| 摘要 |
A system for protecting displayed goods against theft comprises sensor switches (100) which interact directly with the goods or with their electrical connecting cables. Said sensor switches (100) are connected via connecting cables (12) to a monitoring circuit. A resistor (130) is connected in series with the sensor switches (100) and, together with them, forms a physical unit. The contacts on the monitoring-circuit-side end of the connecting cable (12D) are bridged by a further resistor (131). The two abovementioned resistors, together with an input resistor (132) of the monitoring circuit, form a voltage divider. The monitoring circuit contains three discriminator circuits (138A to 138C) which are set to different switching thresholds and trigger when one of the sensor switches (100) is opened, a short circuit is caused in the connecting channel (12D), or the connecting cable (12D) is interrupted or unplugged. <IMAGE>
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