Shielding In Pair Cables Not In Core Cables..?

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mohsinhamid Commentator Join Date: May 2011 Posts: 91	Shielding In Pair Cables Not In Core Cables..? 10/30/2012 11:36 PM
	I have seen in pair cable, a copper shield is present in every pair of the 5 pair,12 pair cables and it is grounded.... but not in the core cables.....???? please explain me clearly why shield is used in pair not in core cables....
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: shielding in pair cables not in core cables..? 10/31/2012 4:16 AM
	To minimise the risk of inductive pick-up on analog circuits. A current loop is usually immume, however, were a loop using voltage as a transmission method, shielding the pair increases the immunity to spikes and surges happening in nearby cables. It isn't necessary in multicore cables as these are often used to carry digital signals, which are usually immune to spikes and surges anyway. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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G.K. Guru Join Date: Mar 2007 Location: Greece / Athens Posts: 722 Good Answers: 28	#2 Re: Shielding In Pair Cables Not In Core Cables..? 11/01/2012 3:52 AM
	In pair cables, the wires are twisted pairs, i.e. they carry differential signals. Such twisted pairs have the advantage of low electromagnetic (e/m) radiation and high e/m immunity (you can find in Wikipedia and several other sites how this is done). So, such wires must be routed together tightly without any shileding between them (in order to operate properly as "twisted pairs"). However a shielding around both of them improves further their e/m emissions and immunity issues and, also, reduces the crosstalk from the other twisted pairs (located in the same cable). __________________ George
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Chankley Power-User Join Date: Sep 2007 Location: South coast of England Posts: 411 Good Answers: 36	#3 Re: Shielding In Pair Cables Not In Core Cables..? 11/01/2012 1:29 PM
	A common arrangement is for the power cores to be unscreened in the centre and screened signal/data cables around the outside.
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Chankley (1); G.K. (1); PWSlack (1)

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