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How to use the Azatrax model train crossing signal controller with block occupancy detectors.

The MRX2 crossing signal controller senses train movement near a model railroad grade crossing, and uses that information to operate crossing signals and crossing gates.
The controller has built-in detector circuits to use infrared (IR) train sensors, and it may also be used with block occupancy detectors.

Atlas BDB Block detectors sense the presence of a train in a track block. A block is a length of track that has one rail electrically isolated from the rest of the layout. Power to that rail is routed through a block occupancy detector. When the block detector senses current flowing into the track block, it switches its output to indicate that a train is present.
The MRX2 controller will work with any block detectors that switch their output to 'ground' (the negative side of the DC power supply) when the block is occupied. This is the case for nearly all block detector circuits.
The exception is Digitrax®. Their detectors typically switch to the positive side of the power supply. This does not work with the MRX2. Contact us for help using Digitrax® detectors.

block detector placement

The drawing above shows where to place the three block detectors. One is for the western block, one for the crossing ('island') block, and the third is for the eastern block. Connect each detector to the track according to the detector instructions.
block detector connections Connect the three block detectors to the MRX2 signal controller as shown at left. Be sure to connect all 'ground' or 'common' points on each detector to terminal C on the MRX2.
Remove the '8det 2trk' jumper from the MRX2.
The MRX2 is able to monitor one track with block detectors, plus an additional track with its on-board IR train detectors.
For IR detector placement examples, see the crossing configurations page.

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