What does the ADCL indication light in the PA5 engineer's cab signal?

The ADCL indication light in the PA5 engineer's cab signals that all doors on the train are closed and locked. This indication is crucial for ensuring the safety of passengers and crew, as it confirms that the train is secure before it departs. It serves as an essential safety check, highlighting that the train is ready for operation, specifically in terms of its doors being properly secured.

The other options address different aspects of train operation but do not pertain directly to the ADCL indication light. For instance, while low air pressure is an important operational concern, it would be indicated by a separate warning system. Regarding readiness for departure, while the ADCL does contribute to this status through door security, it does not encompass other readiness checks such as system diagnostics or signaling systems. Lastly, a control panel malfunction would trigger other alerts or indicators, distinct from the door locking indication.