Serial Standard for Twisted Pair

In North America, the three most influential cabling organizations in the world are as follows. ANSI (American National Standards Institute, American National Standards Institute) TIA (Telecommunication Industry Association, American Telecommunications Industry Association) EIA (Electronic Industries Alliance, American Electronics Industry Association). Since TIA and ISO often coordinate in the formulation of standards, the differences between the standards promulgated by TIA and ISO are not very large. In North America and even the world, the most widely used twisted pair standards are ANSI/EIA/TIA-568A and ANSI/EIA/TIA-568B (actually it should be ANSI/EIA/TIA-568B.1, referred to as T568B for short ). The main difference between the two standards is the difference in the core sequence:

The line sequence definitions of EIA/TIA 568A are green-white, green, orange-white, blue, blue-white, orange, brown-white, and brown, and their labels are shown in the following table:

green and white	green	orange white	Blue	blue and white	Orange	brown and white	brown
1	2	3	4	5	6	7	8

The line sequence definitions of EIA/TIA 568B are orange-white, orange, green-white, blue, blue-white, green, brown-white, and brown, and their labels are shown in the following table:

orange white	Orange	green and white	Blue	blue and white	green	brown and white	brown
1	2	3	4	5	6	7	8

According to the 568A and 568B standards, the functions of the RJ-45 connectors (commonly known as crystal heads) in the network connection are: 1, 2 for sending, 3, 6 for receiving. , 4, 5, 7, and 8 are bidirectional lines; for the twisted pair connected to it, in order to reduce mutual interference, the standard requires that 1 and 2 must be a pair of twisted wires, and 3 and 6 must also be twisted. A pair of wires, 4 and 5 are twisted with each other, and 7 and 8 are twisted with each other.

It can be seen that there is no essential difference between the two standards, 568A and 568B, but the line sequence of the eight twisted pairs when connecting RJ-45 is different. In actual network engineering construction, the 568B standard is often used.