Smoke and CO alarms are, for reasons I cannot explain, unnecessarily complex. I was looking for a simple solution that meets code in my area and provides fire and CO safety for my family. I bought 5 of the CO/Smoke alarms and 5 of the smoke alarms for my house, taking a risk on jumping from Google Nest alarms (no longer in production) and avoiding First Alert alarms (which had false alarms that plagued my family for years before overhauling everything to Google Nest). I installed all of these alarms, the connectors were easy to tie in, they worked immediately interconnected (all ring when one rings), all powered and show power with a green light confirming tied in, and do the job without any false alarms so far. Will revise if anything changes, but so far highly recommended