The three basic elements that must be present in a communication system are the

The three basic elements that a communication system must have are a source, a communication medium, and a host.

Communication system is a general term for a technical system that accomplishes the process of transferring information. The easiest communication system is for users at two points to send and receive information to and from each other. Within a general communications system, users can communicate with other users within the system via switching equipment.

Communication system is composed of three parts: sender (source and sending equipment), channel receiving equipment (host and receiving equipment), noise source; source that is, the source of information, the channel is the transmission medium for transmitting signals, the source of noise is the channel noise as well as dispersed in the communication system elsewhere in the concentration of the noise performance.

The source, the source of information, serves to convert the original signal into the corresponding electrical signal, the baseband signal. The function of the transmitting device is to perform various transformations and processes on the baseband signal, such as amplification and modulation.

The channel is the transmission medium for transmitting the signal, and the host is the receiver of the information, corresponding to the source. The function of the receiving device is the opposite of that of the transmitting device, processing and transforming the received signal. A noise source is the concentrated manifestation of the noise in the channel and the noise dispersed throughout the rest of the communication system.

Communication systems can be divided into two categories according to the different transmission media used:

①The use of metal conductors for the transmission medium, such as commonly used communication cables, etc., this cable for the transmission medium of the communication system is called wired electrical communication system.

②The use of radio waves in the atmosphere, space, water or rock, earth and other transmission media for communication, this communication system is called radio communication system. Optical communication systems also have "wired" and "wireless" points, they use the transmission medium for optical fibers and the atmosphere, space or water.