Monday, July 28, 2008

What is Burglar Alarm???

Central Control Unit
The Burglar Alarm control panels available in the market range from small compact type which incorporates a hooter / siren and can accommodate a few different types of Sensors (detectors) to a more advanced type which can perform more complex functions like, automatic dialing to a phone, cellular phone and convey a pre-recorded message informing about intrusion, in addition to or in place of, local audio visual alarm.The advance burglar alarm versions also have the capability of functioning with user codes for arming and disarming and of switching over to built-in power supply in case of power failure. Many control units also use a remote (infra-red or Radio Frequency based) for arming or disarming of the control unit.For larger installations that have more sensors, there is provision of Zones. Each Zone is associated with one or more sensors e.g. one floor could be controlled by one Zone. The advantage of Different types of Zones is that when the alarm goes off (alarm sounds), the control panel gives an indication as to which Zone has been compromised. This way one has to only check the sensors linked to that particular zone to see where the problem is.Please note that many times the sensor, control unit & alarms unit may be combined in a single housing for reducing cost or to provide easy localized, protection. However, larger systems involving multiple sensors will invariably have a separate control unit.Burglar Alarm control panel is the brain of your security system. It is typically placed in an area that is out of the way like a basement, attic, closer or office. The motherboard and additional components such as radio receivers, backup power supply and zone expanders are inside this metal box which is often locked. You will have little or no interface with the alarm control. Your alarm technician will need to access this unit to program it and wire it to general standards, or your custom standards.
Arming / disarming system
Arming a burglar alarm in a loose sense is switching on the system and disarming is disabling (switching off) the system. These functions can be performed using a simple switch or by using a keypad in which the user is supposed to enter a password.In advanced burglar alarm systems, this may be done by an (Radio Frequency) RF remote or an Infrared remote. In cost effective systems, this is done using a traditional key that operates an electric switch. Such key-based systems are convenient for use by all age groups and offer more flexibility in terms of increasing number of authorized users. Some of the systems also have a keypad in which the owner is supposed to enter the correct password to do any arming/disarming.The infrared remote requires that the operator of remote be in visual line of sight of the receiver that is on the control panel, where as the Radio Frequency remote can operate the control panel from anywhere (as long as the receiver is in the range) In addition to arming/disarming the control can support many other functions which may not be available (or even desired) in every control panel.
Power Back-up
All burglar alarm controls should be equipped with sufficient battery standby to operate the system for the maximum duration of outages you are likely to experience in your area. Do remember that the chargeable battery deteriorates with time. The life of a chargeable battery is normally half after one year of usage and requires replacement after 18 months. The amount of batteries needed depends upon the type and amount of devices used and how long you want the system to function without normal electrical power.
Wired or wireless
Central Control Panels can use wired, wireless, or a combination of wired and wireless devices to communicate with sensors or alarms. The type you use depends upon many factors such as ease of wiring, building construction, and cost.Wireless burglar alarm systems have a much higher equipment cost and require battery changing frequently, but can be installed very quickly. Wireless option, as the name suggests, does not require wires running all over the house. Wireless burglar alarm is also good when you want to have detectors installed in unattached garages or sheds. If you decide to use wireless make sure that the system supervises every transmitter for low battery transmitter health check. It is critical to check the wireless system for a few days to verify that it works properly and there is no interference for other electronic items. Wireless systems normally have special checks built-in to save from false alarms.Wired systems are more cost effective and reliable, as long as you can bear the inconvenience of wiring.
Burglar Alarm Zone, in general terms represent an area or collection of sensors that protect an area. Zones allow to pinpoint the area from where the alarm got initiated, otherwise one has to use guess-work & check all doors & windows for intrusion. In large premises, such a feature is very desirable, though it increases the cost. Make sure that your Central Control Panel can be expanded (or has built-in flexibility) to meet your future needs or you may be faced with replacing the control Panel when you want to add devices.Lets look at a typical zone layout for a control panel so that you can understand the way it is wired and programmed works.
ZONE 1 – (DELAY): This zone is where the doors from which most often enter and exit are. When you turn your alarm on, the exit delay will start a timer (programmed to your specifications, if requested) allowing you time to get out. Once the exit time has expired, (usually about 30-60 seconds.) the alarm will be in the on or “armed” condition.
When you return to your home or business and enter through the delay doors, an entry timer begins. This timer is usually set at about 15-30 seconds. You do not want to have a long entry time as a burglar entering through a delay zone has the same amount of time in your protected area before the alarm goes off. During this time you would go to the nearest keypad and enter your code to turn your alarm off.
In the Know!
