Telephones were generally hardwired, but may have been installed with Bell System connectors to permit portability. In the Bell System, following the Communications Act of 1934, the telephone companies owned all telecommunications equipment and they did not allow interconnection of third-party equipment. The intent was to establish a universal standard for wiring and interfaces, and to separate ownership of in-home (or in-office) telephone wiring from the wiring owned by the service provider. Customers are responsible for all jacks, wiring, and equipment on their side of the MPOE. The MPOE is a utility box, usually containing surge protective circuitry, which connects the wiring on the customer's property to the communication provider's network. The wired communications provider (telephone company) is responsible for delivery of services to a minimum (or main) point of entry ( MPOE). These interfaces used newly standardized jacks and plugs, primarily based on miniature modular connectors. Registration interfaces were created by the Bell System under a Federal Communications Commission order for the standard interconnection between telephone company equipment and customer premises equipment. 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 equipped. 6P indicates a six-position modular plug or jack. The nomenclature for modular connectors is based on the number of contact positions and the number of wires connected. It is commonplace, but not strictly correct, to refer to the unwired connectors or the (male) plugs by these names. The RJ standards designations only pertain to the wiring of the (female) jacks, hence the name Registered Jack. These are the RJ11, RJ14, and RJ25 interfaces. 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. 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. Modular connectors were developed to replace older telephone installation methods that used hardwired cords or bulkier varieties of telephone plugs. The same modular connector type may be used for different registered jack applications. 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. For example, RJ11 uses a six-position two-conductor connector ( 6P2C), RJ14 uses a six-position four-conductor ( 6P4C) modular jack, while RJ21 uses a 25-pair (50-pin) miniature ribbon connector. The connectors used for registered jack installations are primarily the modular connector and the 50-pin miniature ribbon connector. Although these standards are legal definitions in the United States, some interfaces are used worldwide. For example, RJ11, RJ14, and RJ25 are the most commonly used interfaces for telephone connections for one-, two-, and three-line service, respectively. Additional letter suffixes indicate minor variations. Accordingly, registered jacks are primarily named by the letters RJ, followed by two digits that express the type. The specification includes physical construction, wiring, and signal semantics. Registered jack connections began to see use after their invention in 1973 by Bell Labs. They were subsequently codified in title 47 of the Code of Federal Regulations Part 68. 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. 6P6C jack, may be used for RJ11, RJ14, and RJ25.Ī 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.eight-contact 8P8C plug used for RJ45S, RJ49, RJ61 and others.
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