The wiring diagram for a two-way switch starts at the power source and ends at the light bulb. It shows the black hot wire feeding from the switch to the housing where the bulb is attached. A white neutral wire from the power source is shown running parallel to the hot wire, bypassing the switch and intersecting with itself to complete the circuit. Copper ground wires are attached to both the switch and the light bulb housing.
Two-way switches supply power to a load. Loads can be light bulbs, outlets, ceiling fans and lamps. Power is drawn from the power source and delivered to its destination when the switch is turned on. The power is delivered through a hot wire that is bundled with neutral and ground wires in a three-wire cable called a romex.
Copper ground wires are connected to the switch via a green screw. Three ground wires are required. The incoming ground wire stems from the power source. The load ground wire runs to the destination being supplied with power. The switch ground is attached to the switch.
Basic two-way switches can be modified by reversing the load and the switch. In the case of a light bulb, the power supply feeds directly into the house for the bulb, and then run to the switch. Two-way switches can also be daisy chained to supply power to separate loads.