... 1. Modify master code: first press "0 0" button, and then press the door inside the red button, "du" " ... , into the coding state, then input 1-eight new password, and then press "*" button, at hear "du", "du" sound, ... to complete.Second, open the door:Enter a new password and click "#" button, the correct password, buzzer "du" "du" ... battery,you can use emergency key to open. combination lock for safes