Several times I have set the volume to 0 and put the phone to vibrate when entering a meeting.  Then when coming out of a meeting, I hit the phone button and the phone makes the call but I get no volume!  I don’t think anyone would ever want to make a phone call where they have no volume.  When I hit the call button it shouldn’t it turn the volume up for me.  Interesting enough, in this scenario if I plug in the headset the volume is OK?