CAT3, RJ11 Connections
A Registered Jack is a standardized telecommunication network interface for connecting voice and data equipment to a service provided by a local exchange carrier or long distance carrier. The specification includes physical construction, wiring, and signal semantics. Registered jacks are primarily named by the letters RJ, followed by two digits for the type. Suffixes indicate minor variations. RJ11, RJ14, and RJ25 are the most commonly used for telephones. Cable Supply offers a variety of Jacks and Modular Plugs.