The Balanced Magnetic switch is installed on any rigid, operable opening through which access may be gained to the protected room, building or enclosure. The operable opening, such as a door or window, by its construction, constitutes a physical barrier to unauthorized entry. The BMS detects the change in position of the operable opening when such movement or change exceeds 12.7mm in any direction (See 3.1). The BMS consists of two components: the first containing the actuating magnet(s) is installed on or in the moveable member of the operable opening, the second containing the switch function and the biasing magnet(s) (if any) is installed on or in a fixed member of the operable opening, such as the lintel or door jamb adjacent to the first actuating component.