| 摘要 |
PROBLEM TO BE SOLVED: To properly stop alarming by a simple circuit when a control circuit of UL standards is used. SOLUTION: The control circuit 20 inputs a photodetection signal of smoke determined by driving cycles of a light emitting circuit 22 in each fire decision cycles and places a buzzer driving circuit 24 in operation when a fire decision is made successively twice to output an alarm. A capacitor C1 is charged quickly with a switch 14 ON and discharged slowly for an alarm stop period with the switch OFF, an inverter 31 generates an inversion output of L level while the capacitor voltage is at H level, and the light emitting circuit 22 and buzzer driving circuit 24 are externally stopped to stop a buzzer from sounding. The inverter 31 leads in a TEST terminal of the control circuit 20 at the same time by the L-level output to make a current flow out, and consequently the control circuit 20 is switched to a calibration mode to make light emission cycles and fire decision cycles short, thereby stopping alarming by a non-fire decision of the control circuit 20 in a short time. COPYRIGHT: (C)2006,JPO&NCIPI
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