What are the danger condition indications?

• A. Only the DANGER indicator illuminates.
• B. The SAFE indicator extinguishes; detector heads illuminate.
• C. A warning indicator illuminates but no danger.
• D. The DANGER indicator illuminates; the control unit and remote WARNING indicators operate; the SAFE indicator extinguishes; the detector head indicators illuminate corresponding to the detector head(s) that sense the danger or warning condition; a red strobe light in the CHT pump room flashes and a bell rings; a bell outside the CHT pump room also rings; because a WARNING is also set off, amber strobe light and buzzer inside the CHT pump room will operate.

Answer: (D)

When danger is detected, the signaling system brings up a full set of warnings to ensure everyone notices and can act. The DANGER indicator on the main unit lights to show a critical condition. The control unit and remote WARNING indicators also activate so people away from the room get alerted. The SAFE indicator goes out, indicating the system is no longer in a safe state. Detector heads illuminate to show exactly which sensors triggered the alert. Audible and visual alerts then reach everyone: a red strobe light in the CHT pump room flashes and a bell rings there, plus a bell rings outside the pump room. Because a WARNING is also triggered, the amber strobe light and buzzer inside the CHT pump room operate as well. This combination—local and remote indicators, illuminated detectors, and coordinated audible/visual alerts—captures the full picture of a danger condition. Other options miss parts of this multi-channel signaling, such as omitting remote indicators, the extinguishing of the SAFE indicator, or the involvement of the bells and amber strobe.