A reversing Loop is a mechanism where in a locomotive can change direction while continuously moving forward. It enters a turnout and takes either leg, then proceeds in a loop to the other leg of the turnout and exits. On a model railroad utilizing Direct Current, this is accomplished with a Double-pole-double-throw (DPDT) electrical switch, but on a layout like the Baden, Vogt & DeSmet with utilizes Digital Command and Control (DCC), this is accomplished with a circuit like the AR1 (Automatic Reverse) from Digitrax. Its really pretty simple, and this video shows the reversal in action.
