On A 3-way, there’s an additional terminal, called the “prevalent.” Power comes in to the switch about the widespread, then two “traveler” wires hook up the first switch to the second on the brass terminals. Using a screwdriver, cautiously remove the screws that keep the outdated plug alongside one another. https://smartpowerpoints87531.blogzet.com/top-guidelines-of-wiring-systems-49552937