User:Deucharman/sandbox

AC power plugs and sockets are devices that allow electrically operated equipment to be connected to the primary alternating current (AC) power supply in a building. Electrical plugs and sockets differ in voltage and current rating, shape, size and type of connectors. The types used in each country are set by national standards, some of which are listed in the IEC technical report TR 60083, Plugs and socket-outlets for domestic and similar general use standardized in member countries of IEC.

Plugs and sockets for portable appliances originated in the 1880s in Britain and were initially two pin designs. These were usually sold as a mating pair, but gradually defacto and then official standards arose to enable the interchange of compatible devices. Co-ordination of technical standards has allowed some types of plugs to be used over wide regions to facilitate trade in electrical appliances, and for the convenience of travellers and consumers of imported electrical goods. Although there are a number of different national standards in mainland Europe, and significant differences in the methods used for earthing, most of them have a 19 mm spacing between the centres of the current carrying pins.

Concepts and terminology
Generally the plug is the movable connector attached to an electrically operated device's mains cable, and the socket is fixed on equipment or a building structure and connected to an energised electrical circuit. The plug has protruding prongs, blades, or pins (referred to as male) that fit into matching slots or holes (called female) in the sockets. Sockets are designed to prevent exposure of bare energised contacts. Sockets may also have protruding exposed contacts, but these are used exclusively for earthing (grounding).

To reduce the risk of users accidentally touching energized conductors and thereby experiencing electric shock, plug and socket systems often incorporate safety features in addition to the recessed slots or holes of the energized socket. These may include plugs with insulated sleeves, recessed sockets, sockets with blocking shutters, and sockets designed to accept only compatible plugs inserted in the correct orientation.

The term plug is in general and technical use in all forms of English, common alternatives being power plug, and electric plug. The normal technical term (in both British and International English) for an AC power socket is socket-outlet, but in non-technical common use a number of other terms are used. In British English the general term is socket, but there are numerous common alternatives, including power point, plug socket, wall socket, and wall plug. In American English receptacle and outlet are common, sometimes with qualifiers such as wall outlet, electrical outlet and electrical receptacle, all of these sometimes to be found in the same document. A socket may be surrounded by a decorative and/or protective cover called a wall plate, face plate, outlet cover, socket cover, or wall cover. In some designs this is an integral piece with the socket itself, bought and installed as a single unit.

Electrical sockets for single phase domestic, commercial and light industrial purposes generally provide either two or three electrical connections to the supply conductors. All two pin sockets provide neutral and line connections, both of which carry current and are defined as live parts. Neutral is usually at or very near to earth potential, usually being earthed either at the service entrance or at the substation. Line (commonly, but technically incorrectly, called live,) carries the full supply voltage relative to the neutral (and to earth). Three pin sockets provide, in addition, a protective earth connection. This allows the exposed metal parts of the appliance to be connected to earth, providing protection to the user should those exposed parts inadvertently come into contact with any live parts within the appliance. Different types of plugs are used for different IEC appliance classes. The assigned class depends on whether or not the device is earthed, and the degree of insulation it incorporates. Class I, for example, refers to earthed equipment which requires a third contact in the plug and socket, while Class II refers to unearthed equipment protected by double insulation.

To ensure that the line side of the appliance wiring is always connected to the line side of the supply requires a plug that can only be inserted into the socket one way round. In safe designs, such polarized plugs cannot be mated with non-polarized sockets. Polarization is maintained by the shape, size, or position of plug pins and socket holes. Polarization ensures that when a single pole switch is used in the line input of an appliance, there will be no internal components at line potential when the switch is off. This provides a measure of extra protection against electric shock.

Types in present use
The basic standard for voltage and frequency is harmonized in European countries at 230 volts, 50 Hz. The IEC maintains a web microsite World Plugs giving arbitrary letter designations for generally compatible types of plugs. World Plugs does not identify the national standards corresponding to each plug letter. The letter codes are often used as a de facto naming standard when comparing different AC power plugs, especially when describing traveller's adapters. Physically identical sockets may be connected to voltages incompatible with an appliance. The letter codes do not identify all the variants of a plug and socket family for different current ratings or for special purposes.

