Telecommunication systems
Telecommunication is the transmission of information at this distance. Depending on what type of information is transmitted, there are analog and digital communication. Analogue - this continuous channel of communications (such as sound or speech). The digital communications systems - this transfer of information in the form of discrete (digital form). However, discrete messages can be transmitted analog channels and vice versa. Currently, digital communication replaces analog (digitalisation happening), because analog signals can be translated into discrete signals and back (conditions for the possibility of such a transformation, set theorem Kotelnikova) without significant losses.
Depending on the mobile Springs and recipients of information or not, there are stationary (fixed) and mobile telecommunication systems (mobile, communications with mobile objects - SPO).
At the physical principles underlying the lines of communication, the following types of communication:
- Wired link - the transfer is being guided along the environment.
- Communication of electric cables
- Fiber-optic link
- Wireless (radio) - are used for the transmission of radio waves in space.
- -DV, SV-, and HF-VHF communications without the use of transponders
- Satellite communications - a connection with the use of transponder space (s)
- Cellular Telecommunications - relation to the use of the land-base stations
Disclosure of information in a general way signals on the lines on which organized the channel (s) transfer.
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Have long used such methods of alarm as smoke, the battle drums, marking flags at sea (see eg. Flags International Code of Signals) operating at a distance of many kilometers. However, a long time there was no way of transmitting information over long distances, except for media transmission (as gontsa, letters, etc.)
One of the earliest (end of the XVIII century) technology was an optical communications systems Telegraph. He was subsequently replaced electric telegraph and later telephone. Digital communication systems evolve from 1960 - ies.