Ensuring the home is a haven
Personal security is one of the big issues confronting society in this age of high crime rates. With the ever-increasing levels of house break-ins and home invasions, the installation of an effective intruder detection system, incorporating fire, duress and medical alarm facilities is becoming a necessity.
Home alarm systems consist of three main elements: detection sensors, a control panel and the alarm warning device.
Sensors: most sensors used these days are passive infra-red sensors. When installed correctly, they are normally extremely stable and nuisance alarm free. The sensor operates by detecting changes in the levels of a narrow band of infra-red energy in its area of view. All objects in the area transmit infra-red energy. When a person moves into the area, their body heat changes the levels of infra-red; this change is what the sensor detects. Infra-red sensors should be installed in areas where possessions of financial or sentimental value are kept, for example the lounge room and master bedroom. A sensor can cover an area of up to 15m x 15. At additional cost, pet tolerant sensors are also available that will ignore a pet (up to 38kg and 0.75m high) in the area, but still detect a walking intruder.
The system should include at least one or two smoke detectors that are installed in the living and bedroom areas of the home.
Door switches and glass break sensors can also be installed to protect the perimeter of the premises. These devices are normally used in conjunction with internal passive infra-red sensors and their main advantage is that the entire perimeter alarm can be activated while the owner is in the house. The major disadvantage is that cost of installing this type of system can be up to $3500.
Around 85 percent of systems are hardwired, with the sensors and keypads connected to the control panel by cables. An alternative method is to use wireless devices that communicate with the control panel using wireless technology. Utilising wireless systems has advantages when used in locations that would be difficult to hard wire and also in rental properties as the cost of re-installation to a new site is minimal. The disadvantage of using wireless systems is that the installation technician must have a clear understanding of installation techniques as well as the do’s and don’ts of wireless system technology.
Control panels: the alarm control is the brains of the system and continuously monitors its state. Containing the microprocessor electronics, power supply and rechargeable, standby batteries, it is normally connected to a keypad that enables authorised people to arm and disarm the system. Today’s modern systems are easier to operate than a microwave oven. They normally have three operating modes: away armed, at home armed and disarmed.
The system will typically provide single touch buttons to arm it and a four digit code is entered into the keypad to disarm it. In the home arm mode of operation, all of the areas that the occupants will be moving in are automatically isolated from the system, enabling them a level of protection while they are in the home. Indicator lights on the keypad show the system’s operating mode as well as system information. The control panel is normally installed in a discrete location such as a wardrobe and the keypad is mounted in a convenient location such as near the entrance door. At additional cost, convenient remote control “key ring” style wireless transmitters can be used to arm and disarm the system.
Warming devices: there are three methods of generating a warning that the alarm system has activated. These are: a local sounding system that triggers internal and external sirens, a monitored system that will transmit a signal down the normal telephone line to a central monitoring station and a self-monitored system that will transmit a signal down the telephone line to a telephone, pager or mobile telephone. Systems using remote monitoring may also have local warning sirens. External sirens are mounted in weather- and tamper-resistant enclosures that contain tamper switches that will activate the system if the siren cover is removed. A blue flashing strobe that latches on in the event of an alarm, and remaining on until the system is disarmed, is normally incorporated into the external siren unit.
When a monitored alarm is activated, the control panel will dial the pre-programmed telephone number of the central monitoring station. As soon as a communication link is established, the control panel will transmit digital information to the central station receiver describing the premises’ location and the area that has triggered the alarm. Information is then displayed on a computer terminal showing the name and address of the premises, a description of the zone in alarm, relevant emergency telephone numbers and the actions required to respond to the event. Examples of the response could be to call a relative, call the fire brigade or send an armed guard.
A chime function can also be provided. This function is enabled in the disarmed operating mode and will momentarily “beep” the keypad or a buzzer if a particular zone on the system is opened. The zone could include front and back doors, swimming pool gate and gate to the street and provides an additional level of security to the system.
The above is an edited version of an article reproduced from Security Insider (May/June 2002 issue), published by the Australian Security Industry Association - www.asial.com.au.
1-Jul-2002