Abstract: A security system that includes an inductive sensor commonly known as a "proximity sensor" or "variable reluctance sensor", an alarm unit, and a controller that allows a user to position the movable structure on which the sensor is mounted, e.g., a door or window, at a selected position and then arm the security system with the structure in that position to detect movement of the structure away from the selected position. For example, the user may open a window on which the sensor is mounted and then arm the alarm to trigger upon detection of movement of the window from that position or, alternatively, only upon detection of further opening of the window or, alternatively, only upon detection of closing of the window. A user could thus open a window a small, selected amount to admit fresh air without triggering the security system or open a door a small, selected amount to receive a caller or allow pets to enter or leave the premises without triggering the security system.