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NCJRS Abstract

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NCJ Number: 83327 Find in a Library
Title: Getting Active About Passive Infrared
Journal: Security Management  Volume:26  Issue:6  Dated:(June 1982)  Pages:10-14,16,18
Author(s): J J Strauchs
Date Published: 1982
Page Count: 7
Format: Article
Language: English
Country: United States of America
Annotation: The principles and practical features of passive infrared (PIR) systems for detection of intruders are described.
Abstract: Except for audio intrusion detection systems, PIR is the only major passive detection system available on the market today. In PIR, the intruder is the transmitter and the PIR unit is the receiver. PIR senses motion by dividing the field of view into zones. The PIR detector senses the changes that occur in the field of view when either a cooler or warmer object is introduced. Originally developed in the late 1940's, PIR first became commercially available in the late 1960's. The method is based on the electromagnetic wave theory developed in the 19th century by James Clerk Maxwell. PIR sensors measure infrared radiation by means of thermistors, by the measurement of tiny amounts of current, or by the use of pyroelectric detectors. Most PIR units cost between $125 and $175. PIR systems are immune to most common sources of false alarms. They are not bothered by radio interference, motors, faulty fluorescent lights, and sound. In addition, they are generally immune to vibration, and air turbulence does not bother the most modern units. PIR detectors should generally be used primarily indoors. PIR systems are easy to install and maintain. They are difficult to defeat, except by an extremely knowledgeable intruder. Many PIR detectors are designed to operate from about 20 degrees below zero to 160 degrees above zero Fahrenheit. Diagrams are included.
Index Term(s): Facility security; Intrusion detectors
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