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Cat 5 Cable Standards

Straight-through and crossover cables revisited by phuzzy42
Posted: 28 Dec 05

Getting the right color wire to the right pin in a connector can be confusing.  Hold the connector with its clip facing down and with the cable opening facing you.  The leftmost pin is pin #1, then pin #2, and so on.

Most CAT5 and CAT6 is wired using the EIA/TIA 568B standard.  Regardless of whether you use 568A or 568B,  straight-through cables connect the same pin numbers together on each end of the cable - pin #1 on one end goes to pin #1 on the other, pin #2 to pin #2, etc.  Crossover cables swap the positions of the orange and green pairs on one connector so the transmit on one end goes to the receive on the other and vice versa - one connector is wired using 568A and the other uses 568B.

The chart below shows which color wire goes to which connector pin on each end of a cable.

CODE

   EIA/TIA 568B           STRAIGHT-THROUGH           EIA/TIA 568B

1  Orange/White ------------------------------------ Orange/White  1

2  Orange ------------------------------------------------ Orange  2

3  Green/White -------------------------------------- Green/White  3

4  Blue ---------------------------------------------------- Blue  4

5  Blue/White ---------------------------------------- Blue/White  5

6  Green -------------------------------------------------- Green  6

7  Brown/White -------------------------------------- Brown/White  7

8  Brown -------------------------------------------------- Brown  8



   EIA/TIA 568B               CROSSOVER              EIA/TIA 568A

1  Orange/White ----------------+   +---------------- Green/White  1
                                 \ /
2  Orange ------------------+     \  +--------------------- Green  2
                             \   / \/
3  Green/White ---------------\-+  /+--------------- Orange/White  3
                               \  /
4  Blue ------------------------\/-------------------------- Blue  4
                                /\
5  Blue/White -----------------/--\------------------- Blue/White  5
                              /    \
6  Green --------------------+      +--------------------- Orange  6

7  Brown/White -------------------------------------- Brown/White  7

8  Brown -------------------------------------------------- Brown  8

Keep these things in mind to make your cabling more reliable:

*  Keep the twists in the wires as close to the pins as possible to reduce noise and crosstalk.
*  Be careful how tight a turn around corners the cable takes - no sharp bends and no kinks.
*  Don't let people walk on the cable or put anything heavy on it. No pinching!
*  Keep cable at least 3' away from electrical wires if they run parallel to each other.
*  When bundling several cables together, it's better to use velcro instead of wire ties.

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