Optipath 360 photoelectric smoke design. Visual and audible alarm signals - 177 Candela strobe and 1 Hz flash rate meets ADA, ANSI 117.1, NFPA 22 and UL1971 requirements for visual signaling devices. Smart strobe - distinguishes and warns between smoke/heat or CO dangers. Two latching features - two silence features. Two AA battery back-up (Note: will not power strobe). 10 year warranty.