Introduction of the RJ45 interface

Posted on by FS.COM

RJ45 might be a name you are not so familiar with, but actually you have seen it in your daily life for a thousand times. Whenever there is a Ethernet network connection, RJ45 is always the interface used for devices. “RJ” means registered jack, which is a standardized telecommunication network interface for connecting voice and data equipment to a service provided by a local exchange carrier or long distance carrier. RJ45 is a member of the RJ family. It is especially used for Ethernet networking. And “45” is the number of the interface standard. Ethernet cables with RJ45 connectors are also called RJ45 cables.

RJ45 Network Interface Cards

Network interface card, or the network controller, is used to provide an electrical interface for the computer to the network and completely complies with the Ethernet standards. A proper termination is needed for connecting the LAN (local area network) media and the proper motherboard. Typically, cat 6 cable is terminated with an RJ45 modular plug, so its network interface card must have an RJ45 modular jack that matches with the patch cable.


RJ45 Cable Plug

RJ45 cable plug, namely crystal head, is widely applied to LANs and ADSL (asymmetric digital subscriber line) connections. The translucent appearance is the reason why it is described as crystal head. RJ45 cable plug is usually made of a plastic piece with eight pins on the port. Four of the pins are used for sending and receiving data, and the other four are used for other technologies or power networking devices. The plug can be inserted along a fixed direction and automatically prevent shedding. Moreover, this kind of connector is suitable for many applications, such as Ethernet networking, telecommunications, factory automation and so on. Actually, RJ45 connector was first invented in the 1970s to replace the bulkier connector for connecting modems to telephones in the telecommunication industry. Nowadays, it is frequently used for networking devices including Ethernet cables, modems, computers, laptops, printers, etc.


Difference Between RJ45 and RJ11

RJ45 and RJ11 are two commonly used jacks, but people often mixed them together because of their similar appearances. The biggest difference between them is that they are used for different applications. RJ45 is applied to networking while RJ11 is applied to telephone sets. Another difference is the number of wires in their connectors. From the previous introduction, we know that RJ45 connector has eight wires. But unlike RJ45, RJ11 has only four wires so that its size is also smaller than RJ45 connector. Although the smaller size of RJ11 makes it easier to be plugged into the RJ45 slot, it is not recommended to do so since this may damage the device that adopts the RJ45 slot. At present, instead of RJ11 jacks, RJ45 jacks are usually placed on the wall outlets inside people’s houses to reduce the number of visible wiring when using VoIP (voice over Internet protocol) handsets that are rapidly gaining popularity.



Generally speaking, RJ45 is one of the most popular connector types right now. People can use it to realize the Ethernet networking connections. The easy plug-n-play style reduces the difficulty of installation. In addition, RJ45 network interface cards and RJ45 plug cables are the extensively used products that come from the RJ45 family.

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