Hardwired smokes

House is approx. 1997, has hard wired smokes, however when tested, they do not all sound if 1 is tested.

My understanding is they are all hard wired so they will sound togather throughout the house. Is this correct?

They did all sound individually, one was not installed (removed) would this keep the others from sounding in sync.?

Thanks,

Hard wiring them does not make them all sound at once. Interconnecting them does. If they are wired with 3 conductors and interconnected, they will all sound at once. If they are only wired with 2 conductors, they cannot be interconnected.

Given the age of the house they certainly should be interconnected.

I agree.
Sounds to me like they were wired with “2-wire” and not interconnected.
Why? Who knows???