Team Talk 5 for IOS - Where's the push to talk button?

Hi,

actually, I do my first steps with Team Talk 5. All in all it seems that this is a pretty accessible app. The only thing I miss is any announcement of the big gren push to talk button that appears everytime you enter an existing conference room on any public or private PTT server. Does anyone got an idea how to locate that definitivly visual button?
Regards
Martin