Trying to grasp the aspect and placement of B&O signals. I’m intending on using these signals on my layout, however, the reasoning for two of every color on the head is because of “the twoblock system”, I assume? I guess the first set of lights is for the first block, right after the signal, and the second set for the second block. Now, what if there is a track switch in between, does it get its own signal and if so would it be different than the other? I’m sure the information that Im looking for is way to involved for a blog, just a start on this topic would be great.
I don’t plan on having 100% prototypical signaling on my layout, but i would like something close. Thank you for any help.
The placement of the signals would be pretty much the same as any other system of the same type (ABS or CTC).
The signals are a mix of single head and multiple head signals. Normally the multiple head signals are used when there is some change of route or speed, such as at an interlocking.
The heads do not have anything to do with the number of block or whatever. The combination of colors and heads indicate the speed and how the train proceeds beyond the signal.
If you searched for “CPL signals” you would probably find a lot more information on the B&O Color Position Light (CPL) signal systems.
As for what you are trying to do, you should describe what you are planning to set up in more detail. An ABS (Automatic Block System) system is where the signal system is totally automatic and only the switches and signals inside of manual interlockings are controlled by an operator or dispatcher. A CTC (Centralized Traffic Control) system is where the switches at junctions and sidings are controlled by the dispatcher or operator. An interlocking is a location where the switches and signals are controlled by an operator or dispatcher.
If you are just going to use them as switch point indicators then you really don’t have to worry too much about what the prototype does, because you won’t be doing that anyway.
Generally, two or more heads indicates the signal is part of an interlocking. The name “Interlocking” came from the days of manual levers controlling turnouts and signals from a tower. The lever apparatus was “interlocked” so that you could only clear one route at a time. Like at a spot where two railroads crossed each other at grade, the signals could be set so one railroad had a clear signal and the other railroad had to stop - it wasn’t physically possible to accidently set the signals for both tracks to clear.
If you think of yourself riding the cab of a train on the mainline, coming to a spot where a branch line splits from the main. Generally you’d have a two-headed signal near the turnout. Green-over-Red means you’re continuing on the mainline. Red-over-Green means you’re going onto the branchline. Red-over-Red would mean “STOP” as the block ahead wasn’t clear. It’s a little like traffic signals, where you might have the signal for the main street on red, but the left turn lane signal would be green - or vice versa - only instead the signals being side-by-side, they’re one on top of the other (mainline on top, branch line below).
There’s also the point that color-position-light signals are supposed to reproduce the aspects of upper-quadrant semaphores without the semaphores’ moving parts. Thus two horizontal red lights indicate stop, two diagonal yellow lights indicate restricted speed, and two vertical green lights indicate clear. If any light in a color pair burns out, the color of the remaining light still gives the desired indication.
(That’s why the Pennsylvania RR position-light signals had three lights per aspect, so that if any one light was out the other two still appeared in a horizontal, diagonal, or vertical pattern.)
Yes, single head signals (like the first two links) can be “permissive” or “absolute” - some roads said a signal was absolute unless marked with a “P” for permissive, some said signals were permissive unless marked with an “A” for absolute. (Some used a mileage marker as the indicator. But multiple head indications (like the lower link) are virtually always an absolute stop. That’s why at like a grade crossing of two rail lines (with no connections between the two) you might see a ‘dummy’ lower head that always showed red, so the signals would be green over red (proceed) or red over red (stop). It makes it clear that no matter what, this really does mean STOP!! [:)]
Larry, taken in the context of everything he wrote, STIX was clearly refering to an Interlocking signal - Rule B-292 STOP.
I have found it much more usefull and interesting in modeling signal systems to focus on modeling Interlocking signals with little or no concern for permisive block signals.
Even on the largest “basement empires” the distance between interlockings seldom justifies any block signals. So full working interlocking sginals, with correct approach signals is both useful and much easier to impliment, be it CTC or ABS.
To the OP, B&O position light signaling is complex to say the least, you would be well served to research it more before even making a final decission to use it.
Larry, that’s fine, but you made it sound like Stix was wrong, in the context of what he was saying he was not wrong.
Permissive signaling can be done/used in DC as well, electrical “sections” just need to be shorter than signal “blocks”. But DCC or DC, few have layouts that big or with that much trackage between interlockings for that to have any function or meaning.
I agree those truely interested in signaling are well advised to understand the prototype as well as possible, but as a practical matter, interlocking signals are much more important on our selectively compressed model layouts.
Are you not one of those who constantly challenge me on te issue of how many people have “basement empires”? It takes a “basement mega empire” to put permissive signaling to work in more than one or two locations.
Even on my 8 scale mile long double track mainline I have eight interlockings and only one area with any block signals between interlockings. Since train lengths typically approach 40 cars (about 20’) and a scale mile is 60’, what would be the point of signal blocks any shorter than several train lengths in open running country? Even with DCC I would not want trains following that close together.
That’s exactly why I told him not to get too hung up on the prototype signaling, because he won’t be installing signals “prototypically”. And if he wants to use them purely as switch indicators it will be even further from the prototype.
The OP needs to provide more information on his intents or possibly his track plans to give more specific information.
Again, there are still some subtleties, depending on the rules you’re using.
From the old 1962 UCOR used by Canadian roads:
291 Stop and Proceed (note the staggered two-head signal)
292 Stop
A further modification introduced later and now used on pretty much every intermediate signal is the addition of a square yellow plate with a black “R” that turns a 291 Stop and Proceed into a Restricting signal.
Of course, this is a little off-topic, since that’s not the rules the original poster would be using even if he’s going to try to do actual prototype signals…
Wow, this blog really blew up, but thanks. I have done some reading over the last few days, basicly I was trying to get a better understanding of the CPL’s so I could make and educated decision on where they should go on my layout. As I had allready thought it would be a little impractical to place signals on a ABS type set-up as well as for turnout position you would need signals everywhere and a seperate booster to power them all. Not to mention the sytem I was planning on going with is the Block and Signal animator from LogicRail, with this signaling system I would need photocells all over the place.
I’m aware that nothing I use will be 100% prototypical and thats fine. I merely wanted to understand the signal head and the markers, and I think I have a pretty good understanding. Although when the track comes to an interlock ex. a siding, there would need to be a second signal head for that route I assume. That signal head would typically be a two position type signal, yellow and red, I think.
As far as the markers above and below the head, only indicate speeds for that block. Upper markers are a speed upgrade and lower markers are a downgrade in speed. This is how I’m understanding the signals thus far, I may be very wrong and if I am I hopping someone can correct me. Thank you for all the great info it really helps.