The European Committee for Electrotechnical Standardization (CENELEC) publishes a list of approved plug and socket standards used in the member countries.

CEE 7 standards and Europlug
A number of standards based on two round pins with centres spaced at 19 mm are in use in continental Europe and elsewhere. The sockets are generally compatible with the CEE 7/16 Europlug as well as the corresponding plug type.

CEE 7/4 (German "Schuko")(Type F)
"Schuko" is the colloquial name for a system of AC power plugs and sockets that is defined as CEE 7/4. Schuko plugs are unpolarized, they will fit the socket either way round. The two live round pins are 4.8 mm diameter on centers 19 mm apart, they are 19 mm long. Earthing is provided by two scraping contacts on the top and bottom side of the plug. Schuko sockets have a recess into which the plug is inserted. Although Schuko plugs are considered safe when used with Schuko sockets, they can also mate with other sockets which do not provide an earth contact, resulting in an unsafe connection.

"Schuko" is a short form of the German term Schutzkontakt (literally: protective contact). Schuko connectors are normally rated for 230 V, 50 Hz, for currents up to 16 A. The applicable German standards are: DIN VDE 0620-1, DIN 49440-1 and DIN 49441.

History
The Schuko system originated in Germany, it is believed to date from 1925 and is attributed to Albert Büttner, a Bavarian manufacturer of electrical accessories. Büttner's patent DE 370538 is often quoted as referring to Schuko, but it actually refers to a method of holding together all of the parts of a plug or socket with a single screw which also provides clamping for the wires, there is no mention of earth connection. It is said that when the system was introduced, Germany used a 220 V center tap supply (110 V from either live pin to earth) which meant that fuse links were required in both sides of the appliance along with double pole switches. Variations of the original Schuko plug are used today in more than 40 countries, including most of Continental Europe.

Although Schuko has never been a standard (or the de facto norm) in Belgium or France, it is sometimes encountered in older installations in eastern regions of Belgium and Alsace. In parts of the Republic of Ireland, Schuko was commonly installed until the 1960s.

Safety features
When inserted into the socket recess ( 1 )  the plug establishes protective-earth connection through the scraping contacts ( 2 )  before the live pins ( 3 )  establish contact, thereby preventing users from touching the energized pins. A pair of non-conductive guiding notches ( 4 ) on the left and right side provides extra stability, enabling the safe use of large and heavy plugs (e.g. with built-in transformers or timers).

Compatibility with other plug/socket types


Schuko sockets can accept two-pin unearthed Europlug (CEE 7/16) and CEE 7/17. Less safely, Schuko plugs can be inserted into many two-pin unearthed sockets and into some sockets with a different form of earth connection that will not mate with the earth contacts on the Schuko plug (e.g., some variants of the Danish socket. Many such sockets also lack the cavity required to prevent users from touching the pins whilst inserting the plug.

In Italy, Chile and Uruguay, hybrid versions of Schuko sockets are seen with an extra hole that will take the smaller variant of Italian CEI 23-16/VII plugs. There are also hybrid Schuko sockets with three extra holes and a wider cavity that will also accept the larger variant of Italian plugs.

Schuko sockets are unpolarised; if there is a need to be sure which side is line, the socket's polarity must be tested every time.

Some countries, including Finland, Denmark, Norway and Sweden, require child-proof socket shutters; the German Schuko standard does not have this requirement.

