Hello, everyone!
Today, I would like to continue on the article about remote communication systems - digital.
The classification of telecommunication systems depends largely on the characteristics of the information transmitted, the nature of the channel used for transmission, and the method of embedding.
Digital systems:
In these systems, samples of the signal to be sent are transmitted, taken periodically at specific times. These systems rely mainly on the Shannon theorem, which says: “It is sufficient to recombine the transmitted signal from the receiver end to send samples of it at a frequency equal to twice the highest frequency. in the components of that transmitted signal or greater than it.”
This feature is mainly used for sending samples of multiple other signals, independent of each other, in the time between each two successive samples of the transmitted signal, which is known as time division multiplexing (TDM) typesetting. These samples are usually sent by different methods, all of which fall under the name of pulse modulation, and the most important types are:
PAM. Pulse Amplitude Inclusion
Pulse amplitude modulation
PWM Pulse Width Modulation
Pulse width modulation
Pulse location inclusion PPM
Pulse position modulation
Include the PCM pulse code
Pulse code modulation
PCM impulse modulation is the most famous and most widely used type of impulse modulation in digital systems, in which each sample is evaluated before being sent by a calendar scale with a certain number of separate evaluation levels, to give the sample the correct decimal value closest to placing the sample on the calendar scale, and then this is encoded The correct value is in the binary system, and the binary number expressing the sample value is sent as an appropriate electrical signal.
These systems took their name, i.e., “digital systems” from this type of inclusion. Digital systems are widely used in the field of modern telephone communications, especially in electronic telephone exchanges and in communications systems with large capacities such as terrestrial micro-systems or through artificial satellites.
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