Past the Stair
I have blogged before about the Monticello Railway Museum, one of our local hidden treasures. A couple of years back they completed a project to build a replica interlocking tower, named for Richard P. Stair, a now-deceased long-time volunteer. It contains two different styles of original Illinois Central interlocking machines, salvaged from Gibson City, IL and Tuscola, IL.
On some weekends you can get a tour of the interlocking tower, where one of the volunteers will explain how the system works. An interlocking machine is really a kind of analog computer, with connections between the levers that will move multiple switches to guarantee that two trains do not attempt to occupy the same segment of track at the same time. The volunteers, many of whom used to work for various railroads, will also be happy to tell you that the Stair Tower is much too clean and much too comfortable, a dandified version of the dirty and drafty places they used to work. 🙂