Module 5, the swing bridge has completed wiring. As part of this work, I have installed a cut-out switch so that when the bridge is operated power is cut not only to the swinging part, but also the three feet of track leading up to it. The other issue is that when computer controlled, if the track power is cut all the sections will appear empty – encouraging a collision!
The solution is to use a SPDT microswitch mounted on the fixed baseboard/benchwork part with an arm that is activated by some washers that are screwed on the swinging part. The power is routed over the NO contacts (since we only want the power on when the gate is closed). The switch isolates only the power from the track bus, but does not interfere with the accessories bus that also powers the track occupancy detector BlocD8.
When the bridge is open, the NO contacts are open, but NC contacts are closed instead and pass current through a 10k Ohm resistor – and the current in the wire is read by one of the BlocD8 track circuits. In this way the computer will see an occupied block that inhibits all movement when the bridge is open and all trains will stop..