Special Device Used by the Dutch Army to Identify Approaching Enemy Airplanes, 1919
When you first look at this device, it sure looks like a prop out of a Charlie Chaplin movie, but in reality, it is a highly complicated acoustic listening device. Back in the days where Radar was found only in science fiction magazines, the Dutch army had to invent a device that would help their troops discover approaching enemy airplanes.
This device proved to be highly effective, and it used the Dutch army for over 25 years. Once Radar was finally discovered, this machine became one of the most popular attractions at kids’ playgrounds all over the country.