A simple three-way switch has one common screw terminal and two traveler screw terminals. The color and position of the terminals varies from one manufacturer to another. A three-way switch also has an extra screw for the ground wire, which is almost always in a different color than the other screws.
A simple three-way switch allows individuals to control a light from two locations, such as either end of a hallway or the top and bottom of a stair. Toggling this type of switch disconnects one of the traveler terminal to connect the other.
The traveler screws are generally the same color for easy identification. Their function is to carry the electrical power from one switch to another. Unlike other types of switches, simple three-way switches do not have "On" and "Off" markings, because either of them controls the same light. When wiring a three-way switch, the lightbox always needs a neutral, and the traveler terminals connect at each switchbox. If the switches are connected directly, a 2 conductor cable is required between one of the switches and the light. Wireless signaling techniques and power line signaling are available for the implementation of modern three-way switches for easier control and safety.