The combination of all technical equipment and transmission media required to achieve information transmission is called a communication system.

Source: The origin of a message, which converts various messages into original electrical signals, known as message signals or baseband signals. Telephone sets, television cameras, telexes, computers, and other digital terminal devices are the sources of information.

Sending device: Matches the source and channel, transforming the message signal generated by the source into a suitable situation for moving in the channel. Modulation is the most common transformation method. Modulation is the most common transformation method for situations where spectrum shifting is required. For digital communication systems, sending devices are often divided into source encoding and channel encoding.

Channel: The physical medium through which signals are transmitted.

Noise source: It is inherent in various devices and channels in communication systems. For the convenience of analysis, the noise source is abstractly added to the channel as a concentrated representation of various noise sources.

Receiving device: completes the inverse transformation of the transmitting device, i.e. performs demodulation, decoding, decoding, and so on. Its task is to correctly recover the corresponding original baseband signal from the received signal with interference.

Beacon: The destination point for transmitting information, whose function is to convert the restored original signal into corresponding information