3.3 TELECOMMUNICATIONS AN INTRODUCTION 60 Telecommunications is the transmission of signals over long distances for communication purposes. After the discovery of electricity, telecommunication developed with the invention of the telegraph, the telephone, and the radio . Nowadays, we also use mobile phones, TVs, and computers to send words, images, texts, and sounds. Telecommunication happens in two ways: Who are the inventors of the telegraph, telephone, and radio? Some devices such as antennas, mobile phone cells, and satellites can function both as transmitters and receivers; for this reason, they are called transceivers. Receiver, which is an electronic device that receives radio waves and converts the information into a usable form ; Output transducer, which coverts electrical signals into energy; Destination, which is the recipient of the communication. Analogue vs. digital transmission To be transmitted, the information must be transformed into signals that can be analogue or digital: through physical media, such as wires and cables; wirelessly, through electromagnetic waves. Input signal Input transducer Transmitted signal Transmitter Sender/ Transmitter A bit (binary digit) is the smallest unit of data that a computer can process and store. See Unit 3.2. to convey: trasmettere medium: mezzo to prevent: prevenire source: fonte transceiver: ricetrasmittente wire: cavo, filo (elettrico) Received signal Channel Distortion and Noise Output signal Output message Output transducer Receiver Receiver Components The basic components of a telecommunication system are: Information source, which produces the information and transmits it to one or more receivers; Input transducer, which is an object that converts energy into an electrical signal which can be read; Transmitter, which is a device that produces radio waves from an antenna; Channel, which is the medium that carries the message (it can be wires, the air, or space in the case of radio and television transmissions, or fibre-optic cables); 140 ELECTRONICS AND ELECTROTECHNOLOGY Destination Source Input message analogue transmission is a method of conveying information using a continuous signal produced by electromagnetic particles. It was the first type of data transmission in the history of telecommunications; however, its disadvantage is that it can easily be distorted by interference or noise; digital transmission means transforming an analogue signal into a series of bits in order to transmit them in discrete quantities, which prevents the risk of interference or degradation. The number of bits transmitted in a second defines the quality of the transmission.