IEC GUIDE 103 (1980-06)

Defines two recommended systems of dimensional sizes applicable, in the electrotechnical field, to components, devices and equipment in order to ensure the dimensional interface, bearing in mind at the same time the need to control varieties of sizes. The dimensional systems have been evolved to permit: arrangement of products with a minimum loss of room area and space, dimensional interchangeability of products, replacement of a product by several products of smaller dimensions having the same total area or space requirements or vice versa, dimensional compatibility and determination of interface dimensions of products.