The SMi-35 mine, S-mine, or "Bouncing Betty" was an anti-personnel, bounding mine used by Germany during World War II. ==Description== S-Mine stood for Schrapnellmine which meant shrapnel mine in German. It could either be activated by a trip wire or by a pressure sensor at the top of the rod holding the three prongs. One of the notable features of the Bouncing Betty is that once activated, a black powder charge sends it flying up into the air until it reaches about waist height (2 feet, 0.6 meters), then it explodes sending all of the 350 steel balls placed inside of it flying everywhere covering a blast radius of about 149.9 meters maximum, though the effective blast radius was 20 meters The time it took for the mine to detonate the main charge was about 4 seconds.