AC power plugs and sockets

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AC power plugs and sockets are devices that connect appliances, portable light fixtures, and other electrically-operated devices to the commercial power supply so that electric power can flow to them. Plugs and sockets used for household purposes are often the same as those used in industrial or commercial applications for circuits of similar voltage and current rating. Power plugs are male electrical connectors that fit into female electrical sockets. They have contacts that are pins or blades that connect mechanically and electrically to holes or slots in the socket. Plugs usually have a live or hot contact, a neutral contact, and an optional earth or Ground contact. Many plugs make no distinction between the live and neutral contacts, and in some cases they have two live contacts. The contacts may be steel or brass, and may be zinc, tin or nickel plated. Power sockets, power receptacles, or power outlets are female electrical connectors that have slots or holes which accept the pins or blades of power plugs inserted into them and deliver electricity to the plugs. Sockets are usually designed to reject any plug which is not built to the same electrical standard. Some sockets have a pin that connects to a hole on the plug, for a ground contact.

Standard wire colours for flexible cable
Region	Live	Neutral	Protective earth/ground
EU, Australia & South Africa (IEC 60446)	brown	blue	green & yellow
Australia & New Zealand (AS/NZS 3000:2000 3.8.1)	red	black	green/yellow
United States and Canada	black (brass)	white (silver)	green (green)
Standard wire colours for fixed cable
Region	Live	Neutral	Protective earth/ground
EU (IEC 60446) including UK from 31 March 2004	brown	blue	green & yellow
Australia	red	black	green & yellow (core is usually bare and should be sleeved at terminations)
United States and Canada	black, red, blue(brass)	white (silver)	green or bare (green)
Note: the colours in this table represent the most common and preferred standard colours for single phase wiring however others may be in use, especially in older installations.

Contents 1 The three contacts 1.1 Polarized plugs 1.2 Differences in terminology 2 History of plugs and sockets 3 Proliferation of standards 4 World maps by plug/socket and voltage/frequency 5 Types of plug and sockets 5.1 Plugs and sockets in present use 5.1.1 Type A (North American/Japanese 2-pin) 5.1.2 Type B (American 3-pin or U-ground) 5.1.3 Type C (European 2-pin) 5.1.4 Type D (Old British 3-pin) 5.1.5 Type E (French 2-pin, female earth) 5.1.6 Type F (German 2-pin, side clip earth) 5.1.7 Type E and F hybrid 5.1.8 Type G (British 3-pin) 5.1.9 Type H (Israeli 3-pin) 5.1.10 Type I (Australian/New Zealand & Chinese/Argentinian 2/3-pin) 5.1.11 Type J (Swiss 3-pin) 5.1.12 Type K (Danish 3-pin) 5.1.13 Type L (Italian 3-pin) 5.1.14 Type M (see D) 5.1.15 Multi-standard sockets 5.1.16 Proposed common standard IEC 60906-1 5.2 Obsolete and unusual plugs and sockets 5.2.1 Old Spanish sockets 5.2.2 The British electric clock connector 5.2.3 NEMA 2-15, and 2-20 5.2.4 Unusual NEMA 1-15 5.2.5 American "Type I" 10 A/250 V or 15 A/125 V 5.2.6 Perpendicular duplex outlet, USA 5.2.7 Combination parallel and tandem duplex outlets, USA 5.2.8 Dormond & Smith (D&S) 5.2.9 Walsall Gauge 13A plug 6 Safety notes 7 See also 8 References 8.1 Notes 8.2 General 9 External links

[edit] The three contacts

In most countries, household power is single-phase electric power, with two or three wired contacts at each outlet:

• The live wire (also known as phase, hot or active contact), carries alternating current from the power grid to the household.
• The neutral wire returns current to the source.
• The earth wire (known as ground in American English) is only intended to carry electric current when the connected equipment develops an insulation fault. It is generally connected to metal cases and other parts of the equipment which may come into contact with humans, or should otherwise never carry a voltage. Electromagnetic interference filters and surge protectors dispose of unwanted electric charges via the earth wire.

[edit] Polarized plugs

Polarized plugs and sockets are used for safety reasons, and in some cases are required by government regulation. Polarized connectors are used to maintain the identity of the neutral conductor in the connected equipment. This is important so that switches, for example, interrupt only the live wire of the circuit. Polarization is maintained by the shape, size, or position of plug pins and socket holes to ensure that a plug fits only one way into a socket.

If the neutral wire was interrupted instead, while the device would deactivate (due to the opening of the electrical circuit), its internal wiring would still be energized. This can present a shock hazard if the device is opened, because the human body would create a circuit - a path to a voltage different than that of the live wire. Confusion between hot and neutral wires in the behind-the-walls household wiring can thus create a safety hazard.

[edit] Differences in terminology

There are significant differences between American English and British English in talking about power plugs and sockets.

