portable audio system designed for ipod/iphone (1)Output:Rms 4W(3W*2) Stereo(2)Sound respond frequency:150-18000HZ(±3dB)(3)Input Power: DC 5V/1000MAFunction:Recharge: 4 AAA batteries, DC5V/1000mA Power Adapter, or USB5V computer source power.Can link to SD,MP3, MP4, Notebook, CD, DVD, Iphone mobile, IPOD (nano4),Iphone 3G.can be charged when playing by plug in straightly.