3)What is Approach locking & Back locking with conditions ?

 

3)What is Approach locking & Back locking with conditions ?

Ans) * ROUTE HOLDING IS DONE BY APPROACH AND BACK LOCKING.

Approach locking:

It is an electrical locking which doesn’t allow us to alter the route when train entering into the station.

For providing approach locking, a track circuit for a length of 1.2kms. Need to be provided. Provision of such a long track circuit for the purpose of approach locking is a costly proposition. Therefore, the approach locking is provided without the approach locking becoming effective the moment the signal is cleared irrespective of the position of the train in the approach.Such an approach locking is known as “Dead approach locking”. In other words, once the signal is „OFF it gets approach locked and the route can be released

Back/Route locking:

It is an electrical locking ,whenever train passes the signal and it effective until the train occupies & clear the all tracks in route including last point section.The route of the any particular signal is from the foot of the signal to  ahead of that signal.but the route for back locking is from the foot of the signal to last point track.