Registered jack
（重定向自Universal Service Order Code）
![Left to right, modular connectors: eight-contact 8P8C plug (used for RJ45S, RJ49, RJ61 and others)six-contact 6P6C plug used for RJ25four-contact 6P4C plug used for RJ14 (often also used instead of 6P2C for RJ11)four-contact 4P4C handset plug (also popularly called](/Images/godic/202502/18/Rjxx0231.jpg")
![6P4C crimp-on style connector commonly used for RJ11 and RJ14](/Images/godic/202502/18/Conector_RJ110231.jpg")
![6P6C connector showing the location of pin 1](/Images/godic/202502/18/Rj25_connector0231.jpg")
A Registered Jack (RJ) 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. Registration interfaces were first defined in the Universal Service Ordering Code (USOC) system of the Bell System in the United States for complying with the registration program for customer-supplied telephone equipment mandated by the Federal Communications Commission (FCC) in the 1970s. They were subsequently codified in the Code of Federal Regulations Part 68.