Basic Terminology Used in Electronic Communication Systems

Basic Terminology Used in Electronic Communication Systems

• Transducer - any device that converts one form of energy into another. An electrical transducer specifically converts a physical quantity such as pressure, displacement, force or temperature into a proportional electrical signal.
• Signal - information converted into electrical form so that it can be transmitted. A signal can be analog - a continuous, single-valued function of time, like a sine wave (sound and TV picture signals are analog) - or digital, which takes only discrete, stepwise values; binary digital signals use just two levels, 0 (low) and 1 (high).
• Digital coding schemes include binary-coded decimal (BCD), where each decimal digit is represented by 4 bits (e.g. the decimal digits 0-4 are coded as 0000-0100), and ASCII, a standard numeric code representing letters, digits and other characters.
• Noise - any unwanted signal that disturbs the transmission or processing of the wanted signal; it may originate inside or outside the system.
• Transmitter - processes the incoming message signal so that it suits the characteristics of the transmission channel and of the reception process that follows.
• Receiver - extracts the desired message signal from the (possibly corrupted) signal it picks up from the channel.
• Attenuation - the loss of a signal's strength as it travels through a transmission medium.
• Amplification - increasing a signal's amplitude/strength using an amplifier circuit, which is powered by a DC energy source; amplification is applied wherever a signal has weakened below what is needed for it to be used or transmitted further, and so is used to counter attenuation.
• Range - the largest distance between source and destination up to which the signal is received with sufficient strength.
• Bandwidth - the range of frequencies over which a piece of equipment operates, or that a given signal occupies.
• Modulation - the process of superimposing a low-frequency message (information) signal on a high-frequency carrier wave. It is needed because a low-frequency signal cannot, by itself, be transmitted over long distances (explained fully in Section 15.7); the main types are amplitude modulation (AM), frequency modulation (FM) and phase modulation (PM).
• Demodulation - the reverse of modulation: recovering the original message signal from the modulated carrier wave at the receiver. …