Ethernet only requires 2 pairs of (4 cores) cables to complete the signal when using the twisted cylinder as the transmission medium. There are three standards in the fast Ethernet using twisted tunnels as the transmission medium: 100Base-TX, 100Base-T2, and 100BASE-T4.

Among them: 100BASE-T4 standards require all 4 pairs of lines to transmit signals, and the other two standards only require 2 pairs of lines. The most popular in the fast Ethernet is the 100BASE-TX standard, so when you buy the twisted pair used in the 100M network, do not use the twisted twisted wire with only two line pairs for a small cheaper in the figure. In the US Cable Standard (AWG), the three, 4, five, and super five types of twisted lines are defined as 4 pairs. In the Gigabit Ethernet, they require all 4 pairs of lines to communicate. Therefore, there should be 4 pairs of lines in the standard five types of cables.