发明名称 |
Surveillance method and system with electromagnetic carrier and plural range limiting signals |
摘要 |
A microwave carrier signal is transmitted throughout a surveillance field. Two low frequency signals are also radiated into the field from opposite sides to limit the field size. A miniature receptor-reradiator containing a nonlinear signal mixing device responds to the signals when in the field to return a modulated carrier signal to a receiver device for actuating an alarm. The alarm is actuated only when the receiver detects a signal having a carrier component corresponding to the microwave signal with sideband components corresponding to the sum of the frequencies of the two low frequency signals.
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申请公布号 |
US4139844(A) |
申请公布日期 |
1979.02.13 |
申请号 |
US19770840240 |
申请日期 |
1977.10.07 |
申请人 |
SENSORMATIC ELECTRONICS CORPORATION |
发明人 |
REEDER, WILLES W. |
分类号 |
G08B25/00;G08B13/16;G08B13/24;G08B23/00;G08B25/04;(IPC1-7):G08B13/18 |
主分类号 |
G08B25/00 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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