| 摘要 |
PURPOSE:To prevent the titled device from malfunctions such as noises by timing for a prescribed period from the time a smoke detecting output exceeds a standard value and, when the smoke detecting output is still larger than the standard value after passing the prescribed period, generating an alarm. CONSTITUTION:When smoke is generated in detection atmosphere and the output of an amplifier 23 exceeds standard voltage V1, a comparator 24 outputs a high level signal. The output is applied to an up/down (U/D) controlling terminal of an U/D counter and up-counting is executed. When the U/D counter counts up two input pulses, a high level signal is outputted from an output terminal SX and a buzzer 6 is continuously driven through an OR circuit 5 to indicate the generation of smoke for a comparatively long period. In case of tobacco smoke, the U/D counter 8 counts up the fall of the 1st pulse outputted from the OR circuit 9, but the smoke disappears before the 2nd decayed pulse is applied after a few seconds, so that the U/D terminal is turned to the low level and no up-counting and buzzing take place. |
