In 1993, federal law required all garage doors to have this feature after multiple child deaths. Test every month by placing a 2×4 on the ground where the door would close. It should reverse after a second or so when the door hits the wood. Also test the photo-electric sensors if you have them by placing something in front of them (not your body). If the door doesn’t immediately go back up, you have a problem. All garage door openers have a pressure relief setting. Adjust the setting and run through the test again.