If a conductor on a train loses indication, what must happen?

When a conductor loses indication, the procedure typically requires priority attention to safety and communication protocols. In this scenario, the correct course of action is to stop the train immediately to ensure the safety of passengers and crew. This step is crucial because losing indication can lead to a loss of control over the train's operation, potentially resulting in dangerous situations or accidents. Stopping allows for a proper assessment of the situation and safeguards against further issues.

Communication with the operator is essential, but it usually occurs after the immediate safety measure of stopping the train has been taken. Continuing to the next station or merely assessing the situation without stopping could compromise safety and violate operational regulations. Therefore, stopping the train first is the immediate and necessary response to any loss of indication.