Here a method used by the modular Free-mo groups that do signaling. It is call MSS for Modular Signal Standard. It uses block track detectors to see the locos and anything drawing power from the rails. But to catch all the cars that likely do not have resistive wheelsets they use an optic detector at each block boundary. What it does it holds each block as active until the optic detector is no longer triggered.

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When I train is passing from one block to the next, first the loco triggers the optic but then continues on and keeps the track block detector active. Next the cars keep both blocks active until the last car passes the optic detector. At that point the prior block clears. Now if the loco hasn’t reached the other end of the block, that block is active because of the loco. However it the loco has hit the next block, then the cars behind it are triggering the local block (and the next block too). This keeps this block active as if all those cars had resistors.

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If you look at the website, you might get the clues from the graphics and other explanations there. Now you don’t need that interconnecting for a normal layout. All that’s because we never know which way the modules end up getting placed into the layout.

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But the idea of combining current detection with the optic at the boundaries is really pretty good at giving the right results regardless of how many cars have resistive wheelsets. Only catch is they won’t detect a broken train that lost a car in the middle of a block.

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-Ken Cameron, Member JMRI Dev Team

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