How exactly do digital piano's/Keyboards work?

Ahh,
http://www.qrsmusic.com/storyclark-p.asp?pg=1&cid=51&pid=3394

This is an optical sensing system, i.e. no bubble wrap touch film to worry about bursting or ripping (-:

Humm thats interesting :O

But i think that most digital pianos don't work that way seeing how they keep saying they're "state-of-the-art optical sensors that record every piano key motion with unparalleled accuracy and precision. "

"PNOscan MIDI record strip uses optic sensors, eliminating the concern among discriminating musicians that the mechanical interference of traditional recording strips "

I'm not sure if the recording strips are related to the key sensor or not, but it seems it's a expensive and rare technology, so probably not what most digital pianos have.. still great find!