Connectors

Modular connector or RJ (registered jack) 

 A standardized physical network interface—both jack construction and wiring pattern—for connecting telecommunications or data equipment to a service provided by a local exchange carrier or long distance carrier. The standard designs for these connectors and their wiring are named RJ11, RJ14, RJ21,RJ35, RJ45, RJ48, etc. Many of these interface standards are commonly used in North America, though some interfaces are used world-wide. It is common to find a dash (hyphen) between the RJ and the number, but the actual standard has no dash or hyphen.