| 摘要 |
PROBLEM TO BE SOLVED: To monitor rapid temperature rise simultaneously with a smoke density by one detecting means. SOLUTION: A disaster prevention alarm device comprises a measurement start means 11 for transmitting sound wave into a measurement duct 8 at every measurement sampling time, an amplifying means 12 for receiving the sound wave which is transmitted from the measurement start means 11, a propagation time measuring means 13 for measuring a sound wave propagation time between the measurement start means 11 and the amplifying means 12, a propagation time determining means 14 for comparing the propagation time with a predetermined measurement time, and an alarm means 16 for issuing alarm by the output of the propagation time determining means 14. Consequently, the shortening of the sound wave propagation time due to the temperature rise is simultaneously detected with the drop of a sound wave reception voltage by the smoke density. COPYRIGHT: (C)2005,JPO&NCIPI
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