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A B C
Diagram 90: Block with three occupancy sensors
Diagram 90 shows a block driven by three occupancy sensors. Each of these sensors is
associated with a contact indicator in the software called A, B and C. All indicators are
assigned to the same block in the software. The block is indicated as occupied as soon
as a train enters section A from the left or section C from the right. The block remains
occupied until the train leaves the opposite section. The indicator A is additionally used
as stop indicator for trains running to the left, C acts as stop indicator for trains running
to the right. The trains are stopped at the boundary between B and A or C, respectively.
The indicator B is used as brake indicator for both directions. Trains begin to slow
down when entering B from either direction. The sections A and C should be long
enough, that each train is safely stopped before touching one of the switches. On the
other side the longest train should completely fit into the block when being stopped. For
this reason the boundaries between B and A or C, respectively, where trains are
stopped, must be located close enough to the boundaries of the complete block.
The configuration displayed in Diagram 90 is the optimal solution from a pure technical
point of view. The block is indicated as occupied as long as a train is located in one of
the three occupancy sections. Additionally it would be even possible to distinguish in
which of the three sections A, B or C a train is located. This method is also relatively
costly, though, because occupancy sensors are usually relatively expensive and the rails
must be cut at the boundaries of each occupancy section.
A B C
Diagram 91: Block with an occupancy and two momentary sensors
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