The First Alert(R) alarm is an ionization smoke sensor alarm designed to be 120 V hardwired. The alarm includes a battery backup to ensure operation in case of power failure. This unit can be interconnected with up to smoke alarms and up to 6 smoke and carbon monoxide combination alarms so all units will go into alarm if any single unit is triggered. Also equipped with a battery compartment and base locking mechanisms and a single button test/silence. This product is backed by a 10-year limited warranty.