When a particular group or area of a floor is selected, the line indicators change to show whether lines are currently open or busy. In this case, all three available lines for that group/area are busy, so the user clicks on the "Hold & Forward" button which will automatically route the call to a waiting queue, to be connected to the first open line when available. Presumably the operator is talking to the caller during this sequence, over a headset.

After routing the call, the display changes back to the floor number buttons.