When the load is controlled from only two points, Single Pole, Double Throw (SPDT) switches are used.
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While a "normal" light switch needs to be only a Single Pole, Single Throw (SPST) switch, multiway switching requires the use of switches that have one or more additional contacts and two or more wires must be run between the switches.
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Electrically, a "3-way" switch is a Single-Pole, Double-Throw (SPDT) switch.
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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.
Switching Goals | Multiprotocol Label Switching | Electronic Switching System | Electronic switching system | Markov switching multifractal | Energy switching services in the UK | Double switching |