A specialized, often elevated building located at complex junctions where an operator manually controlled switches and signals. The ground floor typically housed the mechanical locking bed, while the upper floor contained the lever frame and track diagram. Most have been replaced by centralized dispatching, but the term survives to describe the control point itself.
The old interlocking tower at the diamond was torn down when they cut over the new CTC system.
Related terms
Interlocking
An arrangement of signals and switches interconnected to prevent conflicting train movements.
Lever frame
A mechanical assembly of large handles used to manually operate switches and signals.
Locking room
The ground-floor space of an interlocking tower that houses the mechanical interlocking apparatus.
Signal box
A traditional building from which switches and signals are controlled.