Of course I have no usual alarm clock, mine is manufactured by "Oregon Scientific", gets the time signals from a nuclear bunker near Rugby and emits a faint "Silence of the Lambs" whistle as it glows to tell you the time in the dark.
And tonight it was showing "Ba" on the left hand display. I thought that it had got it's little silicon brain skewed, and had defaulted to a day of the week setting for a language where Ba means Saturday. I reset the machine several times and laboriously re-entered the alarm time and stepped through the language options. And each time, the accursed Ba came back. And the display was a bit faint. Stupid clock.
After a while it dawned on me that Ba is short for battery. Oh yes. A couple more AAAs (I always have a stock of batteries - we have been known to run out of toilet paper but never batteries) and we are back in business.