Electro Wiring Circuit: Rj45 Color Code

Look for RJ45 color code a , b and standard make a ethernet crossover cable or a straight throught cable , RJ45 or Registered Jack 45 , is the one of the most popular component in computer and communication network. Anyone working in networking field came across this connector every now and then. Because of this connector different devices talk with each other.

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RJ45 connector has a plastic body and inside it there are 8 conductor wires. This connector is used on both the ends of UTP cables. UTP cables having RJ45 at both end, is either a cross cable or straight through cable. There are 8 wires in every UTP cables, there is a pattern on how to place them in correct position in RJ45 connector to get desired functionality. This is achieved by following RJ45 color code scheme.

Color coding is a pattern that tells you how to place 8 UTP wires in RJ45 connector to get a working cable. There are two popular color coding standards TIA/EIA 568A and 568B. It's very important to get familiar with these two color code standards if you are working in networking field, as these color coding standards are used to make Straight Through and Crossover Cables.

We start the article by having a look at what TIA/EIA 568A & 568B color coding standards are and then we will see how this is used in making Straight Through and Cross Over Cable. These standards are used on Ethernet wires and can also be classified as Ethernet Color Code.

Following diagram illustrates T568A and T568B RJ45 color code standard. On left is 568B and on right is 568A color code standard. We look into each of this standard one by one.

RJ45 color code connector ethernet cat5 cat6

RJ45 Color Code TIA/EIA 568A :

It is one the oldest color coding standard available these days but it's not widely used now a days. Introduced in mid 1980s, the color pattern in 568A standard is as follows

RJ45 Pin No Color Wire
1 Green White
2 Green
3 Orange White
4 Blue
5 Blue White
6 Orange
7 Brown White
8 Brown

RJ45 Color Code TIA/EIA 568B

The second TIA/EIA standard is 568B, it is not very old but is most popular color code standards and is used in making Straight through cable. The color pattern in 568B standard is as follows

RJ45 Pin No Color Wire
1 Orange White
2 Orange
3 Green White
4 Blue
5 Blue White
6 Green
7 Brown White
8 Brown

having getting familiarity with TIA/EIA 568Aand 568B its time to get how these two standards are used in straight through and crossover cable.

Crossover Cable Color Code :

Crossover cable is used to connect same type of networking devices. for example, they are used when connecting

Switch to Switch

Laptop to Laptop

Router to Router

Cross over cable can be made by using either 568A or 568B on one end of RJ45 connector while using opposite color coding at the other end. This means

If on one end we are using 568A, other end must uses 568B.

If on one end we are using 568B, other end must uses 568A

Following is an example of cross over cable. We can see that left side connector is using 568B while other end is using 568A. To summarize, both end of UTP cable should have opposite color coding standard.

RJ45 color code connector cable crossover a or b

There is a logic behind changing wire combination at 1,2,3 and 6 at both ends. We can see that wire 1 and 2 on left are terminating at 3 and 6 on the right, while 3 and 6 on left are going on 1 and 2 on right, rest combination at 4,5,7 and 8 are same at both ends. This is because crossover cable is used to connect different type of networking devices, so when device on left is sending at pin 1 and 2 its received at pin 3 and 6 on the right. Whereas pin 3 and 6 on left are receiving what devices on right is sending. Without this crossing of cable at both ends, communication between both different devices is not possible.

Straight Through Cable Color Coding:

Straight Through Cable is used to connect similar type of networking devices. You need this wire while you are connecting

Switch to Router

Router to Computer

Computer to switch

Following is a diagram that shows a Straight Through Cable that is using 568A color coding. It's difference from crossover cable is that, both end are following same type of color coding standard. Here both end of UTP cable has 568A color code standard.

Following is Straight Through Cable that is using 568B of Rj45 Color Coding standard. Both ends of this cable has 568B standard.

To summarize, if one end of UTP cable is using 568A color code standard than other end must also use 568A, same holds true for 568B.

Now that we have seen both 568A and 568B color code standard and how they used in making Straight Through or Crossover cable. We can see that both these standard have small difference only green and orange pairs are swapped while remaining combination remains unchanged.

Automatic Medium-Dependent Interface Crossover (Auto-MDIX)

It's important that if you are working in the field of computer networking then you must have knowledge about color code standards and which combination is used while making Straight Through or CrossOver Cable. It's also important to mention about Automatic Medium-Dependent Interface Crossover (Auto-MDIX) standard. Almost all networking devices available today supports Automatic Medium-Dependent Interface Crossover (Auto-MDIX) standard. The auto-MDIX standard has been devised so that devices can adjust automatically there sending and receiving pins, now devices by themselves can decide that which type of cable is used and adjust their sending and receiving parameter. Which means you can use straight through to connect same devices as well as different devices and same hold true to cross over cable.

So if you have only Straight Through Cable and you want to connect same type of devices like a switch to switch, you can connect them using Straight Through cable as both end of switches will adjust sending and receiving pins.

This video explain how to crimp pinout rj45 color code :