I have found my Bionic randomly going into a total silent mode when I intended only going into sound off keeping vibrate active. When this occurs I find a new icon symbol not listed in the manual that came with the phone (a bell with red circle-slash in lower right) shown in as the second icon this image.
Other times when I use the same action (sliding the vibrate/sound slider to "vibrate") I see the vibrate icon, and when I receive a call the phone vibrates with no sound as intended.
This action (going to no sound / no vibrate) is not described anywhere I could find, nor is this icon described anywhere.
How do I prevent this condition from occuring?
Is there a new cheat sheet of icons (symbols) anywhere with explanation?