A communication channel is an integral part of each information transmission system . In the general case, this concept conceals a set of devices that are designed to provide signal transmission with certain properties from one point to another.
The communication channel contains such an important detail as the communication line through which the transmission of
electromagnetic waves directed from the transmitter to the receiver is carried out. What does it mean? One channel in the General case may contain a number of lines. You can say about the opposite moment. Typically, the same communication line is simultaneously included in a number of channels. But that's not all. In addition to the lines, equipment that is mounted at intermediate and final points is included in the channels. Depending on the task, the same devices can belong to different elements.
The classification of communication channels is carried out according to various criteria: the technical nature of the signals, the purpose of the system, the lines used, and other parameters.
There is another distinction. The communication channel can be analog or digital, and the creation of both is possible on the same communication line. Moreover, they function separately. This is implemented through several possibilities. In new systems, analog channels are actively being replaced by digital ones. But this is not a prerequisite. In the long-distance network, most of them along the entire length, as a rule, are analog, but there are also analog-digital ones. Therefore, in part, the signal will pass as analog, and in part as digital.
The formation of different channels on a pair of wires by signalmen has been going on since the twenties of the last century. One coaxial line can transmit up to 10,800 telephone channels, or a digital signal, the speed of which is 565 megabits per second. Here we should talk about the main difference between these concepts. It is impossible to say about the line that it has a certain throughput until it will be said about all the details of its construction, length, as well as the structural guide.
And in that case, if we consider the communication channel, all the characteristics are set. After all, they are usually standardized and described in great detail, and their type does not depend on anything at all. To a certain extent, the communication line is similar to the railway, and the channel in this case is comparable to a carriage with a clearly defined payload.
There is another concept. A dedicated communication channel is an element with a fixed bandwidth and bandwidth that constantly connects a pair of subscribers. Subscribers can be individual devices or entire networks. This type is usually rented from companies, and large corporations can build their own.
The communication channel can be analog or digital, and it is selected depending on what needs the subscriber is experiencing. In the case of a "dedicated" company focuses on a certain level of needs. Different lines are used to organize channels.