IEC GUIDE 103:1980

Provides definition of 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 first system is based on the most frequently used pitches for the grouping on reference grids in the electrotechnical field, i.e. 0,5 mm, 1 mm, 5 mm, 12.5 mm, 25 mm, 50 mm, 100 mm and 200 mm. The second system gives full priority to satisfy the various interface aspects (additivity, reference grids, 'containers' and 'contained'). It uses a binary based series of sizes, adapting it to usual practice in the electrotechnical field without, however, changing the interface properties.