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Burglar alarm

Burglar (or intrusion), fire, and safety alarms are electronic alarms designed to alert the user to a specific danger. Sensors are connected to a control unit via low-voltage wiring or a narrowband RF signal which is used to interact with a response device. The most common security sensors are used to indicate the opening of a door or window or detect motion via passive infrared (PIR). New construction systems are predominately hardwired for economy. Retrofit installations often use wireless systems for a faster, more economical installation. Some systems serve a single purpose of burglar or fire protection. Combination systems provide both fire and intrusion protection. Systems range from small, self-contained noisemakers, to complicated, multi-zoned systems with color-coded computer monitor outputs. Many of these concepts also apply to portable alarms for protecting cars, trucks or other vehicles and their contents (i.e., "car alarms"). See also fire alarm control panel for specific fire system issues. Burglar alarms are sometimes referred to as alarm systems, see burglar alarm control panel for a discussion of hard-wired burglar alarm system design.

Burglar alarms (or perimeter security systems, perimeter detection systems, Perimeter protection, intrusion detection systems and many more terms for the same thing) are divided to two main fields: home burglar alarms and industrial burglar and perimeter intrusion detection.

Alarm types

Indoor

These types of sensors are designed for indoor use. Outdoor use would not be advised due to false alarm vulnerability and weather durability.

Passive infrared detectors

The passive infrared detector (PIR) is one of the most common detectors found in household and small business environments because it offers affordable and reliable functionality. The term passive means the detector is able to function without the need to generate and radiate its own energy (unlike ultrasonic and microwave volumetric intrusion detectors that are “active” in operation). PIRs are able to distinguish if an infrared emitting object is present by first learning the ambient temperature of the monitored space and then detecting a change in the temperature caused by the presence of an object. Using the principle of differentiation, which is a check of presence or nonpresence, PIRs verify if an intruder or object is actually there. Creating individual zones of detection where each zone comprises one or more layers can achieve differentiation. Between the zones there are areas of no sensitivity (dead zones) that are used by the sensor for comparison.

Ultrasonic detectors

Using frequencies between 15 kHz and 75 kHz, these active detectors transmit ultrasonic sound waves that are inaudible to humans. The Doppler shift principle is the underlying method of operation, in which a change in frequency is detected due to object motion. This is caused when a moving object changes the frequency of sound waves around it. Two conditions must occur to successfully detect a Doppler shift event:

The ultrasonic detector operates by the transmitter emitting an ultrasonic signal into the area to be protected. The sound waves are reflected by solid objects (such as the surrounding floor, walls and ceiling) and then detected by the receiver. Because ultrasonic waves are transmitted through air, then hard-surfaced objects tend to reflect most of the ultrasonic energy, while soft surfaces tend to absorb 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 considered obsolete by many alarm professionals, and is not actively installed.

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 outdoor applications. To reduce false alarms this type of detector is usually combined with a passive infrared detector or "Dualtec" alarm.

By generating energy in the microwave region of the electromagnetic spectrum, detector operates as an active volumetric device that responds to:

Photo-electric beams

Photoelectric beam systems detect the presence of an intruder by transmitting visible or infrared light beams across an area, where these beams maybe 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. Systems are available for both internal and external applications. 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.

Glass break detectors

The glass break detector may be used for internal perimeter building protection. When glass breaks it generates sound in a wide band of frequencies. These can range from infrasonic, which is below 20 hertz (Hz) and can not be heard by the human ear, through the audio band from 20 Hz to 20 kHz which humans can hear, right up to ultrasonic, which is above 20 kHz and again cannot be heard. 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 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 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.

The more primitive detection method involves gluing a thin strip of conducting foil on the inside of the glass and putting low-power electrical current through it. Breaking the glass is practically guaranteed to tear the foil and break the circuit.

Smoke, heat, and carbon monoxide detectors

Most systems may 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 detectors and heat detectors protect from the risk of fire and carbon monoxide detectors protect from the risk of carbon monoxide.

Outdoor

These types of sensors would be found most of the time mounted on fences or installed on the perimeter of the protected area.

Vibration (shaker) or inertia sensors

These 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 technology of the devices varies and can be sensitive to different levels of vibration. 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.

