The RJ45 is a type of information socket (ie, communication terminal) connector in the wiring system. The connector consists of a plug (connector, crystal head) and a socket (module).

The plug has 8 grooves and 8 contacts. RJ is the abbreviation of Registered Jack, which means "registered socket".

In the FCC (Federal Communications Commission Standards and Regulations), RJ is the interface that describes the public telecommunications network. The RJ45 of the computer network is a common name for the standard 8-bit modular interface.