Simplex 565-925 4-Wire Duct Sensor PC Board

The Simplex 565‑925 4‑Wire Duct Sensor PC Board is a replacement printed-circuit board designed for Simplex 4098-9756 duct sensor housings used in HVAC smoke detection systems. This board interfaces with conventional 4‑wire initiating-device circuits (IDCs) to provide supervised relay outputs to control duct smoke alarms. Installed within the duct housing, it works alongside the photoelectric TrueAlarm sensor to detect airborne smoke particulates and trigger alarm responses. Built for durability and reliability, the board features LED indicators (e.g., yellow LED for relay supervision), straightforward integration into existing duct detector assemblies, and compliance with industry safety standards. Its compact design simplifies both installation and maintenance, making it ideal for commercial, industrial, and institutional fire-safety applications where dependable smoke detection in air ducts is essential.