Editing Security alarm (section)

===Ferrous metal detectors===
Change in the local magnetic field due to the presence of [[ferrous]] metals induces a current in the buried sensors (buried cables or discrete sensors) which are analyzed by the system. If the change exceeds a predetermined threshold, an alarm is generated.<ref name="NucReg">{{cite web |title=Perimeter Intrusion Alarm Systems |url=https://www.nrc.gov/docs/ML0037/ML003739217.pdf |publisher=U.S. Nuclear Regulatory Commission |access-date=14 December 2020 |date=1997}}</ref> This type of sensor can be used to detect intruders carrying substantial amounts of metal, such as a firearm, making it ideally suited for [[anti-poaching]] applications.<ref>{{Cite web|last=Trivedi |first =Bijal |title=Hunting Poachers Remotely|url=https://www.technologyreview.com/2007/05/14/272220/hunting-poachers-remotely/|date=14 May 2007 |access-date=26 October 2020|website=MIT Technology Review|language=en}} {{subscription required}}</ref>