British English	American English	Meaning
mains power	line power	The primary electrical power supply wires entering a building, connected to the Main fuses or breakers.
domestic power		Single-phase 230v power as used in a single-family residence
earth connection	ground or grounding connection	Safety connection to the earth or ground
live connection	hot connection	Phase ("active") connection
neutral connection	neutral connection	return connection
flex/mains lead, mains wire/wiring	cord/cable	Flexible electric cable from plug to appliance
socket, electrical wall outlet, power point	outlet, receptacle, socket	Female part of an electrical connection or electrical fitting in a wall outlet
pin, plug	prong or plug	Male part of an electrical connector

In the United States, the live contact may be called live or hot, and is the more narrow, flat connector. The neutral contact may be called cold, neutral, return, the grounded conductor, or (in the National Electrical Code), the identified conductor, and is the wider, flat connector. The earth contact is called ground or the grounding conductor, and is the round connector.

In the United Kingdom the word "line" is occasionally used to denote the live terminal or wire. In electrical engineering, the line voltage is that between the live conductors of the three-phase distribution system, while the phase voltage is that between live and neutral.

Live conductors are called phases when there is more than a single phase in use. Pins are also known as prongs, contacts or terminals.

In Australia, the live contact is called active.

[edit] History of plugs and sockets

When electricity was first introduced into the household, it was primarily used for lighting. At that time, many electricity companies operated a split-tariff system where the cost of electricity for lighting was lower than that for other purposes. This led to portable appliances (such as vacuum cleaners, electric fans, and hair driers) being connected to the light fitting. The picture to the right shows a 1909 electric toaster with a light bulb socket plug.

However, as electricity became a common method of lighting houses and operating labour-saving appliances, a means of connection to the electric system other than using a light socket was needed. The original two blade electrical plug and socket were invented by Harvey Hubbell and patented in 1904. Other manufacturers adopted the Hubbell pattern and by 1915 they were widespread, although even by the early 1920s in the United States, household and light commercial equipment was still powered through cables connected with Edison screw-base adapters to lampholders. ^{[1] [2]}

^[3]

The three prong plug was invented by Philip F. Labre, while he was attending the Milwaukee School of Engineering (MSOE). It is said that his landlady had a cat which would knock over her fan when it came in the window. When she plugged the fan back in, she would get an electric shock. Labre figured out that if the plug were grounded, the electricity would go to earth through the plug rather than his landlady. He applied for and was issued a patent for grounding receptacle and plug on June 5, 1928.^[4] As the need for safer installations became apparent, earthed three-contact systems were made mandatory in most industrial countries.

[edit] Proliferation of standards

During the first fifty years of commercial use of electric power, standards developed rapidly based on growing experience. Technical, safety, and economic factors influenced the development of all wiring devices and a number of different varieties were invented. Gradually the desire for trade eliminated some standards that had been used only in a few countries. Former colonies may retain the standards of the colonizing country, occasionally (as with the UK and a number of its former colonies) after the colonizing country has changed its standard. Sometimes offshore industrial plants or overseas military bases use the wiring practices of their controlling country instead of the surrounding region. In some countries there is no single national standard with multiple voltages, frequencies and plug designs in use, creating extra complexity and potential safety problems for users.

In recent years many countries have settled on one of a few de facto standards, although there are legacy installations of obsolete wiring in most countries of the world. Some buildings have wiring that has been in use for almost a century and which pre-dates all modern standards.

Many manufacturers of electrical devices like personal computers have adopted the practice of putting a single world-standard IEC connector on the device, and supplying for each country a power cord equipped with a standard IEC connector on one end and a national power plug at the other. The device itself is designed to adapt to a wide range of voltage and frequency standards. This has the practical benefit of reducing the amount of testing required for approval, and reduces the number of different product variations that must be produced to serve world markets.

[edit] World maps by plug/socket and voltage/frequency

See also: List of countries with mains power plugs, voltages and frequencies

There are two basic standards for voltage and frequency in the world. One is the North American standard of 110-120 volts at 60 Hz, which uses plugs A and B, and the other is the European standard of 220-240 volts at 50 Hz, which uses plugs C through M. The differences arose for historical reasons as discussed in the article Mains electricity.

Countries on other continents have adopted one of these two voltage standards, although some countries use variations or a mixture of standards. The outline maps show the different plug types, voltages and frequencies used around the world,^[5] colour-coded for easy reference.

[edit] Types of plug and sockets

Electrical plugs and their sockets differ by country in shape, size and type of connectors. The type used in each country is set by national standards legislation.^[6] In this article each type is designated by a letter designation from a U.S. government publication [1], plus a short comment in parentheses giving its country of origin and number of contacts. Subsections then detail the subtypes of each type as used in different parts of the world.

IEC Classes are assigned to electrical devices depending on whether or not they are earthed (grounded) and the degree of insulation they incorporate. Class I, for example, refers to earthed (grounded) equipment, while class II refers to unearthed (ungrounded) equipment protected by double insulation.

[edit] Plugs and sockets in present use

[edit] Type A (North American/Japanese 2-pin)

Main article: NEMA connector

NEMA 1-15 (North American 15 A/125 V ungrounded)

Standardized by the U.S. National Electrical Manufacturers Association^[7] and adopted by 38 other countries, this simple plug with two flat parallel pins, or blades, is used in most of North America and on the east coast of South America on devices not requiring a ground connection, such as lamps and "double-insulated" small appliances. NEMA 1-15 sockets have been prohibited in new construction in the United States and Canada since 1962, but remain in many older homes and are still sold for replacement use only. Type A plugs are still very common because they are compatible with type B sockets.

