thebeave
Veteran Member
That's not uncertain. We don't know if the battery was there or not, but certainly, if the clock had been plugged in the teacher should have noticed. To me it seems rather more likely that the clock was on a battery at that time. As for setting an alarm, forgetting that the alarm is on is a simple mistake, and it going off sometime during a class is not that unlikely.We know he plugged it in and set the alarm to go off in the middle of class, as the clock had no other power source.
Most battery backups that I've come across are there just to maintain the proper time and internal programming (if any) during the power outage. You generally do not have a fully functional device. Once the power is restored, the device will come back on with the proper time and programmed settings. For example, sprinkler system controllers have battery backups, but they will not operate the individual valves during the loss of AC power. They will maintain the proper time and sprinkler on/off programming for you so you don't have to reenter it all in again. Small little batteries often don't have the ability to power large power drains like valves or alarms.
My own alarm clock has a 9V battery backup. Out of curiousity, this morning I put in a brand new 9V battery, and set the alarm to go off in two minutes. I then unplugged it from the wall. The LED display went dead immediately, and the alarm did not go off at the programmed time. When I plugged it back in a few minutes later, the display came on to the proper time and the alarm was beeping. Although I can't be sure, I suspect this is the way Ahmed's and most alarm clock battery backups work. Especially Ahmed's, since his LED display was so huge. I don't see a little 9V battery powering that big thing for very long. This makes sense, as the main purpose of the backup is to ensure that you don't miss your alarm in the morning, due to a momentary AC outage during the night. If the battery was powering up a big display during a power outage in the night, that would deplete the battery pretty fast...maybe that night. And besides, who needs to look at the display while you're sleeping? Of course, if the power outage lasts through the morning, you're screwed, in which case you may want to bring out granny's old wind up clock instead.
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