What indicates a customer call from the lavatory?

The correct choice regarding a customer call from the lavatory is the high-low chime accompanied by an amber light and call button activation. This alert system is specifically designed to differentiate calls from other signals. When a customer requires assistance from the lavatory, activating the call button produces a distinct high-low chime, which is easily recognizable by flight attendants. The amber light serves as a visual cue, indicating the precise location of the call, enabling crew members to respond quickly and efficiently.

This system ensures that cabin crew can attend to passenger needs promptly, maintaining service quality and passenger comfort. The other options do not match the specific indicators used for lavatory calls; for instance, the blue light and single chime signal different situations, while the red flashing light typically indicates a more urgent matter. Normal cabin light adjustments do not indicate customer calls at all. Thus, understanding these distinctions helps reinforce proper responses to in-flight situations.