How could smoke alarm beep without battery and disconnected?

  • Thread starter sp3sp2sp
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  • #1
sp3sp2sp
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It beeped when I had removed battery and disconnected it from ceiling. The power has to come fromm somewhere, so how could it beep?
 

Answers and Replies

  • #2
russ_watters
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It beeped when I had removed battery and disconnected it from ceiling. The power has to come fromm somewhere, so how could it beep?
Two options:
1. It's storing some energy in a capacitor.
2. It's connected to the house's electricity.

You should look up the instruction manual for it.
 
  • #3
FactChecker
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A smoke alarm that is usually powered from an external source will have a capacitor for back-up power. That allows it to "chirp" for a while when the normal power fails. That is important for keeping the alarms working.
 

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