Early designs could be inserted either way, but some modern plugs make the neutral blade wider than the live blade; such a polarized plug can be inserted only one way. New polarized plugs will not fit in old type A sockets, but both old and new type A plugs will fit in new type A and type B sockets. Some devices that do not distinguish between neutral and live, such as sealed electronic power supplies, are still sold with both pins narrow.

JIS C 8303, Class II (Japanese 15 A/100 V ungrounded)

The Japanese plug and socket are identical to NEMA 1-15. However, the Japanese system incorporates stricter dimensional requirements for the plug housing, different marking requirements, and mandatory testing and approval by MITI or JIS.^[8]

Some older Japanese outlets and multiplug adapters are non-polarized -- the slots in the sockets are the same size - and will only accept non-polarized plugs. Japanese plugs should be able to fit into modern North American outlets without trouble, but North American appliances with polarized plugs may require adapters or replacement non-polarized plugs to connect to older Japanese outlets; or even replacement of the wall socket itself.

Japanese standard wire sizes and the resulting current ratings are somewhat different from those used elsewhere in the world. Japanese voltage is only 100 volts - lower than American voltage - and the frequency in eastern Japan is only 50 hertz instead of 60, so even if a North American plug can be inserted into a Japanese socket, it does not always mean the device will work properly.

[edit] Type B (American 3-pin or U-ground)

Main article: NEMA connector

On the left is a North American grounded (earthed) plug, and in the center is a decora style outlet. A more common style of NEMA 5-15 duplex outlet is shown on the right. This socket will also accept an ungrounded (two prong) plug whether polarized or unpolarized.

NEMA 5-15 (North American 15 A/125 V grounded)

The type B plug has two flat parallel blades like type A, but has a round ground or earthing pin (American standard NEMA 5-15/Canadian standard CSA 22.2, № 42).^[7] It is rated for 15 amperes at 125 volts. The ground pin is longer than the live and neutral blades, so the device is grounded before the power is connected. The neutral blade in the type B socket is wider than the live one to prevent polarized type A plugs being inserted upside-down. Type B plugs often have both pins narrow since the ground pin enforces polarity.

The 5-15 socket is standard in all of North America (Canada, the United States and Mexico). It is also used in Central America, the Caribbean, northern South America (Colombia, Ecuador, Venezuela and part of Brazil), Japan, Taiwan and Saudi Arabia.

Looking directly at a type B outlet with the ground at the bottom, the neutral slot is on the left, and the live slot is on the right. They may be installed with the ground at the top or on either side.

In the theater, this connector is sometimes known as PBG for "Parallel Blade with Ground", or Hubbell, the name of a common manufacturer.

In new residential construction since about 1992, a 20-amp receptacle with a T-slot for the neutral blade allows either 15-ampere parallel blade plugs or 20-ampere plugs to be used.

JIS C 8303, Class I (Japanese 15 A/100 V grounded)

Japan also uses a Type B plug similar to the North American one.^[8] However it is less common than its Type A equivalent.

[edit] Type C (European 2-pin)

(Not to be confused with the 3-blade C13 and C14 IEC connectors)

CEE 7/16 (Europlug 2.5 A/250 V unearthed)

For more details on this topic, see Europlug.

This two-pin plug is probably the single most widely used international plug, popularly known as the Europlug. The plug is unearthed and has two round, 4 mm pins, which usually converge slightly. It can be inserted into any socket that accepts 4 mm round contacts spaced 19 mm apart. It is described in CEE 7/16.^[9] and is also defined in Italian standard CEI 23-5 and Russian standard GOST 7396

The Europlug is used in Class II applications throughout continental Europe (Austria, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Macedonia, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey). It is also used in Middle East, most of Africa, Argentina, Chile, Uruguay, Peru, Bolivia, Brazil, Bangladesh, Indonesia, Pakistan as well as the former Soviet republics, and many developing nations.

This plug is intended for use with devices that require 2.5 A or less. Because it can be inserted in either direction into the socket, live and neutral are connected at random.

The separation and length of the pins allow its safe insertion in most CEE 7/17, French type E, Type H (Israeli 3-pin), CEE 7/4 (Schuko), CEE 7/7 and Type L (Italian 3-pin) outlets.

CEE 7/17 (German/French 16 A/250 V unearthed)

This plug also has two round pins but the pins are 4.8 mm in diameter like types E and F and the plug has a round plastic or rubber base that stops it being inserted into small sockets intended for the Europlug. Instead, it fits only into large round sockets intended for types E and F. The base has holes in it to accommodate both side contacts and socket earth pins. It is used for large Class II appliances. Used in South Korea for all domestic non-earthed appliances, it is also defined in Italian standard CEI 23-5.

BS 4573 (UK shaver)

In the United Kingdom and Ireland, there is a special version of the type C plug for use with shavers (electric razors) in bath or shower rooms.^[10] It has 5 mm diameter pins 16.6 mm apart, and the sockets for this plug can often take unearthed CEE 7/16, US and/or Australian plugs as well. Sockets are often able to supply either 230 V or 115 V. In wet zones, they must contain an isolation transformer compliant with BS 3535.

