You may be wondering what it is with on and off, and how this translates into physical parameters or electrical signals. These will soon become clear.

We live in a world of analog signals-a countless number of colors that the eyes can see, a countless number of sounds we can hear, and a countless number of smells, and so on.

But with digital electronics, such as Arduino, we deal with discrete or distinct sets of values.

Logic levels, in a nutshell, describe the state that a signal is in. In digital electronics, such as Arduino, there are two logic states: 0 and 1. Since there are only two states, it is also called binary logic. This is also commonly translated to ON or HIGH for binary 1 and OFF or LOW for binary 0.

For Arduino, a HIGH signal is 5V, and LOW is 0V. This is how these logic levels manifest themselves physically in terms of voltage.

The Arduino uses these logic levels on its I/O pins to either take input from the outside world or give an output.

We shall see how these logic levels affect our project as we go further to understand the input and output devices that we shall be using in our project.