Digital & Analogue Signals (CIE IGCSE Physics)

Extended tier only

• There are two types of signals:
  • Analogue
  • Digital

• Analogue signals vary continuously - they can take any value

 An analogue signal

An analogue signal is continuously varying, taking any value

• A digital signal can only take one of two (discrete) states
  • These are usually referred to as;
    • 1s and 0s
    • Highs and lows, or
    • Ons and offs

 A digital signal

A digital signal can only take one of two values – 0 or 1

Extended tier only

• Sound waves that can be transmitted as a digital or analogue signal

• Signals for speech or music are made up of varying frequencies
  • To make out the information clearly, the signal needs to be transmitted with as little interference as possible

• The signal undergoes digital sampling
• It is converted both before transmission and after being received
  • Before transmission: the signal is converted from analogue to digital
  • After being received: the signal is converted back from digital to analogue

Extended tier only

• The benefits of digitally sampling a signal include:
  • Increased rate of data transmission
  • Increased range due to accurate signal regeneration

Digital sampling an analogue signal

Analogue v digital signal

• The key advantages of data transmission in digital form compared to analogue are:
  • The signal can be regenerated so there is minimal noise
  • Due to accurate signal regeneration, the range of digital signals is larger than the range of analogue signals (they can cover larger distances)
  • Digital signals enable an increased rate of transmission of data compared to analogue
  • Extra data can be added so that the signal can be checked for errors