T568B

T568B is one of two wiring schemes defined by the Telecommunications Industry Association (TIA) under the ANSI/TIA-568 standards for terminating twisted-pair Ethernet cabling with eight-conductor RJ-45 connectors. The scheme specifies a fixed color sequence for the eight conductors in a terminated cable, enabling consistent performance for Ethernet networks using category cables such as CAT5e and CAT6.

Pinout and color sequence: 1 White/Orange, 2 Orange, 3 White/Green, 4 Blue, 5 White/Blue, 6 Green, 7 White/Brown, 8 Brown. In this arrangement, pairs are orange on pins 1 and 2, green on pins 3 and 6, blue on pins 4 and 5, and brown on pins 7 and 8. This defines a straight-through wiring when both ends use the T568B scheme.

Usage and compatibility: T568B is widely used in the United States for commercial and office networking, and it is compatible with modern Ethernet standards such as 100BASE-TX, 1000BASE-T, and higher over CAT5e, CAT6, or CAT6A cables. It is commonly used alongside T568A in various installations. A cable wired with T568B on both ends is considered a straight-through patch or horizontal cable, whereas a mix of schemes (A on one end, B on the other) creates a crossover connection, historically used to connect similar devices directly.

History and scope: The T568 standards define termination schemes for RJ-45 connectors and relate to broader TIA-568 cabling recommendations. T568A and T568B offer two compatible options; modern networks frequently rely on auto-MDI/MDIX, reducing the need for dedicated crossover cables.