[Asmodeus]

They're in-game inspired diagrams. The key is in the paragraph above the start of the 'Unclocked Logic' section.

     A
  →o * o→M O
   o * o
     B

The mechanical power goes in the first →, and the [M O] part is the output. A and B are the AND inputs. Gearboxes actually look like *, but o is also being used for gearboxes, albeit gearboxes that are just there to drain power.