GCSE PHYSICS - What is Noise? - What is the Quality of a Digital Signal?

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Electromagnetic Waves - Transmission of Information.

Digital Signals have a Higher Quality than Analogue Signals.

What is Noise and the Quality of a Signal?

The quality of a signal is a measure of
how much the signal has changed during transmission.
A high quality signal has changed very little.
A low quality signal has other information in it
which was not there in the original signal.
The additional unwanted information is called noise.

Any noise which is present in an analogue signal
reaches the receiver and is processed by the electrical
equipment as if it were part of the original signal.

All signals become weaker as they travel
and some frequencies in an analogue signal
may weaken more quickly than others.
If the signal is amplified during transmission,
then the noise is also amplified in the same way.

A digital signal has only two states called on and off.
Since noise is usually of low intensity compared to the signal,
noise is interpreted by the decoder as an off state and
is not included in the signal processing. A digital signal
ignores the noise and therefore has a higher quality
than an analogue signal. Digital signals also
have increased capacity compared to analogue signals.

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