Wechselschalter

A Wechselschalter, also known as a two-way switch or changeover switch in English-speaking contexts, is an electrical switch used to control a single light fixture or appliance from two different locations. This is commonly found in situations such as staircases, hallways, or large rooms where having a switch at both ends or entrances is convenient. The operation of a Wechselschalter relies on redirecting the flow of electricity through two possible paths.

Internally, a Wechselschalter has three terminals. One terminal is the common input for the power supply. The other two terminals are connected to the output wires that lead to the controlled device. When the switch is in one position, it connects the common terminal to one of the output terminals, completing the circuit and turning the device on. Flipping the switch to the other position disconnects the common terminal from the first output and connects it to the second output terminal. This action either turns the device off or, if another Wechselschalter is controlling the same device, turns it on by completing the circuit through the second switch's path.

The key principle is that the circuit is only complete when both switches are in a complementary state. For example, if the first switch is feeding power to output A, the second switch must also be set to receive power from input A to illuminate the light. If either switch is in the opposite position, the circuit is broken. This allows for independent control from multiple points without needing to return to the original switch.