Variations in sockets

Some Type C sockets can only take 4 mm pins or have plastic barriers in place to prevent Schuko or French plugs from entering. However, many can take 4.8 mm pins and have enough room for a 4.8 mm pin round Schuko or French plug to be inserted, with an unsafe result.

[edit] Type D (Old British 3-pin)

For more details on this topic, see BS 546.

BS 546 (5 A/250 V earthed)

India / Pakistan has standardised on a plug which was originally defined in British standard BS 546. It has three large round pins in a triangular pattern. The BS 546 standard is also used in parts of the Middle East (Kuwait, Qatar) and parts of Asia and the Far East that were electrified by the British. This type was also previously used in South Africa, but has been phased out in favour of the 15 A version there. Similarly, in Ghana, Kenya, and Nigeria, the plug has been mostly replaced by the British 3-pin (Type G). This 5 A plug, along with its 2 A cousin, is sometimes used in the UK for centrally switched domestic lighting circuits, in order to distinguish them from normal power circuits.

BS 546 (15 A/250 V earthed)

This plug is sometimes referred to as type M, but it is in fact merely the 15 A version of the plug above, though its pins are much larger at 7.05 mm × 21.1 mm. Live and neutral are spaced 25.4 mm apart, and earth is 28.6 mm away from each of them. Although the 5 A version is standard in India, Pakistan, Sri Lanka, Nepal, and Namibia, the 15 A version is also used in these countries for larger appliances. Some countries like South Africa use it as the main domestic plug and socket type, where sockets always have an on–off switch built into them. The Type M is almost universally used in the UK for indoor dimmable theatre and architectural lighting installations. It is also often used for non-dimmed but centrally controlled sockets within such installations. The main reason for doing this is that fused plugs, while convenient for domestic wiring (as they allow 32 A socket circuits to be used safely), are not convenient if the plugs and sockets are in hard-to-access locations (like lighting bars) or if using chains of extension leads (since it is hard to figure out which fuse has blown). Both of these situations are common in theatre wiring. This plug is also widely used in Israel, Singapore, and Malaysia for air conditioners and clothes dryers.

[edit] Type E (French 2-pin, female earth)

French type E

France, Belgium, Poland, Czech Republic, Slovakia (after 1 July 2008 also Denmark) and some other countries have standardised on a socket which is not compatible with the CEE 7/4 socket (type F) that is standard in Germany and other continental European countries. The reason for incompatibility is that earthing in the E socket is done by a round male pin permanently mounted in the socket. Sockets are installed with the earth pin upwards and wired with left as live and right as neutral. The plug itself is round with two round pins measuring 4.8 × 19 mm, spaced 19 mm apart and a hole for the socket's earth pin. It will accept Europlug and CEE 7/17 plugs.

As with the German plug below this plug will fit some other types of socket either easily or with force. However, there is no earth connection with such sockets. Also in some cases forcing the plug in may damage the socket.

[edit] Type F (German 2-pin, side clip earth)

CEE 7/4 (German "Schuko" 16 A/250 V earthed)

For more details on this topic, see Schuko.

The type F plug, defined in CEE 7/4 and commonly called a "Schuko plug", is like type E except that it has two earthing clips on the sides of the plug instead of a female earth contact. The Schuko connection system is symmetrical and allows live and neutral to be reversed. The socket also accepts Europlugs and CEE 7/17 plugs. It supplies up to 16 amperes. Above that, equipment must either be wired permanently to the mains or connected via another higher power connector such as the IEC 309 system. It's also used in Spain, Portugal and Sweden.

"Schuko" is an abbreviation for the German word Schutzkontakt, which means "Protective (that is, earthed) contact".

Although Schuko sockets are unpolarized, it is recommended to wire them the same way French sockets are wired (live on left and neutral on right, when looking at the socket), but unfortunately, phase wiring is not yet officially standardised in most of the countries that use this socket type (please see the main Schuko article for details).

Gost 7396 (Russian 10 A/250 V earthed)

For more details on this topic, see GOST 7396.

The countries of the CIS use a standard plug and socket similar to the Schuko standard, defined in Russian Standard Gost 7396. The contacts are also 19 mm apart, but the diameter of the pins is 4.0 mm instead of 4.8 mm. And hence the connectors are rated at 10 rather than 16 amps. It is possible to insert Russian plugs into Schuko outlets, but Russian sockets will not accept type E or F plugs because the holes are too small. This socket also accepts Europlugs, but does not accept CEE 7/17 plugs because they use the larger pin size.

Many official standards in Eastern Europe are virtually identical to the Schuko standard. One of the protocols governing the reunification of Germany required that the DIN and VDE standards would prevail without exception, so the former East Germany had to conform to the Schuko standard. Most other Eastern European countries use the Schuko standard internally but, prior to its collapse, they exported large volumes of appliances to the Soviet Union with the Soviet standard plug installed. Because of that, many of the Russian plugs found their way into other Eastern European countries.

[edit] Type E and F hybrid

CEE 7/7 (French/German 16 A/250 V earthed)

In order to bridge the differences between sockets E and F, the CEE 7/7 plug was developed. It has earthing clips on both sides to connect with the CEE 7/4 socket and a female contact to accept the earthing pin of the type E socket. It's also used in Spain and Portugal. Nowadays, when appliances are sold with type E/F plugs attached, the plugs are CEE 7/7 and non-rewirable. This means that the plugs are now identical between countries like France and Germany; only the sockets are different.

