50 Ft. Driveway Vehicle Sensor (FM138) for Mighty Mule Automatic Gate Opener The 50 ft. Driveway Vehicle Sensor (FM138) allows a vehicle to drive past the sensor's 12 ft. magnetic field and will open your gate automatically, allowing guests the ability to exit without a Remote (FM135). Works with single and dual gates. Easy DIY (Do It Yourself) installation. Can be installed 3-50 ft. away from the gate. Also available are longer lengths including 100 ft. Vehicle Sensor (FM140) and 150 ft. Driveway Vehicle Sensor (FM141). Mighty Mule Wireless Driveway Vehicle Sensor (FM130) also available for wireless installation. Backed by a 12 month Mighty Mule Warranty and Technical Support.