Four-way switches are used to control lighting from three or more locations. Four-way switches are used in combination with three-way switches. There are four terminals that provide two sets of toggle positions on a four-way switch. Each set of terminals is one of the toggle positions. When the switch is in the up position, the current can flow through two terminals. In the down position, the current flows through the other two terminals. Many times, four-way switches will come with two brass colored terminal screws and two darker colored terminal screws. A green ground terminal is also on a four-way switch.
To find out which terminals go together, you can use an ohm meter to test the terminals and the toggle positions. Each set of terminals will connect to the traveler wires from each of the three-way switches. When connected properly, you’ll be able to turn lights on from either of the three-way switches or the four-way switch. And just in the event you need to switch lighting from more than three locations, simply add additional four-way switches between the two three-way switches.