The Fixed Temperature Release (FTR) Pilot Line Detector (PLD) is designed to be used on wet or dry pilot line release systems and trigger the operation of deluge systems, non-interlock preaction systems, single interlock and double interlock systems. The FTR incorporates a 2.5mm glass bulb with a Model F1 Sprinkler frame. It is identified as a Fixed Temperature Release (FTR) to differentiate it from a sprinkler. The FTR is made of die cast brass and is available in various finishes. During fire conditions the heat sensitive liquid in the bulb expands, the bulb shatters, releasing the cap and spring assembly. This triggers the opening of the pilot line, releasing the pressure (air, gas or water), causing the deluge or preaction system valve to open and deliver water under pressure to the system pipes.