Homes built in the last 15 years may have an interconnected smoke alarm system. If all alarms sound when you test, you have an interconnected system. If your home fits this description, then you want to purchase one Kidde Wireless AC Powered Smoke Alarm to replace only one current smoke alarm. This Wireless AC alarm now acts as a bridge between the current system and other Kidde Wireless products. Purchase Kidde Wireless Battery Powered Smoke Alarms to be installed in additional rooms.