| 摘要 |
PROBLEM TO BE SOLVED: To provide an improved coil structure having sensitivity sufficient to issue a sound at the gate, in improvement of a tuning circuit used for a commodity case, a self-sounding type article monitoring device firmly fixed to a commodity itself for use, or a non-self-sounding type article monitoring device storable inside a tag case of the same appearance shape as a tag case of the self-sounding type monitoring device, for preventing shoplifting or the like of the commodity. SOLUTION: This article monitoring device has the tuning circuit of 7.2-9.2 MHz comprising a ferrite bar antenna coil provided inside the tag case, and a capacitor connected to the coil. The ferrite comprises, by mass, iron (Fe)≥61.8±10.0%, nickel(Ni)≥13.8±2.0%, copper (Cu)≥9.2±3.0%, zinc (Zn)≥14.6±3.0% and other components. The ferrite bar antenna coil has 7.5μH±10% inductance, a ferrite core has 5-9 mm diameter and a length≤35 mm, and the coil is pitch-wound with a wire of 0.6±0.1 mm diameter. COPYRIGHT: (C)2004,JPO&NCIPI
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