| 摘要 |
A security system for monitoring the presence in, respectively passage through defined zones such as, e.g. exit areas in shops or stores of objects, for example commodities, which system comprises an antenna (7) with at least one tuning capacitor (1) in the monitored zone and receiver/transmitter devices functioning as tuned resonance circuits on the individual objects monitored, the antenna emitting at short intervals an electrical signal that makes the receiver/transmitter device of a monitored object, which is present in the monitored none, oscillate, which oscillations in the intermissions between antenna (7) transmissions can be received by the antenna (7) - or by a separate antenna - and used to detect the presence of the monitored object in the monitored zone. A switch (3) is provided in the electrical circuit between the antenna (7) and the tuning capacitor (1).
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