Two important safety alarms in one unit / Voice alarms and voice low battery indicator / UL listed # Uses voice alarm to announce "Fire! Fire!: or "Warning! Carbon Monoxide!" warnings # Combines two important safety alarms in one unit # Single button easily tests smoke and CO sensors simultaneously # Low Battery indicator -- unit chirps once, voice announces "Low battery!" and red LED flashes # 5 year Warranty # UL listed # Power source: 3AA Batteries