Differences Between RJ45 and RJ11 Connector

Like fiber patch cable terminated with different types of fiber connectors, such as LC, SC, or FC, Ethernet cable which is the most commonly used component in home network can be also terminated with various RJ-style connectors, like RJ45. The letters “RJ” stands for registered jack, which is a standardized telecommunication network interface, designed by the Bell system and managed by the Federal Communication Commission(FCC) for connecting voice and data equipment to a service provided by a local exchange carrier or long distance carrier. There are many different types of RJ-style connectors, such as RJ11, 14, 21, 35, 45, and so on, and the two most typical types are RJ11 and RJ45. Since these two connectors have similar appearance, many people often mix them together. This post will point out some differences between them to make you better understand.

What Is RJ45 Connector?

RJ45 connector as shown below or RJ45 plug is a type of twisted-pair connector used for Ethernet networking. 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, so this connector type is also called as 8P8C (8-position, 8-conductor) modular connector. This kind of connector is suitable for many applications, such as Ethernet networking, telecommunications, factory automation and so on. Ethernet cable terminated with RJ45 connector is also called RJ45 cable, like cat5 and ca6 cable.

RJ45 connector

What Is RJ11 Connector?

RJ11 as shown below is the most commonly applied connector for telephone lines. It has a total number of six connector positions, but it typically utilized 2 out of the 6 positions, so it can be wired with a 6P2C (6-position, 2-conductor). However, these types of jacks are very rare, most often, an RJ11 connector is 6P4C (6-position, 4-conductor) with two of the four wires running to the junction box unused. The RJ11 is the most common type of registered jack connector today and it is used for the purpose of terminating phone lines. You should keep in mind that when using an RJ11 conductor, make sure to follow all instructions, so that your connection with any device is done correctly.

RJ11 connector

Comparison Between RJ45 and RJ11

Although RJ45 and RJ11 has similar appearance, there still exist some differences between them.

  • Application: The biggest difference between these two is in where they are actually used. RJ45 connector is used in networking, where you connect computers or other network elements to each other, while RJ11 is the cable connector that is being used in telephone sets, ADSL, and modem cables, etc.
  • Structure: Aside from the application, there are also differences in the connector structure that an individual can easily see and identify. If you look closely at both connectors, you would see that there are only four wires inside RJ11, and there are eight wires inside an RJ45. As a consequence of having to accommodate more wires, RJ45 connector is also a little bit bigger than RJ11.
  • Wiring Scheme: Another difference between these two connector is their wiring scheme. The typical RJ11 connector has six terminals, and usually only the middle four pins are used as shown below. The POTS (plain old telephone lines) residential telephone wiring generally contains two pairs of wires, which are designed for two separate telephone lines. The center pins (red and green) contain the first telephone line. (Note: business (digital) phone systems may be wired differently). As for RJ45 connector, it has two different wiring scheme—T-568A and T-568B. These wiring standards are listed below. These two wiring scheme can be used to create a cross-over cable or straight-through cable. Cross-over cable has a T-568A connector on one end and a T-568B connector on the other end, which is typically used for direct computer-to-computer connections when there is no router, hub, or switch available. Straight-through cable has either T-568A or T-568B at both ends, which is designed to connect different types of devices.

wiring scheme for rj11

wiring scheme for rj45

Can We Plug an RJ11 connector into an RJ45 Slot?

As we have mentioned above, RJ45 connector is bigger than RJ11, so it is possible to plug-in an RJ11 connector into an RJ45 slot, but 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. This is true when you use an RJ11 connector that is connected to your phone line. The reason behind this is the power that is being delivered by the telephone company into your handset that allows it to function even during a power outage.


If you observe carefully, you can find many differences between these two connector types by sight, like size, construction and wiring standard that we have mentioned above. And according to different application, RJ11 and RJ45 connectors are different, the former one is used for networking, while the latter one is used for telephone lines. For choosing the right connector type, you should take these factors into consideration.

Author: tiffany09

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