T568A and T568B are the wiring standards that define the pinout (connection order) for terminating twisted-pair network cable in eight-pin modular connector plugs and jacks. These wiring standards are one part of the TIA/EIA-568 telecommunications cabling standards. The American National Standards Institute (ANSI), Telecommunications Industry Association (TIA), and Electronics Industries Alliance (EIA) are in agreement on the use of T568A and B.

Both standards specify the wiring schemes for the connection of twisted-pair copper cable into eight-position RJ45 connectors and jacks for data transmission. The twisted-pair cable is comprised of four wire pairs that provide eight conductors. The pairs feature blue, orange, green and brown colours. Each pair has a solid colour wire and another wire that is the same colour, with white stripes. Once the pairs are untwisted, eight separate wires are available to match the eight pins on a jack or plug.


The T568B Wiring Standard

In commercial environments, the T568B wiring standard is more commonly used for telecommunication installations. However, the 568A assignments are frequently seen in residential applications. Cabling expansions are made according to a network’s current wiring scheme in order for wires to match up and data signals to transmit. Both T568A and T568B wiring standards are straight-through schemes.

The Difference in T568B and T568A Wiring Schemes

The pair-to-pin assignments are different in the T568B and T568A wiring schemes. This difference is easily seen with pin positioning. The green and orange pairs (2 and 3) are switched. Patch cords can be purchased that are pre-wired for T568B or 568A connectivity.

Comms Express can provide additional information on these factory wired patch cables.

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RJ45 Connectors & Adapters
Network Installation & Essentials