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Hello all,

I am bench testing an MTH 3 position Semaphore (3 wires, black, green, red) with a Scale Trax ITAD.  I am wiring according to package directions.  I bought both of these items years ago at a train show, and both were new in box.

My issue is that the semaphore never moves to red.  It is in the green position until I activate the ITAD with motion (of my hand, to mimic a train passing) at which time it moves to yellow.  Then after the built in delay, it moves back to green.

From the instructions, this doesn't appear to be the proper behavior.

Has anyone experienced this before?  I'm wondering if either the ITAD or Semaphore is defective?

Thanks in advance for any insights.

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@Brad Trout posted:


I'm wondering if either the ITAD or Semaphore is defective?


I suggest you take the ITAD out of the picture and directly test just the semaphore.  So per instructions,

Connect black wire to AC common (outer-rail).

Then, connect red wire to AC hot (Accessory AC or center-rail depending on how you're powering your signals).  Does it go to the red position?

Then, disconnect red from AC hot.  Connect green to AC hot.  Does it go to yellow position...and then after ~10 sec go to green position?


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Thank you, @stan2004  !

When I tried your approach, the green wire worked as expected.  The red wire doesn't cause the semaphore arm to drop back down.  It acts as if it simply relies on gravity to fall back down, but that doesn't happen without a little manual push.  So, I'm guessing what is supposed to happen is some mechanism inside the semaphore is supposed to push the arm back down, which is defective.

As follow-up, in case anyone else has this problem... I think I fixed it. 

The head (black) of the semaphore moves up and down on, as well as pivots slightly around, the pole (silver/gray).  Depending on the exact location up/down and the semaphore arm wouldn't drop into the bottom, red position.

After much fiddling of the semaphore head on the bench and getting it to work, I installed everything on the layout.  A bit more gentle fiddling once on the layout, and it now seems to work but still very temperamental.


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