@Manish*: Re# 136920-0
If it is train between different zones it is easy to identify with the train number which indicates the zone to which the train belongs. Train leaving zone is up and train returning is down.
Actually though up is meant going from primary maintainence and down is for getting bank and up train must have the preceeding number(i.e up train 1 and down train 2) but majority cases it isnt the case.