There are 2 different cabling standards when it comes to Cat 3, Cat 5, Cat5E, Cat6 cabling:
1) 568A
2) 568B
1) 568A
2) 568B
I'm not going to go into all the details and the history behind both, but instead just give you a brief summary of how to identify each and a simple method for creating cross-over cables if necessary.
The pattern (from pin 1 to pin 8) is always Stripe, then Solid. Got that? Cool... 568A starts with Green and is (from pin 1 to pin 8): White Green, Green, White Orange, Blue, White Blue, Orange, White Brown, Brown. So... both Green, split the Orange with both Blue, then both Brown. 568B (which is more commonly found in use) starts with Orange and is: White Orange, Orange, White Green, Blue, White Blue, Green, White Brown, Brown. So... both Orange, then split the Green this time with both Blue, then both Brown. |
So, a patch cord is also sometimes referred to as a straight-through cable, meaning all the pins match on both ends of the cable so all traffic flows "straight through" the cable. A Cross-Over cable will take the Transmit pins and cross them over to the Receive pins on the other end of the cable and vise-versa. In Ethernet, this equates to pins 1 and 2 (Tx) crossing over to pins 3 and 6 (Rx).
Pin 1 to pin 3 and pin 2 to pin 6.
Pin 1 to pin 3 and pin 2 to pin 6.
Now, for a simple trick to build an Ethernet cross-over cable... Easy... just get out your cutters and crimpers and terminate 1 end as a 568A and the other end as a 568B. The resulting cable is a perfect cross-over.
Other cables, like T1/E1, 56K... yeah not so simple to make cross-overs, but here are their pinouts
T1/E1: 1 & 2 (Tx) to 4 & 5 (Rx), more specifically 1 to 4 and 2 to 5
56K: 1 & 2 (Tx) to 7 & 8 (Rx), more specifically 1 to 7 and 2 to 8
T1/E1: 1 & 2 (Tx) to 4 & 5 (Rx), more specifically 1 to 4 and 2 to 5
56K: 1 & 2 (Tx) to 7 & 8 (Rx), more specifically 1 to 7 and 2 to 8