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PROCESS OF MAINTAINING SURVEILLANCE WITHIN A CONFINED SPACE AND SURVEILLANCE SYSTEM
PROCESS OF MAINTAINING SURVEILLANCE WITHIN A CONFINED SPACE AND SURVEILLANCE SYSTEM
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机译:在有限的空间和监视系统中保持监视的过程
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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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