Hello In the layout attached (DCC), how the positions of the turnouts are "managed"? For example, if I want to send a train on the reverse loop, I will obviously activate turnout A accordingly.... But what about turnout B? What happens if I don't put it in the right direction? Generally speaking, what happens to a train when it passes on a turnout that is not in the proper direction?
You should have insulating Unijoiners on both rails, at both ends of the loop at A and B, where the reverse loop track meets each turnout. Then the reverse loop track should be powered via an auto-reversing power switch/controller/booster, so it will automatically adapt the loop power polarity to the power from the mainline when a train enters or leaves it from either end. It can be a manual switch (DPDT) too. Note, you should not run a train longer than the loop (A to B via the loop) through the reversing loop, since it would simultaneously short the loop to both ends (polarities), and shut down the power. You can use a method akin to "doubling the hill" to reverse a long train via the loop (divide the train in two, and take each half through the loop, one at a time, and join them back together on the other side). You'd need a run-around at both ends of the loop. I see a crossover that might do...
The above is assuming you are running DCC, not DC power. DC usually has to be manually controlled with toggle switches. And the answer to your final question is, when a locomotive enters the de-selected route of a switch (from the Y end), it will short both rails together. It will also be stopped mechanically, since it cannot continue through the switch. Depending on the system, it will either trip an internal circuit breaker, or just stall out the throttle (some low power DC systems). You should not leave the train shorting the powered rails there for long, circuit breakers or not, since things will tend to get warm... An old trick in DC days was to have the power to the track routed through a light-bulb (aka a 12V auto tail-light bulb). When running trains normally, there is not enough current to brightly light the bulb, but when a short occurs, the bulb will be much brighter, and the bulb drops the voltage reducing the chances of harming something (like melting plastic around the shorting trucks, etc.)
The picture below shows where I've installed the insulating unijoiners......are they properly located?
Yep, that should work. You then need an auto-reversing electrical switch or booster to supply that isolated section of the loop.
