Fire alarm systems can be broadly divided into three types -
Those that use audible warning systems, those that use visual
warning systems, and finally, those that use both. Those audio
types are defined by the type of audio mechanism they use. For
example, some use bells and gongs to sound out their warning.
The larger the gong (average being 6 inches wide), the stronger
the noise emitted. Most home fire alarm gongs are only 4 inches
wide, so as not to go off too loudly.
Bells and gongs are gradually being replaced by newer electronic sound devices that require less power to operate and provide a lot more configuration options. One of the benefits of such newer electronic sound devices is they can be mounted upside down or in any position and they will still work without any hitches. They can be pre-configured to sound out someone's pre-recorded voice, or a beep, or a tone.
The other warning system for fire alarm systems is the visual one, which takes the form of beacon lighting. There are several types of such beacons; some are rotating lights, xenon lights, while others are LED lights. Rotating lights are not used very often but LED beacons are, mainly because they use up relatively little power but yet are able to shine intensely. Xenon beacons that flash on and off are the ones most commonly used by most fire alarm systems. Some models come in different colored filters which colors the lighting output so as to appear more conspicuous.
The best warning systems combine both sound and visual modes so as to maximize the warning efficacy, and give the occupants of the building enough time to react to any fire breakouts, call the fire brigade, and scramble from the premises. If your budget allows it, opt for fire alarm systems with a combination of audio and visual early warning devices.