The doors have chime feature that can easily be turned on or off. Most people elect to leave this feature on all this time, so that they can hear a tone when the alarm is off and someone enters.
ZONE 2 – (INSTANT PERIMETER): This zone would be for other than delay doors. The back yard door and the master bedroom to deck doors and good examples of these types of doors. There is no delay time timer on these doors and when the alarm is on and entry is made the alarm will go off instantly.
ZONE 3 – (INTERIOR): This zone is for your motion detector on the main floor. When you enter through a delay door the motion will delay also, giving you the ability to get to the keypad turn off or “disarm” your system. If you do not enter through a delay door first and the motion sees you it will go into an alarm condition instantly. When you are staying home or arming your business system without leaving, you can arm your interior zone or zones allowing you to move around without restrictions while still having your perimeter secured.
ZONE 4 – (INTERIOR): This zone is for your windows if your house is in Ground Floor and for the customers those who are asking selectively arm or disarm certain doors / windows to protect the particular zone specifically.
Types of ZonesZones fall in various categories depending upon kind of response desired e.g. medical, burglary, and panic. Each type of device could have a specific activation, alarm and response procedure. Some examples of zone are: Hold-up zones can be audible or silent but are always active. You may choose either or both. Audible hold-up can be used to "scare' away prowlers but care must always be exercised when activating hold-up devices since there is no way of predicting the action an intruder may take when he hears the alarm or when the police arrive. By connecting to an Auto Dialer the control panel can 'silently' call for help.
Burglary devices fall into various categories, 24 hour (always active), main entry door, and interior (motion detectors) etc. While going away, you will like to monitor the premises on 24 hours basis. Whereas, if you are at home, you might like to arm (activate) the external doors & windows but not PIR's which monitor the interior. You may also want to selectively arm or disarm certain doors / windows.
Information Input
Advanced Burglar Alarm control panels have displays that may be LCD (liquid crystal display) based or simple LED lights. They can prompt you for the required data, such as Enter Code when the system is activated and provide a clear visual indication of the system status. Some systems also give audible beeps depending upon if the input has been accepted by the system or not.Most of the systems have built-in checks to verify the authenticity of the person entering inputs. The key-pad based system requires the user to enter correct password to perform any function. By giving the password to near & dear ones, the need to have multiple keys is not these. Also, key protection & control could be a problem in case there are many authorized 'individuals'
All central control panels have some form of output or another. Most of them activate an internal and/or external hooter. Some can also be equipped with relays that can be controlled from the Control Panel itself. These relays can allow you to perform many functions such as AC/Heater control or as a means of interfacing with a home automation system.The output of control panel may be given to a Help intimation device such as an Telephone Auto Dialer.
Zone bypassing and forced arming
Sometimes you may want to disconnect OR bypass part of the protected area e.g. in case of a fault in part of the system or when for some reason you do not want to protect a specific area. Such situations can be handled only if the system allows selectively bypassing or arming at a zone level.
AccessoriesFor a complete protection system, it is important to assess the threat level and then carefully choose various sensors and accessories, keeping in mind the cost and utility. While for a smaller installation it is feasible to do the selection on 'do-it-yourself' basis, however for larger installations, it is advisable to take professional help. Using the expert advice, you might actually be able to get a better system at a lower cost.
Magnetic switchMagnetic switches are the most common sensing devices for sensing opening and closing of doors and windows. They are cheap and reliable.Such sensors consist of two parts - A contact switch that is installed on the door / window frame and an Activating magnet that is mounted on the door. The magnetic switch is held in no-alarm contact position when door / window is kept closed. These are installed on a door or window in such a way that opening the door or window causes the magnet to move away from the contact switch which activates the alarm. They have proved to be a tried and tested method of monitoring any of the operable openings in the houses / apartments. These contacts are available in variety of finishes & materials. Heavy duty versions are also available for heavy doors, shutters and gates. The magnetic switches normally have both 'Normally open' & 'Normally Closed' contacts for easier integration with existing systems. While installing care should be taken that alarm should go off when the door just opens. If the sensor is wrongly placed then it is feasible that a person may be able to squeeze in without activating the sensor. A series of such sensors can cover the whole house including every door / window / ventilator. The Magnetic switches need to be connected to Control unit , which senses the change in the position of door and activates an alarm.In Wireless burglar alarm systems , the principle is the same except no wires are required to connect the sensor to the Control Unit.In cases a window has to be left a little open for ventilation, it is made possible by using 2 magnets and 1 switch. In this configuration the first magnet is mounted in the window closed position and the second is mounted in a location where it will align with the switch when the window is open a few inches, typically 3 or 4 inches. This allows for ventilation but will sound the alarm if the window is fully opened. Window or wall mounted air conditioners and Coolers may also require protection if they can be easily removed from the opening. The standard method used to protect these units is to install a sensor on the unit.Advanced versionFor more sensitive control of the door, there is an advanced version called Balanced Magnetic Switch, in which the electrical contact of the switch is held in no-alarm condition by two magnets - one is fixed to the door frame and the other magnet is fixed to the corresponding position on to the door. As long as the magnetic field remains balanced with the door firmly closed, the contacts within the switch would be in no-alarm condition. Even with a slight movement of the door from the door frame the magnetic field gets unbalanced causing the Control Unit to sound an alarm. The balanced magnetic switch is more tamper-resistant than a simple Magnetic switch but requires higher skill and time for installation.
