Ballari Jn - Look around and enjoy the station. A sacred place where Mahatma Gandhi once spent 8 hours. - Vishwanath Joshi

In railway signalling, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings. The signalling appliances and tracks are sometimes collectively referred to as an interlocking plant. An interlocking is designed so that it is impossible to give clear signals to trains unless the route to be used is proved to be safe.
A minimal interlocking consists of signals, but usually includes additional appliances like switches , derails, crossings at grade and movable bridges. Some of the fundamental principles of interlocking include:
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may not be operated to permit conflicting train movements to take place at the same time.
Switches and other appliances in the route must be properly 'set' (in position) before a signal may allow train movements to enter that route.
Once a route is set and a train is given a signal to proceed over that route, all switches and other movable appliances in the route are locked in position until either
the train passes out of the portion of the route affected, or
the signal to proceed is withdrawn and sufficient time has passed to ensure that a train approaching that signal has had opportunity to come to a stop before passing the signal.