AC Power Plugs And Sockets
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AC power plugs and sockets connect electric equipment to the
alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...
(AC)
mains electricity Mains electricity or utility power, power grid, domestic power, and wall power, or in some parts of Canada as hydro, is a general-purpose alternating-current (AC) electric power supply. It is the form of electrical power that is delivered to h ...
power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...
in buildings and at other sites. Electrical plugs and sockets differ from one another in
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
and
current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...
rating, shape, size, and connector type. Different standard systems of plugs and sockets are used around the world. Plugs and sockets for portable appliances became available in the 1880s, to replace connections to light sockets with wall-mounted outlets. A proliferation of types developed for both convenience and protection from
electrical injury Electrical injury is a physiological reaction caused by electric current passing through the body. The injury depends on the density of the current, tissue resistance and duration of contact. Very small currents may be imperceptible or produce a ...
. Today there are about 20 types in common use around the world, and many obsolete socket types are found in older buildings. Coordination of technical standards has allowed some types of plug to be used across large regions to facilitate trade in electrical appliances, and for the convenience of travellers and consumers of imported electrical goods. Some multi-standard sockets allow use of several types of plug; improvised or unapproved adaptors between incompatible sockets and plugs may not provide the full safety and performance of an approved socket-plug combination.


Concepts and terminology

A plug is the movable connector attached to an electrically operated device, and the socket is fixed on equipment or a building structure and connected to an energised electrical circuit. The plug is a ''male'' connector, often with protruding pins that match the openings and ''female'' contacts in a socket. Some plugs have female contacts that are used only for an earth ground connection. Some plugs have built-in
fuses Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protec ...
for safety. To reduce the risk of
electric shock Electrical injury is a physiological reaction caused by electric current passing through the body. The injury depends on the density of the current, tissue resistance and duration of contact. Very small currents may be imperceptible or produce ...
, plug and socket systems have safety features in addition to the recessed contacts of the energised socket. A socket may be surrounded by a decorative or protective cover which may be integral with the socket.
Single-phase In electrical engineering, single-phase electric power (abbreviated 1φ) is the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when load ...
sockets have two current-carrying connections to the power supply circuit, and may also have a third pin for a safety connection to earth ground. Depending on the supply system, one or both current-carrying connections may have significant voltage to earth ground.


History

When commercial electric power was first introduced in the 1880s, it was used primarily for lighting. Other portable appliances (such as vacuum cleaners, electric fans, smoothing irons, and curling-tong heaters) were connected to light-bulb sockets. As early as 1885 a two-pin plug and wall socket format was available on the British market. By about 1910 the first three-pin earthed (grounded) plugs appeared. Over time other safety improvements were gradually introduced to the market. The earliest national standard for plug and wall socket forms was set in 1915.


Application issues


Protection from accidental contact

Designs of plugs and sockets have gradually developed to reduce the risk of electric shock and fire. Plugs are shaped to prevent finger contact with live parts. Sockets may be recessed and plugs designed to fit closely within the recess to reduce risk of a user's fingers contacting the live pins. Contact pins may be sheathed with insulation over part of their length, so as to reduce exposure of energized metal during insertion or removal of the socket. Sockets may have automatic shutters to stop foreign objects from being inserted into energized contacts. Some types can also include
fuses Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protec ...
and switches.


Earthing (grounding)

A third contact for a connection to
earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
is intended to protect against insulation failure of the connected device. Some early unearthed plug and socket types were revised to include an earthing pin or phased out in favour of earthed types. The plug is often designed so that the earth ground contact connects before the energized circuit contacts. The assigned IEC
appliance class Appliance classes (also known as protection classes) specify measures to prevent dangerous contact voltages on unenergized parts, such as the metallic casing, of an electronic device. In the electrical appliance manufacturing industry, the followi ...
is governed by the requirement for earthing or equivalent protection. Class I equipment requires an earth contact in the plug and socket, while Class II equipment is unearthed and protects the user with
double insulation Appliance classes (also known as protection classes) specify measures to prevent dangerous contact voltages on unenergized parts, such as the metallic casing, of an electronic device. In the electrical appliance manufacturing industry, the followi ...
.


Polarisation

Where a "neutral" conductor exists in supply wiring, polarisation of the plug can improve safety by preserving the distinction in the equipment. For example, appliances may ensure that switches interrupt the line side of the circuit, or can connect the shell of a screw-base lampholder to neutral to reduce electric shock hazard. In some designs, polarised plugs cannot be mated with non-polarised sockets. Wiring systems where both circuit conductors have a significant potential with respect to earth do not benefit from polarised plugs.


Universal sockets

"Universal" or "multi-standard" sockets are intended to accommodate plugs of various types. In some jurisdictions, they violate safety standards for sockets. Safety advocates, the United States Army, and a manufacturer of sockets point out a number of safety issues with universal socket and adapters, including voltage mismatch, exposure of live pins, lack of proper earth ground connection, or lack of protection from overload or short circuit. Universal sockets may not meet technical standards for durability, plug retention force, temperature rise of components, or other performance requirements, as they are outside the scope of national and international technical standards. A technical standard may include compatibility of a socket with more than one form of plug. The Thai dual socket is specified in figure 4 of TIS 166-2549 and is designed to accept Thai plugs, and also Type A, B, and C plugs. Chinese dual sockets have both an unearthed socket complying with figure 5 of GB 1002-2008 (both flat pin and 4.8 mm round pin), and an earthed socket complying with figure 4 of GB 1002-2008. Both Thai and Chinese dual sockets also physically accept plugs normally fitted to 120 V appliances (e.g. 120 V rated NEMA 1-15 ungrounded plugs). This can cause an electrical incompatibility, since both states normally supply residential power only at 220 V. File:Multi plug.jpg, A so-called "universal socket", which meets no official standard but is intended to accept a number of different plug types. File:Thai socket.jpg, An earthed Thai socket that appears to comply with figure 4 of TIS 166-2549. Although it may accept NEMA plugs, the Thai voltage is 220 V and thus is electrically incompatible with devices designed only for 110 V. File:Chinasocket.jpg, Chinese dual socket accepting both unearthed 2-pin (upper) and earthed 3-pin (lower) plugs.


Voltage rating of plugs and power cords

Plugs and
power cord A power cord, line cord, or mains cable is an electrical cable that temporarily connects an appliance to the mains electricity supply via a wall socket or extension cord. The terms are generally used for cables using a power plug to connect ...
s have a rated voltage and current assigned to them by the manufacturer. Using a plug or power cord that is inappropriate for the load may be a safety hazard. For example, high-current equipment can cause a fire when plugged into an extension cord with a current rating lower than necessary. Sometimes the cords used to plug in dual voltage 120 V / 240 V equipment are rated only for 125 V, so care must be taken by travellers to use only cords with an appropriate voltage rating.


Appliance connections and extensions

So that manufacturers need not build many similar appliances differing only in the type of plug fitted, a common strategy is to provide an
IEC 60320 IEC 60320 Appliance couplers for household and similar general purposes is a set of standards from the International Electrotechnical Commission (IEC) specifying non-locking connectors for connecting power supply cords to electrical appliances ...
inlet on the appliance and a detachable
power cord A power cord, line cord, or mains cable is an electrical cable that temporarily connects an appliance to the mains electricity supply via a wall socket or extension cord. The terms are generally used for cables using a power plug to connect ...
(mains flex lead) and appropriate plug. The appliance need only to be tested to the power inlet. Some appliances have a switch for selection of voltage.
Extension cord An extension cord (US), power extender, drop cord, or extension lead (UK) is a length of flexible electrical power cable (flex) with a AC power plugs and sockets, plug on one end and one or more sockets on the other end (usually of the same type ...
s (extension leads) are used for temporary connections when a socket is not within convenient reach of an appliance's power lead. A
power strip A power strip is a block of electrical sockets that attaches to the end of a flexible cable (typically with a mains plug on the other end), allowing multiple electrical devices to be powered from a single electrical socket. Power strips are often ...
with multiple sockets may also have a switch, surge voltage protection, or over-current protection.


