7.1 Route Establishment
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In the figure below consider the line between station A and Station B, which is divided in to 4 blocks. The signals at A and B are home signals (controlled signals) and the signals 1, 2 and 3 are automatic blocking signals. In the reverse direction the entire track segment is treated as one block.

Establishment of route

In the idle condition controlled signals show 'danger' and the ABS signals are extinguished.

When a train is to be dispatched from station A to station B, a "black" current is sent from station A to station B.

If the line is free, i.e. all track relays are picked up, the "black" current arrives at station B and blocks there the dispatch of a train from station B to station A. Station B acknowledges by sending a "yellow" current. The first block post (signal 3) signal lights up and show 'caution'. This block post send the current on, but now as "green" current.

The "green" current passes to the remaining block posts and  their signal switch on to 'proceed'. When the current reaches station A, the home signal (starter) shows 'proceed'. There after the black current is cut off. The direction of movement is now locked. 

[ Continued... ]


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[ 7.1 Route Establishment ] 7.2 Train on Line ] 7.3 Release of Route ]

R. Jayanthan
Last updated on 01 January, 2002