Type C is probably the single most widely used international plug. This two-wire plug is ungrounded and has two round prongs. It is popularly known as the Europlug which is described in CEE 7/16. The plug has two 4 mm round pins, measuring 19 mm in length on centres spaced 18.6 mm apart at the base and 17.5 mm apart at the tip. The two pins have 10 mm long insulated sleeves. They converge slightly, but they are relatively flexible which allows the plug to mate with any socket that accepts 4.0 – 4.8 mm round contacts on 17.5 – 19 mm centres. The plug is generally limited for use in class II applications that require 2.5 amps or less. It is, of course, unpolarised. It is commonly used in all countries of Europe except in the United Kingdom, Ireland, Cyprus and Malta. It is also used in various parts of the developing world. Whereas type C plugs are very commonly used, this is not the case for type C sockets. This kind of socket is the older and ungrounded variant of socket types E, F, J, K or N. Nowadays most countries demand grounded sockets to be installed in new buildings. Since type C sockets are ungrounded, they have become illegal almost everywhere and they are being replaced by type E, F, J, K or N (depending on the country). So as to leave no doubt: only the sockets have become illegal, the plugs remain in use of course. A type C plug fits perfectly into a type E, F, J, K or N socket.

Type E is primarily used in France, Belgium, Poland, Slovakia, the Czech Republic, Tunisia and Morocco.

France, Belgium and some other countries have standardized on a socket which is different from the CEE 7/4 socket (type F) that is standard in Germany and other continental European countries. The reason for incompatibility is that grounding in the E socket is accomplished with a round male pin, which is permanently mounted in the socket. This earth pin is 14 mm long and has a diameter of 4.8 mm.  The plug itself is similar to C except that it is round and has the addition of a female contact to accept the socket’s grounding pin. The plug has two 4.8 mm round pins, measuring 19 mm in length on centres spaced 19 mm apart. The centre-to-centre distance between the female contact and the middle of the imaginary line connecting the two power pins is 10 mm.

In order to bridge the differences between sockets E and F, the CEE 7/7 plug was developed (see photo on the left): it has grounding clips on both sides to mate with the type F socket and a female contact to accept the grounding pin of the type E socket. The original type E plug, which does not have grounding clips, is no longer used, although very rarely it can still be found on some older appliances. Note that the CEE 7/7 plug is polarised when used with a type E outlet. The plug is rated at 16 amps. Above that, equipment must either be wired permanently to the mains or connected via another higher power connector such as the IEC 60309 system. A type C plug fits perfectly into a type E socket. The socket is recessed by 15 mm, so partially inserted plugs do not present a shock hazard.

Type F is used, for instance, in Germany, Austria, the Netherlands, Sweden, Finland, Norway, Portugal, Spain and Eastern Europe.

Plug F is known as CEE 7/4 and commonly called “Schuko plug”, which is the acronym of “Schutzkontakt”, a German word meaning “protection contact” or “safety contact”. The plug was designed in Germany shortly after the First World War. It goes back to a patent (DE 370538) granted in 1926 to Albert Büttner, a Bavarian manufacturer of electrical accessories.

Type F is similar to C except that it is round and has the addition of two grounding clips on the side of the plug. The plug has two 4.8 mm round pins, measuring 19 mm in length on centres spaced 19 mm apart. The distance between either of the two earthing clips and the middle of the imaginary line connecting the centres of the two power pins is 16 mm.

Because the CEE 7/4 plug can be inserted in either direction into the receptacle, the Schuko connection system is unpolarised (i.e. line and neutral are connected at random). It is used in applications up to 16 amps. Above that, equipment must either be wired permanently to the mains or connected via another higher power connector such as the IEC 60309 system.

In order to bridge the differences between sockets E and F, the CEE 7/7 plug was developed. This plug, which is shown above, has earthing clips on both sides to mate with the type F socket and a female contact to accept the earth pin of the type E socket. The original type F plug, which does not have this female contact, is now obsolete, but a rewireable version may still be available at some DIY shops. A type C plug fits perfectly into a type F socket. The socket is recessed by 15 mm, so partially inserted plugs do not present a shock hazard.

