RJ45 pinout. Does it matter?

RJ45 pinout. Does it matter?

The RJ45 pinout standards specify two wiring schemes on how to configure RJ45 ethernet cable. While the T568A and T568B wiring standards are very similar, most often than not, the T568B scheme is used for many data cable applications. This is despite the fact that the standard shows preference to the T568A and its schematic has been show to improve issues regarding delay skew and signal-to-noise ratio.

Why Make Your Own Cables?

Many installers prefer to make their own Ethernet cables instead of purchasing pre-made CAT-5e or CAT-6 cables. Purchasing pre-made cables can become expensive, especially when you need to run many lines. The other issue is that pre-made cables only come in common lengths. Having to deal with extra lengths of cable can make your installation look unkempt and unprofessional.

To reduce costs and be able to have just the right length of cable for each one of your connections, all you need is:

  • Bulk CAT-5e or CAT-6 Ethernet cable
  • RJ45 connectors for the appropriate cable (CAT-5e or CAT-6)
  • RJ-45 crimping tool
  • Ethernet cable tester

How to Configure RJ45 Ethernet Cable for T568A or T568B

Whether you choose one standard over the other really depends upon the configuration of the existing network you are working on or if you are building a network from the ground up. The benefit to using the more popular T568B wiring scheme is that it is backward compatible to USOC wiring schemes, but it also accommodates current and future demands on the network.

If you are working on an existing network, it is important to continue with the existing wiring scheme for straight through cables. If this is unknown, this can be determined by testing the cables for continuity. Mixing the two schemes will prevent data signals from transferring simply because the individual colored and striped wires will not be matching up when you connect the plugs and jacks.

When visually comparing the T568A and T568B wiring configurations side-by-side, you will see that that the pin positions for the green and orange pairs are swapped. For T568A, the striped green and solid green untwisted pair is positioned in pin 1 and 2, while the striped orange and solid orange untwisted pair is placed in pins 3 and 6. The T568B wiring scheme places striped orange and solid orange in pins 1 and 2, while striped green and solid green are placed in pins 3 and 6. Otherwise, the remaining wires are configured the same with solid blue, striped blue, striped brown, and solid brown placed in pins 4, 5, 7, and 8 for both configurations.

For some instances, it may be necessary to mix the two configurations when previously T568A-wired components will be connected to T568B components. In this case, you would want to create a crossover cable by terminating one end with a T568A terminated plug and the other with a T568B plug to prevent data loss.