RJ45 and RJ11

In this video from ITFreeTraining, I will look at the connector types RJ45 and RJ11. These are fundamental connector types that are used in networking and, thus, very important for the IT technician to know about.

Registered Jack (RJ)
0:12 To start with, I will look at the Registered Jack otherwise known as RJ. RJ is a specification that defines the jack and the connector – this is essentially the plug and the socket that it goes into.

The original RJ standard defines the number, wire position and conductors in the connector. This is something you don’t really need to know. Why? Because in IT we only use RJ45 and RJ11 as the terminology to define the plug. In IT we don’t worry about how many conductors there are, or how many wires it supports or their position, as we just use the names to refer to the plug rather than the specification. Let’s have a look at a RJ45 plug attached to a cable, and this will start to make sense.

RJ45
1:00 Let’s consider a standard network cable, which we would in IT refer to as RJ45. This particular cable, therefore, meets the standard called RJ45. This is because, in order to meet the standard, it needs to have eight positions. A position simply means somewhere a connector can be mounted to. The next requirement it needs in order to meet the standard is that it needs to have eight wires or four pairs of wires. You can see that this connector has this and, thus, meets the standard for RJ45.

Now let’s consider this cable. This cable, like before, has eight positions. However, there are only four wires or two pairs of wires being used. This connector does not meet the RJ45 standard and, technically, it should not be called RJ45. This cable does meet another RJ standard which has a different number, not 45 after it; but you will never need to know that in IT. In IT we still call this an RJ45 connector, even though, technically, it meets a different RJ specification.

Essentially, in IT, we adopted the convention of calling the connector an RJ45 connector. If there are eight wires, technically this is correct, but any less than that it is not. Don’t worry about it, if you are talking to someone in IT they will all call it an RJ45 cable; someone in telecommunications may call it by its correct name, but not in IT. Let’s now have a look at the other connection you may come across.

RJ11
2:40 The next connection that I will look at is the RJ11 connection. To be technically correct, this connector has six positions and two wires or one pair. This connector is often use to connect telephones.

If, for example, you come across a cable like the following, it has six positions, six wires or three pairs, then technically it is not an RJ11 connector, but in IT we still call it an RJ11 connector.

Before I move on in the video, I will do a quick summary of the main points to make sure everything is clear.

RJ Summary
3:16 Shown here is what we refer to, in IT, as an RJ45 connector. These are used primarily in networking, so you will see a lot of them. They have eight connectors for wires which are called positions in telecommunication language. In telecommunications, the number of wires in the connector will determine what number follows RJ. In IT, however, regardless of how many wires are used we call it an RJ45 connector.

The next connector that you are likely to come across is the RJ11 connector. A little bit smaller than the RJ45 connector, the connector itself has six connectors for wires. As before, in IT regardless of how many of these connectors have wires attached, we still call it an RJ11 connector. Although, at times, it may not be technically correct, it is a convention that we have been using in IT for a long time. If you are working in IT, you won’t need to worry. If you decide to take up a career in telecommunications, you may need to know.

References
“The Official CompTIA A+ Core Study Guide (Exam 220-1001)” Chapter 3 Position 11380-11662
“CompTIA A+ Certification exam guide. Tenth edition” Pages 809 – 811

Credits

[Sneder]

The revelation as to why the pairs of wire are laid out how they are in RJ45 is exactly the kind of stuff why I like learning, thank you!

[FinFu]

I love how u emphasis there is no need to dig further into those protocols as IT

[oumsker]

Thank you for taking the time to share these informative videos. They are very helpful!

[sagarsuryawanshi.s]

Your Videos are very helpful for getting basic information if starting career in I.T

[mRahman]

It's actually called a 8P8C Connector and 6P4C Connectors.

But like you said, this is considered semantics.

[Kid]

That was super helpful, I thought I needed to buy an RJ11 to RJ45 adapter but it turns out an RJ11 will fit anyways!

[laughingbird]

Such a great video man.. You are who i call a teacher. well done!

[predicationstcp]

It's not IT but audio i'm looking for, how to connect a RJ11 to a audio mixer microphone and speaker?

[neildobier]

You mention that you have a video for making your own cables, where can i find this video? as I have searched and can not find it on your channel.

[RBASB]

Awesome video. Well explained and straight to the point.

[LIYNSKIN]

Thanks for the video
Can you please explain what is the color scheme for an rj45 to 1 pair rj11 cable?

[sharadikweli]

The expectation is that people in IT are dumbed down on true technical specifications. I have never heard such a 'don't worry about it' explanation!

[vinayakthote]

you are great man.
last question can we convet rj 11 to rj 45

[engineeringinsight]

Thank you for the free knowledge ! much appreciated

[AQUIBs]

Is it possible to convert RJ45 broadband cable to RJ11 for old router/adsl modem?
only for WIFI not for telephone connection.

please guide me and if there is a splitter or converter then please provide me a link.

Thanks in advance!

[richardpalmer]

When making up RJ11 for phone do you do the color code the same positions on both ends? Because I have bought ones that were reversed from one end to the other.

[IsllamalHashimi]

Can I plug rj11 on cat6 cable for landline phone???

[kafra]

Could we get another Video on the RJ45 considering the different ways to wire it considering the number of pairs? Would be really great =)

[gamebox]

can analog phone still works even if you patch it to a DATA port?

[technicalthug]

Plugging in an RJ11 into an RJ45 will usually damage the outer pins. Best to use an RJ45 plug int an RJ45 jack.