| 摘要 |
The apparatus comprises a circuit controlled by a microcontroller (16 Fig. 1, not shown). The circuit comprises a voltage drop detector circuit 18 for detecting a voltage drop in the battery of the vehicle. The circuit 18 comprises an AC amplifier 40 coupled to the positive terminal of the battery through a coupling capacitor C10 and a resistor R9 and a terminal 3. The output from the amplifier is fed into one input 43 of a voltage comparator 44. A reference voltage derived across a potential divider R16 and 17 is delivered to the other terminal 45 of the comparator. On the voltage on the pin 43 increasing above the reference voltage, the output pin 46 of the comparator goes from a logic low to a logic high, thereby indicating a voltage drop across the vehicle battery. This puts a high on pin (19) of the microcontroller (16) which activates an alarm means. Also disclosed are means for arming and disarming the apparatus, eg by radio, and other means, eg ultrasonic transmitter and receiver, for detecting intrusion into the vehicle. <IMAGE> |