A rather new and unproven type of sensors use piezo-electric components rather than mechanical circuits, which can be tuned to be extremely sensitive to vibration.

Passive magnetic field detection

This buried security system is based on the Magnetic Anomaly Detection principle of operation. The system uses an electromagnetic field generator powered by two wires running in parallel. Both wires run along the perimeter and are usually installed about 5 inches apart on top of a wall or about 12"/30 cm below ground. The wires are connected to a signal processor which analyzes any change in the magnetic field.

This kind of buried security system sensor cable could be buried on the top of almost any kind of wall to provide a regular wall detection ability or be buried in the ground.

E-field

This proximity system can be installed on building 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. Both wires run along the perimeter and are usually installed about 800 millimetres apart. The sensing wire is connected to a signal processor that analyses:

These items define the characteristics of an intruder and when all three are detected simultaneously, an alarm signal is generated.

The barrier can provide protection from the ground to about 4 metres of altitude. It is usually configured in zones of about 200 metre lengths depending on the number of sensor wires installed.

Microwave barriers

The operation of a microwave barrier is very simple. This type of device produces an electromagnetic beam using high frequency waves that pass from the transmitter to the receiver, creating an invisible but sensitive wall of protection. When the receiver detects a difference of condition within the beam (and hence a possible intrusion), the system begins a detailed analysis of the situation. If the system considers the signal a real intrusion, it provides an alarm signal that can be treated in analog or digital form.

Microphonic systems

Microphonic based systems vary in design but each is generally based on the detection of an intruder attempting to cut or climb over a chainwire fence. Usually the microphonic detection systems are installed as sensor cables attached to rigid chainwire fences, however some specialised versions of these systems can also be installed as buried systems underground. Depending on the version selected, it can be sensitive to different 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 chainwire being cut, an intruder climbing the fence, or bad weather conditions.

The systems are designed to detect and analyse incoming electronic signals received from the sensor cable, and then to generate alarms from signals which exceed preset 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 accomplished during commissioning of the detection devices.

Taut wire fence systems

A taut wire perimeter security system is basically an independent screen of tensioned tripwires usually mounted on a fence or wall. Alternatively, the screen can be made so thick that there is no need for a supporting chainwire 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 tensioned wires. These switches or detectors can be a simple mechanical contact, static force transducer or an electronic strain gauge. Unwanted alarms caused by animals and birds 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.

Fibre optic cable

A fibre-optic cable can be used to detect intruders by measuring the difference in the amount of light sent through the fibre core. If the cable is disturbed, light will ‘leak’ out and the receiver unit will detect a difference in the amount of light received. The cable can be attached directly to a chainwire 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. Other types work on the detection of change in polarization which is caused by fiber position change.

H-field

This system employs an electro-magnetic field disturbance principle based on two unshielded (or ‘leaky’) coaxial cables buried about 10–15 cm deep and located at about 1 metre apart. 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 unobtrusive when it has been installed correctly, however care must be taken to ensure the surrounding soil offers good drainage in order to reduce nuisance alarms.

System connections

The trigger signal from each sensor is transmitted to one or more control unit(s) either through wires or wireless means (radio, line carrier, infrared). Wired systems are convenient when sensors (such as PIRs, smoke detectors etc.) require power to operate correctly, however, they may be more costly to install. Entry-level wired systems utilize a Star network topology, where the panel is at the center logically, and all devices "home run" its wire back to the panel. More complex panels use a Bus network topology where the wire basically is a data loop around the perimeter of the facility, and has "drops" for the sensor devices which must include a unique device identifier integrated into the sensor device itself (e.g. iD biscuit). Wired systems also have the advantage, if wired properly, of being tamper-evident. Wireless systems, on the other hand, often use battery-powered transmitters which are easier to install, but may reduce the reliability of the system if the sensors are not supervised, or if the batteries are not maintained. Depending on distance and construction materials, one or more wireless repeaters may be required to get the signal reliably back to the alarm panel. Hybrid systems utilize both wired and wireless sensors to achieve the benefits of both. Transmitters, or sensors can also be connected through the premises electrical circuits to transmit coded signals to the control unit (line carrier). The control unit usually has a separate channel or zone for burglar and fire sensors, and better systems have a separate zone for every different sensor, as well as internal "trouble" indicators (mains power loss, low battery, wire broken, etc.).

