What is a Registered Jack - 11?
RJ-11 is a telephone interface that uses a cable of twisted wire pairs and a modular jack with two, four or six contacts. RJ-11 is a common connector for plugging a telephone into the wall and the handset into the telephone.
The most familiar registered jack is probably the RJ11. It is a modular connector wired for one plain old telephone service line (using two wires out of six available positions), and is found in most homes and offices in most countries of the world for single-line telephones.
Cables sold as RJ11 often use 6P4C RJ14 connectors (six position, four conductor) with four wires running to a central junction box. Two of its six possible contact positions connect tip and ring, and the other two conductors are then unused. 6P2C and 6P6C can also be found in stores.