Codes can be consisted by a 1-15 digits, billions of combinations available Codes can be set and changed by users, and memorized automatically when power off forever Easy operation and more security You can apply for management codes when you forget your own individual codes, press back button to restore factory setting Emergency battery can be applied when battery is out of power Auto-alarm will be activated when input wrong codes 4 times Energy-saving design, 4 pieces AA batteries can be used for one year, automatic power shortage prompts