mini speaker is used for mobile phone,computer,MP3/MP4player 1.Input:5.0V Output:3. ... :800ma Stereo Built-in mini speaker is used for mobile phone,computer,MP3/MP4player1.Input:5.0V Output:3.7V2.battery ... of "audio in" you can play music sources from mobile phone ,MP3,MP4 PC and toher audio devices.5.press the ... the control panel ,you can shift Udisk and SD/MMC card. mini speaker mobile phone speaker