Registered Jack Wikipedia

Telecommunication network interface

Left to right, modular connectors: * eight-contact 8P8C plug used for RJ45S, RJ49, RJ61 and others.
* six-contact 6P6C plug used for RJ25
* four-contact 6P4C plug used for RJ14
* four-contact 4P4C handset plug
* 6P6C jack, may be used for RJ11, RJ14, and RJ25.

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.[1] They were subsequently codified in title 47 of the Code of Federal Regulations Part 68.[2][3][4] Registered jack connections began to see use after their invention in 1973 by Bell Labs.[5]The specification includes physical construction, wiring, and signal semantics. Accordingly, registered jacks are primarily named by the letters RJ, followed by two digits that express the type. Additional letter suffixes indicate minor variations. For example, RJ11, RJ14, and RJ25 are the most commonly used interfaces for telephone connections for one-, two-, and three-line service, respectively. Although these standards are legal definitions in the United States, some interfaces are used worldwide.

The connectors used for registered jack installations are primarily the modular connector and the 50-pin miniature ribbon connector. 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.

Naming standard[edit]
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 plugs.

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 wires connected. 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 equipped.

History and authority[edit]
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.[citation needed] These interfaces used newly standardized jacks and plugs, primarily based on miniature modular connectors.

The wired communications provider (telephone company) is responsible for delivery of services to a minimum (or main) point of entry (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. Customers are responsible for all jacks, wiring, and equipment on their side of the MPOE. 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.

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. Telephones were generally hardwired, but may have been installed with Bell System connectors to permit portability. The legal case Hush-A-Phone v. United States (1956) and the Federal Communications Commission’s (FCC) Carterfone (1968) decision brought changes to this policy, and required the Bell System to allow some interconnection, culminating in the development of registered interfaces using new types of miniature connectors.

Registered jacks replaced the use of protective couplers provided exclusively by the telephone company. The new modular connectors were much smaller and cheaper to produce than the earlier, bulkier connectors that were used in the Bell System since the 1930s. The Bell System issued specifications for the modular connectors and their wiring as Universal Service Order Codes (USOC), which were the only standards at the time. Large customers of telephone services commonly use the USOC to specify the interconnection type and, when necessary, pin-assignments, when placing service orders with a network provider.

When the U.S. telephone industry was reformed to foster competition in the 1980s, the connection specifications became federal law, ordered by the FCC and codified in the Code of Federal Regulations (CFR), Title 47 CFR Part 68, Subpart F,[2] superseded by T1.TR5-1999.[3]

In January 2001, the FCC delegated responsibility for standardizing connections to the telephone network to a new private industry organization, the Administrative Council for Terminal Attachments (ACTA).[4] For this delegation, the FCC removed Subpart F from the CFR and added Subpart G. The ACTA derives its recommendations for terminal attachments from the standards published by the engineering committees of the Telecommunications Industry Association (TIA). ACTA and TIA jointly published the standard TIA/EIA-IS-968,[6] replacing the CFR information.

TIA-968-A, the current version of that standard,[6] details the physical aspects of modular connectors, but not the wiring. Instead, TIA-968-A incorporates the standard T1.TR5-1999, “Network and Customer Installation Interface Connector Wiring Configuration Catalog”,[3] by reference. With the publication of TIA-968-B, the connector descriptions have been moved to TIA-1096-A.[4] A registered jack name, such as RJ11, still identifies both the physical connectors and the wiring (pinout) for each application.

6P4C crimp-on style connector commonly used for RJ11 and RJ14

The most widely implemented registered jack in telecommunications is the RJ11. This is a modular connector wired for one telephone line, using the center two contacts of six available positions. This configuration is also used for single-line telephones in many countries other than the United States. It may also use a 6P4C connector, to use an additional wire pair for powering lamps on the telephone set. RJ14 is similar to RJ11, but is wired for two lines and RJ25 has three lines. RJ61 is a similar registered jack for four lines, but uses an 8P8C connector.

The RJ45S jack is rarely used in telephone applications but a standard version of the 8P8C modular connector used by RJ45S is used in Ethernet networks and the connector is often referred to as RJ45 in this context.

