signal
A signal is the representation of information. It is characterized by the amplitude value or value progression of a physical quantity over a time 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 value and time continuous function is called analog signal. If, on the other hand, the signal consists only of characters, each character corresponding to a specific value range of the signal parameter, then it is called a digital signal.