What are the systems of semaphore signalling used by IR?
Lower Quadrant In IR’s lower quadrant system the semaphore arm can only be in two positions. The horizontal on position shows the most restrictive indication (requiring the train to stop or slow down or proceed with caution depending on the kind of signal), and a lowered position where the semaphore arm is at about 60 degrees or more from the horizontal shows the clear or proceed indication allowing a train to go past the signal. IR actually has two kinds of lower-quadrant semaphore signalling, which are the Two-aspect Lower Quadrant and the Modified Lower Quadrant systems. The difference between them lies in the kinds of signals used, as explained later in this section. MLQ is found in the Kharagpur-Vishakhapatnam and other sections. The lower quadrant system suffers from a potentially dangerous flaw, which is that in case of a mechanical failure, the semaphore arm is likely to drop by gravity into the clear position; note that in the upper quadrant system a failure is more likely to
Lower Quadrant In IR’s lower quadrant system (Two-aspect Lower Quadrant) the semaphore arm can only be in two positions. The horizontal on position shows the most restrictive indication (requiring the train to stop or slow down or proceed with caution depending on the kind of signal), and a lowered position where the semaphore arm is at about 60 degrees or more from the horizontal shows the clear or proceed indication allowing a train to go past the signal. The 2-aspect Lower Quadrant system suffers from a couple of disadvantages. The principal disadvantage is that the driver of a train must be prepared to bring the train to a full stop when the warner is at caution and the home signal is at danger. To address this, often warner signals are moved further back to provide sufficient distance from the home signal for braking the train to a full stop. The second disadvantage with the 2LQ system is that the indication of the warner signal is not explicit. When the warner is at caution, it m
