# Kato trackside signal



## vette-kid (May 2, 2020)

What the purpose for this signal. The signal illuminates right next to the sensor, so it would only be visible to the train that is detected? An I missing something? Seems you would want the sensor in one spot and the signal somewhere else. For example, near a turnout where two trails join to give one direction the right of way. What purpose did having them Co located serve?

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## traction fan (Oct 5, 2014)

vette-kid said:


> What the purpose for this signal. The signal illuminates right next to the sensor, so it would only be visible to the train that is detected? An I missing something? Seems you would want the sensor in one spot and the signal somewhere else. For example, near a turnout where two trails join to give one direction the right of way. What purpose did having them Co located serve?
> 
> Sent from my SM-G781U using Tapatalk


vette-kid;

I don't have a Kato signal, but some model signals are designed more for an easy way to get lights to change, than they are for realistic operation. Short answer, you are correct, to do any real good, the sensor and the signal should indeed be in separate locations.

The subject of prototype signaling practice is a very complicated one. The following is an extremely simplified explanation suitable for signals on a model railroad.

There are two general classes of signals on railroads.

"Block Signals" which indicate the presence of a train in the next "block" or section of track, beyond the signal, with a red light (stop) If the block immediately beyond the signal is empty, but there is a train in the second block beyond the signal, will show as a yellow light. (reduce to minimum speed prepared to stop at next signal) 
If there is no train in either of the two blocks beyond the signal, it will show a green light.

"Interlocking signals" function somewhat like traffic lights on city streets. The green light is only given to one of the possible routes through an "interlocking" (intersection) of track that may contain a crossing, or turnouts, passing sidings, or some combination of these elements.
Like a street intersection, it would be dangerous for two routes to be open for travel at the same time. This type of signal could be used in your turnout route indicator example. From the point end of the turnout, set for the main line, the signal would show green. If the turnout were switched to the diverging route, the signal would change to yellow. At the frog end of the turnout, The signal could be red if the points were set the wrong way, and green if the points were set for the route of your approach.

John Armstrong wrote a short book on signals, prototype & model, years ago. It was titled "All about signals." There are also several other, more recent books on signaling available.

Traction Fan 🙂


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## vette-kid (May 2, 2020)

Thanks TF, that's kind of how I thought they were supposed to work. The kato signal just seems like a simple way to get something to light up on your layout, but not really useful. I'd be happy if they were separate, but really prototypical, but just to indicate the presence of another train on the converging track that will signal the other line to wait. Very basic, but at least had a use. 

Kato Automatic 3-Color Signal N Scale Model Railroad Trackside Accessory #20605 

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## ftauss (Sep 18, 2012)

I saw that and was ready to buy it but then I watched a video. It is always green on approach, turns red as the loco passes and turns green shortly after the last car passes. Seems very not useful. I think in 3 rail, which I also have, if you put you signal before the block that had one of the outside rails insulated in the block you could use that to indicate red for that block, I guess you could go further and do the same thing for the 2nd bock to light up a yellow.


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## vette-kid (May 2, 2020)

I wander if you could somehow cut the signal off and relocate it? Might have to solder some wires and hide the spot on the plastic where it's connected. I like the activation switch, seems cleaner than some of the other options. Hmmm


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## traction fan (Oct 5, 2014)

ftauss said:


> I saw that and was ready to buy it but then I watched a video. It is always green on approach, turns red as the loco passes and turns green shortly after the last car passes. Seems very not useful. I think in 3 rail, which I also have, if you put you signal before the block that had one of the outside rails insulated in the block you could use that to indicate red for that block, I guess you could go further and do the same thing for the 2nd bock to light up a yellow.


Yes, that's one of the advantages of 3-rail. You are essentially duplicating the basic sensing method of the "track circuit" used on the prototype. The wheels short the two (outer on a 3 rail layout) rails and trigger the signal. There are electronic "block occupancy sensors" that can perform the same function on a 2-rail layout.

