Siemens FDO421 S54320-F4-A1 Smoke Detector and 49 similar items

Siemens FDO421 S54320-F4-A1 Smoke Detector W/ DB-ADPT BASE UNTESTED READ PRE OWNED/ NORMAL WEAR/ UNTESTED/ WE WERE TOLD THIS WAS PULLED FROM WORKING ENVIRONMENT BUT CANNOT TEST ANY FURTHER SO WE ARE SELLING AS IS ? What this detector actually is The FDO421 is an addressable photoelectric smoke detector used in commercial fire alarm systems (not typical home standalone alarms). Uses optical (light-scattering) sensing to detect smoke particles Communicates with a fire panel (e.g., Siemens Desigo / FireFinder systems) Built-in microprocessor + algorithms to reduce false alarms Designed for office buildings, hotels, hospitals, industrial sites ?? Key features Addressable device ? each detector has its own ID on the system High stability / low false alarm rate Automatic sensitivity adjustment (drift compensation) LED status indicator for alarm troubleshooting Compatible with Siemens bases SHELF: FA-C SA