This system can be implemented without centralized
monitoring. Basically a part of track between two nodes is tested by sending a
signal from one node to other and receiving it back and testing whether signal
is tampered or not. It avoids accidents, in case miscreants damaged the tracks or it got damaged for
some other reason.
So we will start with a train track that has S – Station and
A,B,C,D and so on are consecutive nodes.
There are four types of signal in this
system.
1.Test Signal(TS) – which tests the portion of the track in
which the signal is sent, whether track is tampered or not. It does it by sending a signal from A to B, then from
B to A. If A got original signal, test is successful.
2.Arrival Signal(AS) – which informs to node left to it( in
case of signal arising from Station) or node which is at second position left to the originating node, that the train has already arrived at the originating node and has started its journey past the node. This signal
triggers further action by receiving nodes. If a train crosses a node, which
exhibits Pass Signal(PS), it is compulsory to send
a arrival signal to the node which is at second position left to it.
3.Distress Signal(DS) – which finds that Test Signal(TS) sent by a node has not been received properly back by it. This says that, that particular part of track is tampered. This Distress Signal(DS) is always sent by a node to the node right of it, so that, train is stopped before hand and enough time is provided to the train to put a brake.
4. Clearance Signal(CS) – which informs the node that sent the Test Signal(TS) has been received properly back. This says track is not tampered.
5. Stop Signal(SS) – which tells the train cannot move forward,
in case train is in station. If the train is moving, it has to stop before the next
node arrives. Stop Signal(SS) can be generated only if a node receives Distress Signal(DS) from the node left to it.(
Exception Station node)
6. Pass Signal(PS) – which tells the train can move ahead to
next station. Pass signal can be generated by a node only if it receives Clearance Signal(CS) from node left to it.
Figure -1
In the beginning, The Train Track Ant-Tamper System at node
S, which is at the station sends a Test Signal(TS) from S to Node A and receives it
back. The signal is randomly generated and changes every time. If the signal
received back is same as the one sent, S gives a Pass Signal(PS) to the train. If the signal
received back by S is not same, S will give a Stop Signal(SS). In a Stop Signal(SS),
train can’t move ahead, if it is in station or should stop before reaching the next node( left to it), if it is a moving train. In case, S gives a Stop Signal(SS),
explanation is in Fig 2. In case S gives a Pass Signal(PS), explanation is in Fig 3
Figure – 2
Here, S gives a Stop Signal(SS). So Train does not move.
Figure – 3
Here, S gives a Pass Signal(PS). So S first sends an Arrival Signal(AS) to A. Arrival Signal(AS) is a signal, which says train has arrived on that
node, which sends the signal( in this case S) and has started moving. Usually Arrival Signal(AS) is transmitted to the second node left to it. But since the train is in station S, exception is given( node A receives Arrival Signal(AS)). Next to
Fig 4.
Figure – 4
Here Since A receives Arrival Signal(AS), it sends a Test Signal(TS) from A to B, to check whether track is tampered or not. Whenever a node
receives a Arrival Signal(AS), it sends a Test Signal(TS) to the node one step left to it. If
A does not receive the same Test Signal(TS), next flow is explained in Fig 5. If A
receives the same Test Signal(TS), next flow is explained in Fig 6.
Figure – 5
Here , A sends a Distress Signal(DS) to S, since same Test Signal(TS) is not received back by A from B, which means Track A to B is tampered.
Whenever a mismatch occurs, the node should send a Distress Signal(DS) to the node right of it( in this case S), to warn the train before hand about an impending danger. Since S
receives a Distress Signal(DS) it puts on Stop Signal(SS) in that node.
Figure – 6
Here , A sends a Clearance Signal(CS) to S, since the same Test Signal(TS) is received back by A from B, which means track A to B is not tampered. Since S
receives a Clearance Signal(CS), it puts Pass Signal(PS) in that node. Next to Fig 7.
Figure -7
Arrival Signal(AS) is always sent to the node which is at
second position left from it. Only in case of train standing in station, Arrival Signal(AS) is first sent to the next left node, than again to the node at second
position left from it. All signals are encoded by some method. When a Node sends an Arrival Signal(AS)( in this case S), it will send some form or other a number 2( for
simplification), which will be received by the next left node( in this case A). On seeing an Arrival Signal(AS), the node ( in this case A) reduces the number by 1 and sends it to the next left node( in this case B). The
receiving node(in this case B) checks the number, if it is 1, starts the further process. After sending Arrival Signal(AS), the train starts to move. Next to fig
8.
Figure 8
Here , B receives Arrival Signal(AS). So it sends a Test Signal(TS) to the next node C. If B does not receive the same signal from C, B sends a Distress Signal(DS) to the previous node A( Fig 9). If B receives the same signal
from C, B sends a Clearance Signal(CS) to A.(Fig 10)
Figure 9
Here, A receives Distress Signal(DS), So A puts up a Stop Signal(SS) and the train reaching node A finds that A has a Stop Signal(SS), so it has to stop
before next node B.
Figure 10
Here, A receives Clearance Signal(CS). So A puts up a Pass
Signal(PS). The train on reaching A sees a Pass Signal(PS) and so crosses it. Whenever
a train passes a Pass Signal(PS) node, it sends a Arrival Signal(AS), which is received
by the second position node left from it. Next to Fig 11
Fig 11
Here , Train sends Arrival Signal to C
The process is repeated forever.
Happy Journey.
