The MagSafe magnetic charging circle on the back of the iPhone 12 has a hidden, secret function. In addition to charging the iPhone, it can also “reverse charge” other gadgets, charging them with its own battery.

Imagine plugging in your iPhone to charge using the standard Lightning cable, and placing your AirPods case on the back of the phone to charge both at the same time. This reverse-charging capability is built into the iPhone 12 you’re holding, according to Apple’s own FCC filings.

“In addition to being able to be charged by a desktop WPT charger (puck), 2020 iPhone models also support 360kHz WPT charging for charging accessories,” the introduction to an FCC filing reads. Then follows a rather confusing sentence that hints at Apple’s future plans: “Currently, the only accessory that can be charged by iPhones is a potential Apple [sic] third-party accessory in the future.”

The iPhone 12 has a magnetic ring on its back that can clip onto a variety of accessories. These include Apple's own magnetic puck charger, as well as Apple's line of iPhone 12 cases. These cases contain compatible magnets, but they also have an RFID chip built into them. This chip can be read by the iPhone. In this case, it tells the iPhone 12 the color of the case so it can change certain display elements to match.