Smoke alarm with ionization technology may detect invisible fire particles (associated with flaming fires) sooner than photoelectric alarms. 120 V inter-connectable, will interconnect with up to 24 other devices (18 of which can be initiating) including smoke alarms (limit of 12), CO and heat alarms. 10-year sealed lithium battery backup, eliminates the need to replace the battery. No battery to replace for the life of the alarm (10 years). Battery backup automatically activates when the alarm is attached to mounting bracket. Multi-function one button design includes Hush® feature temporarily silences nuisance alarms for approximately 9 minutes (smoke must be present before Hush® is activated). test feature, simultaneously tests the unit's electronics and verifies alarm operation. Reset, resets the carbon monoxide alarm. Tamper resist unit will lock to mounting bracket to deter theft or tampering.