Telecommunication Systems Overview

Telecommunications: Distance Communication

Transmission Channels

Transmission channels are the physical support through which the encoded message flows. They can be:

• Guided: Driving waves through a physical path.
• Unguided: Only allows the transmission of waves.

Types of Guided Transmission Channels:

• Cable Pairs: Consists of two wires of conductive material, usually copper, coated with an insulating material (urban telephony).
• Coaxial Cable: Composed of two concentric conductors separated by an insulator. It achieves high transmission speeds for large distances (TV).
• Optical Fiber: Consists of fibers that transmit light signals. It allows sending data more rapidly than cable pairs or coaxial cable. It is lighter but has the disadvantage of being more expensive.

Antennas

An antenna is a device capable of issuing and/or receiving radio waves. When it works as a broadcaster, if you apply a given alternating voltage, it generates an electromagnetic field that allows it to radiate waves. When it functions as a receiver, an electromagnetic field generates an alternating voltage.

Satellite Communication

Satellites act mainly as repeaters for electromagnetic waves from Earth or another satellite. They are at distances between 1000 and 36,000 km from Earth (involved in telephony and the transport of TV and data signals). They can be:

• Passive: If they just bounce the signal like a mirror.
• Active: If they amplify the received signal before retransmitting it.

Analog System

Based on the transmission of information in the form of waves that are basically the same way as sound waves. In analog encoding, information is converted into a given electrical current called an electrical signal and processed (microphone).

Digital System

In digital encoding, data is converted into a series of zeros and ones, called the binary system. In this way, digits only constitute impulses (e.g., PC). Features:

• Variations in the signal can be properly regenerated.
• The system has mechanisms to facilitate verification and ensure that the transmission of information is accurate.
• The system may have mechanisms to allow compression of repeated series of digits without losing data.

The Telegraph

It is a telecommunications system based on the emission and reception of signals from an electric pulse code. The first telegraph was based on Morse code and transmitted messages using electrical impulses circulating through a cable.

The Amplification of Sound

• Microphone: Consists of a capsule containing a membrane that vibrates when it receives sound waves. Through various systems, vibrations become electric waves with an intensity proportional to the strength of the vibrations.
• Amplifier: Is an electronic device that provides power to a weak electrical signal.
• Speaker: Receives the duly amplified electrical signal and converts it into sound. The speaker consists of a membrane attached to a coil inside a powerful magnet. The electromagnetic effect moves the coil when the electric current passes through it. The vibration of the moving coil is transmitted to the membrane and thus plays sound. The set is placed on a sounding board to amplify the sound.

The Telephone Network

Telephony is a telecommunications system that allows the transmission of voice and other sounds through electrical signals. Its operation is based on the transformation of an acoustic signal into an electrical signal that occurs in the microphone, allowing this signal to be transmitted over a distance.

• The Transmission Network: Constituted by cabling and switching equipment that link the various telephone exchanges, and transoceanic cables or satellite communication.
• The Subscriber Network: Constituted by the wiring that goes from call centers to mobile users.

The Fax

The fax is a telecommunications system to transmit data, either written or graphic information, via a telephone line. Once the target number is dialed, the computer establishes a connection via the telephone line with the fax, which scans the information and converts it into electrical impulses. These impulses are transmitted via telephone lines.