What is this little magnet for?

[lPHONE]

I have replaced many of LCD in PowerBooks and one of the things I noticed is after you remove the aluminum panel there's a little round magnet on the back of the LCD... What is this for?

I have also seem a handful of cases where pressure applied to the back panel has caused this magnet to crack the LCD.

 

[Intell]

It triggers the reed switch. The reed switch's job it to detect if the lid is open or closed.

 

[lPHONE]

It triggers the reed switch. The reed switch's job it to detect if the lid is open or closed.

How's that even possible? This is in the center of the LCD where no circuitry is even close. Unless the magnet goes through the LCD and the trackpad and the reed switch is underneath?

 

[Intell]

The switch is under the track pad. That little magnet is powerful enough to trigger the switch, even through the screen and track pad.

 

[Epsilon88]

That confused me too! Yep, it's the reed switch.