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RJ45 Wiring Schemes

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One of the questions in the CORE-IT PROS first Packet Pub Quiz asked which ANSI/TIA wiring standard was used in the plug shown in the picture. Since this was one that many people got wrong, I thought I would take a moment and provide the answer and some background.

The answer, this is wired using the ANSI/TIA T568B wiring standard. When using the T568B standard the orange pair is on 1,2, the green pair is on 3,6, the blue pair is on 4,5 and the brown pair is on 7,8.

There are two popular wiring standards when connecting RJ45 plugs and jacks to network cabling, these are T568A and T568B. The performance between these two standards is the same and in most cases it comes down to which standard your organization is following.

What is the difference between T568A and T568B? The difference between these two is where the orange and green pairs are connected. T568A is very popular in US Government installations and in residential installations. It works when where the cabling may be used for network connections or voice connections. T568B is the popular standard for installations where the cabling will only be used for networking.

What happens if I mix and match T568A and T568B? Well, if you do that in the same cable, you will end up with a crossover cable. While some systems will automatically correct for this, it is a really bad idea. What about connecting a T568A patch cord to a T568B wall connection? In that case everything will work just fine.

For more information on these wiring standards, check out:

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