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RJ45 Termination
Last Updated: 01/31/2017
  • RJ45 Modular Plug

    RJ45 Modular Plug

  • Rear View of Patch Panel Labeled for T568B

    Rear View of Patch Panel Labeled for T568B

Description (Pinout):

Pin#: T568A: T568B:
Pin 1: White/Green -- White/Orange
Pin 2: Green
Pin 3: White/Orange -- White/Green
Pin 4: Blue Blue
Pin 5: White/Blue -- White/Blue
Pin 6: Orange Green
Pin 7: White/Brown -- White/Brown
Pin 8: Brown Brown


Required wiring configuration of 4 pair Ethernet cable for use in high speed data transmission; complies with requirements for Category 5e, Category 6, and Category 6a performance of structured cabling systems.

Installation Considerations:

Consistency should be maintained throughout the installation – all runs wired using either T568A or T568B, not a combination of the two.

The number of twists per inch in twisted pair cable varies, meaning that all pairs are not identical. This is one reason that an Ethernet installation should use either the T568A or T568B wiring configuration and not just an improvised configuration.

T568B is currently the most widely used termination in the United States.

Popular Manufacturers (RJ45 Plugs):

Related Industry Terms/Acronyms:

  • RJ45 – common name for the 8 position / 8 conductor registered jack and/or port typically used in Ethernet installations

  • Pinout (or pin to pair assignment) - refers to the wiring configuration between the conductors in a cable and the pins in the connector or between the connectors at each end of the cable

  • UTP - copper Ethernet cable consisting of Unshielded Twisted Pairs surrounded by an outer jacket

  • STP (ScTP) - Shielded Twisted Pair cable encases the conductors in a shield (usually foil) as a means of reducing the potential for electromagnetic interference (EMI). The shield may also be composed of a braided screen (ScTP)

  • CAT5e / CAT6 / CAT6A – copper Ethernet category cable delivering varying levels of performance and typically terminated using either the T568A or T568B wiring configuration

  • Straight through – refers to a pinout wherein pins 1-8 at one end of the cable are connected to corresponding pins 1-8 on the other end of the cable (as opposed to pin 1 at one end being connected to pin 4 at the other end for example)

  • TIA/EIA 568 – refers to structured cabling standards as defined by the Telecommunications Industry Association and the Electronic Industries Alliance

See Also:

Further References:

  • IEEE (Institute of Electrical and Electronics Engineers, Inc.)
  • ANSI (American National Standards Institute)
  • TIA (Telecommunications Industry Association)
  • EIA (Electronic Industries Alliance)


Which pin is pin #1 on an RJ45 plug?

Hold the plug with the rear opening facing you and the keystone tab facing down. Pin #1 is the far left pin. Pin #s continue in sequence from left to right.

How do I decide which configuration to use?

When working within an existing network you should match the configuration currently in use. There may be documentation indicating which is in use, but it may be easier to simply look at the RJ45 of an Ethernet cable already in place. When the network is new either configuration may be used; however, T568B is the mostly widely used configuration in the United States.

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