Passive Infrared Sensors (PIR)
Passive Infrared (PIR) Motion Sensors protect space by 'looking' for changes in infrared (heat) energy levels caused by movement of an intruder. The passive infrared detectors are passive devices. i.e., they do not transmit any form of energy. When a person enters and moves within the detecting zone, his body which is at its normal temperature of 98.6 degree F., radiates more (or less) thermal energy than the surroundings and such minute difference in thermal energy is detected by the PIR. In simple words, PIR keeps a picture of the heat levels in its view and keeps on comparing the new view with the stored one. In case there is any change then they activate the alarm. PIR's come with a wide variety of detection patterns to meet various needs of indoor movement sensing. Depending upon the type of protection needed and the size of the protection area / volume, the specific parameters of angular and area coverage can be chosen from the vast array of PIR types available. The standard PIR has wide angle coverage with a typical range of 20 to 30 feet. The Narrow angle PIR is for long range covering a long and narrow corridor. The Extra wide angle PIR is for sensing movements through an angle of 150 degrees. Then there are certain specialized PIR:
Roof counted PIR to detect movement in a circular space in the room.
Curtain type vertical pattern to detect access through windows, doors and other entry points and also to give protection to objects hung on a wall
Curtain type horizontal pattern to detect access through ceilings or skylightsWhen installed outside the entrance, this may be used to warn of any one approaching the entrance. Lighting also can be coupled to come ON automatically along with the chiming / alarming on sensing movements. PIR's can be used as a stand-alone system (when connected with an output device) or it can also form part of an integrated system along with other types of security devices. If PIR is used as a sensor in a larger Security system which is controlled by a Control Unit , then the Control Unit decides about the action to be taken.Some PIR's units have a built in key pad to enter the password for activation and deactivation. Some come with a remote control to activate and deactivate. Such PIR’s usually have a built in alarm also, which keeps on till it is deactivated.
Avoiding false alarms with PIRPIR must not point towards a heat producing source like Refrigerator, AC, heater etc. Also, while installing it should be so positioned that the intruder cannot approach the PIR without coming in view of the PIR else he can point the PIR elsewhere or deactivate the same without sounding the alarm. Precaution is required if there are pets in the house. PIR's are sensitive enough to detect dogs and cats. There are special lens available (or a tape can be put on lower part of the existing lens) so as to avoid detection close to the ground. At the same time, it should be kept in mind thatthe intruder can also crawl and avoid detection. So placement and subsequent testing of PIR's is a must to avoid false alarms.If PIR is being installed outdoors then one must keep in mind that the large birds and even pigeons can activate the alarm. So, it must be placed at such a location that PIR does not aims at the flight path of the birds. Due to such restrictions it is not always possible to use a PIR outdoors but it is one of the most used security device.
Glass break detector - vibration type
Glass Break Acoustic detectors "listen" for the specific sound pattern generated when glass breaks, while Vibration type sensors "feel" for the vibration of breaking glass. The vibration type of glass break detector is fixed on to the glass surface and is designed to respond to the specific higher frequency energies generated in breaking glass and not to the low-frequency vibrations produced while hitting the wall.Such sensors have lesser range of detection.
Vibration detector
Most of the sensors detect opening of a door, window or breakage of glass or movement of human beings. But it is equally important to detect if there is a break-in attempted through walls, ceiling or floors. This can be detected with the help of vibration Detectors.The detector operates on the principle of resonance of frequency. When the external impulse frequency due to hammering or chiseling matches with the resonance frequency of the sensing element, the alarm is triggered off. False alarms are avoided with proper setting of the intensity controller. The vibration detector can be fitted to windows, door frames, walls, ceilings etc. A typical vibration detector is effective up to 2.5 meters depending upon its location and the material to which it is fixed. Each detector can set to its own optimum level of sensitivity. There should be a sensor for every 20 ft of wall accessible to the intruder. Sensitivity should be adjusted to suit local vibration requirement.
