You can use the group buttons to control the functions of a camera group.
A group function allows to switch the lights, to open one or more doors or
to make an announcement over several speakers for one or more cameras of
the group (regardless of the camera currently shown). In addition, you can
right-click on the group buttons and open the context menu to control
cameras that are not part of the current group. Before you can this, the
cameras have to be set up accordingly, i.e., the cameras need to be
connected to door openers/light switches and have to be configured
properly.