Special purpose plugs and sockets

Special purpose sockets may be found in residential, industrial, commercial or institutional buildings. Examples of systems using special purpose sockets include: * "Clean" (low electrical noise) earth for use with computer systems, * Emergency power supply, *
Uninterruptible power supply An uninterruptible power supply or uninterruptible power source (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. A UPS differs from an auxiliary or emergency power system ...
for critical or life-support equipment, * Isolated power for medical instruments, tools used in wet conditions, or electric razors, * "Balanced" or "technical" power used in audio and video production studios, *
Theatrical lighting Stage lighting is the craft of lighting as it applies to the production of theater, dance, opera, and other performance arts.
, *
IEC 60309 IEC 60309 (formerly IEC 309 and CEE 17, also published by CENELEC as EN 60309) is a series of international standards from the International Electrotechnical Commission (IEC) for "plugs, socket-outlets and couplers for industrial purp ...
(CEE 17) "plugs, socket-outlets and couplers for industrial purposes", used as a weather-resistant connector for Caravans,
Motorhome A motorhome (or motor coach) is a type of self-propelled recreational vehicle (RV) which offers mobile living accommodation. Features Motorhomes usually have sleeping spaces for two to eight people. Each sleeping space is either fixed or conv ...
s,
camper van A camper van, also referred to as a camper, caravanette, motor caravan or RV (recreational vehicle) in North America, is a self-propelled vehicle that provides both transport and sleeping accommodation. The term describes vans that have been fitt ...
s and
tent A tent () is a shelter consisting of sheets of fabric or other material draped over, attached to a frame of poles or a supporting rope. While smaller tents may be free-standing or attached to the ground, large tents are usually anchored using gu ...
s for mains hook-up at camp-sites. * Sockets for electric clothes dryers, electric ovens, and air conditioners with higher current rating. Special-purpose sockets may be labelled or coloured to identify a reserved use of a system, or may have keys or specially shaped pins to prevent use of unintended equipment.


Shaver supply units

National wiring regulations sometimes prohibit the use of sockets adjacent to water taps, etc. A special socket, with an
isolation transformer An isolation transformer is a transformer used to transfer electrical power from a source of alternating current (AC) power to some equipment or device while isolating the powered device from the power source, usually for safety reasons or to re ...
, may allow electric razors to be used near a sink. Because the isolation transformer is of low rating, such outlets are not suitable to operate higher-powered appliances such as
hair dryer A hair dryer, hairdryer or blow dryer is an electromechanical device that blows ambient or hot air over damp hair to speed the evaporation of water to dry the hair. Blow dryers enable better control over the shape and style of hair, by accelerat ...
s. An IEC standard 61558-2-5, adopted by
CENELEC CENELEC (french: Comité Européen de Normalisation Électrotechnique; en, European Committee for Electrotechnical Standardization) is responsible for European standardization in the area of electrical engineering. Together with ETSI (telecommun ...
and as a national standard in some countries, describes one type of shaver supply unit. Shaver sockets may accept multiple two-pin plug types including Europlug (Type C), Australian (Type I) and BS 4573. The isolation transformer often includes a 115 V output accepting two-pin US plugs (Type A). Shaver supply units must also be current limited, IEC 61558-2-5 specifies a minimum rating of 20  VA and maximum of 50 VA. Sockets are marked with a shaver symbol, and may also say "shavers only." Isolation transformers and dedicated NEMA 1-15 shaver receptacles were once standard installation practice in North America, but now a
GFCI A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) is an electrical safety device that quickly breaks an electrical circuit with leakage current to ground. It is to protect equip ...
receptacle is used instead. This provides the full capacity of a standard receptacle but protects the user of a razor or other appliance from leakage current.


Types in present use

The plugs and sockets used in a given area are regulated by local governments. The
International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
(IEC) maintains a guide with letter designations for generally compatible types of plugs,World Plugs
Retrieved on 27 March 2015.
which expands on earlier guides published by the
United States Department of Commerce The United States Department of Commerce is an executive department of the U.S. federal government concerned with creating the conditions for economic growth and opportunity. Among its tasks are gathering economic and demographic data for bu ...
. This is a ''de facto'' naming standard and guide to travellers. Some letter types correspond to several current ratings or different technical standards, so the letter does not uniquely identify a plug and socket within the type family, nor guarantee compatibility. Physical compatibility of the plug and socket does not ensure correct voltage, frequency, or current capacity. Not all plug and socket families have letters in the IEC guide, but those that have are noted in this article, as are some additional letters commonly used by retail vendors.The letter system first appeared in such guides in 1967
''Electric Current Abroad''.
United States Department of Commerce The United States Department of Commerce is an executive department of the U.S. federal government concerned with creating the conditions for economic growth and opportunity. Among its tasks are gathering economic and demographic data for bu ...
, 1967. Retrieved on 14 December 2013.) which designated types A 2-pin US, B (BS 546), and C (BS 1363). The 1984 edition
''Electric Current Abroad''.
United States Department of Commerce The United States Department of Commerce is an executive department of the U.S. federal government concerned with creating the conditions for economic growth and opportunity. Among its tasks are gathering economic and demographic data for bu ...
, 1984. Retrieved on 14 December 2013.) uses the letters A to G in the same manner as they are used today, and the last revision of the print series was in 1998 (). The
International Trade Administration : The International Trade Administration (ITA) is an agency in the United States Department of Commerce that promotes United States exports of nonagricultural U.S. services and goods. Duties The ITA's stated goals are to # Provide practical inf ...
of the US Department of Commerce now publishes a web version
Electric Current Worldwide
which differs slightly from the IEC list and from Wikipedia's list at
Mains electricity by country Mains electricity by country includes a list of countries and territories, with the plugs, voltages and frequencies they commonly use for providing electrical power to low voltage appliances, equipment, and lighting typically found in homes an ...
.
In Europe,
CENELEC CENELEC (french: Comité Européen de Normalisation Électrotechnique; en, European Committee for Electrotechnical Standardization) is responsible for European standardization in the area of electrical engineering. Together with ETSI (telecommun ...
publishes a list of approved plug and socket technical standards used in the member countries.


Argentina IRAM 2073 and 2071 (Type I)

The plug and socket system used in Class 1 applications in Argentina is defined by IRAM standards. These two standards are; IRAM 2073 "Two pole plugs with earthing contact for domestic and similar purposes, rated 10 A and 20 A, 250 V AC" and IRAM 2071 "Two pole socket – outlets with earthing contact for 10 A and 20 A, 250 V AC., for fixed installations." The plug and socket system is similar in appearance to the Australian and Chinese plugs. It has an earthing pin and two flat current-carrying pins forming an inverted V-shape (120°). The flat pins for the 10 A version measure and for the 20 A version, and are set at 30° to the vertical at a nominal pitch of . The pin length is the same as in the Chinese version. The earthing pin length is for the 10 A version and for the 20 A version. On the plugs, the pole length is for the 10 A version and for the 20 A version. The most important difference from the Australian plug is that the Argentinian plug is wired with the live and neutral contacts reversed. In Brazil, similar plugs and sockets are still commonly used in old installations for high-power appliances like air conditioners, dishwashers, and household ovens. Although being often called "Argentinian plug," it is actually based on the American NEMA 10-20 standard, and is incompatible with Argentinian IRAM plugs. Since Brazil adopted the NBR 14136 standard which includes a 20 A version, the original motivation to use the NEMA 10-20 plug has ceased to exist.