CEE 7/5 (French)(Type E)
French standard NF C 61-314 "Plugs and socket-outlets for household and similar purposes" (which also includes CEE 7/7, 7/16 and 7/17 plugs) defines a round plug with two round pins measuring 4.8 by, on19 mm centres. The plug has a female contact for the 4.8 mm earth pin which projects 15 mm, from the recessed face of the socket. The earth pin is offset by 10 mm from the centre point between the live contacts. A similar standard is also used in Belgium, Poland, the Czech Republic, Slovakia and some other countries. Although the plug is polarised, there is no universally observed standard for placement of the line and neutral. However, the Czech standard recommends the line wire to be on the left side when facing the socket. Add to that the French convention changed circa 2002 from nothing particular, to, if the earth pin was at the top then the line hole in the socket would be on the right looking at the socket. However, the socket may not necessarily be installed with the earth pin at the top. Packaging in France of said sockets is normally marked with correct orientation of the cables. Polarised pre fitted plugs on appliances are therefore connected with the brown to the right pin and the blue to the left, the earth being connected to the hole at the "top" of the plug.

CEE 7/4 plugs are not compatible with the CEE 7/5 socket, the projecting earth pin prevents insertion.

CEE 7/7
To bridge the differences between German and French standards, the CEE 7/7 plug was developed. It is polarised to prevent the line and neutral connections from being reversed when used with a French CEE 7/5 socket, but allows polarity reversal when inserted into a German CEE 7/4 socket. The plug is rated at 16 A.

It has scraping contacts on both sides to connect with the CEE 7/4 socket and a female contact to accept the earthing pin of the CEE 7/5 socket. It is used in most European countries. Currently, appliances are sold with non-rewireable CEE 7/7 plugs attached. This means that the plugs are now identical between countries like France and Germany, but the sockets are different.

History
The Europlug, intended for use with socket-outlets meeting other standards, appeared first in 1963 as Standard Sheet XVI in the second edition of CEE Publication 7, a document that summarized all the national domestic AC plugs and socket-outlets used across Europe. The Europlug is therefore sometimes also referred to as the "CEE 7/16" plug. It was adopted as European standard EN 50075 in July 1990. It has national equivalents in most European countries, as described in IEC 60083. The Europlug is unusual as the standard specifies only a plug, there is no socket-outlet designed specifically for use with it.

Design
This non-rewirable flat, two-pin plug is designed for voltages up to 250 V and currents up to 2.5 A. The dimensions of the Europlug were chosen for compatibility and safe use, such that with continental European domestic power sockets
 * reliable contact is established when the plug is fully inserted;
 * no live conductive parts are accessible while the plug is inserted into each type of socket;
 * it is not possible to establish a connection between one pin and a live socket contact while the other pin is accessible.

Europlugs are only designed for low-power (less than 2.5 A) Class II (double-insulated) devices that operate at normal room temperature and do not require a protective-earth connection. They must be supplied with a flexible cord.

Details
The pins of the Europlug are 19 mm long. They consist of a 9 mm long conductive tip of 4 mm diameter with a rounded end, followed by a 10 mm long flexible insulated shaft of not more than 3.8 mm diameter. The two pins are not exactly parallel and converge slightly; their centres are 17.5 mm apart at the tip and 18.6 mm apart at the base. The elasticity of the converging pins provides sufficient contact force for the Europlug's current rating with a variety of socket-hole arrangements. The entire plug is 35.3 mm wide and 13.7 mm high, and must not exceed these dimensions within 18 mm behind its engagement face (this allows for the recesses on many European socket types). The left and right side of the plug are formed by surfaces that are at 45° relative to the horizontal plane.

Because it is unpolarised, it can be inserted in either direction into a socket, so line and neutral are connected arbitrarily. The separation and length of the pins allow its safe insertion in most CEE 7/5, CEE 7/4 "Schuko", Israeli, CEE 7/7, Swiss, Danish and Italian sockets. Most modern UK dedicated shaver sockets designed to accept BS 4573 shaver plugs also accept Europlugs for applications requiring less than 200 mA.

Incompatibility with UK and Irish sockets
The Europlug is physically not compatible with BS 1363 13 A sockets. The UK wiring system uses ring circuits and requires a suitable fuse to be fitted in each plug to protect the appliance cable, Europlugs do not contain such fuses. BS 1363 sockets contain a child-safety shutter, clause 13.7.2 of BS 1363-2 requires that Europlugs will not open the shutters.

