| 摘要 |
An alarm device for detecting smoke, fire or the like includes a reference and measurement chamber for comparing the character of the ambient atmosphere with a volume of reference gas, and a radioactive source for ionizing the contents of each of the chambers. Electrodes communicating with each of the chambers measures an electric field within each of the latter indicative of the degree of ionization of the contents thereof. An electronic circuit senses the relative difference of the signals produced by the electrodes associated with each of the chambers and activates an alarm when a signal of predetermined magnitude is sensed indicating the presence of smoke or the like in the area of the detector. The electronic circuit includes: memory circuit means for filtering out spurious electrical signals produced by temporary short circuit conditions in the device; a comparative discriminator circuit for compensating for slow occurring variations in the character of the contents of each of the chambers; and, a time delay circuit for suppressing alarm signals in the event of a temporary short or open circuit condition in the device.
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