Can I use the DT-1 and DT-2 Bi-Directional detectors with DCC?

Circuitron does not have any bi-directional grade crossing detectors that are optimized for DCC.  We do have some under development, but lack of time has prevented us from completing these and bringing them to market.  Both our existing bi-directional units, DT-1 and DT-2, were designed long before DCC was known and rely on monitoring the DC track polarity to "tell" the circuit which way the train is traveling.  Without that DC polarity change, the boards get "confused" and will typically work in one direction but not the other.

There is a workaround, but it requires the addition of a panel direction switch and the operator must act as a "dispatcher" just as in real life and set the direction of travel prior to a train passing.  Depending on your crossing location and your trains' mode of operation, this may or may not be "clumsy".  Although most all DCC layouts are designed to operate bi-directionally on a given track, what most modelers find is that they run predominantly in one direction on a  specific track with multiple trains following each other in the same direction.  With this type of operation, you will rarely have to change the panel switch and your detection will function just fine without much operator intervention.

The only other solution we have at this time is to use a very simple detector such as our DT-4.  This circuit has 4 independent detectors on the one board and they may all be used separately.  If you place an Opto-Sensor just a short distance before the crossing on each side, you will get bi-directional action.  Of course, the flashers won't start nearly as early as they SHOULD, and unlike our DT-1 and DT-2, they will hold on after the last car clears the crossing until it is finally clear of the other Opto-Sensor.  But many people don't mind the messed up timing of it all that much.  As long as the crossbucks are flashing when the train passes, they don't pay much attention to the start and stop times.  So this might be a solution for you that does not require the panel switch as the DT-4 is completely independent of track power.  It will NOT work with crossing gates, though, as the sensors need to be placed WAY before the crossing for gates, to allow enough time for the gates to fall and be completely horizontal when the train passes.  No one wants partially lowered gates as their trains pass.  With a fairly rapid 4 second gate lowering time, believe it or not, the Opto-Sensors need to be 9 FEET before the crossing in HO scale to allow enough time for a passenger train running at a scale 70 mph.  Problem is, you then have another sensor 9 feet beyond the crossing and the gates won't start to rise until AFTER that sensor is also cleared.  So the DT-4 is not a good solution with gates.