Editing Security alarm (section)

==Sensor types==

===Hermetically sealed reed switches===
[[File:Reed Magnetic Switch.png|thumb|150px|left|Reed Switch]]The hermetically sealed [[reed switch]] is a common type of two-piece sensor. This switch operates with an electrically conductive switch that is either normally open or normally closed when under the influence of a magnetic field in respect to proximity to the second piece, which contains a [[magnet]]. When the magnet moves away from the reed switch, the reed switch either closes or opens, based on the normally closed or open design. This action, coupled with an electric current, allows an alarm control panel to detect a fault on that zone or circuit. These sensors are common, are found wired directly to an alarm control panel, or are typically found in wireless door or window contacts as sub-components.

===Passive infrared detectors===
[[Image:Burglar alarm.JPG|thumb|A [[passive infrared sensor]] used to detect motion]]

The [[Passive infrared sensor|passive infrared]] (PIR) motion detector is one of the most common sensors found in household and small business environments.  This sensor does not generate or radiate energy; it works entirely by detecting the heat energy given off by other objects.

PIR sensors identify abrupt changes in temperature at a given point. As an intruder walks in front of the sensor, the temperature at that point will rise from [[room temperature]] to [[thermoregulation|body temperature]] and then back again. This quick change triggers the detection.

PIR sensors designed to be wall- or ceiling-mounted come in various [[Field of view|fields of view]]. PIRs require a power supply in addition to the detection signaling circuit.

=== Infrasound detectors ===

The [[infrasound]] detector works by detecting infrasound, or sound waves at frequencies below 20{{nbsp}}Hz. Sounds at those frequencies are inaudible to the human ear.<ref>{{Cite web|url=https://www.nasa.gov/larc/nasa-langley-researchers-nab-invention-of-the-year-for-infrasound-detection-system/#.VN2ml2TF874|title=NASA Langley Researchers Nab Invention of the Year for Infrasound Detection System|date=2014-07-25|website=www.nasa.gov}}</ref> Due to its inherent properties, infrasound can travel distances of many hundreds of kilometers.{{sfn|Chilo|Lindblad|2008|p=<!-- 18{{ndash}}21 -->}}

The entire infrasound detection system consists of the following components: a speaker (infrasound sensor) as a microphone input, an order-frequency filter, an analog-to-digital (A/D) converter, and an microcomputer to analyze the recorded signal.
[[File:Home Intruder Alarm system.JPG|thumb|Exterior alarm [[bell box]]]]<!-- <ref>{{Cite web|title=A Low Cost Infrasonic Recording System|last=Girisha Durrel De Silva & Kasun De Zoyza|website=http://www.comp.nus.edu.sg}}</ref> -->

If a potential intruder tries to enter into a house, they test whether it is closed and locked, uses tools on openings, or/and applies pressure, creating low-frequency sound vibrations. Before the intruder breaks in, the infrasound detector automatically detects the intruder's actions.

The purpose of such a system is to detect burglars before they enter the house to avoid both theft and vandalism. The sensitivity is dependent on the size of a home and the presence of animals.

===Ultrasonic detectors===
These active detectors transmit ultrasonic sound waves that are inaudible to humans using frequencies between 15&nbsp;kHz and 75&nbsp;kHz. [[Doppler effect|The Doppler shift principle]] is the underlying method of operation which detects a change in frequency due to object motion. This detection occurs when the object must cause a change in the ultrasonic frequency to the receiver relative to the transmitting frequency.

The ultrasonic detector operates by the transmitter emitting an ultrasonic signal into the area to be protected. Solid objects (such as the surrounding floor, walls, and ceiling) reflect sound waves, which the receiver will detect. Because ultrasonic waves are transmitted through air, hard-surfaced objects tend to reflect most of the ultrasonic energy, while soft surfaces tend to absorb the most energy.

When the surfaces are stationary, the frequency of the waves detected by the receiver will be equal to the transmitted frequency.  However, a change in frequency will occur as a result of the Doppler principle when a person or object is moving towards or away from the detector. Such an event initiates an alarm signal. This technology is not active in many properties as many consider this obsolete.

