The three main components of every automatic sprinkler system are the controller, station-control valves and sprinklers.

The controller is the brain of the system, telling the control valves when and how long to supply water to the sprinklers. The sprinklers direct and control the water applied to the lawn and plants.

Each valve controls a specific group of sprinklers called a watering station. The stations are generally laid out and installed according to the type of plant material to be watered, the location of the plant within the landscape and the maximum amount of water that can be supplied. Each valve is connected to a numbered terminal within the controller, identifying it as Station 1, Station 2, etc.

The controller operates the valves in order, one at a time. In other words, one station would water completely before another station would turn on. This is called a watering cycle. The information stored in the controller memory that determines when and how long the stations will water is called a program.