Australian/New Zealand standard AS/NZS 3112 (Type I), used in Australasia

This Australian/New Zealand standard is used in Australia, New Zealand, Fiji, Tonga, Solomon Islands, and Papua New Guinea. It defines a plug with an earthing pin, and two flat current-carrying pins which form an inverted V-shape. The flat pins measure and are set at 30° to the vertical at a nominal pitch of . Australian and New Zealand wall sockets (locally often referred to as ''power points'') almost always have switches on them for extra safety, as in the UK. An unearthed version of this plug with two angled power pins but no earthing pin is used with double-insulated appliances, but the sockets always include an earth contact. There are several AS/NZS 3112 plug variants, including ones with larger or differently shaped pins used for devices drawing 15, 20, 25 and 32 A. These sockets accept plugs of equal or lower current rating, but not higher. For example, a 10 A plug will fit all sockets but a 20 A plug will fit only 20, 25 and 32 A sockets. In New Zealand, PDL 940 "tap-on" or "piggy-back" plugs are available which allow a second 10 A plug to be fitted to the rear of the plug. In Australia these piggy-back plugs are now available only on pre-made extension leads. Australia's standard plug/socket system was originally codified as standard C112 (floated provisionally in 1937, and adopted as a formal standard in 1938), which was based on a design patented by
Harvey Hubbell Harvey Hubbell II (December 20, 1857 – December 17, 1927), was an American inventor, entrepreneur, and industrialist. His best-known inventions are the U.S. electrical plug and the pull-chain light socket. In 1888, at the age of thirty- ...
and was superseded by AS 3112 in 1990. The requirement for insulated pins was introduced in the 2004 revision. The current version is ''AS/NZS 3112:2011, Approval and test specification – Plugs and socket-outlets''.


Brazilian standard NBR 14136 (Type N)

Brazil, which had been using mostly Europlugs, and NEMA 1-15 and NEMA 5-15 standards, adopted a (non-compliant) variant of
IEC 60906-1 IEC 60906-1 is an international standard designed ''"to provide a standard for a safe, compact and practical 16  A 250  V  AC system of plugs and socket-outlets that could be accepted by many countries as their national standard, ...
as the national standard in 1998 under specification NBR 14136 (revised in 2002). These are used for both 220-volt and 127-volt regions of the country, despite the IEC 60906-2 recommendation that NEMA 5-15 be used for 120 V connections. There are two types of sockets and plugs in NBR 14136: one for 10 A, with a 4.0 mm pin diameter, and another for 20 A, with a 4.8 mm pin diameter. This differs from IEC 60906-1 which specifies a pin diameter of 4.5 mm and a rating of 16 A. NBR 14136 does not require shutters on the apertures, a further aspect of non-compliance with IEC 60906-1. NBR 14136 was not enforced in that country until 2007, when its adoption was made optional for manufacturers. It became compulsory on 1 January 2010. Few private houses in Brazil have an earthed supply, so even if a three-pin socket is present it is not safe to assume that all three terminals are actually connected. Most large domestic appliances were sold with the option to fit a flying earth tail to be locally earthed, but many consumers were unsure how to use this and so didn't connect it. The new standard has an earth pin, which in theory eliminates the need for the flying earth tail.


British and compatible standards


BS 546 and related types (Type D and M)

BS 546, "Two-pole and earthing-pin plugs, socket-outlets and socket-outlet adaptors for AC (50-60 Hz) circuits up to 250V" describes four sizes of plug rated at 2 A, 5 A (Type D), 15 A (Type M) and 30 A. The plugs have three round pins arranged in a triangle, with the larger top pin being the earthing pin. The plugs are polarised and unfused. Plugs are non-interchangeable between current ratings. Introduced in 1934, the BS 546 type has mostly been displaced in the UK by the BS 1363 standard. According to the IEC, some 40 countries use Type D and 15 countries use Type M. Some, such as India and South Africa, use standards based on BS 546.


BS 1363 (Type G)

BS 1363 "13 A plugs, socket-outlets, adaptors and connection units" is the main plug and socket type used in the United Kingdom. According to the
IEC The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and r ...
it is also used in over 50 countries worldwide. Some of these countries have national standards based on BS 1363, including:
Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...
,
Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...
,
Malta Malta ( , , ), officially the Republic of Malta ( mt, Repubblika ta' Malta ), is an island country in the Mediterranean Sea. It consists of an archipelago, between Italy and Libya, and is often considered a part of Southern Europe. It lies ...
,
Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, borde ...
,
Bahrain Bahrain ( ; ; ar, البحرين, al-Bahrayn, locally ), officially the Kingdom of Bahrain, ' is an island country in Western Asia. It is situated on the Persian Gulf, and comprises a small archipelago made up of 50 natural islands and an ...
,
Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...
and
Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the fifth-largest country in Asia, the second-largest in the A ...
. This plug has three rectangular pins forming an isosceles triangle. The BS 1363 plug has a
fuse Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protect ...
rated to protect its flexible cord from overload and consequent fire risk. Modern appliances may only be sold with a fuse of the appropriate size pre-installed.


BS 4573 (UK shaver)

The United Kingdom, Ireland, and Malta, use the BS 4573 two-pin plug and socket for electric shavers and toothbrushes. The plug has insulated sleeves on the pins. Although similar to the
Europlug The Europlug is a flat, two-pole, round-pin domestic AC power plug, rated for voltages up to 250 V and currents up to 2.5 A.IECEE The IECEE is the IEC System of Conformity Assessment Schemes for Electrotechnical Equipment and Components being a body of the International Electrotechnical Commission (IEC). The IEC uses the name IECEE for the IEC ''System for Conformity Testing a ...
) was a standards body which published ''Specification for plugs and socket-outlets for domestic and similar purposes'' as CEE Publication 7 in 1951. It was last updated by Modification 4 in March 1983. CEE 7 consists of general specifications and standard sheets for specific connectors. Standard plugs and sockets based on two round pins with centres spaced at 19 mm are in use in Europe, most of which are listed in IEC/TR 60083 "Plugs and socket-outlets for domestic and similar general use standardized in member countries of IEC." EU countries each have their own regulations and national standards; for example, some require child-resistant shutters, while others do not.
CE marking On commercial products, the letters CE (as the logo ) mean that the manufacturer or importer affirms the good's conformity with European health, safety, and environmental protection standards. It is not a quality indicator or a certificatio ...
is neither applicable nor permitted on plugs and sockets.


CEE 7/1 unearthed socket and CEE 7/2 unearthed plug

CEE 7/1 unearthed sockets accept CEE 7/2 round plugs with pins. Because they have no earth connections they have been or are being phased out in most countries. Some countries still permit their use in dry areas. Older sockets are so shallow that it is possible to accidentally touch the live pins of a plug. CEE 7/1 sockets also accept CEE 7/4, CEE 7/6 and CEE 7/7 plugs without providing an earth connection. The earthed CEE 7/3 and CEE 7/5 sockets do not allow insertion of CEE 7/2 unearthed round plugs.


