| 摘要 |
An optical flame detector having a first photocell focused on a general area and another photocell, connected to electronically oppose the first photocell, more particularly focused on a specific point within the general area. Thus, ambient light-level changes which occur in the entire general area produce voltage generation in both photocells which cancel each other out and, quite properly, do not operate the fire alarm. Yet, the occurrence of flame at the specific point activates the one photocell more than the other and, consequently, does cause operation of the fire alarm.
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