![]() ![]() This switch has two pairs of "traveler" terminals that it connects either straight through, or crossed over (transposed, or swapped). Ī "4-way" (intermediate) switch is a purpose built double pole, double throw (DPDT) switch, internally wired in manufacture to reverse the connections between the input and output and having only four external terminals. The switches may be arranged so that they are in the same orientation for off, and contrasting orientations for on. By correctly connecting two of these switches together, toggling either switch changes the state of the load from off to on, or vice versa. Toggling the switch disconnects one "traveler" terminal and connects the other.Įlectrically, a typical "3-way" switch is a single pole, double throw (SPDT) switch. ![]() These switches appear externally similar to single pole, single throw (SPST) switches, but have extra connections which allow a circuit to be controlled from multiple locations. Three-way and four-way switches make it possible to control a light from multiple locations, such as the top and bottom of a stairway, either end of a long hallway, or multiple doorways into a large room. The electrical load may be permanently hard-wired, or plugged into a switched receptacle. The controlled load is often a lamp, but multiway switching is used to control other electrical loads, such as an electrical outlet, fans, pumps, heaters or other appliances. Readers in most other countries should read "two-way" or "SPDT" for the United States "three-way" and "intermediate", "crossover" or "DPDT" switch for the United States "four-way". This article follows usage in the United States. Three-way and four-way switches A double pole, double throw switch wired to act as a four-way (intermediate or crossover) switch In alternative designs, low-voltage relay or electronic controls can be used to switch electrical loads, sometimes without the extra power wires. Double pole, double throw (DPDT) switches allow control from three or more locations. When the load is controlled from only two points, single pole, double throw (SPDT) switches are used. In contrast to a simple light switch, which is a single pole, single throw (SPST) switch, multiway switching uses switches with one or more additional contacts and two or more wires are run between the switches. 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. In building wiring, multiway switching is the interconnection of two or more electrical switches to control an electrical load from more than one location.
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