The Dillon Low Powder Sensor is a warning system that provides an audible and visual reminder when it's time to refill your powder reservoir. A buzzer will sound and a bright LED will light when the powder level drops to about 1000 grains.
The added weight of the system helps keep powder charges more consistent, especially as the level drops in the hopper. Dillon's safety sensors are for when something goes wrong and you're distracted, or not concentrating.