Ramcent 3w White Desk Lamp With Usb CableTouch sensor switch is applied to this lamp, and it has 3-levels of different brightness, single touch gives lowest brightness, double touches medium and 3 touches the strongest. Adjustable brightness can meet various demands of different environment. After fully charged, the lamp will last 8 hours consecutively in the dimmest; 6 hours in medium light and 4 hours in brightest. The batteries are discharged when lamp is dimming it in time, lest it damage the performance of the batteries and reduce its lifetime. Thank you for choosing ramcent.