When must employees have their radio tuned to the proper channel?

The correct answer focuses on the requirement for employees to have their radio tuned to the proper channel specifically when they are engaged in radio communication duties. This is crucial for maintaining clear and efficient communication within the operating environment. By listening on the correct channel, employees ensure they receive important operational instructions, updates, and safety information pertinent to their tasks.

This practice underscores the importance of active communication in the workplace, particularly in rail operations where instructions can significantly impact safety and efficiency. Ensuring that radios are tuned correctly during these duties minimizes the risk of miscommunication, which can lead to potentially hazardous situations.

Other choices mentioned do not align with the consistent need for clear communication during work. For instance, being tuned only during scheduled work breaks, once a day, or during emergencies does not account for the unpredictable nature of communication in rail operations, where immediate and ongoing contact is essential for safe and efficient operations.