The Kidde Hardwire Smoke Alarm with Smart Hush™ Alarm Silencer is a 120V AC, wire-in smoke alarm that can function as a stand alone unit or interconnect with up to 24 Kidde devices (of which 18 can be initiating). This smoke alarm uses ionization sensing technology Ionization sensing alarms may detect invisible fire particles (associated with fast flaming fires) sooner than photoelectric alarms. Photoelectric sensing alarms may detect visible fire particles (associated with slow smouldering fires) sooner than ionization alarms. Leading authorities recommend that both ionization and photoelectric smoke alarms be installed to help ensure maximum detection of the various types of fires that can occur within the home. Features and Benefits: • Ionization Technology – May detect invisible fireparticles (associated with flaming fires) sooner than photoelectric alarms. • 120V Interconnectable – Will interconnect with up to 24 other devices (18 of which can be initiating), including smoke alarms (limit of 12), CO and heat alarms. • Multi-function One Button Design includes: • Hush® Feature – Temporarily silences nuisance alarms for approximately 8 minutes (smoke must be present before Hush® is activated). • Test Feature – Simultaneously tests the unit’s electronics and verifies alarm operation. • Tamper Resist Feature – Tamper resist locking pin deters from tampering or theft.