Stellwerke

Stellwerke are railway signaling and interlocking facilities that control railway signals and track switches to ensure safe train movements. They implement the route setting and locking logic that prevents conflicting movements and enables trains to proceed along approved routes.

Historically, Stellwerke were mechanical devices: a frame of levers connected to signals and points; pulling a lever not only set a route but also locked other levers to prevent unsafe configurations. As traffic grew, electromechanical interlockings added electrical actuation and logic circuits, maintaining mechanical interlocking with electrical components. In modern networks, electronic or computer-based Stellwerke (Elektronische Stellwerke) control large areas from central locations, communicating with trackside devices.

A typical Stellwerk comprises a control building, a diagram or panel showing the line, a set of levers or input devices, signaling equipment, and the interlocking logic that enforces safety constraints. Operators set routes by selecting it on the panel; the interlocking verifies that points are correct and provides corresponding signal indications. If a route is unsafe or a conflicting route exists, the system prevents it.

In recent decades, many mechanical and electromechanical Stellwerke have been replaced by electronic interlockings or centralized control systems, often integrated with modern communications and signaling standards. On some heritage lines, functional mechanical Stellwerke are retained as historical equipment.