| 摘要 |
PURPOSE:To prevent the erroneous rumbling without making a rumbling voltage scope narrow by making variable a size of the load at the time of non-rumbling, and fixing a threshold voltage level when the rumbling is started. CONSTITUTION:One end is connected to an electric power source terminal 4a, and a driving circuit 1 to drive the sounder not as shown in the figure and a load 2 at the time of non-rumbling composed of variable resistance are selectively connected. The switching circuit 3, when a threshold is set to a resistance 6 and a supply voltage level exceeds the threshold from a threshold circuit 5 to monitor the supply voltage level, is switched to a driving circuit 1 side. Thus, by fixing a threshold voltage level, adjusting the load at the time of non-rumbling and suppressing an erroneous rumbling preventing level to the low level, the erroneous rumbling can be prevented without making the rumbling voltage scope narrow.
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