I am missing something obvious, I am sure. But, how does the Treo 600 go into "hands free" mode, so that sound (phone calls, etc) goes to the earpiece. I have a Jabra earplug that I connected to the headset jack on the bottom of the Treo, but no sound (phone calls) can be herad through it. How is this feature engaged - sound going to the earpiece?

Thank you.