What is tested alongside the PA button during the preflight inspection?

During the preflight inspection, testing the volume over the passenger service unit (PSU) speakers is crucial to ensure that the public address (PA) system has the appropriate sound levels for effective communication with passengers. This functionality is important for safety announcements and other critical communications that take place during the flight.

The PA button is activated, and its purpose is verified by checking that the sound is transmitted clearly and at the correct volume through the PSU speakers. If the volume is too low or non-functional, it may prevent the crew from delivering important messages in an emergency or during routine operations, potentially compromising passenger safety.

This step in the inspection ensures that all safety measures regarding communication are in place before the aircraft is deemed ready for departure.