Hardwired Ionization Smoke Alarm, With 9V Battery Back Up, The First Alert SMI100-AC Hardwire Interconnect Smoke Alarm with Battery Backup meets new industry standards utilizing First Alert's Precision Detection advance sensing technology. This hardwire smoke alarm is easy to install and replace existing alarms with no need to rewire. Plus interconnect compatible alarms to create a whole home alarm system to help provide an early warning.