March 09, 2024

If you work with network cables, you’ve likely encountered the terms T568A and T568B. These are two wiring standards used for eight-position RJ45 modular plugs. In this quick reference guide, we’ll delve into the details of T568A and T568B color coding, their differences, application scenarios, and how to choose between them.

T568A vs. T568B: What’s the Difference?

The primary distinction between T568A and T568B lies in the arrangement of the green and orange wire pairs. Let’s break it down:

T568A & T568B Color Coding with RJ45


·         Green wire connects to pin three.

·         Orange wire connects to pin six.

·         All other wires follow the same pin assignments as T568B.


·         Orange wire connects to pin three.

·         Green wire connects to pin six.

·         Again, all other wires align with T568A.


Why Do We Have Two Standards?

Both T568A and T568B are allowed under the ANSI/TIA-568.2-D wiring standards. Here’s why they exist:


  • T568A:
    • Recognized as the preferred wiring pattern.
    • Provides backward compatibility to both one-pair and two-pair USOC wiring schemes.
    • Required for wiring done under federal contracts in the U.S.
  • T568B:
    • Matches the older AT&T 258A color code.
    • More widely used in practice.
    • Permitted by the ANSI/TIA-568.2-D standard but offers only single-pair backward compatibility to the USOC scheme.



Technical Comparison

From a technical standpoint, there’s no difference between T568A and T568B. Both standards offer the same transmission performance and support Ethernet protocols, including Gigabit Ethernet. However, consistency is crucial when wiring your network. Mixing T568A and T568B can lead to confusion during troubleshooting.


Application Scenarios

  • Home Networks:
    • Either standard can be used, but T568B is more common. It aligns with the color code used by most network equipment manufacturers.
  • Commercial and Industrial Settings:
    • T568A is often preferred due to its backward compatibility with both one-pair and two-pair USOC wiring schemes.

Remember, whether you choose T568A or T568B, it won’t impact your network’s speed or reliability. Just ensure consistency throughout your installation. Happy wiring!