I have a UPS at home. It has started giving me three short sharp beeps. It isn't showing any error conditions on the LCD, and three beeps isn't mentioned in the manual at all...
Tell me, mysterious box with a battery, why are you shouting S at me in morse code?
Oh, right. After laying on the floor to try and catch the LCD on the UPS when it beeped, I noticed the noise coming from a slightly different location - turns out it's the low battery alarm for my pager.
Why yes, I am a very modern geek 😂