Powered by two lithium batteries, battery life is estimated at up to five years to reduce the inconvenience and cost of replacing batteries.  The detector continually monitors itself, providing drift compensation and visual display of over-or under-sensitivity so that corrective action can be taken and reliable operation assured.  The sophisticated electronics and replaceable optical chamber eliminates the need to send the smoke detector to the factory for recalibration.  Includes batteries.  UL pending.