In ,
Don Y typed:
On 3/13/2016 4:19 PM, TomR wrote:
won't do that. Also, the purpose of the 14/3 is to provide a black
(hot) wire, a white (neutral) wire, and a third (red) wire for the
signal between the units.

And I'm saying that using the third wire in a 14/3 cable for
"signalling" may not comply with code! Any more than my using it as
an audio output from an amplifier (neutral referenced) would...

I already know that the way that 110 volt interconnected smoke detectors are
wired is with 14/3 (or it could be 12/3 as an alternative), and the third
(red) wire is the "signal" wire that allows them all to go off when one goes
off. That is the code compliant way of wiring them.

What I don't know for sure are my original questions about the wiring
diagram, the wireless possible alternative, etc.