Problem In Daisy-Chaining 3 New Kidde Smoke Alarms; Help Please

["Robert11" <rgsrose@xxxxxxxxx>]

Hello:

Boy, I have just finished spending several hours trying to figure out what
is wrong,
and am still stumped.
Would really be most appreciative for any thoughts on the following:

My son moved into a 30 year old house a few weeks back.
The house has 3 AC wired-in Rittenhouser smoke alarms.
No real way of knowing, but it wouldn't surprise me if they were originally
put in when the house was built, some 30 years back.  But they are possibly
newer ?

The three units apparently are wired to communicate with each other; I guess
that if one goes off, they all are supposed to go off.  They have a third,
Red, wire daisy chaining from one to another.

Didn't really think they did this daisy-chaining concept to fairly recently,
so was a bit surprised to see it.

I just put in 3 new Kidde Model PI 2000 (dual, photoelectric/ionization)
alarms.
Also AC wired in.  The "seem" to work fine.

But, if I hook up the red wires to daisy chain them together, they all keep
going off, sequentially.

Disconnecting the red wires, reverts them back to apparently normal
operation.

The house is a bit far from me, and won't be down there again for a week or
two.
I mention this, because I "now" think that it might have been a good idea to
put a meter on the red wire and check if there is any voltage on it ?

My undertstanding with the Kidde units, although I am not really sure, is
that there should normally not be any voltage on the red wires (relative to
ground) unless one of the units is tripped.
Should have checked.

Guess I assumed that the daisy chaining "concept" would be the same for the
old units as it is for the new ones ?

Is it possible that these old Rittenhouser units have the red, daisy link,
wire always hooked up to some voltage, or...?

Am I possibly missing anything when I wired them in ?

Any thoughts on what might bwe the problem, and how to correct it would be
most appreciated.

Thanks,
Bob