How To Fit An RJ45 Connector To UTP Twisted Pair Cable
More and more of us are realising the benefit of using Cat5e or Cat6 cable in our home installations. Whether it be for internet, telephone, data or even the new HDMI over Cat5e/Cat6 standard HDBaseT, Cat5e / Cat6 cable is the most cost and effort effective cable solution around. All you need is some Cat5e, Cat6 cable and some RJ45 connectors
The cost and quality of Cat5e and Cat6 has gone down (cost) and gone up (quality) respectively over the past few years as more and more homes and installers are using it. Not only is the cable very cheap, its also versatile, easy to manage and very easy to install. Simply cut to length and fix the connectors on the end!
Cat5e and Cat6 cables are made up of 4 pairs of copper cables twisted together. Each pair is colour coded with a plastic jacket. Each pair is made up of a solid colour and a white cable with the relevant colour striped across it. e.g. brown and white/brown, blue and white/blue, green and white/green plus orange and white/orange. Each pair of cables is tightly twisted around each other, with each colour of pairs having a different twist rate. in 100BaseT one pair of cables is used to send data and one pair of cables is used to receive data.
Twisted pair cabling is very good at sending signals long distances with a good degree of interference avoidance. The way twisted pair cables avoid interference is all to do with the twists! The basic theory is that if the cables comes into contact with any interference, because of the twists, only one of the pairs will be subject to the interference at any one time. Therefore at the end of the cable run, the two pairs can be compared and any interference can be cancelled out, this is a very simplified explanation! This is one of the many reasons why the RJ45 connectors must be cabled up in the correct wiring diagram!
However many people dont realise that the connectors can not only be a little tricky to install, but also the cable MUST be wired in a very specific way! Most people who I talk to this about say, Well as long as they are the same at both ends, what does it matter? Well it really does matter
A LOT! Yeah you may be very very lucky and get yours to work this way, but for 99.9% of people you will have problems with the signal if the cables are not wired up correctly inside the RJ45 connector.
There are currently two standards to wire up a RJ45 plug with Cat5e/Cat6. These standards are known as TIA/EIA-568-A (T568A) and TIA/EIA-568-B (T568B). The traditional separation of the two standards was that T568A should be used for horizontal cable runs, T568B should be used for vertical cable runs. The only actual difference between the two types of RJ45 terminations is that the transmit and the receive pairs are crossed over. This means that as long as both ends of the same cable are wired with the same standard it wont make a difference if you use T568A or T568B.
The only exception to this rule is for the use of crossover cables. Crossover cables have one end wired up as T568A and one end wired up as T568B. These types of cable are used when you are connecting two like devices. For example when connecting your home computer to your router, you will use a straight through cable. The router knows that it is going to be connected to other PC type devices, it comes preconfigured so that the computers send and receive pairs are matched to the opposite send and receive pairs of the router. There is no point both NICs (Network Interface Cards) sending data to each other on the same pair of wires as neither one of them will be listening, just sending.
With a crossover cable this switching of the send and receive pairs is done in the cable and RJ45 plugs. With this crossover cable you are able to connect two computers together, or even two hubs etc. Most modern professional networking equipment such as Cisco routers and switches come with Automatic MDI/MDI-X. Automatic MDI/MDI-X is where the switch can automatically tell what type of device is connected to it and what type of cable has been used. If the incorrect cable has been used (eg. A crossover instead of a straight through) the switch will automatically cross its own connections to make up for this. As a general rule it is always best to use the correct wiring type for the situation you are in.
When it comes to using Cat5e, Cat6 and RJ45 plugs for HDMI and simple data transfers you should always use just the one standard on both ends. There are many competing arguments for T568A over T568B or vice versa, we at Tradeworks recommend you use one standard and stick with it! Below is the information you will need to correctly wire up your RJ45 connectors.
The RJ45 connector has 8 positions for 8 cables (also known as 8P8C). For 100Mbit (100BaseT) installations, only 2 pairs of cables are used, one pair to transmit and one pair to receive. For installations of higher speeds and with HDMI extenders or HDBaseT extenders all four pairs are used. We recommend always connecting all of the cables to future proof your installations.