or another physical quantity. According to the German Institute for Standardization e.V. (DIN), a signal is understood to be the physical representation of messages or data
. A signal whose signal parameter represents a message consisting only of continuous-value and continuous-time functions is called an analog signal. If, on the other hand, the signal consists only of characters, with each character corresponding to a specific value range of the signal parameter, then it is referred to as a digital signal.