Nubia NX521J User Manual page 11

Home key
Press the key to return to the home screen from any other interface.
Press & hold the key to open the list of most recently used applications.
Menu key
Press the key to open the tools menu of current interface.
After Free Screenshot is enabled, press & hold the key to enter the Free
Screenshot mode.
Back key
Press the key to return to the previous menu.
Volume key
Press the key to adjust the volume. Press & hold the upper key to adjust to
maximum volume, and press & hold the lower key to adjust to Vibration.
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