The valve that the pressure enters has a mix to activate it with each of the other valves. Must have it slightly open as you can see fluid flowing when no stick movement with pump running. I'm assuming the mix opens the (input) valve more as the other valve activates. ?!?? If that servo is disconnected and not working then the hydraulics don't work. Unless the ports on the inside are different I don't see why it couldn't be optioned to re plumb / re radio mix and end up with a forth valve for attachments (thumb)?? I don't know how far I will explore this at this time but if unanswered by winter I'll find out.
. Wonder if anyone else knows how this works or why they choose to run this way. To me it seems like more work all the way around and harder on the pump. Unless ,,,,,, maybe it is acting like the prv only diverting flow until stick input is required then pressurizing and then relying on the prv to handle excess pressure? That seems logical. That make some sense to me with being able to see the flow in the clear lines.