There are three versions or the RF series.
Battery only
Hardwired With battery back up
Hardwired with battery backup and interconnect wire to be used with other regular non-RF three wire Kiddie smokes
To work you can only have one, three wire RF unit installed, after that they can be any combination of non-RF three-wire or hardwired RF or battery RF
But if you plan to use a combo of regular non-RF three wire and RF three wire, you can only use one RF three wire or they will cause false alarms.
They have a series of dip switch's on the back that must be changed to all the same combination. this is similar to remote fan controls.
As a note, don't leave them at the factory setting, or a neighbor's smoke might set them off when his goes off.
