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Diagram 138. This configuration works in the same way as Diagram 93. The Virtual
Contact B acts as brake indicator for both directions. A is the reference contact of B for
trains running to the right and C, respectively, the reference contact for the opposite direction.
Even though a Virtual Contact is used the locomotives do not have to match
their speed profile as exactly as in Diagram 137, because B acts as a brake indicator
only and it does not matter, if trains begin to slow down a little bit too early or too late.
202
B C
Diagram 139: Block with two occupancy sensors
In the diagram displayed above it is assumed that the block is only passed from the left
to the right. B acts as brake indicator and C as stop indicator for trains running to the
right. But there is a disadvantage for passing trains. Let us assume that a train is passing
the block from the left to the right and that a route is to be activated before the block
ahead, to the right of this block. As soon as the passing train enters section B the route
is activated. In the same moment the train begins to slow down, because B is also a
brake indicator and the train has to wait, until the route is reported to be activated which
needs a certain time. This can be avoided by adding an additional Virtual Contact according
to the following diagram:
A
B C
Diagram 140: Block with occupancy sensors and Virtual Contact
In Diagram 140 it is also assumed that the block is only passed from the left to the right.
The occupancy indicator B is the reference contact of the Virtual Contact A for trains
running to this direction. A acts as brake indicator and C as stop indicator for this direction.
By adding the Virtual Contact A undesired speed changes of passing trains caused
by activation of routes ahead can be avoided provided the virtual distance between B