Analog Signals and Digital Signals

A signal is any time-varying physical quantity—voltage, light beam, sound wave, or other—that is used to convey information. Analog signals convey information by analogy (i.e., by mimicking the behavior of some other quantity). Digital signals convey information by assuming a series of distinct states symbolizing numbers (digits). Both analog and digital signals are essential to modern communications and computing, but the greater simplicity and generality of digital signaling has encouraged an increasing reliance on digital devices in recent decades.