:: Conventional System ::

:: Addressable System ::

:: Analog Addressable System ::

Introduction:
Fire detection and alarm systems are designed to provide warning of the outbreak of fire and allow appropriate fire fighting action to be taken before the situation gets out of control. As all systems are designed primarily to protect life and property, this places a great responsibility on the system providing company because each building will present a different set of problems in relation to the risk of fire and fire spread. In designing a system we particular consider the given the type of building, its construction and the purpose for which it is being used, so that in the event of a fire, the fire detection system, combined with appropriate fire
prevention procedures, will keep risk to both personnel and property to a minimum.

For any system to function reliably and provide problem free service throughout the life of the system, all of the aspects like method of installation, materials required during installation, operator training, routine maintenance procedures, and service agreement is considered in the overall system design and plan.



Conventional System ::
As defined in the code, a conventional or two-state detector is a detector that gives one of two states relating to either normal or fire alarm conditions. Conventional fire controllers provide a number of two wire circuits onto which conventional detectors and call points are connected. Similarly, separate two wire circuits are also provided for the purpose of connecting sounders (or alarm bells) to the system.

The primary function of the fire controller unit is to indicate the location of a fire as precisely as possible. To achieve this objective, detectors are grouped into zones with each zone being connected to the fire controller by a separate circuit that also has a separate indicator on the control panel.

Each detector includes an integral LED (light emitting diode) indicator that illuminates when the device is in the fire alarm condition. If an indicator on the control panel indicates a fire in a zone, the zone must be physically searched until the detector with the illuminated LED is found. 

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Addressable System ::
An addressable system, as defined in the code, is one using addressable detectors and/or call points, signals from which are individually identified at the control panel.

In an addressable system, the fire controller can provide a number of two wire circuits onto which addressable detectors and call points may be connected. The two-wire circuit should be connected to form a loop in order to provide circuit integrity. In addition to this, zone/line isolators should be used at zonal boundaries to ensure compliance with the code.

Essentially addressable detectors operate as conventional detectors as they only have two active states (normal and fire alarm) and the zoning requirements of the addressable system are the same as for a conventional system. The main departure from the conventional system is that the detector base is now addressable. As such, each base has several DIL switches or rotary switches or pr-programmed chips that allow the unique address of the base to be set. It is quite common for addressable fire controllers to accommodate up to 1,000 detectors and call points on a number of detection loops.

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Analogue Addressable Systems ::
An analogue addressable system, as defined in the code, is one, which uses analogue addressable detectors each of which give an output signal representing the value of the sensed phenomenon. The output signal may be a truly analogue signal or a digitally encoded equivalent of the sensed value. Apart from the way in which analogue addressable detectors operate, and the fire controller communication principles employed, all system design elements of addressable systems also apply to analogue addressable systems.

Conventional and two state addressable detectors can signal only two output states, that is normal and fire alarm. Consequently, with these detectors it is impossible to ever establish how close the device is from an alarm condition, or whether the localized environmental conditions (which probably contains dust and dirt) are causing deteriorating changes in the detectors sensitivity, thereby adversely affecting its performance. However, an analogue addressable system can offer a number of system performance improvements over both conventional and addressable type systems.

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