I don't know if this is the place to ask this, but I am a mechanical engineering student about to finish a degree, and I have recently been researching hydraulics. After watching a rear loading garbage truck eat bag after bag going down my street, I can't help but wonder a few things. I understand how hydraulic circuits work, such as power steering systems, but how does the engine of the garbage truck know to increase speed (rev up) when the operator opens the valves to the circuit? And I have seen the operator pull both handles for the sweep and slide mechanisms together, and walk away from the truck. How does the truck know to run the sweep cycle first when both levers are pulled at the same time, deactivate the sweep lever when the slide phase begins, and automatically shut the system down when complete? I've searched and searched but cannot find what I am seeking. I appreciate any responses, thank you.