Here you will find out how an alarm systems individual components are put together. What each of these components does and how it is supposed to work.

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The purpose of a detector is to react to change. That is movement, temperature or perhaps humidity among many others variations.The most well known are perhaps motion detectors, which tell us when a burglary is taking place, or in other words, when they detect movement..

There are two main types of movement detectors, Passive Infrared (PIR), Ultrasonic, and Dual Technology.

Passive infrared.(PIR)
The most popular of these and probably the most reliable, is the passive infrared detector or PIR as it is referred to, works by sensing heat change.

In front of it`s heat collector there are a series of lens which divide the area in front of it, into zones, both verticaly and horizontaly. The area the lenses cover can be from 5 degrees, for a narrow screen effect, to 120 degrees or more, for a wider coverage. The zones are sensitive areas and can extend to as far as 40 meters or about 120 feet in front and to the side of the detector. Movement of a person in front of a detector is registered as a change in heat level and if that change occurs above a preset set of parameters then the detector will go into an alarm state and trigger the response that the system is programmed to give. To avoid false alarms the detector can be programmed in a way that two, and not one alarm state within a set time must occur to generate an alarm. The PIR detector, because it reacts to heat, needs to be placed with care. It should not be placed where it can "observe" the sun, or too close to heaters (particularly those that turn themselves on and off). Glass surfaces can "stress" a detector in that it is unsure if it is looking at glass or the area beyond the glass. It would not be particularly wise to put one in a kitchen, for example, where there are many elements that would effect the health of a detector, like steam, smoke, fat and heat, all of which are almost certain to effect the functioning of any form of detector. PIR detectors are most effective when an intruder crosses in front of the detector .

Ultrasonic detectors, as the word implies, use sound to detect movement. The detectors are active in that they are sending out and receiving ultrasonic signals. By using the "doppler effect", these detectors can "hear" the difference in sound when objects move within its listening range. This type of detector is often used in places where conditions do not allow a PIR to be used. Whilst technology today is much improved, ultrasonic detectors can be a touch temperamental and have a tendency to react to sharp / loud sounds. They cannot be used in a shop that has posters that swing in the ventilation system or doors that may move in a draught. (Many years ago when the technology was in it`s infancy and telephones had bells, these detectors would activate if the telephones rang). As with the PIR, these detectors have their uses and their positioning is critical for reliable use. Ultrasonic detectors are most effective when an intruder walks toward or away from the detector.

The Dual Technology detector is something different in that it uses microwaves and PIR detector . They are rather more expensive than the other two types of movement detectors, and use more power. They are used in circumstances of special demand, and only trigger when both pir and microwave are triggered.   Therefore making them suitable for a number or enviorments.

Magnet detectors are fastened to doors or windows and consist of a permanent magnet placed in the woodwork of a door or window, which when closed will cause the magnet to come in close proximity to a magnetic switch. If the door or window is opened then the switch is no longer held closed by the magnet and an alarm is created. These are also often used on doors to activate a chime when people enter. They are robust, tamper proofed and widely used.

Glass detectors come in two main versions. The one version is fastened to the glass and reacts to the frequency of breaking glass, or metal against glass. Uncomplicated, fairly reliable but can be activated by accident under certain circumstances. Then there second type which is based on a filtered microphone, and is typicaly, fastened to a wall close to the glass. These react to the frequency of breaking glass. This type of detector manages to filter out all the other sounds that could cause a false alarm. Widely available and reliable. Detection area is limited in both types of detectors, to within a maximum effective distance.

Seismic detectors are sensitive to a frequency range that covers vibration. These are used on safe doors, walls or roofs. A bank may have seismic detectors on the six surfaces of the vault in addition to light sensitive detectors inside and around the enclosing walls, in addition to movement detectors in the area inside and around the walls of the vault.

Water detectors are, as the name implies, sensitive to damp and water.

A small detector is placed on the floor, (for example, outside the bath room), to detect any leakage of water. Water coming in contact with the detector will cause changes in the resistance of the detector, which in turn will be interpreted by the sensor as water, or at least liquid. Handy in winter for warning of burst pipes and in places where there is a danger of water spillage, such as the rooms where there are washing machines and dish washers.

Temperature detectors are sensitive to changes of temperature within certain preset parameters. For example, a deep freeze that fails, or in the other direction, a machine that runs above a safe temperature. A typical situation is in the data room of a large company where computers and servers must remain between predetermined temperature limits.

