JSW wrote:
Hi
I want to be able to connect smoke alarms to my existing house alarm. At my
local alarm shop they sell a small pcb which replaces the 9v PP3 battery and
allows the smoke alarm to be connected to the main alarm. This pcb probably
has a voltage regulator on it (12v to 9v) and some sort of current sensing
to trigger the main alarm when the smoke alarm sounds.
What I want is to be able to make this pcb myself as the shop wanted to much
for it and a want a few of them, does anybody know a circuit for such a
thing?


Yeah- it's called a relay. Your house alarm has inputs labeled N.O. and
N.C.- so you run a wire pair from one of those over to relay contacts
inside smoke alarm. Your difficulty arises on adapting the existing
smoke alarm circuitry to activate the relay. This will be over your
head- so go buy the finished product or drop the idea entirely.