To activate the Door Interlock Bypass button on PA5 cars, what is the first step?

To activate the Door Interlock Bypass button on PA5 cars, the first step involves depressing and holding the Bypass button. This action is essential because the bypass mechanism is designed to temporarily disable the door interlock system, allowing for safe access to the train while ensuring that standard safety protocols are observed.

The interlock system is what prevents doors from being opened while the train is in motion, so engaging the bypass button is a critical procedure for engineers when performing necessary duties, particularly in cases where access to the train is needed without causing safety hazards.

While other options can be part of train operations or safety procedures, they do not initiate the bypass process itself. For instance, turning the MC handle to the off position or powering down the train would not directly relate to bypassing the door interlock and would instead stop the train or affect its power status. Checking that all doors are closed is indeed important for safety and operational integrity, but it is also not the first action in activating the Door Interlock Bypass system. Thus, depressing and holding the Bypass button remains the immediate and necessary step for accessing the interlock bypass function.