The GN-503 (120VAC/9VDC) Series of combination photoelectric smoke and electrochemical sensor carbon monoxide alarms are for use as evacuation devices in all dwelling units, including but not limited to homes, apartments, hospitals, hotels, motels and other commercial occupancies. The GN-503 Series is listed in compliance with ANSI/ UL 217, ANSI/UL 2034, for installation per NFPA 720 and NFPA 72. Available in three models, the GN-503 Series is engineered to virtually eliminate nuisance alarms and deliver outstanding performance wherever reliable smoke and CO protection is required. The GN-503F features one (1) set of Form A/Form C contacts that activate for smoke and/or CO events. The GN-503FF features two (2) sets of Form A/Form C contacts that activate independently for smoke and CO events. Both the GN-503F and GN-503FF provide a connection to a protected premises alarm system to provide a supervisory/ trouble signal.