Tim,  Sorry just saw your question about the Special Issue from Model Railroading... here's a photo of the cover... I have had it for at least 7 or 8 years, maybe they re-issued it, not sure. 



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Hi Tim, I just picked up a copy of the same issue on the bay. There were 2 of them yesterday and I got one of them!

RayR posted:

… Can you amplify on the operating concept you offered?  What is the control board, where is it obtained?  Can we collaborate on a more detailed wiring scheme?

ray 15 april 2020

See if these "talking points" help.  This applies to 1 signal head controlling the track voltage to the preceding block.  Multiply accordingly based on the number of blocks (in your case 4x or 5x per loop):

[a] As I understand it, you're going to use Atlas signaling hardware.  I do not know exactly what that is so I'd need to see wiring diagrams or the like to show you how to integrate it with block voltage control.  For example, presumably there are 4-wires going to each signal head.  1 wire is common, and 1-wire each for R, Y, and G.  I'd need to know what voltages are involved; LED, bulb, DC, AC, etc.

[b] The "operating concept" is to take the Atlas signal wires going to the signal head and additionally route them to the control (relay) board as shown.  Presumably you have 2 track voltage transformers.  One is set to the full speed voltage, the other is set to the reduced speed voltage.  The relay board has 2 relays.  When a relay is ON, COM connects to NO.  When a relay is OFF, COM connects to NC. 

If the yellow signal is "ON" then the upper relay turns ON.  If the red signal is "ON" then the lower relay turns ON.  If you follow the logic, the relay module will apply FULL track voltage when the signal is Green, REDUCED track voltage when the signal is Yellow, and no track voltage when the signal is Red.

I believe early on you said you envision two transformers - one with the FULL voltage and a second with the REDUCED voltage.  Another method that has been discussed in several OGR threads is to use a single transformer with the FULL voltage...and then use diodes to lower the FULL voltage by several Volts to become the reduced voltage.  This discussion can be deferred.

[c] The relay module is widely available (eBay, Amazon, elsewhere).  If you don't mind waiting a few weeks for free shipping from Asia, a 2-relay module goes for $1-2 per relay.  These come in 1,2,4,8 and even 16 relay modules which can reduce wiring if using multiple pairs.  For example, a typical eBay listing might look like:


[d] The relay modules I'm thinking of require a DC power supply.  In this case I'm showing 12V DC relays so you'd need a 12V DC power source; this is typically done with a DC-output wall-wart...widely available or about $2-3 on eBay (free shipping from Asia).  One adapter as shown below could power dozens of relays.

12v dc output wall wart and wiring adapter

If no DC power is applied to the relay module, then both relays will be OFF and this is equivalent to a Green signal so Full voltage is applied all all blocks.  This is useful because you can then have a single toggle switch that powers all the relay modules in a loop.  By turning OFF all the relay modules you are effectively disabling block control...and the FULL track voltage is applied to the entire loop.  The signaling will still work; this mode might be useful when moving consists to and from the yard or between loops using the throttle handle assigned to FULL voltage (when in automatic).


Well, hopefully this sheds more light on the matter.  It is a lot to take in. 

As an aside, I'm thinking I'm re-inventing the wheel here!  I know lots of guys use Atlas signaling and surely someone (or Atlas themselves?) has mated signaling to block control...though perhaps not using these attractively-priced eBay relay modules.


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Last edited by stan2004

Hello Stan,

Thanks for the next level of detail and yes i do understand operation,  I am studying operation of the relay, but in general I get it.  As for track power, i would be using phased ZWs. Steve Horvath has spec'd the signal system, and he suggests you contact him for signal operation/wiring details.  His email is shorvath@atlasrr.com or phone 908-687-0880 x7142.

Whatever labor you guys want to work out is fine.  I do appreciate your help.  I have attached the block and signal schematic for your  information.  feel free to contact me as well, should you have additional questions.


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Last edited by Rich Melvin

Ray, I sent him an email same day of your previous post but never heard back. 

I'm simply asking what voltages come from the Atlas signaling system to drive the RYG signal head.  I'm assuming it's a 4-wire cable with a common and one wire for each color.  That way I can advise what (if any) additional components might be required to drive the relay modules.  What do you actually have in hand?  