Equipment sold in the UK with a Europlug must be marked with or accompanied by a warning that it is not suitable for use in a UK mains socket. The exception is that shavers, electric toothbrushes and similar personal hygiene products may be supplied with a Europlug as an alternative to the BS 4573 shaver plug. The Europlug is compatible with most 2-pin UK shaver sockets, but these are rated for a maximum of 0.2A.

Fused conversion plugs to BS1363-5 are available for Europlugs, and equipment fitted with these may be legally sold in the UK.

Usage
The Europlug itself is used in class II applications throughout continental Europe. It is also used in the Middle East (Iran), most African nations, South America (Argentina, Bolivia, Brazil, Chile, Peru and Uruguay), Asia (India, Bangladesh, Sri Lanka, Indonesia, Pakistan, and South Korea) as well as Russia and the former Soviet republics, such as Ukraine, Armenia, Georgia, and many developing nations.

CEE 7/17 (German/French)
This plug also has two round pins but the pins are 4.8 mm in diameter like CEE 7/5 and CEE 7/4 and the plug has a round plastic or rubber base that provides mechanical support when inserted in a recessed socket. The base has holes in it to accommodate either side contacts or socket earth pins. It is used for large appliances, and in South Korea for all domestic non-earthed appliances. It is also defined as the Class II plug in Italian standard CEI 23-5. It can also be inserted in to Israeli SI 32 with some difficulty. The Soviet GOST 7396 standard includes both the CEE 7/17 plug and a variant with shape of the CEE 7/17 plug but with the 4.0 mm diameter pins used in the Europlug.

Denmark (Type K)
The Danish plug and socket is defined in Danish Standard DS 60884-2-D1:2011. It has two round pins 4.8 mm diameter on centers 19 mm apart, they are 19 mm long. Earthing is provided by a 14 mm long round pin with one flat side. Sockets are normally recessed and must have child-resistant shutters.

The Danish socket will also accept the CEE 7/16 Europlug or CEE 7/17 plug. CEE 7/4, CEE 7/5, and CEE 7/7 plugs will also fit into the socket, but there will be no earth connection.

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.

Denmark has allowed CEE 7/4 "Schuko" sockets from 15 November 2011.

Italy (Type L)
Italian earthed plugs and sockets are defined by the standard CEI 23-50 which superseded CEI 23-16, this includes two 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.

The 10 A plug has pins which are 4 mm in diameter, the centres spaced 19 mm apart. The 10 A socket can accept Europlugs. The 16 A plug has pins which are 5 mm in diameter, the centres spaced 26 mm apart. The 16 A socket used to be referred to as per la forza motrice (for electromotive force, see above) or sometimes (inappropriately) industriale (industrial). Large appliances are usually sold with Schuko plugs, so 16 A non-rewirable plugs are usually used only in adapters and power cords. Those appliances are always earthed, so unearthed 16 A plugs are now very uncommon, and only a few brands still sell them in rewirable version.

The double standard was initially adopted because in Italy, up to the second half of the 20th century, electricity used for lamps and that used for all other purposes was sold at different tariffs, charged with different taxes, accounted with separated electricity meters, and sent on different wire lines that ended with 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 kept twin wires and twin 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 which is now standardized under CEI 23-50. 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 gauge needs to be connected. Numerous cross adapters were used.

Unearthed Europlugs are also in common use; they are standardized in Italy under CEI 23-5 and fit most of the appliances with low current requirement and double insulation.

Appliances with CEE 7/7 Schuko-French plugs are often sold in Italy too; however most sockets will not accept them since the pins of the CEE 7/7 Schuko-French plugs are thicker than the Italian ones. Adapters are standardized in Italy under CEI 23-57, they are commonly used to connect CEE 7/7 plugs to CEI 23-16/VII sockets, but they cannot exceed 1500 watts and could make an unsafe connection in some cases.

