I've recently bought a magnetic cover for my tablet (a bamboo smart cover for Asus Transformer Pad TF303CL). What puzzles me is that whenever I open the cover, the screen turns on. How does the tablet know when I open the cover?

The cover isn't connected in any way to the tablet, AFAIK. The only way that I could think of is if the tablet is using the light sensor, but then why doesn't it turn on the screen when I use my finger to cover the sensor? Or when I turn the light off and then on again?

  • Also, related: android.stackexchange.com/questions/64721/…
    – Andrew T.
    Commented Mar 10, 2015 at 9:50
  • @AndrewT. The questions are related but not exact duplicates. Before reading the answer I didn't know the tablet had a magnetic sensor (or other kind of sensors) at all, while that question is all about how that sensor work (given that it exists).
    – Bakuriu
    Commented Mar 10, 2015 at 12:41
  • No worries, it is just for a general pointer for devices that support this. I don't know if there are other method, but most of them are using magnet, albeit might have different position on each model.
    – Andrew T.
    Commented Mar 10, 2015 at 12:45

1 Answer 1


Your device will have a little magnetic sensor hidden under the display that can trigger the display to turn on.

A small magnet lies embedded directly under the surface of the smart cover and lines up with the corresponding spot on the device. The device detects the removal of this magnet when opening the cover and turns the screen on, and can also put the device into sleep mode when the cover closes.

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