| 摘要 |
A system for monitoring the position of a receptor reradiator in a surveillance zone having a first means for transmitting a first signal through the zone, and a receptor reradiator operable in response to reception of said signal to radiate at least one reply signal which is a function of the first signal and of the position of said receptor reradiator in the zone. There is also a receiver for receiving the reply signal, means controlled by the receiver, dependent upon the reply signal to indicate the position of the receptor reradiator in the zone, and an alarm triggerable by the receiver responsive to the latter for receiving the reply signals.
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