Fire Alarm

Fire alarm refers to the device used in automatic fire alarm system to issue fire alarm signals different from ambient sound and light. Called fire alarms, fire alarms are the most basic fire alarms, usually combined with fire alarm controller sends out fire alarm signals to the alarm area through sound, light and sound, warning people to evacuate safely and take fire-fighting and disaster-relief measures.

English name – Fire alarm
Signal – Send out a fire signal that is different from ambient sound and light
Warning – Take safe evacuation, fire fighting and disaster relief measures
Classification – Fire Sound Alarm, Fire Light Alarm
Main Components – Bell, Hammer, Drive

Basic Information

Fire alarm is the most basic fire alarm signal notification device. It usually sends out a fire alarm signal to the alarm area in the form of sound and light, warning people to take measures such as safe evacuation, fire fighting and rescue. The early fire alarm was just a fire alarm with a simple sounding method, which usually used a motor-driven transmission to drive a hammer to strike the metal at a certain frequency. Bell Jar, an alarm bell that emits a high-decibel alarm signal. Later, an alarm bell appeared, which used an electromagnet to drive the sound. With the development of electronic technology, fire alarms using buzzers, speakers and other sounding devices have appeared one after another.

Fire alarms have evolved from flashing fire alarms using a constant light source through periodic shading to using flash tubes, pixel tubes or flash tube, pixel tube or LED, the fire alarm is controlled by circuit for its power supply frequency and other flashing Way. With the diversification of the implementation of the alarm, there have been a new type of fire acousto-optic alarm that integrates the fire sound and light alarm signal and a fire alarm that uses a display. Abroad, sound and/or light alarm devices and fire detectors, Manual fire alarm button all-in-one product.

Classification and Performance Requirements


Fire alarms can be divided into the following categories:
①According to the form of alarm signal, it can be divided into fire sound alarm (including alarm bell), fire light alarm and fire sound and light alarm.
②According to the power supply mode, it can be divided into AC power supply alarm and DC power supply alarm.

Performance Requirements

Different types and working principles of fire alarms have different performance requirements. The main performance parameters of a fire sound alarm are the sound pressure level and tone period of its sound signal. The main performance parameters of a fire alarm are its basic flash frequency, visual distance and light signal clarity. According to the requirements of my country’s current public umbrella industry standard GA 385-2002 ((fire sound and light alarm), the sound signal issued by the fire sound alarm is required to measure the sound pressure level (A-weighted) at a horizontal distance of 3m. Within the range of 115dB. The fire alarm using tone requires that its tone change period should be within the range of 0.2 ~ 0.2dB. 5s. The requirement for the optical signal is that its basic flicker frequency should be within the range of 20-180 times/min; Under the ambient light of 500lx, it should be clearly visible at a distance of 25m. The alarm that uses the display to send out a fire alarm signal should be able to operate through automatic and manual operation, clearly and steadily display the light fire alarm signal, and keep it until manual reset.

Composition and Working Principles

The alarm bell is one of the most primitive and simple fire alarms. The main components of a bell are the bell jar, hammer, driving device and transmission device. The bell jar Usually cast aluminum or cast iron, the hammer will make a sound when hitting the bell. The driving device is generally a motor or an electromagnet, which is driven by the motor. The common transmission device is gear transmission or cam rocker mechanism, and there are also transmission methods that use electromagnets to directly attract the armature.

Other fire sound and light alarms are generally composed of a casing, a sounding device and/or a lighting device, a power supply and a control circuit. Commonly used sound-emitting devices are generally buzzers or speakers, and light-emitting devices include flash tubes, pixel tubes and light-emitting diodes. The main function of the control circuit is to control the frequency and voltage of the power supply of the acousto-optic transmitter. Addressable fire audible and/or optical alarms are also provided with address coding sections.

In practical engineering applications, the fire sound and light alarm installed in the fire compartment is controlled by the fire alarm controller connected to it or the fire link controller to start automatically or manually. When a fire occurs in the fire compartment, after receiving the start signal, the fire sound and light alarm will send out a fire sound and light alarm signal different from the ambient sound and light according to the specified sequence.

Engineering Applications

Fire alarms are suitable for various places where fire alarm notification and indication are required. For places without fire emergency broadcasting equipment, fire sound and light alarms are mandatory on-site alarm devices. When installing fire emergency broadcasting equipment on site, it is not necessary to install fire alarms so as not to interfere with voice broadcasting. Under normal circumstances, the setting requirements of fire alarms are that at least one fire alarm should be installed in each fire compartment, and it should be installed at the entrance and exit. Fire alarms should be activated manually or automatically. When the fire alarm is installed in a location where the ambient noise is greater than 60 decibels, the siren sound pressure level should be 15 higher than the background noise decibel.

When the AC power supply alarm is connected to the fire alarm controller, it is generally necessary to connect the control switching module; Connect the alarm output module.

DC powered sirens can usually be powered by a fire alarm controller (DC24 V). This alarm with built-in addressing interface circuit is used in bus system systems and can be connected directly to the bus detection loop. Such alarms without an internal addressing interface circuit can usually be controlled by the alarm control line of the fire alarm controller; when connected to the bus loop of the fire alarm controller, an alarm output module needs to be connected.

In use, the fire sound and light alarm components should be checked regularly. At the same time, according to the maintenance requirements of the product, it is removed from the installation location, and dust removal maintenance is carried out regularly to ensure its normal operation.