Issues creating network from existing wiring - AVS Forum
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post #1 of 10 Old 07-08-2013, 03:41 PM - Thread Starter
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We have a 3 story home wired with 4-pair phone cabling (looks exactly like http://i.imgur.com/bqdBnYH.jpg), which is apparently also cat5?

For the time being, I only want to a connection between 2 of the jacks. I don't want a network for now -- just a single connection -- really, just an extension.

I found the central box where all the cables are connected with the outside line. The blue, white/blue, orange, and white/orange (for all the cables) were tied together. I connected the remaining green, white/green, brown, and white/brown wires together (http://i.imgur.com/xX4FHbP.jpg -- let's just ignore how bad this looks for now, unless you think this is my problem?). I've also disconnected the 6th cable from the box outside, so there shouldn't be any interference (at least from that).

I've replaced 2 (of the 5) phone jacks with cat5 jacks (http://www.lowes.com/pd_248282-60784-F3450-WH-V5_0__?productId=1070763) using T568B. The remaining 3 jacks are still phone jacks, but since nothing is connected to them, I assume it's safe to leave them.

I connected one jack to a LAN port on my router and the other jack is connected to my computer's LAN card. I only want to connect these two devices.

The computer takes a few seconds to recognize the connection, and then it only ever resolves to "Unrecognized network".

If I connect my computer directly using the same ports, I'm assigned an IP and can connect to the network/internet.

To try and diagnose this myself (since I'm missing better equipment) I took 2 longer cat5 cables and connected one end of each into said jacks (their combined length will reach each other). At the place where the two other ends touch, I cut the connectors off, stripped the wires down and tested that each colored wire (from the opposite cable) was indeed connected, and that there were no cross connections (e.g., white/blue was not connected blue). I did this using a LED light (something like http://i.imgur.com/WSkFNUH.jpg) and a 9v battery. Be nice :P

I know this is super (super) hacky, but I don't see why my computer cannot connect to my router through this setup.

All of this is well under a 100 meters, and there shouldn't be any interference that I can think of. The brightness from my LED tests were consistent.

Ideas?
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post #2 of 10 Old 07-08-2013, 05:19 PM
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Normal Ethernet pinouts on the RJ45 will use the same pairs as the phone. You need to pull out all 8 wires coming from both jacks and splice them together. Use ScotchLoc UR2 connectors or similar, keep the wires twisted as much as possible.

But yes, you're effectively creating a long, direct connection between the two rooms without an Ethernet switch in the middle. It will work, but you need to get the wiring correct...

Jeff
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post #3 of 10 Old 07-08-2013, 06:01 PM - Thread Starter
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Originally Posted by jautor View Post

You need to pull out all 8 wires coming from both jacks and splice them together.

Thanks! I can absolutely do this, but I don't understand how it ultimately changes the circuit. Is interference introduced when binding the wires like this (http://i.imgur.com/xX4FHbP.jpg)?
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post #4 of 10 Old 07-08-2013, 06:11 PM
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Generally speaking, yes.

The twists that are in each pair of wires in a cat-5 cable are in fact there for a reason, and you can lose signal quality without those twists in place.

More importantly, are you sure those are cat-5 cables you are working with? It will say on the side of the cable what type of cable it is. Depending on the age, it could be something else in the cabling which is messing things up.

Generally, when I have two wires like you have which you need to splice in the middle, I will put a RJ45 on one, and a punch down on the other, or I will put RJ45 connectors on both ends and put a cat-5e rated coupler between them.
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post #5 of 10 Old 07-08-2013, 06:30 PM
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Quote:
Originally Posted by enough View Post

...cat5?
Could be. Or could be Cat 3, or something else. You will have to check the jacket to see what it says.
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...I only want to a connection between 2 of the jacks.
OK, so think in terms of coming as close to a straight cable as you can.
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I don't want a network for now...
Well, you are going to get one whether you want it or not. You are wiring a LAN.
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I connected the remaining green, white/green, brown, and white/brown wires together...
Yep, but you only want to connect the two the cables that serve the two jacks you want to connect. The other cables are going to upset the impedance causing reflections that degrade the signal, and also act as antennas for any noise in the environment. The long untwisted ends of the pairs have a similar effect.
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...T568B.
That is fine.
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All of this is well under a 100 meters...
That would be relevant if this were a properly wired network connection. It isn't.
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Ideas?
Twist each pair back to the same pitch (twists per inch) it had when new, or as close as you can get. Only untwist as much as necessary to make the connection. Keep the length of each pair the same as the rest in the cable. Consider using b-cons (butt connectors for telephone wiring available at your local home improvement store) to connect the wires. Or consider terminating each cable with a 8p8c plug and joining them with an appropriate cable extender/joiner, or a plug on one and a jack on the other.
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post #6 of 10 Old 07-08-2013, 06:32 PM
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Quote:
Originally Posted by enough View Post

Thanks! I can absolutely do this, but I don't understand how it ultimately changes the circuit. Is interference introduced when binding the wires like this (http://i.imgur.com/xX4FHbP.jpg)?

Yes, it simply won't work. Having all the other leads connected create "echos" and other poor electrical conditions that will trash the Ethernet signal. Ethernet over category cable is a point-to-point system - it must be a single wire from one end to the other, without other drops or dead ends...

Pull all 8 colors from those bundles (which are a "bus" connection that is fine for the phones) for the two jacks in question, and make splices to join those two into a single point-to-point connection.
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post #7 of 10 Old 07-08-2013, 06:39 PM
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Quote:
Originally Posted by enough View Post

Is interference introduced when binding the wires like this...
It isn't created, but it makes the cable much more susceptible to picking up whatever interference is in the environment.
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post #8 of 10 Old 07-08-2013, 08:25 PM - Thread Starter
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Wow. Thanks for the clarification!
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Keep the length of each pair the same as the rest in the cable.

What would be the effects of different-length pairs? Lower throughput? An inability to connect altogether? I assume the NIC must errorcorrect to some degree.
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Having all the other leads connected create "echos"...

I'm surprised. I would have thought only fiber would do this.
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post #9 of 10 Old 07-08-2013, 08:38 PM
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Quote:
Originally Posted by enough View Post

What would be the effects of different-length pairs? Lower throughput? An inability to connect altogether? I assume the NIC must errorcorrect to some degree.

More an issue in Gigabit Ethernet and other multi-pair use cases, but a good practice nonetheless. The technology can deal with this to a degree, but "bad enough" and you'll probably just not get it to work - but we're talking really off, not a few mm or cm's... But as you should normally be cutting wire, stripping and splicing from the same lengths anyway, it's not normally a problem.
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I'm surprised. I would have thought only fiber would do this.

Electrical signals bounce of the ends of wires and reflect back, causing all kinds of grief. It's an effect used for measuring the length of cables, too. See "Time Domain Reflectometer". This is not an issue for fiber optics because the transmission is unidirectional - there's a pair of fibers (send/receive) for most communications systems...


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post #10 of 10 Old 07-08-2013, 10:41 PM - Thread Starter
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Quote:
Originally Posted by jautor View Post

Electrical signals bounce of the ends of wires and reflect back, causing all kinds of grief.

I assume this was my (biggest) issue. I've disconnected everything and re-spliced the two ends for now -- it works like charm. I'll clean things up a bit more when I get time.

The cable is CAT3.

You guys were a ton of help. Thanks!
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