... card and USB port Built in double 2000mah lithium battery The specification and feature of voice amplifier is as ... , pause/play buttons.9.Built in double 2000mah lithium battery to ensure strong power running abilitySpecification: 1.Support TF ... ratio:≥80dB9. Recharging :DC 9V 10.Working voltage:7.4V.11.Battery capacity:2000mAApplication: Teaching, sales promotion, morning exercise, entertainment, ...