RJ45 network cable plug, also known as crystal head, is made of eight cores, and is widely used to connect the network cable (called Category V cable or twisted pair cable) between LAN and ADSL broadband Internet users' network equipment. In specific applications, RJ45 plug and network cable have two connection methods (line sequence), which are called T568A line sequence and T568B line sequence respectively.

The identification method of RJ45 network cable plug pin number is: hold the plug in your hand, with one end of 8 small gold-plated pieces facing upward, and the end of the rectangular large opening with the network cable installed downward. At the same time, face the one without the slender plastic pin to your eyes, and start from the first small gold-plated piece on the left to the first, second,..., and eighth pins successively.