Signals on the Kansas City Subdivision

Part 1 - Research  Part 2 - Design   Part 3 - Logic

Updated 1 October 2008

The beginning

There was no doubt about it, I wanted working signals on my model railroad. Where to start? What to do? Many questions presented themselves. So I began a brainstorming phase where I thought about the kind of signals that I wanted.

Turn back the clock about 26 years - I was working for the Milwaukee Road in Kansas City, as one of the tower operators at West Wye Tower. West Wye Tower controlled a double-track wye connecting the Milwaukee Road, Kansas City Southern and Rock Island (soon to become the Chicago and Northwestern).

West Wye Tower contained a Union Switch & Signal 'Direct Wire' control machine. West Wye Control Machine

The machine lasted into the 1990's when it was decommissioned and replaced by remote control between the Drawbridge operator and the Kansas City Terminal control operator. Until that time, it directly controlled the junction. The system I designed incorporates similar functionality to the US&S machine.

How did the US&S machine work?

There is a track diagram, with red lamps that illuminate when a train is 'in the circuit', two rows of little 'lever' switches with coloured lamps over them. Behind the levers were pie wedge shaped plates with numbers. Switch Lever Plate Signal Lever Plate

The number on the plate designated which switch or signal was controlled by that lever. These levers operated the corresponding switch or signal immediately if it was safe to do so. For example, clearing a Milwaukee train out of town over the Drawbridge.

This was feedback for the operator, to tell them that 36R was clear and that the train could move up to Freight Line Junction. While signal 36R was cleared or there was a train standing on the track, switch 35 would remain locked. Any movements of the lever for switch 35 would be ignored by the machine.

The West Wye interlocking machine worked differently to a CTC machine. CTC machines sent out a coded message on the communications line to remote locations. The remote control point worked out the logic of the request and sent back confirmation (via coded message) to the CTC control panel.

USS Searchlight type H Prototype Signal model signal Model Signal

The signals used at West Wye Tower, and all of the Milwaukee Road mainline up to Laredo Missouri were Union Switch & Signal H Dwarf signals and H series Searchlight signals.

System Requirements

The system needed to:-

The first stop on the research trail was Mike Burgett's CTC web site. Unfortunately, this site is currently under reconstruction. This is an excellent reference for anyone wishing to research a Signal System. On this web site you can learn about CTC Signalling and find links to other web sites about system hardware, signals and software.

Design considerations

I considered a few other possibilities, such as:-

I investigated some of the commercial signal system offerings.

Signal Components and Systems Investigation

Atlas signal system

( - This product was announced in 2006 and provides realistic signaling.

I found that the Atlas offering was good if you wanted simple block signals, however I needed more realism and control since my track plan consisted of more complex junctions than the Atlas system could cater for.

The Atlas signals also were not applicable to my prototype. They would serve NYC modelers well. The Rock Island also had this style (Type G) signals on the line from Polo, Missouri to Des Moines, Iowa.

Digitrax Signal System

( - The Digitrax offering had been around for a while and looks very good. The drawbacks for me were that they only offer colour light signals and not searchlight. I spent a lot of time reading all of the Digitrax documentation and concluded that it was a good flexible system, however I would need to use LocoNet to hook it all together and there did not seem to be an easy way to use other products in conjunction with the Digitrax system.

TracTronics Components

(( - TracTronics offers circuit boards and designs to implement signaling, but this also was very 'homebrew' and did not look like a full integrated system. This would be great for 'do-it-yourself' approach where you would like to save a few dollars.

JLC Enterprises C/MRI

( - I had not heard of this product before the series of signaling articles appeared in Model Railroader magazine, starting with the January 2004 issue. C/MRI stands for Computer / Model Railroad Interface.

This system was designed by Dr. Bruce Chubb, MMR. It was designed many years ago and has matured into a very flexible system. C/MRI is made up of various components, particularly Nodes which can have many connections on them. These connections can control switch machines, signals and they can read the state of turnouts and blocks using different sensors.

This system offers the greatest flexibilty and is easy to change through programming. Once you have wired it up, you do not need to re-wire if you need to change the logic.

Next - Design