4.1 THE BASICS OF TELECOMMUNICATIONS 76 TELECOMMUNICATIONS Telecommunications is the process of exchanging information over significant distance by various types of technologies such as radio waves, optical fibres, wires or other electromagnetic systems . Telecommunications began with the invention of the electric telegraph in the 19th century, soon becoming one of the fastest growing fields of industry. Basic components The basic components of a telecommunication system are: In computing, examples of simplex telecommunication systems are computer to printer communication, and keyboard to computer connection. Information source, the object which encodes message data and transmits the information to one or more receivers; Input transducer, a device that converts physical quantities such as sound or light deriving from the information source into a suitable form which can be transmitted along the communication channel, i.e. a microphone; Transmitter, an electronic device that transmits data received by the transducer. Examples are cell phones, computer networks, radio and TV broadcasting; Channel, the medium that carries the message. In telecommunication, the transmission of signals can occur in two ways: through physical mediums like cables; wirelessly, i.e. through electromagnetic waves; Electrical signal medium: mezzo source: fonte Channel Message (sound, light, pictures, words, etc.) Information source Electrical signal Input transducer Transmitter Message (sound, light, pictures, words, etc.) Receiver Destination Receiver, an electronic device that receives signals and converts the information into a usable form; often, the device is both a transmitter and a receiver as in the case of cell phones; Destination, the intended recipient of the message. Other components These basic components may be implemented by others: an amplifier increases the power of a signal either at the source or at destination; an encoder converts data or signals by using a specific code and may be employed in the transmitter; a decoder changes a given code into a set of signals in the receiver to prepare them for transmission. Types of telecommunication systems There are different types of telecommunication systems: Simplex, a one-way communication mode in which only one signal is transmitted, and always goes in the same direction, i.e. a megaphone ; Duplex, a two-way system that works both as a transmitter and a receiver. It can be: half-duplex, when the two directions are used one at a time, for example a walkie-talkie; full-duplex, when both directions are used at the same time, for example the telephone; Broadcast, a system with one powerful transmitter and many low-power receivers, as in the case of radio and television broadcast transmissions; Multiplex, a system in which multiple transmitters and multiple receivers cooperate and share the same channel, such as in videoconferencing. 174 TelecoMMUNicaTioNs aND NeTWorKs Elettronica-Informatica.indb 174 25/01/24 16:09