Telephone jack and plug
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 RJ11 modular connector 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 series of connectors, as well as for Ethernet and other connectors, such as 4P4C 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 c. 1930, 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 with uneven prong spacings to avoid improper insertion into the jack.The cubic design was changed to a round version 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.
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 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, or it may be wired with pins 2 and 5, as a straight through cable from the BT plug. Thus cables are not in general compatible between different phones, as the phone base may have a socket with pins 2 and 5, or have an RJ11 socket.
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, or other features.
List of plugs
Modular connectors
- 4P4C and 4P2C for handset cables
- 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
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 National Standard, also adopted in Russia as ШТР-IV
Legacy
- 600 series connector, Australia
- Protea, South Africa
- SS 455 15 50, Sweden and Iceland
- Telebrás plug, Brazil
- Tripolar plug, Italy
- BTicino 2021, Italy
List by country or territory
| Place | Plug types |
| Albania | 6P2C |
| Algeria | F-010 |
| Argentina | 6P2C |
| Australia | 610, 6P2C |
| Austria | TDO |
| Barbados | 6P2C |
| Belarus | 6P2C, Polish national 5-pin |
| Belgium | Tetrapolar plug, 6P2C |
| Bolivia | 6P2C |
| Bosnia | 6P2C, 3-pin plug used in countries of former Yugoslavia |
| Botswana | BS 6312 |
| Brazil | Telebrás plug, 6P2C |
| Brunei | 6P2C |
| Bulgaria | 6P2C, Polish national 5-pin |
| Canada | 6P2C |
| Cayman Islands | 6P2C |
| Chile | 6P2C |
| China Mainland | 6P2C |
| Colombia | 6P2C, 2-pin national standard |
| Costa Rica | 6P2C |
| Croatia | 6P2C, 3-pin plug used in countries of former Yugoslavia |
| Cyprus | BS 6312, 6P2C |
| Czech Republic | 6P2C, 4-pin national plug |
| Denmark | 3-prong national standard, 6P2C |
| Dominican Republic | 6P2C |
| Ecuador | 6P2C |
| Egypt | 6P2C |
| Estonia | 6P2C, Polish national 5-pin |
| Faroe Islands | 6P2C |
| Finland | 6P2C, Tripolar plug |
| France | F-010, 8P8C |
| Germany | TAE, 8P8C |
| Gibraltar | BS 6312 |
| Greece | 6P2C, Bipolar plug in older installations |
| Hong Kong | 6P2C, BS 6312 |
| Hungary | 6P2C |
| Iceland | 6P2C, SS 455 15 50 |
| India | 6P2C |
| Indonesia | 6P2C |
| Iran | 6P2C |
| Ireland | 6P2C, 8P8C, |
| Israel | BS 6312 but wired differently from the British Standard, 6P2C |
| Italy | Tripolar plug, 6P2C, BTicino-2021 |
| Japan | 6P2C |
| Korea, Republic of | 6-pin modular, 8-pin modular or 3-position weatherproof connector in accord with TIA-1096-A. 4-prong connector |
| Latvia | 6P2C, Polish national 5-pin |
| Lithuania | 6P2C, Polish national 5-pin |
| Liechtenstein | Reichle-connector, 4-pin Swiss telephone plugs |
| Luxembourg | 6P2C, 4-pin luxembourgish telephone plug |
| Malaysia | 6P2C |
| Malta | BS 6312, 6P2C |
| Mauritius | F-010 |
| Mexico | 6P2C |
| Montenegro | 6P2C, 3-pin plug used in countries of former Yugoslavia |
| Morocco | F-010, 6P2C |
| Netherlands | 6P2C, Dutch telephone plug |
| Nigeria | 6P2C |
| New Zealand | BS 6312, 6P2C, 8P8C |
| North Macedonia | 6P2C, 3-pin plug used in countries of former Yugoslavia |
| Norway | 8P8C, Tripolar plug, :Image:Telephone plugs Norway.jpg|6-prong national standard |
| Pakistan | 6P2C |
| Panama | 6P2C |
| Peru | 6P2C |
| Philippines | 6P2C |
| Poland | 6P2C, Polish national 5-pin coupled with 6P2C socket |
| Portugal | 6P2C |
| Romania | 6P2C, 3-pin triangular plug similar to the Italian Tripolar plug, 5-pin R.S.-79.809 |
| Russia | 6P2C, Polish national 5-pin |
| Senegal | F-010 |
| Serbia | 6P2C, 3-pin plug used in countries of former Yugoslavia |
| Singapore | 6P2C |
| Slovenia | 6P2C, 3-pin plug used in countries of former Yugoslavia |
| Slovakia | 6P2C, 4-pin national plug |
| South Africa | 6P2C, Protea, 8P8C |
| Spain | 6P2C |
| Sri Lanka | 6P2C |
| Sweden | SS 455 15 50, 6P2C |
| Switzerland | Reichle-connector, 4-pin plugs |
| Taiwan | 6P2C |
| Thailand | 6P2C |
| Trinidad and Tobago | 6P2C |
| Turkey | 6P2C, Tripolar plug in older installations |
| Tunisia | 6P2C, F-010 in older installations |
| Ukraine | 6P2C, Polish national 5-pin |
| United Arab Emirates | BS 6312 |
| United Kingdom | BS 6312, 6P2C |
| United States | 6P2C and other Registered jacks, 4-pin Bell System plugs |
| Uruguay | 6P2C |
| USSR | Polish national 5-pin |
| Venezuela | 6P2C |
| Zimbabwe | BS 6312, 6P2C |