There is some new saftey technology out that you simply have to see to believe. SawStop Technology monitors the electical conductivity of the the saw blade to by extension determin the electical conductivity of the material being cut through. So what you say? It allows this device to tell the difference between something like oh say wood and your shop teachers fingers. SawStop can make this distinction and stop the blade in 0.005 seconds. Which sounds fast but you have to SEE it to understand how fast.
They have some excellent videos on their site which perilously place a hot dog in harms way to show off the speed of their response. The difference? A small nic and a bandaid or a swift cut and the ability to scare small children for a lifetime with your nub. The video with the table saw is the best as it has to overcome additional obsticales not inherent in the other saws. IE The momentum of the blade and the fact that the wood “drive mechanism” is trying lop its finger off.