There are a few different ways that automatic gates work. The most common type of gate uses an infrared beam that crosses the entrance to the gate. When a car or person breaks the beam, the gate opens. Another type of gate uses loops in the ground that create an electric current when a car or person drives over them. The current triggers a switch that opens the gate. A third type of gate uses sensors on either side of the entrance that sense when something is coming close. When something comes close, it sends a signal to open the gate.