===Microwave detectors===
This device emits microwaves from a transmitter and detects any reflected microwaves or reduction in beam intensity using a receiver. The transmitter and receiver are usually combined inside a single housing (monostatic) for indoor applications and separate housings (bistatic) for the protection of outdoor perimeters high-risk sites and critical infrastructures such as [[fuel]] storage, [[petrochemical]] facilities, [[military]] sites, civil and military [[airport]]s, [[Nuclear power|nuclear]] facilities and more. To reduce false alarms this type of detector is usually combined with a passive infrared detector or similar alarm. Compared to the monostatic, the bistatic units work over longer distances: typical distances for transmitter-receivers up to 200{{nbsp}}m for [[X band|X-band]] frequencies and up to 500{{nbsp}}m for [[K band (IEEE)|K-band]] frequencies.<ref>{{Cite journal |last=The National Institute of Justice |date=1998 |title=Perimeter Security Sensor Technologies Handbook |url=https://www.ojp.gov/pdffiles1/Digitization/206415NCJRS.pdf |journal=Defense Advance Research Project Agency |pages=NIJ: 2.12–2.13}}</ref>
[[File:Microwavebeam.jpg|thumb|266x266px|[[Microwave]] detection system used to protect a solar farm]]
Microwave detectors respond to a [[Doppler effect|Doppler shift]] in the frequency of the reflected energy, by a phase shift, or by a sudden reduction of the level of received energy. Any of these effects may indicate motion of an intruder. Microwave detectors are low cost, easy to install, have an invisible perimeter barrier. and is not affected by fog, rain, snow, sand storms, or wind. May be affected by the presence of water dripping on the ground. Typically need a sterile clearance area to prevent partial blocking of the detection field.

==== Functioning ====
The microwave generator is equipped with an [[Antenna (radio)|antenna]] that allows it to concentrate the beam of electromagnetic waves in one preferred location and the beam is intercepted by the receiver, equipped with a similar antenna to the transmitter.

The graphical representation of the beam is similar to a cigar, and, when not disturbed, it runs between the transmitter and the receiver and generates a continuous signal. When an individual tries to cross this beam, it produces a disturbance that is caught by the receiver as a variation of amplitude of the received signal.

These barriers are immune to harsh weather, such as [[fog]], heavy [[rain]], [[snow]] and [[Dust storm|sandstorms]]: none of these atmospheric phenomena affect in any way the behaviour and the reliability of the microwave detection. Furthermore, the working [[temperature]] range of this technology goes from -35&nbsp;°C to +70&nbsp;°C.<ref>{{Cite journal |date=2012 |title=Guide to Perimeter Intrusion Detection Systems (PIDS) |url=https://www.cpni.gov.uk/resources/perimeter-intrusion-detection-systems-guidance-document |journal=Centre for the Protection of National Infrastructure |number=5/12 |pages=24–38}}</ref>

==== Digital analysis of the signal ====
The more recent and higher performance models of these detectors generate a detection whether the intruder is rolling, crossing, crawling or moving very slow within the [[electromagnetic field]]<ref>{{Cite book |last1=De Astis |first1=Vincenzo |title=Security technology handbook |last2=Gasparini |first2=Bruno |publisher=Assosicurezza |year=2002 |location=Milano |pages=100–102 |language=en}}</ref> reducing false alarms. The [[ellipsoid]]al shape of the longitudinal section however does not allow a good detection capability close to the receiver or transmitter heads, and those areas are commonly referred to as "dead zones". A solution to avoid this problem, when installing 2 or more barriers, is to cross the respective transmitter and receiver heads some meters from the respective heads or to use mono-head sensor to cover the dead zones.<ref>{{Cite journal |date=2012 |title=Guide to Perimeter Intrusion Detection Systems (PIDS) |url=https://www.cpni.gov.uk/resources/perimeter-intrusion-detection-systems-guidance-document |journal=CPNI - Centre for the Protection of National Infrastructure |number=5/12 |pages=24–38}}</ref>

===Compact surveillance radar===
[[Compact surveillance radar]] emits microwaves from a transmitter and detects any reflected microwaves. They are similar to microwave detectors but can detect the precise location and a GPS coordinate of intruders in areas extending over hundreds of acres. It has the capability of measuring the range, angle, velocity, direction, and size of the target.  This target information is typically displayed on a map, user interface or situational awareness software that defines geographical alert zones or geofences with different types of actions initiated depending on time of day and other factors. CSR is commonly used to protect outside the fence line of critical facilities such as [[electrical substation]]s, power plants, dams, and bridges.

