Doing some work on a mid-60’s bi-level and would like to install interconnected, hard wired smoke detectors. Since it is a bi-level, with finished areas, etc, one continuous connection of the alarms is not possible. I checked the install instructions at First Alert and it shows the alarm interconnector wired from alarm A to B to C, etc. My questions:

1) Does the interconnector wire HAVE to be connected from and to each alarm, as from A to B to C? Or
2) Can the alarms be wired in a star pattern (several of the alarms such as in the bedrooms, would initially be wired in series) as long as ALL of the interconnector wires are connected at some central point? Or
3) Does it depend on the manufacturer and their wiring requirements?

You can connect in the star pattern or on separate lines, they just will not all go off if one goes off. You will have paid a higher price for interconnected and then defeated that feature, might as well by stand alone units.

They can be series, star or any combination, interconnect wire must connect between all.
If all of one level is interconnected, and all lower level is interconnected, and no connection between the 2, you can purchase 2 wireless interconnected smokes, they still use AC power, 1 on each level, that way if smoke is detected upstairs, you will be notified by the downstairs smokes.