1. The Brain:

Fire Alarm Control Panel (FACP) The system’s brain and power supply: this device receives signals from the activating devices, processing them, sending them to notification devices and automatically initiating any response systems installed. It receives its primary power source from the AC power, but it also has a battery backup system capable of sustaining operation for at least 24 hours if the mains power fails.

2. The Triggers:

Initiating Devices These input devices indicate to the Fire Alarm Control Panel that a fire has been detected and should raise the alarm:

• Photoelectric Smoke Detectors-sense larger particles emitted by slow, smoldering fires.
• Ionisation Smoke Detectors-use tiny amounts of radioactive material to detect rapidly burning fires
• Heat Detectors-react to fixed high temperatures or rapid temperature rises.
• Manual Call Points/Pull Stations-used to activate the alarm quickly and efficiently, lever operated or "break-glass" units situated next to exits.
• Sprinkler Flow Switches-activated by the flow of water through the sprinkler pipes, signaling the panel that the sprinkler heads have been activated.

3. The Alerts:

Notification Appliances
These devices sound the alarm to alert people in the building to take action and allow them to escape:

• Audible-horns, bells, sirens or voice evacuation speakers-must be loud enough to reach every area within the building.
• Visual-strobes- used in addition to audible notification devices for those who are deaf, and also to draw attention to alarms, in case of poor visibility from smoke.

4. The Response:

Safety Interfaces Modern FACP systems have the capability of interfacing with safety systems to provide more than simply an audible alarm. For instance, magnetic door holders can be released to allow doors to close and contain smoke, the HVAC can be turned off to help control the movement of fire and smoke around the building and the elevators can be recalled to ground level.