Introduction

A current whose polarity alternates from positive to negative over time. The rate of such "alternations" is measured in cycles per second - more commonly known as Hertz (Hz)

The basic unit of current flow

a measurement of the capacity of a storage medium (a single cell or a battery). A cell which can supply 1 Amp for 1 hour before it is discharged to a specified minimum level is said to have a capacity of 1 Amp hour

a method for increasing the amplitude (or loudness) of electrical signals

An electronic device which generates a high power signal based on the information supplied by a lower powered signal. A perfect amplifier would add or subtract nothing from the original except additional power - these have not been invented yet

the loudness of sound waves and electrical signals. Amplitude is measured in decibels (dB) or volts

A device that converts the infinite range of an analogue signal into discrete "steps". Normally, a good audio ADC will use sufficient "steps" to resolve the smallest musical detail. For CD, this is a 16 bit converter, having 65,536 discrete levels covering the most negative signal level to the most positive

the decrease of a signal's amplitude level over any distance during transmission or through purpose designed attenuators. Attenuation measures signal loss in decibels (dB)

a bank of individual cells connected together to provide the required voltage