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What Is a RJ45 Socket?

Helen Akers
Helen Akers

An RJ45 socket is a type of connector that is used to facilitate communication between two or more devices in a network. It resembles a telephone jack and is primarily used in Ethernet and computer networks. While an RJ45 socket resembles jacks used for telephone networks and wiring, it is characterized by a wider design.

The purpose of an RJ45 socket is to provide enough bandwidth and capacity for computer networks. Since data needs to be transferred over some form of cabling or wiring, a computer's hard drive will usually have Ethernet ports which RJ45 cables can plug into. The wiring may extend to a modem or Ethernet device which connects to a wall socket. An RJ45 socket serves as a gateway to a telecommunications network that transmits data signals from one location to another.

Woman holding a book
Woman holding a book

RJ45 sockets were once used to provide traditional telephone service. Most customers, however, did not require the increased capacity that an RJ45 jack can provide. Since the idea of using these sockets for traditional phone service never gained much popularity, they became a viable option for computer networking, high-speed Internet and Ethernet service.

The eight pin design gives the RJ45 socket its wider appearance. It also increases the capacity for data transmissions. This is why this type of wall socket is used primarily for Ethernet and high speed Internet connections. When a telecommunications company receives an order for data lines, it will almost always install some type of RJ45 jack or socket.

Telephone service works in a similar fashion, but is typically handled through RJ11 sockets. In comparison, RJ11 sockets do not contain as many connectors. An RJ45 socket contains eight connectors and is a registered jack with the local telephone company.

Jacks connect a building's inside wiring to a demarc, which is a point of separation between the telephone company's outside wiring and the customer's wiring. Outside wiring runs from the telephone company's utility poles or connection box into individual buildings in order to provide service. The RJ45 socket serves as an interface where devices can connect or tap into network wiring.

Each RJ45 connector has both male and female connections that correspond to a jack or wall socket. Various telephone wiring is usually assigned to one of the eight pin connectors that make up the lower portion of an RJ45 connector. Some of the pins carry out special functions, such as programming resistors.

Discussion Comments


@Charred - That’s one way to do it. One thing you can do, if you’re into doing some electrical stuff in your house, is to just install an RJ45 wall socket into the room where you’ll need the Internet connection.

You’ll need to refer to an RJ45 socket wiring diagram to make sure that you’ve hooked up everything correctly; otherwise you may wind up with no signal coming from the line.

I have a friend who tried that without reading the diagram and that’s what happened to him. He finally had to pay an installer to come and set it up. It’s easy to do yourself, actually, but you do need to follow the diagrams.


@NathanG - If you’re using these kinds of cables with Internet devices like modems and wireless devices be sure to check what kind of jack you have to ensure that they will work together.

For example I’ve heard that some routers have RJ11 jacks. You may not be able to use the RJ45 socket with these connections, in which case you will need an RJ45 to RJ11 adapter.

Another scenario is if you have DSL and you want to connect the Ethernet cable to your phone line. The phone line doesn’t use RJ45 anymore so you will probably need to get an RJ45 to RJ11 splitter.

That’s what I did when I switched to DSL. One advantage is that the splitter came with four plugs, so I effectively converted one line into four, and could string Ethernet cables to different devices. That’s useful if you want to build a home network for example and you need more than one line.


I use a CAT5E cable for my Ethernet connection. I actually have a wireless router so I hook it up between the router and the modem and then hook up another cable to the back of my computer, which has the RJ45 socket.

Some people have told me that I should use the Cat6 cables instead but I really see no difference in speed. Some of the extreme gamers swear by the more updated version of the cable but I’m not an extreme gamer myself. I just have high-speed Internet, the basic version at around 3 Megabits per second.

I love the flexibility of the Ethernet cabling – I can buy it in really long spools – and the wideness of the RJ45 socket makes it easy to hook up to the computer.

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