CEE 7/3 socket and CEE 7/4 plug (German "Schuko"; Type F)

The CEE 7/3 socket and CEE 7/4 plug are commonly called ''
Schuko "Schuko" () is a registered trademark referring to a system of AC power plugs and sockets that is defined as " CEE 7/3" (sockets) and "CEE 7/4" (plugs). A Schuko plug features two round pins of 4.8 mm diameter (19 mm long, centers 19&n ...
'', an abbreviation for ''Schutzkontakt'', ''Protective contact'' to earth ("Schuko" itself is a registered
trademark A trademark (also written trade mark or trade-mark) is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies products or services from a particular source and distinguishes them from others ...
of a German association established to own the term). The socket has a circular recess with two round holes and two earthing clips that engage before live pin contact is made. The pins are . The Schuko system is unpolarised, allowing live and neutral to be reversed. The socket accepts Europlugs and CEE 7/17 plugs. It is rated at 16 A. The current German standards are DIN 49441 and DIN 49440. The standard is used in Germany and several other European countries and on other continents. Some countries require child-proof socket shutters; the DIN 49440 standard does not have this requirement. The plug is used in most countries of Europe, Asia, and Africa, as well as in the countries of Peru, Chile and Uruguay. The few European countries not using it (or not using it predominantly) are Denmark, Switzerland, UK, Italy and Ireland.


CEE 7/5 socket and CEE 7/6 plug (French; Type E)

French standard NF C 61-314 defines the CEE 7/5 socket and CEE 7/6 plug, (and also includes CEE 7/7, 7/16 and 7/17 plugs). The socket has a circular recess with two round holes. The round earth pin projecting from the socket connects before the energized contacts touch. The earth pin is centred between the apertures, offset by . The plug has two round pins measuring , spaced apart and with an aperture for the socket's projecting earth pin. This standard is also used in Belgium, Poland, the Czech Republic, Slovakia and some other countries. Although the plug is polarised, CEE 7 does not define the placement of the live and neutral and there is no universally observed standard. CEE 7/2 and 7/4 plugs are not compatible with the CEE 7/5 socket because of the round earthing pin permanently mounted in the socket.


CEE 7/7 plug (compatible with E and F)

The CEE 7/7 plug fits in either French or Schuko sockets. The CEE 7/7 plug has earthing contacts to connect to either the CEE 7/3 socket or the CEE 7/5 socket. It is polarised when used with a French CEE 7/5 socket, but can be inserted two ways into a CEE 7/3 socket. The plug is rated at 16 A. Appliances are sold with non-rewireable CEE 7/7 plugs attached. This plug can be inserted into a Danish Type K socket, but the earth contact will not connect.


CEE 7/16 plugs

The CEE 7/16 unearthed plug is used for unearthed appliances. It has two round 4 by 19 mm (0.157 by 0.748 in) pins, rated at 2.5 A. There are two variants.


=CEE 7/16 Alternative I

= Alternative I is a round plug with cutouts to make it compatible with CEE 7/3 and CEE 7/5 sockets. (The similar-appearing CEE 7/17 has larger pins and a higher current rating.) This alternative is seldom used.


=CEE 7/16 Alternative II "Europlug" (Type C)

= Alternative II, popularly known as the
Europlug The Europlug is a flat, two-pole, round-pin domestic AC power plug, rated for voltages up to 250 V and currents up to 2.5 A.

CEE 7/17 unearthed plug

This is a round plug compatible with CEE 7/1, CEE 7/3, and CEE 7/5 sockets. It has two round pins measuring . The pins are not sheathed, in contrast to e.g. CEE 7/16 europlugs. It may be rated at either 10 A or 16 A. A typical use is for appliances that exceed the 2.5 A rating of CEE 7/16 europlugs. It may be used for unearthed Class II appliances (and in South Korea for all domestic non-earthed appliances). It is also defined as the Class II plug in Italian standard CEI 23-50. It is sometimes called a contour plug, because its collar contour follows that of the socket's recess. The collar prevents accidental contact with the non sheathed pins when inserting or removing the plug in a recessed socket. It can be inserted into Israeli SI 32 with some difficulty. The Soviet
GOST 7396 GOST 7396 (''ГОСТ 7396'' in Cyrillic) is a series of Soviet and later Russian standards that specify basic dimensions and safety requirements for power plugs and sockets used in Russia and other Post-Soviet states, former Soviet Republics, as we ...
standard includes both the CEE 7/17 and the CEE 7/16 variant II plug.


China GB 2099.1‐2008 and GB 1002‐2008 (Type A & I)

The standard for Chinese plugs and sockets (excluding Hong Kong and Macau) is set out in GB 2099.1‐2008 and GB 1002‐2008. As part of China's commitment for entry into the
WTO The World Trade Organization (WTO) is an intergovernmental organization that regulates and facilitates international trade. With effective cooperation in the United Nations System, governments use the organization to establish, revise, and e ...
, the new CPCS (Compulsory Product Certification System) has been introduced, and compliant Chinese plugs have been awarded the
CCC Mark The China Compulsory Certificate mark, commonly known as a CCC Mark, is a compulsory safety mark for many products imported, sold or used in the Chinese market. It was implemented on May 1, 2002 and became fully effective on August 1, 2003. It is ...
by this system. The plug is three wire, earthed, rated at 10 A, 250 V and used for Class 1 applications; a slightly larger 16 A version also exists. The nominal pin dimensions of the 10 A version are: 1.5 mm thick by 6.4 mm wide, the line & neutral are 18 mm long, and the earth is 21 mm long. It is similar to the Australian plug. Many 3 pin sockets in China include a physical lockout preventing access to the active and neutral terminals unless an earth pin (which is slightly longer than the other 2 pins) is entered first. China also uses American/Japanese NEMA 1‐15 sockets and plugs for Class-II appliances; a common socket type that also accepts Europlug (type C) is also defined in GB 1002. The voltage at a Chinese socket of any type is 220 V. Type I plugs and sockets from different countries have different pin lengths. This means that the uninsulated pins of a Chinese plug may become live while there is still a large enough gap between the faces of the plug and socket to allow a finger to touch the pin.


Danish Section 107-2-D1 earthed (Type K)

This
Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish a ...
standard plug is described in the Danish Plug Equipment Section 107-2-D1 Standard sheet (SRAF1962/DB 16/87 DN10A-R). The Danish standard provides for sockets to have child-resistant shutters. The Danish socket will also accept the CEE 7/16 Europlug or CEE 7/17 Schuko-French hybrid plug. CEE 7/4 (Schuko), CEE 7/7 (Schuko-French hybrid), and earthed CEE 7/6 French plugs will also fit into the socket but will not provide an earth connection and may be attached to appliances requiring more than the 13 A maximum rating of the socket. A variation (standard DK 2-5a) of the Danish plug is for use only on surge protected computer sockets. It fits into the corresponding computer socket and the normal socket, but normal plugs deliberately don't fit into the special computer socket. The plug is often used in companies, but rarely in private homes. There is a variation for hospital equipment with a rectangular left pin, which is used for life support equipment. Traditionally all Danish sockets were equipped with a switch to prevent touching live pins when connecting/disconnecting the plug. Today, sockets without switch are allowed, but then it is a requirement that the sockets have a cavity to prevent touching the live pins. The shape of the plugs generally makes it difficult to touch the pins when connecting/disconnecting. Since the early 1990s earthed sockets have been required in all new electric installations in Denmark. Older sockets need not be earthed, but all sockets, including old installations, must be protected by earth-fault interrupters (HFI or HPFI in Danish) by 1 July 2008. As of 1 July 2008, wall sockets for French 2-pin, female earth CEE 7/5 are permitted for installations in Denmark. This was done because little electrical equipment sold to private users is equipped with a Danish plug. CEE 7/3 sockets were not permitted until 15 November 2011. Many international travel adaptor sets sold outside Denmark match CEE 7/16 (Europlug) and CEE 7/7 (Schuko-French hybrid) plugs which can readily be used in Denmark.


