T568A and T568B are the two color codes used for wiring eight-position RJ45 modular plugs. Both are allowed under the ANSI/TIA/EIA wiring standards. The only difference between the two color codes is that the orange and green pairs are interchanged.
T568A wiring pattern is recognized as the preferred wiring pattern for this standard because it provides backward compatibility to both one pair and two pair USOC wiring schemes.
The T568B standard matches the older ATA&T 258A color code and is/was(?) the most widely used wiring scheme. It is also permitted by the ANSI/TIA/EIA standard, but it provides only a single pair backward compatibility to the USOC wiring scheme.
The U.S. Government requires the use of the preferred T568A standard for wiring done under federal contracts.
What is a Straight Through Cable?
Straight-through cable is a type of CAT5 which the RJ-45 connectors at each end have the same pin out. (color code use on both ends are the same)
Straight-Through cable is also referred to as a “patch cable.” Straight-through cable is used to connect computers and other end user devices to networking devices such as hubs & switches.
What is a Crossover Cable?
A Crossover cable is a type of CAT where one end is T568A configuration and the other as T568B configuration. Pin 1 is crossed with Pin 3 and Pin 2 is crossed with Pin 6.
Crossover cable is used to connect two computers together without using a switch or hub in between
I was wondering what standard should I use 568a or 568b? And if I have already made all my ends up with 568A and LC&D documentations require 568b can I use a cross over cable?
We recommend that you use 568B and a crossover cable is not needed. Our system requires a “Straight-Through” cable, so either standard can be used. You can even have a mixed cables, some cables as 568A and some as 568B as long as all of them are “Straight-Through” cables.
However, it’s advised not to mix different color schemes because this may cause confusion.