wired fire alarms

[SparkyTris]

the aico system is interesting indeed, a lot of function for the money. I had never seen them before.
The mic idea is a very good one. was it at all tuned for the piezo bleeper or just a wideband noise amp?

 

[JohnW2]

The mic idea is a very good one. was it at all tuned for the piezo bleeper or just a wideband noise amp?

Not "was" - it still "is" (and is alive and well!)!

No, not tuned - triggered purely on the basis of magnitude of the sound and it's duration ('a few seconds' required, if I recall correctly). If I recall (I built this very many, probably nearly 30, years ago!) the sensitivity of the system was adjusted to be something like 50-100 times greater than the minimum sensitivity required for it to be triggered by the alarm (persisting for 'a few seconds) and, despite experiments at the time and many subsequent years of in-service experience, I have yet to see it being triggered by any sound other than the arm sounder (and that includes periods in the past when there were teenagers with powerful audio equipment in the house .

The microphone is, of course, right next to one of the alarms, and I certainly wouldn't want my ear to be in that position when it 'went off'!

Kind Regards, John