| 摘要 |
A fire detector to be disposed on a mounting surface such as a ceiling, comprising a chamber open to the ambient atmosphere the chamber having a base, a peripheral region of which lies in a single plane preferably parallel with the surface when the detector is mounted thereon, the base being formed inwardly of the peripheral region with a pair of oppositely sloped recesses meeting at a generally central ridge extending across the base laterally of the recesses, an optical source mounted at the end remote from the ridge of one of the recesses with its optimum optical path directed therealong and an optical receiver mounted at the end remote from the ridge of the other recess with its optimum optical path facing therealong, characterised in that said optimum optical paths are each at a different angle to said plane so that the optical axes of the source and the receiver meet at an angle between 170 DEG and 135 DEG at a position within the chamber spaced laterally from the ridge. |
