Electrical Glossary

amplifier a system where an input signal is altered (usually in amplitude)

amplitude modulation (AM) a process of modulating the carrier wave in which the amplitude of the carrier wave is changed in sympathy with the modulating signal (information)

analogue a system in which changing values are represented by a continuously variable electrical signal

anti-intrusion system a system or technique used to monitor and prevent unlawful entry to premises by means of, for example, closed-circuit television, electric fencing, gate control, intercom system

astable a circuit which has no stable condition, and which changes at a rate determined by circuit values

audio relating to a system concerned with frequencies within the range of human hearing

base one terminal of a transistor through which 2% of the supply current will flow

binary logic an assembly of digital logic elements which operate with two distinct states

binary number a number system to the base 2

bandwidth the range of frequencies to which a system will respond in the required manner

bipolar-transistor a transistor in which current is carried through the semiconductor both by holes and electrons; it is a current operated device

bistable a circuit which can have two stable states, and which can remain in either state indefinitely

Boolean algebra a system of formal logic used for minimising complex digital systems

capacitor a component used in electronic circuits that has the ability to store electrical charge for a period of time

class A amplifier a system of which the output is identical to the input in terms of frequency and shape but not in amplitude

class B amplifier a system of which the output signal is altered in amplitude and shape representing half of the output signal

class C amplifier a system of the output signal is altered in amplitude and shape to represent less than half of the input signal

collector one terminal of a bipolar transistor through which 98% of the supply current will flow

conductor a material through which an electric current can flow relatively easily

construction encompasses the study of residential, commercial, industrial and recreational applications of Technology, including systems required to maintain and service them

conventional current electric current, regarded as flowing from positive to negative

central processing unit (CPU) the main number-processing and control section of a computer. In a microcomputer the CPU will be a microprocessor.

crystal usually refers to quartz crystal, used as a precision timing element in many circuits; may refer to the term piezoelectric

Darlington pair transistors used in cascade, giving high gain and high input impedance

decibel (dB) one-tenth of a bell; a measure of power gain, on a logarithmic scale (e.g. a power level equal to 10 times the common logarithm of the ratio of the output power to the input power). The decibel is a convenient unit for representing a very large range of power gain.

delta network a combination of three components connected to form a triangular configuaration like the Greek letter delta; also known as a mesh connection

demodulation the process ofrecovery of a modulating signal from a modulated carrier

design includes the study of a variety of basic design processes that are used in solving technological challenges

diac a bi-directional breakover diode; often used for triggering a triac

digital electronics the branch of electronics concerned with the processing of digital systems, usually in binary

diode a component, either semiconductor or thermionic, that permits current to flow through it in one direction only

electronflow regarded as the flow of electrons from negative to positive

emitter one terminal of a bipolar transistor through which 100% of the supply current will flow

energy focuses on domestic, industrial, generation and transmission services

farad unit of capacitance; a very large unit, the largest practical unit being the microfarad

fibre-optic a glass or plastic fibre used for the transmission of information through light

field-effect transistor a type of transistor characterised by a very high input resistance that is a voltage- operated device

flip-flop general term for a bistable, astable or monostable circuit

frequency the number of complete repetitions of a wave form in one second, expressed in Hertz

gain the factor by which the output of a system exceeds the input

gate a component in a digital logic circuit or one terminal of a field-effect transistor, or other semiconductor device

henry unit of inductance

integrated circuit an electronic system, or part of a system, produced on a silicon chip using microelectronic techniques

impedance the ratio of the voltage applied to a circuit to the current flowing in the circuit; similar to resistance, but applicable to alternating currents and voltages

insulator a material through which electric current will not easily flow

Karnaugh mapping a visual technique used in the planning of digital systems for the minimisation of logic circuits

liquid crystal display (LCD) a reflective display used in digital systems for the presentation of output; characterised by a very low power consumption

light-emitting diode (LED) an electronic component in which electric current is converted directly into visible or infrared light

logic the basic principles and applications of truth tables, interconnections of on/off circuit elements, and other factors involved in mathematical computation in a computer; also used as a general term for various types of gates, flip-flops, and other on/off circuits used to perform problem-solving functions in a digital computer

manufacturing and materials product design, process and production planning, raw materials, manufacturing processes and quality control

microcomputer a computer in which the central processing unit is a microprocessor

microprocessor a central processing unit constructed using large-scale integration in which all the CPU circuits are fitted into a single integrated circuit

modulation variation of the frequency, phase or magnitude of a high frequency waveform in accordance with a waveform of lower frequency

monostable a circuit with a single stable state

multimeter a general-purpose measuring instrument, usually able to measure resistance, current and voltage

negative feedback feedback applied to a system in such a way that it tends to reduce the output

NPN one of the two alternative types of bipolar transistors

ohm the unit of resistance ()

operational amplifier a highly stable, gain, DC amplifier, usually produced as a single integrated circuit

opto-electronics electronic systems or devices that involve the use of light

oscillator an electronic system that produces a regular periodic output

oscilloscope an instrument for displaying electrical waveforms on a cathode ray tube

photo-resistor also known as an LDR (light-dependent resistor); a resistor whose value depends upon the amount of light falling on it

piezoelectric effect the direct conversion of electrical to mechanical energy or vice versa in some crystalline materials

programmable logic controller (PLC) a control device, normally used in industrial control applications, that employs the hardware architecture of a computer and a programming language

PNP one of the two alternative types of bipolar transistor

power supply source of electrical energy

positive feedback feedback applied to a system in such a way that it tends to increase the output

protective device a particular type of equipment used in electric power systems to detect abnormal conditions and to initiate appropriate corrective action

rectification the process of changing an alternating current to a unidirectional current

relay an electromechanical device in which an electric current controls a switch

resistance the property of a material that resists the flow of electrical current

speaker an electromechanical device for converting electrical energy into sound (e.g. a loudspeaker)

star network a set of three or more branches with one terminal of each connected at a common node to give the form of a star; also known as a Y connection

technological process the identification, design, development and evaluation of processes and products related to Electrical Technology

thyristor a component similar to a semiconductor diode but having in addition a gate connection by which the component, normally non-conducting, can be triggered into conduction

tolerance generally the amount by which a specified component value can vary from the marked value

triac a semiconductor component similar to the thyristor but which will conduct in either direction

uni-junction transistor a semiconductor device used in some oscillators

voltage regulation a process to maintain the terminal voltage within required limits despite variations in input voltage or load

wavelength the physical distance between two similar and successive points on an alternating wave

zener diode a semiconductor diode, used for voltage regulation. When the zener diode is reverse-biased, it exhibits a sudden increase in conductivity at a certain specific voltage