| 摘要 |
PROBLEM TO BE SOLVED: To prolong the life of an alarm by preventing the wear of contacts of an electromagnetic alarm and simultaneously to suppress the generation of noise to the outside of the alarm. SOLUTION: The current to a coil (11) for vibrating a diaphragm (1) by an electromagnetic effect is controlled by using a power MOS type FET (12) and a transistor (TR) 10 for controlling this FET (12) by a weak current is disposed. Only the current flowing in the TR (10) is passed to the contacts (5a) and (5b) and therefore the generation of sparks is suppressed.
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