Originally Posted by jeremyckitching
Did you try the Mute button, as JSanders suggested? On my 8700g I held it down for about 5 seconds and it switched to the vibrate profile. Holding it down again switches back to Normal.
If you hold down the Mute button, it locks the keyboard and the profile does not change, so everything rings just as I left it. The OP wanted to automatically change the profile to Vibrate - for example if you walk into a meeting or a movie theater, you would want all sounds shut off very quickly.