... priority switch 5. USB/SD card player 12" outdoor active subwoofer speaker box Portable PA System Features:1. USB/SD/MMC/MMS ... Woofer Frequency Band VHF 174-270MHzOutput Power 45Watts Function USB/SD/MMC/MMS card playerLine In/Out 6. ... Scope: *Room, outside(especially suitable dancing, gymnastics, demonstration's loud-speaker, recorded, play) *Teaching, Conference, classroom, military training, guide, ...