Installing working signals on a model railroad can add so much to the operating realism. There are so many different ways to do it, because each of the real railroads did it differently. You can control your signals manually with a CTC control or automatically with ABS signaling. 

The NNRR Co uses a lot of different signaling to monitor the movement of trains, and to control the movement of the trains. First off, lets show what type of signals I use.  

Signaling on the N&N RR - Double Track Automatic Block Signaling

Once I had reached the stage where DCC System tied to the layout and operational, I saw a need to use an extensive signaling system.  because I did not want to tie the whole thing into the DCC itself.  So I embarked on a massive quest to make it was a totally independent System.

This was due to the fact that there are many blocks. As a result, one could not tell what was ahead unless there was a visual indication.  It is based on the PRR / B&O dual track standard, except that both mainlines are signaled bi-directional. Not all the signals are in yet, but more than 30 of them are.

Because of the huge quantity of signals needed (70+), I am building most of our own from scratch, using materials from a variety of suppliers. I also found that a number of situations required custom signals not commercially available. You can't find a working quad track bi-directional signal bridge anywhere, as was needed in several locations.  Some of these signals may seem a little larger than what it should be, but it is close to the scale, so I used the brass heads.

I am using NEC / Lenz block signal controls. They, in turn, connected to the Feedback System, are given commands from the system. The Lenz system gets information from block detectors and turnouts around the layout.  based on block occupancy and turnout position. Then will stop a train from entering the occupied block, and or bridge up situation.

Originally, I set it up using four aspects (Red, Yellow, Flashing Yellow, Green) for all signals. That way, to get a Green signal, at least three blocks ahead of a train had to be clear. Since then I decided to change it to three aspects, reserving the Flashing Yellow for only special situations such as a crossover ahead is thrown, a train is about to take a siding, or a train is about to enter a reverse loop.

I still am re-building the layout, re-doing the yards due to the fact I have a massive amount of rolling stock, and no real place to put it all.  So the Signaling System in the yard operations will be a simple switch dependant system. as shown below...