What is an RJ45 connector? What's the difference between an RJ45 and an RJ11 connector?

A registered jack (RJ) is a standard telecommunications network component that forms part of the cabling system to connect devices to a network. The initial definition of registration interfaces was in the Universal Service Ordering Code (USOC) system of the Bell System. There are various interfaces, and here we will discuss two of them.

The RJ45 connector is an eight-pin standardised interface that allows a device to connect to a Local Area Network (LAN). The name RJ45 is an abbreviation for Registered Jack-45, and the digit 45 is the interface standard number. The development of this connector was initially limited to telephone communication uses, but nowadays has a wide range of applications.

Ethernet cables use these RJ45 connectors at both ends. Since the cable uses RJ45 connectors, they are often referred to as RJ45 cables and are used for connecting Ethernet networks with devices such as computers, printers, security cameras etc. Each RJ45 connector has eight pins, and hence each RJ45 Ethernet cable has eight wires with different colours.

The RJ11 connector is a six-pin analogue telephone interface connecting telephones and modems to the cable. The name RJ11 is an abbreviation of Registered Jack-11 and the digit 11 is the standard interface number. It is commonly used in telephone cabling systems.

An RJ11 jack is a six-pin position but may have four or six contacts used to carry the signal. In recent times, the use of RJ11 connectors has been popular for connecting modems and landlines.