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An Overview of Fire Alarm Systems

Fire alarm systems are essential for the adequate detection and warning of a fire situation within commercial and residential premises. The detection, visual and audible requirements of a fire alarm system are dependent on the layout and use of the building. It is due to the diversity of these applications that fire alarm panels and related accessories have been developed to meet these varying needs.

Who specifies the system required?

According to the Regulatory Reform (Fire Safety) Order 2006, businesses and organisations must have a fire risk assessment carried out by a competent person. The competent person can be someone from within the organisation, or, many choose to nominate a third party Fire Risk Assessor; ensuring they are fully qualified and have read and understand the current legislation. The fire risk assessment is to be completed on-site and a report of the recommendations is to be documented.

Part of the fire risk assessment includes identifying the type of fire detection system required and the relevant British Standard to conform to. According to legislation, for commercial businesses, organisations and HMOs (over 2 storeys), it is likely you would need to comply with BS 5839-1: 2017.

BS 5839-1: 2017 - a system ranging from those comprising of one or two manual call points and sounders to complex networked systems with numerous automatic fire detectors, manual call points and sounders, connected to control and indication panels.

Types of Fire Alarm Panel

There are three main types of fire alarm panel available. The information below briefly describes each panel and the differences between the three:

Conventional (Four Wire)

  • The oldest of the three types of panel available on the market.
  • Traditionally installed in all types and size of premises, conventional fire alarm panels are now used less often for larger buildings - the later developed two wire or addressable fire alarm panel may be more suited
  • Splits the fire alarm system into "zones" - 2, 4 and 8 zone panels available
  • Typically supports up to 32 devices on each zone
  • Suitable for smaller applications where the number of required fire alarm devices is low
  • Cheapest of the three fire alarm panels to purchase; however the installation costs are higher
  • Sounders and beacons are installed on a separate circuit to the detectors and manual call points
  • Identifies which zone of the fire alarm system has been activated
  • Typical applications: small schools, restaurants, sports and community halls

Two Wire

  • Later developed version of the traditional conventional fire alarm panel
  • Suitable for small to medium sized premises
  • Splits the fire alarm system into "zones" - 2, 4 and 8 zone panels available
  • Typically supports up to 32 devices on each zone
  • More expensive to purchase but cheaper and quicker to install
  • Allows sounders and beacons to be connected to the same circuit as the detectors and manual call points
  • Identifies which zone of the fire alarm system has been activated
  • Typical applications: small office premises, restaurants, small HMOs


  • Most advanced fire alarm panel available
  • "Cause and effect" feature - offers greater flexibility for detection, activation and audible and visual warning
  • Ideal for more complex or high risk applications
  • Devices are connected using a "loop" system - multiple loops panels available
  • Typically supports up to 126 devices per loop - detectors, call points, sounders and beacons
  • Each device is given an individual "address"
  • Identifies the exact device that has been activated - saves time for the "appointed person" and the fire services in the event of an emergency
  • Typical applications: hospitals, hotels, large office premises, shopping centres

Wiring Diagrams

The panel is the "hub" of the fire alarm system. This is where the system can be programmed according to the users' requirements, monitors device operation, indicates if there is a problem and identifies where the fire alarm system has been activated

Conventional (Four Wire)

Sounders and beacons are installed on a separate circuit to the detectors and manual call points

Two Wire

Detectors, manual call points, beacons and sounders can be installed on the same pair of supply wires - no need for separate sounder circuits


Detectors, manual call points, beacons and sounders are connected using a loop system - the loop can be split into zones

Key terms


At the planning stage, a premise may be divided into different sections, allowing the fire alarm system to become more manageable. These divided sections are called zones. Zones are particularly important for conventional fire alarm systems, as this enables the panel to identify where the system has been activated.


Addressable fire alarm panels have one or more loops used to connect devices to the panel. The single wire connection leaves and returns to the panel in a complete loop.


Available in smoke, heat, carbon monoxide (CO) and multi-sensor configurations acting as the sensors for the fire alarm system. Detectors do not have built in sounders and they require a base in order to be recognised by the fire alarm panel.

Manual Call Points

Typically located within the exit routes of the building. The device allows the fire alarm system to be activated manually, should a fire be identified before a fire detector has been triggered.


Provides visual indication that the fire alarm system has been activated. Beacons are not required for all areas of the premise; however they enable compliance with the Disability Discrimination Act.


Provides audible warning that the fire alarm system has been activated. These are available as standalone devices or built into the detector base. These can be installed in areas where a detector may not be required.

Repeater Panels

Multiple repeater panels can be installed as part of the fire alarm system. These allow the indicators and functions of the main fire alarm panel to be accessed from different areas of the premise.


Relays allow connection to external devices.


Isolators are required at intervals on the fire alarm system. In the event of a short circuit, isolators ensure that only the section between the isolators will be affected. When the short circuit is removed, the isolators will automatically restore power to the system.

Cause and Effect

Related to addressable fire alarm systems, cause and effect refers to the programming of a fire alarm system, where the output or result of an input activation can be changed according to the requirements of the application e.g. double-knock.


The fire alarm system is programmed to identify and only go into full alarm mode when two devices from different zones or the same zone are activated.

Phased Evacuation

A fire alarm panel can be configured to activate sounders in different parts of a building to alarm in a staged (or phased) sequence. The sounders in rooms where a fire is detected are set to alarm first.


(doc:529 V1.0). Our articles are reviewed regularly. However, any changes made to standards or legislation following the review date will not have been considered. Please note that we provide abridged, easy-to-understand guidance. To make detailed decisions about your fire safety provisions, you might require further advice or need to consult the full standards and legislation.


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