuity checker (one with a battery; many have audio-out), probably available at Radio Shack, can used be to do it. A continuity check will not necessarily prove that the lines are good at network frequencies. Larry

2. RE: Which cable goes where?
Pineapple Oct-02-00 07:10 PM
In response to message 1
Could I just add a little to that?

If you do have an ethernet cable tester, don't be tempted to put the tester on one end (instead of shorting), and a multimeter on the other, as the multimeter might put out a current which could damage the ethernet tester.

3. RE: Which cable goes where?
adrian wyatt Oct-04-00 10:27 PM
In response to message 2
Thanks for that. I've made eight little RJ45 plugs with 6 inches of cable and the blue/browns wound together and i've plugged them in the 8 sockets I want to use. I've also made a simple light bulb circuit using a kit I got for my kids a few years ago. If the bulb lights up I'm on to a winner! Tomorrow I'll finish checking the rest of the cables - thanks once again - brilliant forum.

4. RE: Which cable goes where?
lbyard Oct-05-00 06:02 AM
In response to message 3
LAST EDITED ON Oct-05-00 AT 06:05 AM (GMT)

Just plug-in one at a time so you will know which cable is which. If you plug-in all eight at the same time you will only know that you have found one of the eight cables and not which of the eight it is. On the other hand, since you have already made the plugs, with your method you only have to go though all of the cables once, set aside the 22 you are not interested in, pull one of the plugs, and mark the one of the eight that no longer lights-up. Larry

5. RE: Which cable goes where?
technut Oct-05-00 04:08 PM
In response to message 3
>Thanks for that. I've made eight
>little RJ45 plugs with 6
>inches of cable and the
>blue/browns wound together and i've
>plugged them in the 8
>sockets I want to use.
>I've also made a simple
>light bulb circuit using a
>kit I got for my
>kids a few years ago.
>If the bulb lights up
>I'm on to a winner!
>Tomorrow I'll finish checking the
>rest of the cables -
>thanks once again - brilliant
I was going to reccomend the lightbulb trick my personal favorite just keep it low voltage and don't send the juice through a switch.

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