• induction loops. An induction loop is a coil of wire buried in the floor that creates a magnetic field. It senses the presence of steel. The loop must be selected for the mass of steel in the vehicle, and for the height of the steel chassis above the floor. Induction loops are perhaps the most common type of sensor used to open quick-acting doors for vehicles.
• ultrasonic motion detectors. Ultrasonic sensors are fairly reliable as long as the person or vehicle keeps