The chick safe units both feature an auto stop if a chicken is obstructing the door. They also automatically detect when the door is open and when it is closed so there is no calibrating. Every part of the ChickSafe coop door is designed with long life and weather resistance. The chicks safe eco PC-400 operates on a photo sensor only meaning it will detect the light and open or detect the dark and close. Takes 4 AA batteries that are not included.