Miswired Cable Works?

What do you mean by "reversed pairs", if not cross over? It doesn't matter what colour the wires are, so long as proper pairing is maintained.

My guess is that it worked because it was punched down as 568A and he 'saw' the colors as 568B. As long as it is 568A or 568B at each end, it will work. Just my 2 cents.

...Bob

Electrons are color blind, but they do know who their dance (twist) partners are. TIA-568A & B are side-to-side symmetrical, so it will work just fine because no pairs are split.

I'm a little surprised because Cat5+ jacks have color codes on them.

-- Robert

It is a balanced (symmetrical) signal. The hardware sees reversed signal exactly like normal. It would not be a good idea to do for an un-balanced application like RS-232, but those are EXTEMELY rare these days. Well, maybe video without a balun would be another possible un-balanced application, but I presume they do not send video over those cables either.

But I agree, sloppy work indeed.

I've seen it done - one customer had the jacks wired properly, but polarity of every pair was reversed at the patch panel.

Must have had two people working at each end when they terminated the jacks and backboard.

Worked fine for data, totally choked when they needed to use a data run for another Legend MLX telephone.

At one end, the blue-white is punched down where the white-blue should be and vice versa.

That's exactly the way this installation appeared. All the work area outlets were wired correctly, with the exception of one that had the brown pair wired to a separate voice jack. However, at the patch panel, the white-blue and blue-white were reversed, with the same problem appearing on EVERY pair on EVERY cable. The only explaination I can come up with is that the pair-separators on the punch down were labled with the pair colors, but not with individual conductor colors, and the installer had no idea which conductor went on which side of the separator.

To clarify for anyone not following this mess, the wiremap results were:

1 - 2 2 - 1 3 - 6 4 - 5 5 - 4 6 - 3 7 - 8 8 - 7

Obviously, the original installer did no testing, with the possible exception of testing connectivity between two ethernet devices.

Thanks to all for the helpful replies.

Shouldn't be a problem, as the signal is not polarity sensitive.

One thing to remember, is that the blue pair is not used for 10 & 100 Mb ethernet. All 4 pairs are used for gigabit. So you could cut the blue pair and it shouldn't affect networking.

Ah, tip & ring were crossed over on every pair!

Not good practice! But it works for ethernet because the signalling system looks for _changes_, not absolute levels.

Very typical for 110 punchdowns.

-- Robert

But can cause all sorts of interesting problems if the link is used for for telecoms or V24.

If the connectors at both ends are from the same manufacturer all that's necessary is that things are done consistently.

Plenty of simple network testers will show if this has happened.

10baseT does need the right polarity, but as far as I know it is usual for the transceivers to detect and correct it.

I know many separate transceivers with an LED polarity indicator, the only reason for having one is for marketing value. (Or for network installers to check the polarity with.)

As far as I know, all UTP ethernet either don't care or detect and correct polarity.

-- glen

Only the Orange and Green pairs are used for 10/100 Ethernet, so you do not even need the blue or brown to be punched down for it to work. That does NOT mean it is correct if they are not! And, to the pedants, I do know about 100VG which uses all the pairs, but it is *almost* extinct. Phil Partridge snipped-for-privacy@pebbleGRIT.demon.co.uk Remove the grit to reply

(snip)

The polarity in question is for a given pair. That is, exchanging orange and orange/white for example. Transceivers detect and correct for it.

-- glen