F.M. is now everywhere, developed largely by one man. Colonel Edwin Armstrong, the father of modern radio, and the creator of the first F.M. system, had committed suicide. Before that he played a crucial role in communications during the First World War. He believed, rightly so, that F.M. was a revolutionary operating system and that it should replace A.M. equipment for broadcasting. Tired and despondent after fighting one lawsuit after another against RCA and others, his personal fortune spent on promoting and defending F.M., Armstrong finally gave up.
Every modern radio has circuits Armstrong designed.
And you thought modulation was boring. . . Frequency shift keying, an F.M. variation Conventional cellular makes much use of frequency shift keying modulation to send signaling and control messages. It's old technology, in fact, the earliest modems were built with this technique, but FSK works well for what it does. To explain its title, FSK means sending data by slightly shifting frequencies. Keying, by the way, simply means forming or creating a signal.