IEC 60906-1 (Type N)

In 1986, the International Electrotechnical Commission published IEC 60906-1, a specification for a plug and socket that look similar, but are not identical, to the Swiss plug and socket. This standard was intended to one day become common for all of Europe and other regions with 230 V mains, but the effort to adopt it as a European Union standard was put on hold in the mid-1990s. The plug and socket are rated 16 A 250 V AC and are intended for use only on systems having nominal voltages between 200 V and 250 V AC The plug pins are 4.5 mm in diameter, line and neutral are on centres 19 mm apart. The earth pin is offset 3.0 mm. The line pin is on the left when looking at a socket with the earth pin offset down. Shutters over the line and neutral pins are mandatory. The only country to have officially adopted the standard is South Africa as SANS 164-2. Brazil developed a plug resembling IEC 60906-1 as the national standard under specification NBR 14136. The NBR 14136 standard has two versions, neither of which has pin dimensions or ratings complying with IEC 60906-1. Use at 125 V is permitted by NBR 14136, which is against the intention of IEC 60906-1.


Israel SI32 (Type H)

The plug defined in
SI 32 The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...
( IS16A-R) is used only in Israel and in the territories of the
West Bank The West Bank ( ar, الضفة الغربية, translit=aḍ-Ḍiffah al-Ġarbiyyah; he, הגדה המערבית, translit=HaGadah HaMaʽaravit, also referred to by some Israelis as ) is a landlocked territory near the coast of the Mediter ...
and the
Gaza Strip The Gaza Strip (;The New Oxford Dictionary of English (1998) – p.761 "Gaza Strip /'gɑːzə/ a strip of territory under the control of the Palestinian National Authority and Hamas, on the SE Mediterranean coast including the town of Gaza.. ...
. There are two versions: an older one with flat pins, and a newer one with round pins. The pre-1989 system has three flat pins in a Y-shape, with line and neutral apart. The plug is rated at 16 A. In 1989 the standard was revised, with three round pins in the same locations designed to allow the socket to accept both older and newer Israeli plugs, and also non-earthed Europlugs (often used in Israel for equipment which does not need to be earthed and does not use more current than the Europlug is rated for). Pre-1989 sockets which accept only old-style plugs have become very rare in Israel. SI 32 plugs have no sleeve insulation, so when a plug is partially removed its prongs may still be powered although they can be touched by small fingers, metal objects, etc., with a risk of electric shock. Sockets have a defined polarity; looking at the front, neutral is to the left, earth at the bottom, and line to the right.


Italy (Type L)

Italian plugs and sockets are defined by the standard CEI 23-50 which superseded CEI 23-16. This includes models rated at 10 A and 16 A that differ in contact diameter and spacing (see below for details). Both are symmetrical, allowing the line and neutral contacts to be inserted in either direction. This plug is also commonly used in Chile and Uruguay. # 10 A plugs and socket: Pins which are 4 mm in diameter, the centres spaced 19 mm apart. The 10 A three-pin earthed rear entry plug is designated CEI 23-50 S 11 (there are also two side-entry versions, SPA 11 and SPB 11). The 10 A two-pin unearthed plug is designated CEI 23-50 S 10. The 10 A three-pin earthed socket is designated CEI 23-50 P 11, and the 10 A two-pin unearthed socket is designated CEI 23-50 P 10. Both 10 A sockets also accept CEE 7/16 (Europlugs). # 16 A plug and socket: Pins which are 5 mm in diameter, the centres spaced 26 mm apart. The 16 A three-pin earthed rear entry plug is designated CEI 23-50 S 17 (there are also two side-entry versions, SPA 17 and SPB 17). The 16 A two-pin unearthed plug is designated CEI 23-50 S 16. The 16 A three-pin earthed socket is designated CEI 23-50 P 17, there is not a 16 A two-pin unearthed socket. The 16 A socket used to be referred to as ''per la forza motrice'' (for electromotive force, see above) or sometimes (inappropriately) ''industriale'' (industrial) or even ''calore'' (heat). The two standards were initially adopted because up to the second half of the 20th century in many regions of Italy electricity was supplied by means of two separate consumer connections – one for powering illumination and one for other purposes – and these generally operated at different voltages, typically 127 V single phase and 220 V single phase (from 3-phase 380 V) or two phase (from 220 V 3-phase). The electricity on the two supplies was separately metered, was sold at different tariffs, was taxed differently and was supplied through separate and different sockets. Even though the two electric lines (and respective tariffs) were gradually unified beginning in the 1960s (the official, but purely theoretical date was the summer of 1974) many houses had dual wiring and two electricity meters for years thereafter; in some zones of Lazio the 127 V network was provided for lighting until 1999. The two gauges for plugs and sockets thus became a
de facto standard A ''de facto'' standard is a custom or convention that has achieved a dominant position by public acceptance or market forces (for example, by early entrance to the market). is a Latin phrase (literally " in fact"), here meaning "in practice b ...
which is now formalized under CEI 23-50. Some older installations have sockets that are limited to either the 10 A or the 16 A style plug, requiring the use of an adaptor if the other gauge needs to be connected. Numerous cross adaptors were used. Almost every appliance sold in Italy nowadays is equipped with CEE 7/7 (German/French), CEE 7/16 or CEE 7/17 plugs, but the standard Italian sockets will not accept the first and the third ones since the pins of the CEE 7/7 and CEE 7/17 plugs are thicker (4.8 mm) than the Italian ones (4 mm); besides the pins are not sheathed and forcing them into a linear Italian socket may lead to electric shock. Adaptors are standardized in Italy under CEI 23-57 which can be used to connect CEE 7/7 and CEE 7/17 and plugs to linear CEI 23-50 sockets. Europlugs are also in common use in Italy; they are standardized under CEI 23-34 S 1 for use with the 10 A socket and can be found fitted to Class II appliances with low current requirement (less than 2.5 A). The current Italian standards provide for sockets to have child-resistant shutters ("Sicury" patent).


