AC power plugs and sockets are devices for connecting electrically operated devices to the power supply at any place.
An electric plug is a male electrical connector with contact prongs to connect mechanically and electrically to slots in the matching female socket.
Wall sockets are female electrical connectors that have slots or holes which accept and deliver current to the prongs of inserted plugs. To reduce the risk of injury or death by electric shock, some plug and socket systems incorporate various safety features. Sockets are designed to accept only matching plugs and reject all others.
Electrical plugs and their sockets differ by country in shape, size and type of connectors. The type used in each country is set by national standards legislation. As is known to all, each type is designated by a letter designation from a U.S. government publication, plus a short comment in parentheses giving its country of origin and number of contacts. Subsections then detail the subtypes of each type as used in different parts of the world.
IEC Classes are assigned to electrical devices depending on whether or not they are earthed and the degree of insulation they incorporate. Class I, for example, refers to earthed equipment, while class II refers to unearthed equipment protected by double insulation.
Special purpose sockets may be found in residential, industrial, commercial or institutional buildings. These may be merely labeled or colored, or may have different arrangements of pins or keying provisions. Some special-purpose systems are incompatible with general-purpose lighting and appliances. Examples of systems using special purpose sockets include:
- “clean” ground for use with computer systems,
- emergency power supply,
- uninterruptible power supply, for critical or life-support equipment,
- isolated power for medical instruments,
- “balanced” or “technical” power used in audio and video production studios,
- theatrical lighting
- outlets for electric clothes dryers, electric ovens, and air conditioners with higher current rating.
Depending on the nature of the system, special-purpose sockets may just identify a reserved use of a system (for example, computer power) or may be physically incompatible with utility sockets to prevent use of unintended equipment which could create electrical noise or other problems for the intended equipment on the line.