Type E and F plugs that are not compatible with both types of socket are only found if a cheap replacement plug has been attached to a cord that originally had another plug. Better-quality replacements are standard CEE 7/7 and are compatible with both Schuko and French standard sockets.

Note that the CEE 7/7 plug is polarized to prevent the live and neutral connections from being reversed when used with a type E outlet, but allows polarity reversal when inserted into a type F socket. The plug is rated at 16 A. Above that, equipment must either be wired permanently to the mains or connected via another higher power connector such as the IEC 309 system.

[edit] Type G (British 3-pin)

BS 1363 (British 13 A/230-240 V 50 Hz earthed and fused)

For more details on this topic, see BS 1363.

The British Standards 1363 plug. ^[11] This design is not only used in the United Kingdom and Ireland, but also in Sri Lanka, Bahrain, UAE, Qatar, Yemen, Oman, Cyprus, Malta, Gibraltar, Botswana, Ghana, Hong Kong, Macau, Brunei, Malaysia, Singapore, Kenya, Uganda, Nigeria, Iraq, Tanzania and Zimbabwe. BS 1363 is also standard in several of the former British Caribbean colonies such as Belize, Dominica, St. Lucia, Saint Vincent and the Grenadines and Grenada. It is also used in Saudi Arabia in 230v installations although 110V installations using the NEMA connector are more common.

This plug, commonly known as a "13-amp plug", is a large plug that has three rectangular prongs forming a triangle. Live and neutral are 4 × 6 × 18 mm spaced 22 mm apart. 9 mm of insulation over the base of the pins prevents people from touching a bare connector while the plug is partly inserted. Earth is 4 × 8 × 23 mm.

The plug is unusual in that it has a fuse inside, for protection, in addition to a circuit breaker in the distribution panel. The fuse is required to protect the cord, as British wiring standards allow very high-current circuits to the socket. Accepted practice is to choose the smallest standard fuse (3 A, 5 A, or 13 A) that will allow the appliance to function. Using a 13 A fuse on an appliance with thin cord is considered bad practice. The fuse is 1 inch long, conforming to standard BS 1362.

UK wiring regulations (BS 7671) require sockets in homes to have shutters over the live and neutral connections for safety reasons (e.g. to prevent children from inserting metal objects into them). These are incorporated into all BS 1363 sockets and are opened by the insertion of the (longer) earth pin. The shutters also help prevent the use of plugs made to other standards. On plugs for Class II appliances that do not require an earth, the pin is often plastic and serves only to open the shutters and to enforce the correct orientation of live and neutral. It is sometimes possible to open the shutters with a screwdriver to insert Type C Plugs or other plug types, but this should be avoided as such plugs will not have a fuse and will often not fit properly at best.

BS 1363 plugs and sockets started appearing in 1946 and BS 1363 was first published in 1947. By the end of the 1950s, it had replaced the earlier standard (type D) (BS 546) in new installations, and by the end of the 1960s, most earlier type D installations had been rewired to BS 1363 standards. Socket-outlets usually include switches on them for convenience. BS 1363 is considered a very safe system^{[citation needed]}, but the plugs are much larger and heavier than corresponding Euro plugs.

[edit] Type H (Israeli 3-pin)

SI 32 (Israeli 16 A/250 V earthed)

This plug, defined in SI 32 (IS16A-R), is unique to Israel and is incompatible with all other sockets. It has three flat pins to form a Y-shape. "Live" and "Neutral" are spaced 19 mm apart. The Type H plug is rated at 16 A but in practice the thin flat pins cause the plug to overheat when connecting large appliances. In 1989, the SI 32 was revised to use three round 4 mm pins in the same locations as the older standard. Sockets made since 1989 accept both flat and round pins in order to be compatible with both old and new plugs. This also allows the Type H socket to accommodate type C plugs which are used in Israel for non-grounded appliances. Older sockets, from about the 1970s, have both flat and round holes for "Live" and "Neutral" in order to accept both Type C and Type H plugs. As of 2008, "pure" Type H sockets (which accept only old standard Type H plugs) are very rare in Israel.

This plug is also used in the areas controlled by the Palestinian National Authority in the West Bank and all of the Gaza Strip.

[edit] Type I (Australian/New Zealand & Chinese/Argentinian 2/3-pin)

AS 3112 (Australian 10 A/240 V)

For more details on this topic, see AS 3112.

This plug, used in Australia, New Zealand, Fiji and Papua New Guinea, has an earthing pin, and two flat pins forming an upside down V-shape.^[12] The flat blades measure 6.5 × 1.6 mm and are set at 30° to the vertical at a nominal pitch of 13.7 mm. Australasian wall sockets 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 small double-insulated appliances, but the power (wall) outlets always have three pins, including an earth pin.