===Photoelectric beams===
Photoelectric beam systems detect the presence of an intruder by transmitting invisible infrared light beams across an area, where these beams may be obstructed. To improve the detection surface area, the beams are often employed in stacks of two or more. However, if an intruder is aware of the technology's presence, it can be avoided. The technology can be an effective long-range detection system, if installed in stacks of three or more where the transmitters and receivers are staggered to create a fence-like barrier. To prevent a clandestine attack using a secondary light source being used to hold the detector in a sealed condition whilst an intruder passes through, most systems use and detect a modulated light source. These sensors are low cost, easy to install, and require very little sterile clearance area to operate. However, it may be affected by fog or very high luminosity, and the position of the transmitter can be located with cameras.

===Glass-break detection===
A [[glass break detector|glass-break detector]] may be used for internal perimeter building protection. Glass-break acoustic detectors are mounted in close proximity to the glass panes and listen for sound frequencies associated with glass breaking.

Seismic glass-break detectors, generally referred to as shock sensors, are different in that they are installed on the glass pane. When glass breaks it produces specific shock frequencies which travel through the glass and often through the window frame and the surrounding walls and ceiling. Typically, the most intense frequencies generated are between 3 and 5&nbsp;kHz, depending on the type of glass and the presence of a plastic interlayer. Seismic glass-break detectors feel these shock frequencies and in turn generate an alarm condition.

Window foil is a less advanced detection method that involves gluing a thin strip of conducting foil on the inside of the glass and putting low-power electric current through it. Breaking the glass will tear the foil and break the circuit.

===Smoke, heat, and carbon monoxide detectors===
Most systems can also be equipped with smoke, heat, and/or [[carbon monoxide]] detectors. These are also known as 24-hour zones (which are on at all times). Smoke and heat detectors protect from the risk of fire using different detection methods. Carbon monoxide detectors help protect from the risk of carbon monoxide poisoning. Although an intruder alarm panel may also have these detectors connected, it may not meet all the local [[fire safety#Fire code|fire code]] requirements of a fire alarm system.

Traditional smoke detectors are ionization smoke detectors which create an electric current between two metal plates, which sound an alarm when disrupted by smoke entering the chamber. Ionization smoke alarms can quickly detect the small amounts of particles produced by fast-flaming fires, such as cooking fires or those fueled by paper or flammable liquids. A newer type of the smoke detector is the photoelectric smoke detector. It contains a light source, which is positioned indirectly to the light sensitive electric sensor. Normally, light from the light source shoots straight across and misses the sensor. When smoke enters the chamber, it scatters the light, which then hits the sensor and triggers the alarm. Photoelectric smoke detectors typically respond faster to a fire in its early, smoldering stage, before the source of the fire bursts into flames.

===Motion sensors===
Motion sensors are devices that use various forms of technology to detect movement. The technology typically found in motion sensors to trigger an alarm includes infrared, ultrasonic, vibration and contact. Dual technology sensors combine two or more forms of detection in order to reduce false alarms as each method has its advantages and disadvantages. Traditionally motion sensors are an integral part of a home security system. These devices are typically installed to cover a large area as they commonly cover up to {{convert|40|ft|abbr=on}}, with a 135° field of vision.

A type of motion sensor was used by the Japanese since ancient times.  In the past, "(m)any people in Japan kept singing crickets and used them like watch dogs."<ref>Mathiews, Franklin K. "The Boy Scouts Book of Outdoor Hobbies," D, Appleton-Century Company, Incorporated, New York 1938, page 193.</ref>  Although a dog would bark when it senses an intruder, a cricket stops singing when approached by an intruder. The crickets are kept in decorative cages resembling bird cages, and these cages are placed in contact with the floor.  During the day, the house is busy with normal daytime tasks.  When activity reduces at night, the crickets start singing.  If someone comes into the house at night, the floor starts to vibrate.  "The vibration frightens the crickets and they stop singing.  Then everyone wakes up --- from the silence.<ref>Mathiews, Franklin K. "The Boy Scouts Book of Outdoor Hobbies," D, Appleton-Century Company, Incorporated, New York 1938, page 194.</ref>  The family is used to hearing crickets at night and knows something is wrong if the crickets aren't singing.  A similar observation was made in England about millers who lived in their mills.  A mill wheel makes a great deal of noise, but the miller only awakens when the mill wheel stops turning.

