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View Full Version : Can anyone explain why wire order makes a difference in line?


Breadfan
08-17-01, 09:09 AM
I recently had trouble networking an HP 4100TN network printer. Turns out the problem was how I crimped the lines...they wires weren't in correct order.

I crimped it:

White orange
Orange
White blue
blue
white green
green
white brown
brown

I was then told that the correct order was:
white orange
orange
white green
blue
white blue
green
white brown
brown.

I recrimped them in this order and the printer worked fine.

However it raised a few questions. The cables are all bunched together in the line, so how can there be crosstalk one way, but no cross talk with a different order? One would expect that if you used the same order on each side, you'd have continuity through the line and therefore it would. Obviously this is not the case, but can someone explain the scientific reason why this will not work and why this particular order must be used?

Also, someone else had done the otehr lines. One line is even longer than mine, and crimped in the order I was going to do it...and they all work fine. So why did the printer not work in that order but the computers do?

So I'm happy it works, but to be honest, I don't understand the science behind wiring the lines a certain way to make them work....one things that throws me off is the fact that other lines already existing in the office are NOT wired that way, yet they do work. So a lesson in network line science may be in order :)

Mike

Shep
08-17-01, 10:45 AM
I have been told it has something to do with how tight the pairs are twisted, and of course the order has to match at each connector.

Kingslayer
08-17-01, 12:55 PM
I explained it in my answer to your original post on this printer. Turns out I was right too.

Keeping the lines paired up when it comes to the incoming and outgoing stop cross talk between the lines. The signals can interfere with each other, cause packet loss, and signal degredation. (Chances are you were seeing both, and that is why the printer would puke) Wrapping them stops this.

Plenum rated cable also helps stop outside interference like AM and FM, TV signals, and electical wires.

The computers may still worked although wired wrong because of distance. If they are longer and still work is probably because there is a hub somewhere in the line, which will act as a repeater. Computers will also resend the data until it is all recieved, printers will not. If the original signal is corrupt to a printer it will just not print or not print properly.

That is why you will see packet loss on a computer and still recieve the data. The sending computer will resend it. This doesn't work with printers.

And just for FYI...

The color schematic that I put on your original post is for normal cables to make a crossover, make one end like that and the other end will be...

White Green
Green
White Orange
Blue
White Blue
Orange
White Brown
Brown

This will also keep the pairs together and stop line interference and crosstalk on crossover cables.

pii100
08-18-01, 01:28 AM
okay here is a simplified explanation if you have a negative and posotive they cancel out that is why the color pairs are twisted together (so they can cancel out each others emi(electro magnetic interference)) the reason that the order matters is that you have to enshure that the posotive and negative end up on the same pair ethernet uses pin one +transmit pin two -transmit pin three +recieve pin six -recieve also ethernet is very sensitive to cross talk that is why you pretty much have to use at least cat5 (and no cat3 wont work)

netnic30
08-19-01, 09:43 PM
if so these are generally not good for the reasons stated in the prior posts. any good shielded cable will do Belkin makes almost any sort that you can think of and they are end to end tested as well.

pii100
08-19-01, 11:58 PM
just noticed this in your post kingslayer plenum rating refers to the fact that the cable is rated for use in plenum space (fire codes) which means you can use it in a space that the airconditioner uses as a air return path (most drop ceilings) the actual difference is that non plenum emits toxic smoke when it burns plenum rated dose not. i beleive you meant to say stp (sheilded twisted pair)

Kingslayer
08-20-01, 01:19 PM
You're right pii200. I was confused. Plenum rated is the toxic smoke protection.

Either way, I'm glad you got your printer working Breadfan.

Breadfan
08-21-01, 06:35 PM
Thanks alot for the replies guys....very helpful and informative info...

Sorry for the delayed response, I just got my modem back working since I wiped my drive and reinstalled everything fresh...also, I'm taking the week off of work...WOHOO!

Mike