Hotkeys can be used to start and stop talking while the Voice Chat connection window is minimized or not active:
If multiple Voice Chat windows are active, hotkeys only affects the window that has the Hotkey Focus. To enable or disable hotkey focus for a window, click on the toolbar button or select the menu item: 'Tools', 'Enable/Disable Hotkeys' Only one window can have the hotkey focus at a time, and enabling the hotkey focus for a window will automatically disable it for any window previously having the hotkey focus.