All about metal detectors

I learned how metal detectors work.
back then people use metal detectors to find metal, coins, metal devices and
all sorts of things. in the olden days metal detectors were big they were heavy
and they were not working properly. The reason why soldiers use metal detectors
just to find bombs under the ground that people who  lives around the area is
very dangerous for them. Here is a presentation that i learned from it.