The Notifier FSP-951 is a low-profile intelligent plug-in photoelectric smoke detector engineered for performance and modern aesthetics. It is a direct replacement for the FSP-851 Series and features an enhanced optical sensing chamber designed to respond to a wide range of combustion sources in accordance with updated code standards. The detector connects to a two-wire Signaling Line Circuit (SLC) and communicates using the FlashScan protocol. Sensitivity is programmable through the control panel and continuously monitored. Rotary decimal switches allow precise address setting for accurate point identification and maintenance tracking. The FSP-951 installs onto a compatible intelligent mounting base (sold separately) and is intended for commercial fire alarm applications.