Automatic Telephone Dialer (Auto dialer)The Automatic telephone dialer is an instrument that can automatically dial a fixed number of telephone numbers and deliver a message at each of the telephone numbers, without the help of any operator. The telephone numbers and the message can be stored by the user (in his own voice) and can be modified whenever required. When this instrument is activated, it starts dialing the telephone numbers in sequence and delivers the recorded message on each of the stored numbers. The system can re-dial to take care of busy numbers. The system works on normal telephone line. It does not need a dedicated telephone line. There are two types of Auto dialers in the market - One that uses electronic chip to record and play the voice message and the other one uses the usual Cassette for this purpose. The electronic chip is the preferred one on account of following:
There is no fear of jamming of the tape
No deteriorating of performance with time because of rubber belts getting weak
Requires very low current to operate since there are no mechanical parts nor are there any motors that require heavier current.
Always the same quality of voice as the playing speed is not dependent of the voltage of batteries.
Salient Features of an Auto dialerAn Auto dialer has small microcomputer that controls all functions. The emergency dialer takes priority over all incoming phones and faxes. This implies that the dialer cannot be disabled by keeping the line busy on which the dialer is installed. The salient features of popular Auto dialers are:
EPROM retains memory permanently
Can be activated by NO/NC contacts
Password protection to guard against unauthorized use
Test dialing facility
Can re-dial up to 3 times
Can work on Tone and Pulse telephone lines
Provision to activate external alarm if tampered (alarm system not included)
Special protection against lightning effects on telephone line
The Wired Auto dialer is connected with wires to the main control unit whereas the Wireless Auto dialer does not use wired to connect to the Control unit. It is to be noted that in both cases the connection to the telephone wires is by physical wires.
Panic Alarms
Panic devices are manually activated units that you can activate if you need immediate assistance. These units can either be silent or activate loud alarms. If you desire the silent version then you must have your system monitored. You should bear in mind that activating these units (especially those raise an alarm) may alert the intruder to your actions, so care must be exercised in their use.Panic devices can be fixed buttons, portable wireless buttons, or a special combination with a keypad. A variation on the panic device is Medical Alert. When the Panic Alarm is activated, then it can trigger off the alarm that can scare the intruder as well as alert everyone in the house. Optionally this can be connected to an Automatic Telephone Dialer also which can call up predefined numbers & convey pre-recorded message in your voice (to friends or police).Such systems are ideal to face emergency situations e.g. confrontation with intruder at night, holdups in office/banks/homes, confrontation with a visitor at door etc. The Wireless system consists of a small hand held transmitter unit which can optionally be worn as a pendant with a neck chain or worn as a wristwatch or simply kept in the pocket and a receiver unit which is mounted on the ceiling/wall. At the time of an emergency, the compact hand held units are simply operated by pressing the button or pulling off the neck chain. The signal transmitted is picked up by the receiver unit which in turn sends it to the security personnel or any other designated device/person.Alternatively, the receiver could be interfaced with an Auto dialer which can dial automatically any desired number or the Receiver may simply activate an audible alarm. Larger version of the system provides for a multi-channel receiver which can handle multiple transmitting signals from one or more individual transmitting units. Each transmitter is individually coded which makes it possible to identify the initiator of the alarm and hence the location where the incident has taken place at the receiving end. Such systems are useful for nursing homes, apartment complexes etc. With a single multi-channel receiver, the system can be extended to cover most of the apartments in the same / adjacent block falling within the operating range of the system. Effective functioning of the system will give the much needed peace of mind and reassurance to all the families covered by the system, especially to house wives and elderly couples, who live alone in unpredictable circumstances.
Security / Automatic Lights
Security lights get switched on whenever it detects an intruder within its field of view. Such systems may be based on PIR or Photosensitive sensors. A PIR may be connected to normal lights to make security lights (requires technical knowledge). Security lights are very useful to scare the intruders especially if these lights are employed in the compound or on the roof tops. When the lights are switched ON, the intruder feels that he has been detected and the owner is trying to confirm this. Normally this will deter the intruder for making any further attempt.For safety and security of homes and offices specially when there is no one in the house automatic/timer based lights are very helpful. Such lights are automatically switched on after a predefined time. Normally, it is feasible to program these lights to switch ON or OFF at any particular time. However, if the house is going to be alone for a long time then a thief can see that the lights are switched on or off at the time same time every day (provided he is keeping a vigil over days). This may arise his suspicion and such a light may not be useful in such situations.

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