Common electrical adaptors in Hong Kong and the United Kingdom

Plugs and sockets for electrical appliances not hardwired to mains electricity originated in Britain in the 1880s and were initially two-pin designs. These were usually sold as a mating pair, but gradually de facto and then official standards arose to enable the interchange of compatible devices. British standards have proliferated throughout large parts of the former British Empire.

BS 546, Two-pole and earthing-pin plugs, socket-outlets and socket-outlet adaptors for AC (50-60 Hz) circuits up to 250 V is a British Standard for three pin AC power plugs and sockets. Originally published in April 1934, it was updated by a 1950 edition which is still current, with eight amendments up to 1999. BS 546 is also the precursor of current Indian and South African plug standards. The 5 A version has been designated as Type D and the 15 A as Type M. BS 546 plugs and sockets are still permitted in the UK, provided the socket has shutters.

BS 1363, 13 A plugs socket-outlets adaptors and connection units is a British Standard which specifies the most common type of single-phase AC power plugs and sockets that are used in the United Kingdom. Distinctive characteristics of the system are shutters on the neutral and line (see Concepts and Terminology below) socket holes, and a fuse in the plug. It has been adopted in many former British overseas territories. BS 1363 was introduced in 1947 as one of the new standards for electrical wiring in the United Kingdom used for post-war reconstruction. The plug and socket replaced the BS 546 plug and socket, which are still found in old installations or in special applications. BS 1363 plugs have been designated as Type G.

The International Electrotechnical Commission publishes IEC 60050, the International Electrotechnical Vocabulary, which is also available as IEV Online.

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