ISO And Digital Cameras?

I can understand how ISO works with film cameras. It requires a change of film, to one with larger silver-halide grains, to increase light sensitivity. But other than a dial change, what exactly does a digital camera do differently when you change the ISO setting to increase light sensitivity?

Same function as film - gets you faster shutter speeds.

I know how to use it and what it does for you. What I want to know is how it works, in a technical/scientific sense.

Basically it changes the voltage to the sensors, making them more or less sensitive to light - thus requiring more or less light. Of course, they were made to work on a certain voltage so they don't do quite as well at other voltages.

What changing the ISO in a digital camera does is to change the amplification that's used to process the signals of the image sensors. Higher ISO means more signal amplification is used. Since less light means less signal generated at the sensors, the signal needs to be amplified more to make the signal useable for creating an image. Increasing the amplification also increases the noise. And this is why there is more noise when shooting at higher ISO settings than when shooting at a lower ISO setting.

Thanks for the replies. That was exactly the kind of info for which I was asking.

PacAce nailed it.