Combining logic gates

The logic circuit below shows a combination of two NOT gates and an AND gate.

You can see from the diagram that there are two inputs, which are initially set to 0. The NOT gate changes the inputs of 0 to become outputs of 1. This means that the inputs for the AND gate are both 1. As the AND gate detects that both inputs are now 1 it produces an output of 1.

A real-life example which might use such a setup would be an indoor irrigation system. The watering system has two sensors, one for light, the other for soil moisture. A gardener might only want to water at night (to avoid excess evaporation). So, for the watering system to come on the light sensor should NOT be activated (i.e. it’s dark) AND soil should be NOT moist.