Unlike an analogue signal, the digital signal
uses a code with two states which are called on and off.
The on state is a small pulse of the electromagnetic carrier wave.
The off state is the gap in between the pulses
where there is no electromagnetic wave.
The digital signal can be represented by the picture below.
When the digital signal reaches its destination,
the series of on and off states
must be changed back into the original information.
This process is called decoding.
