Type F is used, for instance, in Germany, Austria, the Netherlands, Sweden, Norway, Finland, 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
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