I think they are really suggesting adding DCC circuit breakers. MRC makes one but you would probably be better off with a PSX circuit breaker from DCC Specialties. A PSX-1 to make your layout one circuit or a PSX-4 to divide into up to 4 sections.
Peter
The support staff at MRC advise that I install dedicated circuit breakers between the track bus and the command unit, adjusted to trip before the command unit breaker trips. This will protect the layout from shorts while allowing the command unit to provide uninterrupted power to the throttle bus (and WiFi module). This could get expensive. There is the Voltscooter Electronics circuit breaker that were incrementally adjustable and sell for around $8 each or $35 for 5 breakers. I can't find any reviews for these yet.
Hornblower
I use an MRC Prodigy Advance (not squared) DCC system to power my 10' by 19' double deck HO scale layout. To save construction costs, I used generic Cat5 components to fabricate the throttle bus which is powered by the command unit. I have two tethered throttles, two wireless throttles (via the plug-in receiver), and the MRC WiFi module connected to the throttle bus. Everything works quite well and I am very happy with the system. However, a problem cropped up during a recent operating session that had not occurred before. The train schedule had as many as four crews running trains simultaneously. Several of the operators found it most convenient to use their personal smart devices as wireless throttles (the MRC WiFi module will accomodate up to 8 smart devices at a time). The problem that occurred was that every time someone accidentally caused a short circuit, the breakers would interrupt power to both the DCC power bus AND the throttle bus. Power would be restored to both buses as soon as the short was cleared but the interruption of power to the WiFi module would cause the smart devices to lose their connection to the WiFi module. This meant that every short would cause the smart throttle users to have to completely start over, first re-connecting with the WiFi module and then re-acquiring their train. As several of the operators were novices, short circuits were many, causing lots of frustration for the WiFi users.
Has anyone else experienced this problem when using the MRC WiFi module? Does anyone know whether installing the MRC 0001502 Powered Extension Plate in my existing throttle bus will eliminate such power interruptions to my WiFi module? If so, does anyone know where I can obtain one of these powered extension plates as they are not currently available from MRC or most retailers?