Heat detector is used for discovering early stage of fire. It’s system uses termistores to carry fast and reliable fire detection. Heat detection is carried by 4-termistors temperature sensors. Fire alarm appears when temperature reach seted level or in case of it’s fast increase. Detector has built-in optical FLASH LED. This lets recognize it’s activation for a long distance. Microchip recognize type of alarm and drives it trough loop to FAS control unit. Detector works only in FAS systems. Device can be installed in addressable loop detection circuits or stub detection circuits.