===Driveway alarms===
[[Driveway alarm]] systems can be combined with most security and automation systems. They are designed to alert residents to unexpected visitors, intruders, or deliveries arriving at the property. Types of driveway sensors include magnetic and infrared motion sensors. Driveway alarms can be found in both hard-wired and wireless systems. They are common in rural security systems as well as for commercial applications.

===Electro-mechanical (shaker) sensors===
These [[Electromechanics|electro-mechanical]] devices are mounted on barriers and are used primarily to detect an attack on the structure itself. The technology relies on an unstable mechanical configuration that forms part of the electrical circuit. When movement or vibration occurs, the unstable portion of the circuit moves and breaks the current flow, which produces an alarm.  The medium transmitting the vibration must be correctly selected for the specific sensor as they are best suited to different types of structures and configurations. These systems are low cost and easily installed on existing fences, but can only be fence mounted and are unable to analyze differences in the pattern of vibrations (for example, the difference between gusts of wind and a person climbing the fence). For this reason, this technology is gradually being replaced by digital [[accelerometer]]-based systems.

=== MEMS Accelerometer ===
MEMS technology is an electromagnetic device that is created using [[photolithography]], incision and ionian implantation. This produces a very compact and small device. In this device, in addition to the mechanical system, there are electronic circuits for control, acquisition and conditioning of the signal able to sense the environment.<ref>{{Cite book |last1=De Astis |first1=Vincenzo |title="Manuale delle tecnologie di sicurezza" |last2=Dischi |first2=Franco |publisher=Assosicurezza |year=2019 |location=Italy |pages=133–134 |language=it}}</ref>

MEMS accelerometer can be divided into two groups, piezoresistive and capacitive-based accelerometers. The former consists of a single-degree-of-freedom system of a mass suspended by a spring. They also have a beam with a proof mass at the beam’s tip and a Piezoresistive patch on the beam web.<ref>{{Cite journal |last=Albarbar |first=Alhussein |date=2008 |title=Suitability of MEMS Accelerometers for Condition Monitoring: An experimental study |url=https://www.mdpi.com/1424-8220/8/2/784/pdf |journal= Sensors|volume=8 |issue=2 |pages=784–799|doi=10.3390/s8020784 |pmid=27879734 |pmc=3672998 |bibcode=2008Senso...8..784A |doi-access=free }}</ref>

On the contrary, capacitive-based accelerometers, also known as vibration sensors, rely on a change in electrical capacitance in response to acceleration.<ref>{{Cite book |last1=Venkatanarayanan |first1=A. |last2=Spain |first2=E. |title=Comprehensive Materials Processing |chapter=Review of Recent Developments in Sensing Materials |date=2014 |chapter-url=https://www.sciencedirect.com/science/article/pii/B9780080965321013030 |pages=47–101 |doi=10.1016/B978-0-08-096532-1.01303-0 |isbn=9780080965338 }}</ref>

==== Operating principle ====
The current technology allows to realize suspended silicon structures that are attached to the substrate in some points called anchors, and that constitute the sensitive mass of the accelerometer MEMS. These structures are free to move in the direction of the acceleration detected. They constitute the mobile reinforcement of a pair of capacitors connected to the ''half bridge''.

In this way, the acquired signals are amplified, filtered and converted in digital signals with the supervision of specific control circuits. MEMS' incorporations evolved from a single, stand-alone device to the integrated inertial motion units that are available today.<ref>{{Cite book |last1=De Astis |first1=Vincenzo |title=Manuale delle tecnologie di sicurezza |last2=Dischi |first2=Franco |publisher=Assosicurezza |year=2019 |edition=2nd |location=Italy |pages=134–135 |language=it}}</ref>

This technology uses a variety of transduction mechanisms to detect the displacement. They include capacitive, piezoresistive, thermal, optical, piezoelectric and tunneling.<ref>{{Cite book |last1=Rasras |first1=Mahmoud |title=MEMS Accelerometers |last2=Elfadel |first2=Ibrahim M. |last3=Duong Ngo |first3=Ha |publisher=MDPI |year=2019 |isbn=978-3-03897-415-4 |location=Abu Dhabi, UAE |pages=1–2, 12, 4–6 |language=en}}</ref>

==== Applications ====
[[File:Sioux MEMS 3D Pro2.jpg|thumb|Fence protected by a device which uses MEMS technology to detect intruders]]
In the last decades, many technological progresses have been made in this area and MEMS accelerometers are used in high-reliability environments and are starting to replace other established technologies.