Video detectors are not new but the technology to move pictures from one place to another is always improving. A video detector will react to movement. The detectors memorizes the picture in front of it and react to changes in that picture. To save band width the alarm system will send only the changes in the picture to a monitoring station and not the whole picture every time. The program that handles the pictures will point out the cause of the alarm by pointing to or highlighting the area of the picture that has changed. These systems used to be extremely expensive, but today are relatively cheap, dependant on the usage and quality of the pictures required. The pictures, ideally need to be of high definition to ensure that they can be used for identification purposes. Not all monitoring stations are willing to take in these signals so it is a good idea to check first. Most banks and other establishments store the alarm pictures locally as well as sending them over to the monitoring station. Similar systems are used in banks and shops where the picture is a continuous video recording, and not triggered by a detection device. These recordind tapes are stored for several weeks before being reused.

Fire detectors Smoke detectors offer the earliest warning of fire and should be included in your security system. Most deaths from nighttime fire occur from smoke inhalation because the victim doesn't wake up. Your home security system is best equipped to awaken you and call for help. Your fire system remains active, even when the burglar alarm is turned off.

They work in one or in a combination of three ways, either by reaction to the gasses produced by fire, optically, by heat or a combination of the different types. They can be integral with the central alarm system thus eliminating the need to buy batteries ,mains powered or stand alone battery powered. Smoke / fire detectors should be checked at least once a month. It is possible to buy a spray can that simulates the gasses produced in a fire to test that they work properly. Pushing the button is not good enough on it`s own, that only checks the sound. Regular dusting of the housing is advised

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This is the heart of an alarm system. This is the box that hangs on the wall and monitors every thing that is happening to all it`s other components. The simple version is preprogrammed, whilst the complex version has many different programming possibilities. It continually monitors the tamper circuits of the whole alarm system, from detector level to communications level. It continually watches over the status of the detector zones and individual detectors. It ensures that the power supply throughout the system is up to specs. and it monitors itself internally to pick up on any system failure. It monitors the communications between itself and the central monitoring station to ensure that there is always a connection. It is here, at the control panel, that all the programming is done, that tells the system how it should react, and when it should react, to all the information it receives, both locally and often also, from a distant station. It can be programmed to allow a guard to take a particular route through an industrial complex, but to react if he wanders into the wrong areas. In a similar way it will allow the owner of a house to go into the house using a defined door and give maybe ten seconds for him / her to turn off the alarm. It controls how long and if, a siren or bell should sound, and how a signal should be sent to the local monitoring station. It will keep a record of all incidents regarding the use of the alarm system such as when it was turned on and off and which codes were used to do so, thereby identifying the user when multiple coding is used this option is only available on the more expensive units. It also decides where to send the various signals, fire,intruder.

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access is by use of either a key, to turn off or to activate a delay mechanism, by a code lock that requires a code to deactivate the system, or by a remote wireless device that will activate a delay mechanism so the a person has the time to go into the area covered by the alarm , to turn it off. All delay systems, when used, have a timer and will turn the delay off automatically after the preprogrammed time expires. The key pad or code pad often offers the same facilities as the control panel keypad so that the system can be programmed directly from the pad. A more complex routine requires that the person entering the area has to ring the central monitoring station, identify him / herself by code, after which the alarm system will be instructed by the monitoring station to allow the person a limited number of attempts to punch in their code, or so many seconds to turn off the alarm. Codes should be changed regularly and these can normally be changed at the key pad with help of a master code.

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Sirens or bells are the standard audible warning sounds used by alarm systems. Each has it`s own backup battery which will power the unit if an intruder should cut the wires. Cutting any wires to an alarm system will result in an active alarm situation and a tamper   warning. Bells and sirens with their own power supplies will sound. In some situations it is desirable that when the alarm is activated there is no audible warning, but that a signal is sent to a monitoring station in silence, so that Police or secutity guards can react without the intruder realizing it. Often used for robbery alarms or in health institutions and hospitals. Backup batteries should be checked regularly and changed regardless every third year. Most bell units in the U.K. are fitted with a cut off timer as required by each areas Local Authority.

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When an alarm is activated by a detector of any type, the control panel  will activate the audible devices and, if so programmed, send a warning to the local monitoring station to initiate a reaction. This transmission of signals is either via the local telephone lines or by wireless. Systems that use the telephone lines should have the facility to check that the line is in working order and send a warning to the monitoring station if not. In many parts of the world where the telephone net is not reliable, a wireless solution is the preferred method. In other parts of the world the local telephone companies offer a special network for alarm transmissions. This network is continually and automatically checked for integrity every few seconds.

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Conditions:- All services are given on the understanding that conditions and legal commitments can vary from country to country. Advice is given in good faith, but it is up to the individual to make the final decision regarding the practicability and legality of following any advice given