Know the Difference- RJ9, RJ11, RJ12, RJ45, RJ48 & Pinout

Last updated on March 21st, 2024 at 11:33 am

We have come across several variants of registered jacks. They are usually differentiated with specific numbers after ‘RJ’. This distinction is given corresponding to the number of positions and wires/connectors. They also differ in size. Let’s discuss some of the prominent registered jacks.


All these denote the same 4P4C connector. The change in number, in this case, does not indicate any change in the features. RJ9 is also called RJ10 and RJ22.

RJ9 Cable and Connector
RJ9 Cable and Connector

RJ9 is typically used to connect the telephone headset(sometimes called a handset) to its body. Thus RJ9 does not interface with the public network. For this reason, it is not considered an official registered jack.

It has the least number of positions(4 Positions). Hence, it is the smallest among the registered jacks.

RJ9 Pinout
RJ9 Pinout

The pinout and color code of RJ9/RJ10/RJ22 is given in the table below.

PositionPinDescriptionColour Code
Pin description of RJ9/TJ10/RJ22


RJ11 comes under the category of 6P4C modular connectors. It is slightly larger than RJ9/RJ10/RJ22. These connectors transmit audio and control signals. They connect the telephone to the Public Switched Telephone Network (PSTN) networks. They are also used in Asymmetric Digital Subscriber Line (ADSL) and modem connections.

RJ11 Pinout(Male Connector)
RJ11 Pinout(Male Connector)

The 4 wires are utilized as two pairs. Thus RJ11 can make two connections to connect with two telephone lines. Usually, one pair is used and the other is kept as extra. (Read more about RJ11 here.)


RJ12 is a 6P6C connector. It has 6 positions and 6 wires. Thus the only difference between RJ12 and RJ11 is that RJ12 has two more wires. Since the number of positions is the same, the size of RJ12 and RJ11 is also the same.

RJ12 can make 3 connections with the available 3 pairs of wires. RJ12 is mainly used for system phones. It can also be used in place of an RJ11 connector. But the reverse is not possible since RJ11 can only make two connections as opposed to the three connections of RJ12.

rj12 pinout
rj12 pinout

The pinout and color code of 6P6C connectors are given below.

PositionPinRJ11RJ12Colour Code
1Transmit+UnusedT3White or Orange
6Receive-UnusedR3Blue or Brown
Pin description of RJ12 Connector


RJ45 is a well-known connector and is widely used for Ethernet and data connections. Hence they are also known as Ethernet connectors. It is an 8P8C connector.

With the larger number of positions, RJ45 is slightly larger than RJ12. RJ45 terminates the coaxial cables of Cat6 and Cat5e standards. (Read more about RJ45 here.)

The pinout of RJ45 is given below.

Straight cable pinout
Straight cable pinout
Crossover cable pinout
Crossover cable pinout

For more differences between RJ11 and RJ45, read: 9 Key Differences Between RJ45 and RJ11


RJ48 is also an 8P8C connector that has a good similarity with RJ45. But both the connectors are not the same.

Although RJ48 is used in the networking sector, it is specifically used to terminate T1 and ISDN networks. Another advantage of RJ48 over RJ45 is that it can be used for longer-distance communications.

RJ48 is used to terminate Shielded-Twisted Pair (STP) cables. It is available in different variants such as RJ48C, RJ48X, and RJ48S.

RJ48 pin combination is 1,2,7,8 or 1,2,4,5. The pinout of RJ48 is given below:

RJ48 Pinout and Color Code Description
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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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