Evolution through radio-circuits
This communication system was used in both World Wars.
The first receivers were asymptotic: every signal received by the antenna was transmitted and listened by all the people, this caused very few selective radio (one could not select a single channel excluding the others), but also very careful.
In 1864 Maxwell made important discoveries such as the laws of electromagnetic radiation reflection, that is, the laws governing the behavior of the waves, which were especially employed in the use of radar.
In 1883 Edilson invented the radio valves, or reaction radio that replaced galenic radios.
It exploits the property of free electrons: if it carries a piece of metal to incandescence, it emits free electrons, which to a high enough temperature exceed the potential barrier that keeps them in metal, a phenomenon called "thermionic emission" and discovered by Edilson.
..."I've been a bit in your story. Today I've been back to my story."...