Digital & Analogue Signals (Cambridge International IGCSE Physics)

Spec point — 3.3.5 · Know the difference between a digital and analogue signal

Digital & analogue signals

Extended Tier Only

• There are two types of signals:

  • analogue
  • digital

• Analogue signals vary continuously - they can take any value

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
    • ons and offs

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

Transmission of sound

Spec point — 3.3.5 · Know that a sound can be transmitted as a digital or analogue signal

Extended Tier Only

• Sound waves 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

Benefits of digital signalling

Spec point — 3.3.5 · nan

Extended Tier Only

Digitally sampling an analogue 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 data transmission compared to analogue
  • Extra data can be added so that the signal can be checked for errors

Exam Hint Remember that digital sampling is when you convert an analogue signal into a digital signal by recording sound at set time intervals.