Subsequent investigation determined one of the models to be non-functioning and apparently the cause of the problem. I don't quite understand why all of the models are inter-wired to each other resulting in all of them shrieking at the same time, but, hey, I am not that smart. I got to the manufacturer's website and noted that they have a 5 year warranty and to return for a complete replacement. Out in the mail it goes today. I attached a note asking if they could change the warning tune to Brahm's Lullaby.
It makes it easier to sleep.