Analogue & Digital Signals
Physics: Cambridge International GCSE Supplement, topic 3.5.10
Analogue & Digital Signals
A signal is a way of transmitting information. The two main types of signals (analogue and digital) differ in how they carry information.
Analogue signals
- An analogue signal is a continuous wave.
- Example: A sound wave from a person's voice is analogue. The vibrations in the air are continuous.
- The information is carried by changing the signal's amplitude (strength) or frequency (how often it repeats).
- This signal can have any value within a range.
- Example: A microphone converts sound waves into an analogue electrical signal.
Digital signals
- A digital signal is a series of pulses, or 'on' and 'off' states.
- It is not continuous; it is a sequence of discrete steps.
- These signals only have two values (usually 0 and 1, in binary code).
- Example: A sound recorded on a computer for a CD is digital data. The original sound wave is sampled and converted into a string of 1s and 0s.
Transmitting sound
- Sound waves can be sent as either digital or analogue signals.
- When a sound wave hits a microphone, it is converted into an electrical signal.
- Analogue transmission:
- The electrical signal is a continuous wave that mimics the original sound wave, carried by varying electrical voltages.
- Digital transmission:
- The original sound wave is sampled and converted into a binary stream (a digital code), which is then transmitted.
Benefits of digital signals
- Digital signals can transmit more data in less time because they are discrete pulses.
- Digital signals can be sent over longer distances without losing quality.
- When the signal becomes weak or distorted, it can be easily restored:
- The receiver simply needs to identify whether a pulse is a '1' or a '0' to recreate the signal perfectly.
- This is harder with an analogue signal, as any noise becomes part of the continuous wave and cannot be removed.
Test yourself on Analogue & Digital Signals
What does a digital signal consist of?