Registered Jack (RJ) is a standard for telecommunication network interface for connecting cables for voice and data equipment to a service provided by a local exchange carrier and long distance carrier. A registered jack is simply a female connector. In the beginning registered jack was regulated by FCC (Federal Communications Commission) as a standard interface Telecommunication. Telecommunication companies are only responsible for delivery of their services for minimum port of entry especially for Telephone. The standard Registered Jack was only designed for ISDN (Integrated Services Digital Network). Nonetheless, in 1990 modular jacks were internationally standardized in IEEE 802.3i.
Variety of Standard Jacks are now available depending upon their application few most commonly used are:
- RJ 11 Connector: This is the most common modular form of Registered Jack. It is found in houses and offices where old telephone wired systems are connected with the ISP’s line.
- RJ 14 and RJ 61 Connector: These designs are similar to RJ-11, however they are designed for two lines and four lines respectively. At termination of twisted pair cables and uses an eight pin modular connector for cables RJ 61 is used.
- RJ 25 Connector: For three lines connection RJ 25 connector was introduced.
- RJ 21 Connector: With 50 conductors to implement 25 lines at a time this jack was designed. These connectors are used in area networks with multiple switches and other communication devices.
- RJ 45 Connector: An 8-pin plug or jack is normally used to connect two or more computers onto Ethernet based Local Area Networks (LAN).
- RJ 11s Connector: A suffix is added to indicate a slight addition in functionality with respect to its common version which was RJ 11. For example, the suffix ‘w’ means that this is used so the telephone set can be hung on the wall.
- RJ 48 Connector: RJ 48 Connector, using an eight position modular connector for local area networks (LANs), T1 and ISDN termination.