There has been lots of discussion about the internal mic not working when using the Thunderbolts headphone jack. At one point HTC stated that the internal mic turns off when the headphone jack is used and that no setting would change this. Well, I read a post on this forum a while back that changing the TTY mode would turn the mic on when a headphone jack is plugged in. Here's the change. Go to: Settings -> Call -> TTY Mode and change it to TTY VCO Today, I suggested to member Bonerdroid to try this as he had his phone plugged into his stereo and wanted to listen to the call through his stereo but talk through the bolts internal mic. He changed this setting and confirmed it worked. I know many people have complained about this issue so I thought I would post the solution under the "Tips" prefix. Thanks for the confirmation Bonerdroid and thanks to the OP who first posted this solution on this site. I would go back and find his user name but do not recall what thread he posted it in.