The 420 Series Automatic Fire Detectors offer a superb accuracy as well as detection speed and precision. The versions with dual-optical sensor (DO-detectors: FAP-DO420, FAP-DOT420, FAP-DOTC420) are able to detect lightest smoke (TF1 and TF9). These detectors provide all advantages of LSN improved version. The addressing of the detectors can be configured with the integrated turning switches.