with an additional 5 mm wide groove cut through the shroud. Colour code The colour of the housing indicates the type of power available. The primary distinction is by rated operating voltage, as follows: Keying In addition to the colour code, connectors are keyed in one of 12 positions to ensure that incompatible utilization voltages cannot be connected. Different voltage and frequency combinations are distinguished by the location of the earth pin (or a plastic projection called the minor keyway, for connectors with no earth pin), as shown in the following table. The earth pin can be in one of twelve locations, described by clock positions 1h through 12h, spaced at 30° intervals around the circle on which all the pins lie. The various positions are referenced from the view of the open side of a socket; the 6 o'clock (6h, 180°) position is at the same angle as the major keyway, and is oriented downwards. The major keyway is a projection on the plug shroud which aligns with a notch on the socket. The earth pin has a larger diameter than the other pins, preventing the wrong type of plug being inserted in a socket. The extra-low voltage connector also supports keying, although in this case the angle is the position of the minor key, assuming the major key is at the 6h position (180°). Minor key positions 5h, 6h and 7h are unavailable, as they would overlap with the major key, but an unkeyed variant exists. Notes Common plugs Red 3P+N+E, 6h The red 3P+N+E, 6h (180°) plug allows connecting to the widespread 400 V three phase power network. The most common ratings are 16 A, 32 A and 63 A, with 125 A less common. Construction sites in central Europe have most of their higher power cabling setup with this three phase socket type as the single phase to neutral voltage of 230 V is available for other devices. So called power splitters with this connector as a 3 phase inlet and 3 groups of single phase outputs with individual circuit breakers are generally used to achieve this, and allow load balancing across the phases, important on generator supplies. Similar configurations are used for outdoor exhibitions, festivals and large events. When looking at the mating face of the socket, the phase sequence should be L1, L2, L3, and then the neutral pin, proceeding clockwise from the earth