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Cat 5 Cable Standards

I want to know how to make straight through and crossover cables. by Kyusaku
Posted: 17 Sep 01

Presented below are the two current standards for todayÆs cable pin outÆs.  The EIA/TIA 568B also referred to as the AT&T 258A, and the EIA/TIA 568A.  Also included are the pin outÆs for the crossover portions.  

EIA/TIA   568B - Straight Through (Widest used standard)

Pins
1.) Orange/White = Tx (+)            
2.) Orange     = Tx (-)
3.) Green/White     = Rc (+)
4.) Blue        
5.) Blue/White
6.) Green     = Rc (-)
7.) Brown/White
8.) Brown

Tx=Transmit  Rc=Receive
(Pins 1, 2 belong to pair 1 which is Orange/White, Orange.  Pins 3, 6 belong to pair 2, which is Green/White, Green.)

EIA/TIA   568A - Straight Through

Pins
1.) Green/White     = Tx (+)                
2.) Green     = Tx (-)
3.) Orange/White = Rc (+)
4.) Blue
5.) Blue/White
6.) Orange     = Rc (-)
7.) Brown/White
8.) Brown

Tx=Transmit  Rc=Receive
(Pins 1, 2 belong to pair 2, which is Green/White, Green.  Pins 3, 6 belong to pair 1, which is Orange/White, Orange.)


EIA/TIA   568B - Crossover

Pins
1.) Green/White     = Tx (+)                
2.) Green     = Tx (-)
3.) Orange/White = Rc (+)
4.) Blue
5.) Blue/White
6.) Orange     = Rc (-)
7.) Brown/White
8.) Brown

Tx=Transmit  Rc=Receive
(Pins 1, 2 belong to pair 2, which is Green/White, Green.  Pins 3, 6 belong to pair 1, which is Orange/White, Orange.)


EIA/TIA   568A û Crossover

Pins
1.) Orange/White = Tx (+)            
2.) Orange     = Tx (-)
3.) Green/White     = Rc (+)
4.) Blue        
5.) Blue/White
6.) Green     = Rc (-)
7.) Brown/White
8.) Brown

Tx=Transmit  Rc=Receive
(Pins 1, 2 belong to pair 1 which is Orange/White, Orange.  Pins 3, 6 belong to pair 2, which is Green/White, Green.)

To produce the cable you want, use the standard in your area. (Being the color coding on other cables...most likely 568B.) For a straight through (going from computer to hub) use say 568B on both ends of the cable.  For a crossover (cascading hubs and switches lacking a MIDX switch OR computer to computer without a hub...peer-to-peer) Use 568B on one end and 568A on the other.  Studying the FAQ will bring an understanding of this idea.

Notice anything interesting? For a crossover cable, you are merely swaping standards on the cable, 568B on one end and 568A on the other. For all other "straight through" choose the standard that is in use were you are and use it to make your cables. The staple standard that I have seen the most is 568B, which is why I placed it first.  In your area it may be 568A, which ever it is, a good rule of thumb is to stick with one standard and use it!  I hope this helps.

Mark R



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