Anyway, I'd like to have the information documented here on OGR so others might benefit.  As for actually building this, I think you can inquire here on OGR if there's someone in your locale that can help as this is something I'd think you want boots-on-the-ground so to speak.

*** 4/26 update: Steve responded ***

Last edited by stan2004


I have to apologize after reading your last post. When I did not see your email I checked our spam filter and saw it had been flagged. I just released it and now its MIA??,sorry. Anyway you can reach me at 908-687-0880 ext 7142. I work from home and I am available most any day or just leave me a good contact number and time to call.


Steve H

Steve, my objective is to keep this a transparent discussion to reach the widest audience rather than a backroom secret handshake exchange of information.  From what I can tell, Ray would NOT be doing the actual assembly and hence would undoubtedly refer to this thread to solicit help.

1.  What are the Atlas item numbers that you are proposing for his signaling?

2. Are you providing the signal head themselves and are these low-current LED vs. bulbs?

3. I am proposing to "tap" into the voltages going to the signal head.  Specifically, it appears from the Hump Yard Mike's above linked thread that there is a modular phone-jack connector going to the Red-Yellow-Green signal head.  What voltages are on that connector?  What is the pin-out?  Is common referenced to track outer rail?  As shown in the reverse-engineered schematic in the above linked thread, is it really "just" a 5V PIC microcontroller output pin thru a resistor?  Do you provide a breakout board to split the phone-jack output to drive multiple parallel signal heads...or in this case to steal the signals to drive relays for track voltage control?

Last edited by stan2004

Hello Steve,

Will give you a call tomorrow 4/26 to id a path forward.  My original intention is to attempt wiring myself, assuming there is sufficient granularity in the instructions which you can easily see from this thread is my intention. Of course assistance is assumed to be needed and a payout for this is expected.

Having said that, it is NOT my intention to expose or exploit the long hours some of you have expended to develop your own working system.  If your/the design is considered proprietary, perhaps a contract or non-compete could be used to assure there is no  intended exploitation/distribution of the of the build on my part.

If there is sensitivity to this, the work around is for someone to propose a fee for service to install the system, if the price is not exorbitant.

If none of these options are workable, then it may be time to fold up the tent before I invest more resources for this project.

Thanks for your thoughts,




Ray, my posts have been oriented to a DIY hobby project.  As I see it, this has morphed into a turnkey, custom-built system!  That's fine, but I think you need to find a "general contractor" so to speak...preferably somebody local to you.   If that person thinks the Lego-style eBay relay module approach is worth pursuing, I'll gladly discuss it openly here on OGR.  


Hello Stan,

I do not seek a turnkey project.  I am fully capable of building this system with minimum assistance, once the concept we have identified has been further articulated into a plan; this includes the design, critical materials needed to build it, and build instructions.  

I realize there are numerous alternatives, but we need to settle on one.  This is been proposed, including the  signaling and control board components have been identified.  What remains is the block control concept which appears to be compatible with the control board.  If this is a workable solution in your professional opinion, can we move forward with the complete solution?

It seems to me we are relatively close.  If you are comfortable with the concept and action steps, can we move forward?  If not, let's try to identify the obstacles that remain and attempt to resolve them one at a time.

Thanks again for your thoughts and effort.



Here is my suggested way forward.  Separate signaling from train control so they operate independently of each other...rather than train control being dependent on the signaling.  Here is previous diagram modified. 

signaling in parallel with train control

As shown, the automatic train control does not monitor the Red-Yellow-Green signal head to steer the appropriate track voltage.  Instead, the ATC directly monitors the insulated-rail triggers.  The ATC has access to the same information as the signaling circuit, so it can make the same decisions and effect the same track voltage control as before.  So this means you can use whatever signaling system you choose...whether it be the original 3PDT relay method, the dual SPDT relay method, or an off-the-shelf method.  In fact, you do NOT need to install signaling at all if you simply want to automatically keep multiple consists separated!

train control irrespective of signaling

The image should be click-able to get more resolution.  The ATC has the same function as before.  FULL track voltage is appled if the next two blocks are empty (GREEN), no track voltage if the next block is occupied (RED), and REDUCED track voltage if the 2nd block ahead is occupied (YELLOW).  I show 3 relay-modules for 3 blocks but replicate the hookup for additional blocks.  Since a loop, the blocks wraparound to the beginning. N blocks requires N relay modules.

