Home · IGCSE 0625 · Electromagnetic spectrum · Digital vs analogue · Practice
Extended · Practice questions · Digital vs analogue

Two levels you can rebuild.

Six original Cambridge-style questions. They cover the difference between the two signal types, the benefits of digital, what regeneration means, and why it is not the same as amplification.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
The whole case for digital

Two levels. Noise removed. Quality kept.

01
[2 marks]

State the difference between an analogue signal and a digital signal.

  • An analogue signal varies continuously and can take any value. ✓
  • A digital signal has only two values (0 and 1, or low and high), sent as pulses. ✓
02
[3 marks]

State three benefits of transmitting information using digital signals rather than analogue signals.

  • Noise can be removed by regenerating the signal, so quality is kept over long distances. ✓
  • More information can be sent per second, and many signals can share one route. ✓
  • The data can be stored, copied, and processed by computers without loss, and errors can be detected. ✓
03
Analysis
[3 marks]

Explain what is meant by regenerating a digital signal, and why this keeps the quality high over a long distance.

  • Regenerating means the receiver decides whether each noisy pulse is a 0 or a 1, and sends out a fresh, clean pulse. ✓
  • This removes the noise the signal picked up, rather than carrying it on. ✓
  • Doing this repeatedly along the route stops noise building up, so the signal stays high quality over a long distance. ✓
04
Analysis
[2 marks]

A student says that an analogue signal can be cleaned up just as well as a digital one by amplifying it. Explain why this is wrong.

  • Amplifying an analogue signal makes the noise louder along with the signal, so the quality is not restored. ✓
  • Only a digital signal can be regenerated, because the receiver can decide each value is a 0 or a 1 and send a clean pulse, leaving the noise behind. ✓

Amplifying boosts everything, noise included. Regenerating rebuilds a clean signal.

05
[2 marks]

State whether each of the following is best described as an analogue or a digital signal:

(a) the continuously varying voltage produced by a microphone, [1] (b) a stream of pulses representing only the values 0 and 1. [1]

(a) Analogue. ✓

(b) Digital. ✓

Continuously varying, analogue. Only two values, digital.

06
Analysis
[3 marks]

The same recording is sent along a very long cable, once as an analogue signal and once as a digital signal. At the far end, the digital version sounds much clearer.

(a) Explain what happens to the noise in the analogue signal as it travels. [1] (b) Explain why the digital signal arrives with much less noise. [2]

(a) The noise becomes part of the continuously varying signal and builds up, and it cannot be removed. ✓

(b) The digital signal is regenerated at stations along the cable: each pulse is read as a 0 or a 1 and a fresh clean pulse is sent on. ✓ So the noise is removed instead of building up. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.