Gate Opening Sensor.
This is an electromagnetic sensor, which offers 'hands free' operation of the Mighty Mule Gate Opener with a 12 ft. radius of detection of vehicles in motion. GTO Exit Wand - 50 ft. With sensitivity Adjustment. (Not Compatible with Mighty Mule 250)

The exit wand is an electromagnetic sensor that detects metal mass in motion providing a 12 foot radius of detection that allows hands free exit from automatic gate operators. The sensitivity of the wand is adjustable for individual requirements. The GTO Exit Wand is designed for residential, agricultural and commercial applications and comes with various lengths. It is compatible with most automatic gate operators utilizing single and dual gates. The GTO Exit Wand has very low power consumption with a wide input voltage range that makes it ideal for battery applications. It is designed to reject line noise of 50 Hz or 60 Hz to improve its detection compatibilities near power lines.