| 摘要 |
Electronic detection device arranged in a passage for the surveillance of marked products, characterized in that it is comprised of a signal emitting device including an emission-reception antenna (1) which produces electromagnetic fields having a predetermined frequency in the protected area; electric marker circuits tuned to resonate to said predetermined frequency, which marker circuits are secured to the articles to be protected; a high sensitivity reception circuit 7h comprising a field effect device 7n piloted by at least one varicap diode 7m which is shunted to said emission-reception antenna (1), which field effect device is intended to detect the electromagnetic effects produced by the resonance of said marker circuits when they pass through the protected area, said emission-reception antenna (1) being arranged vertically on one side of said protected passage.
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