Railway semaphore signal
One of the earliest forms of fixed railway signal is the semaphore. These signals display their different indications to train drivers by changing the angle of inclination of a pivoted 'arm'.
Railway Semaphore Signal Media
German semaphore distant (left) and home (right) signal exhibition in Steinfurt, Germany
Upper quadrant signal on the Santa Fe Railroad, 1943. The vertical position indicates a "clear" aspect.
Lower quadrant stop signals at St. Erth in 2007
Somersault signals at Carrickfergus railway station, showing the distinctive central pivot about which the arm "somersaults"
Semaphore signal levers inside train dispatcher's room of Cianjur railway station. These levers are connected to the signal by pairs of wires.