We all know that the table saw is the widow maker of the tool world, ranking just above chainsaws and shapers. Using a table saw is like scratching a rabid Doberman behind the ears; you might be OK this time, but if you let your guard down for just an instant and become too comfortable, you're going to be missing a hand, an arm, or a face. The biggest risk is undoubtedly to the fingers, and when things go bad, they go bad fast. Human reflexes don’t even count when they go up against a table saw. But one company has created a saw that drastically reduces this risk.
The saw is called the Saw Stop, and on top of about a thousand other great features, it has a very unique safety system. The saw constantly reads a slight electrical charge that is carried in the blade, and when the charge is disrupted by, say, a thumb, the saw engages a brake and automatically lowers the blade. There is really no way to describe how fast this happens. The only thing you can do is watch.
The guys at Workbench have a longer movie that gets into greater detail if you're interested. It's really amazing.