Telephone plug

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A modular connector plug (6P6C) and socket (6P4C).

A telephone plug is a type of connector used to connect a telephone set to the telephone wiring inside a building, establishing a connection to a telephone network. It is inserted into its counterpart, a telephone jack, commonly affixed to a wall or baseboard. The standard for telephone plugs varies from country to country, though the RJ11 modular connector has become by far the most common.

A connection standard, such as RJ11, specifies not only the physical aspects of an electrical connector, but also the pinout, i.e. the assignment or function of each contact.[1] 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,[2] often improperly[3][4] referred to as RJ connectors.

History[edit]

Bell system line cord as used in the mid 1960s

Historically the telephone was typically owned by the telephone company and permanently wired to the telephone line they supplied, but as phone markets were deregulated a need arose for a simple plug-in interface that consumers could install. Many countries initially used different specifications for connectors. For example, after 1965 Bell System companies used the 505A plug, a round connector about 40 mm in diameter with four prongs about 15 mm apart. National connectors remain in service but few are used for new installations.

Connections[edit]

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; 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[edit]

Typical U.S. modular phone connector

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.

Compatibility[edit]

Different telephone connections are generally compatible with the use of an adapter: the physical connector and its wiring is the primary incompatibility.

See: gallery of telephone adapters.

List of plugs[edit]

Modular connectors[edit]

  • 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[edit]

International standards[edit]

National standards[edit]

  1. WT-4
  2. RJ11
  3. Cable holes

Traditionally, the 5th plastic pin disconnects 1 μF capacitor that shorts telephone line while plug is not inserted into socket. In modern makes it does nothing electrical, and capacitor compartment was reused for additional RJ11 socket.

Legacy[edit]

List of countries and territories, with the plugs they use[edit]

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 and the wide array of registered jacks.

Place Plug types
Albania RJ11
Algeria F-010
Argentina RJ11
Australia 610, RJ11
Austria TDO
Barbados RJ11
Belarus RJ11, Polish national 5-pin (WT-4[Note 1]
Belgium Tetrapolar plug, RJ11
Bolivia RJ11
Bosnia RJ11, 3-pin plug used in countries of former Yugoslavia [Note 1]
Botswana BS 6312
Brazil Telebrás plug, RJ11
Brunei RJ11
Bulgaria RJ11, Polish national 5-pin (WT-4[Note 1]
Canada RJ11
Cayman Islands RJ11
Chile RJ11
China Mainland RJ11
Colombia RJ11, 2-pin national standard[5]
Costa Rica RJ11
Croatia RJ11, 3-pin plug used in countries of former Yugoslavia [Note 1]
Cyprus BS 6312, RJ11[Note 2]
Czech Republic RJ11, 4-pin national plug [Note 1]
Denmark 3-prong national standard, RJ11 [Note 3]
Dominican Republic RJ11
Ecuador RJ11
Egypt RJ11[Note 4]
Estonia RJ11, Polish national 5-pin (WT-4[Note 1]
Faroe Islands RJ11
Finland RJ11, 3-prong national standard [Note 1]
France F-010, 8P8C [Note 5][Note 3] (since 2003)
Germany TAE, 8P8C [Note 5][Note 6]
Gibraltar BS 6312
Greece RJ11,[Note 7] Bipolar plug in older installations
Hong Kong RJ11[Note 3] BS 6312
Hungary RJ11
Iceland RJ11, SS 455 15 50 [Note 1]
India RJ11
Indonesia RJ11
Iran RJ11, CEI 23-16/VII[Note 1] CEE 7/16 [Note 1]
Ireland RJ11, 8P8C[Note 5][Note 8]
Israel BS 6312 but wired differently from the British Standard], RJ11
Italy Tripolar plug, RJ11, BTicino 2021
Japan RJ11
Korea, Republic of RJ11, RJ14,[Note 9] 4 prong connector (WE-like) [Note 10]
Latvia RJ11, Polish national 5-pin (WT-4[Note 1]
Lithuania RJ11, Polish national 5-pin (WT-4[Note 1]
Liechtenstein Reichle-connector, 4-pin Swiss telephone plugs [Note 1]
Luxembourg RJ11, 4-pin luxembourgish telephone plug [Note 1]
Macedonia RJ11, 3-pin plug used in countries of former Yugoslavia [Note 1]
Malaysia RJ11
Malta BS 6312, RJ11 [Note 3]
Mauritius F-010
Mexico RJ11
Montenegro RJ11, 3-pin plug used in countries of former Yugoslavia [Note 1]
Morocco F-010, RJ11
Netherlands RJ11, Dutch telephone plug
Nigeria RJ11
New Zealand BS 6312, RJ11,[Note 3] 8P8C [Note 5][Note 3]
Norway 8P8C[Note 5][Note 3][Note 11] 3-prong national standard[Note 1] 6-prong national standard[Note 12]
Pakistan RJ11
Panama RJ11
Peru RJ11
Philippines RJ11
Poland RJ11, Polish national 5-pin (WT-4) coupled with RJ11 socket [Note 1]
Portugal RJ11[Note 13]
Romania RJ11, 3-pin triangular plug similar to the Italian Tripolar plug,[Note 14] 5-pin R.S.-79.809[Note 15][Note 1]
Russia RJ11, Polish national 5-pin (WT-4[Note 1]
Serbia RJ11, 3-pin plug used in countries of former Yugoslavia [Note 1]
Singapore RJ11
Slovenia RJ11, 3-pin plug used in countries of former Yugoslavia [Note 1]
Slovakia RJ11, 4-pin national plug [Note 1]
South Africa RJ11, Protea, 8P8C [Note 5][Note 6]
Spain RJ11
Sri Lanka RJ11
Sweden SS 455 15 50, RJ11
Switzerland Reichle-connector, 4-pin plugs [Note 1]
Taiwan RJ11
Thailand RJ11
Trinidad and Tobago RJ11
Turkey RJ11, Tripolar plug in older installations
Ukraine RJ11, Polish national 5-pin (WT-4[Note 1]
United Arab Emirates BS 6312
United Kingdom BS 6312, RJ11[Note 16]
United States RJ11 and other Registered jacks, 4-pin Bell System plugs [Note 1]
Uruguay RJ11
Venezuela RJ11
Zimbabwe BS 6312, RJ11
  1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z Used in older installations
  2. ^ Used for ADSL
  3. ^ a b c d e f g Used in newer installations
  4. ^ Currently the dominant plug
  5. ^ a b c d e f Often, although incorrectly referred to as "RJ45"
  6. ^ a b Used for ISDN
  7. ^ Although other types can also be found
  8. ^ Used for ISDN, Digital PBX, and office systems
  9. ^ Official standard
  10. ^ The old standard deprecated officially after 2002 but still used generally.
  11. ^ Same plug used for POTS, ISDN and LAN
  12. ^ For local battery telephones, not used since approximately 1980
  13. ^ Also known as R.I.T.A.
  14. ^ Rarely used today
  15. ^ Same as the Polish WT-4
  16. ^ Used for ADSL modem lines in British telephone sockets

