Easy Installation - simply plug-in to a standard, 120V outlet in your home 9-volt battery backup provides protection during a power outage Digital LED display shows the level of carbon monoxide the CO alarm is sensing 85-decibel alarm announces when carbon monoxide is detected Peak Level Memory records the last time carbon monoxide was detected or when the unit was last tested Test-Hush Button makes testing the detector or silencing false alarms easy Extension cord (included) allows for placement on a table or shelf UL listed with a 10-Year limited manufacturer warranty on the alarm only (not a battery performance claim). Warranty begins when the alarm is powered on. If that date is unknown, it should be assumed that replacement is needed.