These are typical valve boxes are used with the Irritrol RainDial RD600, RD900, and RD1200 models. Valve boxes contain the valves and each valve has a solenoid that controls the water flow. The sprinkler timer, like the RD600, activates the solenoid by applying 24VAC to the wires connected to it. The sprinkler timer is simply a 24VAC switch with some fancy scheduling capability.
Valves and wiring inside the valve box that is controlled by the Irritrol RainDial.
The wires go to the solenoids. The other end of the wires go to the timer.
Typical Valve and Solenoid
A typical solenoid; it screws into the top of the valve.