Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1991-05-08
1993-05-11
Mullen, Jr., Thomas J.
Communications: electrical
Condition responsive indicating system
Specific condition
340572, G08B 1324
Patent
active
052105245
ABSTRACT:
The invention is related to a process of deactivating a magnetic security marker of an article surveillance system, wherein the security marker is detected by simulating conditions normally present in such a system, e.g., by creating between a transmitter and a receiver a sinewave electromagnetic field and the deactivating the security marker by means of the electronically switchable magnetizing apparatus in response to the detection of the magnetic field which corresponds to the magnetization of the security marker in the surveillance zone. It is the object of the invention to enable the magnetic security marker to be deactivated using any alternating power line. To this end, the magnetic system is automatically connected to a power line without circuit change when the security marker is detected. The magnetizing apparatus gradually builds up a magnetic field by rectifying the flow current, monitoring it by a current sensor and increasing it at each change of phase until the current reaches a level to which the sensor is set as effecting deactivation. Thereafter, the magnetizing apparatus is electronically disconnected from the power line.
REFERENCES:
patent: 3820104 (1974-06-01), Fearon
patent: 4484184 (1984-11-01), Gregor et al.
patent: 4906974 (1990-03-01), Rehder
patent: 5027106 (1991-06-01), Lizzi et al.
Graessle Josef
Schwarz Werner
Barte William B.
Griswold Gary L.
Kirn Walter N.
Minnesota Mining and Manufacturing Company
Mullen Jr. Thomas J.
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