A little information about DCC auto reversing sections and reversers.
When using DC, if you changed the switch under a moving train, the train would reverse directions. Thus, you generally had two switches. One to reverse the loop, and one to reverse the layout. In DCC, this does not happen.
So as an example, if you have a reversing loop, only the loop would be connected to the auto reverser. You would not need to change the polarity of the main layout any more.
When the train entered the loop, and the loop was not set right, the auto reverser would change the polarity of the loop to match the layout for the incoming train. When that train went to exit the same loop, the auto reverser would again change the polarity of the loop to match the layout. And when this happened, the train would not change directions.
Auto reversers also have an input side and an output side. The output side goes to the section that is to be reversed, such as the loop in the above example. The input side is wired to the DCC bus, the main track next to the reversing section, or the DCC booster output. Wiring the input to the DCC bus is the most logical choice for most folks.
Some auto reversers also act as DCC circuit breakers for the reversing section. Most of the electronic type of auto reversers do.
Some auto reversers do not work well with low current or beginner DCC systems. These systems do not have the current availability to make them operate correctly. So ask questions and do your research before purchasing an auto reverser for your DCC system.
Hope this helps.