First Alert BRK SL177 Hearing-Impaired, ADA-Compliant Smart Strobe Light, 120V AC Smart strobe flash patterns help alert hearing impaired individuals to danger from smoke and carbon monoxide Must be used in combination with 120V AC smoke, heat or carbon monoxide alarms (sold separately) Powerful 177 candela xenon strobe light provides effective visual warning Separate "smart" flash patterns distinguish between smoke and carbon monoxide Backed by a 10 Year Limited Warranty and meets Underwriters Laboratories (UL) UL 1971 safety standard