Today, information is spreading so quickly that there is not always enough time to comprehend it. Most people rarely think about how and by what means it is transmitted, and even more so do not imagine the scheme of information transfer.
Basic concepts
The transfer of information is considered to be the physical process of moving data (signs and symbols) in space. From the point of view of information technology, the data transfer process is a pre-planned, technically equipped event for moving information units in a specified time from the so-called source to the receiver through the information channel, or data transmission channel.
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Directly to technical data transmission channels include radio channels, fiber optic channels and cable. The cable can be coaxial or twisted pair. The first are an electric cable with a copper wire inside, and the second are twisted pairs of copper wires, insulated in pairs, located in a dielectric sheath. These cables are quite flexible and easy to use. Fiber optic consists of fiber optic fibers transmitting light signals through reflection.
The main characteristics of communication channels are bandwidth and noise immunity. By bandwidth, it is customary to understand the amount of information that can be transmitted over the channel for a certain time. A noise immunity is a parameter of the channel resistance to external noise (noise)., , : «», «» « ».
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Understanding this scheme is easy. Especially if you imagine its elements in the form of familiar objects and phenomena. For example, the source of information is a person talking on the phone. The handset will be an encoding device that converts speech or sound waves into electrical signals. In this case, the data transmission channel is telephone wires, communication centers, in general, the entire telephone network leading from one telephone set to another. The decoding device is the subscriber's handset. It converts an electrical signal back into sound, that is, into speech.
In this diagram of the process of transmitting information, data is presented as a continuous electrical signal. Such a connection is called analog.
Coding concept
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In digital communication channels, information is divided into parts — packets, for each of which a checksum is calculated. This amount is transferred along with each packet. The information receiver recalculates this amount and receives the packet only if it coincides with the original. Otherwise, the packet is sent again. And so on until the checksums sent and received do not match.