13. Enemy Aircraft Listener (Before Radars)
If you had good hearing, you wouldn’t have struggled to find a job at top secret military bases all over the world. Before radars became mainstream, militaries used acoustic mirrors and other listening devices to detect enemy aircrafts. Acoustic mirrors were very accurate and could pin point the location of enemy aircrafts.
The British used acoustic mirrors much more efficiently than the rest of the world. The mirrors were invented by British scientists led by Dr William Sansome Tucker. However, after 1930s, the aircrafts evolved to ground breaking speeds. This dropped the accuracy of acoustic mirrors to a compromising extent. This lead to invention of radars and acoustic mirrors and the listeners became obsolete.