Wednesday, December 24, 2014


As I have mentioned on and off in past posts, I've been working on installing operating signals on a portion of the layout. Over the past several weeks, the last pieces have come together and the system is now working. I'm using the Signals By Spreadsheet (SBS) hardware and software and I'll provide some more detail on this later. I'm also using the signal aspects and indications used by the Chesapeake and Ohio Railway and there will be some more information on that later as well.

The goal is to eventually have full CTC control of the railroad from a remote dispatcher's panel and I've built the signals with that in mind. Fortunately, the SBS system is designed so that you can get bi-directional automatic block signals (ABS) up and running prior to developing the CTC system. This allows you to establish all of the required blocks and corresponding detection, get the signals built and in place, and develop the programming of the signals in steps. Gerry Albers, who developed and markets the SBS product, strongly recommended that I get all of the detection in place and the signals working before starting on CTC. Getting the bi-directional ABS system up and working is a  tremendous amount of work and there's much to be learned in the process that will aid the development of the CTC system later. It should be noted that bi-directional ABS must be overlaid with a traffic control system such as time table and train orders or track warrants in order to provide conflict free movement authority. Thus we will continue to use track warrants until the full CTC system is up and running.

The section of the railroad that is now under ABS runs from Petersburg Junction to Cedar Falls Junction. This area includes Big Chimney, WV and the passing siding there along with the Purgittsville Branch and the Elkwater Branch. Let's take a quick look at this area.

Looking east toward Big Chimney, we see the signal at Petersburg Junction controlling the Purgittsville Branch in the foreground and the signal controlling the eastbound entrance to the passing siding at Big Chimney in the background. Here's a link to the track plan so that you can follow along: Note that there are no westbound movements approaching this section of the railroad as indicated by the Clear aspects. Also note the signal on the Sand Fork Branch which is displaying a Restricting aspect. This is the first of two signals on the branch before the connection with the main at Cedar Falls Junction.

Looking back west at Petersburg Junction, we see that the turnout is thrown for the main and the line is clear.

At the west end of Big Chimney, we see the signal governing westbound movements at the west end of the passing siding. Note the Stop aspect for the siding as the turnout at the west end is lined for the main.

Looking at the east end of Big Chimney we see that the turnout is lined for the main and there are no movements in the area as indicated by the Clear aspect.

The signal governing the westbound approach to the east end of Big Chimney also shows Clear.

So here's some video of the system in action. My apologies for the small size of the screen and the noisy Tortoises. Here's a link to larger versions of the videos which are posted on YouTube: There is a local moving west and a way freight heading east toward Big Chimney. The dispatcher wants to arrange a meet there and have the local take the siding. He throws the switch for the local to take the siding at the east end of Big Chimney.

As the switch is thrown to the siding on the east end, the westbound signal drops to Approach indicating to the approaching local that the next signal will be Stop. The turnout at the west end of Big Chimney is lined for the main and the local will face a Stop signal at the end of the siding. As the local enters the block before the turnout, the eastbound signal on the siding drops to Stop. If there had been a train in the siding when the turnout was thrown for the siding, the westbound signal would have dropped to Stop.

Now the local comes down the hill from Cedar Falls Junction and heads toward the siding at Big Chimney.

As the locals moves into the clear in the siding, the dispatcher throws the turnout at the east end back for the main. The signal for the eastbound main now shows Clear for the approaching eastbound way freight. The momentary Clear signal eastbound from the siding in this short clip came about as the caboose cleared the block that contains the turnout. As there are no westbound movements in the blocks behind the local, the eastbound signal from the siding would show Clear as long as the turnout remained lined for the siding.

Next time, we'll watch as the eastbound way freight approaches the local in the siding at Big Chimney. Until then, here's wishing you a very Merry Christmas!


  1. Would really like to see the nuts & bolts of the signal system Tom, as I'm working through the installation of our LocoNet I've become really interested in how these systems work. Are you using speed or direction orientated signalling?
    The JL&T is using speed orientated, with mainly searchlights (both mast & dwarfs) and with a few tri-light masts too.

  2. Jas,

    I'm using speed and direction. Without getting into too much detail, the signals are set up primarily to convey the track conditions ahead (occupancy) and speed. In several instances, I've employed an aspect to indicate that a power operated turnout has been lined for either a diverging route or non-diverging route and the speed with which the trains should proceed through that turnout and beyond. I'm not going to use three headed signals, so my ability to convey route is somewhat limited.

    Here's a link to Mike Burgett's Control Train Components website. It has one of the best descriptions I've ever found of CTC and signalling in general:

    I'll pass along some more information to you about how this system works in a separate e-mail.

    Merry Christmas!


  3. Thanks Tom for the link, I'll have a look at that tonight. Always interested to see anything about signals/aspects and how they operate, it's a fascinating subject how they work