First 286 words of the document:
Analogue signals which travel along copper wires are
being replaced by digital signals which travel along optical
As radio waves and microwaves travel from an emitter towards a receiver, there
may be some loss in signal strength, possibly due to diffraction or interference.
Too ensure a strong signal arrives at the receiver, it may be amplified several
times at repeater station.
Analogue signals vary continuously. When they are amplified at relay stations any
distortions (noise) which have been added to the wave during its journey will
also be amplified. If the noise is considerable, the final signal received may be
very different from the original and therefore difficult to understand.
Digital signals have only two values: 1 and 0. An analogue signal can be
converted into a digital signal , i.e. it's continuously changing shape can be
described by a code consisting of just 1s and 0s. This code an then be
transmitted. When the weakened signal arrives at a repeater station, it is easy to
recognized, even with lots of noise, those parts of the signal which should be a 1
and those that should be a 0. These are amplified, producing a perfect copy of
the original. At the receiver, the digital code is converted back into the analogue
signal, but without any noise distortion, i.e. the signal is very clear.
Why are Digital Signals better ?
Digital Signals are better because they are transmitting a clearer sound then a
analogue signal. This is better for TV's because then films and also other
programs are clearly spoken.