Energy-saving:Why does the Led clock automatically dim from 10 p.m. to 6 a.m. the next day? For better sleep, For Led Service Longer, For more energy-saving. You can use the remote control to manually adjust the brightness of the clock at any time other than the above time period. LED ELECTRONIC CLOCK : Adjustable Brightness with 3 intensity levels to accommodate different needs, you can turn off the nightlight when you go to sleep.(The clock will keep working) the clock is powered by USB cable only DESK OR WALL MOUNT CLOCK: it has notches on the back for mounting, stand is removable, can be easily hung on the wall as a wall clock, or place it on the desktop arbitrarily.Can be used as a Alarm Clock with waking up; The 3D Led Clock get 12/24 hour display mode. Size:"A" means the clock is white backgroud,and "B"means the clock is black backgroud.