There is a little more to it.
The PTO engages a cam. The cam is two round off-set cylendars. The off-set round cam rotates in a slider (item 26) that is round in the middle and square on the outside. This translates the relative motion into a verticle movement in the pump piston frames (Item 24). And a relative horizontal movement of the pistons in the pump housings (Item 25).
One side effect of this is... you can lift an implement without the engine running. Just place your plow spanner over the PTO splines and rock it back and forth a 1/4 turn or so and you"ll raise the lift. Assuming of course the quadrant is in the up position. The pump does not even have to be engaged.