When operating trains or shunting cars, there are many conditions to be understood, such as whether the route is open in the correct direction, whether there is sufficient headway with the preceding train, and whether the train may be started, etc. These conditions are conveyed by railway signal devices through a combination of shapes, colors, and sounds, etc.
These signals are used to allow people to judge train operation and car shunting conditions according to fixed rules, and are therefore set to facilitate handling and prevent misreading of signals.
Signal devices are divided into signals to indicate conditions for train or car operation, signs for workers to communicate with each other, and markers to indicate object location, direction, conditions, etc. The main types of signal devices are listed below, but multiple color light signals are predominate.
(1) Signaling system
There are two main signaling systems: "two position signal" and "three position signal".
The two position signal system signals by two positions (horizontal and 45 degrees) of the arm of the semaphore signal and a set of lights of the position light signal, and also by red and green (orange and green of subsidiary signals) of the color light signal.