Alarm connection and monitoring

Depending upon the application, the alarm output may be local, remote or a combination. Local alarms do not include monitoring, though may include indoor and/or outdoor sounders (e.g. motorized bell or electronic siren) and lights (e.g. strobe light) which may be useful for signaling an evacuation notice for people during fire alarms, or where one hopes to scare off an amateur burglar quickly. However, with the widespread use of alarm systems (especially in cars), false alarms are very frequent and many urbanites tend to ignore alarms rather than investigating, let alone contacting the necessary authorities. In short, there may be no response at all. In rural areas (e.g., where nobody will hear the fire bell or burglar siren) lights or sounds may not make much difference anyway, as the nearest responders could take so long to get there that nothing can be done to avoid losses.

Remote alarm systems are used to connect the control unit to a predetermined monitor of some sort, and they come in many different configurations. High-end systems connect to a central station or responder (e.g. Police/ Fire/ Medical) via a direct phone wire (or tamper-resistant fiber optic cable), and the alarm monitoring includes not only the sensors, but also the communication wire itself. While direct phone circuits are still available in some areas from phone companies, because of their high cost they are becoming uncommon. Direct connections are now most usually seen only in Federal, State, and Local Government buildings, or on a school campus that has a dedicated security, police, fire, or emergency medical department (in the UK communication is only possible to an Alarm Receiving Centre - communication direct to the emergency services is not permitted). More typical systems incorporate a digital telephone dialer unit that will dial a central station (or some other location) via the Public Switched Telephone Network (PSTN) and raise the alarm, either with a synthesized voice or increasingly via an encoded message string that the central station decodes. These may connect to the regular phone system on the system side of the demarcation point, but typically connect on the customer side ahead of all phones within the monitored premises so that the alarm system can seize the line by cutting-off any active calls and call the monitoring company if needed. Encoders can be programmed to indicate which specific sensor was triggered, and monitors can show the physical location (or "zone") of the sensor on a list or even a map of the protected premises, which can make the resulting response more effective. For example, a water-flow alarm, coupled with a flame detector in the same area is a more reliable indication of an actual fire than just one or the other sensor indication by itself. Many alarm panels are equipped with a backup dialer capability for use when the primary PSTN circuit is not functioning. The redundant dialer may be connected to a second phone line, or a specialized encoded cellular phone, radio, or internet interface device to bypass the PSTN entirely, to thwart intentional tampering with the phone line(s). Just the fact that someone tampered with the line could trigger a supervisory alarm via the radio network, giving early warning of an imminent problem (e.g., arson). In some cases a remote building may not have PSTN phone service, and the cost of trenching and running a direct line may be prohibitive. It is possible to use a wireless cellular or radio device as the primary communication method.

Broadband Alarm Monitoring

Increasing deployment of voice over IP technology (VoIP) is driving the adoption of broadband signaling for alarm reporting. Many sites requiring alarm installations no longer have conventional telephone lines (POTS), and alarm panels with conventional telephone dialer capability do not work reliably over some types of VoIP service.

Dial up analog alarm panels or systems with serial/parallel data ports may be migrated to broadband through the addition of an alarm server device which converts telephone signaling signals or data port traffic to IP messages suitable for broadband transmission. But the direct use of VoIP (POTS port on premises terminal) to transport analog alarms without an alarm server device is problematic as the audio codecs used throughout the entire network transmission path cannot guarantee a suitable level of reliability or quality of service acceptable for the application.

In response to the changing public communications network, new alarm systems often can use broadband signaling as a method of alarm transmission, and manufacturers are including IP reporting capability directly in their alarm panel products. When the Internet is used as a primary signaling method for critical security and life safety applications, frequent supervision messages are configured to overcome concerns about backup power for network equipment and signal delivery time. But for typical applications, connectivity concerns are controlled by normal supervision messages, sent daily or weekly.

