Reliability of Stockholm Subway - Index of

Figure 4.10 Net of tracks controlled with an interlock
The reader located on the opposite side of the block receives the signal and sends the
information to the interlock that the block is unoccupied. The moment the train enters
the block its first wheel axis connects both the rails preventing signal translation to
the reader. In that case the reader does not send any signal and the interlock considers
that the block is occupied. There will be no signal until the last train wheel axis will
not have passed the block and the signal from the sender will not be interrupted any
more.
Figure 4.11 Scheme of track circuit
Every block is isolated from others with the filters located on both sides of the block,
which prevent the signal of one track circuit to be translated to the others. The filter is
a wire put in „S‟-shape that connects one rail with another.
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