question on trigger rapid fire, confused on circuit for rapid fire

[carjason19]

I just do not understand what is going on with the trigger circuit, is the trigger both an input and an output together at the same time?
if i were to use the comparator, would there be different wiring to the trigger? i will be using a cg/cg2 controller.
Basically whats the easiest method? i will also be implimenting other things like adjustable speeds and other features.

[Modded Matt]

the triggers are floating potentiometers.