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My MTH signal bridge straddles 2 parallel tracks that join at a switch (turnout) with the route continuing as a single track.  Both position light heads are controlled by a DZ1008 relay triggered by a ground wire from an insulated third rail on the single track section.  The idea is to hold a train on either parallel track if the single track ahead is occupied.

All works OK, but both signal heads either have a vertical Proceed aspect or a horizontal Stop aspect.  I would like to have each signal head's indication depend on the position of the switch.  This way, when the track ahead is occupied, both signal heads would show Stop; however, when the single track ahead is clear, the signal head over the track aligned with the switch would show Proceed, and the other signal head would show Stop.  This would be a little more interesting.

Another relay connected to the switch machine could separately control the signals, but the result is that one of the signal heads is getting both a Proceed and a Stop trigger from the two relays and lights up like a Christmas tree.  Not very RR authentic - although my wife says it looks pretty!

I know that some sort of sophisticated logic device might solve my problem, but anything like that is beyond my level.  Is there a simpler way that I can get my desired result? 

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Baldoc posted:
...

I know that some sort of sophisticated logic device might solve my problem, but anything like that is beyond my level.  Is there a simpler way that I can get my desired result?

So your turnout provides output wire(s) that indicate straight vs. diverge?

Also, your existing wiring diagram would be handy as a starting point. 

What constraints do you have?  Less than $10 out-of-pocket?  No soldering?  No messing with small components (diodes, resistors, whatever)?  No eBay - only stuff you can get at local Radio Shack or whatever?

Consolidated Leo posted:

Is this what we're talking about?

I suspect it is, but all of the MTH signal offerings that I'm aware of are meant to be fairly stand-alone -- working off some type of very simple detection device or relay.  The yellow aspect is based solely on an internal timer circuit rather than whether trains are actually in proceeding blocks.  For my purposes, the MTH signals work great, since the signaling I plan to have is minimal -- only protecting track blocks that travel underneath mountain scenery or tracks approaching a station or grade crossing.  

But I can see some folks may want more prototypical signal operation, in which case Atlas-O's system may be a better choice since the signal controllers are linked.

Once you start introducing more complicated criteria (typically at interlockings) for the signal indication (i.e., turnout positions, trains in the proceeding block, etc...), it typically involves logic circuits where relays are wired in series/parallel as needed based on the 'and' and 'or' criteria established for the interlocking.  

David

Last edited by Rocky Mountaineer

Many thanks for the replies.  I am always amazed at how quickly people respond to posts.

Leo, I appreciate the schematic.  I will give it a try.   It appears that it is designed use the DPDT relay to cause the Switch Relay to override the Single Track Relay when the single track section is unoccupied - exactly what I am looking for.

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