- Incandescence
Incandescence is the emission of visible light from a hot body due to its temperature. In simpler terms, it is "light produced by heat." This occurs when an electric current passes through a high-resistance filament (typically tungsten), heating it until it glows.
Historically, incandescence was the primary method for illumination and signaling in fire systems. While being phased out by electroluminescent technologies (LEDs), it is still found in:
- Legacy Fire Indicator Panels (FIPs): Older generation panels (pre-1990s) used incandescent pilot lamps behind colored lenses for alarm and fault signals.
- Fire Pump Controllers: Older fire pump control panels frequently utilized large incandescent indicator lamps to signal critical engine or motor status (e.g., "Pump Running," "Mains Power Available," or "Battery Fault"). These lamps are subject to significant vibration during pump operation, which often leads to filament failure.
- Legacy Exit Signs & Emergency Lights: Older "spitfire" units or box-style exit signs utilise small incandescent globes. These rely on a filament that is susceptible to "burning out" over time.