The 9120 Series smoke alarms have been designed to install faster, perform better and be even smarter than before. These improvements help reduce nuisance alarms and save you time and money. 10-Years Limited Warranty. 9V Battery Backup. Dust Cover. Easy Installation/Maintenance - Preferred features include alarge opening in the mounting bracket for easy access towiring.. Latching alarm indicator - remembers which unit initiated analarm. Perfect Mount - allows for easy alignment of alarm. Single button test/silence. Smart Technology - helps reduce the number of nuisancealarms Replaces 3535020