A Guide to RJ45 Connectors

RJ45 network connectors are most commonly found at either end of an Ethernet (wired internet) connection. At first glance, they appear similar to the familiar telephone plugs and jacks which connect landlines to walls or switchboards. However, RJ45 connectors are typically slightly larger.

The term RJ45 connector is widely used today to describe both male RJ45 plugs and female RJ45 sockets. The plugs, sometimes called modular connectors, are usually found on the end of Ethernet cables. The sockets or jacks are generally embedded in the device that is being hooked up or mounted to a fixed wall panel.

Definition of an RJ45 Connector

Registered jacks are for telecoms network interfaces. Their job is to link various types of voice and data equipment either to a central hub or directly to each other.

In modern domestic and commercial environments, RJ45 connectors are primarily used for plugging an internet-enabled device directly into hardware such as a modem, router, or server. The connectors themselves are the modular sets of fittings at either end of the physical data connection (Ethernet cable) joining one networked device to another.

As previously mentioned, the term ‘RJ45 connector’ can broadly refer to both male and female versions of these jacks and plugs. In the case of Ethernet networking, the plug fixtures on cable ends are the RJ45 male parts, while the sockets found on the devices themselves are RJ45 female parts.

Technical RJ45 Definitions

Most standard Ethernet data cables have a core consisting of four twisted-pair wire strands, making eight individual wires in total. Male RJ45 plugs separate and correctly terminate these eight individual wires. In other words, RJ45 wiring is based on an 8P8C (8 position, 8 contact) configuration.

Standard RJ45 is defined as a mechanically-keyed variant on a generic 8P8C body. Mechanically keyed essentially means that RJ45 connectors also include an additional tab. This extra tab is designed to prevent them from being mated with any other socket standards which are visually similar, but electrically incompatible. It also prevents accidental disconnection.

For an RJ45 network connector to function properly, the eight Ethernet cabling wires must be inserted into the correct pinout locations on the male connector. With RJ45, this is done following either a T568A or T568B wiring standard. Each of these standards has its own colour-coded wiring convention, achieving two different forms of connectivity.

Wired Ethernet connections between devices are often preferred as a physical alternative to wireless or Wi-Fi networks. This is because wired Ethernet tends to provide a more reliable, stable, and interference-free connection. It also offers the potential for faster data transfer speeds than wireless in most cases and prevents interception of sensitive data by hackers.

Today, Ethernet networks are commonplace in both domestic and professional environments. A network is simply several interconnected devices that are capable of sharing data between one another. Home networks, for example, are usually based around a router or modem, connected to various other devices and sharing out data. This might include PCs and laptops, smart TVs, mobile phones, games consoles, media servers, printers, and so on. A domestic setup of this kind is an example of a LAN (Local Area Network). The name comes from the fact that all devices linked to it are close to the others, typically within the same building.

If all the devices on a given network can interconnect wirelessly, then there may not necessarily be any Ethernet or RJ45 cabling involved at all. However, when they are linked by a physical, wired connection for better speed and stability of data transfer, it is invariably some category of Ethernet cable that connects them. It will have a small plastic or metal plug fitting at both ends. Corresponding sockets on the respective devices will allow the plug to slot in easily, making a secure connection. These modular plug and socket fittings are commonly known as RJ45 connectors.

There are various RJ45 connector types available to buy, with the most important distinction being between the modular male and female versions. So, what are the different types of RJ45 connector, and how do you differentiate between them?

In short, plugs are male whereas jacks or sockets are female. The key role of plugs is to properly terminate the wires in an Ethernet cable. Conversely, the role of sockets is to transfer the electrical data signal through to the device it is being shared with. The two are designed to fit together securely to provide a solid connection – both physical and electrical.

The pin assignment according to type T568B swaps pairs two and three. The correct pin assignment is as follows:

The correct standard will depend on whether you are using a straight-through cable (often called a patch cable) or a crossover cable. In most cases, you will be using patch cable, which has the same type of wiring standard at each end. Crossover cable is far less widely used and has a T568A connection at one end and a T568B connection at the other end.

Wiring your own male RJ45 plugs to the end of a suitable network communication cable requires just a few simple tools. Fixing a new connector is usually cheaper than replacing an entire Ethernet cable. Other reasons you may want to wire them yourself include:

• Knowing how to wire an RJ45 connector plug means that you can cut your Ethernet cable to custom lengths. This is handy for neatly managing cables or creating very long runs
• RJ45 plugs and sockets can be damaged by stress forces at connection points. This sometimes happens if a cable is too short or gets pulled or snagged. As a general rule, pressure on RJ45 connections should not exceed around 20lbs.
• Although the polycarbonate plastic on most RJ45 connectors is fairly robust, it can eventually wear out or break. Inserting and removing connectors incorrectly can damage plugs or sockets. Frequent swapping between sockets can cause plugs to loosen over time. Impact can also cause an RJ45 connector to fail, crack, or detach
• If you intend to make lots of cables, wiring them yourself can also be a considerable cost-saving measure

Ethernet Cable RJ45 Wiring Step-by-Step Guide

The tools and components you will need include:

• An Ethernet network communication cable
• RJ45 crimpable connectors for the category of cable you are using
• An RJ45 crimping tool

Once you have established which wiring convention you need to use, complete your RJ45 wiring by following these basic steps:

• If necessary, cut your cable to the required length with a cable cutter
• Use your crimping tool to trim and tidy the cut ends of the cable you will be working on
• Take a pair of wire strippers and remove about an inch of the cable jacket from the end. Make sure that you do not damage any of the internal wiring in the process
• Untwist and separate the eight individual wire strands that make up the cable core. Flatten and straighten them out as much as possible
• Arrange them side-by-side in a line. It is important to arrange them in the correct order by colour. For standard patch cabling, this is (L-R): white/orange, solid orange, white/green, solid blue, white/blue, solid green, white/brown, solid brown
• Cut the wires straight across at the ends, around half an inch from the cable sleeve
• Hold your male RJ45 connector plug with its contact pins pointing away from you and away from the cable wires, and its keyed tab (plug clip) facing downwards
• Gently push the arranged wires through the body of the RJ45 plug, until they reach and touch the end of the connector where the pins are. Feed-in a half centimetre or so of the cable jacket too; this will provide a stronger and better-insulated connection. If the length of the wires prevents this, you will need to trim them a bit shorter
• Once you have attached the connector according to the above steps, take your RJ45 crimping tool and use it to press down tightly on the connector around the cable. Tabs inside the connector will pierce and flatten the individual wires, forcing them into proper contact. Once you have crimped the wire around the connector in this way, that end of the cable is ready to be tested for use