| 摘要 |
A system for actuating an alarm device secreted in a packet of bills when the packet is carried outwardly through a transmitted field at an exit from protected premises, in which such actuation is prevented when the packet is carried into the field near the exit and then back again into the protected premises. This is accomplished by constituting the field of two different field regions, an inner field region and an outer field region, having different identifying characteristics which are distinguishable by electronic circuitry in the packet, these field regions being disposed so that a person removing the packet from the protected premises must pass along an egress path extending in sequence through the inner field region and the outer field region. Circuitry in the packet produces signals indicative of when the packet is in one or the other of the two field regions, or in neither, and activates the alarm only when these signals indicate that the packet has been moved through the inner field region, and then through the outer field region to the exterior.
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