DBD22 - Reverse Loop Application Information

The DBD22 can be used in conjunction with a Tortoise™ switch machine to automatically control a turnout and reverse the polarity in a loop of track. A single track loops back on its self through a turnout (switch) to reverse the direction of train travel. The DBD22 is used to detect block occupancy of two short sections of track at the frog end of the turnout. As the train loops around the track to return to the turnout, one of the short blocks becomes occupied and the DBD22 controls the Tortoise™ to throw or close to the correct state. At the same time the polarity of the loop or reverse section of track is changed to match that of the track at the points end of the turnout. This is done using the Tortoise™ built in electrical contacts.

Both short blocks cannot be occupied at the same time for proper operation. That is, the total train should be able to fix in the reverse section of track. Consider metal wheels.
The wiring connections in the diagram may not be correct based of the Tortoise™ installation. Most likely the wires that power the Tortoise™ from the DBD22 and/or the wires that power the reverse loop will have to be swapped.