Are there other tools that detect fingers and stop heavy machinery instantly? Did they exist prior to sawstop? Just because someone can guess how an invention w

Are there other tools that detect fingers and stop heavy machinery instantly? Did they exist prior to sawstop? Just because someone can guess how an invention works doesn't mean it was obvious, you've also got the benefit of being told of the idea in the first place. It's an invention that saves over ten life-changing injuries a day, if it was so inherently obvious, why did no-one else think of it before? So many comments on here seem to focus on the electrical side of the patent, yet it's only part of the invention. There's also the non-trivial discovery of how to safely stop the fast spinning blade instantly.