can be used for star-delta starting of three-phase motors. Pilot contact Connectors rated at 63 A and 125 A may optionally be equipped with a 6 mm pilot contact. This smaller pin in the centre of the connector is shorter than the others, designed to 'make' after all the other pins when connecting a plug and socket, and to 'break' first when disconnecting. It is used to switch off the load. This is useful as disconnecting under load will cause arcing which may cause damage to both the plug and socket, and risk injury to the user. The pilot pin is located in the centre of main contact circle on 4- and 5-pin connectors. On 3-pin (2P+E) connectors, it is located on the contact circle opposite the ground pin. The other connectors are located 105° on either side of the earth pin, rather than 120° as in the smaller variants, to make room for the pilot pin. Extra-low voltage variant The standard specifies an additional, different design for extra-low voltages up to 50 VAC and currents of 16 or 32 A. This resembles, but is larger than, the IEC 60906 DC connector. On the male plug, three 6 mm pins each 20.5 mm long are equally spaced around a 15.4 mm diameter circle, starting at the 12-o'clock position. They are surrounded by a 23 mm long shroud with an inner diameter of 36 mm and an outer diameter of 42 mm. The pin opposite the major key is optional and may be omitted to make a 2-pin variant. The inner surface of the male plug shroud is flattened at the 6-o'clock position. One or two grooves are cut in the male plug shroud to mate with corresponding keys in the female socket. There is a required major groove at the 6-o'clock position and an optional minor groove at the 12-o'clock position. On the female socket, the major key is 4 mm deep at the 6-o'clock position. The width of the major key defines the current rating: 32 A plugs have a narrower 5 mm wide groove, while 16 A plugs have a wider 8 mm groove, and therefore 32 A plugs can be used with 16 A sockets but 16 A plugs cannot be used with 32 A sockets. The optional minor keyway is the same dimension for both current ratings: 4 mm wide at the 12-o'clock position, which mates