For decades, the International Electrotechnical Commission (IEC) tried to develop a universal domestic power plug, but time and again political and economic issues threw a spanner in the works. In 1986, the IEC finally presented the universal standard plug (type N) to the world, but unfortunately the initial enthusiasm had dampened.

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.

In the other patent, the same type of plug was used with various three-way adaptors that could be connected to lampholders or “a receptacle of any ordinary type”. Hubbell had introduced its own parallel flat pin configuration in 1912. In 1915 there were from 15 to 20 different types of blades and from 15 to 30 different types of receptacles. The line of each was not interchangeable with competing lines.

Following the lead set by the lamp manufacturers in standardizing lamp bases, a conference of the plug and receptacle manufacturers, including Hubbell, was arranged with a view to agreeing a standard configuration. It was a time of great expansion in the use of electrical appliances such as fans, heaters, and cookers, as well as portable devices such as hair curlers and irons, and the public wanted interchangeability. Despite Hubbel’s objections, other manufacturers adopted the Hubbell pattern, omitting Hubbell’s detents, and by 1915 the use of Hubbell’s configuration was widespread. In 1919 Hubbell unsuccessfully attempted to get an injunction to prevent other manufacturers from making receptacles and plugs to the dimensions used by Hubbell. The existence of both “tandem” and parallel pin configurations had led to the introduction in 1914 of some receptacles having both configurations of slots and others having “T” slots.Electricity was the new thing and it generated an increased transnational flow of ideas and products. The report of the court proceedings includes a comprehensive review of the development of the art in the US prior to 1919, based on evidence presented to the Court. Separable plugs had been available for more than a decade prior to Hubbell’s 1904 design. Take the green wire and tightly twist the exposed copper wire so that no strands are standing out. Then slip the green wire into the green terminal and tighten the screw down to secure it. Step 8