The Kidde Smoke Detector, Hardwired Smoke Alarm with Battery Backup & Interconnect Capability, model i12040A, is an AC/DC powered, ionization smoke detector that is hardwired into a home's 120V power and includes a 9V battery backup. This smoke alarm uses ionization sensing technology, which may detect invisible fire particles (associated with flaming fires) sooner than photoelectric alarms. Kidde strongly recommends that both ionization and photoelectric smoke alarms be installed to help ensure maximum detection of the various types of fire that can occur within the home. Designed to be mounted easily, the smoke detector has a large mounting base, pre-stripped wiring harness with easy-off cap, and a front battery pull tab so you can activate the battery without removing the alarm from the mounting bracket.Red and green LEDs on the smoke detector indicate the alarm's status, with green indicating the unit has AC power. The red LED indicates the alarm condition, including standby, alarm, memory, or Hush mode. This hardwired smoke alarm is also available in 2-pack, as well as a 6-piece bulk pack for contractors and property owners. The unit is a UL Listed product with a 10-year limited warranty.A maximum of 24 Kidde devices can be interconnected in a multiple station arrangement, but cannot exceed the NFPA (National Fire Protection Association) limit of 18 initiation devices, of which 12 can be smoke alarms. With 18 initiating devices (smoke, heat, CO, etc.), interconnected, it is still possible to interconnect 6 strobe lights and or relay modules. Meets requirements of UL217, NFPA72, The State of California Fire Marshal, NFPA 101 (One and two family dwellings), Federal Housing Authority (FHA), and Housing and Urban Development (HUD).