I am unable to get a low battery audible alert unless the squelch is broken. If the vocal is not too loud I can hear the alert tone in the background (alert time repeat currently set to 30 sec.) I've played with the EZ-Scan advanced settings to no effect. There is no card corruption when the unit shuts off without my knowing, and always powers up again normally after new batteries. I suspect the answer is right in front of me but I don't have the right glasses to see it. This is an upgraded 668 unit by the way. Alert settings are set to audio and max volume. Any ideas on what I've got wrong?