Voice Mini Portable Amplifier G228B CE,ROHS,ISO9001 Li-battery,With SD and USB Card,Echo ABS,it can work 8- ... 15hours continuely SD and USB Multifunctional Voice Mini Portable Amplifier with Echo Power:15W RMS/20W MaxFrequency response:100-15000HZ ... years (Li-ion battery), it can cover 500 square meters with proffional headset microphone.