In the Light obscuring smoke detector, smoke interferes with a light-weight beam among a light-weight supply and photocell. The photocell steps the level of light-weight it gets. This type of fire detection equipment can be used to protect large areas with The sunshine supply and photocell positioned a ways apart. https://socialinplace.com/story3952559/helping-the-others-realize-the-advantages-of-conventional-fire-system