Indian Signaling Systems
Indian Railways is the national rail transportation service of India. It utilizes a signaling system similar to that employed by trains in the United States.
Among the oldest railroad signaling systems in the world, semaphores are popular in areas of India not subject to an overabundance of rail traffic. These types of signals use a rotating arm with a colored lens attached, which moves in front of a lamp and illuminates a particular color signal easily seen by a railroad conductor aboard a train. These signals utilize anywhere from two to four colors, based on traffic, to indicate to the conductor whether he must stop his train, whether there are situations to be cautious of on the track ahead or whether it is safe to proceed.
Electrical signaling and switches
Multiple aspect lighting is based on the same principles as semaphore signals; it employs two to four colors of lighting to alert the conductor to conditions further down the track. In its simplest form, used many places in India, multiple aspect lighting indicates an "on," which is a condition where the moving train must stop, or a "clear," which tells the conductor to proceed at safe speed. In high-traffic areas, more complex electrical signals are also connected to switches which can change the path of a train dependent on conditions ahead. Multiple aspect signals are an efficient way to alert the conductor of any encumbrances further ahead and to tell him which speed is best.
The signaling systems used by India Railways are nearly identical to those used elsewhere in the world. This commonality makes trains safer.