Newonline Waistband Tour Teacher Voice Amplifier Portable Microphone Speaker N74U Digital circuitry technology, 15W output power LOW-THD AT Adaptive Technology features low distortion even at high output power Built-in intelligent recharging management system for secure battery charging and discharging, fast charging and long play time (continuously work for 8-15 hours. ) Built-in high capacity rechargeable lithium-ion battery Music play function supports multimedia audio file play of USB and TF card