Combination carbon monoxide/smoke alarm. Features programmable voice that will alert the location of the unit and the danger detected. Photoelectric smoke sensing gives optimum protection for smoldering fires and reduces false alarms caused by cooking， or showers and steam. Electrochemical carbon monoxide sensor for accurate monitoring of carbon monoxide levels. Variable horn frequency makes it easier for the elderly with age related hearing loss to hear the horn. Provides hazard location information (such as smoke in the kitchen) for blind or visually impaired. 2 silence features: Low battery silence for up to 8 hours or temporarily silence for an unwanted nuisance alarm. 2 latching features: Alarm latch remembers which unit initiated the alarm and the low battery latch. End of life signal. 120V AC with battery back up. (2) AA batteries included. Battery life varies according to use and application. 7-year warranty. Vermont and Oregon approved.