Editing Physical security (section)

====Alarm systems and sensors====
{{Main|Security alarm}}
[[Security alarm|Security alarms]] can be installed to alert security personnel when unauthorized access is attempted. Alarm systems work in tandem with physical barriers, mechanical systems, and security guards, serving to trigger a response when these other forms of security have been breached. They consist of sensors including [[Perimeter intrusion detection system|perimeter sensors]], [[motion sensors]], contact sensors, and [[glass break detector]]s.<ref>{{Cite book|title=Field Manual 3-19.30: Physical Security|publisher=Headquarters, United States Department of Army|year=2001|chapter=Chapter 6: Electronic Security Systems|url=http://www.globalsecurity.org/military/library/policy/army/fm/3-19-30/ch6.htm|url-status=live|archive-url=https://web.archive.org/web/20130313231931/http://www.globalsecurity.org/military/library/policy/army/fm/3-19-30/ch6.htm|archive-date=2013-03-13}}</ref>

However, alarms are only useful if there is a prompt response when they are triggered. In the reconnaissance phase prior to an actual attack, some intruders will test the response time of security personnel to a deliberately tripped alarm system. By measuring the length of time it takes for a security team to arrive (if they arrive at all), the attacker can determine if an attack could succeed before authorities arrive to neutralize the threat. Loud audible [[alarm device|alarms]] can also act as a psychological deterrent, by notifying intruders that their presence has been detected.<ref>{{cite book|author=Fennelly, Lawrence J.|title=Effective Physical Security|publisher=Butterworth-Heinemann|year=2012|isbn=9780124158924|pages=345–346|url=https://books.google.com/books?id=hfuODGScv_0C&pg=PA345|url-status=live|archive-url=https://web.archive.org/web/20130921072054/http://books.google.com/books?id=hfuODGScv_0C&pg=PA345|archive-date=2013-09-21}}</ref>

In some U.S. jurisdictions, law enforcement will not respond to alarms from intrusion detection systems unless the activation has been verified by an eyewitness or video.<ref>{{cite web |url=http://isc.temple.edu/economics/wkpapers/Pubs/FalsePolicy.pdf |title=Evaluation of alternative policies to combat false emergency calls |page=238 |url-status=dead |archive-url=https://web.archive.org/web/20121101083705/http://isc.temple.edu/economics/wkpapers/Pubs/FalsePolicy.pdf |archive-date=2012-11-01 }}</ref> Policies like this one have been created to combat the 94&ndash;99 percent rate of false alarm activation in the United States.<ref>{{cite web |url=http://isc.temple.edu/economics/wkpapers/Pubs/FalsePolicy.pdf |title=Evaluation of alternative policies to combat false emergency calls |page=233 |url-status=dead |archive-url=https://web.archive.org/web/20121101083705/http://isc.temple.edu/economics/wkpapers/Pubs/FalsePolicy.pdf |archive-date=2012-11-01 }}</ref>