There are several AS/NZS 3112 plug variants,^[13] including one with a wider earth pin used for devices drawing up to 15 A; sockets supporting this pin will also accept 10 A plugs. There is also a 20 A variant, with all three pins oversized, and 25 and 32 A variants, with the 20 A larger pins and the earthing pin forming an inverted "L" for the 25 A and a horizontal "U" for the 32 A (the 5 variants {10; 15; 20; 25 & 32 ampere sockets} will accommodate all the plugs that are equal or of a lesser current carrying capacity, but not a higher value; i.e. a 10 A plug will be accommodated by all sockets but a 20 A plug will fit only 20, 25 and 32 A outlets).

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 superseded by AS 3112 in 1990. As of 2005, the latest major update is AS/NZS 3112:2004, which mandated insulated pins^[14] by 2005. However, equipment and cords made before 2003 can still be used.

CPCS-CCC (Chinese 10 A/250 V)

Although the pins on the Chinese plug are 1 mm longer, the Australasian plug can be used with mainland Chinese socket. The standard for Chinese plugs and sockets is set out in GB 2099.1–1996 and GB 1002–1996. As part of China's commitment for entry into the WTO, the new CPCS (Compulsory Product Certification System) has been introduced, and compliant Chinese plugs have been awarded the CCC (China Compulsory Certification) Mark by this system. The plug is three wire, grounded, rated at 10 A, 250 V and used for Class 1 applications.

In China, the sockets are installed upside down relative to the Australian one.

China also uses American/Japanese "Type A" sockets and plugs for Class-II appliances. However, the voltage across the pins of a Chinese socket will always be 220, no matter what the plug type.

IRAM 2073 (Argentinian 10 A/250 V)

The Argentinian plug is a three-wire earthed plug rated at 10 A, 250 V defined by IRAM and used in Class 1 applications in Argentina and Uruguay.

This plug is similar in appearance to the Australasian and Chinese plugs. The pin length is same as the Chinese version. The most important difference from the Australasian plug is that the Argentinian plug is wired with the live and neutral contacts reversed.

[edit] Type J (Swiss 3-pin)

SEV 1011 (Swiss 10 A/250 V)

Switzerland has its own standard which is described in SEV 1011. (ASE1011/1959 SW10A-R) This plug is similar to the type C europlug (CEE 7/16), except that it has an earth pin off to one side. Swiss sockets can take Swiss plugs or europlugs (CEE 7/16). This connector system is rated for up to 10 amperes. There is also a less common variant with 3 square pins rated for 16 A. Above 16 A, equipment must either be wired permanently to the electrical supply system with appropriate branch circuit protection, or connected to the mains with an appropriate high power industrial connector.

Switzerland also has a two-pin plug, with the same pin shape, size and spacing as the SEV 1011's live and neutral pins, but with a more flattened hexagonal form. It fits into both Swiss sockets (round and hexagonal) and CEE 7/16 sockets, and is rated for up to 10 A.

[edit] Type K (Danish 3-pin)

Section 107-2-D1 (Danish 10 A/250 V earthed)

This Danish standard plug is described in the Danish Plug Equipment Section 107-2-D1 Standard sheet (SRAF1962/DB 16/87 DN10A-R). The plug is similar to the French type E except that it has an earthing pin instead of an earthing hole (and vice versa on the socket). This makes the Danish socket more unobtrusive than the French socket which is a cavity into the wall to protect the earthing pin from mechanical damage (and to protect from touching the live pins).

The Danish socket will also accept the type C CEE 7/16 Europlug or type E/F CEE 7/17 Schuko-French hybrid plug. Type F CEE 7/4 (Schuko), type E/F CEE 7/7 (Schuko-French hybrid), and earthed type E French plugs will also fit into the socket but should not be used for appliances that need earth contact. The current rating on both plugs is 10 A.

A variation (standard DK 2-5a) of the Danish plug for use only on surge protected computer circuits exists. It fits into the corresponding computer socket and the normal type K socket, but normal type K plugs deliberately don't fit into the special computer socket.

There is a variation for hospital equipment with a rectangular left pin, it 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. However, the shape of the plugs generally makes it difficult to touch the pins when connecting/disconnecting.

Since the early 1990s grounded outlets have been required in all new electric installations in Denmark. Older outlets need not be grounded, but all outlets - including old installations - are required to be protected by RCD/GFCI (HFI in Danish) no later than 1 July 2008.

After 1 July 2008 Wall outlets for type E (French 2-pin, female earth) will be permitted for installations in Denmark.

Sockets for the Schuko F type will not be permitted. The reason is that a large number of currently used Danish plugs will jam when inserted into a Schuko socket. This may cause damage to the socket. It may also result in a bad connection of the pins, which implies the risk of overheating and fire.

• Adapter plugs exist to allow connection of other plugs (British, American etc.) to Danish (non-computer) outlets. These usually are not sold at the local Danish supermarket so visitors wishing to be safe may contact an electrician. However, many international travel adapter sets sold outside Denmark match type C CEE 7/16 (Europlug) and type E/F CEE 7/7 (Schuko-French hybrid) plugs which can readily be used in Denmark as explained above.

