568A and 568B Wiring Standards

What is 568A and 568B?

568A and 568B are wiring standards used to arrange the array of pins in 8P8C (sometimes erroneously referred to as RJ-45) connectors. These connectors in turn switched to the UTP or Unshielded Twisted Pair wire scheme. The number 568 indicates the arrangement of individual wires inside a CAT 5 cable. The Telecommunications Industry Association (TIA) and the Electronics Industry Association (EIA) developed these 568 standards. The American National Standard Institutes (ANSI) then approved it. Most of the organizations in the world adopted these standards.

Difference between 568A and 568B

Cables used for eight-position 8P8C modular plugs generally consist of 8 wires twisted together in four pairs, wherein the pairs are identified by a primary color. These pairs of wires carry a signal to a destination and back.

The 568A wiring standard is the ideal wiring prototype for standard use because it allows reverse compatibility to both one and two pairs Universal Service Order Codes (USOC) wiring. Regulations in the United States require the use of the 568A standard for wiring installations under federal contracts.

However, the 568B is the most commonly used wiring system in the industry today as it goes with the AT&T 258A color scheme. This allows one pair for backward compatibility with the USOC wiring method.

One way to physically identify the difference between the two wiring standards is through their green and orange wires, as these are interchanged.

568A Wiring Color Codes

The table below illustrates the pairing of the wires to an 8P8C jack:

Color Pair Jack Pin Plug Pin
white-green 3 – TIP 1 8
green 3 – Ring 2 7
white-orange 2 – TIP 3 6
blue 1 – Ring 4 5
white-blue 1 – TIP 5 4
orange 2 – Ring 6 3
white-brown 4 – TIP 7 2
brown 4 – Ring 8 1

568B Wiring Color Codes

The table below illustrates the order in which wire pairs are connected to an RJ-45 jack:

Color Pair Jack Pin Plug Pin
white-orange 2 – TIP 1 8
orange 2 – Ring 2 7
white-green 3 – TIP 3 6
blue 1 – Ring 4 5
white-blue 1 – TIP 5 4
green 3 – Ring 6 3
white-brown 4 – TIP 7 2
brown 4 – Ring 8 1

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