On a B777 aircraft, which visual indicator illuminates when the lavatory smoke detector is activated?

• A. Customer call reset button outside lavatory door illuminates
• B. Amber light on master call panel illuminates
• C. Forward Attendant Panel indicates "Smoke detected"
• D. Cabin chime over PA system sounds

Answer: (A)

When the lavatory smoke detector is activated, the system provides a direct, local visual cue at the lavatory exterior to quicken crew response. On a B777, the indicator that lights up is the exterior lavatory door's customer call/reset button—the light illuminates to signal that the lavatory has detected smoke and needs attention. This makes it immediately clear which lavatory is affected, without having to hunt through panels or rely on audible cues. The amber light on the master call panel is more general and not tied to a specific lavatory location, the forward Attendant Panel may display a message but isn’t the primary location-specific visual cue, and the cabin chime is an audible alert, which doesn’t provide a visual indication.