https://www.asmag.com/project/resource/index.aspx?aid=16&t=secutech-made-in-taiwan-products-and-solutions
Product Info
521B Smoke Detector

521B Smoke Detector

Digital Monitoring Products, Inc.
Region: United States of America
Update: 05/25/2007
Key Specifications
Two-wire photoelectric smoke detector with CleanMe. Monitors sensitivity and operational status and provides visual and remote trouble status if out of sensitivity range or fails internal diagnostics.
https://www.asmag.com/project/resource/index.aspx?aid=16&t=secutech-made-in-taiwan-products-and-solutions