A receptacle plug is the male half of an electrical push-in, plug and socket connection. The term is a fairly broad description for a wide selection of connections ranging from the garden variety plug on a vacuum cleaner lead to specialized, high voltage industrial plugs. The receptacle plug typically features a set of male pins which fit into corresponding female pins enclosed in a socket. These plugs may be either lead mounted or mount flush as an integral part of an appliance and may be rated for small direct current (DC) voltages or high load, single- or multiphase mains supplies. Receptacle plugs generally contain an insulating housing or a metal housing with an insulating inner insert to prevent short circuits and electrical shocks.
Plug and socket connections are the most common non-permanent electrical connections that supply power to appliances and machines. They are also widely used as junctions in electrical harnesses. Receptacle plugs are available in a huge variety of application-specific and general purpose retrofit designs suitable for an equally extensive list of power ratings. They are also included as standard parts of extension and power supply cables for household and garden appliances, power tools, and machines. It is actually difficult to think of an appliance or piece of equipment which does not utilize a receptacle plug to access its power source.
Receptacle plugs and their corresponding sockets fall into two broad categories: lead mounted and surface mount. Both plug types adhere to a common design concept in that they will typically feature male pins with the female pins enclosed within the powered female socket. This design trend is a safety feature to ensure that the pins are not powered when the plug is exposed, thereby offering protection from short circuits and electrical shocks. Where polarity or phasing is an issue, both types will also include a key feature that ensures the plug is always inserted in the correct orientation to the socket pins.
Common lead mounted receptacle plug units include the two and three pin mains power examples which are standard on most equipment and appliance leads. Other examples include low voltage DC harness variants such as Molex and AMP plugs or heavy duty, three-phase plugs for welding machines and heavy workshop equipment. These plugs usually feature both power and ground pins; some applications such as double insulated appliances don't have a ground connection, however.
Integral plug types include charge connectors for battery powered tools and appliances and built-in plugs encountered on some garden and hand tools. In addition to the non-powered exposed pin safety feature of receptacle plug design, most feature housings designed to offer protection during use. These include molded, insulating materials on outer casings, recessed mating surfaces, and locks which prevent the plugs being inadvertently pulled out of the socket. Plugs with aluminum or steel cases feature an insulating inner housing that isolates the pins from the casing.