Portal:Trains/Featured picture/Week 7, 2006

The interlocking mechanism in Deval Tower at Des Plaines, Illinois.

In mechanical interlocking plants, a locking bed is constructed, consisting of steel bars forming a grid. The control levers that operate switches, derails, signals or other appliances are connected to the bars running in one direction. The bars are constructed so that, if the function controlled by a given lever conflicts with that controlled by another lever, mechanical interference is set up in the cross locking between the two bars, in turn preventing the conflicting lever movement from being made.

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