| 摘要 |
PROBLEM TO BE SOLVED: To prevent excessive voltage from being applied to a display device to display the operational state of an emergency notifying system mounted on a vehicle, and to prevent the display device from no display of the operational state in the emergency notifying system. SOLUTION: When the voltage applied to a display unit 600 exceeds the predetermined value, the reverse current runs in a Zener diode 621 in a voltage detection unit 620, and a transistor 622 is turned ON. As a result, a transistor 631 in a switch unit 630 is turned OFF, and the current running in an LED 611 of a state display unit 610 is shut off. Further, when the voltage applied to the display unit 600 is below the predetermined value, no reverse current runs in the Zener diode 621 in the voltage detection unit 620, and the transistor 622 is turned OFF. As a result, the transistor 631 in the switch unit 630 is turned ON, and current runs again in the LED 611 of the state display unit 610. COPYRIGHT: (C)2006,JPO&NCIPI
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