As electricity became a common method of operating labour-saving appliances, a safe means of connection to the electric system other than using a light socket was needed. According to British Author John Mellanby the first plug and socket in England was introduced by T.T. Smith in 1883, and there were two-pin designs by 1885, one of which appears in the (British) General Electric Company Ltd. catalogue of 1889. Gustav Binswanger, a German immigrant who founded the (British) General Electric Company Ltd, obtained a patent (GB189516898) in 1895 for a plug and socket using a concentric (co-axial) contact system.

 

An early American electrical plug and socket was invented by Harvey Hubbell and patented in 1904. Hubbell's first design was a socket which screwed into a lampholder (like the early lampholder plugs), but with a seperable plug with pins or blades (U.S. Patent 774,250). Other manufacturers adopted the Hubbell pattern and by 1915 they were widespread. Gradually wall sockets were developed to supplement those that screwed into lampholders.

 

The earthed consumer plug has several claimants to its invention. A 1911 book dealing with the electrical products of A. P. Lundberg & Sons of London describes the Tripin earthed plug available in 2.5 Amp and 5 Amp models. The pin configuration of the Tripin appears virtually identical to modern BS 546 plugs. In her 1914 book Electric cooking, heating, cleaning, etc Maud Lucas Lancaster mentions an earthed iron-clad plug and socket by the English firm of Reyrolle and Co. The earliest American patent application for an earthed plug appears to be 11 January 1915 by George P. Knapp, on behalf of the Harvey Hubbell company. This patent covers the use of an earthing pin which extends further than the other two contacts to ensure that it is engaged first. The configuration of the socket was not operable with existing two-contact unearthed plugs. Other earthed sockets that are widely used today are operable with unearthed plugs.

 

The German Schuko-system plug was patented by Albert Büttner in 1926. The current American version of the earthed plug, with two parallel blades and a round earthing pin, was invented by Philip F. Labre, while he was attending the Milwaukee School of Engineering. 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 deduced that if the fan was earthed, the electricity would go to earth through the plug rather than through the person holding it. He was issued a US patent for an earthed socket and plug in 1928. As the need for safer installations became apparent, earthed three-contact systems were made mandatory in most industrial countries.