Editing Registered jack (section)

==Naming standard==
The registered jack designations originated in the standardization process of telephone connections in the Bell System in the United States, and describe application circuits and not just the physical geometry of the connectors. The same modular connector type may be used for different registered jack applications. Modular connectors were developed to replace older telephone installation methods that used hardwired cords or bulkier varieties of [[telephone plug]]s.

Strictly, ''Registered Jack'' refers to both the female physical connector ([[modular connector]]) and specific wiring patterns, but the term is often used loosely to refer to modular connectors regardless of wiring, gender, or use, commonly for telephone line connections, but also for [[Ethernet over twisted pair]], resulting in confusion over the various connection standards and applications. For example, the six-position physical connector, plug and jack, is identically dimensioned and inter-connectable, whether it is wired for one, two, or three lines. These are the RJ11, RJ14, and RJ25 interfaces. The RJ standards designations only pertain to the wiring of the (female) jacks, hence the name ''Registered Jack''. It is commonplace, but not strictly correct, to refer to the unwired connectors or the (male) plugs by these names.

The nomenclature for modular connectors is based on the number of contact positions and the number of contacts present. ''6P'' indicates a six-position modular plug or jack. A six-position modular plug with conductors in only the middle two positions is designated ''6P2C''; 6P4C has four conductors in the middle positions, and 6P6C has all six. An RJ11 without power, if made with a 6P6C connector, has four unused contacts.