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Electrical signals are in two forms;

Analogue signals
Digital signals
 

This graph is typical of analogue signals.

Analogue signals: These are usually older electronic gadgets (introduced before the mid 1990’s). A good example of an analogue signal is the loud-speaker of a stereo system. When the volume is turned up the sound increases slowly and constantly.

Examples of analogue systems include;
Old radios, megaphones and the volume control on old telephone hand sets.

This graph is typical of digital signals

Digital signals: Modern electronic products such as computers and mobile phones depend on digital signals. However, a good example of a digital signal is Morse Code. The signal is sent as a series of ‘on’ and ‘off’ pulses. The signal is either present or it is not. Morse code was introduced in 1837 by Samuel Morse, as a method of communication.

For further information on digital computers - see Bits and BYTES.
 

Both analogue and digital systems can be used as sensors. A thermistor is analogue as resistance slowly changes, a micro-switch is digital, as it is ‘on’ or ‘off’.

1 = ON

0 = OFF

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