JS debugger on conceptual level

I am exploring a possilibity to add Firefox debugging into our Splinetech 
JavaScript Debugger: www.remotedebugger.com

Since it will only enrich mozilla if another debugger supports it, I would 
like to learn more about how the FF debugger works conceptually. If there is 
a diagram, that will be great.
I obviously checked the firebug docs but I find it not clear.
What are the essential classes and components that make the debugging 
possible, and how do they interact with each other.

Thanks,

Daniel..
www.remotedebugger.com