First Alert SA521CN-3ST

Wireless Interconnect Hardwired Smoke Alarm

  • Factory New
Brand: First Alert Part #: 17000 Category: Manufacturer Part #: SA521CN-3STSecondary Part #: 1039830


First Alert Wireless Interconnect photoelectric smoke alarms link the alarms throughout your home. 120 V AC hardwired wireless detectors with battery backup integrate single alarms into a system. Expand protection by replacing one existing hardwired alarm with Wireless Interconnect and linking to existing hardwired and battery operated alarms. By adding Wireless Interconnect battery operated alarms elsewhere, when one alarm sounds, all alarms will be notified. Photoelectric smoke sensor reduces nuisance alarms. Easy access battery drawer: no need to remove an alarm from the ceiling to change battery. Includes 10-year limited warranty. Meets UL standards.


Weight 1.00 lbs
Dimensions 5 × 5 in

First Alert

Production Status



  • Hardwired alarm can communicate wirelessly with other compatible alarms to create a fire alarm system (additional alarms sold separately)
  • When one alarm is triggered, all connected alarms will sound
  • Integrated battery backup allows continuous detection during power outages
  • Photoelectric sensor detects smoke with reduced false alarms
  • One button silences a false alarm and tests the smoke detector
  • Eco-friendly, completely recyclable as an electronic device
  • EZ access battery door, no need to remove alarm from ceiling to change battery
  • Loud 85db alarm


First Alert – Data Sheet