1. Analog Signals
The advantages of analog signals are intuitive and easy to implement, but there are two main disadvantages.First of all, it has a poor confidentiality considering analog signals, especially microwave and wired open-line communications, can be easily eavesdropped. As soon as an analog signal is received, it is easy to obtain the content of the communication.
The next deficiency about analog signal is its weakness in anti-interference. During the transmission of the electrical signal, it is subjected to external and internal noise interference within the communication system, which makes it difficult to separate the noise from the signal, thus degrading the communication quality. The longer the line, the more noise accumulates.
2. Digital Signals
Advantages of digital transmission
First of all, digital signal has a better confidentiality than analog signal. And digital signal improves anti-interference capability that can be mixed with noise during transmission, and the input signal voltage can be measured using the threshold voltage (called the threshold value) constituted by the electronic circuit. At last, an integrated digital communication network can be constructed. With time-division switching, transmission and switching are unified to form an integrated digital communication network.
Disadvantages of digital signals
Occupies a wider frequency band. Because the line is transmitting a pulse signal, the transmission of digital voice information all the way to occupy 64kHz bandwidth, while an analog channel occupies only 4kHz bandwidth, that is, the PCM signal all the way to occupy several analog channels. This means that a PCM signal takes up several analog channels. For a given channel, its utilization is reduced, or its requirements on the line are increased.
Then, the technical requirements are complex, especially the synchronization technique, which requires high accuracy. In order for the receiver to understand the sender correctly, it must correctly distinguish each code element and find the beginning of each message group. This requires strict synchronization between the transmitter and the receiver, which is more difficult to solve if a digital network is formed. With the use of large-scale integrated circuits and the popularity of broadband transmission media such as optical fiber, the storage and transmission of information is increasingly using digital signals, so the analog signal must be converted to analog/digital, which will inevitably lead to quantization errors in the conversion.
Specifically, digital signals have the following advantages: "First, the anti-interference ability is stronger, the quality of the transmitted signal is higher, the second is the high-definition image, the effect of sound conversion is good. The third is the more efficient use of channel resources, which can transmit hundreds of programs, while in the analog TV signal, only dozens of programs can be transmitted.