Patent attributes
An anti-theft vehicle alarm system includes an acceleration sensor acting as a tilt sensor, a microcomputer, a first power source for supplying a first voltage to the microcomputer, and a second power source for supplying a second voltage to the acceleration sensor. The microcomputer calculates a tilt angle of a vehicle from output of the acceleration sensor and activates an alarm in accordance with the tilt angle. If the second voltage is outside a predetermined voltage range, for example, due to a reduction in battery voltage, the microcomputer temporarily stops to activate the alarm to prevent a false alarm. The microcomputer monitors the second voltage not the battery voltage. Thus, even when the second voltage is outside the threshold range, for example, due to a breakdown in the second power source, the false alarm can be prevented.
