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TIA/EIA T568A VS. T568B

[Q] What is the difference between the TIA/EIA standards 568-A and 568-B? [A] In order to explain the standard correctly, we must first discuss a little history that is relevant to this standard. In 1985, the Computer Communications Industry Association requested that the Electronic Industries Alliance (EIA) to develop standards for the cabling used in telecommunications applications. The first revision of this standard was released in 1991, but was later updated again in 1995 due to the massive development of networking technology and new faster high-speed ethernet cables and networking components. This was also replaced later with the current TIA/EIA 568-B standard. Although many aspects of networking structure and performance are addressed in these standards, the most visible and often misunderstood component is the definition of the wiring assignments in the RJ45 plug. A colored wire must be placed in a specific pin location in the plug in order for the cable to meet the standard. It is these wiring assignments that differ between the T568A and T568B standard. The pins on the RJ45 plug are numbered 1 to 8. If you are holding a CAT 5 patch cable in your hand, as if inserting into a jack, with the contacts facing in the up position, pin 1 will be on the far left. Pin 8 will be the pin on the far right. This is the orientation we will use when we define the wiring assignments in the RJ45 plug and making understanding this easy. CAT 5 Cable has four twisted pairs within the sheath. Each pair has a specific color code, and is to placed into deliberate pin location within the RJ45 plug. We will now identify the wiring locations in each of the standards: TIA/EIA 568-A (T568A) Pin 1 - white / green stripe Pin 2 - green Pin 3 - white / orange stripe Pin 4 - blue Pin 5 - white / blue stripe pin 6 - orange pin 7 - white / brown stripe pin 8 - brown TIA/EIA 568-B (T568B) Pin 1 - white / orange stripe Pin 2 - orange Pin 3 - white / green stripe Pin 4 - blue Pin 5 - white / blue stripe Pin 6 - green Pin 7 - white / brown stripe Pin 8 - brown If you are making a patch cable, you will construct the cable using identical pin assignments on each end. Although it does not matter which standard you use for this, the 568-B standard is usually used in the United States. If you are making a crossover cable, you will construct the cable using the 568-A standard on one end, and the 568-B standard on the other. Mistakes are easily made when making crossover cables, so if you do not have experience with this type of work do not hesitate to get an experienced installer. It is always best to defer this to a professional. It is vitally important to use the very best material that you can get in the construction of the cable, and that a top quality crimper is used as well. Make certain that the cable is checked using a test meter, to ensure that the wiring sequence is correct on each end. Remember, the 568-B standard is used in virtually every application in the United States, so make sure you discuss this before starting your project. In some cases, there may be special reasons to use the 568-A standard. Special projects and temporary runs have been made specifying the 568-A standard, to serve as an easily distinguished visual cue for those servicing the network. Other situations may exist as well that call for this application. If you have any questions about which standard is most appropriate for your specific installation, refer to a qualified network specialist. CAT 5 Cable Company provides CAT 5 and CAT 5e patch and crossover cables for all networking applications in 9 colors, and any custom length. Hand assembled and 100% tested to ensure the finest quality. RELATED FAQ QUESTION: What is the difference between CAT 5 and CAT 5e cable? Keywords: Cat 5, Cat 5e, Cat 6, Ethernet cable, patch cable, crossover cable