A contact device installed at the outlet for the connection of an attachment plug.
In North America receptacle standards are created by the National Electrical Manufacturers Association (NEMA). The most commonly encountered residential receptacles in North America are of the NEMA 1, NEMA 5, NEMA 10, and NEMA 14 variety. This is because these standards specify devices for 120/240V split-phase systems, which is a common residential electrical distribution system in North America.
NEMA 1 devices are 2 prong, ungrounded receptacles, rated for 125V. These devices are becoming less and less commonplace, as standards organizations (most notably the National Fire Protection Association (NFPA), creators of the National Electrical Code (NEC)) have move away from the use of ungrounded receptacles. These receptacles consist of an ungrounded (hot) terminal, and a grounded (neutral) terminal.
NEMA 5 devices are 3 prong, grounded receptacles, rated for 125V. These may be the most common type of receptacle in use in North America. This devices have an ungrounded (hot) terminal, a grounded (neutral) terminal, and an equipment grounding terminal.
NEMA 10 devices are 3 prong, ungrounded receptacles, rated for 125/250V. As with NEMA 1 devices, these devices are quickly being replaced by grounded versions. These receptacles were commonly used to supply power for electric clothes dryers, and electric ranges. They consist of two ungrounded (hot) terminals, and one grounded (neutral) terminal.
NEMA 14 devices are 4 prong, grounded receptacles, rated for 125/250V. These devices are quickly replacing ungrounded NEMA 10 devices, due to standards and code changes. They consits of two ungrounded (hot) terminals, one grounded (neutral) terminal, and an equipment grounding terminal.