Computers are the foundation of the information age, but communication technology is the foundation of the foundation. Without the theories and practical applications of theory brought to us by the pioneers of communication, the computer age would perhaps have remained in the back office, hidden away as infrastructure like electricity or running water - critical to modern life, but not as transforming as the combination of communications and computing. The information age exploded once machines were endowed with the ability to talk among themselves. The Signal connects everything to everything else, in both communication, and in the metaphorical sense as the link between and among people.FeaturesIdentifies the key ideas underlying modern communications technology, and documents the contributions of its inventorsExplores the signal in communication, and also in the metaphorical sense as the link between and among peopleLeads the reader through a journey from ancient number systems to Voyager II to radio and MP3s to quantum cryptographyIncludes coverage of "e;Signals from Hell,"e; including memes and "e;fake news"e; on the InternetLooks to the future of communication, with emergent 5G