[edit] Type L (Italian 3-pin)

The Italian earthed plug/socket standard, CEI 23-16/VII, includes two models rated at 10 A and 16 A that differ in contact diameter and spacing. Both are symmetrical, allowing the live and neutral contacts to be inserted in either direction. CEE 7/16 (type C) unearthed Europlugs are also in common use, and standardized in Italy as CEI 23-5. Appliances with CEE 7/7 Schuko-French plugs are often sold in Italy, but not every socket will accept them, since the pins of the CEE 7/7 Schuko-French plugs are slightly thicker than the italian ones. Adapters are cheap and commonly used to connect CEE 7/7 plugs to CEI 23-16/VII sockets. It is also possible o fit CEE 7/7 Schuko-French plugs to a common italian flat-face sockets, by firmly pushing the plug into the socket. However, this practice is not strongly reccomended, since it can cause damage to the socket by expnding its holes, and the plug may get stuck inside the socket.

CEI 23-16/VII (Italian 10 A/250 V)

The 10 ampere style extends CEE 7/16 by adding a central earthing pin. Thus, CEI 23-16-VII 10 A sockets can accept CEE 7/16 Europlugs. This is the plug shown in the illustrations. Outside of Italy, this plug is found in Syria, Libya, Ethiopia, Chile, Argentina, Uruguay, various countries in North Africa, and occasionally in older buildings in Spain.

CEI 23-16/VII (Italian 16 A/250 V)

The 16 ampere style looks like a bigger version of the 10 A style. The pins are a couple of millimetres further apart, and all three are slightly thicker. The packaging on these plugs in Italy may claim they are a "North European" type. They were also referred to as industriale ("industrial") although this is not a correct definition.

Variations in sockets

Two types of sockets are in common use in modern installations in Italy. One type has a central round hole and two 8-shaped holes above and below. This design allows the connection of both styles of type L plugs (CEI 23-16/VII 10 A and 16 A) and the type C CEE 7/16 Europlug. The advantage of this socket type is its small face.

The other type looks like a type F socket, but adds a central grounding hole. This design accepts CEE 7/7 (type E/F) plugs, in addition to type C and type L 10 A plugs; its disadvantage is that it is twice as large as a normal type L socket. Some of these sockets also have extra holes to accept type L 16 A plugs. Another disadvantage of this kind of socket is the impossibility to accept most of the AC/DC wall-mounted power supplies without an adapter or an extension cord, because of its pit-shaped design.

Older installations often have sockets that are limited to either the 10 A or the 16 A style plug, requiring the use of an adapter if the other style needs to be connected.

[edit] Type M (see D)

BS 546 (South African 15 A/250 V)

Type M is sometimes used to describe the 15 A version of the old British type D, used in South Africa and elsewhere. See type D for details.

[edit] Multi-standard sockets

Sockets that take a variety of incompatible plug types are often seen in developing countries where electrical standards are either lacking or unenforced. These sockets may accept both 120 V and 240 V plugs raising a significant risk of devices being damaged by the wrong voltage. Sometimes they have one or more earth holes to allow 3-pin plugs, but there is a good chance that the ground contact may not actually be connected to earth and the ground contact certainly will not mate with Schuko or French plugs. Great care should be taken to avoid incompatible voltage and grounding connections when using such outlets. Multi-standard devices designed to auto-adapt to different voltage and frequency standards, and devices which do not require a ground contact are best used with these sockets.

[edit] Proposed common standard IEC 60906-1

IEC 60906-1 (Brazilian 16 A/250 V)

For more details on this topic, see IEC 60906-1.

In 1986, the International Electrotechnical Commission published IEC 60906-1, the specification for a plug that looks similar but is not identical to the Swiss (Type J) plug. This plug was intended to become one day the common standard 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.^[15] Brazil — which uses a mix of Europlug and NEMA plugs — later adopted it as national standard NBR 14136 in 2001^[16] and it will be the only plug permitted to be sold with domestic appliances in Brazil from 2009.

[edit] Obsolete and unusual plugs and sockets

[edit] Old Spanish sockets

Older buildings in Spain may have sockets that take a particular type of plug that has two flat contacts and a round earth pin, somewhat similar to the ones found on American plugs.

The live and neutral measure 9 mm × 2 mm × 19 mm, and are 30 mm apart. The earth pin is a cylinder with a diameter of 4.8 mm, and is 19 mm long.

While the plug may look like a USA-style connector at first glance, the spacing between the two flat contacts on this obsolete plug is much wider than found on a standard American plug. Therefore, American plugs will not fit in these sockets.

No appliances are sold with these plugs. Adaptors are necessary.

[edit] The British electric clock connector

Fused plugs and sockets of various proprietary (and non-interchangeable) types are often seen in older public buildings in the UK where they are used to feed AC electric wall clocks. They are physically smaller than conventional socket outlets, commonly being made to fit BESA junction boxes, and often of very low profile, for neatness. Early types were available fused in both poles, later types fused in the live only and provided with an earth pin. Most are equipped with a retaining screw or clip to prevent accidental disconnection. The prevalence of battery powered quartz controlled wall clocks has meant that this connector is rarely seen in new installations.

