... : DC 5V 3.7V-Li battery with 2000mAhSpeaker : 3-inch 4Ω with high quality magnet Color : Yellow/Black/ ... 5-10mVFM Frequency:FM87.5 – 108 MHzFunction: MP3/audio playback Headset microphone USB/SD card FM RadioComponents: USB ... Li-ion battery (built-in)Keyword: Portable Teaching Amplifier, Portable Amplifier, Teaching Amplifier, Voice Amplifier, Portable Teaching Amplifier 2012 Audio Amplifier