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The numerals following the hyphen is the current rating of the device in amperes. This number is followed by the letter 'R' to indicate a receptacle (socket) or 'P' to indicate a plug (prongs). As an example, the 5-15R is the common 125 V two-pole, three-wire receptacle rated for 15 A.
Three-prong plugs do not fit into the older, two-prong receptacles. [7] When used as intended, the ground pin of the 3-wire receptacle is to be connected to a grounded cover screw, or to an external ground. In 1969, Underwriters Laboratories mandated three-prong plugs on major appliances for safety. [7]
The socket has a circular recess with two round holes and two earthing clips that engage before live pin contact is made. The pins are 4.8 by 19 mm (0.189 by 0.748 in). The Schuko system is unpolarised, allowing live and neutral to be reversed. The socket accepts Europlugs and CEE 7/17 plugs and also includes CEE 7/7. It is rated at 16 A.
In 1885, two-pin plug designs appeared and in 1889 there were two-pin plugs and sockets in the GEC catalogue. [28] The 1893 GEC Catalogue included three sizes of what was described as Double plug Sockets with capacities described not in amps, but as "1 to 5 lights", "5 to 10 lights" and "10 to 20 lights".
The connection may be removable (as for portable equipment), require a tool for assembly and removal, or serve as a permanent electrical joint between two points. [2] An adapter can be used to join dissimilar connectors. Most electrical connectors have a gender – i.e. the male component, called a plug, connects to the female component, or socket.
A receptacle tester being used to check for some types of improper wiring of an outlet. For this particular tester, proper wiring is indicated by the two yellow lights. The outlet tester checks that each contact in the outlet appears to be connected to the correct wire in the building's electrical wiring. It can identify several common wiring ...
The type 15 plug and socket has 3 round pins of 4 mm diameter, plus 2 flat pins (for L2 and L3). It is designed for three phase applications and is rated at 10 A, 250 V/440 V. The socket will also accept types 11 and 12 plugs, and the Europlug. The type 25 plug and socket has 3 rectangular pins, 4 mm x 5 mm, plus 2 flat pins (for L2 and L3).
During the first 50 years of commercial use of electric power, standards developed rapidly based on growing experience. Technical, safety, and economic factors influenced the development of all wiring devices and numerous varieties were invented. After the two-prong electric plug was introduced in the 1920s, the three-pin outlet was developed.