Three-Way Switch
A switch pair controlling one light from two locations, like both ends of a hallway or stairs. The "three" counts terminals, not switches or locations.
Three-way circuits route power through traveler wires between the two switches, so either one can complete or break the path. Add a four-way switch between them and three or more locations can control the same light. The naming confuses everyone; the wiring confuses DIYers in practice, since a miswired three-way produces lights that only work when both switches are in lucky positions.
Three-ways matter today mostly through smart-home retrofits: smart switches need specific wiring (often a neutral in the box, and matched companion switches at other locations), and three-way boxes are where ambitious weekend projects stall. They are also a frequent flicker culprit: worn three-way contacts make lights blink as people use the other switch.
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- Receptacle (Outlet) : The device you plug into.
- GFCI (Ground Fault Circuit Interrupter) : The outlet with TEST and RESET buttons.
- NEMA 14-50 : The heavy 240-volt, 50-amp receptacle used for ranges, RV hookups and plug-in EV charging: four slots, rated for the most power a standard residential outlet delivers.
- Dedicated Circuit : A circuit serving exactly one appliance, with its own breaker and nothing else sharing the wire.