What is an intruder alarm system?
Intruder/burglar alarm system is a set of interconnected devices that is aimed to protect an object, usually a facility, against intruders and to notify the owner or/and the monitoring station/center of any violation of the protected zones. Depending on the requirements and financial possibilities, it can be a simple alarm system suitable for a basic protection of a home/apartment, or a more advanced structure, which in addition to the basic functions will greatly improve the life comforts of the users. The designer of the system, usually the installation company or simply the installer, can greatly help the investor/user (customer) to choose an optimal solution, depending on the characteristics of the facility and the customer needs, also taking into account expansion options for the future. More advanced alarm systems can perform functions like access control (motorized gates, electric strikes in wickets/doors), lighting and heating control, and many other tasks of home/building automation. The interface devices (manipulators) are modern keypads and touch panels, which beyond the aesthetic appearance and intuitive operation have the ability to store maps of the facility on memory cards for easier control of the entire system, as well as (optionally) mobile phones or handhelds and PCs with dedicated applications and Internet connection.
Elements of alarm systems
Alarm control unit/panel (switchboard). The main unit is mounted in a dedicated housing/box together with a backup/buffer battery guarantying operation of the system during power outages. The housing is equipped with an anti-tamper switch connected to the dedicated input of the panel. If the system is not put in the service mode, any attempt to open the case ends up triggering an alarm. The control panel monitors the proper operation of all the equipment installed in the system. It collects information from the sensors, keypads, anti-tamper circuits, detects any faults in the wiring, and in the event of an irregularity, switches on optical and acoustic signaling. If the control panel is equipped with a communication module, it can notify the user or a security company about the alarm action. Any interference into the system will not go unnoticed, being stored the memory of the unit. During the selection of an intruder alarm control panel, one should pay particular attention to the number of inputs, outputs (high and low current), and system expandability options (if ever needed in the future).
Keypads, touch panels. These manipulators allow the installer to setup the control panel and program all the functions of the alarm system. They also are the user interface for communication with the alarm system, which provides information on the system status and enables arming and disarming operations. An alarm system usually contains one main (master) keypad and (if needed) zone/partition manipulators. The master device has LCD display and numeric keys, or touch screen. The partition keypads have numeric keypads and a simple optical signaling in the form of LEDs. They are used to arm and disarm the partitions, while the main keypad is responsible for the complete control of the entire alarm. The daily handling of the alarm system is limited to arming and disarming operations with the use of the appropriate codes, and viewing/reseting the alarm history.
Sensors. Sensors/detectors are the most essential elements of any alarm system. The proper selection, deployment and operation of sensors determines the actual usability of the entire system. The popularly employed sensors are PIR and PIR+MW motion detectors and reed switch sensors mounted on the door/window frames. These and other sensors used in alarm systems can be classified as follows:
motion detectors:
Passive Infra Red (PIR) sensors
Micro-Wave (MW) sensors
dual sensors (PIR+MW)
peripheral sensors (reed switches)
other sensors: glass break, vibration, water, carbon monoxide, gas, smoke, infrared barriers (curtain detectors)
Wireless controllers. The controllers enable the expansion of the system with additional wireless devices, e.g. detectors. They are connected to the control panel via the system bus. The programming is done via the control panel, using a keypad or computer running a dedicated software. Battery-operated wireless sensors can work approx. 2 years without battery exchange. The battery life depends on the transmission power and on how many times the transmission takes place. Wireless subsystems are ideal for use in each case where any additional wiring is unacceptable, e.g. due to aesthetic reasons. The installation is very fast and the maintenance is limited to periodical replacement of the batteries in the wireless detectors.
