The Kidde PI2010 is a 120VAC, wire-in smoke alarm with 9V battery backup. This smoke alarm functions as a stand alone unit or in an interconnected system. The Kidde PI2010 features Hush®, allowing you to quickly silence nuisance alarms and also includes a tamper resist features that deters tampering and theft. The PI2010 includes a quick connect power harness that allows for quick and easy installation. This smoke alarm combines both photoelectric and ionization sensors. Ionization sensing alarms may detect invisible fire particles (associated with flaming fires) sooner than photoelectric alarms. Photoelectric sensing alarms may detect visible particles (associated with smoldering fires) sooner than ionization alarms. Kidde strongly recommends that both ionization and photoelectric smoke alarms be installed to help insure maximum detection of the various types of fire that can occur within the home. The Kidde PI2010, 120VAC, wire-in smoke alarm with 9V battery back up provides continuous protection against smoke and fire hazards, even during power outages. The Kidde PI2010 interconnects with up to 24 Kidde devices of which 18 can be initiating. This unit also includes flashing LEDs to signal the alarm is functioning properly, a low battery warning and a loud 85dB alarm. The Kidde PI2010 is UL Listed and includes a 10-year limited warranty.