As long ago as the early 70s, the Bureau of Mines was developing
magnetic induction communication devices for locating and
communicating with trapped miners. They worked just like our "cave
radios," except that they got extremely long range by having very
large underground antennas, like wires wrapped around a mine pillar.
Leveling wasn't critical, because precise location not needed, there
presumably being a good survey of the mine available. The idea was
just to see that someone was alive and trapped in a certain area of
the mine. Not sure what ever became of that idea. I have a bunch of
government publications on the subject from those days because of my
interest in cave radios.
--Mixon
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I am walking down the street with Leonardo di Vinci. He says, "It is
indeed wonderful what your science has created. You must explain to me
how everything works." That's when I wake up.
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