Co-ordination of technical standards has allowed some types of plugs to be used over wide regions to facilitate trade in electrical appliances, and for the convenience of travellers and consumers of imported electrical goods. Today there are approximately 20 types in common use around the world, and many obsolete socket types are still found in older buildings. A proliferation of types developed to address the issues of convenience and protection from electric shock. Plugs and sockets for portable appliances started becoming available in the 1880s, to replace connections to light sockets with easier to use wall-mounted outlets. The types used in each country are set by national standards, some of which are listed in the IEC technical report TR 60083, Plugs and socket-outlets for domestic and similar general use standardized in member countries of IEC. Electrical plugs and sockets differ in voltage and current rating, shape, size and type of connectors. 'AC power plugs and sockets are devices that allow electrically operated equipment to be connected to the primary alternating current (AC) power supply in a building. The vector stenvils library 'Outlets' contains 57 symbols of electrical outlets for drawing building interior design, electrical floor plans and layouts of AC power plugs and sockets.