Type H is used exclusively in Israel and Palestine. This earthed 16 amp plug is unique to Israel. It has three 4.5 mm round prongs, measuring 19 mm in length and forming a triangle. The centres of the line and neutral pins are spaced 19 mm apart. The centre-to-centre distance between the earth pin and the middle of the imaginary line connecting the two power pins is 9.5 mm.

Type H outlets also accept type C plugs. This was not the case before 1989, when the Israeli plug still had flat prongs. Power outlets made since 1989 accept both flat and round pin plugs. The original flat-bladed type H plugs have now become obsolete, but they can still occasionally be found. This plug is also used in the West Bank and all of the Gaza Strip.

Strictly speaking, type H sockets are incompatible with type E or type F plugs, because the diameter of the Israeli socket contacts is 0.3 mm smaller than the prongs of E/F plugs. However, if you push really hard, you can often force such plugs into an Israeli outlet. Bear in mind, though, that the appliance will not be earthed and that it is very hard to pull the plug back out!

Type H plugs are among the most dangerous ones in the world: the prongs are not insulated (i.e. the pin shanks do not have a black covering towards the plug body like type C, G, I, L or N plugs), which means that if a type H plug is pulled halfway out, its prongs are still connected to the socket! Little children run the risk of electrocuting themselves when pulling such a plug out and putting their fingers around it. Type H outlets are not recessed into the wall, so they do not provide any protection from touching the live pins either.

Type J is used almost exclusively in Switzerland and Liechtenstein. Switzerland has its own standard which is described in SEC 1011. This plug is similar to C, except that it has the addition of a grounding pin. Type J plugs have three 4 mm round pins, measuring 19 mm in length. The centres of the line and neutral prongs are spaced 19 mm apart and they have 10 mm long insulated sleeves. Older versions of this plug have unsleeved pins. Type J looks very much like the Brazilian type N standard, but it is incompatible with it since type J has the earth pin further away from the centre line than type N: the centre-to-centre distance between the earth pin and the middle of the imaginary line connecting the two power pins is 5 mm. This connector system is rated for use in applications up to 10 amps. Above 10 A, equipment must be either wired permanently to the electrical supply system with appropriate branch circuit protection or connected to the mains with an appropriate high power industrial connector. A type C plug fits perfectly into a type J socket.

Type K-Round Pin Plug

Type K is used almost exclusively in Denmark and Greenland. The Danish standard is described in DS 60884-2-D1. Unlike the similar type E plug, the grounding pin is not mounted in the receptacle, but it is on the plug itself. The U-shaped earthing pin is 14 mm long, 4 mm thick and has a 6.5 mm diameter. The line and the neutral pins of type K are round and have a 4.8 mm diameter. They are 19 mm in length and their centres are spaced 19 mm apart. The centre-to-centre distance between the earth pin and the middle of the imaginary line connecting the two power pins is 13 mm. The plug is rated at 16 A. A type C plug fits perfectly into a type K socket. The Danish socket will also accept plug types E and F: however, there is no grounding connection with these plugs because a male ground pin is required on the plug. Because of the huge amount of imported European appliances fitted with E/F plugs, the Danish government decided to make it legal to install type E or F sockets too. So, the expectation is that, in the long term, the standard European type F socket (or – but this is less likely – the less frequently used type E) will eventually replace the Danish type K socket.

Type L is used almost exclusively in Italy, Chile and is also randomly found throughout North Africa. The Italian grounded plug/socket standard, CEI 23-16/VII, includes two styles rated at 10 and 16 amps. Both plug top styles consist of three rounded pins placed in a straight line. They differ in terms of contact diameter and spacing, and are therefore incompatible with each other. The 10 amp version has three 4 mm round pins, measuring 19 mm in length. The centres of the line and neutral pins are spaced 19 mm apart. The distance between the centres of either of the two outer prongs and the centre of the ground pin is 9.5 mm. The 10 amp style socket also accepts type C plugs.

