| 摘要 |
PURPOSE:To prevent the generation of spark and surge noise by carrying-out the interruption of the electric current which flows in an electromagnet by a noncontact switch and carrying-out the ON/OFF control of the noncontact switch by a contact point which is opened and closed according to the operation of a vibrating plate. CONSTITUTION:When a horn switch 9 is closed, electric current flows to increase the base voltage of a transistor 8, and when the turned-ON state is generated, a closed circuit is formed between a battery 7, electromagnet 4, transistor 8, switch 9, and the earth, and an exciting current flows in the electromagnet 4. Then, the electromagnet 4 attracts an armature 2 to push down an interrupter 5, and a contact point 6 is opened, and the electric current which flows in the resistors 13 and 14 is cut off, and the base voltage of the transistor 8 becomes zero, and the exciting current which flows in the electromagnet 4 is cut off, and the armature 2 is returned to the original state, and a contact point 5 is closed again, and a repeatedly vibrating plate 1 vibrates, and a resonance plate 3 resonates to generate alarm sound. Therefore, the generation of noise is prevented because of the weakness and the gentle variation of the electric current.
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