1. Analogue and Digital Signals
G. Jones
May 2010

2. Learning Objectives
Communication signals may be analogue (continuously varying) or ...
digital (discrete values only, generally on and off).
Digital signals are less prone to interference than analogue...
and can be easily processed by computers.
(from AQA specification for GCSE Science A p.53)

3. What is a signal? A signal is organised information.
A signal can be transmitted in many ways e.g.
Sound,
Tone (of voice)
light,
gestures,
electronically.

4. Analogue Signals 1
Sound is an example of an analogue signal. This means that it is continuously varying.
It can have any value.
(Analogue = any)

5. Analogue Signals 2
This is an example of the original analogue signal with interference (or noise) added.
Sound is an example of an analogue signal – it is continuously varying

6. Digital Signals
Analogue signals can be converted into digital signals by sampling. Digital signals are easily processed by computer.

7. Digital Signals Worksheet

8. Digital Signals Worksheet
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110
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011
010
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100

9. Digital Signals Worksheet
010
110
011
110

10. Digital Signals Worksheet
The higher sampling rate captures more information.
The digital copy is closer to the original analogue signal.
More memory needed / bigger file sizes / longer time to transmit.

11. Processing Digital Signals
This is a digital signal. This is a digital signal with interference.
Clean Up
The digital signal has a predictable shape so it can be cleaned up easily. This means that digital signals are less prone to interference than analogue signals.

12. Processing Digital Signals Part 1
Follow your teacher’s instructions for the Back-to-Back Activity
2 marks
Title written down
4 marks
Some understanding of the word digital is shown (check spelling)
6 marks
The word discrete is used correctly (with some understanding of meaning and correct spelling)
8 marks
Signal drawn that is clearly digital and not analogue
10 marks
Diagram usefully labelled

13. Processing Digital Signals Part 2
Follow your teacher’s instructions for the Back-to-Back Activity
2 marks
Title written down
4 marks
The word interference is spelled correctly
6 marks
Digital signal with “noise” or “interference” added is drawn
8 marks
Cleaned up digital signal is drawn
10 marks
Both diagrams usefully labelled to show understanding of the process

14. Picture A

15. Picture B

16. Picture C

17. Picture D
Picture E

18. Picture F