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 simpler type has a central round hole and two figure-8 shaped holes above and below. This design allows the connection of both 10 A and 16 A plugs and the Europlug. The advantage of this socket style is its small, compact face. 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 looks like a Schuko socket, but adds a central earthing hole. This design can accept CEE 7/4 (German), CEE 7/7 (German/French), and Italian 10 A plugs. Some of these sockets may also have figure-8 shaped holes to accept Italian 16 A plugs as well. Its drawback is that it is twice as large as a normal Italian socket and the price is higher; for those reasons Schuko and bipasso-Schuko socket are rarely installed in Italy.

Other types may push compatibility even further. The VIMAR-brand universale (all purpose) socket, for example, accepts CEE 7/4 (German), CEE 7/7 (German/French), Italian 10 and 16 A plugs, and also NEMA 1-15 (USA/Japan) plugs (older versions also had extra holes to accept UK shaver plugs).

Unearthed sockets
Round unearthed sockets have no earth provisions and consequently have been phased out in most countries. (For example, Sweden prohibited them from new installations in 1994.) Countries using the CEE 7/5 and CEE 7/4 standards vary in whether unearthed round sockets are still permitted in environments where the need for earthing is less critical.

Some countries prohibit use of unearthed and earthed sockets in the same room, in the "insulated room" concept, so that people cannot touch an earthed object and one that has become live, at the same time. For example, in Germany, unearthed sockets are rare, found only in very old installations, whereas in the Netherlands they are common in "dry areas" such as in bedrooms or living rooms.

Standards also vary between countries as to whether child-resistant shutters are required. The depth of the sockets also vary between countries and age. Older sockets are so shallow that it is possible to touch the pins of a plug when the plug is inserted deep enough to get electrical power on the pins, while newer sockets are deep enough to protect from this kind of accident. Depending on the country and the age of the socket these may have 4.0 or 4.8 mm sockets. (4.0 mm are usually similar to 6 A GOST 7396 type C1 and 4.8 mm are usually simiar to 16 A GOST 7396 type C1, but for example in Sweden older 4.8 mm sockets are usually marked 10 A or 10 / 16 A stating that at the time no more than 10 A were allowed). The latter accept CEE 7/5 and CEE 7/4 plugs in addition to Europlugs, though without earth connection. Adaptors, trailing sockets, and power strips designed to accept only Europlugs with 4 mm pins may also have plastic barriers in place to prevent CEE 7/17, Schuko or French plugs from entering. The earthed CEE 7/5 and CEE 7/4 sockets were specifically designed to not allow insertion of an unearthed round plug from older appliances that were earthed via other means, but the CEE 7/17 plug has notches to allow it be used in those sockets by devices not requiring an earth. Round unearthed sockets and plugs are for class 0 insulation and are not a kind of Europlug. Europlugs are for class II insulation and designed specifically to plug in CEE 7/5 and CEE 7/4 sockets (and also round unearthed sockets, and some other sockets).

(Type J)
Switzerland has its own standard which is described in SEV 1011 (ASE1011/1959 SW10A-R). This plug is similar to the Europlug (CEE 7/16), except that it has an offset earth pin and the pin shanks are not necessarily insulated (the pins of most modern appliances are), so plugs partially inserted into non-recessed sockets present a shock hazard. However, since 1 January 2013, only partially insulated plugs of type CEE 7/16 (Europlug, unearthed, SEV 1011 type 11) and of type J plugs (SEV 1011 type 12) are allowed to be imported and distributed to reduce the risk of electric shocks. Sockets used in kitchens, bathrooms and other wet areas are recessed, while those used elsewhere are not (after 2016, only recessed sockets are allowed to be installed in any setting, minimizing the risk of electric shocks). Some plugs and adaptors have a tapered form and can be used in either environment, while others will fit only the non-recessed sockets. Swiss sockets accept Swiss plugs or Europlugs (CEE 7/16). There is also a non-earthed two-pin variant with the same pin shape, size, and spacing as the SEV 1011's line and neutral pins, but with a more flattened hexagonal form. It fits into Swiss sockets and CEE 7/16 sockets, and is rated 10 A.

