1. Active speaker 2. Class AB amplifier 3. Rechargeable battery 4. Microphone priority ... SD MP3 Wireless Portable PA Speaker System AK12-203Portable PA System Features:1. USB/SD/MMC/MMS card player 2. Audio input/out put ( ... Scope: *Room, outside(especially suitable dancing, gymnastics, demonstration's loud-speaker, recorded, play) *Teaching, Conference, classroom, military training, guide, sales ...