[edit] NEMA 2-15, and 2-20

Main article: NEMA connector

These ungrounded (unearthed) plugs with two flat parallel pins are variants of the 1-15 but are intended to deliver 240 volts instead of 120. The 2-15 has both pins rotated 90 degrees from vertical and is used for 240 V service at 15 amperes, while the 2-20 has one pin rotated 90 degrees and is used for 240 V service at 20 amperes. NEMA 2 plugs and sockets are rare because they have been prohibited for household use in the United States and Canada for several decades. They are potentially hazardous since they have no ground or neutral, and in some cases plugs can be inserted into incorrect-voltage sockets. Prior to the adoption of the NEMA standard, a plug nearly identical to the 2-20 was used for 120 V at 20 A. A 2-20 plug would fit into either a 5-20 or a 6-20 socket (explained below) which use different voltages.

[edit] Unusual NEMA 1-15

A very rare 5 way outlet, found in an old house in L.A., circa 1928. Note that it is polarized, and thus it would accept modern ungrounded polarized 1-15 plugs.

[edit] American "Type I" 10 A/250 V or 15 A/125 V

The American electrical supply manufacturers Hubbell, Eagle, and possibly others made outlets and plugs that would match Type I plugs and sockets exactly. Type I connectors are used in Australia for 240 V. These American outlets date back to the 1930s to the early 1950s, and predated the modern American 3 prong Type B sockets and plugs. These were meant for appliances that needed grounding, 120 V at 15 Amps, and to be used in laundry rooms for washing machines and such. These did not become popular for the obvious reason that American type A 2 prong plugs would not fit.

The American Type I duplex outlet, made by Hubbell

Demo of the compatibility of the American and Australian Type I plugs

an Eagle brand adaptor to go from a 2 prong Type A outlet to a 3 prong Type I plug

[edit] Perpendicular duplex outlet, USA

Another obsolete outlet, made by Bryant, 125 V 15 A and 250 V 10 A rating. A NEMA 5-20 125 V 20A or 6-20 250 V 20A plug with a missing ground pin would fit this outlet. But a NEMA 2-20 plug is a little too big to fit.

The upper (as seen in the picture) slots connect to silver colored wiring screws on the upper side, and the lower (as seen in the picture) slots connect to brass colored wiring screws on the lower side

[edit] Combination parallel and tandem duplex outlets, USA

This is an extremely old outlet. The brand name looks to be "Nurpolian", and also says "250V 10A". Though it was normally supplied with 120 V.

It accepts normal parallel NEMA 1-15 plugs and also tandem NEMA 2-15 plugs. Both plugs are fed internally by the same supply.

A newer and fairly common version of this is the "T slot" outlet. The locations of the tandem and the parallel slots were combined to create the T shaped slots here. This version also accepts normal parallel NEMA 1-15 plugs and also tandem NEMA 2-15 plugs. And as in the perpendicular outlet pictured further above, a NEMA 5-20 125 V 20 A or 6-20 250 V 20 A plug with a missing ground pin would fit this outlet. But a NEMA 2-20 plug is a little too big to fit. These went out of production sometime in the late '50s or early '60s.

An L shaped pattern was also possible, but few if any were ever made.

[edit] Dormond & Smith (D&S)

The D&S plug was used by the BBC for technical supplies. The LINE pin was a fuse which unscrewed to change, unfortunately these often came unscrewed and were left in the socket, live, when the plug was removed.

There was yet another type popular in the Manchester area at one time, with two staggered rectangular pins and a round earth pin. These were designed for ring-main systems and would often be replaced with the BS1363 type when the householder became annoyed with the difficulty of obtaining plugs. The old plugs would be snapped up by people who still had the D&S system.

[edit] Walsall Gauge 13A plug

These were also used by the BBC for technical supplies at a later date. Unlike the standard BS1363 plugs found in the UK the earth pin is on a parallel axis to the live and neutral pins. They are still in use on parts of the London Underground for low voltage power supply.

Walsall Gauge 13A plug

Walsall Gauge 13A plug

[edit] Safety notes

Improvised connections between plugs and sockets of different systems can be hazardous. Manufactured adapters exist to allow interconnections. However, even if an adapter allows a secure and protected connection between portable equipment and a socket, it may not adjust voltage, frequency, grounding, or overcurrent protection to allow safe use of "foreign" equipment with any particular wall socket. Of reported electrical shock accidents, approximately 0.05% are fatal. ^[17]

[edit] See also

• DC connector
• Double insulated
• IEC connector
• Electricity
• Electric power
• Extension cable
• Ground and neutral
• Industrial and multiphase power plugs and sockets
• List of countries with mains power plugs, voltages and frequencies
• Polyphase system
• Power connector
• Power cord
• Power strip
• Single-phase electric power
• Split-phase electric power
• Two-phase electric power (compare to split-phase)
• Three-phase electric power
• Telephone plugs

[edit] References

[edit] Notes

[edit] General

[edit] External links

• Hubbell History - Invention of the power plug and outlet.
• IEC Zone: Plugs and sockets
• AC Power Cords
• Glossary of standards terms
• Steve Kropla's World Electric Guide
• Change to UK electrical wire colours 2004
• Household electrical safety handbook, Electrical and Mechanical Services Department, Hong Kong Special Administrative Region Government
• IEEE history of Australian power connectors (in MS Word format)
• Information on the electrical systems in use in most countries of the world
• Pictures and dimensions of various plug types
  • Ungrounded plugs
  • Grounded plugs
• IEC High temperature plugs
• South Africa Eskom - Wiring a Plug
• Diagrams of Adapter Plugs