Analogue signals vary continuously in [?]. They use less circuitry than digital circuits, but the signals are more likely to suffer from [?] by external sources. Examples of naturally occuring [?] signals include changes in light levels, temperature, sound levels, electric and [?] fields.




The analogue clock has a [?] movement of the hands, but this digital clock display only changes every [?].

Transmission of information using analogue signals is less secure than using digital tranmissions. Digital signals are easy to [?], making it more difficult for unauthorised users to gain access. Digital signals only have two values. This is often called a [?] signal. The off state is given a value of 0 and the on state is given a value of . Digital signals are used in modern communications including mobile [?], and satellite communications.




Most television signals will soon be [?]. This image shows a [?], which allows digital signals to be received.

[?] use digital signals, and the information is easily stored on hard drives or usb drives.




Large amounts of digital information can now be stored in a small space, using memory [?]. These are widely used used in digital [?]

Digital circuitry is often more complex, and can use more [?] energy than analogue circuits. They are usually more [?], especially when produced in small quantities.




Transmission of digital signals can be achieved using [?] fibres. In this process the electrical signals are converted into pulses of visible light or [?] light. This involves the use of [?] to digital circuits.



Optical fibres use the phenomenon of total internal [?], as the light is transmitted within the fibres. This is shown in the diagam above. The angle of incidence must be greater than the [?] angle for light to be transmitted along the fibre. Optical fibres are much [?] to produce than heavier, copper cables. Digital signal allow a greater amount of information to be transmitted in a given [?], compared with analogue signals.