Traction Fan


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## traction fan (Oct 5, 2014)

vette-kid said:


> I wander if you could somehow cut the signal off and relocate it? Might have to solder some wires and hide the spot on the plastic where it's connected. I like the activation switch, seems cleaner than some of the other options. Hmmm
> 
> 
> Sent from my SM-G781U using Tapatalk


vette-kid;

I think you would be better off using some of the other, separate, sensors and signals available. A google search for "block occupancy detectors" should show you what's available. Likewise a search for "N-scale model railroad signals."

Traction Fan


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## cv_acr (Oct 28, 2011)

[proper] Signalling is a complicated affair.

In a sense, [a] sensor should be next to the signal, as it's correct for a signal to "knock down" from green ("Clear") to red ("Stop") as the train passes it. Of course in real life, the signal would stay red if there's a train past it, and not go back to green when the last car clears. Real signal systems detect an entire "block" of train, and not just point sources.

This is before you get into turnouts and speed vs. route signal indications...

The simple sensor is nothing more than a simple animator; it can't realistically reproduce the behaviour of a signal. That gets into some pretty involved wiring and logic work.


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## cv_acr (Oct 28, 2011)

traction fan said:


> Yes, that's one of the advantages of 3-rail. You are essentially duplicating the basic sensing method of the "track circuit" used on the prototype. The wheels short the two (outer on a 3 rail layout) rails and trigger the signal. There are electronic "block occupancy sensors" that can perform the same function on a 2-rail layout.
> 
> Traction Fan


If I understand 3-rail wiring, the two outside rails are the same polarity, and the middle rail is the opposite. Nothing will ever "short" across the outside rails if they're same.


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## traction fan (Oct 5, 2014)

cv_acr said:


> If I understand 3-rail wiring, the two outside rails are the same polarity, and the middle rail is the opposite. Nothing will ever "short" across the outside rails if they're same.


cv_acr;

Actually, if you've ever done any "electron chasing" through some wiring done by another person, you have probably discovered that it is quite possible, and often very frustrating, to have more than one short in a circuit. So, technically speaking, something could indeed short across the outside rails of three-rail track, even though they're already shorted. What wouldn't happen is any change in polarity or voltage level, which of course is what you're pointing out. Enough with the arcane theory & semantics. Here is how three-rail detection can work.
The center rail is the incoming power, and both the outside rails are used as power returns. Yes, you're right that normally the two outside rails are the same polarity, & voltage. However, what the three-rail guys do is to insulate one of the outer rails on a section of track that will be used to trigger for a signal. Then when a train enters that track section, the insulated rail is shorted to the other outside rail, by the wheels of the train.

Unlike two-rail model trains, (but like prototype trains) the model three-rail variety has metal wheels connected both physically, and electrically, to a metal axle, and through that to each other. In two-rail this would be very bad, since it would short out the power in the track.
Since three-rail only draws power from the center rail, It doesn't matter if there is a short between the two outside rails. In fact, they are normally shorted to each other all the time, if the track is the old tubular rail type with metal ties.*
The center rail of this track is isolated from the metal ties, and the two outer rails, by cardboard insulator shims between the ties and the center rail. To construct a trigger section one outside rail would also need to be insulated from any metal ties and insulated "rail Joiners" (wood or plastic pins) would be installed at both ends of the trigger section of rail.

This arrangement is similar to the most basic form of prototype train detection. They also install insulated rail joiners (big ones) to electrically isolate a length of rail from the rest of the main line, in the approaches to, and the rails of, a grade crossing. The train's wheels short that isolated rail when the train is approaching the crossing. This triggers the flashing lights, bell & gates. The gates stay down and the lights & bell stay on until the last car has left the isolated rail, beyond the crossing.
I watched an interesting you tube video by "Distant Signal Productions" on this subject. The prototype often uses modern electronics to adapt the triggering process to specific situations. For instance, when a train must stop and linger near a crossing, the systems can turn off the lights, bells & gates to give motorists a break.

Traction Fan 🙂 

* Newer three-rail track, like Lionel's "Fast Track" may not have the two outer rails shorted. I don't know since I use two-rail (N-scale) I'll leave any explanation of newer three-rail track to the O-scale modelers who use it.


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