USB PoweredThe alarm clock does not have a battery case so it does not utilize batteries,it can be only powered by the usb cord by connecting with the DC adaptor.The memory lithium button cell(CR2025) can be replaced,and it can keep the previous setting of the alarm, but not supply the power for the clock. 7 Adjustable brightness levels + 5 levels alarm volumeThe clock has 2 display modes that can show you time/date/month/year and temperature(C/F).L1~L7, all light 7 brightness levels to provide a full range brightness dimmer, meet your different demands, make it bright enough for the daytime and not too bright at night. You can choose a comfortable brightness for your eyes. Plus with 5 levels of alarm volume, it can be adjusted to your comfortable level. Perfect for heavy sleeper. SNOOZE Function For 9 Minutes Extra SleepPress the SNOOZE button after the wake-up alarm rings, you will enjoy extra 9-minutes sleep. The SNOOZE button is designed to be any buttons on the back, very easy to use. 9 minutes interval snooze can be repeated for 5 times until turning off. Press any buttons twice to turn off the alarm.Only with 3 buttons can anyone finish all settings of the travel alarm clock in just 1 minute. The user-friendly manual book also offers all operation details. And we provide warm and friendly customer service 24/7,and we provide worry-free 1 Year Replacement or Refund Warranty.