Difference and conversion between analog signal and digital signal
Different data must be converted into corresponding signals for transmission: analog data generally uses analog signals (Analog Signal), such as a series of continuously changing electromagnetic waves (such as electromagnetic waves in radio and TV broadcasting), or voltage signals (such as telephone transmission) Digital data is represented by a digital signal, such as a series of intermittently changing voltage pulses (for example, we can use a constant positive voltage to represent the binary number 1, and a constant negative voltage to represent the binary number 1). number 0), or light pulses. When an analog signal is represented by a continuously changing electromagnetic wave, the electromagnetic wave itself is both a signal carrier and a transmission medium; while when an analog signal is represented by a continuously changing signal voltage, it is generally transmitted through traditional analog signal transmission lines (such as the telephone network , cable television network) to transmit. When digital signals are represented by intermittently changing voltages or optical pulses, it is generally necessary to use twisted pairs, cables or optical fiber media to connect the two communication parties to transmit signals from one node to another.
2. Mutual conversion between analog signal and digital signal
Analog signals and digital signals can be converted to each other: analog signals are generally quantized into digital signals by PCM pulse code modulation (Pulse Code Modulation) method, that is, different amplitudes of the analog signal correspond to different binary values. For example, 8-bit encoding can be used. The analog signal is quantized into 2^8=256 orders of magnitude, and 24-bit or 30-bit encoding is often used in practice; the digital signal is generally converted into an analog signal by phase-shifting the carrier. Computers, computer local area networks and metropolitan area networks all use binary digital signals. Currently, what are actually transmitted in computer wide area networks are both binary digital signals and analog signals converted from digital signals. But the more promising application is the digital signal.