How could I identify the usable Cat-5 pairs in this mess of torn-out wiring?

When the previous occupants vacated my new lab space they did a number on the Cat-5 wiring that had previously been installed.

Mess of wire

The baseboard jacks at the other end of this mess appear to be okay, but how do I go about figuring out which of these torn-out wires go to which jacks? Is there a straightforward way?

The three grey cables to the right side and the one sticking down on the left are what I suspect to be Cat-5. There are a bunch of other torn-out cables which appear to be from an alarm system and some phone lines.

Kaelin Colclasure

Posted 2012-02-14T17:52:06.153

Reputation: 213

Very little of that looks like cat5. – Kellenjb – 2012-02-14T18:10:18.790

1Superuser might be a better fit that Electrical Engineering; I've asked about this in their chat room. DIY might also be an option. However, remember that not every question has a home on Stack Exchange. – Kevin Vermeer – 2012-02-14T18:29:33.160

That looks like old telephone cable, not CAT 5. Those connectors used to be common for internal telephone wiring with fairly large number of extensions. Telephone linemen have special beeper units they attach at one end then find where the tone comes out on the other end. – None – 2012-02-14T18:53:22.393

2Jacks and pairs at left appear to be PBX/telephone. Black coax may be 10base2 ethernet. Grey cable has correct colours for CAT5. Copy and paste diagram to an image viewer and you get 8 MP original. | Run single wire between ends via corridor. Plug CAT5 cable with wire end into Jack at good end. Bare cable ends. To start join all ends in one cable together and connect to corridor cable. You can now do end to end test with multimeter ohms beeper. This shows which cable is which. Now separate wires. If you have two people you can wire by wire check continuity using buzzer and return wire. – None – 2012-02-15T00:47:16.560

Connect buzzer and wire at one end to one wire and person at other end runs C.wire (corrisor wire) end over wires one at a time till beeper sounds. Once you have ONE wire identified you can use it as a return and this can eliminate CWire. eg identify which cable is which by shorting all wires in one at far end and test for short. Unshort one only at far end and go through 8 at your end with buzzer to see which has gone missing. This is now a known wire. You can remove wires one at a time and find them this way. – None – 2012-02-15T00:51:33.543

You can feed far wirs into 8 x LEDs and connect to a return wire and apply say 20 MA around loop via one wire at your end. Lit LED IDs which wires is connected. Needs two people or running to and fro | Connect 8 wires at far end to known common OR 7 to a random member of the 8 via resistors. These can be eg just std E12 series probably (1k, 1k2, 1k5) or wider apart if desired. Rmin should be >> Rcable (not hard). Summat like 1k, 1k5, 2k2, 3k3, 5k6, 10k, 15k ... should be very easily distinguished (about 50% each time) or 1k, 2k2, 4k7, 10k, 22k ... (doubled plus per time) – None – 2012-02-15T00:55:04.320

1At least there appears to be nice carpet. – CharlieRB – 2012-02-15T16:46:11.830

Apropos of nothing: I love this picture. – goblinbox – 2012-02-15T17:57:19.483

Answers

You want a two-part device called a toner. It's standard telephony equipment used to identify specific wires. You use it to put tone on one end of a wire and to listen for tone on the other end.

(Nthing the previous observation that most of that jumble of cabling isn't CAT-5; it's coax and RJ-11 and other stuff and you should probably just rip it out and install a new run.)

goblinbox

Posted 2012-02-14T17:52:06.153

Reputation: 2 414

Aha! I knew this had to be a relatively common problem with a common solution. I've ordered one of these from Amazon. Thanks! – Kaelin Colclasure – 2012-02-15T20:28:14.747

Those big connectors are for connecting multiple lines to a system such as a PBX or connecting certain switches to certain patch panels. They're probably not network cord.

The black cord that is connected is Coax, or Cable TV/Internet cord.

The grey cords do appear to be network cable, but their condition leads me to believe you're better off simply laying out cable of your own as posipiet postulates in his comment.

There is expense and then there is hassle. The hassle necessary to figure out which of these goes where seems to me to be greater than the expense of simply laying down for several long-enough network cords from your local electronics store.

music2myear

Posted 2012-02-14T17:52:06.153

Reputation: 34 957

What kind of cable is it? Are you sure it is the optimum cable you need? How long will you be in the lab space?

The cable duct seems to be accessible. If it is not cat 5e cabling, or anything recent, replace it before you fully move in. You will thank yourself for doing that if you stay longer than 3 years.

If you want to reverse engineer the whole thing, dismantle each cable for a bit, find one certain strand (they seem to be marked). Find the opposite end of the specific strands by opening the plug housings. Tie the one strand of one cable to ground, measure resistance on the other side until you find that strand. Repeat for all cables.

You could also make a multi-frequency signal generator, feed one distinct spectrum made by adding several frequencies into each strand,then walk around the house and measure the spectrum for each strand, thusly identifying the cables.

It might be viable to feed the spectrum not by adding, but by timeshare multiplex, if you have a bunch of multiplexers lying around.

posipiet

Posted 2012-02-14T17:52:06.153

Reputation:

I only expect to be here for a year, and the landlord has no interest in compensating for any improvements-- which may be why the previous occupants chose to remove their equipment the way they did. – Kaelin Colclasure – 2012-02-14T18:23:19.817

5In this case, stash the ruin into the duct, flop the cables you need on the floor, and spare your time. – None – 2012-02-14T18:24:18.613

From what I can see, it looks like the grey ones all have the standard Cat5 insulator colors orange/blue/green/brown. If you can strip the greys to the right a little, you can confirm them as well.

Of course where they come from and where they go is a whole different question, but one that you would need to figure out to determine whether or not they are usable (ie, which end to add a connector to). You could probably add a connector to each grey and then use a network testing tool to determine if it is connected to the network or to a terminal. (You can probably find one at a local computer shop or on eBay for

As for the yellow-blue spaghetti in the top-left, it’s not clear from whence they come.

Synetech

Posted 2012-02-14T17:52:06.153

Reputation: 63 242