– How does a hard-wired smoke alarm know when it’s backup battery is low, and starts to chirp? 784 viewsJanuary 3, 2024 Question90.96K April 16, 2020 0 Comments – How does a hard-wired smoke alarm know when it’s backup battery is low, and starts to chirp? In: Technology 1 Answer ActiveNewestOldest Anonymous Posted April 16, 2020 0 Comments It has a little circuit that measures battery voltage. When the voltage drops too low it sounds the warning. Register or Login
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