BATTERY BACKUP - Outlet powered, but you have the option to back it up with 3 AAA batteries (NOT included) in case of power outage. Not only time and settings are restored, alarm are also supported (USB will not charge). Please be noted that the clock may drain batteries fast, so ONLY use as a backup but NOT everyday operation. Integrated USB port charges your compatible smartphone while you sleep. Start your fresh day with a fully-charged phone. Easy-to-use digital alarm clock. Easy snooze with a simple press of the top button and experience zero stress when setting the time or alarm. Pick your favorite sound among the 5 alarm sound options(Beep/Buzzer/Bird Sound/Piano Music/Soft Music), and wake up to adjustable alarm volume from 30-90db. Small footprint(5.9"x3.11"x1.65") with big white LED numbers easy to read day or night, and display brightness can be easily adjusted from 0 to 100%, depending on personal preference. 12 or 24 hour time display optional.