This is an odd one. Almost every night for the past six weeks to two months, I've been woken up by a burglar alarm going off at about 3 am. It only goes off for about 30 seconds. It's the same length of time each time - and end abruptly. Sometimes I hear it during the day, but mostly at night. Because it is short, and in the middle of the night, I can't find out where it is coming from! Has anyone else heard it?