Checking for DC on the signal line, I get functionally nothing. 20ma DC at most, and even that's something I'm picking up out of noise floor shift rather than direct measurement.

My _thought_ was that if the signal line was somehow floating in whole number volts (for whatever reason) than maybe somehow the right RF noise could kick it over.

The problem with _that_ is that I can now _also_ confirm that non-detecting units go off _exactly as long_ as a detecting device keeps saying it's detecting by putting voltage on the signal line. If that voltage goes away, so do the satellite alarms - and immediately.

And that's not what happens. We have to manually intervene and shut the alarms off ourselves.

(2/n)

#electronics #SmokeDetectors #why

The reason I paid meaningfully more than baseline for this particular set is that they report exactly which detector went off and why. That way, if it were the signal line somehow triggering the alarms, none of them would claim to be the originating unit; they'd all report it came from the signal backbone.

But they don't. There's always a unit claiming to be the active detector and it's always smoke (and there is *never* actually smoke), and none of them shut up until we shut off that unit, which sometimes seems to require removing it from power.

So today's afternoon check was basically just another way of confirming what we already knew, and I guess I've done that now, but...

(3/n)

#electronics #SmokeDetectors #why