The back of your Hello doorbell has a USB port, which often provokes questions. Unfortunately it's not to charge up your phone with! It's not even to transfer video files - since, of course, the Nest doesn't store video locally (it uploads all video to 'the cloud'). In actual fact, the USB port - which is micro USB - is used to quickly charge the small internal battery within the Hello. This shouldn't usually be needed because the hardwired connections will self charge this small battery, but in rare cases an issue can occur which requires you to dismount the Nest Hello and plug it in to charge it up and restore functionality. Nest's support team can also potentially use this USB port for debugging issues with your doorbell.