Another question regarding circuit breaker for modern trains

The breakers aren't protecting any of "the circuit board trains".

The TVS diode on the "A" throttle is protecting B-C-D when "A" is on, but not as well - it is wired in parallel to B-U, C-U, & D-U.  It will clamp voltage spikes on the A-U circuit when the breaker pops and protect the other throttles from spikes originating on A-U.

Thanks, Rob. I bought 4 magnetic breakers that are ‘instant’. I originally thought I would place 1 breaker in series on each of the 4 A-D posts in addition to TVS diodes between power and common. I may pick up one of the LC/LC+/LC+ 2.0 and wanted to be sure to protect them.

I didn’t realize the in line breakers didn’t also help protect the circuit boards when there is a short on the track. Maybe they do, but the TVS diodes are the critical component. 

I run conventionally now using the A and D handles for track power and B and C are accessories. I might save the 2 breakers that I was going to use on B/C for the Christmas layout under the tree.