The SEV 1011 earth pin is offset by 5 mm from the centre line of the line and neutral pins.

The system is modular and allows variants with five pins for three phases and square pins for 16 A (and the combination of both—see reference). Above 16 A, equipment must either be hardwired to the electrical supply system with appropriate branch circuit protection, or connected to the mains with an appropriate high power industrial connector.

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 a.c. and are intended for use only on systems having nominal voltages between 200 V and 250 V a.c. The plug pins are 4.0 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 receptacle 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 adopted a non-compliant version of 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 to IEC 60906-1. Use at 125 V is permitted by NBR 14136, which is against the intention of IEC 60906-1.

Soviet standard GOST 7396 C 1 unearthed
This Soviet plug, still widely used in modern Russia, 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 French CEE 7/5 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. The corresponding 6 A socket accepts the Europlug, but not others as the 4.5 holes are too small to accept the 4.8 mm pins of CEE 7/4, CEE 7/5 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 7/4 socket by cutting notches with a sharp knife.

Old Spanish sockets
Some older industrial buildings in Spain used sockets that took a plug rated for higher current and had two flat contacts and a round earth pin, somewhat similar in design to the ones found on American plugs but larger in size. The two flat contacts are spaced further apart than on an American plug. No domestic appliances were ever sold with these plugs.

The line and neutral measure 9 by, and are 30 mm apart. All three pins are 19 mm long, and the earth pin is a cylinder of 4.8 mm diameter.

In the former Soviet Union this socket was and still is commonly used for wiring in places where the voltage is lowered for safety purposes, like in schools, filling stations or in wet areas, and is rated 42 V 10 A AC. Such an unusual connection is intended specifically to make the connection of standard higher-voltage equipment impossible.

Old Greek sockets
Called "Tripoliki" (τριπολική, meaning "three-pole"), the standard had 3 round pins, similarly to the Swiss SEV 1011 and to the post-1989 Israeli/Thai type, virtually abandoned by 1995. Previous to the large-scale adoption of Schuko plugs, this was the only way to use an earthed appliance.

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 stacked arrangement of plugs. This design was very helpful (for the usual Soviet apartment of the 1960s had very few sockets), but somewhat unsafe, as the brass cylinders of the secondary socket were uncovered at the ends (to unscrew them easily), recessed only for 3 mm and provided bad contact because they relied on the secondary plug's bisected expanding pins. The pins of the secondary plug (without insulation sleeves) could not be inserted into the cylinders completely, and were accessible through a 5 mm gap between the primary and secondary plugs.

Italian Bticino brand Magic security connector
This style of connector, produced by Italian manufacturer Bticino, appeared in the 1960s and was intended as an alternative to the Europlug or CEI 23-16/VII connectors then in use. The socket is an almost rectangular socket, with one or more lateral key pins and indentations to prevent inverting the polarised plug, or connecting plugs and sockets with different current ratings. At least four models were produced: three single-phase general purpose connectors rated respectively 10 A, 16 A and 20 A; plus 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 blades positioned on both sides of the plug; the plug is energized only when it is inserted fully into the socket.

The obvious drawback of the system is that it is not compatible with Europlugs. As household appliances were never sold fitted with these security plugs and the use of adapters would defeat all of the newly introduced safety features, once this system is adopted all standard plugs must be cut off and replaced with the appropriate security connector. However, 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 (VIMAR Sicury ) and then applied to standard sockets by third brands and by Bticino itself.

In Italy, the system was never definitively abandoned and, though rarely seen today, is still marked as available in Bticino’s products catalogue, (except for the three-phase version, that is no longer in production from 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 or an uninterruptible power supply 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 stoves from a single-phase line have to be rated for greater current values than ones for three-phase system because all the power has to be transferred through a single line. Electric stoves are often hardwired to the electrical supply system, connected to the mains with an appropriate high power industrial connector or with non-standard high power proprietary domestic connector (as 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 to 32 A connector.