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An active electronic motion detector contains an optical, microwave, or acoustic sensor, as well as a transmitter. However, a passive contains only a sensor and only senses a signature from the moving object via emission or reflection. Changes in the optical, microwave or acoustic field in the device's proximity are interpreted by the ...
Active devices require the user to take some action to trigger an alarm condition; passive systems monitor the user and raise an alarm based on an algorithm - a fall, lack of activity, etc. A weakness of active devices is that the user must be conscious to trigger the alarm. Both passive and active devices require that the user wear the device.
A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors . PIR sensors are commonly used in security alarms and automatic lighting applications.
The electric immobiliser/alarm system was invented by St. George Evans and Edward Birkenbuel and patented in 1919. [2] They developed a 3x3 grid of double-contact switches on a panel mounted inside the car so when the ignition switch was activated, current from the battery (or magneto) went to the spark plugs allowing the engine to start, or immobilizing the vehicle and sounding the horn. [3]
Alerting devices indicate an alarm condition. Most commonly, these are bells, sirens, also and or flashing lights. Alerting devices serve the dual purpose of warning occupants of intrusion and potentially scaring off burglars. Keypads: Keypads are devices that function as the human-machine interface to the system. In addition to buttons ...
In nuclear engineering, active safety contrasts to passive safety in that it relies on operator or computer automated intervention, whereas passive safety systems rely on the laws of nature to make the reactor respond to dangerous events in a favourable manner.