Various IP Alarm transmission protocols exist but most in use today are proprietary. Just as the formats used for conventional telephone reporting were standardized and published, broadband signaling for alarm reporting is being standardized today. In 2007, US alarm manufacturers developed an open standard called DC-09. This standard has been accepted as an American National Standard, and is published as ANSI/SIA DC-09-2007. [ref: ANSI/SIA DC-09-2007] The protocol provides an encoding scheme and transport mechanism to carry data from 17 previously defined alarm protocols, including the latest Contact ID, SIA DC-03 and SIA 2000 protocols. [ref: ANSI/SIA DC-07-2001.04] Several manufacturers of panels and receivers are reported to be developing or have released support for DC-09.

Listen In Alarm monitoring

Monitored alarms and speaker phones allow for the central station to speak with the homeowner and/or intruder. This may be beneficial to the owner for medical emergencies. For actual break-ins, the speaker phones allow the central station to urge the intruder to cease and desist as response units have been dispatched.

Alarm monitoring Services

The list of services to be monitored at a Central Station has expanded over the past few years to include: Access Control; CCTV Monitoring; Environmental Monitoring; Intrusion Alarm Monitoring; Fire Alarm & Sprinkler Monitoring; Critical Condition Monitoring; Medical Response Monitoring; Elevator Telephone Monitoring; Hold-Up or Panic Alarm Monitoring; Duress Monitoring; Auto Dialer tests; Open & Close Signal Supervision & Reporting; Exception Reports; and PIN or Passcode Management. Increasingly, the Central Stations are making this information available directly to end users via the internet and a secure log-on to view and create custom reports on these events themselves.

Alarm response

Depending upon the zone triggered, number and sequence of zones, time of day, and other factors, the monitoring center can automatically initiate various actions. They might be instructed to call the ambulance, fire department or police department immediately, or to first call the protected premises or property manager to try to determine if the alarm is genuine. They could also start calling a list of phone numbers provided by the customer to contact someone to go check on the protected premises. Some zones may trigger a call to the local heating oil company to go check on the system, or a call to the owner with details of which room may be getting flooded. Some alarm systems are tied to video surveillance systems so that current video of the intrusion area can be instantly displayed on a remote monitor, not to mention recorded.

The first video home security system was patented on December 2, 1969 to inventor Marie Brown. The system used television surveillance.

Access control and bypass codes

To be useful, an intrusion alarm system is deactivated or reconfigured when authorized personnel are present. Authorization may be indicated in any number of ways, often with keys or codes used at the control panel or a remote panel near an entry. High-security alarms may require multiple codes, or a fingerprint, badge, hand-geometry, retinal scan, encrypted response generator, and other means that are deemed sufficiently secure for the purpose.

Failed authorizations should result in an alarm or at least a timed lockout to prevent "experimenting" with possible codes. Some systems can be configured to permit deactivation of individual sensors or groups. Others can also be programmed to bypass or ignore individual sensors (once or multiple times) and leave the remainder of the system armed. This feature is useful for permitting a single door to be opened and closed before the alarm is armed, or to permit a person to leave, but not return. High-end systems allow multiple access codes, and may even permit them to be used only once, or on particular days, or only in combination with other users' codes (i.e., escorted). In any case, a remote monitoring center should arrange an oral code to be provided by an authorized person in case of false alarms, so the monitoring center can be assured that a further alarm response is unnecessary. As with access codes, there can also be a hierarchy of oral codes, say, for furnace repairperson to enter the kitchen and basement sensor areas but not the silver vault in the butler's pantry. There are also systems that permit a duress code to be entered and silence the local alarm, but still trigger the remote alarm to summon the police to a robbery.

Fire sensors can be "isolated", meaning that when triggered, they will not trigger the main alarm network. This is important when smoke and heat is intentionally produced. The owners of buildings can be fined for generating False alarms that waste the time of emergency personnel.

