As someone who was born in Poland but has lived their entire lives overseas, I found this video fascinating.  Great to see a novel approach to water quality and safety being implemented in real world use.,(reply>), I don't think it's very new, I've learned about it at school 15 years ago and it's been a thing for a while then,(reply>), I like how analouge it is, even the opening angles are on an osciliscope. These days it would be done with video and vision detection systems.