9 Key Differences Between RJ45 and RJ11

Last updated on March 21st, 2024 at 11:39 am

RJ11 and RJ45 are popular connectors used in voice and data telecommunications equipment. RJ45 is mostly used for data communication purposes in ethernet cable whereas RJ11 is mainly used in conventional telephonic applications.

Although this is the most highlighted difference, there are several other important differences between RJ45 and RJ11. Some of them are listed below:

RJ45 VS RJ11 - Differences
RJ45 VS RJ11 – Differences
SizeBroader (larger)Smaller
Number of wires8 (4 pairs)4 (2 pair)
ApplicationTo connect data linesTo connect telephone lines
Supported Bandwidth10 Gbps24 Mbps
Compatible cablesCat5 and Cat6Telephone cables
Fiber compatibilityCompatibleNot compatible
Interchangeable connector plug-inCannot plug RJ45 into RJ11Can plug RJ11 into RJ45
Difference between RJ45 and RJ11
Note: The IT and communication aspects of RJ standardization have a slight difference. In IT, the standardization is addressed only with respect to the number of positions(slot for wire). They do not take care of the number of wires. But in communication, both the number of positions and the number of wires have to be satisfied as per the standard.
For example, any connector with 8 positions is called RJ45 in IT. Whereas in communication, only the connector with 8 positions as well as 8 wires is considered an RJ45 connector.

Here, we are discussing the connectors based on communication only.

What is RJ45?

Since RJ45 was introduced after RJ11, it has lots of enhanced features than RJ11.

RJ45 falls under the category of 8P8C connector standard. This implies that RJ45 has 8 positions for connections that can accommodate 8 wires. The 8 wires are used as 4 pairs.

RJ45 Connector
RJ45 Connector

The key application of RJ45 comes in Ethernet and Data communications. The RJ45 is thus used to terminate Ethernet cables, mostly of Cat5 and Cat6 standards. Hence, the network switches and hubs are the most connected devices with RJ45 terminations.

These connectors are now improvised to connect with fiber cables too.

Where is RJ45 used?

The RJ45 is used for Ethernet applications. Data transfer is the major purpose in this scenario. Thus, it supports 10Gbps bandwidth.

RJ45 interfaces are seen in the data distribution and collection points like a hub. Nowadays, they are also used in telephone lines.

Looking for USB-C to Ethernet connectors? 7 Best USB to Ethernet Adapters in 2023 (USB-C, 3.0, 2.0)

What is RJ11?

RJ11 is the predecessor of RJ45. It is a 6P4C connector. The RJ11 connector has 6 positions and at least 4 wires. Thus it is capable of making 2 connections at a time with the two available pairs. And at least one pair of wires will be connected to the communication line.

RJ11 Connector
RJ11 Connector

As it has less number of positions, it is smaller than RJ45 and easily insertable in the RJ45 jack.

Where is RJ11 used?

RJ11 is used for the connections in telephone lines, specifically for PSTN networks. So these are commonly used for voice applications. But recently, RJ11 has been used for connecting modems also.

Read in detail: Know the Difference- RJ9, RJ11, RJ12, RJ45, RJ48 & Pinout

Conclusion: RJ11 VS RJ45

RJ45 and RJ11 are the most widely used registered jacks. An RJ45 is used for Ethernet applications whereas RJ11 is specifically used in telephonic networks. The RJ11 connector can easily plug into the RJ45 jack. But it is not widely practiced due to power delivery issues.


Are RJ11 and RJ45 interchangeable?

We can easily insert RJ11 in the RJ45 jack or the ethernet port. The reverse is not possible since the RJ45 jack is bigger. However it is not advised to insert RJ11 in the RJ45 jack due to the power delivery issues.
The RJ45 jack receives more power compared to that of the RJ11. This may cause damage to the RJ11 connector.

Are RJ11 and RJ45 interchangeable?

Yes. RJ11 is compatible with the RJ45 jack. So it can be used for Ethernet.
But this can reduce the performance. RJ11 is designed to receive 24Mbps only since they are intended for telephonic applications.
Since Ethernet deals with data transfer, the Ethernet channels support up to 10Gbps speed. This cannot be utilized with RJ11.

What is the difference between RJ11 and RJ45 cables?

RJ11 is used with copper wires and twisted pair cables. RJ45 supports copper wires, twisted pair cables, and even fiber cables. Cat5 and Cat6 are the most used cables with RJ45 connectors.

Is RJ45 the same as a phone jack?

No. The phone jack has an RJ11 connector standard. It is slightly different from that of RJ45. Although RJ11 can be inserted in an RJ45 jack, the reverse is not supported. But the connections with modems are usually performed with RJ45.

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Ankit Negi

I am an electrical engineer by profession who loves to tinker with electronic devices and gadgets and have been doing so for over six years now. During this period, I have made many projects and helped thousands of students through my blog and YouTube videos. I am active on Linkedin.

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