| 摘要 |
An optical fire detector has a radiation-emitting means which emits a beam of radiation which, after passing through an intermediate air-medium is received by a radiation detecting means for providing an alarm upon an obscuration of the beam or radiation. The radiation-detecting means has first means for individually measuring the intensity in a first and a second wave-length band of the beam of radiation and second means for comparing the invididually measured intensities to provide the alarm upon a predetermined difference between such intensities. |