MEMS accelerometer can be applied as a sensor in the earthquake disaster prevention, since one of the main characteristics of MEMS accelerometers is the linear frequency response to DC to about 500&nbsp;Hz, and this capability offers an improvement in measuring [[ground motion]] at lower-frequency band.<ref>{{Cite journal |last1=Aizawa |first1=Takao |last2=Matsuoka |first2=Toshi |last3=Kimura |first3=Toshinori |last4=Takeda |first4=Tetsuya |date=2008 |title=Application of MEMS accelerometer to geophysics |url=https://www.researchgate.net/publication/43195901 |journal=International Journal of the JRCM |volume=4}}</ref>

Another practical application of MEMS accelerometers is in machine condition monitoring to reduce machines’ maintenance. Wireless and embedded technologies such as Micro-electro Mechanical system sensors offer a wireless smart vibration measurement of machine’s condition.<ref>{{Cite journal |last1=Albarbar |first1=Alhussein |last2=Mekid |first2=Samir |last3=Starr |first3=Andrew |last4=Pietruszkiewicz |first4=Robert |date=2008 |title=Suitability of MEMS Accelerometers for Condition Monitoring: An experimental study |url=https://www.mdpi.com/1424-8220/8/2/784/pdf |journal= Sensors|volume=8 |issue=2 |pages=784–799 |doi=10.3390/s8020784 |pmid=27879734 |pmc=3672998 |bibcode=2008Senso...8..784A |doi-access=free }}</ref>

Moving to the [[arms industry|defence]] field, it can be applied in fence-mounted intrusion [[detection]] systems. Since MEMS sensors are able to work in a wide temperature range, they can prevent intrusions in outdoors and very spread-off perimeters.

==== Properties ====
An advantage offered by MEMS Accelerometers is the ability to measure static accelerations, such as acceleration due to gravity. This enables them to constantly verify that the positioning of the sensor, based on MEMS accelerometer, remains unaltered from the installation one.

MEMS accelerometers’ significant advantages also stem from their small size and high measurement frequency; additionally, they can be integrated with multiple sensors with different functions.<ref>{{Cite journal |last1=Niu |first1=Weimeng |last2=Fang |first2=Liqing |last3=Xu |first3=Lei |last4=Li |first4=Xu |last5=Huo |first5=Ruikun |last6=Guo |first6=Deqing |last7=Qi |first7=Ziyuan |date=2018 |title=Summary of Research Status and Application of MEMS Accelerometers |url= |journal=Army Engineering University Shijiazhuang Campus, Shijiazhuang.}}</ref>

===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>

===Electrostatic field===
Sometimes referred to as E-field,  this volumetric sensor uses [[Electroreception and electrogenesis|Electric field proximity sensing]] and can be installed on buildings, perimeters, fences, and walls. It also has the ability to be installed free-standing on dedicated poles. The system uses an electromagnetic field generator powering one wire, with another sensing wire running parallel to it. The sensing wire is connected to a signal processor that analyses amplitude change (mass of intruder), rate change (movement of intruder), and preset disturbance time (time the intruder is in the pattern). These items define the characteristics of an intruder and when all three are detected simultaneously, an alarm signal is generated.

The barrier can provide vertical protection from the ground to the height of the mounting posts (typically 4–6{{nbsp}}meters of height), depending on the number of sensor wires installed.  It is usually configured in zones of about 200 metre lengths. Electrostatic field sensors are high-security and difficult to defeat, and have high vertical detection field. However, these sensors are expensive and have short zones, which contributes to more electronics (and thus a higher cost).

