Fire Alarm System (FAS)

An automatic fire alarm system is designed to detect the unwanted presence of fire by monitoring environmental changes associated with combustion. In general, a fire alarm system is either classified as automatic, manually activated, or both. Automatic fire alarm systems can be used to notify people to evacuate in the event of a fire or other emergency, to summon emergency forces aid, and to prepare the structure and associated systems to control the spread of fire and smoke

Before we tackle how a fire alarm system works, let us first review what a fire alarm system is. A fire alarm system is an active fire protection system that controls all the fire alarm modules in a building. The phrase active fire protection refers to items or systems that can be activated mechanically or electronically.

Fire alarm systems are composed of alarm initiating devices (smoke detectors and heat sensors), alarm notification appliances (sirens or devices that produce loud noises), fire control units (sprinkler systems or fire extinguisher systems), power supplies and wirings.

Fire alarm systems notify the occupants of a building or a house of a possible fire so that the occupants can either evacuate for safety or extinguish the fire before it could spread out and become uncontrollable.

Fire Alarm System

  • Conventional fire alarm system
  • Addressable fire Alarm System
  • Hybrid fire detection systems

Fire Alarm System

The fire alarm system can be set off automatically by smoke detectors, heat detectors or manually. These sensors are set to detect certain levels of heat or smoke that could be an indication of fire. A loud bell or a siren, sometimes accompanied by blinking or flashing lights for individuals who have hearing problems, blasts to alert occupants in the building. To truly understand how a fire alarm system works, let us go further into the components of the fire alarm system. In a fire alarm system there is always a smoke detector to detect smoke or fire.

Another aspect of how a fire alarm system works is the heat sensor or also called thermal sensor. A fire alarm system works by way of heat sensor in quite simple way. The heat sensor monitors the temperature in a room and any abrupt rise or sudden extreme change in temperature triggers the fire alarm.

How does a fire alarm system work by way of smoke sensor? There are two types of smoke detectors.

These are the optical detector and the ionization detector. The optical smoke detector detects smoke by using light sensors (infrared LED). When smoke particles pass through the chamber of the optical detector, it scatters light that triggers the alarm. In the ionization detector, if the smoke particle enters the chamber of the ionization detector it will reduce air ionization inside the chamber of the ionization detector and triggers the alarm.

Conventional Fire Alarm Systems

Fire Alarm Systems fall broadly in to two groups - Conventional Systems or Analogue Addressable Systems.

'Conventional' Fire Alarm Systems, in their various forms, have been around for many years and have changed little in that time in terms of technology although design and reliability have improved significantly. However, Conventional Systems are a well-proven technology protecting many hundreds of thousands of properties worldwide. A Conventional Fire Alarm System is often the natural choice for smaller systems or where budget constraints exist.

In a typical Conventional Fire Alarm System the 'intelligence' of the system resides solely within the Fire Alarm Control Panel which receives a trigger signal from a Conventional Detector or Call Point and in turn, signals the condition to other devices such as alarm sounders and remote signalling equipment.

Conventional detectors are normally connected to the Fire Control Panel via dedicated circuits, each circuit protecting a designated 'Zone' or 'Area' of the building (the maximum size of which will often be governed by local standards). Detectors have two states, Normal healthy and Alarm.

Addressable Fire Alarm System:

Addressable fire alarm systems offer benefits in speed of detection, identification of the location of a fire and easier maintenance. Addressable fire alarm systems also offer tolerance to faults in the system wiring, which allows a single pair of wires to be used to connect up to 200 devices to the system, allowing cost savings in the wiring of large systems. In larger installations, the benefits of improved maintenance and reduced cabling cost are overwhelming. The price difference between Addressable systems and conventional systems has narrowed to such an extent that even for small installations, the use of an Addressable fire alarm system should be considered.

Main Functional Features of Fire Alarm System:

  • Detecting a fire at an early stage
  • Alerting and evacuating occupants
  • Notifying the relevant personnel
  • activating auxiliary functions e.g. smoke controls, lift homing etc
  • identifying and guiding fire fighters
  • Blocking Diodes for reverse current flow protection
  • Easy DC-termination
  • Easy and decent Cable management
  • Time effective as well as money effective for cabling
  • Step by step trouble shooting methodology
  • Contemporary DC combining and disconnecting
  • Space saving and orientation flexibility
  • Load-break rated disconnecting
  • Increased granularity
  • Traditional DC combining
  • Reliable electric safety to avoid hazard
  • Online Monitoring* (Optional for DCDB/ACDB)

GEESYS Fire Alarm System


TYPE OF SYSTEM Fire Detection & Alarm System
NO. OF ZONES  PROVIDED 1 to 200 zones
  • Ionisation type smoke detectors
  • Photoelectric smoke detectors
  • Fixed temperature cum rate of raise in temperature detectors
  • Open circuit in detector cabling for each zone. Short circuit in detector cabling for each zone. 
  • AC failure.
  • Battery low. (adjustable from 22 V to 23 V)
FIRE Two flashing red LEDs in the zone under Tire
FAULT  Two steady glowing yellow LEDs in the corresponding zone.
CHARGER ON  One separate yellow LED for 'Charger 0, indication.
SYSTEM ON  One separate green LED for 'System 0, indication.
AC & DC FUSE BLOWN INDICATOR  Separate red color LED for AC & DC 'Fuse Blow, indication.

Fire:A beep sound in the panel.

Fault: A continuous tone in the panel.

After alarm cancellation Hooter sound changes to a low continuous tone & when another zone enunciates fire again, the main Hooter gets activated. Audio alarm can be silenced by ALARM CANCEL button.

Applications :

  • Computer suites, EDP facilities and telecommunications hardware
  • Control rooms such as railway signalling centres and air traffic management centres
  • Stores and archives
  • Heritage sites such as art galleries and museums
  • Medical and laboratory equipment
  • Petrochemical plant, offshore oil and gas installations, pipeline pumping stations
  • Ship machinery spaces, rail locomotives and rolling stock