NORAC Dispatcher Practice Exam

The correct answer is when the missing transponder symbol is displayed. In this context, a missing transponder symbol indicates that the system has detected an issue related to transponder communication, but it does not necessarily imply that the entire system has failed or that it requires immediate action to cut out the system. Instead, it suggests a localized issue that the dispatcher can assess further while the system may still be able to function correctly in other respects.

In practical operations, having a missing transponder symbol may indicate that there is a problem with a specific transponder, yet the overall system could still maintain functionality under certain conditions, allowing trains to operate normally without cutting out the entire system. This means that while monitoring the situation continues, decisions can be made based on the overall performance of the system, instead of immediately taking steps that could disrupt operations unnecessarily.

In contrast, the other options imply conditions where either the system is functioning normally or showing appropriate symbols. In these cases, if there were a fault, it would typically require further action to resolve the issue, highlighting the distinction between a minor fault (as indicated by a missing transponder symbol) and a more critical failure that demands immediate rectification.