How do PDA/Nintendo DS Touchscreens work?

[Japlabot]

I've been wondering, how do PDA/Nintendo DS Touchscreens work? There is an LCD/TFT, but what is the technology used that turns that LCD/TFT into an input device too, what is this technology called?

Thanks,

QR

[tomfleet]

It's called a digitiser, a layer that sits on top of the screen. I think it works on resistance values accross the x-y axis, but check how stuff works, i'm probably wrong.

Tom

[Vice]

It uses sounds, each pixel on the screen is given a different sound (the sound is never played out loud) when you click the screen the cluster of pixels you have touched make a sound which the device processes into user input signals and refreshes the screen accordingly.

[YaKaLeDo]

http://electronics.howstuffworks.com/question716.htm

[tomfleet]

Seems like we are both right WinMacLin ;)