Final answer:
The conductor passes the prescribed buzzer signal to the train operator when a car inspector and police officer are needed on the train.
Step-by-step explanation:
In railroad operations, the conductor plays a crucial role in ensuring safety and coordination during a train's journey. When a train is en route and the services of a car inspector and police officer are necessary, the conductor communicates this need to the train operator using a prescribed buzzer signal. This signal serves as a notification to the train operator that the assistance of a car inspector and police officer is required on the train. The timing for passing this signal is typically when the need for inspection or security measures becomes apparent, contributing to effective communication and the overall safety of railroad operations.