RJ11 vs. RJ45: What’s the difference?

There are many different types of jacks such as RJ11, RJ14, RJ21, RJ35, RJ45, RJ48, etc.. They are mainly used in North America, and some are used all around the world. The two most typical Registered Jacks are RJ11 and RJ45. Each of them is designed for their particular objectives. RJ11 and RJ45 are connectors which have gold pins that are used for networking, telecoms and low voltage lighting control software. RJ stands for Registered Jacks, which were designed by the Bell system and managed by the Federal Communication Commission for day to day interface issues. This post aims at helping you differentiating RJ11 from RJ45.

RJ11 Connector

RJ11 is the cable connector that is being used in telephone sets, modem cables, and ADSL. There are four wires inside it. It is a 6P4C standard which confirms that it has six positions and four connectors. Through these jacks, now it is viable to link telephone lines to this RJ11 port on the system for receiving calls. Mostly the Americans identify it as a necessary phone plug. It has a finishing of plastic along with a clip of spring at its top. The standard position for this port is on a fax machine or a telephone.


RJ45 Connector

RJ45 is the standard wired Ethernet over copper cable connector. RJ45 plugs are used in networking, where you connect computers or other network elements to each other. It is usually made of a plastic piece with eight pins on the port, four of the pins are used for sending and receiving data, while the other four are used for other technologies or power networking devices. It is 8P8C which denotes that it has eight positions and eight contacts. Ethernet cable terminated with RJ45 connector is also called RJ45 cable, like cat5 and ca6 cable.

RJ11 vs. RJ45

Application-The major difference between these two is about their utilization, that where they are needed. RJ45 plugs have the usage in networking to link up computers or other network components to each others. While RJ11 plugs have the usage for telephones, modem cables, and ADSL.

Design-If you look closely at both connectors, you would see that there are only four wires inside and RJ11 while there are eight wires inside an RJ45. As a consequence of having to accommodate more wires, RJ45 connectors are also a little bit bigger than RJ11s. Physically, they may look the same, but RJ45 contains an additional layer of plastic on one of its sides. This strip is known as keyed RJ45 plug. This layer restricts a plug wired for particular equipment that is put into unsuitable RJ45 socket. These are quite similar to RJ12 standards and look alike to each other.

Can I Plug a RJ11 Connector to a RJ45 Slot Or Vice Versa?

It is then quite easy to deduce that you can’t plug-in an RJ45 connector to a RJ11 slot but the opposite is possible. Because RJ45 is bigger than RJ11. But we should keep in mind that although you can plug an RJ11 connector into an RJ45 slot, you should avoid doing that because you might damage the device that has the RJ45 slot, whether it is a switch or a network adapter.


In a nutshell, RJ45 is used with Ethernet cables in computer networking while RJ11 is used in connecting telephone units. RJ45 contains more wires than RJ11. RJ45 is physically bigger than RJ11 to accommodate the extra wires. Understanding the differences of them can help you choose the right connector in applications. For choosing the right connector type, please visit www.fs.com for more information.


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.