The myth of battery back-up

Since I was knee-high to a grasshopper I've had digital alarm clocks, all touting "battery back-up."

Until a week ago I assumed that meant that, in the event of a power outage, the 9V battery I'd installed in a little compartment in back would take over the timekeeping and alarm functions, so that I'd be protected from a failed wake-up call.

Turns out that's true — but with one big qualification.

If your power goes out but comes back on before the time you've set your alarm for, you'll never know anything happened by what the clock says/does.

Because the moment the electricity comes back on, the clock will assume the correct time, with the alarm setting you left.

But — the big but — if the power's still off when your alarm is supposed to go off, nothing will happen.

What is the sound of silence?

'Cause that's what you'll hear.

My crack research team last week, out back in the skunk works, performed a series of experiments that revealed the facts above.

So — my advice would be to use a strictly battery-powered alarm clock the morning of your bar exam or whatever it is that absolutely, positively cannot be slept through.