First it comes with a built-in micro USB adapter, so you only need to device itself to charge your handset. But if your device doesn't charge through micro USB you can still use your own cable and plug it into the standard USB adapter. Actually you can charge two devices simultaneously, using the micro USB cable and the standard USB adapter. It's very easy to use it: simply plug the micro USB cable (or your own cable) and press the button. Four LEDs will indicate the current battery level available to recharge your handset. You can also quickly check how much power is available even if it is not plugged by simply pushing the button and looking at how many LEDs light up. With a 1420 mAh battery you won't get quite a full recharge for your device, and this will depend on how much power your device

Source: Geekzone