On the lower left, I show a simple ON/OFF toggle switch to cut 12V DC power to the relay modules.  This turns off ATC; that is, all relays turn OFF and the "FULL" voltage is applied to all blocks. This might be useful when "manually" moving consists on or off the loop via turnouts. 

The two main components, the 12V DC wall-wart and the dual 12V SPDT relay module, were introduced earlier in this thread.


Separately, I see the JC Studio O gauge archive is back online.  As I understand it, this was source of the 3PDT relay method that Chris used; I see Leo responded in that write-up suggesting the dual SPDT method I demonstrated earlier in this thread!



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Last edited by stan2004

Hi Stan,


Thanks for stepping up with this plan.  Is there a reason you decided to omit signaling as the driver of train speed and block control?  Was this a technical issue, and what was that?  Intellectual curiosity.

I don't see input/output for the signaling on your detailed diagram.  Where are these connected to the control boards?







@RayR posted:
...Is there a reason you decided to omit signaling as the driver of train speed and block control?  Was this a technical issue, and what was that?  Intellectual curiosity.


By divorcing signaling from the block control you can use any method (3PDT like Chris, your vintage RoW signaling, dual SPDT method, custom, etc.) of signaling you desire...or no signaling at all.  And you still get the originally specified block control behavior.



Hi Stan....

I just want to confirm...in the diagram below...


the "coil" symbol shown above represents one relay. And the wiring diagram would need to be replicated for "each" coil (aka relay). So in the above example, the wiring diagram would be replicated 6 times for the 6 relays ("coils")....correct?


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Last edited by Junior
@RayR posted:

Ok, can you identify the control boards, and/or direct me to website where these can be obtained?

See my post above from 15 April 2020.

If you don't do eBay or would rather not wait for shipping from Asia, there are several sellers on Amazon for a bit more coin but presumably you'd get them faster.  For example,


For sizing the 12V DC-output adapter, plan 1 Watt for each dual-relay module.  I believe you have something like a dozen total blocks in your two loops so that would be, say, 12 Watts.  Thus a 24 Watts (12V x 2A) DC-adapter does the job.




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@Junior posted:

the "coil" symbol shown above represents one relay. And the wiring diagram would need to be replicated for "each" coil (aka relay). So in the above example, the wiring diagram would be replicated 6 times for the 6 relays ("coils")....correct?

So there's no confusion, I'll answer a different question with a visual aid. 

insulated rail 3-aspect signal

The "original" signaling circuit as implemented by Chris used one 3PDT relay per 3-aspect signal head.  I demonstrated the same functionality using two SPDT relays per 3-aspect signal head.  It's just that you can buy these relay modules with 1, 2, 4, 8, even 16 relays on one board...which can save wiring depending on your layout geometry.

If you follow some of the links to earlier threads, you will see I recommend inserting a 5-cent resistor and 10-cent capacitor on each input to the relay.  This helps demote signal light flickering or relay chatter when a consist enters or exits the insulated-rail section and there's only one or a few axles on possibly dirty track and wheels.  If you have clean track/wheels and don't care about occasionaly flickering, then you can skip the resistor-capacitor combo and directly wire from the insulated-rail section to the relay input.

Note that for the eBay relay modules shown above, you do not actually directly drive the relay coil.  If you are not using these relay modules, but instead directly driving a 12V DC relay coil, then let me know which relay you have and I might have more to say!

Also, as drawn in this diagram and the diagram you reference, I'm assuming a so-called "common-anode" LED-style signal head.  Shown above is a signal head photo from eBay seller "we honest" who has been discussed many times over the years for their attractively priced O gauge signals and accessories. Their common-anode 4-wire RYG signal comes with a resistor so you can directly drive them with 12V DC.  


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Last edited by stan2004

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