Member Avatar for mehnihma

I have one strage question,
I have one question that confuses me and not sure how to answer it

The question is:

Discuss why it is important to cross the pins in the cable. Include the functions of the pins and what problem you are trying to solve.

My answer would be:

With a crossover cable, the wires connected to Pins 1-2 on one end are "crossed over" and connected to Pins 3-6 on the far end and other way around.
Most electrical noise from the cable can be eliminated by puting twisted pairs in cables
and Cross-talk (signals leaking between wires in a cable) is also minimized.

But I am not sure is this the answer?
What do you think

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  • Latest Post Latest Post by rubberman
Member Avatar for JorgeM

"Cross-over" cables are used to connect two devices of the same type such as computer to computer or switch port to switch port. This is really the only reason to use this type of cable. 1,2 and 3,6 are crossed as you mentioned.

UTP (unshielded twisted pair) cable addresses teh electrical noise problem you mentioned by including the "twists" in the cable. this is not related to the first concept of a cross-over cable. UTP simply twists the pairs within the cable to prevent cross-talk.

so, it sounds like you are talking about two different concepts in the same answer.

Member Avatar for mehnihma

Yes I know that crossover is not releted to cross-talk

but is the question is talking about the problem? That is the only problem for which I know?

Member Avatar for JorgeM

"Cross the pins" is a very generic reference in this question.

If the question is simply referring to having the 568A scheme on one end of the cable then 568B on the other, this is generally known as a cross-over cable. The only purpose of this cross pin layout is to connect to similar devices together. No other purpose that I am aware of.

Also note that this is not the only "cross-pin" design out there. There are other pin schemes for the UTP cable/RJ-45 connector.

Member Avatar for rubberman

Another term for this (for serial rs-232 connections) is a null-modem cable. For ethernet cables, this would be called a patch cable.

Edited by rubberman
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