The smoke detectors in my house are hooked up to the main power, but they still take a battery and beep when the battery is dead. I thought the battery was backup, but they die after about 2 years, so it can’t be backup, it must be used for something.
The smoke detectors in my house are hooked up to the main power, but they still take a battery and beep when the battery is dead. I thought the battery was backup, but they die after about 2 years, so it can’t be backup, it must be used for something.