RJ45 vs RJ11: How to Distinguish?

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More and more people choose to install their home or office network themselves. RJ45 connectors play an important role in network data transmission. Even if you don’t DIY your own home network, you still need to insert the RJ45 connectors into the router for the network.

Some novices may confuse RJ45 with RJ11, so we’ll dig out these two things in this article. Hope this article can help you better understand the difference between RJ45 and RJ11 and give a guide to distinguish them.

History of Modular Connector

RJ45 and RJ11 are both modular connectors, the history of which can date back to the 1960s. The first type of modular connector was invented by AT&T to be used for telephones and then in the 1980s, they have been commonly used in the telephone system. Modular connectors have been so useful that they were not only used in the telephone system but also in data and telecommunication applications.

What is RJ45 and RJ11?

As is known to all, “RJ” means registered jack and the number behind “RJ” means the listing number. So, do you know what is “RJ45” and “RJ11”?


RJ11 (Registered Jack 11) usually has a size of 6mm*9.5mm. It features 6 positions and 2 or 4 pins, which is widely used in the telephone system and ADSL/VDSL modem. A 6P4C RJ11 connectors are compatible to make 2 connections with 2 pairs.


RJ45 (Registered Jack 45) is the most commonly used connector in network and telecommunication applications. RJ45 belongs to the category of 8P8C connector standard, which means that it has 8 positions and 8 pins/conductors. RJ45 connectors are compatible with many categories of Ethernet cables including Cat5, Cat5e, Cat6, Cat6a, and Cat8.

rj45 vs rj11

RJ45 vs RJ11: What’s the Difference?

RJ45 connectors are very similar to RJ11 in their appearance, and you may confuse them. But in fact, they have different designs and functions.


RJ11 connectors are small, compact, and square-shaped, while RJ45 connectors are rectangular, bigger, and longer. RJ11 is usually a 6P2C or 6P4C standard, which is regarded by Americans to be a useful telephone plug. RJ45 uses an 8P8C standard, which means that it has 8 positions and 8 contacts. Among these eight pins, four pins are used to send and receive data.


RJ11 connectors can support the speed of about 24Mbps, while RJ45 connectors are designed to achieve the maximum speed of 40Gbps for CAT8.

Wiring Standard

RJ11 connectors have 4 wires and they use a regular wiring standard. RJ45 connectors have 8 wires and they can be arranged to two wiring standards including T568A vs. T568B. In general, T568B is more common than T568A in daily use.

There are also two connectivity types for RJ45 connectors: straight-through and crossover connections. If both ends of Ethernet cables use the same wiring standard, it is called straight-through; but if not, it is a crossover connection. A crossover cable is generally used to connect a computer to a computer, a router to a router, and a switch to a switch.

wiring standard


It is known that RJ45 and RJ11 are used in different applications. RJ45 connectors are often seen in the network system, linking the modems to other network components. And they are paired with Ethernet cables for stable and high speed. RJ11 connectors have usage for fax machines, telephones, ADSL, VDSL, and other voice systems.

rj45 vs rj11 chart

What About Other RJ Connectors?

Besides RJ11 and RJ45, there are various other RJ connectors such as RJ12, RJ14, RJ25, RJ48, and so on. These types of RJ connectors are widely used in North America. Like RJ11, RJ12, RJ14, and RJ25 are modular connectors that feature 6 positions, and all of them are used for wiring a phone line. RJ12 uses a 6P6C standard, which is designed to build a connection for one telephone line with the key telephone system. RJ11 connectors can be replaced by RJ12 connectors as RJ12 also has the function of RJ11. Generally, RJ11 connectors are used for modems and wired telephones at home, while RJ12 connectors are more suitable for centralized telephone systems in offices.

rj45 connector


The biggest difference between RJ11 and RJ45 is their applications. The former is paired with telephone wires and the latter is used with Ethernet cables. Compared to RJ11, RJ45 connectors can be more popular nowadays in the scenarios of transmitting voice and data. An RJ45 connector is a small yet indispensable part in network systems and they are frequently used for networking devices such as modems, computers, laptops, switches, printers, and so on.


Is RJ11 still being used?

RJ11 connectors are mostly used for voice applications. And they continue to be used for wireline phones.

Are RJ11 and RJ45 connectors interchangeable?

Please note that an RJ45 Connector cannot be plugged into the RJ11 port, but an RJ11 connector can be easily inserted into the RJ45 port. However, we don’t recommend you do so as it may damage your devices.

Can I plug an RJ11 into an RJ45 port for Ethernet?

RJ11 connectors can be used for Ethernet. But it can affect the performance as you know that the maximum speed of RJ11 is 24Mbps. RJ45 connectors are the best choice for Ethernet.

For more information on this topic, you can keep up on our blogs. While VCELINK offers general and basic information for our customers and other visitors to the website, it’s not professional advice.


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