Universal Security Instruments CD-9590 3-LED Plug-in Carbon Monoxide Alarm with Battery Backup/Drawer,Universal Security Instruments,CD-9590" /> Includes a 9-Volt super heavy duty battery to power the alarm in the event of an AC power failure The unit contains front-load battery drawer for easy access when it is time to replace the battery The 120-Volt AC direct plug in alarm is fast and easy to install Test buttons for alarm and power No costly sensor replacement. 3LED's: alarm power and service alarm condition indicators