Guys, you're the expect, but let me tell you what confuses me - that MOSFET on the left, it's 3 pins are all connected to fixed volatges, as i marked on the schematic respectively +3.3V, +5V and GND directly from the power supply. So, that means nothing is really switched, if the input doesn't change, right? maybe it's done like that in case +3.3V or +5V rail disappeared, i.e. in case of fault in the power supply?
in any case I still cannot understand from your replies assuming by "output" you mean point "? ? ?" on the schematic what voltage should be there?