Data can be analog or digital. The term analog data refers to information that is continuous. Digital data take on discrete values. Like the data they represent, signals can be either analog or digital. An analog signal has infinitely many levels of intensity over a period of time. A digital signal, on the other hand, can have only a limited number of defined values. Although each value can be any number, it is often as simple as 1 and 0. at the physical layer.