Notification devices use ways to capture the attention of the senses, such as hearing, sight, touch or even smell, to alert people in the event of a hazardous situation like fire. The signals for evacuation of occupants are usually made of simple devices that can transmit information that hasn’t been coded or devices that transmit patterns that are predetermined, or even complete message instructions.

Electronic hooters are used in fire alarm systems to alert people in case of fire. It is usually fully solid state with an audio output that is high enough for it to be heard at a distance that is not less than 50 m. The hooters generally have a facility to adjust the output volume based on the requirements on site. The units are always located at critical areas and have a minimum audible level that is around 65 dB, or it is at least 5 dB above the level of noise in the work area as well as in the plant area. Hooters are typically connected to the detector loop with the help of an addressable control module and are powered by the control panel using the same detector loop.

The unit has a sturdy and rugged body. The system, being waterproof, it is protected from the elements and is suitable to be mounted outdoors. The hooters that are used in such environments, in the outdoors, are usually fitted with a rain canopy for protection from the harsh beams of the direct sun, and rain.

Dual tone hooters are used in fire alarm systems to distinguish between fault audible alarms and fire alarms. In the USA, fire alarm systems have signals for evacuation that are typically a standard audio frequency. They may also have visual notifications in public areas. These messages are made such that they are unique for its purpose, ensuring there is no confusion due to any other signals.

There are fire alarm systems that use emergency voice alarm communication systems (EVACS) to give voice messages that are either manual or recorded beforehand. These high-end hooters are used in hospital buildings and facilities for detention. These are large places where complete evacuation of occupants is highly challenging to accomplish.