Great Advances

Wars, as usual, are responsible for many technical advances. Among the most significant was the invention of new devices capable of producing higher frequencies which were to be called microwaves. This made possible the emergence of radar both for military and civil communications and sometime later Long Distance Communications was realized by microwave links where information was sent from tower to tower. Microwave networks were built in all industrialized countries. It was followed by satellite communications, first passive (relying on signal reflection) and later active, that re-radiated signal. The first mobile phones also used microwave frequencies. Further advances like digitalization, optical fibres, and inter-computer communications are introduced.