Fire alarm devices used in fire protection systems come in two types: coded and non-coded. Coded alarms have a unique address code, allowing individual or simultaneous activation by the main unit, and the corresponding alarm can be easily located. Non-coded alarms trigger as soon as there is power and require a fire alarm input/output module to connect to the fire alarm controller. Generally, a single module can be used for unified control within the same area.
Furthermore, fire alarm devices can be classified in various ways based on different technical principles and application scenarios. According to detection principles, they can be divided into ionization, photoelectric, and semiconductor types. Photoelectric smoke detectors are based on the principle of optical scattering and are sensitive to large particles of smoke produced by smoldering fires; semiconductor smoke detectors are based on changes in the conductivity of semiconductor materials and are more sensitive to combustible gases, responding quickly to open flames; ionization detectors utilize the ionization region formed by radioactive materials to detect changes in current. According to application methods, they can be divided into stand-alone smoke detectors and networked automatic fire alarm systems. Networked systems can transmit alarm signals to a cloud data monitoring platform for remote monitoring and linkage. Based on integrated functions, alarms can be divided into single smoke detectors and "three-sensor" intelligent detectors that integrate smoke, temperature, and combustible gas detection. Based on signal transmission methods, alarm systems can be divided into wired alarm systems and wireless alarm systems (such as those based on Wi-Fi, NB-IoT, and other wireless networks).
