It is often associated with obsolete wiring installations or where it is found in modern wiring, it is confined to special use cases, particularly for switch-controlled lamps and stage lighting. The type D 2 amp and 5 amp plugs are mainly used for lighting such as table lamps. These were clearly recognisable as two-pin plugs and sockets, but with no indication as to pin size or spacing, they were sold as pairs. By the time the 1911 GEC Catalogue was published two-pin plugs and sockets were being offered with specifications in amps, but still with no indication as to pin size or spacing. The 1911 General Electric Company (GEC) Catalogue included several earthed sockets intended for industrial use. In 1885, two-pin plug designs appeared and in 1889 there were two-pin plugs and sockets in the GEC catalogue. This was shortly followed by patents from W. B. Sayers and G. Hookham; these early designs had rectangular plugs with contact plates on either side. Plugs and sockets for electrical appliances not hardwired to mains electricity originated in the United Kingdom in the 1870s and were initially two-pin designs. In the United Kingdom and in Ireland this system is usually referred to by its pin shape and is simply known as "round pin plugs" or "round pin sockets".

5 A, 10 A and 15 A with a round earth pin and rectangular live and neutral pins. The brass pins appear relatively solid and large compared to others. If you live in an urban area, usually the transformer is quite "large" and has a high capacity but in a rural area, the transformer can be a small one on a pole and only capable of supplying a few homes. They were particularly popular in the Manchester area, although they were installed throughout England, mainly in schools, university accommodation, and government laboratories. The current revision of the standard allows optional shutters similar to those of BS 1363. Current UK wiring regulations require socket outlets installed in homes to be shuttered. The first British standard for domestic three-pin plugs was BS 317 Hand-Shield and Side Entry Pattern Three-Pin Wall Plugs and Sockets (Two Pin and Earth Type) published in 1928. This was superseded in 1930 by BS 372 Side-Entry Wall Plugs and Sockets for Domestic Purposes Part II which states that there are only minor alterations from BS 317. In 1934, BS 372 Part II was in turn superseded by the first edition of BS 546 Two-Pole and Earthing-Pin Plugs and Socket Outlets.

The pin configuration of the Tripin appears virtually identical to modern BS 546 plugs. Following the introduction of BS 4573 in 1970 there were no longer any UK domestic uses for two-pin sockets except for shavers, so BS 372 was renamed "Two-pin Side-entry Wall Plugs And Sockets For Special Circuits" and subsequently withdrawn. A fused 13 A version of this continued to be available after the introduction of BS 1363, illustrating that BS 546 was not used exclusively at any time. The 5 A version has been designated as Type D and the 15 A as Type M in the IEC 60083 plugs and sockets standard. PAS 003 allowed for the design and approval of plugs without earthing intended for class II applications only. BS 73 Wall plugs and sockets (five ampere two-pin without earthing connection) was first published in 1915, and revised in 1919 with the addition of 15 A and 30 A sizes.

BS 546 plugs and sockets are still permitted in the UK, provided the socket has shutters. Neutral is usually at or very near to earth potential, being earthed either at the substation or at the service entrance (neutral-to-earth bonding is not permitted in the distribution board/consumer unit). Although still permitted by the UK wiring regulations, BS 546 sockets are no longer used for general purposes. When BS 546 was in common use domestically in the UK the standard did not require sockets to be shuttered, although many were. A. P. Lundberg & Sons and its pin configuration appears virtually identical to modern BS 546 plugs. The pins of both round pin and rectangular pin plugs are arranged in a triangular fashion, the earth pin being the larger and longer pin at the apex. An adaptor (in the context of plugs and sockets) is defined in IEC 60050 as "a portable accessory constructed as an integral unit incorporating both a plug portion and one or more socket-outlet portions".

If you beloved this write-up and you would like to receive extra details about what are electric cables kindly visit the website.