I haven’t had cause to use one of these controllers before, but today I needed to check one out for replacement.
It is a DC controller powered by two nine volt batteries and uses the tap as its water source. I guess its a reasonable solution if you want to do some DIY, but I would prefer to run things from the water and elec main.
They aren’t cheap either. I got a price on a replacement unit and it was not far off the price of a regular control box and a bunch of solenoids.