RJ45 is a common network connector in our life. It is mainly divided into RJ45 adapter and RJ45 connecting cable, which are mainly used for network connection. RJ45 is an indispensable part of our network work. Now, with the extensive development of e-commerce, more and more manufacturers have begun to produce related network devices, adapters, connecting wires, or various parts. RJ45 connecting cable and adapter is one of the most frequently used and cheapest products among many network related components.

There are two types of common RJ45 interfaces: DTE for Ethernet network cards, router Ethernet interfaces, and DCE for switches.

DTE can be called "data terminal equipment", and DCE can be called "data communication equipment". In a sense, DTE devices are called "active communication devices" and DCE devices are called "passive communication devices". When two devices of the same type use RJ45 interface to connect for communication, cross cable connection must be used. This can be explained from the following RJ45 DTE type pin definitions and RJ45 DCE type pin definitions