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Author Topic: Twisted pairs  (Read 4782 times)

hake

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Twisted pairs
« on: November 30, 2009, 04:50:10 PM »
Could someone please confirm that both twists in a pair carry the signal.  I have some 2pair Cat.5E which I am going to use to connect the router to the filtered faceplate.
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oldfogy

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Re: Twisted pairs
« Reply #1 on: November 30, 2009, 05:24:23 PM »
I don't know about the signals etc, but

One of the main reasons for having a "Twisted" cable is simply to help identify a particular pair of strands in a multi core cable.
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sevenlayermuddle

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Re: Twisted pairs
« Reply #2 on: November 30, 2009, 05:31:27 PM »
Twisted pairs can be explained by use of enormously complicated maths, but not by me - I don't do complicated maths these days.

Put very simply however, if you twist two wires together then any currents induced in one wire (by interference) will also be induced in the other wire.  Equipment that uses twisted pairs is usually only interested in the differential signal between each wire of the pair, and so interference largely cancels itself out.
« Last Edit: November 30, 2009, 05:34:16 PM by sevenlayermuddle »
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roseway

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Re: Twisted pairs
« Reply #3 on: November 30, 2009, 06:52:12 PM »
Concerning the specific question, I'm not sure exactly what you mean by 'both twists in a pair'. A twisted pair carries one signal, with equal and opposite voltages in the two wires. To carry the signal from the filtered faceplate to the router's telephone input socket you only need one pair.
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orainsear

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Re: Twisted pairs
« Reply #4 on: December 02, 2009, 02:46:36 PM »
Both wires in the pair carry a signal of opposite polarity.

It's best to use one pair or the other.
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jeffbb

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Re: Twisted pairs
« Reply #5 on: December 02, 2009, 07:59:17 PM »
Hi
quote The T designates twisted pair cable, where the pair of wires for each signal is twisted together to reduce radio frequency interference and crosstalk between pairs (FEXT and NEXT)

from http://en.wikipedia.org/wiki/Ethernet_over_twisted_pair

Regards Jeff
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