Abstract: The invention relates to an air vent system for a door of an automobile to allow a passenger to avoid undesired exposure to air by completely blocking an air duct, the system constructed with a door duct installed at a door with an inlet that is to be tightly aligned to a duct of a crush pad when the door is closed and an outlet formed to a predetermined direction of the door and control apparatus installed in the front side of the door duct to control an air exhausting direction, the system comprising: a damper arranged in the center of the door duct for opening and closing the door duct at the time of rotations; a damper knob coupled with a rotary axis at an edge of the door duct to be rotated; and links connecting damper and damper knob which is rotated to allow the damper to open and close the door duct.

Abstract: A power source voltage tracking circuit, for providing a given voltage which is lower than power source voltage, containing a first node for applying a power source voltage, a second node and an output line, a load connected between the first node and the output line to precharge the output line with the given voltage, elements connected between said first node and said second node to charge the second node, and elements to discharges the output line charged with the given voltage in response to the charging voltage of the second node.