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You can see the on-board computer
control in Figure 2.85 .
The state machine starts in the state free . It changes to the composite state
usage handover as soon as the signal card data arrives. The internal view of the
state is not shown. It has a special exit point. The exit point cancel is selected
when the usage handover is canceled, e.g., due to an invalid PIN. The on-board
computer control is then in the state free or in use again.
The state usage handover is internally terminated (fi nal state) in the positive
case. This causes the transitions outgoing above and below to activate immediately,
because they may not have triggers. Instead they have conditions that check
the state the right-hand region is currently active in. In our case, that ??™ s the handover
state, and we switch to in use state. During the transition we send the signal
pickup completed . This sets the state return in the right-hand region. This region
serves as a sort of knot in the handkerchief to remember the direction in which
the next usage handover should occur.


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