The 16 amp version has three 5 mm round pins, measuring 19 mm in length. The centres of the line and neutral pins are spaced 26 mm apart. The distance between the centres of either of the two outer prongs and the centre of the ground pin is 13 mm. Since both plugs are symmetrical, they can be inserted in either direction, which means they are unpolarised.

Nowadays there are also universal sockets available, of which there are two kinds: first, there is the so-called bipasso receptacle (literally: twin-gauge outlet), a very commonly used socket which accepts C plugs as well as both styles of L plugs. Second, there is the bipasso-Schuko receptacle, which even adds compatibility with plug types E & F.

Type M is used almost exclusively in South Africa, Swaziland and Lesotho.

This plug resembles the Indian type D plug, but its pins are much larger. Type M is a 15 amp plug, and it has three round prongs that form a triangle. The central earth pin is 28.6 mm long and has a diameter of 8.7 mm. The 7.1 mm line and neutral pins are 18.6 mm long, on centres spaced 25.4 mm apart. The centre-to-centre distance between the grounding pin and the middle of the imaginary line connecting the two power pins is 28.6 mm. The South African version of the M plug often has insulated sleeves on the pins to prevent accidental contact with a bare connector while the plug is partially inserted. Although type D is used in India, Sri Lanka and Nepal, type M is also used for larger appliances. Some sockets over there can take both type M and type D plugs. Type M is also used in Israel and the United Arab Emirates for heavy appliances such as air-conditioning circuits (in cases where wall-mounted units are plugged in to a dedicated socket) and certain types of washing machines. In the UK, type M is still pretty much the standard plug for theatre installations, despite efforts to move to the international blue- and red-coloured industrial CEE plugs.

Type N is used almost exclusively in Brazil.  The type N socket and plug are the official standard in Brazil. The plug consists of two pins and a grounding pin. There are two variants: the prongs of the 10 A version have a diameter of 4 mm and a length of 19 mm. The second version, rated at 20 amps, is used for heavier appliances and has 4.8 mm round pins, but also measuring 19 mm in length. The centres of the line and neutral pins are spaced 19 mm apart. The centre-to-centre distance between the earth pin and the middle of the imaginary line connecting the two power pins is 3 mm. Type N sockets were specifically designed to accommodate the ubiquitous type C plugs as well. Type N looks very much like the Swiss type J standard, but it is incompatible with it since type N has the earth pin closer to the imaginary line that connects the two power pins (3 mm instead of 5 mm).

Type N is actually based on the international standard 230 V household plug system, called IEC 60906-1. In 1986, the International Electrotechnical Commission published this standard, which was intended to become the common standard for the whole of Europe (and, by extension, all other regions with 230 V mains). Unfortunately, the effort to adopt it as a European Union standard was put on hold in the mid-1990s. Brazil had been using as many as 10 (!) different types of plugs and sockets, including the frequently used type C. In order to put an end to this proliferation of different socket and plug types, the Brazilian Association of Technical Standards (Associação Brasileira de Normas Técnicas (ABNT)) decided to standardize on IEC 60906-1. In 2001, this standard was adopted in Brazil as NBR 14136 and its implementation started in 2007. This Norma BRasileira 14136, however, is not completely identical to IEC 60906-1: the Brazilian standard has a pin diameter of 4 mm for the 10 A plug and 4.8 mm for the 20 A plug, whereas the original IEC 60906-1 standard only has one single pin diameter of 4.5 mm and a maximum current of 16 A.

Brazil’s standardization on 1 single plug & socket type, however, does entail some risks. Why? Simply because Brazil is one of the very few countries that does not have a standard voltage, but at the same time it has only one official type of socket! In other words, you cannot tell the difference between a 220 V and a 127 V socket! Most states use 127 V electricity, but a couple of them are on 220 V. This means that a 127 V hairdryer bought in the state of Minas Gerais will be destroyed when plugged into a compatible 220 V socket in Distrito Federal! Make sure you check out the local voltage before plugging something in! It must be said, though, that many appliances sold in Brazil are dual voltage, but that’s definitely not the case for all of them.