(The independent variable takes discrete values, and the parameter takes a finite number of discrete values ??through quantization, which is called a digital signal. A digital signal in practical use is usually a sequence of only two pulses with the values ??"0" and "1". The essential difference between an analog signal and a digital signal is that an analog signal can take an infinite number of values, while a digital signal can take a finite number of values, usually only two values ??of "0" and "1".)