When the load is controlled from only two points, single pole, double throw SPDT switches are used. The bare copper wires tie together with a wire nut. By correctly connecting two of these switches together, toggling either switch changes the state of the load from off to on, or vice versa. 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. The diagram below will give you a better understanding how this circuit is wired. A phenomenal effort on your part! When used in combination with another type of switch—the four-way switch—you can arrange switches to control light fixtures from three or more locations.
Electrically, a typical "3-way" switch is a single pole, double throw SPDT switch.
3 Way Switch Wiring Diagram
There are three screw terminals on the body of the switch, in addition to the green grounding screw. An optional master control can be added that turns all lights in the facility on or off simultaneously under the control of a timer or computer. At each end of a hallway. No longer allowed after NEC if no neutral wire in switch boxes 3- Way Switch Wiring Diagram Light Fixture Between Switches Line voltage enters the first 3- way switch outlet box, light fixture is located between switch boxes. Just that 3 way switches are a pain in the neck, especially when someone pre-wired but did no finish work, dry wall was installed and the electrician never came back, leaving this owner to hunt down every power leg and determine where every run went.