The Edwards EST SIGA-OSD is a Signature Optica Series intelligent optical smoke detector designed for use with control panels that utilize a Signature Loop controller. It incorporates multi-criteria optical sensing technology using dual optical wavelengths and multiple detection angles to differentiate nuisance particulates from true smoke conditions. Analog data collected from the sensing chamber is processed by an onboard microprocessor that applies digital filtering and preprogrammed alarm decision algorithms. The detector features environmental compensation, self-diagnostics, automatic device mapping, and non-volatile memory storage of maintenance history. The SIGA-OSD is listed to UL 268 7th Edition and CAN/ULC-S529 standards and is intended for commercial life safety applications requiring advanced nuisance rejection and long-term stability.