Here, we will mainly introduce the definition and classification of transmission data.
What exactly is data transmission?
It refers to the process of transmitting data between a data source and a data sink in accordance with appropriate procedures through one or more links. It also refers to the operation of sending data from one place to another with the help of signals on the channel.
It is the communication process of transmitting data from one place to another. The data transmission system usually consists of a transmission channel and data circuit termination equipment at both ends of the channel. In some cases, it also includes multiplexing equipment at both ends of the channel.
The transmission channel can be a dedicated communication channel. It can also be provided by a data exchange network, a telephone exchange network or other types of switching networks.
The input and output devices of the data transmission system are terminals or computers, collectively referred to as data terminal equipment. The data information it sends is generally a combination of letters, numbers and symbols. In order to transmit this information, each letter, number or symbol needs to be represented by a binary code.
Commonly used binary codes include International Number 5, EBCDIC code, International Telegraph Number 2 and Chinese Character Information Exchange Code.

Data transmission classification
①Baseband transmission refers to the transmission method in which the binary "1" or "0" electrical signal sent by the data terminal equipment is directly sent to the circuit. The baseband signal is not modulated and can be directly transmitted after being driven by code conversion.
The characteristics of the baseband signal are that the spectrum contains DC, low-frequency and high-frequency components. As the frequency increases, its amplitude decreases accordingly and finally tends to zero. Baseband transmission is mostly used in short-distance data transmission.
②Most transmission channels are bandpass characteristics, and baseband signals cannot pass through. The modulation method is used to modulate the baseband signal to the channel bandwidth for transmission.
The method in which the receiving end restores the baseband signal through the demodulation method is called band transmission. This method can realize long-distance data communication.
③Digital data transmission is a method of transmitting data signals using digital voice channels.
Folded parallel transmission
Parallel transmission is a method in which the binary codes that constitute characters are transmitted simultaneously on parallel channels.
Folded serial transmission
Serial transmission is a method in which the binary codes that constitute characters are transmitted bit by bit in a channel in time sequence in units of bits.
Although the speed is slow, only one transmission channel is needed, the investment is small, and it is easy to implement. This is the main transmission method used for data transmission. It is also a main method adopted by computer communication.
Folding asynchronous transmission
Asynchronous transmission is a method of character synchronous transmission, also known as start-stop synchronization. This method is simple, and the clock signals of the receiving and sending parties do not need to be accurately synchronized. The disadvantage is that the start and stop signals are added, the efficiency is low, and it is used in low-speed data transmission.
Folding synchronous transmission
Synchronous transmission is a bit (code element) synchronous transmission method. This method must establish accurate bit timing signals on both the receiving and sending parties in order to correctly distinguish each bit of data signal.
Folding simplex transmission
Simple transmission means that data can only be sent and received in a single direction. Half-duplex transmission means that data can be transmitted in two directions but not at the same time.
Full-duplex transmission means that data can be transmitted in two directions at the same time, that is, receiving and sending at the same time.
Generally, four-wire lines are full-duplex data transmission, and two-wire lines can achieve full-duplex data transmission.
The above is an introduction to the classification of data transmission.