| 摘要 |
<p>A smoke detector is disclosed which includes a smoke chamber having an inlet through which smoke can enter the chamber. In the chamber there are two light sources, preferably LEDs, which radiate light at frequencies which are as widely spaced as possible. Blue and infrared LEDs are preferred as these have wavelengths of about 430 nm and 980 nm respectively. The chamber also has therein one or more photosensitive devices onto which light scattered by smoke particles in the chamber falls. There is a barrier between the light sources and the photosensitive device to prevent light travelling in a straight line from the sources to the photosensitive device. Embodiments are disclosed which have more than two light sources, more than one photosensitive device and more than one smoke chamber.</p> |
