1,Built-in Class D power amplifier ,which means the unit has automatic battery saving,pure and exquisite timbre ,and can up to 18 hours of use 4*AA batteries. 2)Electronic volume control avoids the signal interference and wastage which is from the mechanical friction,which lets Audio player palyback be more clear and exquisite. 3,The speaker is used high efficiency,internal magnet ,double rubidium ,iron born as the magnet circuit system, the magnet density reaches as high as 12000GS,completely improve the speaker's sensitivity,you can put the units alongside computer or TV,there is no interference to them 4.The stylish appearance design, and it can work with iPod Nano ,iPod Photo,iPod Video and charge your iPod at the same time. ,and also fits MP3,CD,MD, PC or any units ,which has audio output.