Choosing the right wiring standard

For all the young technical people who come across data outlet modules with two different wiring standard options, this is a quick guide to keep your data cables correctly wired.

Bulk data cables have 4 twisted pairs and these have to be terminated on a module [usually at a wall or desk outlet], or on a panel [usually in an equipment rack]. The colours are described as White/Orange and Orange, White/Green and Green, White/Blue and Blue, White/Brown and Brown [see above].

Each module has a colour coded label, to show you where to land these pairs. As you can see below the module is a little confusing with two sets of green and orange pairs, and single blue and brown pairs. Basically there are two standards used around the world namely T568A & T568B. Here you can see these standards represented as a small A & B on the left hand side of the module.

T568A is the preferred wiring standard in European and Pacific countries, as well as in all United States government installations.

T568B is more commonly used in commercial installations and data networks in the U.S. and the UK

The main difference between the standards is that the orange and green pairs are swapped, White/Orange becomes White/Green etc.

If you now look at the above module you can see that the pins 1,2,3,6 are either green or orange, and the other pins 4,5,7,8 are always the same for both standards.

I you don’t know what standard to use in a new installation, so long as you chose a single standard throughout the job, it won't matter at all.

There are some manufacturers who only have the regional colour coding, which is very helpful, but it is important to appreciate the difference, as other manufacturers have both wiring systems to accommodate a global supply.

As the vast majority of our jobs are within the UK, we simply use the phrase “B for British“, and thats how we remember our standard. If you know the standard for your country, make a simple phase to remember yours too.

Lastly, what happens if you wire both ends of a cable differently, so A one end and B the other. Well you have created a crossover cable It is most often used to connect two devices of the same type, e.g. two computers. So this lead is quite useful, but should be labelled accordingly as it can't be used to patch a computer to a network switch.

When it comes to wiring RJ45 plugs you will need to ensure the sequence is the same both ends. It won't matter if you choose A or B they will always work if they are the same both ends.