AM-FM vs telegraphy

AM-FM

telegraphy

noun
  • The devices and networks used to enact this process. 

  • Any process for transmitting arbitrarily long messages over a long distance using a code, especially by means of electrified wires or radio waves using Morse code. 

  • The science and techniques used to enact this process. 

How often have the words AM-FM and telegraphy occurred in a corpus of books? (source: Google Ngram Viewer )