Officially recognized types of registered jacksCodeConnectorUsageRJA1X225A adapterConnector for a modular plug to a four-prong jackRJA2X267A adapterConnector for splitting one modular jack to two modular jacksRJA3X224A adapterConnector for adapting a modular plug to a 12-prong jackRJ2MB50-pin2–12 telephone lines with make-busy arrangementRJ11(C/W)6P2CEstablishes a bridged connection for one telephone line (6P4C if power on second pair)RJ12(C/W)6P6CEstablishes a bridged connection for one telephone line with key telephone system control ahead of line circuitRJ13(C/W)6P4CSimilar to RJ12, but behind the line circuitRJ14(C/W)6P4CFor two telephone lines (6P6C if power on third pair)RJ15C3-pin weatherproofFor one telephone line for boats in marinasRJ18(C/W)6P6CFor one telephone line with make-busy arrangementRJ21X50-pinMultiple (up to 25) line bridged T/R configurationRJ25(C/W)6P6CFor three telephone linesRJ26X50-pinFor multiple data lines, universalRJ27X50-pinFor multiple data lines, programmedRJ31X8P8CAllows an alarm system to seize the telephone line to make an outgoing call during an alarm. Jack is placed closer to the network interface than all other equipment. Only 4 conductors are used.RJ32X8P8CLike RJ31X, this wiring provides a series tip and ring connection through the connecting block, but is used when the customer premises equipment is connected in series with a single station, such as an automatic dialer.RJ33X8P8CThis wiring provides a series tip and ring connection of a KTS line ahead of the line circuit because the registered equipment requires CO/PBX ringing and a bridged connection of the A and A1 lead from behind the line circuit. Tip and ring are the only leads opened when the CPE plug is inserted. Typical usage is for customer-provided automatic dialers and call restrictors.RJ34X8P8CSimilar to RJ33X, but all leads are connected behind the line circuit.RJ35X8P8CThis arrangement provides a series tip and ring connection to whatever line has been selected in a key telephone set plus a bridged A and A1 lead.RJ38X8P4CSimilar to RJ31X, with a continuity circuit. If the plug is disconnected from the jack, shorting bars allow the phone circuit to continue to the site phones. Only 4 conductors are used.RJ41S8P8C, keyedFor one data line, universal (fixed loop loss and programmed)RJ45S8P8C, keyedFor one data line, with programming resistorRJ48C8P4CFor four-wire data line (DSX-1)RJ48S8P4C, keyedFor four-wire data line (DDS)RJ48X8P4C with shorting barFor four-wire data line (DS1)RJ49C8P8CFor ISDN BRI via NT1RJ61X8P8CFor four telephone linesRJ71C50-pin12-line series connection using 50-pin connector (with bridging adapter) ahead of customer equipment. Mostly used for call sequencer equipment.Many of the basic names have suffixes that indicate subtypes:

* C: flush-mount or surface mount
* F: flex-mount
* W: wall-mount
* L: lamp-mount
* S: single-line
* M: multi-line
* X: complex jack

For example, RJ11 comes in two forms: RJ11W is a jack from which a wall telephone can be hung, while RJ11C is a jack designed to have a cord plugged into it. A cord can be plugged into an RJ11W as well.

RJ11, RJ14, RJ25 wiring [edit]
6P6C connector showing the location of pin 1

All of these registered jacks are described as containing a number of potential contact positions and the actual number of contacts installed within these positions. RJ11, RJ14, and RJ25 all use the same six-position modular connector, thus are physically identical except for the different number of contacts (two, four and six respectively) allowing connections for one, two, or three telephone lines respectively.

Cords connecting to an RJ11 interface require a 6P2C connector. Nevertheless, cords sold as RJ11 often use 6P4C connectors (six position, four conductor) with four wires. Two of the six possible contact positions connect tip and ring, and the other two conductors are unused.

The conductors other than the two central tip and ring conductors are in practice variously used for a second or third telephone line, a ground for selective ringers, low-voltage power for a dial light, or for anti-tinkle circuitry to prevent pulse dialing phones from sounding the bell on other extensions.

Observing the male connector from the cable opening, with prong facing downward, the pins are numbered 1–6, left to right:

PositionPairTip or
Ring
±RJ11RJ14RJ25U.S. Bell System colors[A]25-pair color code[B]German colors[C]Australian colorsDutch colors[8]13T+T3