Well, I suppose what I was trying to say was that once the pressure switch is triggered, it sends a signal to the attesa ecu, which in turn cuts the power to the pump relay.
I did however take apart the some of the pump components to see how they work. With your pump on the right, looking down at the top of the assembly, working from right to left: you have the pump, a large black cylinder (unknown purpose), and then the pressure switch (small black cylinder with 2 leads. Then underneath the pressure switch is the solenoid (medium gray cylinder with 2 leads). I haven't taken the piston assembly that the solenoid engages, but I now see how the solenoid controls how much pressure is fed to the transfercase actuator. It either has full pressure with no current to the solenoid or full. As I said, I will have to take the piston assembly apart at some point to clarify.
Do you know what the black cylinder in between the pump and the pressure switch is?