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Recognising analogue and digital signals

You should be able to recognise analogue and digital signals, and be able to outline the advantages of digital signals.

Analogue signals

the signal is a wavy line that goes up and down in an uneven pattern

Oscilloscope trace of an analogue signal

Music and speech vary continuously in frequency and amplitude. In the same way, analogue signals can vary in frequency, amplitude or both. You may have heard of FM radio and AM radio – Frequency Modulated radio and Amplitude Modulated radio. The diagram shows a typical oscilloscope trace of an analogue signal.

Digital signals

the signal is a continuous line that goes up, down and across in straight lines with no curves

Oscilloscope trace of a digital signal

Digital signals are a series of pulses consisting of just two states, ON (1) or OFF (0). There are no values in between. DAB radio is Digital Audio Broadcast radio – it is transmitted as digital signals. The diagram shows a typical oscilloscope trace of a digital signal.

Advantages of digital signals

Digital signals carry more information per second than analogue signals. This is the same whether optical fibres, cables or radio waves are used.

Digital signals maintain their quality over long distances better than analogue signals. You will notice far less noise and crackle from a DAB radio programme than in an ordinary FM or AM radio programme.

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