Why there is 'X' sign on the back of the last train car/coach?

For all of us, "Indian railway" is a very useful thing. We often notice many things while traveling from the railway.

Have u noticed the 'Cross' (X) on the last coach/box of the railway in a station?

Yes, you are right....This cross "X" mark indicates that this is the last coach/box of the railway. 

Except this cross 'X', 2 letters as "LV" in English are also seen on the last box of each railway. (LV means Last Vehicle) 

And at night, we see a red light blinking on the last coach.

According to the rules of railways, it is mandatory to have these things on the last box. Typically all these signs are there to show the end of the rail. These signs are not registered on any other coaches of the railway. The only purpose here is to show that the rail ends here.

It is important for the safety of the train to know that the train ends here. The controller signals when a rail goes from that station, If the last box of the rail have not mentioned above marks, it means that the whole train have not been admitted to the station.

Due to technical reasons, some coaches of the trains can be seperated from other coaches. In such a situation, if some coaches are separated from the railway, this cross 'X' sign helps the controller so he can take immediate steps. If some of the rail coaches are separated, then they are likely to be stuck in the 'block sections' coming between the stations. There is possibility of accident with the next train running on that route.

Therefore, the station controller and signal cabin controller confirms that the entire train had gone from the station. At the time of the day, this 'cross' sign and at night shining red lamp indicates that all the coaches of the trains are safe and intact.