초록 ▼

Intruder-detection systems in which intruder-induced signals are transmitted through a medium also receive spurious signals induced by changes in a climatic condition affecting the medium. To combat this, signals received from the detection medium are converted to a first signal. The system also pro

Intruder-detection systems in which intruder-induced signals are transmitted through a medium also receive spurious signals induced by changes in a climatic condition affecting the medium. To combat this, signals received from the detection medium are converted to a first signal. The system also provides a reference signal proportional to climate-induced changes in the medium. The first signal and the reference signal are combined for generating therefrom an output signal which is insensitive to the climatic changes in the medium. An alarm is energized if the output signal exceeds a preselected value. In one embodiment, an acoustic cable is coupled to a fence to generate a first electrical signal proportional to movements thereof. False alarms resulting from wind-induced movements of the fence (detection medium) are eliminated by providing an anemometer-driven voltage generator to provide a reference voltage proportional to the velocity of wind incident on the fence. An analog divider receives the first electrical signal and the reference signal as its numerator and denominator inputs, respectively, and generates therefrom an output signal which is insensitive to the wind-induced movements in the fence.

대표청구항 ▼

In an intruder-detection system wherein an intruder-induced signal is transmitted through a medium whose signal-conductance changes with variations in a climatic condition to which said medium is exposed, the improvement comprising: first means coupled to said medium for converting signals transmitt

In an intruder-detection system wherein an intruder-induced signal is transmitted through a medium whose signal-conductance changes with variations in a climatic condition to which said medium is exposed, the improvement comprising: first means coupled to said medium for converting signals transmitted therethrough to a first electrical signal, second means for continuously generating an electrical reference signal proportional to the signal-conductance of said medium, third means for receiving the first electrical signal and said reference signal and generating therefrom an electrical output signal unaffected by said signal-conductance changes, and fourth means for giving warning when said output signal exceeds a selected value.