A telephone jack and a telephone plug are electrical connectors for connecting a telephone set or other telecommunications apparatus to the telephone wiring inside a building, establishing a connection to a telephone network. The plug is inserted into its counterpart, the jack, which is commonly affixed to a wall or baseboard. The standards for telephone jacks and plugs vary from country to country, though the 6P2C style modular plug has become by far the most common type.

A connection standard, such as RJ11, specifies not only the physical aspects of an electrical connector, but also the signal definitions for each contact, and the pinout of the device, i.e. the assignment or function of each contact. Modular connectors are specified for the registered jack (RJ) series of connectors, as well as for Ethernet and other connectors, such as 4P4C (4 position, 4 contacts) modular connectors, the de facto standard on handset cords, often improperly referred to as RJ connectors.

History Historically, telephones were typically owned by the telephone company, and were usually permanently wired to the telephone line. For some applications it was necessary or convenient to provide portable telephone sets that could be moved to a different location within the customer's premises. For this purpose telephone companies developed jacks and plugs in various designs with various numbers of contacts. Before , concentric connectors with three contacts were usually sufficient, but the upgrade of telephone sets to anti-sidetone circuitry in the 1930s required at least four conductors between a desk set and the subscriber set that contained the telephone hybrid and a ringer. For this purpose, Bell System engineers developed a cube-shaped four-prong plug (type no. 283) with uneven prong spacings to avoid improper insertion into the jack.AT&T, Jacks and Plugs, Bell System Practices, Section C36.201 Issue 1 (February 1, 1932)

The cubic design was changed to a round version (No. 505A) in the mid 1960s. The four-prong jack and plug combination was the standard line connection for all portable telephone sets until the conversion to modular jacks in the 1970s, typified by the Registered Jack standards promulgated in U.S. federal law.

Many countries initially used different specifications for connectors, and some national connector types remain in service, but few are used for new installations for which modular connector types are prescribed.

Connections The installation of a conventional wired telephone set has four connection points, each of which may be hardwired, but more often use a plug and socket: telephone line to phone cord: The wall jack. This connection is the most standardized, and often regulated as the boundary between an individual's telephone and the telephone network. In many residences, though, the boundary between utility-owned and household-owned cabling is a network interface on an outside wall known as the demarcation point; all wall jacks in the home are part of the household's internal wiring. telephone cord to telephone set base: This connection is generally not regulated, but instead follows de facto standards. It is often a 6P4C connector, which is often RJ11, but may be proprietary or hardwired. telephone set base to handset cord: By de facto standard, this is usually a 4P4C connector. handset cord to handset: The handset end of the straight-through handset cord also uses a 4P4C connector.

Some of these may be absent: Wired telephones may not have a separate base and handset. The defining characteristic of wireless telephones is that they do not have a handset cord, and the defining characteristic of mobile telephones is that they do not have a phone cord.

Wiring

A standard specifies both a physical connector and how it is wired. Sometimes the same connector is used by different countries but wired in different ways.

For example, telephone cables in the UK typically have a BS 6312 (UK standard) plug at the wall end and a 6P4C or 6P2C modular connector at the telephone end: this latter may be wired as per the RJ11 standard (with pins 3 and 4), or it may be wired with pins 2 and 5, as a straight-through cable from the BT plug (which uses pins 2 and 5 for the line, unlike RJ11, which uses pins 3 and 4). Thus cables are not in general compatible between different phones, as the phone base may have a socket with pins 2 and 5 (requiring a straight-through cable), or have an RJ11 socket (requiring a crossover cable).

When modular connectors are used, the latch release of the connector should be on the ridge side of flat phone wire in order to maintain polarity.

Though four wires are typically used in U.S. phone cabling, only two are necessary for telecommunication. In the event that a second line is needed, the other two are used. They are also sometimes used to provide power for telephone dial lamps (6 volts AC, as in the Princess phone), or other features.

List of plugs

Modular connectors

4P4C and 4P2C for handset cables (often erroneously referred to as RJ9, RJ10, and RJ22) 6P2C for RJ11 single telephone line 6P4C for RJ14 two telephone lines 6P6C for RJ25 three telephone lines 8P8C for RJ61X four telephone lines, RJ48S and RJ48C for four-wire data lines, RJ31X single telephone line with equipment disconnect, RJ38X (similar to RJ31X but with continuity circuit)

Other connectors 50-pin miniature ribbon connector for RJ21X, used for up to 25 lines for multiline phones such as the ITT 2564, key telephone systems such as the 1A2 Key System, and PBX systems.

International standards RJ11, by far the most common BS 6312, British F-010, French TAE connector, German

National standards TDO-connector, Austria WT-4, Polish and Eastern Bloc national standard, also adopted in Russia as ШТР-IV (SHTR-IV)

The Polish WT-4 plug is also adopted in the Eastern Bloc and Russia as ШТР-IV (SHTR-IV) and has four metal pins and an additional fourth dielectric pin. The corresponding socket comes in two variants. The GTN-4 socket (РТШ-IV (RTSH-IV) in Russia) provides a 4 pin connection (in most cases, the two rightmost pins are used for connecting a single line). The GTNC-4 (РТШК-IV, RTSHK-IV) is a GTN-4 socket that has an additional circuit. The 5th plastic pin of the inserted plug disconnects a 1μF capacitor that otherwise closes the circuit of the telephone line when the plug is not inserted. This feature allows testing the line when the phone is not plugged in. The usage of a capacitor is mostly obsolete and GTN-4 sockets produced later reuse the capacitor compartment for an additional RJ11 socket.

