Standardization
IEC 60309-1 specifies general functional and safety requirements for any form of industrial high-current power connector. IEC 60309-2 specifies a range of mains power connectors with circular housings, and different numbers and arrangements of pins for different applications. IEC 60309-3 dealt with connectors for use in explosive gas environments, but was withdrawn in 1998.
The standardization was originally done by the CEE (Commission internationale de réglementation en vue de l'approbation de l'équipement électrique), being a European certification body that became the IECEE in 1985 (International Commission on the Rules for the Approval of Electrical Equipment) as part of the IEC. It is the same standardization body that had also catered for the home AC plugs in the "CEE 7" series (CEE 7/4 alias German Schuko, CEE 7/5 French and CEE 7/7 French/German hybrid plug, and later the CEE7/16 Europlug). The industrial sockets were standardized in the 1960s in the CEE 17 series that was adopted in the UK as BS 4343 and which were later to become the IEC 60309 standard.
IEC 60309-4 concerns switched socket-outlets and connector interlocks. In the United Kingdom, this standard was first adopted as BS 4343:1968 and has since been replaced by its European equivalent EN 60309:1999, catalogued in the BSI system as BS EN 60309:1999. In the UK these plugs are often referred to as caravan, Commando (a brand name used by MK Electric), CEE industrial, CEEform or simply CEE plugs.
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