An on-screen indication that you are speaking.
Summary[]
As in many other online multiplayer games, Team Fortress 2 allows for teammates to speak to each other over a microphone. This is known as Team Chat. While helpful, it does have it's limitations. You can only speak to your teammates, for example. [Patched]( Another limitation is that if you are dead and waiting to respawn, or return to the game, you can only speak to members of your team that are also dead, and no one else ). This was done most likely to prevent Ghosting; basically, giving your alive teammates tips/orders about their environment that they couldn't normally see, for example, warning them about a Spy who is about to backstab them.