| 摘要 |
PCT No. PCT/SE84/00381 Sec. 371 Date Jul. 10, 1985 Sec. 102(e) Date Jul. 10, 1985 PCT Filed Nov. 9, 1984 PCT Pub. No. WO85/02285 PCT Pub. Date May 23, 1985.Two strips (ribbons of foil) are positioned underneath a label on an article. Upon purchase of the article a magnetizing means with two spaced apart magnets provided thereon is passed across the strips in the transverse direction of the latter. One of the strips is of a ferromagnetic hard material and then will be magnetized with a number of poles. The second (one of the strips is of a ferromagnetic soft material which possesses the property of generating harmonics in a magnetic field. In combination with a magnetized strip having more than two north and south poles the ferromagnetic soft material will, however, be magnetically saturated so that harmonics will not be generated. In a sensing zone including magnetic fields the ability of the strips to generate harmonics is detected. If such harmonics are generated, the alarm is activated.
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