Italian multiple standard sockets

In modern installations in Italy (and in other countries where Type L plugs are used) it is usual to find sockets that can accept more than one standard. The simplest type, designated CEI 23-50 P 17/11, has a central round hole flanked by two figure-8 shaped holes, allowing the insertion of CEI 23-50 S 10 (Italian 10 A plug unearthed), CEI 23-50 S 11 (Italian 10 A plug earthed), CEI 23-50 S 16 (Italian 16 A plug unearthed), CEI 23-50 S 17 (Italian 16 A plug earthed) and CEE 7/16 (Europlug). The advantage of this socket style is its small, compact face; its drawback is that it accepts neither CEE 7/7 nor CEE 7/17, very commonly found in new appliances sold in Italy. Vimar brand claims to have patented this socket first in 1975 with their ''Bpresa'' model; however soon other brands started selling similar products, mostly naming them with the generic term ''presa bipasso'' (twin-gauge socket) that is now of common use. A second, quite common type is called CEI 23-50 P 30 and looks like a Schuko socket, but adds a central earthing hole (optional according to CEI 23-50, but virtually always present). This design can accept CEE 7/4 (German), CEE 7/7 (German/French), CEE 7/16, CEE 7/17 (''Konturenstecker'', German/French unearthed), CEI 23-50 S 10 and CEI 23-50 S 11 plugs. Its drawback is that it is twice as large as a normal Italian socket, it does not accept 16 A Italian plugs and the price is higher; for those reasons Schuko sockets have been rarely installed in Italy until recent times. Other types may push compatibility even further. The CEI 23-50 P 40 socket, which is quickly becoming the standard in Italy along with CEI 23-50 P 17/11, accepts CEE 7/4, CEE 7/7, CEE 7/16, CEE 7/17, CEI 23-50 S 10, CEI 23-50 S 11, CEI 23-50 S 16 and CEI 23-50 S 17 plugs; its drawback is that it does not accept SPA 11, SPB 11, SPA 17 and SPB 17 side-entry plugs; however almost no appliance is sold with these types, which are mainly used to replace existing plugs. The Vimar-brand ''universale'' (all purpose) socket accepts CEE 7/4, CEE 7/7, CEE 7/16, CEE 7/17, CEI 23-50 S 10, CEI 23-50 S 11, CEI 23-50 S 16, CEI 23-50 S 17 and also NEMA 1-15 (US/Japan) plugs (older versions also had extra holes to accept UK shaver plugs).


North America, Central America and IEC 60906-2

Most of North America and Central America, and some of South America, use connectors standardized by the
National Electrical Manufacturers Association The National Electrical Manufacturers Association (NEMA) is the largest trade association of electrical equipment manufacturers in the United States. Founded in 1926, it advocates for the industry, and publishes standards for electrical product ...
(NEMA). The devices are named using the format NEMA n-mmX, where ''n'' is an identifier for the configuration of pins and blades, ''mm'' is the maximum current rating, and ''X'' is either P for plug or R for receptacle. For example, NEMA 5-15R is a configuration type 5 receptacle supporting 15 A. Corresponding ''P'' and ''R'' versions are designed to be mated. Within the series, the arrangement and size of pins will differ, to prevent accidental mating of devices with a higher current draw than the receptacle can support.


NEMA 1-15 ungrounded (Type A)

NEMA-1 plugs have two parallel blades and are rated 15 A at 125 volts. They provide no ground connection but will fit a grounding NEMA 5-15 receptacle. Early versions were not polarised, but most plugs are polarised today via a wider neutral blade. (Unpolarised
AC adaptor An AC adapter or AC/DC adapter is a type of external power supply, often enclosed in a case similar to an AC plug. Other common names include wall wart, power brick, wall charger, and power adapter. Adapters for battery-powered equipment may ...
s are a common exception.)
Harvey Hubbell Harvey Hubbell II (December 20, 1857 – December 17, 1927), was an American inventor, entrepreneur, and industrialist. His best-known inventions are the U.S. electrical plug and the pull-chain light socket. In 1888, at the age of thirty- ...
patented a parallel blade plug in 1913, where the blades were equal width (). In 1916 Hubbell received a patent for a polarised version where one blade was both longer and wider than the other (), in the polarised version of NEMA 1-15, introduced in the 1950s, both blades are the same length, only the width varies. Ungrounded NEMA-1 outlets are not permitted in new construction in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
and
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, but can still be found in older buildings.


NEMA 5-15 grounded (Type B)

The NEMA 5-15 plug has two flat parallel blades like NEMA 1-15, and a ground (earth) pin. It is rated 15 A at 125 volts. The ground pin is longer than the line and neutral blades, so the device is grounded before the power is connected. Both current-carrying blades on grounding plugs are normally narrow, since the ground pin enforces polarity. The
National Electrical Contractors Association The National Electrical Contractors Association (NECA) is a trade association in the United States that represents the electrical contracting industry. NECA supports the businesses that bring power, light, and communication technology to buildi ...
's National Electrical Installation Standards (NECA 130-2010) recommends that sockets are mounted with the ground hole up so that a falling object makes first contact with the ground pin. This socket is recommended in IEC standard 60906-2 for 120-volt 60 Hz installations. Tamper-resistant sockets may be required in new residential construction, with shutters to prevent contact by objects inserted into the socket. In
stage lighting Stage lighting is the craft of lighting as it applies to the production of theater, dance, opera, and other performance arts.
, this connector is sometimes known as ''PBG'' for ''Parallel Blade with Ground'', ''Edison'' or ''Hubbell'', the name of a common manufacturer.


NEMA 5-20

The NEMA 5-20 AP variant has blades perpendicular to each other. The receptacle has a T-slot for the neutral blade which accepts either 15 A parallel-blade plugs or 20 A plugs.


Other NEMA types

30- and 50- Amp rated sockets are often used for high-current appliances such as clothes dryers and electric stoves.


JIS C 8303, Class II unearthed

The Japanese plug and socket appear physically identical to NEMA 1-15. The Japanese system incorporates stricter dimensional requirements for the plug housing, different marking requirements—for example, the ground side of the Alexa smart plug is marked with a clearly identifiable "N"—and mandatory testing and approval by METI or JIS. Older Japanese sockets and multi-plug adaptors are unpolarised—the slots in the sockets are the same size—and will accept only unpolarised plugs. Japanese plugs generally fit into most North American sockets without modification, but polarised North American plugs may require adaptors or replacement non-polarised plugs to connect to older Japanese sockets. In Japan the voltage is 100 V, and the frequency is either 50 Hz (East Japan) or 60 Hz (West Japan) depending on whether the customer is located on the Osaka or Tokyo grid. Therefore, some North American devices which can be physically plugged into Japanese sockets may not function properly.


JIS C 8303, Class I earthed

Japan also uses a grounded plug similar to the North American NEMA 5-15. However, it is less common than its NEMA 1-15 equivalent. Since 2005, new Japanese homes are required to have class I grounded sockets for connecting domestic appliances. This rule does not apply for sockets not intended to be used for domestic appliances, but it is strongly advised to have class I sockets throughout the home.


Soviet standard GOST 7396 C 1 unearthed

This Soviet plug, still sometimes used in the region, has pin dimensions and spacing equal to the Europlug, but lacks the insulation sleeves. Unlike the Europlug, it is rated 6 A. It has a round body like the European CEE 7/2 or flat body with a round base like CEE 7/17. The round base has no notches. The pins are parallel and do not converge. The body is made of fire-resistant
thermoset plastic In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening (" curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and ...
. The corresponding 6 A socket accepts the Europlug, but not others as the 4.5 mm holes are too small to accept the 4.8 mm pins of CEE 7/4, CEE 7/6 or CEE 7/7 plugs. There were also moulded rubber plugs available for devices up to 16 A similar to CEE 7/17, but with a round base without any notches. They could be altered to fit a CEE 7/5 or CEE 7/3 socket by cutting notches with a sharp knife. File:Soviet Plug Type1 6A 250V.jpg, Soviet grip plug, 6 A 250 V AC, thermoset plastic File:Soviet Plug Type2 6A 250V.jpg, Soviet round plug, 6 A 250 V AC, thermoset plastic, half height File:Soviet moulded rubber plugs 6A 250V cut.jpg, Moulded rubber Soviet plugs cut with knife so that they can fit into CEE 7/3 socket. Originally the plugs had a round base. File:Soviet shaver power cord.jpg, Soviet shaver power cord. The plug is similar to CEE7/16, but has different configuration. Thermoplastic plug is rated 6 A and 250 V.