===Microphonic systems===
[[File:Strain -sensor cable installation.jpg|thumb|Strain-sensor cable installed on a chain-link/barbed-wire fence]]
Microphonic systems vary in design (for example, [[Time-domain reflectometer|time-domain reflectrometer]] or [[Piezoelectric sensor|piezo-electric]]) but each is generally based on the detection of an intruder attempting to cut or climb over a fence. Usually the microphonic detection systems are installed as sensor cables attached to rigid chain-wire fences, however, some specialized versions of these systems can also be installed buried underground. Depending on the type, it can be sensitive to different frequencies or levels of noise or vibration. The system is based on coaxial or electro-magnetic sensor cable with the controller having the ability to differentiate between signals from the cable or chain-wire being cut, an intruder climbing the fence, or bad weather conditions.

The systems are designed to detect and analyze incoming electronic signals received from the sensor cable, and then to generate alarms from signals which exceed pre-set conditions. The systems have adjustable electronics to permit installers to change the sensitivity of the alarm detectors to the suit specific environmental conditions. The tuning of the system is usually done during commissioning of the detection devices.

Microphonic systems are relatively inexpensive compared to other systems and easy to install, but older systems may have a high rate of false alarms caused by wind and other distances. Some newer systems use [[digital signal processing|DSP]] to process the signal and reduce false alarms.

===Taut wire fence systems===
A taut wire perimeter security system is an independent screen of tensioned tripwires usually mounted on a fence or wall. Alternatively, the screen can be made thicker to avoid the need for a supporting chain-wire fence. These systems are designed to detect any physical attempt to penetrate the barrier. Taut wire systems can operate with a variety of switches or detectors that sense movement at each end of the tense wires. These switches or detectors can be a simple mechanical contact, static force transducer or an electronic strain gauge. Unwanted alarms caused by birds and other animals can be avoided by adjusting the sensors to ignore objects that exert small amounts of pressure on the wires. This type of system is vulnerable to intruders digging under the fence. A concrete footing directly below the fence is installed to prevent this type of attack.

Taut wire fence systems have low false alarm rates, reliable sensors, and high detection rates, but is expensive and complicated to install.

===Fiber optic cable===
A fiber-optic cable can be used to detect intruders by measuring the difference in the amount of light sent through the fiber core. A variety of fiber optic sensing technologies may be used, including [[Rayleigh scattering]] or [[interferometry]]. If the cable is disturbed, the light will change and the intrusion is detected. The cable can be attached directly to a chain-wire fence or bonded into a barbed steel tape that is used to protect the tops of walls and fences. This type of barbed tape provides a good physical deterrent as well as giving an immediate alarm if the tape is cut or severely distorted.

Being cable-based, fiber optic cables are very similar to the microphonic system and easy to install and can cover large perimeters. However, despite performing in a similar manner to microphonic-based systems, fiber optic cables have higher cost and is more complex due to the use of fiber-optic technology.

===Ported coaxial cable===
[[File:Ported coaxial cable installation.png|thumb|right]]
This system employs an electro-magnetic field disturbance principle based on two unshielded coaxial cables.{{sfn|Chen|Young|1984|p=<!-- 1313{{ndash}}1317-->}} The transmitter emits continuous radio frequency (RF) energy along one cable and the energy is received by the other cable. When the change in field strength weakens due to the presence of an object and reaches a pre-set lower threshold, an alarm condition is generated. The system is covert after installation. The surrounding soil must offer good drainage in order to avoid nuisance alarms. Ported coaxial cables are concealed as a buried form but can be affected by RF noise and is difficult to install.

===Security electric fence===
[[File:Security Electric Fence.JPG|thumb|upright|Multi-zone security electric fence used on top of a physical barrier]]
Security electric fences consist of wires that carry pulses of electric current to provide a non-lethal shock to deter potential intruders. Tampering with the fence also results in an alarm that is logged by the security electric fence energiser, and can also trigger a siren, strobe, and/or notifications to a control room or directly to the owner via email or phone. In practical terms, security electric fences are a type of [[sensor array]] that acts as a (or part of a) physical barrier, a psychological deterrent to potential intruders, and as part of a security alarm system.

Electric fences are less expensive than many other methods, less likely to give false alarms than many other alternative perimeter security methods, and have highest psychological deterrent of all methods, but there is a potential for unintended shock.