How does a door switch work?

A door switch operates through a simple electromechanical or magnetic mechanism that opens or closes an electrical circuit in response to physical movement. A mechanical door jamb switch utilizes a spring-loaded plunger mounted in the door frame. When the door closes, it presses against the plunger, pushing it inward and physically separating internal metal contacts to break the electrical current, turning off the connected light. When the door opens, the spring pushes the plunger outward, forcing the contacts together to complete the circuit and turn the light on. Similarly, magnetic security door switches utilize a permanent magnet and a reed switch; when separated, the magnetic field drops, altering the circuit state.

A door switch operates as a simple electromechanical or magnetic interlock device designed to detect the physical position of a door, lid, or access panel. Mechanical door switches feature a spring-loaded plunger button that is physically depressed when the door is closed, holding the internal electrical contacts open or closed to control a circuit. When the door opens, the spring releases the plunger, altering the circuit state to turn on a light, trigger an alarm, or cut off power for safety. Magnetic door switches rely on a stationary reed switch and a moving permanent magnet; when the door closes and brings the magnet close to the sensor, the magnetic field pulls the contacts together. You can verify proper operation by testing electrical continuity with a digital multimeter while manually depressing the actuator.