16.4 ANALOGUE AND DIGITAL ELECTRONICS
The quantities whose values vary continuously or remain constant are known as analogue quantities. For example, the temperature of air varies in a continuous fashion during 24 hours of a day. If we plot a graph between time and temperature recorded at different times, we get a graph (Fig.16.5- a). This graph shows that temperature varies continuously with time. Therefore, we say that temperature is an analogue quantity. Similarly, time, pressure, distance, etc. are analogue quantities.
The branch of electronics consisting of circuits which process analogue quantities is called analogue electronics. For instance, the public address system is an analogue system in which the microphone converts sound into a continuously varying electric potential. This potential is an analogue signal which is fed into an amplifier. Amplifier is an analogue circuit which amplifies the signal without changing its shape to such an extent that it can operate a loudspeaker. In this way, loud sound is produced by the speaker. Radios, televisions and telephones are a few common devices that process analogue signals.