This First Alert® is a 120 V AC powered hardwired combination photoelectric smoke and carbon monoxide alarm with battery backup and rapid connect feature for an easy installation. It features photoelectric smoke detection and electromechanical carbon monoxide detection as well as 85 dB siren at 10'. It gives you an end-of-life signal telling when the unit needs to be replaced and 2 silence functions, to silence low battery indicator for 8 hours or to temporarily silence a false alarm. A maximum of 18 detectors can be connected12 of which can be smoke alarms. The technology OptiPath 360 is a patented design providing unobstructed 360° access to the smoke detector. The tamper-resistant locking pin makes it ideal for rental units. This product is backed by a 10-year limited warranty.