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Alert System Type
Smoke / Fire / Carbon Monoxide
Sensor Type
Smoke / Heat
Audible Indicator
Battery Backup
Ease of Installation
Intermediate (Installs < 60 minutes)
First Alert
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Build a Safety network of Interconnected Alarms in Your Home Without the Cost and Hassle of Wiring
First Alert SA521CN-3ST Onelink Integrated Wireless Smoke Alarm
First Alert SA521CN-3ST Onelink Integrated Wireless Smoke Alarm
First Alert SA521CN-3ST Onelink Integrated Wireless Smoke Alarm
Item# 79861
Price: Normally $75.99 
Hot Deal $50.60
Free shipping on orders over $175 - See Details


  • Wireless integration with other alarms in your home
  • Photoelectric smoke sensing alarm with mute button
  • Eco-friendly
  • Easy access battery door
  • Optional theft-prevention lock to protect alarms
  • Loud 85db alarm

Essential Info

The First Alert SA521CN-3ST Onelink Integrated Wireless Smoke Alarm links the alarms throughout your home. This 120VAC hardwired wireless detector with battery backup integrates single alarms into a system. Expand protection by replacing one existing hardwired alarm with Onelink and linking to existing hardwired and battery operated alarms. By adding Onelink battery powered alarms elsewhere, when one alarm sounds, all alarms will be notified. Easily link alarms with the press of a button. 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.

Works with the INSTEON Smoke Bridge
The First Alert ONELINK Smoke detectors can be linked to the INSTEON Smoke Bridge to create email and text message alerts in case of smoke, fire or carbon monoxide using an INSTEON Hub or other central controller. It can also be linked to lights or other INSTEON devices manually or via software to turn lights on instantly in the event of an alert to make the escape faster, easier and safer.


What's Included

  • Wireless Smoke Alarm
  • 2AA Batteries
  • Specifications

  • Sensor: Photoelectric
  • Warranty Claim: 10-Year Limited
  • Color: white
  • Battery backup: AA
  • Product Dimensions (L x W x H): 8.3 (inches) x 7.18 (inches) x 10.0 (inches)
  • Reviews

    8 Ratings
    5 star: 88%  (7)
    4 star: 0%  (0)
    3 star: 0%  (0)
    2 star: 0%  (0)
    1 star: 12%  (1)
    Average Customer Rating
    (8 customer ratings)
    Share your thoughts with other customers
    JOHN -- dallas, TX   4/13/2014
    I replace two old hard-wired detectors and have been pleased with how these work with the ISY.
    JOHN -- dallas, TX   4/13/2014
    Easy install. Works well. The two detectors communicate with each other and with the ISY.
    JASON -- daytona beach, FL   5/31/2013
    Love it! SUPER EASY to set up and install. Linked to smoke bridge right away. Great product!
    KEVIN -- clearfield, UT   3/14/2013
    WOW, along with the Insteon smoke link bridge I can now monitor my home away from home for smoke, too cool. It also linked with my older smoke detectors (hardwired) though out the house.

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