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 Wiring Plug Diagram30 Amp Receptacle BoxDifference Between 24vac And 24vdcReplace Old Honeywell ThermostatHoneywell 3 Way Valve Wiring Diagram8 Pole Switch2 Way Dimmer Switch Wiring DiagramBasic Electrical Switch