No.6 lever in the centre is the master lever of the ground frame.It has a lock which is unlocked by a key issued by the Station Master.Once the key is inserted and turned,the lever can be pulled which in turn unlocks the rest of the levers for further...

No.6 lever in the centre is the master lever of the ground frame.It has a lock which is unlocked by a key issued by the Station Master.Once the key is inserted and turned,the lever can be pulled which in turn unlocks the rest of the levers for further operation.This prevents the operation of the levers by unauthorised personnel.