As aforementioned in the introduction of chapter 8, communication
is the workhorse of armies and armed forces. Without a doubt
the precise monitoring and evaluation of signals were possible
only after the advancements in electronics, which took place
back in the firsts years of the XX century and, certainly
it was responsible for inspiring the procedures of the modern
In this way due to the readiness arisen by the electronic
technology, in the several communications modes: continuous
wave, phony, facsimile, pulse and so forth, those types of
signals could be monitored, analyzed and then duly encoded
to become unknown to the enemy.
During WWII, in the countries
in conflict the radio waves were daily monitored by using
radiogoniometry procedures in order to locate several
modes of clandestine transmissions. Due to the lack of
trained operators generally radio amateurs conducted this
Photograph by Hallicrafter.
Mobile radio monitoring
of clandestine transmissions, circa 1944.