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> I even briefly entertained the thought of a microphone
> and audio decoder circuit to "hear" the bell but it would be
> easy to confuse and might false trigger from many sources.

Are you sure ? If it's the sort of chime I'm thinking of they are
pretty loud close up, and quite a pure tone. An LM567 at the
receiver, and a minimum-length threshold would eliminate
false alarms. eg the LM567 triggers a one-shot. At the end of
the one-shot period the LM567 should still be detecting the
tone if it's the chime. It's unlikely another event would be as
long as the chime

I made a remote door bell for my friend who has a long thin
factory. They make spaghetti. JK.

The front 1/3 is retail, the other 2/3 is the work area and often
people are way down the back, a good 50m away from the
front door. I tapped into the light beam detector and used a
a little Dorji 433MHz tx/rx pair (with help from a couple of
12F PICs and a small amp) to beep a speaker on the back wall

Joe


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