An analogue signal is continuous: it can take any value, and it varies smoothly, the way a needle sweeps across a dial. A digital signal is discrete: it takes one of a finite set of values, and between them there is nothing.
Analogue
- Continuous physical qualities and signals
- A vinyl groove, a mercury thermometer, a clock with hands
- Copies degrade — each generation loses something
- Fails slowly: a scratched record still plays
Digital
- Discrete signals with a finite set of values
- A WAV file, a digital thermometer, a clock showing numerals
- Copies are exact, however many times you copy
- Fails all at once: a damaged file may not open at all
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Turning analogue into digital means measuring the signal at regular moments and writing each measurement down as a number. Two choices decide how good the result is.
The two knobs
Sample rate
How often you measure. CD audio takes 44,100 samples a second. Too few and you miss the fast parts of the signal entirely.
Bit depth
How finely each measurement is recorded. More bits means smaller steps between the values available, so the number is closer to the real one.
How often × how finely = how faithful
Sampling, drawn: the continuous curve, the moments it is measured, and the staircase that is all the file actually holds.
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Something is always lost: A digital recording is only ever close to the original — a staircase drawn over a curve. Raising the sample rate makes the steps smaller, never zero. That is the honest answer to “is digital better?”.
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Almost every argument later in the course rests on one property of the digital: because it is discrete, it can be copied, moved and processed without loss. That is a benefit and a problem in the same breath.
| Property of digital | Opportunity | Dilemma |
|---|---|---|
| Exact copies | Backup, preservation, sharing | Unauthorised copying is as easy as authorised copying |
| Numbers can be processed | Search, filter, analyse | Analysis of data people did not know was collected |
| Media share one format | One device does everything | One breach exposes everything at once |
| Signals can be reconstructed | Robust transmission over poor links | Synthetic media indistinguishable from a recording |
Real-world examples you can name
Digitizing heritage collections — Google Arts & Culture from 2011; Notre-Dame laser scans used after the 2019 fire
Museums and monuments are photographed and laser-scanned at high resolution and published online. Detailed scans of Notre-Dame made before the fire informed its reconstruction — digitization as preservation, not just access.
Who it affected: People who will never travel to the collection, and conservators rebuilding what burned.
The Zelensky surrender deepfake — March 2022
A synthetic video showing Ukraine's president telling troops to lay down their arms circulated on social media and briefly on a hacked news website. It was crude enough to be debunked within hours, but it is the standard example of synthetic media used in wartime.
Who it affected: Ukrainian soldiers and civilians, and anyone judging what video evidence is worth.
How this is tested — you have to distinguish analogue from digital precisely, and then use the distinction to explain something else. It comes up two ways:
Paper 1 — structured question
- Part a: distinguish between analogue and digital data
- Part b: explain why a described system was digitized
Paper 2 — source-based question
- Q2: explain how a source uses a technical term
- Q1: describe what a waveform or sampling diagram shows
The trap: “digital is better quality”: Digital is more robust, not automatically more faithful. A poorly sampled digital recording is worse than a good analogue one. Say robust, not better.
Distinguish between analogue and digital signals.
Model answer plan
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Explain one reason why an archive might digitize a collection of paper documents.
Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.