Schuko
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"Schuko" (IPA: /'ʃuko/) is the common colloquial name for a system of domestic AC power plugs and sockets that is also known as "Type F" or "CEE 7/4". A Schuko plug features two round pins of 4.8 mm diameter (19 mm long, centers 19 mm apart) for the live and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth (ground). Schuko sockets form a cavity into which the plug is inserted. Schuko plugs and sockets are symmetric AC connectors. They can be mated in two ways, therefore live and neutral can arrive on either pin at the consuming device. As with most types of European sockets, Schuko sockets can accept europlugs. Schuko plugs are considered a very safe design when used with Schuko sockets but they can also mate with other sockets to give an unsafe result.
"Schuko" is a short form of the German term Schutzkontakt (literally: protective contact), which simply indicates that plug and socket are equipped with protective-earth contacts (in the form of clips rather than pins). Schuko connectors are normally used on circuits with 230 V, 50 Hz, for currents up to 16 A.
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[edit] History
The Schuko system originated in Germany and goes back to a patent (DE 370538) granted in 1926 to Albert Büttner, a Bavarian manufacturer of electrical accessories. It is used today in more than 40 countries, including most of Continental and Eastern Europe. In Ireland they are known as "side earth" plugs and are sometimes seen in very old installations. France, Belgium, Czech Republic, Slovakia and Poland use a type of plug and socket with the same size and spacing of the main pins but with a male protective-earth pin on the socket instead of the earth clips and without the guiding notches at the sides. Most modern moulded-on Schuko plugs, and good-quality screw-on replacements - are a hybrid version with an extra hole ("CEE 7/7") that also accommodates the earth pin of French sockets.
[edit] Safety features
When inserted into the socket, the Schuko plug covers the socket cavity (1) and establishes protective-earth connection through the earth clips (2) before the live and neutral pins (3) establish contact, thereby preventing users from touching connected pins. (Hence the Schuko system does not require partially insulated pins as used in the europlug and the British and Australian plugs.) 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).
[edit] Compatibility with other plug/socket types
Schuko sockets can accept two-pin unearthed type C plugs, namely 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 type K). Many such sockets also lack the cavity required to prevent users from touching the pins whilst inserting the plug.
The Russian standard plug defined in GOST 7396 is similar but has 4 mm pins. Therefore, Russian plugs will fit Schuko outlets, but Schuko plugs will not fit Russian outlets. Many former Eastern bloc countries are currently undergoing a process of transition from the (10 A) GOST to the (16 A) Schuko standard.
In Italy, hybrid versions of Schuko sockets are seen with an extra hole that will take the smaller variant of type L plugs. There are also hybrid Schuko sockets with three extra holes and a wider cavity that will also accept the larger variant of type L plugs.
