Last week, Apple surprise-launched its lineup of Smart Battery Cases for the iPhone 11, 11 Pro, and 11 Pro Max, and the cases have an intriguing new addition this year: a physical camera button. How the new button works was a bit of a mystery, as iPhones themselves don’t have a button dedicated entirely to being a camera shutter. But now we know a little more about the mechanism, thanks to an X-ray of one of the cases done by iFixit and Creative Electron.

If you look closely at the picture at the top of this post, you can see two thin circuits running down from the button toward the battery before they take a right turn to the circuit board, which connects to the Lightning port, which transmits data to and from the iPhone connected to the case. Presumably, when you push the button, those circuits are telling the circuit board to tell the iPhone to open up the camera app so you can snap photos. Here’s an even closer look:

Other cases offer dedicated camera buttons, like Moment’s Battery Photo Case, so if you don’t want to use an Apple case, you have options. But since Apple makes the phone that goes into the case, it can offer tighter integration between the two, like showing you the battery level of both the iPhone and the case in the battery widget, for example. And with that tight integration, there’s always the chance Apple will add more functionality into the shutter button in the future.

These X-rays also seem to rule out the possibility of the camera button coming to Apple’s non-battery cases for now, since those cases don’t have integrated circuit boards that could be used to relay a message from the shutter button.

Here’s the full X-ray of the Smart Battery Case, if you’re curious: