Miswired Cable Works?
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Posted by glen herrmannsfeldt on September 20, 2005, 12:52 am
Please log in for more thread options David Lesher wrote: > At one end, the blue-white is punched down where the white-blue
> should be and vice versa. 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 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Posted by Phil Partridge on September 20, 2005, 9:46 am
Please log in for more thread options >David Lesher wrote:
> > >>>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. >
>> At one end, the blue-white is punched down where the white-blue
>> should be and vice versa. >
Only the Orange and Green pairs are used for 10/100 Ethernet, so you do
>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 > 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 philp@pebbleGRIT.demon.co.uk Remove the grit to reply | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Posted by glen herrmannsfeldt on June 25, 2006, 5:42 am
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Phil Partridge wrote: (snip) > 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. 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 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Posted by Robert Redelmeier on May 10, 2005, 4:35 pm
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> I went to new customer's office yesterday to identify and
> label the data cabling installed (but never used) by the > previous occupant. EVERY cable was miswired, with ALL > pairs reversed at the patch panel. 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 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Posted by Dmitri(Cabling-Design.com on May 10, 2005, 4:51 pm
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Michael Quinlan wrote: > I went to new customer's office yesterday to identify and label the
> data cabling installed (but never used) by the previous occupant. > EVERY cable was miswired, with ALL pairs reversed at the patch panel. > The problem was easy enough to identify and correct, however, I'm
> baffeled by the fact that the (5) PCs they had already connected using > the installed cabling were working! Out of curiosity, I check some > (but not all) of the patch cables they were using, and they were all > passed a wiremap test. > I know that current hardware will detect and compensate for
> straight-through and cross-over wiring, but I've never heard of > auto-correcting for reversed pairs. > Anyone got an explaination for this one!?
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. -- Dmitri Abaimov, RCDD http://www.cabling-design.com Cabling Forum, color codes, pinouts and other useful resources for premises cabling users and pros http://www.cabling-design.com/homecabling Residential Cabling Guide ------------------------------------- ##-----------------------------------------------## Article posted with Cabling-Design.com Newsgroup Archive http://www.cabling-design.com/forums no-spam read and post WWW interface to your favorite newsgroup - comp.dcom.cabling - 1984 messages and counting! ##-----------------------------------------------## | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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>>what colour the wires are, so long as proper pairing is maintained.