Kindle Cover - How Does it Work?

I have a plain old Kindle with “special offers” (ads) on it. I also bought a cover for it. If the Kindle’s screen is turned off, when I close and open the cover it goes to “special offers” mode, with the option to slide my finger on the screen to unlock it and turn it back on to reading mode. When it’s in “special offers mode” and I close and open the cover, it also recognizes that something has happened because it once again gives the option to slide my finger on the screen to unlock it.

There is only one button, and the cover doesn’t touch that button. So how does the Kindle know I closed the cover? Is it some trick with the touch screen? If so, I can’t duplicate it with anything other than the cover.

There’s a magnet in the cover (and a sensor in the kindle.)

I assume it’s similar to the iPad method, which uses a small magnet in the cover to trigger a sensor in the edge of the device.

Edit - ninja’ed!

Ah, thanks. I knew it would be a simple answer. Well, that was my post for the year. Back to my hole for a few months…