Swiss SN 441011 (Type J)

The Swiss standard, also used in
Liechtenstein Liechtenstein (), officially the Principality of Liechtenstein (german: link=no, Fürstentum Liechtenstein), is a German-speaking microstate located in the Alps between Austria and Switzerland. Liechtenstein is a semi-constitutional monarchy ...
, is ''SN 441011'' (until 2019 ''SN SEV 1011) Plugs and socket-outlets for household and similar purposes''. The standard defines a hierarchical system of plugs and sockets with two, three and five pins, and 10 A or 16 A ratings. Sockets will accept plugs with the same or fewer pins and the same or lower ratings. The standard also includes three-phase devices rated at 250 V (phase-to-neutral) / 440 V (phase-to-phase). The Swiss standard does not require the use of child protective shutters. The Swiss standard was first described in 1959.


10 A plugs and sockets (Type J)

SEV 1011 defines a "Type 1x" series of 10 A plugs and sockets. The type 11 plug is unearthed, with two 4 mm diameter round pins spaced 19 mm apart. The type 12 plug adds a central 4 mm diameter round earth pin, offset by 5 mm. The type 12 socket has no recess, while the type 13 socket is recessed. Both sockets will accept type 11 and type 12 plugs, and also the 2.5 A
Europlug The Europlug is a flat, two-pole, round-pin domestic AC power plug, rated for voltages up to 250 V and currents up to 2.5 A.shock Shock may refer to: Common uses Collective noun *Shock, a historic commercial term for a group of 60, see English numerals#Special names * Stook, or shock of grain, stacked sheaves Healthcare * Shock (circulatory), circulatory medical emergen ...
hazard when partially inserted into non-recessed sockets. The IEC type J designation refers to SEV 1011's type 12 plugs and type 13 sockets. Unique to Switzerland is a three-phase power socket compatible with single-phase plugs: The type 15 plug has three round pins, of the same dimensions as type 12, plus two smaller flat rectangular pins for two additional power phases. The type 15 socket is recessed, and has five openings (three round and two flat rectangular). It will accept plugs of types 11, 12, 15 and the Europlug.


16 A plugs and sockets

SEV 1011 also defines a "Type 2x" series of 16 A plugs and sockets. These are the same as their 10 A "Type 1x" counterparts, but replace the round pins with 4 mm × 5 mm rectangular pins. The sockets will accept "Type  1x" plugs. The unearthed type 21 plug has two rectangular pins, with centres 19 mm apart. The type 23 plug adds a central rectangular earth pin, offset by 5 mm. The recessed type 23 socket will accept plugs of types 11, 12, 21, 23 and the Europlug. Again, the three-phase power socket is compatible with single-phase plugs, either of 10 A or 16 A ratings: The type 25 plug has three rectangular pins of the same dimensions as type 23, plus two rectangular pins of the same dimensions as type 15. The corresponding type 25 socket is recessed and will accept plugs of types 11, 12, 15, 21, 23, 25 and the Europlug.


Adaptors etc.

A 2012 appendix to SEV 1011:2009, ''SN SEV 1011:2009/A1:2012 Plugs and socket-outlets for household and similar purposes – A1: Multiway and intermediate adaptors, cord sets, cord extension sets, travel adaptors and fixed adaptors'' defines the requirements applicable to multiway and intermediate adaptors, cord sets, cord extension sets, and travel and fixed adaptors, it covers the electrical safety and user requirements, including the prohibition of stacking (the connection of one adaptor to another). Non-conforming products must be withdrawn from the Swiss market before the end of 2018.


Pictures


Thai three-pin plug TIS 166-2549 (Type O)

Thai Industrial Standard (TIS) 166-2547 and its subsequent update TIS 166-2549 replaced prior standards which were based on NEMA 1-15 and 5-15, as Thailand uses 220 V electricity. The plug has two round power pins 4.8 mm in diameter and 19 mm in length, insulated for 10 mm and spaced 19 mm apart, with an earthing pin of the same diameter and 21.4 mm in length, located 11.89 mm from the line connecting the two power pins. The earth pin spacing corresponds to that of NEMA 5 and provides compatibility with prior hybrid three-pin sockets, which accept NEMA 1-15, NEMA 5-15 and Europlugs, all of which have been variably used in Thailand. The hybrid socket is also defined in TIS 166-2547, in addition to a plain three-round-pin socket, with plans to replace the former and phase out support for NEMA-compatible plugs. Sockets are polarised (as in NEMA 5-15). The plug is similar to, but not interchangeable with, the Israeli SI32 plug. The Thai plug is designated as "Type O" at IEC World Plugs.


Comparison of standard types


Adaptors


Travel adapters

Adapters between standards are not included in the standards, and as a result they have no formal quality criteria defined. Physical compatibility does not ensure that the appliance and socket match in frequency or voltage. Adaptors allow travellers to connect devices to foreign sockets, but do not change voltage or frequency. A
voltage converter A voltage converter is an electric power converter which changes the voltage of an electrical power source. It may be combined with other components to create a power supply. AC and DC AC voltage conversion uses a transformer. Conversion from one ...
is required for electrical compatibility in places with a different voltage than the device is designed for. Mismatch in frequency between supply and appliances may still cause problems even at the correct voltage.


Multisocket adaptors

Multisocket adaptors allow the connection of two or more plugs to a single socket. They are manufactured in various configurations, depending on the country and the region in which they are used, with various ratings. In Europe for example, they are called double or triple adaptors, and transform one socket into a multiple socket. This allows connecting more than one electrical consumer item to one single socket and is mainly used for low power devices (TV sets, table lamps, computers, etc.). They are usually rated at 6 A 250 V, 10 A 250 V, or 16 A 250 V. This is the general rating of the adaptor, and indicates the maximum total load in amps, regardless of the number of sockets used (for example, if a 16 A 250 V adapter has four sockets, it would be fine to plug four different devices into it that each consume 2A as this represents a total load of only 8A, whereas if only two devices were plugged into it that each consumed 10A, the combined 20A load would overload the circuit). In some countries these adaptors are banned and are not available in shops, as they may lead to fires due to overloading them. Adaptors can be made with ceramic, Bakelite, or other plastic bodies.


Unusual types


Lampholder plug

A lampholder plug fits into a light socket in place of a
light bulb An electric light, lamp, or light bulb is an electrical component that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the soc ...
to connect appliances to lighting circuits. Where a lower rate was applied to electric power used for lighting circuits, lampholder plugs enabled the consumers to reduce their electricity costs. Lampholder plugs are rarely fused. Edison screw lampholder adaptors (for NEMA 1-15 plugs) are still commonly used in the Americas. File:Lampholder plugs.jpg, Italian bypass lampholder plugs with Edison screw mount. Left: early type (porcelain and brass, c. 1930); right: late type (black plastic, c. 1970) File:Lampholder plug adapter.jpg, Lampholder plug (US, circa 1950-1960)


Soviet adaptor plugs

Some appliances sold in the Soviet Union had a flat unearthed plug with an additional pass-through socket on the top, allowing a stacked arrangement of plugs. The usual Soviet apartment of the 1960s had very few sockets, so this design was very useful, but somewhat unsafe; the brass cylinders of the secondary socket were uncovered at the ends (to allow them to be unscrewed easily), recessed by only 3 mm, and provided bad contact because they relied on the secondary plug's bisected expanding pins. The pins of the secondary plug (which lacked insulation sleeves) could not be inserted into the cylindrical sockets completely, leaving a 5 mm gap between the primary and secondary plugs. The adaptors were mostly used for low power appliances (for example, connecting both a table lamp and a radio to a socket).


UK Walsall Gauge plug

Unlike the standard BS 1363 plugs found in the UK, the earth pin is on a horizontal axis and the live and neutral pins on a vertical axis. This style of plug/socket was used by university laboratories (from batteries) and the
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...
, and is still in use on parts of the
London Underground The London Underground (also known simply as the Underground or by its nickname the Tube) is a rapid transit system serving Greater London and some parts of the adjacent ceremonial counties of England, counties of Buckinghamshire, Essex and He ...
for 110VAC voltage supply. In the 1960s they were used for 240VDC in the Power laboratory of the Electrical Engineering department of what was then University College, Cardiff. Power was supplied by the public 240VDC mains which remained available in addition to the 240VAC mains until circa 1969, and thereafter from in-house rectifiers. They were also used in the
Ministry of Defence Main Building The Ministry of Defence Main Building or MOD Main Building, also known as MOD Whitehall or originally as the Whitehall Gardens Building, is a Listed building, grade I listed government office building located on Whitehall in London. The building w ...
on circuits powered from the standby generators to stop staff from plugging in unauthorised devices. They were also known to be used in some British Rail offices for the same reason.


Italian BTicino brand Magic security connector

The Italian manufacturer BTicino in the 1960s introduced an alternative to the Europlug or CEI 23-16 connectors then in use. The socket is rectangular, with lateral key pins and indentations to maintain polarisation, and to prevent insertion of a plug with different current ratings. Three single-phase general purpose connectors were rated 10 A, 16 A and 20 A; and a three-phase industrial connector rated 10 A; all of them have different key-pin positioning so plugs and sockets cannot be mismatched. The socket is closed by a safety lid (bearing the word ‘'Magic'’ on it) which can be opened only with an even pressure on its surface, thus preventing the insertion of objects (except the plug itself) inside the socket. The contacts are positioned on both sides of the plug; the plug is energised only when it is inserted fully into the socket. The system is not compatible with Italian CEI plugs, nor with Europlugs. Appliances were never sold fitted with these security plugs, and the use of adaptors would defeat the safety features, so the supplied plugs had to be cut off and replaced with the security connector. Even so, the ''Magic'' security system had some success at first because its enhanced safety features appealed to customers; standard connectors of the day were considered not safe enough. The decline of the system occurred when safety lids similar to the Magic type were developed for standard sockets. In Italy, the system was never definitively abandoned. Though very rarely seen today, it is still marked as available in BTicino’s catalogue, (except for the three-phase version, which stopped being produced in July 2011). In Chile, 10 A Magic connectors are commonly used for computer/laboratory power networks, as well as for communications or data equipment. This allows delicate electronics equipment to be connected to an independent circuit breaker, usually including a
surge protector A 'surge protector'' (or spike suppressor, surge suppressor, surge diverter, surge protection device (SPD) or transient voltage surge suppressor (TVSS) is an appliance or device intended to protect Electronics, electrical devices from voltage s ...
or an
uninterruptible power supply An uninterruptible power supply or uninterruptible power source (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. A UPS differs from an auxiliary or emergency power system ...
backup. The different style of plug makes it more difficult for office workers to connect computer equipment to a standard unprotected power line, or to overload the UPS by connecting other office appliances. In Iceland, Magic plugs were widely used in homes and businesses alongside Europlug and Schuko installations. Their installation in new homes was still quite common even in the late 1980s.


Single phase electric stove plugs and sockets

The plugs and sockets used to power
electric stove An electric stove or electric range is a stove with an integrated electrical heating device to cook and bake. Electric stoves became popular as replacements for solid-fuel (wood or coal) stoves which required more labor to operate and maintain. ...
s from a single-phase line have to be rated for greater current values than those used with three-phase supply because all the power has to be transferred through two contacts, not three. If not hardwired to the supply, electric stoves may be connected to the mains with an appropriate high power connector. Some countries do not have wiring regulations for single-phase electric stoves. In Russia, an electric stove can often be seen connected with a 25 or 32 A connector. In Norway and parts of Sweden a 25 A grounded connector, rectangular shaped with rounded corners, is used for single phase stoves. The connector has three rectangular pins in a row, with the grounding pin longer than other two. The corresponding socket is recessed to prevent shocks. The Norwegian standard is NEK 502:2005 – standard sheet X (socket) and sheet XI (plug). They are also known as the two pole and earth variants of CEE 7/10 (socket) and CEE 7/11 (plug).


See also

*
DC connector A DC connector (or DC plug, for one common type of connector) is an electrical connector for supplying direct current (DC) power. Compared to domestic AC power plugs and sockets, DC connectors have many more standard types that are not intercha ...
* History of AC power plugs and sockets *
IEC 60309 IEC 60309 (formerly IEC 309 and CEE 17, also published by CENELEC as EN 60309) is a series of international standards from the International Electrotechnical Commission (IEC) for "plugs, socket-outlets and couplers for industrial purp ...
high-power industrial and polyphase connectors *
IEC 60320 IEC 60320 Appliance couplers for household and similar general purposes is a set of standards from the International Electrotechnical Commission (IEC) specifying non-locking connectors for connecting power supply cords to electrical appliances ...
appliance connectors *
Industrial and multiphase power plugs and sockets Industrial and multiphase plugs and sockets provide a connection to the electrical mains rated at higher voltages and currents than household plugs and sockets. They are generally used in polyphase systems, with high currents, or when protection f ...
*
Mains electricity Mains electricity or utility power, power grid, domestic power, and wall power, or in some parts of Canada as hydro, is a general-purpose alternating-current (AC) electric power supply. It is the form of electrical power that is delivered to h ...
*
Mains electricity by country Mains electricity by country includes a list of countries and territories, with the plugs, voltages and frequencies they commonly use for providing electrical power to low voltage appliances, equipment, and lighting typically found in homes an ...
lists voltage, frequency, and connector types for over 200 countries *
Perilex Perilex is the trade name for an approved indoor three-phase electric power connector system used in Germany, the Netherlands and Sweden. It has mostly been superseded by the IEC 60309 system used throughout Europe. There are two variants, a mo ...
*
Plug load Plug load is the energy used by products that are powered by means of an ordinary AC plug (e.g., 100, 115, or 230 V). This term generally excludes building energy that is attributed to major end uses (HVAC, lighting, water heating, etc.) Definitio ...
*
Polyphase system A polyphase system is a means of distributing alternating-current (AC) electrical power where the power transfer is constant during each electrical cycle. AC phase refers to the phase offset value (in degrees) between AC in multiple conducting ...
*
Smart plug A smart plug is a power plug also known as wall plugs, sockets, outlets, and electrical connectors, which can be fitted between power cords and sockets to function as a remote controlled power switch. As such, smart plugs can be used to make "d ...
*
Stage pin connector A stage pin connector, also known as a grounded stage pin (GSP) or grounded pin connector (GPC), is a standard cable type for theatrical lighting in North America and in many countries in the theatre world.Richard Cadena, ''Electricity for the En ...
*
Anderson Powerpole The Anderson Powerpole is a family of electrical connectors by Anderson Power Products (APP), although plug compatible connectors are now available from alternate sources. Specific variants of this series of connectors have become de facto stan ...


References


External links


Digital Museum of Plugs and Sockets
(comprehensive collection of plugs and sockets)
Glossary of standards terms


{{Authority control Electrical standards Electrical wiring Mains power connectors