| 摘要 |
The anti-theft system comprises a numeric keyboard mounted on the vehicle dashboard and an electronic circuit which is fitted inside the vehicle in an inaccessible location. The system protects the vehicle by interrupting the vehicle's electric system by cutting the ignition circuit and the starter circuit. - The system is automatically activated when the ignition is turned off, and requires that four correct digits are pressed from nine available digits. Pressing an incorrect digit automatically resets the system and initiates an alarm sequence. The electronic circuit uses four, series connected, four-terminal silicon switches which are turned on when the correct keys are pressed, and immediately reset if an incorrect key is pressed. These switches drive a relay which is energised when all four switches are conducting. A timer circuit (555) acts as a multivibrator to drive an alarm.(0/3)
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