How to identify Cat5 wiring in patch panel (when live)


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Old 01-07-08, 03:02 PM
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How to identify Cat5 wiring in patch panel (when live)

I want to convert some of my phone lines to data lines.

I moved into a house that has all the phone jacks (RJ11) wired with Cat 5e to a panel in a bedroom closet. All the cables are attached to a punch block, with 8 wires (4 pair) running criss-cross along the whole thing to wire them in parallel.

I'd like to replace some of the wall phone jacks with RJ45 keystone jacks, and then terminate those wires to an RJ45 patch panel.

Problem is, the phone system is live (activated by the phone company) and I have no idea which wires in the junction box run to which rooms.

I have an RJ45 cable tester (signal box on one end and receiver box on the other end with LEDs for each pair). Is there a way to test the wires without disconnecting them from the punch block? (I can't figure out how to pull them from the block without cutting the wires and destroying the whole thing).

I guess I could just pull the whole thing out and redo all of the phone wiring on a new punch block, but that's extra time and money, versus just pulling the 4 rooms that I'm interested in for the RJ45.

TIA.


(Fortunately all of the RJ6 was labled. But that's easy enough to disconnect and test anyways.)
 
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Old 01-07-08, 03:25 PM
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You won't be able to ID them while they're connected in parallel. Unfortunately you'll have to pull them off the block to isolate the pairs.

Then again, since you're buying an RJ45 patch panel anyway, you could just put all of the field wiring into the patch panel. The blue pair becomes your phone line, and the green & orange pairs are your data lines.
 
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Old 01-07-08, 11:38 PM
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Originally Posted by Rick Johnston
Then again, since you're buying an RJ45 patch panel anyway, you could just put all of the field wiring into the patch panel. The blue pair becomes your phone line, and the green & orange pairs are your data lines.
Since I'm planning to set up a home server, I'd like 100baseT, so I'll need all 4 pairs for the data.

I'm thinking of making a custom cat5 cable by cutting out the blue pair. I'll connect my tester using this cable. That way I can test the wires while still leaving the phone line connected (the tester will just show the blue pair as disconnected).
 
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Old 01-08-08, 04:07 AM
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I misunderstood the quoted line below to mean that all four pairs were connected. If you have open pairs you can short one at a time and use a multimeter set to ohms to read which one is shorted.

All the cables are attached to a punch block, with 8 wires (4 pair) running criss-cross along the whole thing to wire them in parallel.
 
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Old 02-14-08, 02:19 PM
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With a good signal tracer and buttset (rather than a cable checker) you can determine which cable goes where and what wire does what. There are adapters that allow you to "piggyback" onto a 110 or 66 block that would provide access to each of the eight wires without removing them from the block. This can all be done while connected to a live phone line.

Inject a signal onto each 4 pair cable and trace the tone with a probe to a particular room. The buttset will also give you an indication as to those pair(s) which provide the phone connection (through a "banjo" adapter) and those that do not (do not assume the previous "technician" used the standard color sheme -- TEST IT!). After all, the cables aren't labeled (first clue as to the professionalism of that "technician") or you wouldn't be tasked with this project.

Keep good notes and label each cable (which should have been done by the previous "technician"), then connect the 4 pair cables from those rooms where you want data to your patch panel, following industry-standard practices (1/2" unjacketed wire lengths, color schemes, etc.).

Whether to use a coloring scheme from EIA/TIA 568A or 568B is your choice. Residential is usually 568A. Keystone jacks usually have both color schemes on them. Most patch panels I've seen are 568B, however. Let the patch panel scheme be your guide.

You can use some of the unused wires from the 4 pair data cable for a phone line and attach a jack to them. Doing so runs the risk of crosstalk on the remaining data wires by eliminating the "shielding" provided by those wires when injecting a signal onto them for phone use when they're only intended to create an induced magnetic field by their proximity to the original data wires within the cable.

Splitting pairs like that is asking for trouble, but it's been done successfully by many people with no observed ill effects. The ill effects are definitely there, but may not be noticeable with even a 100BaseT signal. 1000BaseT will suffer a degradation, so if you intend to upgrade to Gigabit soon, don't connect a phone line into the data cable.

A purist wouldn't do it on even a 100BaseT cable, but a practical person will. It depends upon what side of the fence you reside as to whether you'll accept the risk. The System Engineer in me wouldn't split pairs.

It's a lot easier to do the things I've written than expressing them in writing, so I hope I managed to properly convey my ideas in printed form. My apologies if my writing skills aren't up to the same degree as those of my wiring. I've been trained by Cisco for wiring, but have no formal training with writing, hehehe.

Good luck and have fun!
 
 

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