Chain signals?

[Rahjital]

Would any kind soul here be willing to explain how chain signals work, how are they different from regular signals and what are their uses? Are they simply regular signals that also need the following block free to turn green, or is their function more complicated?

[Yttrium]

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[FishSandwich]

I've been experimenting a couple hours with these guys.

One use I have found for them so far, is getting trains to wait in more convenient places, for example: http://i.imgur.com/C2n7aeD.png

In the picture, T1 wants to go to the station that T2 has stopped at, but can't, so waits at CS. Without the CS, T1 would normally go and wait at S, completely blocking the other 2 rails. With the CS, he waits out of the way and the other two rails are free for other trains to run through.

[FishSandwich]

An explanation on what they do, from what I can tell:

Chain signals read rail signals that are in the blocks ahead of them. They have 3 color settings; green, blue, and red.

If all rail signals in the blocks ahead of a chain signal are green, the chain signal will display green and will allow trains to go through.
If rail signals in the blocks ahead of a chain signal are a mix of green and red, the chain signal will display as blue and will allow trains through as long as their path leads to a green rail signal.
If all rail signals in the blocks ahead of a chain signal are red, the chain signal will display red and will not allow trains to go through.

[Tallinu]

That's a really excellent breakdown of their behavior, I don't think I could've explained it quite that clearly. I would add, however, that chain signals will "chain" their search through other chain signals until they reach a normal signal - if a chain signal can lead to a blue chain signal, it will also be blue, for example.

Anywhere you have rails crossing paths in such a way that one train could end up blocking another if it stops at the wrong signal, you can use a chain signal just before that to make the train wait prior to entering the block(s) in which the rails cross. It's perfect for multi-direction intersections, and even the most basic 3-way T junction can benefit from them in the right places.

[ratchetfreak]

Maybe the most intuitive way of deciding where to put chains is to first put all normals and for each signal that you don't want a train to wait at; go backwards and replace the signals coming in with chains. Repeat for each signal.