Mechanical interlocking towers were an integral part of mainline railroading in the late 19th and early 20th centuries.
This presentation will review some early developments in the history of interlocking machines and describe the basic concepts involved in designing an interlocking scheme. Rich will describe his explorations of the New Haven Railroad Signal Station 44 interlocking infrastructure, as preserved in the South Norwalk (SONO) Tower Museum, and will review the development of a scale model of a simple interlocking plant intended to illustrate these concepts to museum visitors.