Photoelectric sensor; Wireless RF interconnect; Reduces nuisance alarms; Eco-friendly; Uses electrochemical carbon monoxide sensor; Easy-to-use mute button; EZ-access battery door; Voice location announces where fire or CO is located; Includes 2 AA batteries; This product is intended for non-professional, DIY installation. If information is needed about a professionally installed & monitored system, please contact First Alert(R) Professional at 1-800-921-6025. First Alert(R) Professional is not affiliated with BRK Brands, Inc.;