Security system for monitoring the passage of items through defined zones
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United States of America Patent
Stats
-
Dec 31, 2002
Grant Date -
N/A
app pub date -
Dec 9, 1999
filing date -
Dec 9, 1998
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A security system for monitoring the presence of one or more objects in a monitored zone. The system includes an antenna and at least one tag having a tuned resonant circuit, the tag being associated with one or more objects to be monitored. A transmitter, coupled to the antenna, is operable to transmit at one of a plurality of frequencies in response to a frequency selection signal. A receiver, coupled to the antenna producing a tag detection signal for stopping the cycling of the transmitter frequencies in response to a signal received at the receiver from the tag thereby causing the transmitter at a single frequency when a tag is detected. Also provided is a device for decreasing the output power of the transmitter when the receiver signal is above a predetermined level.
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Cited Art Landscape
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