RJ11 History and authority

History and authority

For more details on this topic, see Interconnection.

Registration interfaces were created by the Bell System under a 1976 Federal Communications Commission order for the standard interconnection between telephone company equipment and customer premises equipment. These interfaces used newly standardized jacks and plugs, primarily based on miniaturemodular 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 allowinterconnection 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. USOCs are commonly specified to the communications provider by large businesses for a variety of services. Because there are many standardized interface options available to the customer, the customer must specify the type of interface required by RJ/USOC. For a multi-line interface such as the RJ21 (which provided 25 pairs), the customer must denote which position(s) of the interface are to be used. If there are multiple RJ21 connectors, they are numbered sequentially and the customer must advise the communications provider of which one to use.

When the US telephone industry was opened to more competition in the 1980s, the specifications became US 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[4] (ACTA). The FCC removed Subpart F from the CFR and added Subpart G, which delegates the task to the ACTA. The ACTA generates its recommendations for terminal attachments from the standards published by the engineering committees of the Telecommunications Industry Association (TIA). ACTA and TIA jointly published a standard called TIA/EIA-IS-968[5] which contained the information that was formerly in the CFR.

The current version of that standard, called TIA-968-A,[5] specifies the modular connectors at length, but not the wiring. Instead, TIA-968-A[5] incorporates a standard called T1.TR5-1999, "Network and Customer Installation Interface Connector Wiring Configuration Catalog",[3] by reference to specify the wiring. With the publication of TIA-968-B,[4] the connector descriptions have been moved to TIA-1096-A.[4] Note that a registered jack name such as RJ11 identifies both the physical connectors and the wiring (pinout) of it (see above).

Registered jack types

The most commonly recognized registered jack is the RJ11. This is a modular connector wired for one analog telephone line, using the center two contacts of six available positions, and is found in most homes and offices in most countries for single-line telephones. 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. Telephone line cords with modular plugs are intended most often for RJ11 and RJ14.

The RJ45(S) jack is rarely used, but the designation RJ45 commonly refers to any 8P8C modular connector.

List of official registered jacks

Code     Connector           Usage

RJA1X    225A adapter     Connector for a modular plug to a four-prong jack

RJA2X    267A adapter     Connector for splitting one modular jack to two modular jacks

RJA3X    224A adapter     Connector for adapting a modular plug to a 12-prong jack

RJ2MB  50-pin micro ribbon

2–12 telephone lines with make-busy arrangement

RJ11(C/W)           6P2C

Establishes a bridged connection for one telephone line (6P4C if power on second pair)

RJ12(C/W)           6P6C

Establishes a bridged connection for one telephone line with key telephone system controlahead of line circuit

RJ13(C/W)           6P4C

Similar to RJ12, but behind the line circuit

RJ14(C/W)           6P4C

For two telephone lines (6P6C if power on third pair)

RJ15C    3-pin weatherproof        For one telephone line for boats in marinas

RJ18(C/W)           6P6C

For one telephone line with make-busy arrangement

RJ21X    50-pin micro ribbon

For up to 25 lines

RJ25(C/W)           6P6C

For three telephone lines

RJ26X    50-pin micro ribbon

For multiple data lines, universal

RJ27X    50-pin micro ribbon

For multiple data lines, programmed

RJ31X    8P8C

Allows 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.

RJ32X    8P8C

Like RJ31X, this wiring provides a series tip and ring connection through the connecting block, but is used when the customer premise equipment is connected in series with a single station, such as an automatic dialer.

RJ33X    8P8C

This 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.

RJ34X    8P8C

Similar to RJ33X, but all leads are connected behind the line circuit.

RJ35X    8P8C

This 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.

RJ38X    8P4C

Similar 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.

RJ41S     8P8C, keyed

For one data line, universal (fixed loop loss and programmed)

RJ45S     8P8C, keyed

For one data line, with programming resistor

RJ48C    8P4C

For four-wire data line (DSX-1)

RJ48S     8P4C, keyed

For four-wire data line (DDS)

RJ48X    8P4C with shorting bar   For four-wire data line (DS1)

RJ49C    8P8C

For ISDN BRI via NT1

RJ61X    8P8C

For four telephone lines

RJ71C    50-pin micro ribbon

12 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.)