Three Way Switch Definition March 4, 2019 Understanding Three. Three-way wall switches control a light fixture from two locations in a room. They are always installed in pairs and use special wiring connections. www.thespruce.com Thermostat Wiring InstructionsEscort Mk1 Wiring DiagramInstalling A 110v OutletFree Classic Car Wiring DiagramsInstalling A Relay SwitchHow To Wire A Light From An OutletHome Stat Thermostat ManualWiring Multiple Light Switches From One Power Source