| 摘要 |
A security system includes an intrusion detector having a transmitter coupled with a portable receiver to alert a homeowner or the like that an intrusion has taken place or occurred within a pre-set time period. The area under surveillance is monitored by an infrared detector which activates the transmitter upon the receipt of abrupt differences in infrared radiation levels, associated with the presence of a warm body in an otherwise equilibrated environment. A radio signal is emitted by the transmitter upon activation by a transmitter-receiver carried by the homeowner or the like as he/she approaches the protected area. The radio signal from the transmitter is received by the portable remote transmitter-receiver. A first signal, indicating that an intrusion has been detected in the monitored areas, is displayed on the receiver for a preselected period of time. After the preselected period of time has elapsed, a second signal is generated to indicate that the intrusion took place at a time greater than the preselected period of time. The first signal indicates that the intrusion is recent and that the probability of the intruder still being present is great. Once the intrusion detector is activated, the signal is stored until transmission is requested by the portable receiver and then transmitted continuously until the intrusion detector has been reset.
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