I don't know about that brand, but wired in smoke detectors are not hard
to find. They all should also have battery backup as it is not all that
uncommon to loose power as part of the problem that causes the fire.
I know that Rittenhouse was a competitor of "Nutone" in the 1970's and
1980's. At the time, I worked for an electronic servicing company that
was factory authorized for Nutone service
(as a minor sideline of their business).
Rittenhouse made door bells, door chimes, radio/intercom systems and
hard wired burglar alarm systems. Perhaps those smoke detectors are
part of the security system in that house.
They are liable to be pretty old. As another poster said, they
probably should be replaced for reliability.
I don't think Rittenhouse is still in business, at least not in
business making those products....
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