... 2.bulit-in amplifiler mp3 board 3.stable performance amplifier module--mp3 player boardFeature 1. control by MCU or pushbuttons 2 ... .play mp3 files selected by serial command 3.With play/pause, next, prev. vol-,Vol+ button ... / chime play mp3 music2. Graden , banks , schools , hosplitals , etc . mp3 module,mp3 player , embedded audio module , serial mp3 module