The name of Claude Elwood Shannon is not a completely strange to Communication researchers. However, part of its importance to the history of communication in the XXth century is not well known. His master’s dissertation and the derived paper (A Symbolic Analysis of Relay and Switching Circuits) were essentials to the transformation of computers into communication machines and, consequently, penetration in our society as happens today. This paper revises the first great work of Shannon and explains its participation in the present context of communication.