types "B" & "S", and the General Railway Signal Company's universal Model 2A mechanisms, manual semaphores and earlier electric disc signals quickly began to disappear.

Form

Components

The British semaphore signal arm consists of two parts: A wooden or metal arm (or "blade") which pivots at different angles, and a spectacle holding coloured lenses which move in front of a lamp in order to provide indications at night. Usually these were combined into a single frame, though in some types (e.g.

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