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. 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. 120V AC with battery back up (2 "AA") included. 5 year warranty. Vermont and Oregon approved.