The First Alert Model No. 3120B is a wire in, 120V AC 60Hz single and/or multiple station photoelectric and ionization dual sensor smoke alarm specifically designed for residential and institutional applications including sleeping rooms of hospitals, hotels, motels, dormitories and other multifamily dwellings as defined in standard NFPA 101. Model 3120B complies with UL217, CSFM, NFPA 72, HUD, FHA and other agencies that model their codes after the above agencies. It meets building codes where AC/DC photoelectric and ionization combination smoke alarms are required. The BRK 3120B is a state of the art hardwired with battery backup smoke alarm that features dual photoelectric and ionization smoke sensing technologies. This alarm features two latching features and two silence features. Alarm Latch: Easily identifies initiating alarm even after alarm condition has subsided. Low Battery Latch: Identifies which unit is in low battery condition by blinking the green power light. Low Battery Silence: Temporarily silence the low battery chirp for up to eight hours. Alarm Silence: Silence alarm for several minutes. Other features include an85dB horn, single button test/silence, an easy access battery drawer and dust cover. OptiPath 360 Technology: Exclusive patented technology provides 360 degrees of direct access to the smoke sensor. Two locking features are provided to prevent battery theft and/or theft of the unit. Connection to AC power is made with a Quick Connect wiring harness. Installation is quick, easy and cost effective.