Legacy

600 series connector, Australia Protea, South Africa SS 455 15 50, Sweden and Iceland Telebrás plug, Brazil Tripolar plug, Italy BTicino 2021 (with or without line interruption), Italy (rare)

List by country or territory

This list covers only single-line telephone plugs commonly used in homes and other small installations; there are 44 different variations of plugs, including an Israeli version of BS6312 with different internal wiring of the pins, plus hard wiring to a junction box with no adapter. Special telephone sets use a variety of special plugs, for example micro ribbon for key telephone systems.

+PlacePlug typesAlbania 6P2CAlgeria F-010Argentina 6P2CAustralia 610, 6P2CAustria TDOBarbados 6P2CBelarus 6P2C, Polish national 5-pin (WT-4) Belgium Tetrapolar plug, 6P2CBolivia 6P2CBosnia 6P2C, 3-pin plug used in countries of former Yugoslavia Botswana BS 6312Brazil Telebrás plug, 6P2CBrunei 6P2CBulgaria 6P2C, Polish national 5-pin (WT-4) Canada 6P2CCayman Islands 6P2CChile 6P2CChina Mainland 6P2CColombia 6P2C, 2-pin national standardCosta Rica 6P2CCroatia 6P2C, 3-pin plug used in countries of former Yugoslavia Cyprus BS 6312, 6P2CUsed for ADSLCzech Republic 6P2C, 4-pin national plug Denmark 3-prong national standard, 6P2C Dominican Republic 6P2CEcuador 6P2CEgypt 6P2CCurrently the dominant plugEstonia 6P2C, Polish national 5-pin (WT-4) Faroe Islands 6P2CFinland 6P2C, Tripolar plug France F-010, 8P8C  (since 2003)Germany TAE, 8P8C Gibraltar BS 6312Greece 6P2C,Although other types can also be found Bipolar plug Hong Kong 6P2C,  BS 6312Hungary 6P2C, legacy 3 and 5-prong national standardIceland 6P2C, SS 455 15 50 India 6P2CIndonesia 6P2CIran 6P2CIreland 6P2C, 8P8C, Used for ISDN, Digital PBX, and office systems Israel BS 6312 but wired differently from the British Standard, 6P2CItaly 6P2C, Tripolar plug,  BTicino-2021Japan 6P2CKorea, Republic of 6-pin modular (6P4C or 6P2C), 8-pin modular (8P8C) or 3-position weatherproof connector in accord with TIA-1096-A.Legal regulation 4-prong connector The old standard ruled out after 2002 but still used widely.Latvia 6P2C, Polish national 5-pin (WT-4) Lithuania 6P2C, Polish national 5-pin (WT-4) Liechtenstein Reichle-connector, 4-pin Swiss telephone plugs Luxembourg 6P2C, 4-pin Luxembourgish telephone plug Malaysia 6P2CMalta BS 6312, 6P2C Mauritius F-010Mexico 6P2CMontenegro 6P2C, 3-pin plug used in countries of former Yugoslavia Morocco F-010, 6P2CMyanmar BS 6312Netherlands 6P2C, Nigeria6P2CNew Zealand BS 6312, 6P2C, 8P8C North Macedonia 6P2C, 3-pin plug used in countries of former Yugoslavia Norway 8P8C, Same plug used for POTS, ISDN and LAN Tripolar plug,  6-prong national standardFor local battery telephones, not used since approximately 1980Pakistan 6P2CPanama 6P2CPeru 6P2CPhilippines 6P2CPoland 6P2C, Polish national 5-pin (WT-4) coupled with 6P2C socket Portugal 6P2CAlso known as R.I.T.A.Romania 6P2C, 3-pin triangular plug similar to the Italian Tripolar plug,Rarely used today 5-pin R.S.-79.809Same as the Polish WT-4Russia 6P2C, Polish national 5-pin (WT-4) Senegal F-010Serbia 6P2C, 3-pin plug used in countries of former Yugoslavia Singapore 6P2CSlovenia 6P2C, 3-pin plug used in countries of former Yugoslavia Slovakia 6P2C, 4-pin national plug South Africa 6P2C, Protea, 8P8C Spain 6P2CSri Lanka 6P2CSweden SS 455 15 50, 6P2CSwitzerland Reichle-connector, 4-pin plugs Taiwan 6P2CThailand 6P2CTrinidad and Tobago 6P2CTurkey 6P2C, Tripolar plug Tunisia 6P2C, F-010 Ukraine 6P2C, Polish national 5-pin (WT-4) United Arab Emirates BS 6312United Kingdom BS 6312, 6P2CUsed for ADSL modem lines in British telephone socketsUnited States 6P2C and other Registered jacks, 4-pin Bell System plugs Uruguay 6P2CUSSR (history) Polish national 5-pin (WT-4)Venezuela 6P2CZimbabwe BS 6312, 6P2C

See also Network interface device Power plugs/sockets by country

References

External links

Telephone plug list—at Steve Kropla's World Wide Phone Guide How to install telephone wiring