What Time Is It? History and Typology of Time Signals From the Telegraph to the Digital

Time signals provide a sense of “despatialized simultaneity,” a rhythm to the everyday lives of billions of people, and experiences of liveness. This article offers a history of time signals from the 19th to the 21st centuries, identifying three typologies: scheduled time signals, sent mainly by radio and TV; on-demand , such as those of the speaking clock; and automatized , transmitted by the Network Time Protocol for digital devices. The article stresses the importance of time signals in media history and the significance of an infrastructural network of timekeeping/timesharing for the functioning of media themselves.