See also[edit]

References[edit]

  1. ^ Semenov, Andrey B.; Strizhakov, Stanislav K.; Suncheley, Igor R. (October 3, 2002). "Electrical Cable Connectors". Structured cable systems (1st ed.). Springer. p. 129. ISBN 3-540-43000-8. "The abbreviation for registered jack, RJ defines a particular wiring scheme of individual wires into outlet contacts. For example, a 6-position outlet may be wired to RJ-11C scheme (one pair), RJ-14C (two pairs), or RJ-25C (three pairs)." 
  2. ^ BICSI (October 7, 2002). "Background Information". Telecommunications Cabling Installation (2nd ed.). McGraw-Hill Professional. p. 88. ISBN 0-07-140979-3. "4-position and 4-contact connectors are used primarily for telephone handset cords." 
  3. ^ Trulove, James (December 19, 2005). "User Cords and Connectors". LAN wiring (3rd ed.). McGraw-Hill Professional. p. 219. ISBN 0-07-145975-8. "This 8-pin modular plug is probably the most subject to name abuse, because it resembles the specialized RJ-45 connector. However, the RJ-45 wiring pattern (which includes an interface programming resistor) is so radically different from that of T568A and B that it really should not be called by that name at all." 
  4. ^ Oliviero, Andrew; Woodward, Bill (July 20, 2009). "Connectors". Cabling: The Complete Guide to Copper and Fiber-Optic Networking (4th ed.). Sybex. p. 294. ISBN 0-470-47707-5. "The RJ (registered jack) prefix is one of the most widely (and incorrectly) used prefixes in the computer industry; nearly everyone, including people working for cabling companies, is guilty of referring to an eight-position modular jack (sometimes called an 8P8C) as an RJ-45." 
  5. ^ "Columbia/Venezuela phone plug". Archived from the original on April 13, 2008. 

External links[edit]