DF 501-SD conventional photoelectric smoke detectors are state-of-the-art detectors suitable for connection to conventional fire detection control and indicating equipment, or to addressable fire detection control and indicating equipment that can accept conventional type detectors1. Advanced electronics in conjunction with a photoelectric smoke sensing chamber provide early detection of smoke and high immunity against unwanted alarms. The DF 501-SD range of conventional detectors provides fire detection and alarm system designers with a Standards-compliant, economical smoke detector for life safety and property protection applications.