It's letting you know that there's no mains power supply to the panel, and it's running on battery backup,which will need replacing anyway.
It most likely hasn't a fused spur fitted as it has a 2amp fuse fitted to a ceramic plug top holder INSIDE the control panel.
You need to make absolute certain that there is no mains power supply to the panel before you go inside to check this fuse.
Chances are they won't be a spare fuse in there anyway.
be safe and get someone in :)
e manno
December 2012