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In building wiring, multiway switching is the interconnection of two or more electrical switches to control an electrical load from more than one location.A common application is in lighting, where it allows the control of lamps from multiple locations, for example in a hallway, stairwell, or large room.
An older, but still widely used, high-leg delta system uses three phases with 240 volts phase-to-phase for motor loads, and 120 volts for lighting loads by use of a center-tapped transformer; two of the phases are 120 volts to neutral. The third phase, the "high leg" of the system (also referred to as the "wild leg"), has 208 V to neutral and ...
A form of bus duct known as "plug-in bus" is used to distribute power down the length of a building; it is constructed to allow tap-off switches or motor controllers to be installed at designated places along the bus. The big advantage of this scheme is the ability to remove or add a branch circuit without removing voltage from the whole duct.
120 V circuits are the most common, and used to power NEMA 1 and NEMA 5 outlets, and most residential and light commercial direct-wired lighting circuits. 240 V circuits are used for high-demand applications, such as air conditioners , space heaters , electric stoves , electric clothes dryers , water heaters , and electric vehicle charge points .
The 20 A plug has a blade rotated 90° (opposite blade from what would be the "line" blade on a 2-15 or 5-15 plug. This prevents accidental insertion of plugs into outlets that use different voltages), and the 6-20R receptacle has a T-shaped hole to accept both 6-15P and 6-20P plugs (similar to the 5-20R receptacle accepting 5-15P and 5-20P plugs).
Most of the world uses 50 Hz 220 or 230 V single phase, or 400 V three-phase for residential and light industrial services. In this system, the primary distribution network supplies a few substations per area, and the 230 V / 400 V power from each substation is directly distributed to end users over a region of normally less than 1 km radius.
Phasor diagram showing 240 V delta and center-tapped phase (a–c) creating two 120 V pairs. Consider the low-voltage side of a 120/240 V high leg delta connected transformer, where the b phase is the high leg. The line-to-line voltage magnitudes are all the same: = = =.
The normal technical term (in both British and International English) for an AC power socket is socket-outlet, [4] but in non-technical common use a number of other terms are used. In British English the general term is socket, but there are numerous common alternatives, including power point, [5] plug socket, [6] wall socket, [7] and wall plug ...