I installed a couple of these controllers in the late 70s and at that time, the company owner I worked for would rig up a valve manifold out of galvanized pipe and hydraulic valves, and then we'd bury the whole thing without putting in a valve box - guess the thinking at the time was that these things should be so reliable as to not need service...
As I recall, each valve has a 1/4" control line coming off it, each of which plugs into the controller. The valves are off as long as the controller does not allow water to flow out of each control line. The controller has a separate 1/4" drain line which will have constant water flow as long as a valve is open.
I do recall that Toro also used to make a totally hydraulic controller, intended for use in highway medians, etc. where no electricity was available. It would have a constant flow of water from the drain line to run a hydraulic timer.
Don't know if any of this helps or not but that's my limited knowledge of these valves/controllers.