IEC 60309-1 or IEC 60309-2 and a switching device, with a rated operating voltage not exceeding 1000 VDC or VAC and 500 Hz, and a rated current not exceeding 800 A. IEC 60309-5 "Dimensional compatibility and interchangeability requirements for plugs, socket-outlets, ship connectors and ship inlets for low-voltage shore connection systems (LVSC)" applies to a single type of plug, socket-outlet, ship connector and ship inlet, intended to connect ships to dedicated shore supply systems described in IEC/IEEE 80005–3. The standardization was originally done by the CEE (), which became IECEE in 1985 (International Commission on the Rules for the Approval of Electrical Equipment) and is now part of the IEC. (This is the same body that produced the "CEE 7" series of domestic AC plugs.) The industrial sockets were standardized in the 1960s in the CEE 17 series that was adopted in the UK as BS 4343, and which are now the IEC 60309 standard. Preferred current ratings and wire gauges The standard includes preferred current ratings and wire gauges for both International (deemed Series I) and North American (deemed Series II) applications. Series I preferred current ratings (in amps) are: 16, 32, 63, 125, 250, 400, 630 and 800, with wire gauges specified as mm. Series II preferred current ratings (in amps) are: 20, 30, 60, 100, 200, 300, 350, 500 and 600, with wire gauges specified as AWG and circular mil. Environmental protection IEC 60309-2 connectors come in IP44 (splash-proof), IP67 (waterproof) and IP66/IP67 (jet-proof/waterproof) variants. In all cases, the rating applies when detached or mated, but not during the mating process. The more common IP44 variant features a spring-loaded hinged cap over the socket. When a plug is inserted, the cap hooks over a lug on the plug and retains it in place. Fixed connectors are usually installed angled downward to prevent water entering. The IP67 and IP66/IP67 variants include a gasket and a twist-lock ring which seals the two connectors together. Dimensions Plugs have cylindrical connector pins arranged in a circle, with the earth pin larger in diameter than the other pins (used for line/neutral). This is surrounded by a circular shroud on the male connector, which fits into a matching recess on the female connector. The standard defines connectors with 3, 4 and 5 pins, but a non-standard variant with 7 pins (6 in a circle plus one in the centre) is commercially available; this