T568A vs T568B: Which One Should I Choose?

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As is known to all, the colored wires should be positioned correctly when terminating the network cable. T568A and T568B are wiring standards set by ANSI (American National Standards Institute), TIA (Telecommunications Industry Association ), and EIA (Electronic Industries Association). T568A and T568B can also be called TIA/EIA568A and TIA/EIA568B as their standard name.

You may be confused about how to choose one when terminating an RJ45 jack or for Cat5, Cat5e, Cat6, Cat6a Cat7, and Cat8.

Two Types of Ethernet Cables

Two types of Ethernet cables are widely used in networking transmission: straight-through cable and crossover cable. Straight-through cable has a single wiring standard and both ends of the RJ45 connector use the T568A wiring standard or T568B wiring standard; while crossover cable has one end of T568A and the other end of T568B.

t568a vs t568b

In the past, these two types of network cables were necessary as the network interface card cannot recognize the wire order of network cables and a crossover cable was necessary when you need to connect the two same devices. For example, a crossover cable is used to connect a computer to a computer, a router to a router, and a switch to a switch.

But nowadays, it is recommended to use the same wiring schemes at both ends of the RJ45 connector. With the development of Auto MDI-X technology, the network equipment can automatically recognize whether the other device is the same and almost all users choose straight-through cable.

So, do you know what is T568A and T568B as well as the difference between them? The following will help you know more information about T568A and T568B so that you will further know how to choose them.

T568A vs T568B: The Similarity

Both T568A and T568B are used to offer a wiring scheme for terminating CAT cables to RJ45 connectors. Usually, an RJ45 connector has 8 positions, which means that the data transmission needs 8 conductors and they are generally twisted into 4 pairs. And the four main colors of T568A or T568B wiring standard are green, orange, blue, and brown.

T568A vs T568B: The Difference

Different Color Order

You can see from the diagram that the obvious difference between T568A and T568B is the switching of green and orange pin positions.

 Pin 1 2 3 4 5 6 7 8
T568A white/green green white/orange blue white/blue orange white/brown brown
T568B white/orange orange white/green blue white/blue green white/brown brown

t568a vs t568b

Different Backward Compatibility

T568A wiring scheme is compatible with one pair or two pairs of USOC wiring schemes, while T568B is only compatible with a pair of USOC wiring schemes. But T568B wiring standard can also match the AT&T 258A color code.

Different Application

T568A wiring scheme is used to interconnect dual computers and T568B is used to connect switches, HUBs, and other devices.

The Importance of Using Wiring Standard

The test data shows that the network cable using the standard color order has a dense strand of network cables and the signal attenuation during the transmission will be reduced. What's more, the transmission distance of the network cable can also be relatively long. But if you don’t use the standard color order, you may see no obvious change on short cables, but it may cause data loss or even interruption on long cables. So, you should definitely use the wiring standard of T568A or T568B.

A Brief Guide to Choose T568A or T568B

Different Scenarios

  1. In commercial applications, T568B has widespread use in telecom installation. But if you have old technology such as old fax devices or phones, T568A is recommended for you for its powerful backward compatibility.
  2. If you have the project guideline, please follow the recommended wiring scheme.
  3. If you need to upgrade or expand the current network, continue to use the same wiring scheme

In fact, T568A and T568B have subtle differences and one is no better than the other. All you need to do is to choose one, and then stick with it! But if you are hesitating about it, I recommend you to use the T568B wiring standard and remember to choose the right wire.

T568B Wiring Standard

Although there are two wiring standards, T568B wiring standard is chosen by most people. On the one hand, the network equipment and terminal connection are generally using the T568B wiring standard; on the other hand, T568B is more cost-effective.


Wire Diagram for T568B

 RJ45 Pin Wire Color 10Base-T Signal 100Base-TX Signal 1000Base-T Signal
1 white/orange Transmit + Transmit + BI_DA+ (TX+)
2 orange Transmit – Transmit – BI_DA- (TX-)
3 white/green Receive + Receive + BI_DB+ (RX+)
4 blue Unused Unused BI_DC+
5 white/blue Unused Unused BI_DC-
6 green Receive – Receive – BI_DB- (RX-)
7 white/brown Unused Unused BI_DD+
8 brown Unused Unused BI_DD-

T568B wiring scheme has been widely used in different scenarios and is popular among users as it can be compatible with AT&T 258A color code and it also meets the current and future needs.

How to Make A Cat6 Cat6a T568B Network Cable?

Step 1: Put the strain relief boot through the cable

step 1

Step 2: Cut off the jacket by a stripper

step 2 

Step 3: Make the wires straight and arrange them in T568B wiring scheme

step 3

Step 4: Check it again to see if the color order is right

step 4

Step 5: Cut wires

step 5

Step 6: Insert the RJ45 connector into the cable

step 6

Step 7: Crimp the RJ45 connector

step 7

Step 8: Make the other end by the same way

step 8

Step 9: Do the test to make sure whether the Ethernet cable can work well

step 9


What happens if you mix T568A and T568B?

Never mix T568A and T568B. If you mix them, it will cause troublesome errors.

How do I know which one should I use?

If a new network is about to be built up, you're free to choose any type of wiring scheme according to your own needs. But if there is already a network infrastructure, you should make an effort to find out which wiring scheme was used and update the network within the original standard.

Is there a speed difference between T568A and T568B?

No, the only difference between T568A and T568B is the change of green and orange color codes.


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