Circuit breakers are okay for over current but not for short circuit protection, at least not to protect digital electronics, motors and static loads maybe, the instantaneous current flowing from a dead short will fry digital electronics LONG before the breaker trips. After reading "The Art of Electroncs" it says the most common simple method of short circuit protection is a zener diode feeding the gate of an SCR. The SCR is set as a crowbar which will blow a fuse rather than let the current through to the circuit.