False / no alarms

System reliability can be a problem when it causes nuisance alarms, false alarms, or fails to alarm when called for; in all cases, the costs are significant. In many jurisdictions, law enforcement fees for multiple false alarms are significant, and even lead to loss of service, while losses due to undeterred crimes can be large or even priceless. Approximately 1% of police alarm calls actually involve a crime. Nuisance alarms occur when an unintended event evokes an alarm status by an otherwise properly working alarm system. A false alarm also occurs when there is an alarm system malfunction that results in an alarm state. In all three circumstances, the source of the problem should be immediately found and fixed, so that responders will not lose confidence in the alarm reports. It is easier to know when there are false alarms, because the system is designed to react to that condition. Failure alarms are more troublesome because they usually require periodic testing to make sure the sensors are working and that the correct signals are getting through to the monitor. Some systems are designed to detect problems internally, such as low or dead batteries, loose connections, phone circuit trouble, etc. While earlier nuisance alarms could be set off by small disturbances, like insects or pets, newer model alarms have technology to measure the size/weight of the object causing the disturbance, and thus are able to decide how serious the threat is, which is especially useful in burglar alarms.

False-Alarm Reduction

Home and business owners can now choose a new type of keypad control panel designed to help reduce false alarms.

Based on a standard called CP-01-2000, developed by the American National Standards Institute and Security Industry Association , the new generation of keypad control panels takes aim at user error by building in extra precautions that minimize unwarranted dispatch of emergency responders.

Some of the features of CP-01 keypads include a progress annunciation function that emits a different sound during the last 10 seconds of delay, which hastens exit from the premises. Also, the exit time doubles if the user disables the pre-warning feature.

Other "rules" address failure to exit premises, which results in arming all zones in Stay Mode and a one-time, automatic restart of exit delay. However, if there is an exit error, an immediate local alarm will sound.

Cross zoning reduces alarms

Cross zoning is an innovative alarm-system strategy that does not require a new keypad. Using multiple sensors to monitor activity in one area, advanced software analyzes input from all the sources.

For example, if a motion detector trips in one area, the signal is recorded and the central-station monitor notifies the customer. A second alarm signal - received in an adjacent zone in close time proximity, is the confirmation the central-station monitor needs to request a dispatch immediately. This builds in increased protection and a fail safe should a door blow open or a bird rattle an exterior window.

Enhanced Call Verification

Enhanced Call Verification (ECV) helps reduce false dispatches 25-50% while still protecting citizens, and is mandated in several US jurisdictions, although the alarm industry has successfully opposed it in others. ECV requires central station personnel to attempt to verify the alarm activation by making a minimum of two phone calls to two different responsible party telephone numbers before dispatching law enforcement to the scene.

The first alarm-verification call goes to the location the alarm originated. If contact with a person is not made a second call is placed to a different number. The secondary number, best practices dictate, should be to a telephone that is answered even after hours, preferably a cellular phone of a decision maker authorized to request or bypass emergency response.

Video verification

Video verification documents a change in local conditions by using cameras to record video signals or image snapshots. The source images can be sent over a communication link, usually an Internet protocol (IP) network, to the central station where monitors retrieve the images through proprietary software. The information is then relayed to law-enforcement and recorded to an event file, which can later be used as prosecution evidence.

An example of how this system works is when a passive infrared or other sensor is triggered a designated number of video frames from before and after the event is sent to the central station.

A second video solution can be incorporated into to a standard panel, which sends the central station an alarm. When a signal is received, a trained monitoring professional accesses the on-site digital video recorder (DVR) through an IP link to determine the cause of the activation. For this type of system, the camera input to the DVR reflects the alarm panel’s zones and partitioning, which allows personnel to look for an alarm source in multiple areas.

Independent certification

Some insurance companies and local agencies require that alarm systems be installed to code or be certified by an independent third party. Independent certification ensures a system meets a level of criteria above and beyond what a sales representative may offer. The alarm system is required to have a maintenance check carried out every 6 – 12 months (in the UK, 'Audible Only' intruder alarm systems require a routine service visit once every 12 months and monitored intruder alarm systems require a check twice in every 12 month period) to ensure all internal components, sensors and PSUs are functioning correctly. In the past, this would require an alarm service engineer to attend site and carry the checks out. With the use of the Internet and a compatible IP transmitting device (at the alarmed premises) some checks can now be carried out remotely from the central station. This insures you have a system that will be reliable when needed. 3rd party alarm certifying agencies include:

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2011/04/07

Burgalar alarms